Asymmetric hydroboration for

Asymmetric Hydroboration. For reaction with a prochiral alkene, (/ ,/ )-2,5-dimethyl-B-methoxyborolane is liberated from (1) and a standard solution of the corresponding lithium dihydri-doborate in ether is prepared (eq 5). Hydroboration is effected by addition of lodomethane to the solution of dihydridoborate and alkene (eq 6). After oxidation, chiral secondary alcohols of high enantiomeric purity and predictable configuration are obtained from cis, trans, and (risubstituted alkenes. As is the case with other known asymmetric hydroborating agents, 2-methyl-1-alkenes react with low asymmetric induction. 

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