LANTHANOIDS IN ORGANIC-SYNTHESIS .6. THE REDUCTION OF ALPHA-ENONES BY SODIUM-BOROHYDRIDE IN THE PRESENCE OF LANTHANOID CHLORIDES - SYNTHETIC AND MECHANISTIC ASPECTS
LANTHANOIDS IN ORGANIC-SYNTHESIS .6. THE REDUCTION OF ALPHA-ENONES BY SODIUM-BOROHYDRIDE IN THE PRESENCE OF LANTHANOID CHLORIDES - SYNTHETIC AND MECHANISTIC ASPECTS
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DOI：
10.1021/ja00408a029
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发表时间：
1981-01-01
影响因子：
15
通讯作者：
LUCHE, JL
中科院分区：
文献类型：
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作者：
GEMAL, AL;LUCHE, JL
氯化镧 (LnCl3) 是 NaBH4 在甲醇溶液中区域选择性 1, 2 烯酮还原的有效催化剂。该反应的最佳条件已确定。给出了描述 Ln3+ 离子作用的机理解释。 Ln3+ 的主要作用是通过羟基溶剂催化 BH4~ 分解生成烷氧基硼氢化物，这可能是观察到的区域选择性的原因。 Ln3+离子的存在也改变了该过程的立体选择性，增强了环己酮体系的轴向攻击。自从发现硼氢化物的还原性能以来，硼氢化钠作为羰基的选择性温和还原剂受到了相当多的关注。大量论文报告了合成、机械或立体化学重要性的结果，并且最近发表了评论
Lanthanoid chlorides (LnCl3) are efficient catalysts for the regioselective 1, 2 reduction of-enones by NaBH4 in methanol solution. Optimal conditions of this reaction havebeen determined. A mechanistic interpretation depicting the role of the Ln3+ ions is given. The major effect of Ln3+ is the catalysis of BH4~ decomposition by the hydroxylic solvent to afford alkoxyborohydrides, which may be responsible for theobserved regioselectivity. The stereoselectivity of the process is also modified by the presence of the Ln3+ ions, in that axial attackof cyclohexanone systemsis enhanced.Since the discovery of the reducing properties of boron hydrides, sodium borohydride has receivedconsiderable attention as a se-lective and mild reducing agent of the carbonyl group. A large variety of papers report results of synthetic, mechanistic, or ste-reochemical importance, and reviews have recently been pub-