Application of organolithium and related reagents in synthesis, Part X. Metallation-electrophilic substitution sequence of secondary chlorobenzamides

摘要

The lithiation (BunLi/THF) of 2-chloro- (1), 3-chloro- (2) and 4-chlorobenzanilides (3) and the subsequent reactions of the corresponding bis-lithiated anilides4–6with electrophiles (MeI, CH2=CH-CH2Br,Me3SiCl,MeCHO,o-MeOC6H4CHO,p-MeOC6H4CHO,Me2NCHO andp-MeOC6H4CONMe2) towards the synthesis of theorthosubstituted chlorobenzoesic acids derivatives12–14have been described. The effect of the chlorine substituent upon the generation and stability of the bis-lithiated chloro-anilides4–6has been studied. It has been found that the bis-lithiated chloro-anilide5derived fromm-chloro-benzanilide (2) at a temperature above −30°C converts into the corresponding benzyne9. The anilide moiety (masking group) of the formedortho-substituted chlorobenzanilides appeared to be effectively removable on acid-driven hy