Cyclisation of arylpropiolyl chloro-oxalyl anhydrides: the chemistry of aryl(chloro)methylenetetrahydrofuran-2,4,5-triones and theX-ray crystal structure of a 3,4-methylenedioxybenzylidene representative

摘要

138 J.C.S. Perkin ICyclisation of Arylpropiolyl Chloro-oxalyl Anhydrides : the Chemistry ofAryl (chloro)methylenetetrahydrof uran-2,4,5-triones and the X-rayCrystal Structure of a 3,4- M et hylened ioxybenzyl idene RepresentativeBy Michael J. Begley, Leslie Crombie,' Roger G. Havard, and Derek P. Reynolds, Department of Chemistry,3.4-Methylenedioxyphenylpropiolic acid and oxalyl chloride form a mixed anhydride which cyclises to give a red.water-sensitive aryl (chloro) methylenetetrahydrofuran-2.4.5-trione : its mixed Z,E-geometry has been investigatedby single crystal X-ray methods. Arylpropiolic acids with substituents providing sufficient electron release undergothe cyclisation, but in other cases arylnaphthalenedicarboxylic anhydrides and arylpropiolyl chlorides are formed.The mechanism of the cyclisation is considered, and some reactions of the trione are described.The University of Nottingham, Nottingham NG7 2RD, and University College, Cardiff CF1 3NRTREATMENT of a suspension of 3,4-methylenedioxy- red crystals of a new compound, C,,H,C10,, are formed.phenylpropiolic acid (1) in benzene with oxalyl chloride In this paper the chemistry and structure of the com-gives little of the expected propiolyl chloride: instead, pound are discussed, and the scope and mechanism of th1977 139reaction considered.1 The following paper deals withthe thermal rearrangement which it undergoes.ArcAr CO-R0 0 I0 0A r v C 0 2 RC02H( 9 )(6)A r0H(13 1A r = 3.4-(CH202)C6H3The red compound showed n.m.r. signals for threearomatic and two methylenedioxy protons, and hadv,, 1 869, 1 838, 1 788, and 1 723 cm-l, accommodatingan oxo-anhydride structure (2) or (3) which might beformed by cyclisation of a mixed anhydride (4).Structure (2) was shown to be correct by basic hydro-lysis to 3,4-methylenedioxybenzoylpyruvic acid (5 ;R = H; enolised).The latter could be degradedthermally to 3rsquo;,4rsquo;-methylenedioxyacetophenone (6) withloss of CO and CO,, or, by further treatment with base,to (6) and oxalic acid. Alcohols reacted with (2) togive the esters ( 5 ; R = Me or Et), and the latter wasresynthesised by Claisen condensation between (6) anddiethyl oxalate.ZE-Isomerism is possible for the vinylogous acidchloride structure (2), and the stereochemistry wasexamined by X-ray methods.The compound formedorthorhombic crystals, space-group Pbca, with unit celldimensions a = 7.95, b = 23.78, and c = 11.93 A,containing 8 molecules in the unit cell (one molecule perasymmetric unit). The structure was solved by theheavy-atom technique (664 reflections) and refined byblock-diagonal least-squares methods. Two views ofthe structure arrived at, which has Z-geometry, areshown in Figure 1, and Figure 2 shows the crystallo-graphic numbering.However, a difference map calculated after apparentconvergence (R 0.077) revealed an additional peak inthe neighbourhood of the ring oxygen atom 0(5)together with a lsquo;holersquo; at the oxygen atom of thecarbonyl 0(4). This was interpreted as indicating thepresence of a limited amount of E-isomer which had co-crystallised with the Z-.The two isomers are super-imposable in a space-filling sense, except for the carbonylFIGURE 1 (Z)-a-Chloro-3,4-methylenedioxybenzylidene-tetrahydrofuran-2,4,6-trione0161a4FIGURE 2 Crystallographic numbering schemeoxygen 0(4) which has to be moved between O(4) andO(7) with interchange between O(5) and C(11) (Figure 2).Refinement was therefore continued with an lsquo;extrarsquo;Preliminary account, L. Crombie, R. Havard, and D. P.Reynolds, J.C.S. Chem. Comm., 1973.266140 J.C.S. Perkin Iatom, 0(7), attached to 0 ( 5 ) , and the occupationfractions of O(4) and O(7) were allowed to vary. Re-finement converged to R 0.056 (anisotropic temperaturefactors were used).The occupation fractions of O(4)and O(7) had a