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 (H 4 SiW 12 O 40 ) 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.