Z-Selective 1,4-Addition of 5H-Oxazol-4-ones with Alkynyl Carbonyl Compounds

Significance

An asymmetric 1,4-addition of 5H-oxazol-4-ones 2 with alkynyl carbonyl compounds 3 was developed. High geometric control was achieved to afford the thermodynamically less stable Z-isomer. Chiral guanidine catalyst 1 bearing a free hydroxy group gave addition products 4 with high enantioselectivity in low to good yields. The Z/E-selectivity of the addition increased with the electron-donating ability of the R^³ group in alkynyl carbonyls 3.