Studies on lead tetraacetate oxidation of α-oxoketene S,N- and N,N-acetals

Abstract

Lead tetraacetate oxidation of α-oxoketene-S,N-phenyl (1a ) and S,N-benzyl (1b ) acetals gave the iminoacetate 2 and α-acetoxy-S,N-acetal 3 respectively, while the corresponding S,N-ethylacetal 1c yielded the iminodiacetate 5 . The corresponding N,N-arylacetals 7a -d afforded the respective 2-N-aryl-3-(arylimino)-5-aryl-4-isoxazolines 8a -d under similar conditions via oxidative cyclization. The oxidation of N,N-(4-methylphenyl)acetal 7e gave 3-benzoyl-5-Bethyl-2-(4-methylphenylamino)-indole 9a , iminodiacetate 10 and the dimeric indole 11 , besides the corresponding 3-(4-methylphenyl-imino) isoxazoline 8e in varying yields. The N,N-(2-methylphenyl) acetals 7f and 7g afforded under similar conditions the respective 3-(2-methylphenylimino)isoxazolines 8f , 8g and the indoles 9b , 9c in good yields. The structural assigment and the probable mechanism of the formation of all the products have been discussed.