Reaction of lithioamino anions with α-oxoketene dithioketals: an improved and a new general method for the synthesis of α-oxoketene S,N- and N,N-ketals

Abstract

A new method has been developed for the preparation of α-oxoketene S,N- (A) and N,N-(B) ketals starting from α-oxoketene dithioketals by employing mild conditions. Thus, lithioamino anions 2a–c, 4 and 6 are treated with α-oxoketene dithioketals 1 to afford the corresponding S,N-ketals 3a–j, 5a–j, 7a–e and N,N-ketals 8a,b in good yields. The scope and steric orientations of the reaction have been investigated.