Catalytic enantioselective synthesis of secondary alcohols using C2-symmetric diamino diol ligands

A new class of diamino diols was evaluated as catalytic ligands in the enantioselective borane reduction of aromatic ketones and the enantioselective ethylation of arylaldehydes with diethylzinc. By variation of the substitution pattern on the ketone, e.e.s of up to 94%,, could be obtained by in situ borane reduction using 0.025 equiv. of the ligand at 35 degreesC in THF. N,N,N',N'-Tetramethyldiamino diol and N,N'-dialkyl diamino diol were used as promoters for the enantioselective addition of diethylzinc reagent to the arylaldehyde, where use of 0.1 equiv. of N,N,N',N'-tetramethyl diamino diol as catalyst in the addition of diethylzinc to arylaldehyde achieved e.e.s of up to 98%. (C) 2001 Elsevier Science Ltd. All rights reserved.