Selective reduction of carbonyl compounds with diisobutyldialkylaminoalanes

Details are described of reaction of carbonyl compounds with diisobutyldialkylaminoalane (DIBAL-NR(2); R=Et, i-Bu, Ph) in order to establish their reduction characteristics. The reagents were extremely mild and reduced only aldehydes and ketones effectively in ethyl ether at 25 degrees C. The stereoselectivity in the reduction of representative cyclic ketones appeared not so high but quite different from that obtained by DIBAL-H itself. The reagents reduced alpha,beta-unsaturated aldehydes and ketones to the corresponding allylic alcohols without any detectable 1,4-reduction products, DIBAL-NR(2) also achieved the selective reduction of aldehydes or ketones in the presence of keto or other readily reducible functional group, however the chemoselectivity was less satisfactory than that achieved by diisobutylethoxyalane (DIBAL-OEt).