The reaction of nucleophiles with some isothiazolium and 1,2-dithiolium salts

摘要

1972 2305The Reaction of Nucleophiles with Some lsothiazolium and I ,2=DithioliurnSaltsBy P. Sykes and H. Ullah, University Chemical Laboratory, Lensfield Road, Cambridge CB2 1 EW2-Alkylisothiazolium salts were prepared by quaternisation of the corresponding isothiazoles ; they were found tobe relatively stable to oxidation but when unsubstituted, formed insoluble complexes with heavy metal salts. Theisothiazolium salts were decomposed by aqueous alkali, but were found to yield a series of products includingboth cyclic and acyclic compounds on treatment with a range of nitrogen and sulphur nucleophiles ; generallyanalogous products were obtained from reactions of the same nucleophiles with 1.2-dithiolium salts. Both typesof salt were unaffected by the phosphorus nucleophiles investigated.FOLLOWING studies of the reactions of nucleophiles with3-alkylthiazolium 1p and 3-alkyl-2-thiazolinium saltswe have performed a similar investigation of some2-alkylisothiazolium (1)-(8) and 1,Zdithiolium (9)-(14) salts.R' A R;S-N R +X -R I f i R 2s-s +X 'R ' R 2 R 3 R ' R 2( 1 ) H H PhCHz ( 9 1 H H( 2 1 H H M e ( l 0 ) P h H( 3 ) !-i H PhCO.CH2 ( 1 1 ) Ph P h( 4 ) Ph H PhCH2.( 1 2 ) Ph SMe( 5 ) Ph H Me ( 1 3 ) Ph SqCH2Ph( 6 ) Ph H PhCO.CH2 ( 1 4 ) Ph S.CH2*COPh( 7 ) P h H Ph( 8 ) P h P h M eThe 2-alkyl salts (1; X = Br or I), (2; X = S03F orjb-MeC,H,*SO,), and (3; X = Br) were obtained byquaternisation of isothiazole (prepared, with somemodification, by the method of Wille *) with benzylbromide and iodide, methyl fluorosulphonate andtosylate, and phenacyl bromide, respectively.5-Phenyl-isothiazole similarly yielded the salts (4; X = Br),(5; X = S03F), and (6; X = Br), the first and lastonly with difficulty and in low yield, however. 3,5-Diphenylisothiazole resisted quaternisation by benzyland phenacyl halides but yielded the salt (8; X = SO,F)on treatment with methyl fluorosulphonate. Saltscontaining the fluorosulphonate anion tended to behighlv hygroscopic and somewhat unstable, readilylosing sulphur dioxide. Compounds containing thisand some other anions were therefore subjected to ion-exchange to yield a variety of anion salts of a commoncation; of these, perchlorates were the most stablebut had the disadvantage, for our purposes, of very lowsolubility even in hydroxylic solvents.The fluoro-sulphonates also had the property of adhering tenaciouslyJ . E. Downes and P. Sykes, Chem. and Ind., 1959, 161.G. M. Clarke and P. Sykes, (a) Chem. Comm., 1965, 370;( b ) J . Chem. SOG. ( C ) , 1967, 1269; (c) ibid., p. 1411.A . D. ClarkandP. Sykes, J . Chem. SOG. (C), 1971, 103.( a ) F. Wille, Angew. Chem. Internat. Edn., 1962, 1, 335;( b ) K. Raap, Canad. J . Chenz., 1966, 44, 1324; (G) R. Slack,personal communication.M. G. Ahmad, R. W. Alder, G. H. James, RI. L. Sinnott,and M. C. Whiting, Chem. Comm., 1968, 1533.to hydroxylic solvents. The 1,2-dithiolium salts (10;X = Clog) and (11; X = Clog) were obtained by themethods of Klingsberg8 and of Behringer and Grimm,9respectively, but salts with other anions were alsoprepared, The 3-alkylthio-l,2-dithiolium salts (12 ;X = I), (13; X = Br), and (14; X = Br) were obtainedby S-alkylation of 5-phenyl-l,2-dithiole-3-thione (39) .loThe 2-alkylisothiazolium salts were stable to oxidisingagents such as hydrogen peroxide and sodium periodate,but (1; X = Br) yielded benzoic acid as the onlyproduct with acid permanganate.The salt (1 ; X = Br)formed insoluble, crystalline complexes with mercury (11)chloride and bromide, lead nitrate, and antimony tri-chloride, but the salts (5; X = S03F) and (8; X =S03F) did not. U.V., i.r., and n.m.r. spectra indicatedthat the isothiazolium cation was essentially unchangedin these complexes.2-Alkylisothiazolium salts lacking 3- and 5-substituentse.g.(1; X = Br) were decomposed rapidly at roomtemperature by aqueous alkali; those with such sub-stituents e.g. ( 5 ; X = S03F) and (8; X = SO,F) wereslightly more resistant, but decomposed rapidly onwarming. Intractable tars, apparently polymeric incharacter, were obtained and in no case were any fissionproducts identified. A case is known l1 (4-methoxy-carbonyl-2,3-dimethylisothiazolium iodide) where afission product (methyl 2-f orm yl-3-met h ylaminobut -2-enoate) was isolated, but it is significant that the hetero-cyclic nucleus here carried a powerful electron-with-drawing substituent .Action of Nitrogen Xucleophiles on Isothiaxolium Salts.-Following the observation of Landsberg and Olofson l2that a singly substituted 2-alkylisothiazolium salt re-acted with ethanolic ammonia, hydrazine hydrate, andphenylhydrazine to yield the corresponding substitutedisothiazole, pyrazole, and l-phenylpyrazole, respectively,the generality of the reactions was demonstrated bysimilar conversions of unsubstituted and of 3,5-di-phenyl-2-alkylisothiazolium salts e g .(1) and (S) .R. A. Olofson, J. M. Landsberg, R. 0. Berry, D. Leaver,W. -4. H. Robertson, and D. 31. McKinnon, Tetrahedron, 1966,22, 2119.D. 31. McKinnon and E. A. Robak, Canad. J . Chem., 1968,46, 1855.E. Klingsberg, J . Amer. Chem. SOL, 1961, 83, 2934.H. Behringer and A. Grimm, Annalen, 1965, 682, 188.lo B. Bottcher and A. Liittringhaus, Annulen, 1947, 557,l1 G.P. Volpp, personal communication.l2 J. M. Landsberg and R. A. Olofson, Tetvahedron, 1966, 22,89.2135J.C.S. Perkin Ibenzylamine yielded the ring-opened benzylamino-thiones (25) and (26)l; the former was not obtainedpure, but both were converted on oxidation withiodine into the corresponding 2-benzylisothiazoliumsalts (4) and (28), respectively. The reaction of5-substituted isothiazolium salts e.g. (5) with anilinewas slower than with benzylamine, but yielded thecorresponding anilino-thione (27) previously obtainedfrom the reaction of aniline with a 3-phenyl-1,2-di-thiolium salt l5 (10; X = ClO,); this, in turn, wasconverted on oxidation with iodine into the correspond-ing 2-phenylisothiazolium salt (7). The 3,5-disub-stituted isothiazolium salt (8) was, however, recoveredunchanged after being heated with aniline in ethanolunder reflux for 24 h.Hydroxylamine reacted with 2-methyl-3,5-diphenyl-isothiazolium fluorosulphonate ( 8 ; X = SO,F) to yieldR ’ h R 2S-NN-N( 1 ) R1=R2=H,R3=PhCH2 H( 1 7 ) R1 =R2=H( 1 8 ) R 1 =R2=PhA( 8 ) R’ =R2=Ph.R3=MeRIY /)RZN-NPh( 1 9 ) R ’ = R 2 = H( 2 0 ) R ’ =R2=Phthe isoxazole (21) and the isothiazole N-oxide (24a);2-met hyl-5-phen ylisothiazolium fluorosulphonat e (5 ;X = SO,F) similarly yielded a mixture (4 : 1) of 3- and5-phenylisoxazoles (22) and (23), respectively plus theisothiazole N-oxide (24b). Unsubstituted isothiazoliumP h 6 R2 N H2’0H * R l f i R 2 + P h 6 R 2S-N M e O-N S-N++ SOsF‘ ( 2 1 ) R’=R2=Ph ( 2 4 ) 0 -( 8 ) R2=Ph ( 2 2 ) R’=Ph, R2=H a; R2=Ph( 5 ) R ~ = H (23) R’-H,RZ=Ph b; RZ=Hsalts e.g.(1; X = Br) yielded neither isoxazole norisothiazole N-oxide with hydroxylamine, probablyowing to the instability of both potential products underthe basic conditions of the reaction. It is significantthat the yield of isoxazole from the substituted iso-thiazolium salts fell markedly as the basicity of thesolution, or the time of heating beyond an optimum, wasincreased. The establishment of the structure of thenovel N-oxides depended (apart from elemental analysis)on the mass spectrum, which included an M+ - 16 ioncharacteristic of N-oxides,13 on a red shift in the U.V.spectrum (ether solution) relative to that of the parentheterocycle and a blue shift with methanol as solventcompared with ether,14a on a strong i.r.absorption at1280 cm-l shifted to 1260 cm-l in protic solvents 14b and,finally, on their conversion into the corresponding iso-thiazoles on treatment with phosphorus trichloride.Attempts to oxidise 5-phenylisothiazole to the N-oxide(24b) with peroxy-acids were unsuccessful.Reactions of 5-mono- and 3,5-di-substituted iso-thiazolium salts e.g. (5) or (7) and (8), respectively withl3 T. A. Bryce and J. R. Maxwell, Chem. Comm., 1965, 206.l4 E. Ochiai, ‘ Aromatic Amine Oxides,’ Elsevier, Amsterdam,1967, (a) p. 126; (b) p. 114.x -+ ( 5 1 R 2 =H.R3 =Me ( 2 5 ) R =PhCH2,R2=H( 7 ) R2=H,R3=Ph ( 2 6 ) R =PhCH2,R2=Ph( 8 1 R2=Ph,R3=Me ( 2 7 1 R =Fh,R2=H I I 2Isothiazolium salts carrying no 3-, 4-, or 5-substituent e g .