sum of unity within one standarddeviation, thus confirming the model of co-crystallisedstereoisomers. Bond-length and -angle calculationsshowed no contact distances to O(7) less than 3.0 A, thesum of the van der Waals radii: this indicates that thecrystal structure of the 2-isomer contains enough spaceFIGURE 3 Molecular packing; view perpendicular to the caxisto accommodate the additional atom Q(7) of the E-isomer without distortion of the close-packing of themolecules. The crystal structure thus consists of the2-isomer shown in Figure 1 with 17 amp; 5 of E-isomerin the lattice.Whether the observed isomer ratio in the crystal isrepresentative of the total reaction product is uncertain.It is also uncertain whether the mixture reflects kineticor thermodynamic control, though the latter seemsprobable (2 h reflux in benzene).Proton n.m.r. does notadequately differentiate between the 2- and E-isomers,there being insufficient perturbation to alter the chemicalshifts of the aromatic protons, and a lH solution studyof the isomerisation could not be undertaken.0FIGURE 4 Bond length (A) ; e.s.d.s 0.01 unless otherwiseindicated in parenthesesThe arrangement of molecules in the unit cell isshown in Figure 3 which confirms the availability ofspace within the crystal structure to accommodate theadditional atom of the E-isomer without distortion.Bond lengths and angles are displayed in Figures 4and 5; these adopt expected values if allowance is madefor the larger uncertainties in those positions which arefractionally occupied. The benzene ring is planarwithin 0.03 A (x2 13.93) as are also both the five-membered rings, with x2 = 1.03 for the cyclic acetalring and x2 = 3.77 for the trione ring.As expected, thebenzene and acetal rings are coplanar: however, thecentral section of the molecule C(l),C(2) ,C(9) is dis-torted out of conjugation, presumably to avoid closecontact of O(3) and C(3). The torsion angle about theC(l)-C(2) bond is 33", and, surprisingly, the C(l)-C(9)double bond has a torsion angle of 11". The resultingtwist in the molecule allows the 0(3)-C(3) contactdistance to expand to 2.41 A and the Cl-0(6) contactdistance is 2.89 A. Short intermolecular carbon 10(3)-C(12'), 2.99 A; 0(4)-C(8'), 3.00 A; O(6)-C(lO'),2.84 A; Q(6)-C(ll'), 2.95 A; 0(7)-C(8'), 2.99 A.Treatment of the red trione (2) in ethyl acetate withan excess of water led to the acid (5; R = H), but with1 mol.equiv. of water the tetraone, C,,H,O, (7) couldbe isolated in 70 yield. The mass spectrum (Scheme 1)contacts were observed as follows: 0(3)-C(9'), 2.93 K ;Cl 0FIGURE 5 Bond angles { O ) ; e.s.d.s 1" unless otherwiseindicated in parenthesessupported the structure, and U.V. data A,, (CHC1,)250 ( E 7510), 292 (6820), 332 (6180), and 408 nm(13 300) suggested that it is largely enolised, as in (8)1977 141in this solvent. Treatment of (8) with water or sodiumhydroxide solution gave the acid (5; R = H), and( 7 ) C,, H 60Jt1 +c@0 qL OSCHEME 1treatment with ethanol gave the ester (5; R = Et), bycleavage of the anhydride and decarboxylation of (9;R = Et).Addition of an excess of ethanol to the red trione (2)itself, in the absence of organic diluent, resulted in anexothermic reaction with evolution of carbon dioxide.If, after effervescence had ceased, water was added, theester (5; R = Et) was obtained.However, if themixture was set aside, two further products, (10) and( l l ) , could be isolated from the acidic solution. Then.m.r. spectrum of (10) showed signals for three ethylgroups (two equivalent), a methylene singlet, and themethylene singlet and three aromatic protons of themethylenedioxyphenyl group. Comparison of U.V.datashowed a chromophore closely similar to that of 3,4-methylenedioxyacetophenone, but substantially differentfrom models for the 4-monoacetal chromophore, e.g. thelignan asarinin. Assignment of structure (10) is alsosupported by the mass spectral data (Scheme 2).The n.m.r. spectrum of the second product showedsignals for two ethyl groups, an olefinic proton, and