Key Laboratory of Applied Chemistry of Chongqing Municipality, and Chongqing Key Laboratory of Soft-Matter Material Chemistry and Function Manufacturing, School of Chemistry and Chemical Engineering , Southwest University , Chongqing 400715 , China.
J Am Chem Soc. 2019 Apr 3;141(13):5159-5163. doi: 10.1021/jacs.9b01910. Epub 2019 Mar 25.
A chiral aldehyde is rationally combined with a Lewis acid and a transition metal for the first time to form a triple catalytic system. This cocatalytic system exhibits good catalytic activation and stereoselective-control abilities in the asymmetric α-allylation reaction of N-unprotected amino acid esters and allyl acetates. Optically active α,α-disubstituted α-amino acids (α-AAs) are generated in good yields (up to 87%) and enantioselectivities (up to 96% ee). Preliminary mechanism investigation indicates that the chiral aldehyde 3f acts both as an organocatalyst to activate the amino acid ester via the formation of a Schiff base, and as a ligand to facilitate the nucleophilic attack process by coordinating with π-allyl Pd(II) species.
手性醛首次与路易斯酸和过渡金属合理组合形成三重催化体系。该共催化体系在 N-未保护的氨基酸酯和烯丙基乙酸酯的不对称α-烯丙基化反应中表现出良好的催化活化和立体选择性控制能力。光学活性的α,α-二取代α-氨基酸（α-AAs）以良好的收率（高达 87%）和对映选择性（高达 96%ee）生成。初步的机理研究表明，手性醛 3f 既可以作为通过形成席夫碱来激活氨基酸酯的有机催化剂，也可以作为通过与π-烯丙基 Pd(II)物种配位来促进亲核攻击过程的配体。