(1) J reacted rapidly with benzylamine and aniline,yielding not the expected benzylamino- or anilino-thiones but the dianil salts (29) and (30), respectively.Ph CH2.N HZo r PhNH2 RN H2N.CH2Ph Br’ S-Y-CH 2 P hB r - (29) R = P h C H t(1 1 (30) R =PhThe retention of a benzyl group in structure (30) demon-strates that the dianil salts cannot be produced byattack of a second molecule of amine on a first formedamino-thione (cf. before), and suggests that the mode ofinitial attack by amine must depend on whether theisothiazolium salt does, or does not, carry a 5-substituent.Both substituted and unsubstituted isothiazoliumsalts were decomposed by secondary amines such asdiethylamine, piperidine, and pyrrolidine, and also bythe tertiary amine triethylamine, but none of the de-composition products (other than elemental sulphur)was isolated or characterised.Pyridine, acridine, andN-methylaniline were without effect on the isothiazoliumsalts.15 D. Leaver, D. M. McKinnon, and W. A. H. Robertson,J . Chem. SOC., 1965, 321972 2307An NS-bidentate nucleophile, 2-aminoethanethiol, wasemployed to investigate whether attack on the iso-thiazolium nucleus occurred preferentially through itsnitrogen or its sulphur atom. The salts (5) and (8)were attacked exclusively through nitrogen to yield themercaptoethylamino-thiones (31) and (32), and thesewere converted by iodine into the corresponding iso-thiazolium salts (33) and (34), respectively, in which thethiol group had also been oxidised to a disulphide system.+SO3F’ ( 3 1 ) R2=H( 5 I R ~ = H ( 3 2 ) R2=Ph( 8 ) R2=Ph I I I 2d)r 1( 3 3 ) R2=H( 3 4 ) R2=PhIt was necessary to carry out the reactions undernitrogen because of the instability in air of both thenucleophile and the mercapt oethylamino-t hiones (3 1)and (32). Ring opening also occurred with 2-benzyliso-thiazolium bromide (1; X = Br), but none of theproducts was isolated or characterised.Actioiz of Sulphur Nucleophiles on Isothiazoliuna Salts.-The relative resistance of isothiazolium salts toattack by a thiol group in the NS-bidentate nucleophilewas further illustrated by their resistance to attack byethanethiol, 2-aminoethanethiol hydrochloride, andmercaptoacetic, thioacetic, and thiobenzoic acids. Withthe more nucleophilic benzenethiol, however, ring fissiontook place; the somewhat unexpected products werethe methylamino-thiones (35) and (36), in which the2-alkyl group of the starting material had been retainedthese methylamino-thiones have been obtained previ-ously by the action of methylamine on the corresponding1,2-dithiolium salts (10) and (1 l).The methylamino-thiones (35) and (36) were further characterised byPhS” PhCl/ijRzS HNMeP h f i R 2 1 2S-N MeClOL +(5) R ~ = H( 8 ) R2=Ph( 3 5 1 R2=H( 3 6 ) R2=Phreconversion, on oxidation by iodine, into the original2-methylisothiazolium cations (5) and (8). The factsl6 H. Newman and R.B. Angier, Chem. Comm., 1967, 353.l7 D. Leaver and W. A. H. Robertson, Proc. Chem. Soc., 1960,OCOthat no benzenethiolate residue was incorporated andthat diphenyl disulphide was formed suggest that thereaction may be a reduction rather than a simplenucleophilic attack.More surprising, in the light of the stability of iso-thiazolium cations towards sulphur nucleophiles, is thathydrogen sulphide reacted extremely readily in aqueoussolution with isothiazolium salts lacking a 3-substituent e g . (l), (5), and (6) to yield the bis-1,2-dithiolyl sul-phides (37) and (38), the original 2-substituent beinglost as the corresponding amine; the unsubstitutedsulphide (37) was extremely unstable.The bis-1,2-dithiolyl sulphides (37) and (38) one witha 4-substituent had previously been obtained from theaction of hydrogen sulphide on the corresponding4-substituted 1,2-dithiolium salt 16 are readily decom-posed by acid to yield the corresponding dithiolium salts(9) and (IO), respectively. The 3,5-diphenylisothia-zolium salt (8; X = S0,F) also reacts with hydrogensulphide but the resultant gummy product was notcharacterised and, though it was converted on boilingwith hydrochloric acid into the 3,5-diphenyl-1,2-dithiolium salt (11; X = Cl), there is some doubt as to.whether it is a simple sulphide.It may be relevantx - +( 1 ) R =PhCHZ,R’=H( 5 1 R =Me,R1=Ph( 3 7 ) R l = H( 3 8 ) R’=Phi H X( 6 1 R =PhCOCH2,R1=PhR 1 6 s-sx - + ( 9 ) R J = H( 1 0 ) R’=Phthat the 3,5-diphenyl-l,2-dithiolium cation (1 1) is un-affected by hydrogen sulphide (see later).Action of Nitrogen N.ucleophdes on 1,2-DithioliumSaZts.-l,2-Dithiolium salts are known to react withammonia 6915917 to yield the corresponding isothiazoles,and with methylamine and arylamines 7918~19 to yieldthe corresponding 3-methyl- (or -aryl-)aminopropene-l-thiones e.g.(36) and (27). Benzylamine was found tobehave similarly, and 2-aminoethanethiol also gave theexpected amino-thione (32) with the 3,5-diphenyl-lJ2-dithiolium salt (11; X = C10,). With the 3-phenyl-1,2-dithiolium salt (10; X = C10,) the latter nucleophileyielded not only the expected amino-thione (31) but also5-phenyl-l,2-dithiole-3-thione (39).J. Bigenbat and H. Quiniou, Bull.SOC. chim. France, 1966,1180. ~ ~ - .19 J. Bigenbat, H. Quiniou, and N. Lozac’h, Bull. Soc. chi~t2.France, 1969, 1272308 J.C.S. Perkin IAction of Sulphw Nucleophiles on 1 ,2-Dithioliuum Salts.-Ethanethiol reacted with 3-mOnO- and 3,5-disub-stituted 1,2-dithiolium salts e g . (10) and (ll) to yields-s(39 1the simple 5-adducts (40) and (41), respectively, whichwere reconverted into the original 1 ,2-dithiolium saltson treatment with acid. Ethanethiol, surprisingly, didnot react with the 3-methylthio-1 ,2-dithiolium salt (12).With thiobenzoic, thioacetic, and mercaptoacetic acidsthe 3-phenyl-lJ2-dithiolium salt (10) also yielded adducts(42), (43), and (U), respectively, and these were con-verted by acid into the corresponding lJ2-dithiolium saltP h h R 2 B RSH P h ( 9 1 :H X s-s s-sx - +( 1 0 ) R ~ = H( 1 1 ) R 2 =Ph( 4 0 1 R2= H,R = E t( 4 1 1 R 2 = P h , R = E t( 4 2 1 R2=H,R =COPh( 4 3 ) R2=H,R =COMe( 4 4 ) R 2 = H , R = C H z * C O 2 H(10) and by aniline into the phenylamino-thione (27).The foregoing three nucleophiles were, in contrast toethanethiol, without effect on the 3,5-diphenyl-l,2-dithiolium salt (11).With the 3-methylthio-1 ,Z-di-thiolium salt (12) all three nucleophiles yielded the 3-thione (39), as did benzenethiolate anion and hydrogensulphide the latter with (14) as well as (12), the lasttwo in markedly higher yield. These reactions mayproceed through simple alkyl transfer as observed withpyridine,20 but no S-methylated nucleophiles weredetected and it thus seems likely that the high stabilityof the 3-thione (39) prompts its formation from a morecomplicated ring opening-reclosure sequence.This isborne out to some extent by the fact that both benzene-thiolate anion and 2-aminoethanethiol (see before) alsoconverted the 3-phenyl-lJ2-dithiolium salt (10) into the3-thione (39). The same nucleophile reacted with the3,5-diphenyl-1,2-dithiolium salt (11) but no thione (39)was detected, the product being an unidentified gum.Hydrogen sulphide was without effect on the disub-stituted salt (11) but converted the 3-phenyl salt (10)into the bis-1,2-dithiolyl sulphide (38) (cf. ref. 16).Both isothiazolium and 1 ,Zdithiolium salts wererecovered unchanged on attempted reaction with thepotential phosphorus nucleophiles , phosphine andphenylphosphine.Discztssion.