622 J.C.S. Perkin Iv-Triazolines. Part V.l Rearrangement of Triazolines from Cyclopropyl-enamines and Toluene-p-sulphonyl AzideBy Donato Pocar * and Pasqualina Trimarco, lstituto di Chimica Organica della Facolt3 di Farmacia, UniversitbThe reactions of tosyl azide with enamines bearing a cyclopropyl group in the a-position (1) afford, via unstabletriazolines (2), zwitterionic intermediates (3) which can lead (i) through C-C cleavage to diazo-compounds (6)and amidines (5) and (ii) through nitrogen loss and rearrangement to amidines (7).di Milano, Viale Abruzzi 42, 201 31 Milano, ItalyDURING our work on the reactions of arenesulphonylazides with enaminesZv9 evidence has been foundshowing that unstable 5-amino-v-triazoline intermediates(2) are formed which react according to the paths (i)and/or (ii).Path (i) is followed where R1 = R2 = H,3s4y7and where R1, R2, and R3 are alkyl the rearrangementreaction is preferred.2s4s5,8 We now report the corre-sponding reactions of enamines bearing a cyclopropylgroup in the a-position. The possibility of interactionof the cyclopropyl group with a carbocation centre atthe p-position and its great ability to migrate are welldocumented.1deg; We were also interested in examiningthe influence of P-substituents on the course of reaction.equilibrium mixture with its tautomer. The amidines@a, b, and f ) and (7a-f) formed are listed in Table 1,along with the ratio in which they were formed and theirTABLE 1Reactions of enamines (1) with tosyl azideAmidines Ratio YieldEnamine produced (6) : (7) ( 5 ) + (7)111(W(Id)(W (El(Eia) and (7a) 75: 25 80(5a) and (7c) 25: 75 91(5a) and (7d) 10: 90 82(5a) and (7e) 60 : 40 90ki ( E : 2 7 : 3) (5b) and (7b) 30 : 70 7450 (If) (E : 2 6 : 4) (5f) and (7f) 40 : 60overall yields.The formation in appropriate cases ofthe diazo-compound was inferred from the isolation ofthe corresponding amidine (5) path (i); and no effortwas made to isolate it. The structures of all amidinesThe reactions between the enamines (la-f) andtosyl azide were performed at room temperature inbenzene solution. All the enamines have the cyclo-propylvinyl structure and their configurations are asindicated in Table 1. The enamine (If) was used as the1 Part IV, R. Stradi, D.Pocar, and G. Bianchetti, Org. Mag-a R. Fusco, G. Bianchetti, and D. Pocar, Gaxzetta, 1961,91,933.R. Fusco, G. Bianchetti, D. Pocar, and R. Ugo, Chem. BBY.,4 G. Bianchetti, D. Pocar, P. Dalla Croce, and A. Vigevani,G. Bianchetti, P. Dalla Croce, and D. Pocar, Ist. Lomb. Acc.6 G. Bianchetti, D. Pocar, and P. Dalla Croce, 1st. Lomb. Acc.netic Resonance, 1972, 4, 247.1963, 96, 802.Chem. Ber., 1965, 98, 2716.Sci. Lett., 1965, A99, 259.Sci. Lett., 1966, A99, 316; Gazetta, 1965, 95, 1220.P. Ferruti, n. Pocar, and G. Bianchetti, Gazzetta, 1967, 97,110. * D. Pocar, G. Bianchetti, and P. Ferruti, Gazzetta, 1967, 97,697; P. Dalla Croce and R. Stradi, 1st. Lomb. Acc. Sci. Lett.,1967, A101, 692.8 P. Dalla Croce, D. Pocar, and R. Stradi, 1st.Lomb. Acc. Sci.Lett., 1967, A101, 680.lo For a review, see J. Haywood-Farmer, Chem. Rev., 1974,74, 315.l1 D. Pocar, R. Stradi, and P. Trimarco, Tetrahedron, 1978,31, 24271976 623were assigned on the basis of their lH n.m.r. spectra(solvent C,D,).R', / R3'c=c; I ArS02N3 + R2'NR 2I R? R! R?(71R'HHMeHHI.!3-J21r.R2HMeMe 1 N Ramp;n2NEt2n MuoThe results show that both paths (i) and (ii) areoperative at the same time. This behaviour has beenCompd. M.p. ("C)( 5 4 156-15879-81(Oil)(Oil)116(Oil)( 7f) 156(5b)(5f)( 7 4(7b)( 7 4( 7 4( 7 476-78137-139Required values in parentheses.standard).(7).