Synthesis of (Z)‐β‐(Carbonylamino)alkenylindium through Regioselective anti‐Carboindation of Ynamides and Its Transformation to Multisubstituted Enamides

The regioselective anti‐carboindation of ynamides by using InBr3 and silylated nucleophiles was developed to synthesize (Z)‐β‐(carbonylamino)alkenylindiums. The X‐ray crystallographic analysis of an alkenylindium suggested that the reaction proceeded in an anti‐addition fashion. In contrast to reported syn‐carbometalations of ynamides by using organometallics, a cooperation of InBr3 and silylated nucleophiles to ynamides achieved an anti‐addition, which was supported by DFT calculations. 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. Regioselective anti‐carboindation: The regioselective anti‐carboindation of ynamides with InBr3 and silyl ketene acetals was achieved to give β‐(carbonylamino)alkenylindium. Superior π‐electron affinity of InBr3 efficiently activated the triple bond of an ynamide despite the existence of an amide moiety. The regioselectivity of the nucleophilic attack of a silyl ketene acetal was controlled by the polarization of a triple bond derived from a nitrogen atom.