-Our observations are generally com-patible with the occurrence of initial attack of nitrogennucleophiles on the 3-position of isothiazolium cations(45a) , followed by ring-opening (mechanism C of Lands-berg and Olofson 12) ; whether reclosure does or does nottake place then depends on the nature of R in thenucleophile RNH,.When R = H, attack of the addednitrogen atom’s lone pair on the sulphur atom in (46)with loss of R3NH2 (as R3NH- and H+) will yield iso-thiazoles (15) and (IS). When R = alkyl or aryl, thereis no proton to be lost and the products are thus theamino-thiones (25)-(27) formed by loss of R3NH fromc N H 2 RR1R32 R 1 f i R 2S-N R S-FJ R 3 +H(46)(46).When R = NH, or NHPh, however, attack bythe more nucleophilic of the added nitrogen atoms cantake place a t the carbon atom attached to R1(C,) in(46) to form a five-membered ring, followed by loss ofproton (though from a different nitrogen than withammonia; see before) to yield pyrazoles (17) and (IS)and l-phenylpyrazoles (19) and (20), respectively.When R = OH, isoxazoles (21) and (22) are obtained ina similar way, but, unexpectedly, isothiazole N-oxides(24a and b) are also formed through attack of thenitrogen lone pair on sulphur in (46), as with ammonia,followed this time by loss of proton from the adjacentoxygen atom.However, attack of hydroxylamine (or of phenyl-hydrazine 12) on an unsymmetrically (5-) substitutedisothiazolium cation (45; R2 = H) yields not only the5- but also the 3-substituted isoxazole k (23) as wellas (22) (the 1,3- as well as the lJ5-disubstituted pyrazolewith phenylhydrazine 12) , and this latter must be formedthrough initial nucleophilic attack on C-5 of the originalheterocycle.Such attack is not unreasonable on thebasis of the expected charge distribution in the quasi-aromatic cation (45) f-t (45b)l. Attack of the lonepair of the oxygen (R = OH) or nitrogen (R = NHPh)atom on CA in (47) will then yield the 3-substitutedheterocycle e.g. (23). Surprisingly, the 3-substitutedisoxazole is formed in higher yield than the 5-isomer(4 : l ) , suggesting that the product ratio is controlled bygreater difficulty of lone pair attack on Co in (46) thanon CA in (47), rather than by the relative ease of initialnucleophilic attack on C-3 in (45a) versus that on C-5 in(45b).It is interesting in this connection that thedianils (29) and (30), obtained from the action of benzyl-amine (R = CH2Ph) and aniline (R = Ph), respectively,on an isothiazolium cation (45 R1 = R2 = H) lackinga 3- or 5-substituent, must also arise through preferential2O Y . Mollier and N. Lozac’h, Bull. SOC. clzim. Frame, 1961,6141972 2309attack of the initial nucleophile at C-5, followed by lossof sulphur (which is indeed detectable) from (47). Withammonia (R = H), nucleophilic attack on C-5 in (45b)could not lead to an isothiazole and only one suchheterocycle, the 5-substituted one, is in fact obtained.12( 4 5 1 ( 4 5 b )R N H 2 17 HR f,< cB3TAR2 f------ R H N o R 2RN NR3 I R 1 C S - N R 3SH( 4 7 1With hydrazine (R = NH,), only one pyrazole is againobtained, as 3- and 5-substituted pyrazoles are in-distinguishable.The reactions of 1,2-dithiolium salts e g .(10) and (ll)with nitrogen nucleophiles clearly indicate a similarmechanism with initial attack at C-3 and C-5 bothpossible.6, 2-Aminoethanethiol did, however, yield5-phenyl- 1,2-dit hiole-3-thione (39) with compound (10)in addition to the expected aminothione (31); but thismay well arise as a secondary product from the actionof sulphur (from ring-opened and decomposed 1,2-dithiolium cation) on the 1,Z-dithiolium cation (10).Isothiazolium cations (45) were unaffected by most ofthe sulphur nucleophiles investigated, but the power-fully nucleophilic benzenethiol yielded the alkylamino-thiones (35) and (36).It is difficult to explain theirP h S HP h G R 2 ---+S-N M e- 7 * ..I .PhSH( 5 1 R ~ = H(6) R2=PhP h f i R 2S. NMeP h J ( 4 8 )I F ' h S HPhfiR2 + PhS*SPhS HNMe( 3 5 ) R2=H(36) R2=Phformation on the basis of initial nucleophilic attack a tC-3 or C-5, but simple in terms of initial attack onsulphur, followed by exchange of the resultant mixeddisulphide (48) with a second molecule of benzenethiol.Significantly, diphenyl disulphide is formed during thereaction. More surprising is that isothiazolium cationse.g. (1) and (5) yielded bis-1,2-dithiolyI sulphides (37)and (38) with hydrogen sulphide; the formation ofthese too is more readily explainable in terms of initialattack on sulphur.H2SJ H S:)( 1 ) R1=H( 5 1 R ' = P hR I W s m R 1 4 H 2 S R1$:HR3s-s s-s(37) R ~ = H( 3 8 ) R1 =PhThere is no evidence whether final formation of thesulphide occurs via the parent 1,2-dithiolium cationfrom (49) or directly from the amine adduct (49) asshown.Hydrogen sulphide reacted with a 3,5-diphenyl-isothiazolium cation (8) but no sulphide was formed; itmay be significant in this respect that the 3,5-diphenyl-1,2-dithiolium cation (1 1) is unaffected by hydrogensulphide.The 5-phenyl-1 ,Z-dithiolium cation (lo), unlike iso-thiazolium cations, yielded simple 3-adducts (40) and(42)-(U) with a range of sulphur nucleophiles and thesulphide (37) with hydrogen sulphide, the latter pre-sumably via nucleophilic attack of the first formed 3-adduct on a second l,dithiolium cation; l 6 onlyethanethiol yielded an adduct (41) with the 3,5-di-phenyl-l,2-dithiolium cation ( l l ) , no sulphide beingformed either.All the foregoing nucleophiles ex-cept ethanethiol converted 3-alkylt hio-5-phenyl- 1,2 -dithiolium cations e.g. (12) into the 1,2-dithiole-3-thione (39), but it seems unlikely that this occurs bysimple dealkylation (as happens with pyridine 2o andacridine) as no S-methylated nucleophiles were detected.Hydrogen sulphide could effect the conversion by attacka t C-3 with expulsion of methanethiolate anion (a goodleaving group) and a proton, but such a mechanism isclearly not open to the other sulphur nucleophiles, andit is perhaps significant that yields of 3-thione (39) areconsiderably lower with them than with hydrogensulphide.It is also significant that the thione (39) isproduced by the reaction of benzenethiolate anion withthe 1,2-dithiolium cation (10) with no S-alkyl sub-stituent in the 3-position albeit in smaller yield thanfrom (12) and also, in addition to the amino-thione (31),from attack of 8-aminoethanethiol on the same cation(see before). In the latter two cases a t least it seemslikely that the third sulphur atom in the 3-thione (39)comes from breakdown of the dithiolium cation addedsulphur increased the yield of thione (39), rather thanfrom the nucleophile itself, arising from a relativelycomplicated ring opening (perhaps by initial nucleo-philic attack on sulphur) and decomposition sequence 2310 J.C.S.Perkin Icertainly a complex mixture of products, in addition tothe thione (39), is formed.EXPERIMENTAL1.r. spectra were obtained with a Unicam SP 200 or aPerkin-Elmer 257 instrument; n.m.r. spectra were obtainedwith a Varian HA 100 or a Perkin-Elmer R10 (60 MHz)instrument, tetramethylsilane being used as internalstandard except for solutions in deuterium oxide, for which2-methylpropan-2-01 (7 8.78) was employed ; U.V. spectrawere obtained with a Unicam SP 800B or a Cary 14M-50instrument; mass spectra were obtained with an A.E.I.MS9 or MS902 instrument.T.1.c. was performed on silicagel GF 254 plates. Analytical g.1.c. was performed with anFM720 or Perkin-Elmer F11 instrument, and preparativeg.1.c. with an Aerograph Autoprep 700 instrument.Isothiazo1e.