Chiral Primary Amine Catalyzed Asymmetric Direct Cross‐Aldol Reaction of Acetaldehyde

The first primary aminocatalytic direct cross‐aldol reaction of acetaldehyde is presented. Among the various vicinal diamines screened, the L‐tert‐leucine derivative 1c in conjunction with (H4SiW12O40)0.25 was identified as the optimal catalyst; good catalytic activity (up to 99 % yield in 4 h), and high enantioselectivities (up to 92 % ee) were achieved for a range of donors, including aromatic aldehydes and isatin derivatives. Aqueous acetaldehyde solution and paraldehyde can be conveniently applied in this system.