Enantioselective Kinetic Resolution of trans-Cycloalkane-1,2-diols

摘要

The kinetic resolution of ehiral trans-cycloalkane-1,2-diols (1) presents a formidable challenge and a rare case where chemical methods are superior to enzymatic approaches. Taking the kinetic resolution of trans-cyclohexane-1,2-diol (1a, n = 2) through monoacylation as the delineating test reaction, it was shown that various Pseudomonas lipases display both low activities (reaction times typically within the range of days) and low selectivities. Purely chemical transformations utilizing benzoyl transfer in Gu~(II)-catalyzed reactions with C2-symmetric bisoxazoline ligands give good ee values for the monobenzoylated product (around 80%) and good conversions (37—46 %; selectivity factor s = 14-22) within hours; Diol la is resolved with up to 66% ee. Hence, the availability of a practical chemical method for the catalytic enantioselective kinetic resolution of diols 1 is desirable.