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对手性噁唑硼烷催化3,3-二甲基丁酮-2不对称还原反应机理进行了从头算研究.结果表明,该不对称还原反应是放热的.反应经历了催化剂-硼烷加合物、催化剂-硼烷-酮加合物、含B-O-B-N四元环的催化剂-烷氧基硼烷加合物的生成,以及催化剂-烷氧基硼烷加合物的离解并再生催化剂等过程.在催化剂-硼烷-酮加合物经氢转移而生成催化剂-烷氧基硼烷加合物的过程中,氢转移与B-O-B-N四元环的形成是协同进行的.氢转移是还原反应的控制步骤.氢转移过渡态具有扭曲的椅式结构,所决定的还原产物是与实验相吻合的R手性醇.
The ab initio study on the asymmetric reduction of 3,3-dimethylbutanone-2 catalyzed by the chiral oxazaborolidine showed that the asymmetric reduction reaction was exothermic and the reaction had been catalyzed by borane The formation of the adduct, the catalyst-borane-ketone adduct, the BOBN four-membered ring catalyst-alkoxyborane adduct, and the dissociation of the catalyst-alkoxyborane adduct and the regeneration of the catalyst In the course of the catalyst-borane-ketone adduct being hydrogen-transferred to form the catalyst-alkoxyborane adduct, the hydrogen transfer is coordinated with the formation of the BOBN four-membered ring.The hydrogen transfer is a reduction reaction Control step. The transition state of hydrogen transfer has a distorted chair structure, and the reduction product determined is R chiral alcohol consistent with the experiment.