A novel synthetic strategy involving the Eschenmoser coupling reaction of 4-bromoisoquinoline-1,3(2H,4H)-diones with substituted thioformanilides, thioacetanilides, and thiobenzanilides
gave 18 (Z)-4-((substituted phenylamino)methylidene)isoquinoline-1,3(2H,4H)-diones. The reaction occurs under mild conditions (DMF or MeCN, 25–60 °C) without
any base or thiophile and in good yields (43–95%). Furthermore, for the synthesis
of starting thioformanilides carrying basic substituents, a new thioacylation protocol
was developed that involves a thioacylating agent formed from carbon disulfide and
lithium triethylborohydride.
Key words
Eschenmoser coupling reaction - 4-bromoisoquinoline-1,3(2
H,4
H)-diones - thioamides - thioacylation - bromination