* A possible explanation is related to the ability ofalkyl substituents to stabilize the carbocation (4), thusmaking path (ii) easier.Mechanism (ii) is a generalpathway for the reactions of azides bearing stronglyelectron-withdrawing substituents l2 with strained orunstrained olefins and vinyl ethers.13 In the particularcase of enamines, path (i) becomes important probablybecause cleavage of the C-C bond to give the diazo-compound can be assisted by the amino-substituent.However, it seems that the basicity of the amine residuehas little influence on ratio of the products (5) and (7).14Finallv, the presence of the a-cyclopropyl group doesnot affect particularly the pathway of the reaction withtosyl azide. Also, the migratory aptitude of the cyclo-propyl group in our systems is similar to that of thecyclohexyl group enamine (If) and that of the isopropylEXPERIMENTALEnarPzines.--The enamines (la, b, d, and e) were preparedas previously described; l1 (lc) was obtained by the sameprocedure from cyclopropyl isopropyl ketone l5 as a liquid,b.p.85 "C at 4 Torr (yield 50). The enamine (If) wasprepared according to the same method from cyclohexylethyl ketone, morpholine, and titanium tetrachloride inlight petroleum as a liquid, b.p. 95-97 "C a t 0.3 Torr(yield 50). Compound (If) is obtained along with itstautomer, 1-cyclohexylidene-l-morpholinopropane, as theequilibrium mixture which, according to its lH n.m.r.spectrum (solvent C,D,) contains about 70 of ( I f ) .Reactions with TosyE Azide.-A solution (cn. 10) of theenamine in anhydrous benzene at room temperature wastreated dropwise with an equimolar amount of a solution(ca.20) of tosyl azide in anhydrous benzene. Stirringwas continued until the end of the reaction, normallyindicated by quantitative evolution of nitrogen.? Thecrude reaction mixtures were analysed by t.1.c. and theTABLE 2Analysis () ac Recryst. .Afrom Formula C H NPi-OH CISH,,N,O,S 58.2 (58.45) 6.4 (6.55) 9.1 (9.1)Pri,O C,,H,,N,O,S 60.9 (61.2) 7.3 (7.5) 9.75 (9.5)Cl,H2,N~03S 59.3 (59.6) 6.55 (6.9) 8.6 (8.7)Pri,O Cl,H,,N,O,S 63.06 (63.35) 7.9 (8.15) 8.4 (8.7)Ri2O C18H,,N203S 62.05 (61.7) 7.55 (7.5) 7.85 (8.0)Pr1,O C,,H,,N,03S 64.1 (63.8) 7.3 (7.5) 7.6 (7.45)Pri,O C,,H3,N20,S 63.4 (63.45) 8.15 (8.0) 7.2 (7.4)Cl8H2,N2o3S 61.3 (61.7) 7.5 (7.5) 7.9 (8.0)C,,H,,N,O,S 62.5 (63.0) 8.0 (7.95) 9.85 (10.0)The structures of the products were confirmed by lH n.m.r.(solvent C,D, or CDC1,;observed previously only in the case of enamines derivedfrom methyl isopropyl and methyl isobutyl k e t ~ n e . ~The ratio between the products (5) and (7) appears todepend on the nature of the P-substituents; in theseries of enamines (la-d and f ) increasing P-substitutionleads to increasing amounts of rearrangement products* The complexity of the structure of the enamine (le) makesit difficult in this case to rationalize the ratio of (5) to (7). t Compound (If) was used as the equilibrium mixture with itstmtomer, yielding at least four products from which (5f) and(7f) were isolated and identified.Me,products were isolated by one of the following methods;their properties are collected in Table 2.l2 P.Scheiner, ' Tnazoline Decomposition in Selective OrganicTransformations,' ed. B. S. Thyagarajan, vol. 1, Wiley-Inter-science, 1970, p. 327; R. A. Wohl, J . Org. Chew., 1973, 38,3862; R. Huisgen, R. Sustmann, and K. Bunge, Chem. Ber.,1972, 105, 1324; M. E. Hermes and F. D. Marsh, J . Ovg. Chem.,1972, 37, 2969; R. S. McDaniel and A. C. Oehlschlager, Tetru-hearon, 1969, 25, 1381.l3 R. A. Abramovitch, G. N. Knaus, hf. Pavlin, and W. D.Holcomb, J.C.S. Perkin I , 1974, 2169 and references therein.l4 R. Stradi and P. Dalla Croce, personal communication.l5 S. C. Bunce, J . Amer. Chem. SOC., 1955, 77, 6616J.C.S. Perkin I(a) Enafttines (la, and c-e). The crude solution with benzene-ethyl acetate containing 85--60 benzenewas evaporated to dryness and a first crop of the as eluant.less soluble amidine was obtained by recrystallization (b) Enantines ( I b and f ) . The crude mixture was(from di-isopropyl ether or propan-2-01). The mother evaporated and chromatographed directly on a silicaliquors were evaporated and the residue was chromato-graphed on a silica column (Kieselgel 60; Merck), *:5/1784 Received, 17th Septembev, 19753column, eluted as in (a)
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