themethylenedioxyphenyl group: this led to the enol etherstructure (1 1). Its stereochemistry was explored asfollows. Treatment of (5; R r= Et) with diazomethanein the presence of a catalytic quantity of boron tri-fluoride gave (12), showing T 3.16 for the olefinic 3-proton. On treatment with trifluoroacetic acid, thisisomer underwent stereomutation to give (13), T 3.82;the upfield shift suggests that the methoxycarbonylgroup is in this case trans to the olefinic proton.2 Thisgeometry was confirmed when a 21 enhancement ofthe H-3 signal was observed on irradiation at T 6.18L.H. Jackman and S. Sternhell, 'Applications of NylearMagnetic Resonance Spectroscopy in Organic Chemistry, 2ndedn., Pergamon, Oxford, 1969.(OMe). Since H-3 in (11) resonates at 3.88 thecompound is the E-isomer. L4ssignment of the 2-alkoxy-structures (11)-(13) as opposed to the 4- (14) issupported by U.V. data. Since an alkoxy-group pro-duces a shift of ca. 30 nm when substituted in thep-position of an =-unsaturated k e t ~ n e , ~ the principalabsorption of (14) would be expected to be at longerwavelength than that of 3,4-me t h ylenediox ycinnamicester (15).Compounds (1 1)-( 13) absorb a t shorterwavelengths (though longer than that of 3',4'-methylene-dioxyacetophenone) .N.m.r. data show that, in the solvents examined, noneof the compounds of type (5) actually exhibits reson-ances attributable to the dioxo-form: all appear entirelyenolised, with the chelated proton signal near 7 -5.Since the U.V. spectra show maxima at longer wave-lengths than that of the corresponding cinnamic acid(15), the predominant tautomer appears to be (16).Following this examination of the chemistry of thered trione (2), the reactions of a series of substitutedarylpropiolic acids with oxalyl chloride were studied,to assess the scope of the synthesis. The results aresummarised in Table 1: yields refer to the amounts ofpure compounds isolated by crystallisation or distillation.noq!I M+ 3 3 8m*207.8J I +0 O E t+on+J T o2 9 3 .7 - 0L Obsol;m*154.0 /SCHEME 2In the cases (a)-(d), the i.r. spectra of the crudeproducts showed absorptions at 2 200 cm-l assigned toA. I. Scott, ' Interpretation of the Ultraviolet Spectra ofNatural Products,' Pergamon, Oxford, 1964142 J.C.S. Perkin IC Z stretching of the corresponding acid chlorides (18),which are minor products. For case (a) quantitativei.r. estimation showed the presence of 92 of thetrione (19) and 8 of the acid chloride (18) ; amounts for(b)-(d) are expected to be similar. The ratio of (19)to (18) remained unchanged on prolonged refluxing, andboth pure compounds were unchanged by refluxing withoxalyl chloride in benzene: the two are produced incompeting pathways, neither being an intermediate inthe formation of the other.TABLE 1Reaction of arylpropiolic acids (17) with oxalyl chlorideProduct isolated ()R1a Hb HC Hd He OMef Hh Hg HRa Ra--J O*CHg*OOMe OMeOMe OMeH OMeH HH MeH HH c1R4 lsquo; (19) (18) (20)rsquo;H 75OMe 70H 76H 73H 41 6H 44 16H 41 40H 36 62(17) X = O H(18) X = C l(20)All the triones (19) exhibit deep red solutions showingstrong absorption (E 12000-~00oO) in the 420-480nm region, and their i.r. spectra are very similar in thecarbonyl region.The mass spectral fragmentationpatterns all follow that summarised in Scheme 3.*Arylnaphthdenes (ZO), all identical with authenticspecimens: were important products in reactions(e)-(h). These arise from the corresponding acetylenicacid anhydrides5 which, along with the acid chlorides,are well known products from oxalyl chloride andcarboxylic acids6 However in none of these reactionsdid a red colour develop, indicative of trione formation,with the exception of (e), and here no trione was isolated.