Aza Cope Rearrangements in the Cyclopropenyl-and Allyl-Substituted Δ2-Oxazolinone Systems

Article abstract of DOI:10.1021/jo00153a015

The scope of the thermal and photochemical reorganization reactions of a number of cyclopropenyl- and allyl- substituted oxazolinones has been examined.These systems undergo a facile sigmatropic rearrangement in accord with orbital symmetry predictions. 2-Methyl-4-allyl-Δ²-oxazolinones were found to undergo a 3,3-sigmatropic allyl shift on thermolysis to give the Δ³-oxazolinone isomer.In contrast, on direct irradiation the 2-methyl-4-allyl-Δ³-oxazolinones undergo a 1,3-allyl shift to give the Δ²-isomer.The 4,4-disubstituted Δ²-oxazolinones undergo decarbonylat ion either on irradiation or by flash vacuum pyrolysis to give acetimides.The acetimides formed were easily hydrolyzed to give the corresponding ketones.The excited-state behavior of the 2-phenyl-4-methyl-Δ²-oxazolinone system was found to be markedly different from that encountered with the 2-methyl-4-phenyl-substituted isomer.The rationale for the difference in behavior is discussed.