Development of Highly Selective Reducing Reagent Which is Useful in Organic Synthesis

氢化二异丁基铝（DIBAH）是一种广泛应用的还原剂，它与α，<alpha>β<beta>-不饱和羰基化合物反应生成烯丙醇。我们已经发现，六甲基磷酰三胺（HMPA）配体改变DIBAH的还原反应性，以实现共轭还原的<alpha>，<beta>-不饱和羰基化合物没有羰基还原和甲基铜催化剂增强的反应性的共轭还原DIBAH-HMPA。MeCu-DIBAH<alpha><beta>-HMPA体系可实现多种α-不饱和羰基化合物（醛、酮和酯）的选择性和有效的共轭还原。MeCu-DIBAH-HMPA体系实现孕酮和角甲基化茚酮的立体选择性反式共轭还原。后一种还原提供了制备角甲基化反式稠合的茚满环的方便方法。铜化合物的种类控制共轭还原的立体选择性，HCu-DIBAH-HMPA体系主要生成顺式稠合的茚满酮。MeCu-DIBAH<alpha><beta>-<alpha><beta>HMPA体系不含HMPA时，能有效地还原，-不饱和腈，从而开发了一种新型的、化学和立体选择性的还原剂MeCu-DIBAH-HMPA.

Diisobutylaluminum hydride (DIBAH) is a widely employed reducing reagent, which reacts with <alpha> , <beta> -unsaturated carbonyl compounds to produce allylic alcohols. We have found that the hexamethylphosphoric triamide (HMPA) ligand changes the reducing reactivity of DIBAH to effect the conjugate reduction of <alpha> , <beta> -unsaturated carbonyl compounds without the carbonyl reduction and the methylcopper-catalyst enhances the reactivity of the conjugate reduction by DIBAH-HMPA. The selective and efficient conjugate reduction of a variety of <alpha> , <beta> -unsaturated carbonyl compounds (aldehydes ketones, and esters) can be accomplished by MeCu-DIBAH-HMPA.The MeCu-DIBAH-HMPA system effects the stereoselective trans conjugate reduction of progesterone and angularly methylated hydrindenone. The latter reduction provides a convenient method of preparing angularly methylated trans fused hydrindane ring. The kind of the copper compound controles the stereoselectivity of the conjugate reduction, and the HCu-DIBAH-HMPA system gives predominantly the cis fused hydrindanone. The <alpha> , <beta> -reduction of <alpha> , <beta> -unsaturated nitriles can be effected by the MeCu-DIBAH system without HMPA.Thus, we have been able to develope a novel, chemo- and stereoselective reducing reagent of MeCu-DIBAH-HMPA which is useful in organic synthesis.