-The oxidation of prop-2-yn- 1-01 with chro-mium trioxide-sulphuric acid to yield prop-2-ynal wascarried out 4e at 35" rather than at 2-10' as recommendedby Sauer,,l resulting in a considerably higher yield. Thealdehyde content of the resultant aldehyde-water mixturewas rapidly determined with hydroxylamine, and the un-stable aldehyde was immediately treated with the calculatedquantity of aqueous sodium thiosulphate solution to yieldthe cis-propenal a d d ~ c t . , ~ , ~ The adduct was finallytreated with liquid ammonia to yield isothiazole; a crucialfeature was the rate of evaporation of the liquid ammonia,attempts to hasten i t being attended by a marked fall in theyield of product.2-Benzylisothiazolium Bromide (1 ; X = Br) .-Isothiazole(5.1 g, 0.06 mol) and benzyl bromide (10-3 g , 0.06 mol) wereheated at 155-160" (3 min).The solid that separated oncooling and dilution with dry ether (30 ml) gave the iso-thiazolium bromide as prisms (9.1 g, go), m.p. 123-124'(from ethanol-ether) (Found: C, 46.8; H, 3.85; N, 5.6.C1,H,,BrNS requires C, 46.8; H, 3.9; N, 5.45), ,(EtOH) 260 nm (E 6270), v,, 1070, 1500, and 875 cm-l,H-3), 2-25 (lH, q, H-4), 2-45 (5H, s, Ph), and 4.15 (2H, s,PhCH,) ; picrate, m.p. 120" (decomp.) (from aqueousethanol) (Found: C, 47-3; H, 3.1; N, 14.1.C,,H,,N,O,Srequires C, 47.5; H, 2-95; N, 14.0). No change in then.m.r. spectrum of (1; X = Br) was observed after 48 hin deuterium oxide, alone or in the presence of trifluoro-acetic acid.Treatment of the isothiazole with benzyl iodide a t 80"yielded the isothiazolium iodide (1; X = I) (20), m.p.115" (decomp.) (from ethanol) (Found: C, 39.25; H, 3-5;N, 4.5. C,,Hl,INS requires C, 39.5; H, 3.3; N, 4.6).The reaction of the bromide with silver toluene-9-sulphon-ate 22 in methanol-acetonitrile yielded the isothiazoliumtoluene-p-sulphonate (1 ; X = $J-M~C,H~*SO,) as plates(72), m.p. 90" (decomp.) (from acetone-ether, 9 : 1)(Found: C, 58.85; H, 5.2; N, 3.95. C1,Hl,N03S, requiresC, 58.8; H, 4.9; N, 4.05). The reaction of the bromidewith silver nitrate in water yielded the isothiazolium nitrate(1; X = NO,) (73y0), m.p.85-86" (decomp.) (frommethanol-ether) (Found: C, 60.35; H, 4.4; N, 11.65.C1,H,,N,03S requires C, 50.4; H, 4.2; N, 11.750(0). Ionexchange could not be effected with acetate ion.2-Methylisothiazolium Toluene-p-sulphonate (2 ; X =p-MeC,H,*SO,) .-Isothiazole (2-3 g, 0.025 mol) and methyltoluene-p-sulphonate (4.65 g, 0.025 mol) were heated slowlyT (DZO) 0.45 (lH, d, J 6.0 Hz, H-5), 0.70 (lH, d, J 2.0 Hz,to 115" and maintained a t this temperature (10 min). Thesolid that separated on cooling, after being washed withdry ether, gave the isothiazolium toluene-p-sulphonate asplates (4.8 g, 70y0), m.p. 134" (from ethanol-ether) (Found:C, 48.95; H, 4-65; N, 5.1.C,,H1,NO,S, requires C, 48.7;H, 4.8; N, 5.2), Am, (MeOH) 257 nm (E 7780), v,,1230-1180, 865, 810, and 690 cm-l, T (D,O) 0.73 (lH, d,J 6.0 Hz, H-5), 1.15 (lH, d, J 3.0 Hz, H-3), 2.55 (lH, 9,H-4), 2.38 (2H, d, J 8.0 Hz, 2 x Ortho-H), 2.82 (2H, d,J 8.0 Hz, 2 x meta-H), 5-98 (3H, s, NMe), and 7.73 (3H, s,C*CH,) ; picrate, m.p. 145" (from ethanol) (Found : C,36-8; H, 2.7; N, 17-1. C,,H,NO,S requires C, 36.6; H,2.45; N, 17.05).Treatment of isothiazole with methyl fluorosulphonate 5(cooling) yielded the isothiazolium Jluorosulphonate (2 ;X = SO,F) as prisms (71), m.p. 145" (from methanol-ether) (Found: C, 24-0; H, 2.75; N, 7.1. C,H,FNO,S,requires C, 24.1; H, 3.0; N, 7.0).2-Phenacylisothiazolium Bromide (3 ; X = Br) .-Iso-thiazole (1.7 g, 0-02 mol) and phenacyl bromide (3.98 g,0.02 mol) were heated a t 85" (5 min).The solid thatseparated on cooling and dilution with dry ether gave theisothiazolium bromide as pale yellow needles (3.0 g, 53y0),m.p. 170" (decomp.) from ethanol (charcoal) (Found: C,46.8; H, 3.55; N, 5.0. C,,Hl,BrNOS requires C, 46.45;H, 3.5; N, 4.9), A,, (MeOH) 248 (E 12,100) and 334 nm(1250), v,, 1700 and 870 cm-l, T (D,O) 0.40 (lH, d, J6.0 Hz, H-5), 0.90 (lH, d, J 2.5 Hz, H-3), 1-92-2-06 and2-22-2.53 (6H, m, Ph and H-4), and 3.60 (2H, s, PhCO-CH,).2-Benzyl-5-~henylisothiazoZium Perchlorate (4 ; X = ClO,) .-Benzyl bromide (1.71 g, 0.01 mol) and 5-phenyliso-thiazole6 leg1 g, 0.01 mol; this is actually a mixture of3- and 5-phenylisothiazoles containing (g.1.c.) 92 of thelatter were heated to 90".The solid that separated oncooling and dilution with dry ether gave the isothiazoliumbromide (4; X = Br) as plates (0.34 g, lo), m.p. 95-96'(from ethanol). This had the expected n.m.r. spectrum butno satisfactory analysis was obtained so i t was convertedinto the isothiazolium perchlorate as needles, m.p. 145'(decomp.) (from propan-2-01) (Found: C, 54-95; H, 4.05;N, 4.0. C,,Hl,CINO,S requires C, 54.7; H, 4.0; N, 4*0y0),A,, (MeOH) 313 nm (E 17,350), vmX. 1500, 1470-1460, and890 cm-1, T (CD,),SO 0.37 (lH, d, J 3.0 Hz, H-3), 1.72(lH, d, J 3.0 Hz, H-4), 1.90-2.15 (lOH, m, 2 x Ph), and4.06 (2H, S , PhCH,).2-Methyl-5-phenylisothiazoliurn Fluorosulphonate (5 ; X =S0,F) .-Methyl fluorosulphonate (0.6 g, 0.005 mol) and5-phenylisothiazole (0.805 g, 0.005 mol) were mixed (dry-ness essential).Heat was evolved and the solid thatseparated, after being washed with dry ether, yielded theisothiazolium jluorosulphonate as plates (0.86 g, 64), m.p.134135" (from ethanol) (Found: C, 43-5; H, 3-85; N,4-9. C,,H,,FNO,S, requires C, 43.6: H, 3.65; N, 5 ~ 1 ) ~Am= (MeOH) 265 (E 5590) and 309 nm (16,100), vmX. 1475-1440, 1310-1250, 850, and 690 cm-l, T (CD,),SO 0.632.12 and 2.25-2-44 (2H and 3H, m, Ph), and 5.68 (3H, s,NMe); picrate, m.p. 128" (from water) (Found: C, 47.36;H, 3.1; N, 13.9. C,,H,,N,O,S requires C, 47-5; H, 3.1;N, 13.9).Larger scale (15 g) recrystallisation of the crude fluoro-sulphonate from ethanol yielded only 25 of pure material.(lH, d, J 3.0 Hz, H-3), 1-83 (lH, d, J 3.0 Hz, H-4), 1.98-J.C . Sauer, Org. Syntlz., 1963, Coll. Vol. IV, p. 813.22 N. Kornblum, W. J. Jones, and G. J. Anderson, J . Amer.Chem. SOC., 1959, 81, 41131972 2311Addition of the mother liquor to dry ether yielded material(65) containing one mol. equiv. of ethanol (n.m.r.spectrum), m.p. 85-90" (Found: C, 49-4; H, 5.1; N, 5-05.CloHloFN0,S2,C2H,0H requires C, 49.8; H, 5-5; N,4.85). The solvent was not removed on prolongedheating a t 60" in vacuo or on recrystallisation from acetone-ether (1n.p. 90-92").2-Phenacyl-5-phenylisothiazolium Bromide (6 ; X = Br) .-Phenacyl bromide (1-99 g, 0.01 mol) was added to molten5-phenylisothiazole (1.61 g , 0.01 mol) and the mixture wasmaintained a t 80".Cooling and addition of dry etherafforded a gum which yielded the isothiazolium bromide(0.38 g, lo), m.p. 156-157" (decomp.) from ethanol-ether (charcoal) (Found: C, 56.6; H, 3.8; N, 3.8.Cl,H14BrN03 requires C, 56.65; H, 3.9; N, 3.9), Amax.(MeOH) 255 nm ( 17,900), vmx. 1700, 1600, and 870 cm-l,and 2.32-2.58 (11H, m, PhCO, Ph, and H-4), and 3.68 (2H,s, PhCO-CH,).2-Methyl-3,5-diphenylisothiazolium Fluorosulphonate ( 8 ;X = S0,F) .-3,5-Diphenylisothiazole (0.59 g, 0.0025 mol)and methyl fluorosulphonate (2 ml; excess) were heateduntil the mixture became homogeneous. The solid thatseparated on cooling, after being washed with dry ether,yielded the isothiazolium fluorosulphonate as needles (0-60 g ,68y0), m.p.158-160" (from ethanol) (Found: C, 54.55;H, 3.9; N, 4.1. C16Hl,FN03S, requires C, 54.8; H, 4.0;N, 4.0y0), A,, (MeOH) 315 nm (E 23,300), vmX. 1540, 1460,1310-1260, 815, and 710-690 cm-l, T (CD,),SO 1.59(lH, s, H-4), 1.90-2.19 and 2-20-2.42 (lOH, m, 2 x Ph),and 5.80 (3H, s, NMe); picrate, m.p. 155" (from water)(Found: C, 54.55; €3, 3-35; N, 11.9. C,2Hl,N,07S re-quires C, 56.0; H, 3.35; N, 11.65).Larger scale (15 g) recrystallisation of the fluorosulphonatefrom ethanol yielded two fractions: plates, m.p. 205" (25)and needles, m.p. 169-160" (30). Both had the sameanalytical figures as before and their i.r. and n.m.r. spectrawere identical ; they are apparently polymorphic forms.Addition of the mother liquor to dry ether gave a furtherproduct, m.p.128-130" (32) whose n.m.r. spectrum(CD,),SO showed the presence of 1 mol. equiv. of ethanol,which was not removed on heating in vacuo or on re-crystallisation from acetone-ether. Recrystallisation ofthe m.p. 205" product from propan-2-01 led to only 40recovery; addition of the mother liquor to dry etheryielded a further product, m.p. 118", whose n.m.r. spectrum(CD,),SO indicated the presence of 1 mol. equiv. ofpropan-2-01. This solvent too was not removed on heatingin vacuo or on recrystallisation from acetone-ether.1,2-Dithiolium Salts.