Copper(I)-catalyzed highly regio- and stereoselective boron addition-protonolysis of alkynamides to give alkenamides

Copper-catalyzed and highly chemoselective reduction of N-alkynylamides by a boron addition-protonolysis protocol is presented. The reaction proceeds with the addition of boryl-copper complex to N-alkynylamides with high regioselectivity and stereoselectivity, followed by regiocontrolled transmetallation of the α-site of the alkenylboronate with MeOCuL to afford N-alkenylamides in good yields. Deuterium labeling experiments indicated that both of the alkenyl hydrogen atoms originate from the additive methanol. The copper-catalyzed semireduction of N-alkynylamides by a boron addition-protonlysis protocol afforded N-alkenylamides in good yields with high stereo- and chemoselectivity. Deuterium labeling experiments indicated that both of the alkenyl hydrogen atoms of the N-alkenylamides originate from the additive methanol.