In situ preparation of chiral derivatives of oxaborolidine-borane complexes, useful in asymmetric reduction reactions of etheroximes or ketones to chiral alcohols or amines

摘要

Preparation in situ of oxaborolidine-borane complexes by addition of a Lewis base and an ester of an inorganic acid to a suspension of a metal borohydride, which are used as catalysts for the synthesis of chiral alcohols and amines. The preparation of oxaborolidine-borane complexes comprises the addition of a Lewis base of formula (II) and an ester of an inorganic acid to a suspension of a metal borohydride. R1-A-(R2)n (II) R1,R2alkyl(optionally substituted), aryl(optionally substituted), alkylaryl, or 4 - 7C cycloalkyl; n : 1 or 2; A : N, O, S or P; R1+ R21 - 7C carbocycle, optionally substituted - and an inorganic acid ester R3-X (III); X : sulfonyloxyester(OS(O)2OR4), sulfonate(-OS(O)R5) or sulfite(-OS(O)OR5); R3, R4 and R5alkyl optionally substituted by halogen, aryl, heterocycle, heteroaryl, alkoxy, alkylthio, alkylaryl or 4 - 7C cycloalkyl; R4 + R51 - 7C carbocycle, optionally substituted - to a suspension of a metal borohydride MBH4(I), in which M is Na, K, Li, Zn (preferably Na). Then, (stage 2), to the product obtained above, an optically active amino-alcohol R6-NH-C3-(R7R8)-[C2]n(R9R10-C1(R11R12-OH (IV) is added; R6H, 1 - 8C alkyl or 1 - 15C arylalkyl(optionally substituted); R7 - R12H, 1 - 8C alkyl, 6 - 12C aryl or 7 - 1C arylalkyl, on condition that R6 and R7 are different; n : 0, 1, 2 or 3; R6+R7 or R7+R11, or R8+R9 or R10+R11form 3 - 6C alkylene; R8+R9alkylene substituted or fused with a benzene ring; and C1 and/or C2 and/or C3symmetric carbon. An independent claim is also included for the synthesis of chiral alcohols and amines using the complexes described.