-3-Phenyl- 1,2-dithiolium perchlor-ate (10; X = ClO,) was made by the method of Klings-berg; picrate, m.p. 159-160" (from ethanol) (Found: C,44.5; H, 2.4; N, 10.0. C1,HgN,07S, requires C, 44.25;H, 2.2; N, 10.3).3,5-Diphenyl-1,2-dithiolium per-chlorate (11; X = ClO,) was made by the method ofBehringer and Grimm ; hydrogen sulphate, yellow needles,m.p. 210-212" (decomp.) (from ethanol) (Found: C, 51.5;H, 3-8; S, 27.5. C1,Hl,O,S, requires C, 51.2; H, 3.55;S, 27.3) ; periodate, m.p. 152-153" (decomp.) (Found:C, 40.25; H, 2.5; S, 14.0. Cl,Hl,IO,S, requires C, 40.35;H, 2.7; S, 14.1); picrate, m.p. 205" (from ethanol-dimethyl sulphoxide) (Found: C, 51-7; H, 2-5; N, 8.8.C21H1,N,0,S2 requires C, 52.15; H, 2.7; N, 8.7). 3-Methylthio-5-phenyl-1,2-dithiolium iodide (12; X = I) wasmade by methylation of the corresponding 3-thione ; 10z (D2O) 0.98 (lH, d, J 3.0 Hz, H-3), 1.88-2.08, 2'23-2.30,similar benzylation yields the 3-thiobenzyl salt ( 13 ; X = Br),m.p.130" (decomp.) (from ethanol-ether), T (CD,),SO 0.96(lH, s, H-4), 1.9 (5H, d, Ph), 2-20-2.60 (5H, m, PhCH,),and 4.98 (2H, s, PhCH,), and phenacylation yields the3-thiophenacyl salt (14; X = Br), m.p. 151-153" (decomp.)(from acetone-ether, 10 : l), z (CD,),SO 0.88 (lH, s, H-4),1.68-2.00 and 2.18-2.58 (lOH, m, Ph and PhCO), and4-18 (2H, S, PhCOCH,).Oxidation of 2-Benzylisothiazolium Bromide.-2-Benzyl-isothiazolium bromide (2.56 g) was stirred with potassiumpermanganate (7.0 g) in water (20 ml) containing sulphuricacid (5 ml), first a t room temperature then at 80". Additionof sodium hydrogen sulphite (10 g), filtration (hot), de-dolourisation with charcoal, filtration (hot), and coolingyielded benzoic acid (0.75 g, 61), m.p.and mixed m.p. 120O.Metal Salt Complexes of 2-Benzylisothiazoliunz Bromide.-Treatment of 2-benzylisothiazolium bromide (1.28 g, 0.005mol) in dry methanol (10 ml) with mercury(r1) chloride(1.35 g, 0.005 mol) in methanol yielded the isothiazoZiunzbromide-mercury (11) chloride complex as prisms (2.2 g, 85 ) ,m.p. 140-141" (decomp.) (from acetone-dimethyl sulph-oxide, 4 : 1) (Found: C, 22.85; H, 2.05; N, 2.7.CloHl,BrNS,HgC12 requires C, 22.8; H, 1.9; N, 2.65);treatment with mercury(11) bromide gave the conzplex(85), m.p. 110" (decomp.) (Found: C, 25-3; H, 1.85;N, 2-95. C1,Hl0BrHgNS requires C, 26.3; H, 2.2; N,3.05). Lead nitrate in aqueous solution yielded thecomfilex (27y0), m.p. 167-168" (from acetonitrile) Found:C, 20.6; H, 1.7; N, 6.9.CloHloBrNS,Pb(NO,), requiresC, 20.4; H, 1.7; N, 7-1y0. Antimony trichloride inethanol yielded the complex, m.p. 150" (decomp.) (fromethanol-ether), T (CD,),SO 0-44 (lH, d, J 3.0 Hz, H-3),0.48 (lH, d, J 6-0 Hz, H-3), 2.33 (lH, q, H-4), 2.52 (5H, m,Ph), and 4.14 (2H, s, PhCH,).Action of Nitrogen Nucleophiles on Isothiazolium Salts.-(a) Ammonia. (i) 2-Benzylisothiazolium bromide (1 ; X =Br). Dry ammonia gas was passed (4 h) through a stirredsolution of 2-benzylisothiazolium bromide (2.56 g, 0.01 niol)in ethanol (saturated with dry ammonia). Excess ofammonia was evaporated off (15") and the solution wasdivided into two equal portions. Preparative g.1.c. on oneportion (20 f t DEGS column; oven temp.85"; 50 ml min-1)yielded isothiazole (tB 9.8 min) (67), identical (n.m.r. andi.r. spectra) with authentic material. The other portionwas concentrated and diluted with water (5 ml) ; treatmentwith aqueous picric acid yielded benzylamine picrate (ca.20), m.p. and mixed m.p. 195-196".(ii) 2-Methyl- 3,5-diphenylisothiazoZiam jluorosulphonate(8; X = S0,F). Similar treatment of 2-methyl-3,5-diphenylisothiazolium fluorosulphonate (0.1 75 g, 0.0005mol) yielded 3,5-diphenylisothiazole (0.101 g, 85), m.p.and mixed m.p. 81", identical (i.r. spectra) with authenticmaterial. The mother liquors yielded methylamine picrate(65), m.p. and mixed m.p. 207-208".(b) Hydrazine. (i) 2-Benzylisothiazolium bromide (1 ;X = Br). 2-Benzylisothiazolium bromide (1.28 g, 0-005mol) was dissolved in methanol and a methanolic solutionof hydrazine prepared from hydrazine hydrochloride(0.343 g, 0.005 mol) and sodium methoxide (0.27 g, 0.005mol) was added.After 24 h the separated sulphur (0.14 g,88) was removed, the solvent was evaporated off, and theresidue was extracted with ether to yielded pyrazole (0-07 g,20) (from light petroleum), m.p. and mixed m.p. 69-70",U.V. and n.m.r. spectra identical with those of authenticmaterial. Recrystallisation of the initial, ether-insolubl2312residue from ethanol-ether yielded benzylamine hydro-bromide (0.52 g, 56), m.p. and mixed m.p. 220". Asimilar reaction with ethanolic hydrazine hydrate yieldedpyrazole (21), and replacement of the bromide by thetosylate (1; X = p-MeC6H4S03), and by 2-methyliso-thiazolium tosylate (2; X = p-MeC,H4S03), yielded 18 and25 of pyrazole, respectively.(ii) 2-Methyl-3,5-dip henylisothiazolium fluorosulphonate(8; X = SO,F).Similar treatment of 2-methyl-3,5-di-phenylisothiazolium fluorosulphonate (0.175 g, 0.005 mol)with ethanolic hydrazine hydrate yielded 3,5-diphenyl-pyrazole (0.068 g, 62), m.p. 200" (lit.,23 ZOO") (fromethanol) (Found: C, 81.6; H, 5-55; N, 13.0. Calc. forC,,H,,N,: C, 81.8; H, 5.45; N, 12.7). Methylaminecould also be isolated as the picrate (48), m.p. and mixedm.p. 207".(c) Phenylhydrazine. (i) 2-Benzylisothiazoliurn bromide(1; X = Br). Phenylhydrazine (1.08 g, 0.01 mol) inethanol (20 ml) was added to 2-benzylisothiazolium bromide(2-56 g, 0.01 mol) in ethanol (20 ml).After 24 h the solventwas removed and the residue extracted with ether. G.1.c.(5 f t 10 Apiezon column; oven temp. 200"; H,, 100ml min-l) showed the presence of I-phenylpyrazole (sameretention time as authentic material: 3 min) in 53 yield,i.r. and n.m.r. spectra identical with those of authenticmaterial. The ether-insoluble residue yielded benzylaminehydrobromide (0.80 g, 43), m.p. and mixed m.p. 220°,and sulphur (from carbon disulphide) (0.15 g, 48).Similar treatment of 2-methylisothiazolium tosylate (2 ;X = p-MeC,H,*SO,) yielded l-phenylpyrazole (50),methylamine tosylate (52), m.p. and mixed m.p. 147-148", and sulphur (38).(ii) 2-Methyl-3,5-di~henylisothiazolium fluorosulphonate(8; X = S03F).Phenylhydrazine (0.108 g, 0.001 mol) inethanol (10 ml) was added to a vigorously stirred suspensionof 2-methyl-3,5-diphenylisothiazolium fluorosulphonate(0.17 g, 0.0005 mol) in ethanol (20 ml). After 1 h themixture was heated under reflux (4 h), the solvent removed,and the residue extracted into chloroform. Removal ofthe solvent under vacuum yielded 1,3,5-triphenylpyrazole(0.072 g, 48), m.p. 140" (lit.,24 137-138") (from ethanol)(Found: C, 85.2; H, 5.55; N, 9.5. Calc. for C2,H1,N2:C, 85-15; H, 5-4; N, 9.45). The chloroform-insolubleresidue yielded methylamine picrate (50), m.p. andmixed m.p. 206-207".