LiClO4‐katalysierte nucleophile Addition an α‐chirale Aldehyde, Aldimine und Oxirane

LiClO4‐Catalyzed Nucleophilic Addition to α‐Chiral Aldehydes, Aldimines, and Oxiranes The diastereoselectivity of lithium perchlorate‐induced addition of trimethylsilyl cyanide and O‐silylated ketene acetals to α‐chiral aldehydes is studied. Whereas aldehyde 1 reacts with the ketene acetal 2 exclusively to form the syn‐ester 3, a divergent selectivity is observed in the case of trimethylsilyl cyanide addition to 5 and 11a–c. Also the reaction of O‐silylated ketene acetals with aldimines 16 in the presence of lithium perchlorate proceeds smoothly to afford the corresponding β‐amino esters 17 in high yields. While the silyl ketene acetal of methyl acetate leads preferentially to the corresponding anti‐diastereomer, in the case of the silyl ketene acetal of methyl isobutyrate a syn‐/anti‐selectivity in the range of 79:21 to 44:56 is observed. In the presence of lithium perchlorate solution in ether the oxiranes 27a–d undergo facile nucleophilic ring opening reactions with 2, 29, and 30.