| Abstract: | α-Methylthio-propiophenone anti-oxime p-toluenesulfonate (tosylate) ( 12b ) fragments quantitatively in 80% ethanol yielding benzonitrile and a methylidenesulfonium ion 15 . The syn-isomer, however, undergoes a Beckmann rearrangement. The fragmentation of α-methylthio-isobutyropher one anti-oxime tosylate ( 13b ) is accompanied by cyclization to the 1, 2-thiazetin-1-ium ion 27 , which is hydrolyzed via the sulfimine 29 to the keto sulfide 20 and the keto sulfoxide 30 . A comparison of the rates of the α-alkylthio anti-ketoxime tosylates 12b and 13b and of the homomorphous oxime tosylates 16b and 17b shows that fragmentation and cyclization are strongly assisted by the sulfur atom. Whereas both the anti- and syn-isomers of α-amino ketoxime derivatives fragment quantitatively, only the anti-isomers of α-alkylthio ketoxime derivatives undergo facile fragmentation. |