(d) Hydroxylamine. (i) 2-Methyl-5-phenylisothiazoZiumfluorosulphonate (5; X = SO,F). A solution of hydroxyl-amine from hydroxylamine hydrochloride (0.695 g, 0.01mol) and ethanolic sodium ethoxide ( 0 .8 ~ ; 12.8 ml, 0.01mol) in ethanol (50 ml) was added slowly to a stirredethanolic solution of 2-methyl-5-phenylisothiazolium fluoro-sulphonate monoalcoholate (1.605 g, 0.005 mol). Thesolution was heated under reflux (0.5 h), cooled, and con-centrated under vacuum (15 ml). Dilution with etheryielded inorganic material which was filtered off; removalof the solvent under vacuum yielded a yellow oil whichdeposited sulphur on dilution with chloroform. G.1.c. ofthe chloroform solution (6 f t 5 APL + Berlone column;oven temp. 150") showed the presence of 3-phenyl- and5-phenyl-isoxazoles ( t ~ 48 and 62 s, respectively ; identicalwith those of authentic materials inserted concurrently).Quantitative g.1.c. showed a total isoxazole yield of 20(3-phenyl : 5-phenyl 5 4 : 1).Removal of chloroform fromthe main solution, extraction with hot ether, concentrationof the ethereal solution, and cooling afforded 5-phenyliso-J.C.S. Perkin Ithiazole N-oxide (24b) as needles (0.35 g, 40), m.p. 92-93'(decomp.) (from ether) (Found: C, 60.75; H, 4.15; N,7.7; S, 17.9; M+, 177. C,H,NOS requires C, 61.0;H, 3.95; N, 7.9; S, 18.05'70; M, 177), A,, (Et,O) 352, 262,and 232 nm 5-phenylisothiazole, AmX. (Et,O) 267 nm,A,=. (MeOH) 335, 261, and 225 nm, A,, (M-HC1) 320, 260,and 224 nm, vmX. (solid and CS,) 1280 crn-l, vmXa (CS,MeOH) 1260 cm-l, z (CDC1,) 2.27 (lH, d, J 2.5 Hz, H-3),2-63 (5H, s, Ph), and 3.25 (lH, d, J 2-5 Hz, H-4), mle 177(35), and 90 (10).Conversion of 5-Phenylisothiazole N-Oxide (24b) into 5-Phenylisothiazo1e.-Gradual addition of phosphorus tri-chloride (0.083 g, 0.0006 mol) to 5-phenylisothiazole N-oxide(0-075 g, 0.0004 mol) resulted in a violent reaction with theformation of a yellow oil which solidified on addition ofcrushed ice.Extraction with ether and preparative t.1.c.(silica in chloroform) yielded 5-phenylisothiazole (0.045 g,65y0), m.p. and mixed m.p. 46-47", identical (i.r. spectra)with authentic material.(ii) 2-Methyl-3,5-diphenylisothiazoliurn fluorosulphonate(8; X = S0,F). 2-Methyl-3,5-diphenylisothiazoliumfluorosulphonate monoalcoholate (1.99 g, 0.005 mol) andhydroxylamine (0.005 mol; see before) were heated underreflux (4 h) in ethanol (20 ml).Removal of solvent invacuum, extraction of the residue with hot benzene, andevaporation yielded 3,5-diphenylisoxazole (0.30 g, 27 yo),m.p. from benzene-ether (charcoal) and mixed m.p. 141",identical (n.m.r. and i.r. spectra) with authentic material.Extraction of the benzene-insoluble residue with hot ether-ethanol (15 : 1) and concentration of the solution yielded3,5-diphenylisothiazole N-oxide (24a) (0.15 g, 12y0), m.p.199-201' (decomp.), vma, (solid) 1260 cm-l, 7: (CDCI,)1.7-1.9 and 2.4-2-6 (lOH, m, 2 x Ph), and 2.7 (lH, s,H-4). Treatment of the N-oxide (0.10 g) with phosphorustrichloride a t 80" yielded 3,5-diphenylisothiazole (0.07 g,70), m.p. from petroleum (b.p. 40-60") and mixedm.p. 81", identical (i.r.spectra) with authentic material.Similar treatment of 2-benzylisothiazolium bromide ( 1 ;X = Br) yielded only benzylamine as picrate and somesulphur.(e) BenzyZamine. (i) 2-Methyl-3,5-diphenylisothiazoliumfluwosulphonate (8; X = SO,F). Benzylamine (0.318 g,0.006 mol) and 2-methyl-3,5-diphenylisothiazolium fluoro-sulphonate (0-702 g, 0.002 mol) in ethanol were heatedunder reflux (4 h). T.1.c. (silica; toluene-chloroform, 5)showed five spots (one major). Column chromatography(silica gel; elution with toluene-chloroform, 10) yielded,from the first fraction, 3-benzylarnino-l,3-di~henylpropene-l-thione (26) as red needles (0.36 g, 55), m.p. 115-116"(decomp.) (from ethanol) (Found: C, 80.3; H, 5.95; N,3-95. C,,H,,NS requires C, 80.25; H, 5.75; N, 4-2y0),A,, (Me,SO) 308 and 418 nm (E 23,100), v,, 1200, 1130,and 700 cm-l, z (CDCI,) 2.16-2-30 and 2.42-2.84 (15H,unsym. m, 3 x Ph), 3.36 (lH, s, H-2), 5.45 (2H, d, J 6.0 Hz,PhCH,), and -2-95br (lH, NH).Titration of theamino-thione (0.329 g) in warm ethanol with saturatedethanolic iodine solution yielded 2-benzyl-3,5-diphenyliso-thiazolium tri-iodide (28; X = 13) as brown columns (0.38 g,54y0), m.p. 147-148" (decomp.) (from nitromethane)(Found: C , 37.4; H, 3.0; N, 2.0. C,,H1,I,NS requiresC, 37-25; H, 2.65; N, 1-9yo), Amax. (Me,SO) 301 nm (c39,300), v,, 1530 and 850 cm-l, z (CD,),SO 1-52 (lH, s,(M', loo), 161 (M+ - 16, 85), 134 (25), 121 (35), 102s3 P. Duden, Ber., 1893, 26, 117.24 L. Knorr and H. Laubmann, Ber., 1888, 21, 12011972 2313H-4), 1.90-2.15 and 2.20-2.40 (lOH, unsym.m, 2 x Ph),2.53 (5H, s, PhCH,), and 4.21 (2H, s, PhCH,).(ii) 2-Methyl-5-phenyZisothiazoZium fluorosulphonate (5 ;X = S0,F). 2-Methyl-5-phenylisothiazolium fluoro-sulphonate (0.688 g, 0.0025 mol) was stirred with benzyl-amine (0.268 g, 0.0025 mol) in ethanol until all had dissolved(4 h), T.1.c. (silica; toluene-chloroform, 5) of the deepred solution showed one major and three minor spots. Themajor spot 3-benzylamino- l-phenylpropene- l-thione (25)was not obtained crystalline after column chromatography,but oxidation with ethanolic iodine followed by ion exchangewith perchlorate yielded 2-benzyl-5-phenylisothiazoliumperchlorate (4; X = C10,) as needles (0-42 g, 48y0), m.p.(from propan-2-01) and mixed m.p.145" (decomp.), identical(i.r. and n.xi1.r. spectra) with authentic material.Similar treatment of 2,5-diphenylisothiazolium per-chlorate (7 ; X = ClO,) yielded 2-benzy1-5-phenyZiso-thiazolium tri-iodide (4; X = I,) as brown needles (36y0),m.p. 125" (decomp.) (from nitromethane) (Found: C, 30.2;H, 2.35; h-, 2.15. C1,H1,I,NS requires C, 30.35; H, 2.2;N, 2.2).(iii) 2-Benzylisothiazolium Bromide (1 ; X = Br) .-Addi-tion of benzylamine (0.214 g, 0.002 mol) to a solution of2-benzylisothiazolium bromide (0-512 g , 0.002 mol) inethanol resulted in a dark brown colouration and theseparation of a small amount of brown solid. Removal ofthe solvent (vacuum), and washing with chloroform andthen acetone yielded the hydrobromide (29) as needles(0.269 g, 41y0), m.p.208-210" (from water) (Found: C,61.45; H, 5-7; N, 8.5. C17H1,BrN2 requires C, 61.6; H,5.75; N, 8-5), A,, (MeOH) 238 and 304 nm, v,, 3200,1620, 750, and 700 cm-l, m/e 250 (M+ - 81, 14), 160(64), and 91 (100). Attempts to prepare the picrate andthe free base were unsuccessful.(f) A niline. (i) 2-MethyZ-5-phenyZisothiazolium ~7uoro-sulphonate (5; X = SO,F). 2-Methyl-5-phenyliso-thiazolium fluorosulphonate (0.55 g, 0-002 mol) was heatedunder reflux with aniline (0.186 g, 0.002 mol) in ethanoluntil all had dissolved. Column chromatography (silica ;benzene-chloroform, 5) yielded 3-anilino-l-phenylpro-pene-l-thione (27) (0.144 g, 30), m.p. 105-106° (lit.,15106O), AmX. (CH,CI,) 226, 236, 250, 324, and 440 nm (lit.,l5225, 236, 250, 324, and 440 nm).Titration of the amino-thione in ethanol with saturated ethanolic iodine solutionyielded 2,5-di~henyZisothiazolium tri-iodide (7 ; X = I,) asbrown columns (52), m.p. 129" (decomp.) (from nitro-methane) (Found: C, 29.25; H, 2.0; N, 2.5. C15H1213NSrequires C, 29.1; H, 1.95; N, 2.25y0), v,, 1580, 880, and820 cm-l, T (CD,),SO 0.08 (lH, d, J 3-0 Hz, H-3), 1.47(lH, d, J 3.0 Hz, H-4), and 1.18-2.10 and 2.15-2.40 (lOH,unsym. m, 2 x Ph).Heating of 2-methyl-3,5-diphenylisothiazolium fluoro-sulphonate (8; X = SO,F) under reflux with aniline (3 mol.equiv.) in ethanol for 24 h led only to recovery of startingmaterial.(ii) 2-Benzylzsothiazolium. bromide ( 1 ; X = Br) .-Aniline(0.186 g, 0.002 mol) was added t o a solution of S-benzyliso-thiazolium bromide (0.512 g, 0.002 mol) in ethanol (10 ml),and the solvent was removed (vacuum) from the dark redsolution after 24 h.The residue was washed with ether,then with acetone, to yield the hydrobromide (30) as plates(0.201 g, 32), m.p. 179-180" (decomp.) (from acetone-water, 10 : 1) (Found: C, 60-0; H, 5-2; N, 8.8. Cl,H1,BrN,requires C , 60.4; H, 5.3; N, 8*8), Anlax. (MeOH) 233 and345 nm, vnlaX. 3120, 1650, 1600, 752, and 748 cm-l, m/e 236(M+ - 81, 50y0), 160 (ZO), and 91 (100). Attempts toprepare the picrate and the free base were unsuccessful.(g) 2-Aminoethanethi01.~~ (i) 2-Methyl-5-phenylisothiazo-lium fluorosulphonate (5; X = SO,F).