* This contrasts with the mass spectrum of the thermal re-arrangement products (following paper), which fragment by directdecomposition of M+ to ArCGO.Minor peaks corresponding tothe latter were observed even under conditions of strict exclusionof moisture to avoid contamination by (8): this tends to implysome isomerisation in the mass spectrometer.Formation of the triones must involve nucleophilicdisplacement by C-2 of the acetylene in the mixedCI n l :Arolsquo;N - 2 8 M-44 -coy*ArRbase peakSCHEME 3anhydride see (21).In the transition state for thecyclisation the aromatic ring is envisaged as beingorthogonal to the forming trione ring. Overlap of thearomatic orbitals with the shaded orbitals of the re-hybridising acetylene (Figure 6) implies that theelectronic effect of substituents in the aromatic ring is ofcardinal importance in stabilising the developing positivecharge at C-3; carbonyl overlap with the unshadedorbitals has little influence. Thus only examples(a)-(d) in Table 1, all of which possess a $-alkoxy-group gave chlorotriones. When suitable electronrelease is not available, i.e.(e)-(h), the reaction takesanother course leading to arylnaphthalenes and acidFIGURE 6chlorides. Other aspects of the mechanism are dis-cussed with the mechanism of the thermal rearrange-ment of the chloro-triones in the following paper.(a) F. G. Baddar, J . Chem. SOC., 1947,224; (b) F. G. Baddarand L. S. El-Assal, ibid., 1848, 1267; (c) 1961, 1844; ( d ) F. G.Baddar, L. S. El-Assal, and N. A. Doss, ibid., 1956, 465; (e) 1969,1027; (f) F. G. Baddar. G. E. M. Moussa, and M. T. Omar, J .Chem. SOC. ( C ) , 1968, 110.J. Cleyand J. F. Arens, Rec. Trav. chim., 1959,78, 929.R. Adams and L. H. Ulich, J . Amer. Chem. Soc., 1920, 42,6991977 143EXPERIMENTALa-Chloro-3,4-methylenedioxybenzylidenetetrahydro fuian-2,4,5-trione (2) .-Oxalyl chloride (10 g, 80 mmol) was addedto a finely ground suspension of 3,4-methylenedioxyphenyl-propiolic acid (5.7 g, 30 mmol) in anhydrous benzene(10 cm3).The mixture was refluxed for 2 h. Benzeneand the excess of oxalyl chloride were removed underreduced pressure, and the residue crystallised from an-hydrous benzene to give the tetrahydrofurantrione (2) (6.2 g,75), red plates, m.p. 170-172' (decomp.) (Found: C,requires C, 51.3; H, 1.8; C1, 12.65; M , 279.977),vmx (CHCl,) 1869, 1838, 1788, and 1723 cm-l, Lx274sh (E 7 020), 288 (8 200), 364 ( 5 300), 425sh (8 700), and473 nm (13 000), T (CD,),CO 2.45 (1 H, dd, J5.6 8, J z S s2 Hz, arom. H-6), 2.70 (1 H , d, J2.6 2 Hz, arom. H-2), 2.95(1 H , d, J 5 .6 8 Hz, arom. H-5), and 3.78 (2 H, s, CH,O,).Reactions of the Trione (2) with Water and Alcohols.-(a) With aqueous sodium hydroxide. The trione (2) (0.5 g)was shaken with aqueous sodium hydroxide (5; 10 cm3).When the red colour had been discharged (a few minutes),the solution was acidified with hydrochloric acid. Theprecipitate, on crystallisation from aqueous ethanol, gavepale yellow crystals of 3,4-methylenedioxybenzoyl~yruvic acid(16; R = H) (348 mg, 83), m.p. 197-199' (decomp.)(Found: C, 55.7; H, 3.35; M+, 236. CllH8O6 requiresC, 56.0; H, 3.4; M , 236), v,, (mull) 3 200-2 400(carboxylic acid), 1730 and 1723 (carbonyl), and 1633cm-l (enolic P-diketone), vmx. (EtOH) 352 (E 15 000),306infl (8 loo), and 244 nm (7 300), T (CD,),SO -1.0551.3; H, 1.8; c1, 12.6; M+, 279.977. Cl2H5C1O6(2 H , s ) , 2.23 (1 H, dd, J5.6 8, J 2 .6 2 Hz, H-6), 2.45 (1 H ,d, J 2 , 6 2 Hz, H-2), 2.92 (1 H, d, J 8 Hz, H-5), 2.93 (1 H, S,olefinic), and 3.78 (2 H , s, CH,O,). An ethanolic solutiongave a red colour with iron(II1) chloride.(b) With a n excess of water. The trione (2) (533 mg)was refluxed with ethyl acetate (10 cm3) and water (1 cm3)for 1.5 h. Evaporation, and crystallisation from aqueousethanol, yielded 3,4-methylenedioxybenzoylpyruvic acid(16; R = H) (236 mg, 54), m.p. 196-198' (decomp.).