Synthesis of (Z)-β-(carbonylamino)alkenylindium via Regioselective Anti-carboindation of Ynamides and Its Transformation to Multisubstituted Enamides.

Abstract

The regioselective anti-carboindation of ynamides using InBr3 and silylated nucleophiles was developed to synthesize (Z)-β-(carbonylamino)alkenylindiums. The X-ray crystallographic analysis of an alkenylindium suggested the reaction proceeded in an anti-addition fashion. In contrast to reported syn-carbometalations of ynamides using organometallics, a cooperation of InBr3 and silylated nucleophiles to ynamides achieved an anti-addition, which was supported by DFT calculation. The scope of substrates included various ynamides and silylated nucleophiles such as silyl ketene acetals and silyl ketene imines. The transformation of synthesized alkenylindiums by iodination, radical coupling, and Pd-catalyzed cross-coupling successfully afforded trisubstituted enamines with high regio- and stereoselectivities.