Anomalous ozone degradations of 1-chloro substituted conjugated dienes in methanol

Abstract

KARL GRIESBAUM and ASHIS R. BANDYOPADHYAY. Can. J. Chem. 65, 487 (1987). Diozonolyses in methanol of (E~-4-chloro-2,3-dimethyl-1,3-hexadiene (40) and of (4E)-5-chloro-3,4-dimethyl-2,4-heptadiene (4b) resulted in complete cleavage of the double bonds and of the single bonds of the respective diene systems. The course of these anomalous cleavage reactions has been established by step-wise ozonolyses of these dienes, and by the identification of labile methoxy hydroperoxides as intermediates.KARL GRIESBAUM et ASHIS R. BANDYOPADHYAY. Can. J. Chem. 65, 487 (1987). La diozonolyse du chloro-4 dimkthyl-2,3 hexadiene-1,3-(E) (4a) et du chloro-5 dimkthyl-3,4 heptadiene-2,4-(E4) (4b), dans le mkthanol, conduit 21 une coupure complete des doubles et des simples liaisons des systemes dikniques respectifs. On a determink le cours de ces rkactions de coupures anormales en prockdant a l'ozonolyse par etape de ces diknes ainsi qu'a l'identification des mkthoxy hydroperoxydes labiles comme intermkdiaires.[Traduit par la revue] Introduction product 2 was lowered from 96% after direct warm-up to 60% previous work we obtained the chlorinated diene 1 as one after DMS-d6 treatment in the ozonolysis of 4a and from 95 to of several products from the reaction of anhydrous hydrogen 18% in the OzOnO1~sis 4b. chloride with 2-butyne (1).an attempt to confirm this These results demonstrated that 4a and 4 b underwent anomstructure by ozone degradation, we observed an anomalous alous ozonolysis reactions, similar to that observed for 1, viz. ozonolysis of 1 in methanol, which resulted in the cleavage of by cleavage of the double bonds and the sing1e the double bonds and of the single bond of the diene system to of the respective conjugated diem systems. The fact that the give fragments 2 and 3 in a ratio of 3: 1 (2). extent of the abnormal cleavage could be lowered by reduction of the product mixture indicated, however, that it did not occur CH3 CH3 CH3 C1