(c) With 1 mol. equiv. of water. A solution of water inethyl acetate (19.976 g 1F; 3 cm3) was added to a hotsolution of the trione (2) (932 mg) in anhydrous ethylacetate ( 7 cm3).On cooling the solution deposited yellowneedles of a-hydroxy- 3,4-methylenedioxybenzylidenetetrahydro-furan-2,4,5-trione (8) (621 mg, 71), m.p. 179' (decomp.),not raised by crystallisation (ethyl acetate) (Found: C,54.7: H, 2.45; M+, 262. Cl2H6O, requires C, 54.95; H,2.3: M, 262), vmaL (CHCI,) 1 850, 1 780, and 1 695 cm-1,Amx. (CHCl,) 250 (E 7 510), 292 (6 820), 332 (6 180), and408 nm (13 300), T (CD,),CO 2.15 (1 H , dd, J5,6 8, J2.62 Hz, arom. H-6), 2.43 (1 H, d, J2.6 2 Hz, arom. H-2), 2.97(1 H, d, J5,6 8 Hz, arom. H-5), and 3.81 (2 H, s, CH,O,).The trione (2) (710 mg) inanhydrous chloroform (300 cm3) was treated with ethanol(500 mg) and kept for 60 h. The solution was evaporatedand the residue crystallised from aqueous ethanol to giveethyl 3,4-methyZenedioxybenzoyl~yruvate (16; R = Et) (5 11mg, 65) as pale yellow microcrystals, m.p.70-71'(Found: C, 59.0; H, 4.5; M+, 264. Cl3Hl2O6 requires(chelated OH), 1 758, 1 738, and 1 045 cm-1, A,,, (EtOH)248 (E 6 640), 309 (7 890), and 360 nm (14 700), T (CCl,)-4.7br (1 H, s, chelated OH), 2.43 (1 H, dd, J5.6 8, J2,6olefinic), 3.20 (1 H, d, J5,6 8 Hz, H-5), 3.95 (2 H, s, CH202),(d) With a n excess of ethanol.C, 59.1; H, 4.55; M, 264), vmax (CCl,) 3 200-2 5002 Hz, H-6), 2-62 (1 H, d, 1 2 . 6 2 Hz, H-2), 3.16 (1 H , S,5.68 (2 H, q, J 7 Hz), and 8.60 (3 H , t, J 7 Hz). Anethanolic solution gave a red colour with iron(II1) chloride.Prior to evaporation the mixture was analysed by g.1.c.(column 5 f t by t in of 10 squalane on Celite) in order todetermine whether ethyl chloride was a product.Sensi-tivity was adequate to detect a less than 1 yo yield, but nonewas observed.A solution of ethanolin chloroform (45.9 g 1-1; 0.85 cm3) was added to the trione(2) (237 mg) in anhydrous chloroform (100 cmS). After60 h g.1.c. showed no ethyl chloride. Evaporation andcrystallisation from anhydrous ethyl acetate gave a-hydroxy-3,4-methylenedioxybenzylidenetetrahydrofuran-2,4,5-trione (8) (79 mg, 36), m.p. 178-179' (decomp.).(f) With ethanol in the absence of a n inert solvent. (i) Withquenching after a short period. Anhydrous ethanol (0.6cm3) was added in one portion to the trione (2). After aninduction period (minutes) an exothermic reaction began,and the red compound dissolved with effervescence.Assoon as dissolution was complete, water (10 cm3) was added.The precipitated oil solidified ; crystallisation from aqueousethanol gave ethyl 3,4-methylenedioxybenzoylpyruvate(16; R = Et) (154 mg, 80), m.p. 71-72'.Anhydrous ethanol (10 cm3)was added to the trione (2), and the resulting solution keptfor 24 h. The mixture was separated by p.1.c. on silicawith benzene-ethyl acetate (7 : 1) as eluant. Three bandsformed and were extracted with ethyl acetate. That ofhighest RF gave the enol ethyl ether of ethyl 3,4-methylene-dioxybenzoylpyruvate (1 1) (69 mg), needles (benzene), m.p.128-130" (Found: C, 61.7; H, 5.5; M+, 292. C15H1,06requires C, 61.65; H, 5.5; M , 292), vmx. (CHCl,) 1735(a@-unsaturated ester), 1 655 (aryl and ap-unsaturatedketone), 1 604, and 1 582 cm-1, (EtOH) 238 (E 13 400),280 (11 800), and 322 nm (12 050), T (CDCl,) 2.50 (1 H, dd,(e) With 1 mol.equiv. of ethanol.(ii) Over a prolonged period.J5.6 8, J2.6 2 Hz, H-6), 2.59 (1 H , d, J2,6 2 Hz, H-2), 3.20(1 H, d, J5.6 8 Hz, H-5), 4.01 (2 H , S, CH202), 3.88 (1 H, S,olefinic), 5.68 (2 H , q, J 7 Hz), 5.97 (2 H, q, J 7 Hz), 8.58(3 H , t, J 7 Hz), and 8.70 (3 H , t , J 7 Hz). The band ofintermediate Rp gave the diethyZ acetal of ethyZ 3,4-methyZene-dioxybenzoylpyruvate (10) (715 mg), blades, m.p. 89-90'(aqueous ethanol) (Found: C, 60.7; H, 6.6; M+, 338.C,,H,,O, requires C, 60.35; H , 6.55 ; M , 338), vmx. (mull)1750 (ester) and 1660 cm-1 (aryl ketone), (EtOH)231 (E 17 800), 275 (7 050), and 310 nm (8 320), T (CDCl,)2.43 (1 H, dd, J5.6 8, J2.6 2 Hz, H-6), 2.58 (1 H, d, J2.6 2 Hz,H-2), 3.17 (1 H, d, J5.6 8 Hz, H-5), 3.96 (2 H, S, CH,O,),6.38 (2 H, s, CH,), 5.75 (2 H, q, J 7 Hz), 8.73 (3 H, t,J 7 Hz), 6.45 (4 H , q, J 7 Hz), and 8.81 (6 H, t, J 7 Hz).The band of lowest RF gave ethyl 3,4-methylenedioxy-benzoylpyruvate (16; R = Et) (242 mg), m.p.70-72'(from ethanol).Reactions of a-Hydroxy- 3,4-methylenedioxybenzylidsnetetra-hydrofuran-2,4,5-trione (8) with Water and Alcohols.