-Addition of asolution of 2-methyl-5-phenylisothiazolium fluorosulphonate(0.688 g, 0.0025 mol) in dry methanol t o a methanolicsolution of 2-aminoethanethiol (0.193 g, 0.0025 mol) undernitrogen resulted in a red colouration and the slow separ-ation of 3- (2-mercaptoethylamino) - l-phenylpropene- 1 -thione(31) as red needles (0.264 g, 48y0), m.p.136-137" (decomp.)(from acetonitrile) (Found: C, 59.05; H, 5.51; N, 6.3; S,28-5. Cl1Hl3NS, requires C, 59-2; H, 5.7; h', 6-25; S,28.7), Am, (CH,CI,) 309 and 407 nm (E 12,800 andl9,000), vmX. 3450, 1610, 1500, and 1120 cm-l, T (CDCI,)2.25 (lH, q, H-3), 2.5-2.8 (5H, m, Ph), 3.5 (lH, d, J S.0 Hz,8.50 (lH, unsym. m, SH), and -3.6br (lH, NH). Titrationof this thione in ethanol with saturated ethanolic iodinesolution yielded the isothiazolium disulphide hi-iodide (33)as brown needles (0.376 g, 63), m.p.145-146" (decomp.)(from nitromethane) (Found: C, 22.0; H, 1.9; 8, 2.65.c22H2216Nz~4 requires C, 21.9; H, 1-85; X, 2.3), A,,(Me,SO) 249 and 263 nm (E 12,700 and 19,000), T (CD,),SO2.24-2-45 (5H, m, Ph), and 4-88-51 (4H, m, CH,CH,).(ii) 2-Methyl- 3,5-diphenyZisothiazolium Jluorosu1;bhonate(8; X = S0,F). 2-Aminoethanethiol (0.308 g, 0.004 mol)and 2-methyl-3,5-diphenylisothiazolium fluorosulphonate(0.702 g, 0.002 mol) in methanol were heated at 60" undernitrogen (0.5 h); the reaction mixture was filtered, thefiltrate concentrated (vacuum), and the residue chromato-graphed on silica gel (80 g ; elution with dichloromethane).The main fraction yielded 3-(2-mercapioethylamino) - 1,3-diphenylpropene-l-thione (32) as red plates (0.34 g, 57),m.p.88-90' (decomp.) (from propan-2-01) (Found : C,68.55; H, 5.75; N, 4.9. C17H17NS, requires C, 68.2; H,5.7; N, 4.7), Am, (CHC1,) 309 and 414 nm (E 1197 and23,990), vmx. 1610, 1490, and 1080 cm-l, 7 (CDCI,) 32-2-36and 2.58-2.82 (lOH, unsym. m, 2 x Ph), 3-44 (lH, s,8.20 (lH, unsym. m, SH), and -4.35br (lH, NH), m/e 299(M+, 25) and 266 (100). Oxidation of the thione withethanolic iodine yielded the isothiazolium disulphide tri-iodide (34) as dark brown needles (68), m.p. 159-160"(decomp.) (from nitromethane) (Found: C, 30.25; H, 2.3;N, 2.1. C,,H,,I,NzS4 requires C, 30.05; H, 2.2; N, 2.05y0),A,, (Me,SO) 365 nm (c 13,770).Action of Sulphur NucZeofihiles on Isothiazolium Salts.-(a) Benzenethiol.(i) 2-Methyl- 3, dip henylisothiazoliumperchlorate (8; X = C10,). A suspension of 2-methyl-3,5-diphenylisothiazolium perchlorate (0.85 g, 0.0025 mol) inethanol was heated under reflux with sodium benzene-thiolate (0-33 g, 0-0025 mol). The mixture showed twomain components on t.l.c., one of which was identified asdiphenyl disulphide. Removal of the solvent (vacuum),extraction into chloroform, and chromatography of theextract (silica gel ; elution with toluene-chloroform, 5)yielded a red gum which was not crystallised. Its n.m.r.spectrum, T (CDC1,) 2.2-2-8 (lOH, m, 2 x Ph), 3.40 (lH,s, H-2), 7.05 (3H, d, J 6.0 Hz, NMe), and -4-3br (lH, NH),was as expected for 3-methylamino-l,3-diphenylpropene-l-thione (55); this was confirmed by oxidation withiodine to yield 2-methyl-3,5-diphenylisothiazolium tri-iodide, m.p.150-151" (lit.,' 150-151").H-2), 6.35 (2H, q, CH2CH2*SH), 7.08 (2H, t, CH,*CH,.SH),0.50 (lH, d, J 3.0 Hz, H-3), 1.73 (lH, d, J 3.0 Hz, H-4),H-2), 6.4 (2H, 9, CH2CH,*SH), 7.10 (ZH, t, CH,*CH,*SH),25 S . Gabriel and J. Coleman, Ber., 1912, 45, 16432314 J.C.S. Perkin I(ii) 2-Methyl-5-phenylisothiazolium perchlorate (5 ; X =C10,). Benzenethiol (0.14 g, 0.0013 mol) and 2-methyl-5-phenylisothiazolium perchlorate (0.35 g, 0.00 13 mol) werestirred in ethanol (24 h) and then heated under reflux (1 h) .Chromatography yielded 3-methylamino- l-phenylpropene-l-thione (35), z (CDCl,) 2.35 (lH, q, H-3), 2.5-2-95(5H, m, Ph), 3-60 (lH, d, J 8-0 Hz, H-2), 6.95 (3H, d, J6.0 Hz, NMe), and -3-5br (lH, NH), which, on oxidationwith iodine and ion exchange, was converted into 2-methyl-5-phenylisothiazolium perchlorate, m.p.and mixed m.p.144-1 45".(i) 2-Bevtzylisothiazoliunz bromide(1; X = Br). Hydrogen sulphide was bubbled (15 min)through an aqueous solution of 2-benzylisothiazoliumbromide (0-5 g). The separated yellow solid was collectedand extracted into chloroform-acetone (1 : 1) ; the extractwas dried (MgSO,) and chromatographed (silica gel ;elution with toluene-chloroform, 10) to yield bis- 1,2-dithiol-3-yl sulphide (37) (15), m.p. 102-105° (decomp.)(Found: C, 30.3; H, 2.35. C,H,S, requires C, 30.25; H,2.5y0), hmx. (MeOH) 220 and 300 nm. The sulphide de-composed readily in air.Benzylamine could be recoveredfrom the mother liquors as picrate (43). The sulphide ontreatment in chloroform-methanol with hydrogen iodideyielded the 1,2-dithiolium iodide (9; X = I), m.p. 179-182" (from propanol) (lit.,2e 179-181"), i.r. absorptions1430, 1050, and 810 cm-l) identical with those(ii) 2-Methyl-5-phenylisothiazoliurn jluorosulphonate (5 ;X = SO,F). Similar treatment yielded bis-(5-phenyZ-lJ2-dithiol-3-yl) sulphide (38) (68), m.p. 122-124" (decomp.)(from benzene-acetone, 19 : 1) (Found: C, 55.5; H, 3.65;S, 41.2. Cl8HI4SS requires C, 55-35; H, 3.7; S, 41.0y0),A,, (CHCl,) 247 and 364 nm (E 22,400 and 19,900), urn=1590 cm-l, z (CDSO-CDCl, (1 : 3) 2.42-2-80 (5H, m,Ph) and 3-76-4.02 (2H, unsym. m, H-3 and H-4). Methyl-amine could be recovered from the mother liquors aspicrate, and the sulphide on treatment with perchloric acid(70) in dichloromethane-ether yielded the 3-phenyl- 1,2-dithiolium perchlorate (10; X = ClO,) (70), m.p.andmixed m.p. 182-183".2-Phenacyl-5-phenylisothiazolium bromide (6 ; X = Br)yielded the same sulphide (60).(iii) 2-Methyl-3,5-diphenylisothiazolium jluorosulphonate(8; X = SO,F). Similar treatment of 2-methyl-3,5-di-phenylisothiazolium fluorosulphonate monoalcoholate (0.5g) yielded only a dark brown gum, non-homogeneous (t.1.c.)after column chromatography. Boiling the gum withdilute hydrochloric acid yielded the 3,5-diphenyl-1 , 2-dithiolium chloride (11; X = C1) (0.22 g, SO), m.p. andmixed m.p. 190-192", identical (i.r. spectrum) withauthentic material.Action of Nitrogen Nucleophiles on 1,2-Dithiolium Salts.-(a) Benzylamine.(i) 3,5-Diphenyl- 1 , 2-dithiolium per-clzlorate (1 1 ; X = CIO,) .s Benzylamine (0.43 g, 0.004 mol)was added to a suspension of 3,5-diphenyl- 1,2-dithioliumperchlorate (0.71 g, 0-002 mol) in ethanol and the stirredmixture was heated gently until homogeneous. Coolingyielded 3-benzylamino- 1,3-diphenylpropene- l-thione (26)(0-33 g, 50) (from ethanol), m.p. and mixed m.p. 115-116" (decomp.), which was converted on oxidation withiodine into 2-benzyl-3 , 5-diphenylisothiazolium tri-iodide(42) (from ethanol), M.P. and mixed m.p. 147-148"(decomp.). In both cases i.r. spectra were identical withthose of authentic material.(ii) 3-Phenyl-1,2-dithioZium perchlorate (10; X = ClO,) .*(b) Hydrogen sulphide.Similar treatment (heating for 1 h), followed by oxidationof the impure benzylamino-thione with iodine and ionexchange yielded 2-benzyl-5-phenylisothiazolium perchlor-ate (4; X = ClO,) (55) (from propan-2-01), m.p.andmixed m.p. 145", i.r. spectrum identical with that ofauthentic material,(i) 3,5-Diphenyl- 1 , 2-dithioliumperchlorate (11 ; X = ClO,). 2-Aminoethanethiol (0.39 g,0.005 mol) and 3, 5-diphenyl- 1,2-dithiolium perchlorate(0.89 g, 0-0025 mol) were heated under reflux (2 h) in anitrogen atmosphere. Work-up yielded 3- (2-mercapto-ethylamino)-l,3-diphenylpropene-l-thione (32) (41 ) (frompropan-2-01), m.p. and mixed m.p. 88-90" (decomp.), i.r.spectrum identical with that of authentic material.Iodineoxidation of the amino-thione yielded the bis-isothiazoliumdisulphide bistri-iodide (34), m.p. and mixed m.p. 159-160" (decomp.).