The reductions of an α, β-unsaturated lactone (5) and lactam (7) with the Ni2+/BH-4 system resulted in the formation of cis-hydrogenated products (8a and 9a) with high stereoselectivity. The cis products (8a and 9a) were easily isomerized to the corresponding trans isomers (8b and 9b, respectively) by refluxing with sodium methoxide in anhydrous methanol. Isotope labeling studies with methyl cinnamate as the substrate indicated that the reduction with this reducing system poceeds stepwise via a carbon-nickel intermediate.
α, β-不饱和
乳酮(5)和乳酰胺(7)在Ni2+/BH-4系统的还原反应中,生成了高立体选择性的顺式氢化产物(8a和9a)。顺式产物(8a和9a)通过在无
水甲醇中与
甲醇钠回流,易于异构化为相应的反式异构体(8b和9b)。以
肉桂酸甲酯为底物的同位素标记研究表明,该还原反应通过一个碳-
镍中间体以逐步方式进行。