Two-Carbon Homologation of Hemiaminal Ethers Using Enecarbamates

Significance

Hemiaminal ethers 2 were used as substrates for two-carbon homologation with ­enecarbamates 3. Employing chiral phosphoric acids 1 as catalysts, hemiaminal products 4 were obtained in moderate to high yield with high enantioselectivity. The more problematic reaction with aliphatic hemiaminal ethers was solved by using enecarbamates with the more electron-withdrawing trichloroethoxycarbonyl group. The method was shown to be compatible with α-methyl-substituted enecarbamates giving syn or anti product depending on the geometry of the starting enecarbamate.