-(a) With aqueous sodium hydroxide. Aqueous sodiumhydroxide ( 5 ; 2 cm3) was added to the hydroxy-trione(8) (92 mg). When effervescence had ceased the solutionwas acidified. The precipitate crystallised from aqueousethanol to give 3,4-methylenedioxybenzoylpyruvic acid(16; R = H) (69 mg, 84), m.p.197-198' (decomp.).(b) With water. The hydroxy-trione (8) (169 mg), water(0.5 cm3), and ethyl acetate (4 cm3) were refluxed for 1 h.Evaporation and crystallisation from aqueous ethanolyielded 3,4-methylenedioxybenzoylpyruvic acid ( 16; R =H) (135 mg, 88), m.p. 197-198'144 J.C.S. Perkin I(c) With ethanol. The hydroxy-trione (9) (202 mg) waswarmed with ethanol (0.5 cm3) until effervescence hadceased and dissolution had taken place. On cooling, ethyl3,4-methylenedioxybenzoylpyruvate ( 165 mg, 8 1 ) crystal-lised; m.p. 71-72'.Enol Methyl Ethers of Ethyl 3,4-MethyZenedioxybenzoyl-pyruvate. -Ethyl 3,4-met hylenedioxybenzo ylpyruvate (2 64mg, 1 mmol) in ether (10 cm3) was treated with boron tri-fluoride-ether (0.06 cm3, 0.05 mmol) and an excess ofethereal diazomethane.After 20 h the solution waswashed with aqueous sodium hydrogen carbonate, thenwater, dried (MgSO,), and evaporated. The predominantproduct (12) was separated from contaminating E-isomerand starting material (both of lower R p ) by p.1.c. on silica,with benzene-ethyl acetate (9 : 1) as eluant. Moleculardistillation (60 "C; 0.1 mmHg) gave the (2)-enol methylether of ethyl 3,4-methylenedioxybenzoyl~yruvate ( 12) (143mg) as an oil (Found: C, 60.55; H, 5.0; M+, 278.Camp;amp;6 requires C, 60.54; H, 5.05 ; M , 278), vmaK (CHCl,)1 725 (ap-unsaturated ester), 1 656 (aryl, ap-unsaturatedketone), 1620sh, 1608, and 1590 cm-l, Amx. (EtOH) 239(z 13 300), 281 (10 SOO), and 324 nm (11 300), 7 (CDC1,)2.50 ( I H, dd, J 5 .6 8, J 2 . 6 2 Hz, H-6), 2.63 (1 H, d, J2.6 2 Hz,H-2),'3.22 (1 H, d, J 5 , 6 8 Hz, H-5), 4.0 (2 H, S , CHZO,),3.16 (1 H, s, olefinic), 6.23 (3 H, s, OCH,), 5.70 (2 H, q,J 7 Hz), and 8.65 (3 H, t, J 7 Hz).Trifluoroacetic acid (0.5 cm3) was added to a solution ofthe Z-isomer (12) (140 mg) in chloroform (5 cm3). After10 min, the solution was evaporated, and the residuecrystallised from benzene-hexane to give needles of theE-isomer (13) (96 mg), m.p. 132-133' (Found: C, 59.9;H, 5.2; Mf, 278), v,,, (CHC1,) 1733 (aP-unsaturatedester),. 1 656 (aryl, aP-unsaturated ketone), 1 605, and1583 cm-l, Lx. (EtOH) 238 (E 13 600), 281 (11 400), and323 nm (12 loo), T (CDC1,) 2.49 (1 H, dd, J5,6 8, J2,6 2 Hz,H-6), 3.99 (2 H, s, CH202), 3.82 (1 H, s, olefinic), 6.18 (3 H,s, OCH,), 5.67 (2 H, q, J 7 Hz), and 8.70 (3 H, t, J 7 Hz).A 10 solution in CDCl, was degassed by five freeze-pump-thaw cycles, and tetramethylsilane was added forfield frequency locking.With irradiation a t T 6.17 (OMe)the olefinic signal at T 3.82 showed 21 greater integratedintensity than observed with the irradiating field offset to7 6.5.Arylpropiolic A cids.-The acids (1 7 s - c ) and (1 7f) wereprepared from the corresponding cinnamic acids, byesterification followed by bromination and dehydrobromin-ation. The cinnamic acids were made by Doebner con-densation. The acids (17d) and (17g and h) were preparedfrom the appropriately substituted benzoic acids by theWittig method.'Reactions of Oxalyl Chloride with Arylpropiolic Acids.-The arylpropiolic acid in anhydrous benzene was refluxedwith an excess of oxalyl chloride (2-3 mol.equiv.) and,after evaporation, the crude product was purified (seebelow). Products and their solutions are moisture sensitive ;exposure to the atmosphere was kept to a minimum, and allthe solvents were anhydrous.In reactions with the acids (17a-d) crystallisationgave coloured aryl(chloro)methylenetetrahydrofuran~2,4,5-triones (19a-d). With (17f and g) the crude product wasa yellow solid suspended in an oil. The solid was filteredoff and washed with a little benzene to give the naphthalene-' G. Markl, Chsm. Bey., 1961, 94, 3005; s. T. D. Gough andS.Tripett, J. Chem. SOC., 1962, 2333.H-6), 2.60 ( 1 H, d, J2.6 2 Hz, H-2), 3.18 ( 1 H, d, J 5 , g 8 Hz,dicarboxylic anhydride (20f or g). Evaporation of