Effect of Temperature on the Enantioselectivity in the Oxazaborolidine-Catalyzed Asymmetric Reduction of Ketones. Noncatalytic Borane Reduction, a Nonneglectable Factor in the Reduction System
作者:Xu、Wei、Zhang
DOI:10.1021/jo035203v
日期:2003.12.1
The effect of temperature on the enantioselectivity of the oxazaborolidine-catalyzed asymmetric borane reduction of ketones has been investigated carefully using alkyl aryl ketones with a variety of functional groups and a B-methoxyoxazaborolidine derived from trimethyl borate and (S)-alpha,alpha-diphenylprolinol as a catalyst. The reductions were carried out over a range of temperatures in THF and
使用具有各种官能团的烷基芳基酮和衍生自硼酸三甲酯和(S)-α,α-二苯基脯氨酸的B-甲氧基恶唑硼烷仔细研究了温度对恶唑硼烷催化的不对称硼烷还原酮的对映选择性的影响。作为催化剂。在有或没有催化剂的情况下,在THF和甲苯中的一定温度范围内进行还原。通过GC分析确定酮向醇的转化率,还原速率随着有或没有催化剂的反应温度的升高而增加。但是,催化还原的速率比没有催化剂的速率增加得更快。结果表明,非催化硼烷还原是还原中对映选择性的重要因素。