(ii) 3-Phenyl-l,2-dithiolium perchlorate (10; X = ClO,).Similar treatment followed by preparative t.1.c. (silica;toluene-dichloromethane, 10) yielded 5-phenyl-1,2-di-thiole-3-thione (39) (31), m.p. and mixed m.p. 128-130",n.m.r. spectrum identical with that of authentic material.3- (2-Mercctptoethylamino) - l-phenylpropene- 1-thione (3 1)was detected (t.1.c.) but was not isolated nor satisfactorilyoxidised by iodine to the corresponding isothiazolium saltdisulphide (33).Action of Sulphur Nucleophiles on 1,2-Dithiolium Salts.-(a) Ethanethiol. (i) 3-Phenyl-1 , 2-dithiolium hydrogen sul-phate (10; X = HSO,).-Ethanethiol (0.37 g, 0.006 mol)and 3-phenyl-l,2-dithiolium hydrogen sulphate (1.38 g,0.005 mol) were dissolved in aqueous ethanol and thesolution was concentrated (vacuum) after 1 h.Addition ofether yielded 3-ethylthio-5-phenyl- 1,2-dithiole (40) as plates(0.96 g, 80) , m.p. 140' (decomp.) (from chloroform-ether)(Found: C, 54.95; H, 5.0; S, 40.1. Cl,Hl,S, requires C,55.0; H, 5.0; S, 40.0), Lx. (CHCI,) 296 and 271 nm(e 10,200 and 8430), vmX. 1580 cm-l, z (60 MHz; CDCl,)2.20-2.75 (5H, unsym. m, Ph), 4-10 (lH, d, J 9.0 Hz, H-3),4.87 (lH, d, J 9.0 Hz, H-4), 7.35-7.85 (2H, unsym. m,S*CH,*CH,), and 8.7-9-1 (3H, unsym. m, SCH,CH,).Treatment of the dithiole in chloroform-methanol solutioncontaining sulphuric acid ( 0 .1 ~ ; few drops) with perchloricacid (70) yielded 3-phenyl-lJ2-dithio1ium perchlorate (10X = C10,) (80), m.p. and mixed m.p. 182-183' (de-camp.), i.r. spectrum identical with that of authenticmaterial.(ii) 3,5-Diphenyl-l,2-dithiolium hydrogen sulphate (1 1 ;X = HSO,). Similar treatment followed by extractionwith ether yielded 3-ethylthio-3,5-diphenyl-l, 2-dithole (41) aspale yellow needles (60), m.p. 96-98' (decomp.) (frompropan-2-01) (Found: C, 64.7; H, 5.0; S, 30-65. C1,Hl,S,requires C, 64-55; H, 5.05; S, 30-4y0), = (CHCl,) 241 nm(E 16,500), vma= 1590 cm-l, T (60 MHz; CDCI,) 2.20-2.70(lOH, unsym. m, 2 x Ph), 3.70 (lH, s, H-4), 7.05 (2H, q,S*CH,*CH,), and 8-65 (3H, t, S*CH,*CH,). The dithiolewas converted by perchloric acid into 3,5-diphenyl-1,2-dithiolium perchlorate (11; X = ClO,), m.p.and mixedm.p. 259-260°, i.r. spectrum identical with that of authenticmaterial.(iii) 3-Methylthio-5-phenyl- 1 , 2-dithiolium iodide (1 2 ; X =I). The salt was recovered unchanged after exposure toethanethiol in ethanolic solution either at room temp.(4 h) or at 60" (2 h).(b) Thiobenzoic, thioacetic, and mercaptoacetic acids.*@ E. Klingsberg, Chem. and Ind., 1960, 1568.(b) 2-Aminoethanethiol1972(i) 3-Phenyl-l,2-dithiolium hydrogen sulphnte (10; X =HSO,). Thiobenzoic acid (0.345 g, 0,0025 mol) and 3-phenyl- 1,2-dithiolium hydrogen sulphate (0-69 g , 0-0025mol) were dissolved in aqueous ethanol; the separated solidwas collected after 2 h, the ethanol was removed, and theresidue was extracted with ether.The original solidcombined with that obtained from evaporation of theextract yielded 3-benzoylthio-5-phenyl-1,2-dithiole (42) (0.59g, 75), m.p. 194195' (decomp.) (from propan-2-01)(Found: C, 60.6; H, 3.75; S, 30.15. C,,H,,OS requiresC, 60.75; H, 3.8; S, 30.5), , (CH,Cl,) 241 and 273 nm(E 24,100 and 17,800), vmx. 1650, 1580, 920, and 760 cm-l,T (CC1,) 1.98-2.15 and 2-40-2.80 (lOH, unsym. m,2 x Ph), 3.48 (lH, d, J 4.0 Hz, H-3), and 3-82 (lH, d,J 4.0 Hz, H-4). Treatment of the 3-benzoylthio-adductwith perchloric and picric acids and with iodine yielded thecorresponding 3-phenyl-1,2-dithiolium salts (10 ; X = ClO,,C6H2N,0, or I), identical (mixed m.p.s, i.r. spectra) withauthentic materials.With thioacetic acid the adduct separated as an oil whichyielded 3-acetylthio-5-phenyl-1,2-dithiole (43) as a un-crystallisable brown gum (homogeneous on t.1.c.in chloro-form-methanol, 5) (79 yield), vmx. 3500, 1700, 1580,and 950 CIII-~, 7 (CCl,) 2.5-2.68 and 2.69-2.85 (unsym. m,H-41, and 7.78 (3H, s, SAC). This dithiole, too, could beconverted, as before, into the dithiolium salts (10; X = C10,or C,H,N,O,), and also the iodide (10; X = I) as brownneedles, m.p. 180" (decomp.) (Found: C, 35-55; H, 2.35;S, 20-6. C,H,IS, requires C, 36.3; H, 2.3; S, 20-9y0).Treatment of the dithiole with ethanolic aniline yielded3-anilino- l-phenylpropene-l-thione (27), 1n.p. and mixedm.p. 105-106".Mercaptoacetic acid yielded 3-carboxymethylthio-5-phenyl- 1 , 2-dithiole (44) as a hygroscopic, uncrystallisablegum (homogeneous on t.1.c.) (88), v,, 1690 and 1580 cm-l,T (CDC1,) 2.30-2-98 (5H, unsym.m, Ph), 3-89 (lH, d,J 4.0 Hz, H-3), 4.09 (lH, d, J 4.0 Hz, H-4), and 6-45 (2H,s, S*CH,CO,H). The dithiole was converted, as before,into the salts (10; X = ClO,, CeH2N3O7, or I) and into theanilino-thione (27).(ii) 3,5-DipJaenyl-l, 2-dithiolium perchlorate (1 1 ; X =ClO,). This salt was recovered unchanged after beingheated under reflux (2 h) with thiobenzoic, thioacetic, andmercaptoacetic acids in ethanol-acetone, aqueous ethanol,or dime th ylf ormamide.(iii) 3-iWethylthio-5-phenyl-l ,2-dithiolium Iodide (12 ; X =I) .-A suspension of 3-methylthio-5-phenyl- 1 , 2-dithioliumiodide (0-352 g, 0.001 mol) was heated (70-80'; 10 h) withthiobenzoic acid (0.277 g, 0.002 mol) in aqueous ethanol.Removal of the solvent (vacuum) , extraction of the residuewith ether, further removal of the solvent, and fractionalcrystallisation (acetone) yielded 5-phenyl- 1,2-dithiole-3-Ph), 3-82 (lH, d, J 4.0 Hz, H-3), 4.02 (lH, d, J 4.0 Hz,thione (39) (49), m.p.(from butyl acetate) and mixedm.p. 128-130", identical (Lr. spectrum) with authenticmaterial, and dibenzoyl disulphide (35), m.p. and mixedm.p. 130-131" (decomp.).Similar treatment with mercaptoacetic acid (1 h at 80')yielded, after column chromatography (silica gel; elutionwith toluene-chloroform), the thione (39) (40). Withthioacetic acid (2 h a t 80°), the original dithiolium salt (12;X = I) was recovered (66) and the thione (39) (5) wasobtained as its iodine complex (cj. ref. 27), m.p. and mixedm.p. 142-143' (decomp.) , identical (i.r. spectrum) withauthentic material.(c) Benzenethiol. (i) 3-Methylthio-5-phenyl- 1 , 2-dithioliunziodide (12; X = I). Sodium benzenethiolate (0.044 g,0.0003 mol) and 3-methylthio-5-phenyl-1,2-dithiolium iodide(0.1 g, 0-0003 mol) were heated under reflux in ethanol(6 h). T.1.c. showed the presence of diphenyl disulphideand of 5-phenyl-l,2-dithiole-3-thione (39), which could beobtained (preparative t.1.c.) in 60 yield).(ii) 3-Phenyl- 1,2-dithiolium perchlorate (1 0 ; X = ClO,) .Sodium benzenethiolate (0.165 g, 0-0013 mol) and 3-phenyl-lJ2-dithiolium perchlorate (0.345 g, 0.0013 mol) were heated(1.5 h) under reflux in ethanol. Work-up yielded thethione (39) (35).Similar treatment of 3,5-diphenyl- 1 , 2-dithiolium per-chlorate (11; X = ClO,) yielded no thione (39), only anunidentifiable gum.(d) Hydrogen sulphide. (i) 3-Methylthio-5-phenyl-l,2-dithiolium iodide (12; X = I). Hydrogen sulphide wasbubbled through a solution of 3-methylthio-5-phenyl- 1,2-dithiolium iodide (0.125 g) in aqueous ethanol (7 : 3) untilno more brown solid separated. Recrystallisation (butylacetate) yielded 6-phenyl-lJ2-dithiole-3-thione (39) (0.063 g,85), m.p. and mixed m.p. 128-130'. Similar treatmentof 3-phenacylthio-5-phenyl- 1,2-dithiolium bromide (14 ;X = Br) yielded the thione (39) (70).(ii) 3-PhenyZ-1,2-dithiolium hydrogen sulphate (10; X =HSO,) . Similar treatment of 3-phenyl- 1,2-dithioliumhydrogen sulphate (0.69 g) yielded bis-(5-phenyl-l,2-dithiol-3-yl) sulphide (38) (0-325 g, 70), m.p. (frombenzene-chloroform, 4 : 1) and mixed m.p. 122-124O(decomp.), identical (i.r. spectrum) with authentic material.Similar treatment of 3, 5-diphenyl- 1,2-dithiolium hydrogensulphate (11; X = HSO,) led only to recovery of the start-ing material.We thank Drs. D. M. McKinnon, R. A. Olofson, and R.Slack for gifts of material; one of us (H. U.) thanks theSaigol Foundation for a research grant and the PakistanAtomic Energy Commission for study leave.2/888 Received, 21st April, 1972327 N. Lozac'h and 0. Gaudin, Compt. rend., 1947, 225, 1162