thefiltrate and distillation gave the arylpropiolyl chloride(18f or g). For (lh), sublimation at 55 'C and 0.2 mmHggave the acid chloride (18h) and crystallisation of theinvolatile residue afforded the naphthalenedicarboxylicanhydride (20h).Unlike reactions with (17f and g), with (17e) the reactionmixture developed a red colour but no aryl(ch1oro)-methylenetetrahydrofurantrione (1 9e) was isolated. Sub-limation (75 "C and 0.1 mmHg) of the crude productyielded the acid chloride (18e), and crystallisation of theinvolatile residue gave the naphthalene (1 9e).The naphthalenedicarboxylic anhydrides (20e-h) wereidentical (mixed m.p.and i.r. spectrum) with authenticsamples .4 The arylpropiolyl chlorides ( 18e-h) wereidentical (i.r. spectrum) with samples prepared by theaction of thionyl chloride on the corresponding acids.Products and yields are summarised in Table 1. Propertiesof compounds (18)-(20) are given in Table 2..For the reaction involving 3,4-methylenedioxyphenyl-propiolic acid (17a), the ratio of (19a) to (18a) was estimatedfrom the absorbances of the i.r. bands at 2 200 and 1 790cm-1, by using a calibration graph.Crystallographic Analysis of a-Chloro-3,4-methylenedioxy-benzylidenetetrahydro furan-2,4,5-trione (2) .-Suitable speci-mens of the trione were grown from ethyl acetate solution.Oscillation and Weisenberg photographs were taken aboutthe a axis to establish approximate unit cell dimensionsand space group.For intensity measurement, a crystal ofdimensions ca. 0.6 x 0.3 x 0.05 mm was mounted,aboutthe a axis on a Hilger and Watts linear diffractometer.Unit-cell dimensions were refined on the diffractometer.With Mo-K, radiation, intensity data were collected on thelevels 0-7kl by the moving-crystal stationary-counter scanmethod. Each reflection was measured twice and themean taken in data reduction. Reflections with a mean netcount 31s were considered unobserved, leaving 664observed reflections which were used in the subsequentrefinement. No absorption corrections were made. Datareduction and subsequent crystallographic calculations wereperformed by using the National Research Council (Ottawa)programs of Ahmed, Hall, Pippy, and Saunders.Atomicscattering factors were taken from ref. 8.Crystal data. C12H,C106, M = 280.6. Orthorhombic,a = 7.95 f 0.02, b = 23.87 f 0.04, c = 11.93 f 0.02 A,U = 2 255.4 Hi3, 2 = 8, D, = 1.65 g cm-,, F(000) = 1 136.Space group Pbca uniquely from systematic absences.Mo-K, radiation, h = 0.710 69 A, p(Mo-K,) = 3.67 cm-l.Structure solution and refinement. The atomic co-ordinates of the chlorine atom were found from a Pattersonsynthesis using the observed intensity data, sharpened by1/Lp corrections. A three-dimensional Fourier summationphased on the chlorine atom enabled a further 9 atoms to belocated. After a structure-factor calculation with the newmodel, a second Fourier synthesis revealed the positions ofall the non-hydrogen atoms.Initially five cycles of block-diagonal least-squaresrefinement of atomic positions and isotropic temperaturefactors were carried out with all the data and unit weight.After the fifth cycle the value of the agreement factor R was0.15.Analysis of the agreement between F, and F,,indicated a slight rescaling of the data between the reciprocallattice levels 0-7kl. A weighting scheme was also adopted* ' International Tables for X-Ray Crystallography,' vol. 111,Kynoch Press, Birmingham, 19621977 145of the form w = 1 for IFo 30.0 and w = (30.0/lF01)2 forlFol 30.0. Two further cycles of refinement were thencarried out, after which the atomic temperature factorswere allowed to vary anisotropically.Three more cyclesreduced the value of R to 0.077.A difference synthesis was then calculated whose mainfeature was the presence of a peak within bonding distanceTABLE 2(a) Data for triones (19)Reflux Cryst.R2 R3 R4 time solvent Form M.p. ("C)(19b) OMe OMe OMe 2 h PhH Orange 162- 154needles (decornp.)(19c) OMe OMe H 2.5h PhMe Brown. 158-160needles (decornp.)