关于羧酸酯还原为醇的原理

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1、金属钠和醇为还原剂（Bouveault-Blanc反应）金属氢化物为还原剂本反应是将羧酸酯用金属钠和醇直接还原生成相应的伯醇，主要用于高级脂肪羧酸酯的还原n-C11H23OEtOn-C11H23OHNa,EtOHtolueneOrganic Syntheses,Coll.Vol.2,p.372;Vol.10,p.62LiAlH4还原异丁醇铝还原硼氢化钠（钾）还原NaBH4-ZnCl2还原ROR1OROR1OAlH3ROR1OHRHOROAlH3ROHLiAH4LiAH4-R1OH1.减少用量并在低温下或降低其还原能力，可使反应停留在醛的阶段2.降低其还原能力可以提高还原反应的选择性常用的方法是

2、加入不同比例的无水三氯化铝或加入计算量的醇，取代LiAH4中的个氢原子而成铝烷或烷氧基LiAH4TBSONMe2CO2MeTBSONMe2OHLiAH4,ether5 oCOrganic Syntheses,Coll.Vol.10,p.442;Vol.78,p.160Work up:The reaction mixture is stirred for 15 min, diluted with ether(100 mL), and quenched by dropwise addition of water (9 mL). The resulting gray suspension is al

3、lowed to reach RT, and the mixture is stirred vigorously for an additional 60 min.The mixture is transferred to a 1.0-L Erlenmeyer flask and diluted with ether(350 mL).HNNOOHNNOHlithum tri-sec-butylborohydridePatent:US5849764 A1(1998/12/15)1.The mixture was stirred at -78oC for 4h,followed by warmin

4、g to -40oC for 4h2.The reaction was quenched by addition of aqueous methanol.NCO2CH3H3CO2CNOHHONaBH4Liebigs Ann.lRecueil 1997,707-720.此法操作较为简单，安全由于NaBH4的还原性不够强，因此此类反应一般需要回流过夜而且，反应初始阶段不要去加热，而是在室温下搅拌数小时后再缓缓加热至回流，否则极易冲料EtOOCCOOEtOTIPSEtOOCOTIPSOHZn(BH4)2THFOrganic Syntheses,Coll.Vol.7,p.530;Vol.63,p.136OOOCNOCNHOOOONaBH4