Stereoselective preparation and reactions of configurationally defined dialkylzinc compounds

The reaction of cyclic and open-chain diastereomerically pure secondary org anoboranes with diisopropylzinc allows the preparation of secondary dialkyl zinc reagents with good to excellent retention of configuration as shown by deuterolysis and Cu-I- and Pd-0-mediated reactions with electrophiles. The importance of a high boron-zinc exchange rate to obtain high diastereosele ctivity has been shown. Improvement of the configurational stability and st ereomeric purity of the zinc intermediates has been obtained by using mono- isopinocampheylborane ((-)-IpcBH(2)) providing optically active dialkylzinc compounds (up to 96% ee) with enhanced diastereoselectivities.