(19d) OMe H H 10min PhH- Orange 138-139C6H14 needles (decornp.)Found (yo) Required (yo)r-- bsol; -7 C H C1 Formula C H C1(19b) 51.4 3.5 10.65 C,,HllC1O, 51.45 3.4 10.9 1;s) 53.95 2.75 13.2 C,,H,ClO, 54.1 2.6 13.3Xmax.(CHC1,)/nm (4(19b) 298 (7 710), 464 (12 500)(19c) 293 (8 030), 381 (5 880), 430 (9 600), 477 (15 100)(19d) 264sh (6 410), 287 (8 930), 422 (19 900).434sh (17 700)v,,./cm'-l (carbonyl region)(19b) 1 870, 1 830, 1 786, 1 723(19c) 1 870, 1 845, 1 786, 1 720(19d) 1861, 1788, 17257 (CDJWI(19b)52.65 3.15 11.65 C13H,C106 52.6 3.05 11.95z 2.78 (2 H, s, H-2 and -6), 6.08 (3 H, s, 4-0Me), and 6.13(6 H, s, 3- and 5-OMe)(1) T 2.34 (1 H, dd. J 5 . 6 8, J2.6 2 Hz, H-6). 2.51 (1 H, d,Jz.6 2 Hz, H-2), 2.82 (1 H, d, J5.6 8 Hz, H-5), 6.00 (3 H,s, OMe), and 6.14 (3 H, s, OMe)z cu. 2.05 and cu. 2.85 (4 H, AB, multiplet, symmetricalabout z 2.47, H-2, -3, -4, and -6), and 6.03 (3 H, s, OMe)(19d)(b) Data for arylnaphthalenes and arylpropiolyl chloridesRL R3 Products M.p. or b.p. ("C) Lit. m.p. ("C) Ref.91-93 93-94 4c247-249 254-246 4aOMe H (184OMe H (20e)H Me (18f) 80 a t 0.2 mmHgH H (18g) 46 at 0.1 mmHgH C1 (18h) 65-67 68-69 4sH C1 266-267 266-267 4eH Me (20f) 272-273 268-269 4dH H 258-259 255-256 4bof O(5).This corresponded to the presence of a minoramount of the E-isomer of the trione which had co-crystallised. In confirmation the difference map alsoshowed a large depression in the neighbourhood of O(4).The difference map also revealed the approximate positionsof all the hydrogen atoms. The additional atom wasdesignated O(7) and included in the structure factorcalculation. The temperature factor for O(4) reverted tobeing isotropic and O(4) and O(7) were included in thecalculations with isotropic temperature factors, and theiroccupation fractions were also refined.Five further cyclesof least-squares refinement were carried out to allow therefined occupation fractions of these two atoms to settledown, which reduced R to 0.065. The positions of thehydrogen atoms were calculated accurately from bondlength and angle considerations and found to correspondapproximately to their peaks in the difference map. Threefinal rounds of least-squares refinement, including thehydrogen atoms but without refinement, and allowing O(4)and O(7) to vibrate anisotropically, reduced the agreementfactor R to 0.056 after a total of 18 cycles, the largestparameter shifts being of the order 0.40, indicating that therefinement had converged. The accuracy of the structurewas confirmed by computing a final difference map whichshowed no peaks or depressions 0.3 eA-3. Final atomicco-ordinates are listed in Table 3 together with theirTABLE 3Fractional atomic co-ordinates with e.s.d.s in parenthesesxla0.594 8(4)0.321 4(10)0.270 5( 11)0.360 4(8)0.411 2(15)0.562 9( 10)0.681 4(9)0.525 l(10)0.469 9(10)0.501 l(11)0.451 9(13)0.381 2(13)0.352 2(12)0.398 7( 12)0.249 l(17)0.527 6(10)0.440 2( 10)0.473 4( 12)0.602 3(11)0.641 7(52)0.5660.4670.3830.3140.118Y lb0.375 O( 1)0.515 6(3)0.530 9(3)0.272 8(3)0.156 O(5)0.194 4(3)0.257 3(3)0.350 3(4)0.391 4(4)0.382 4(4)0.422 O(4)0.470 4(4)0.478 7(4)0.442 l(4)0.554 4(5)0.292 7(4)0.260 3(4)0.250 O(5)0.156 5(15)0.3440.4150.4510.5950.5610.201 7(4)standard deviations. Temperature factorszlc-0.024 l(2)0.398 l(6)0.206 3(6)0.285 3(6)0.215 7(9)0.078 5(6)0.102 5(7)0.181 O(6)0.298 2(7)0.376 3(8)0.336 7(7)0.223 5(7)0.144 4(7)0.320 2(9)0.116 4(7)0.205 5(7)0.174 7(8)0.038 3(7)0.052 l(29)0.3260.4650.0560.3270.340-0.045 4(5)and observedand calculated structure factors are listed in SupplementaryPublication No. SUP 21879 (16 pp., 1 microfiche).t Thefinal values for the occupation fractions of O(4) and O(7)were 0.85(2) and 0.19(2), respectively. These add up tounity, within one standard deviation, and were taken toindicate the presence of 17 f 5 of the minor E-isomer co-crystallised with the major 2-isomer of the trione (2).We acknowledge the support of the S.R.C.6/S63 Received, 6th May, 19763t For details of Supplementary Publications see Notice toAuthors No. 7 in J.C.S. Perkin I, 1975, Index issue