非过渡金属催化体系NHPI/DDQ/NaNO_2催化分子氧选择氧化醇

Selective Oxidation of Alcohols Catalyzed by a Transition Metal-Free System of NHPI/DDQ/NaNO_2

考察了N-羟基邻苯二甲酰亚胺(NHPI),2,3-二氯-5,6-二氰基-1,4-苯醌(DDQ)与NaNO2组成的非金属催化体系,催化分子氧选择氧化醇的反应性能.结果表明,该体系可有效地催化芳香醇等生成相应的醛(酮).在80°C反应6h,苯甲醇转化率达到65%,苯甲醛选择性为99%.此外,该催化体系也能有效地催化其它醇的选择氧化.在该催化体系中,DDQ夺取NHPI羟基的H原子生成催化活性物种邻苯二甲酰亚胺氮氧自由基PINO与氢醌;而高亲电性的PINO能够夺取醇分子上的H原子,进一步反应生成醛(酮);NaNO2分解产生的氮氧化合物催化了分子氧氧化氢醌生成醌的过程.

A transition metal-free catalyst composed of N-hydroxyphthalimide（NHPI）,2,3-dichloro-5,6-dicyano-benzoquinone（DDQ）,and NaNO2 was studied for the selective oxidation of alcohols using O2 as oxidant.The reaction results showed that this catalyst system can effectively catalyze the oxidation of alcohols to the corresponding aldehydes or ketones.99% selectivity for benzaldehyde at 65% conversion of benzyl alcohol was obtained at 80 °C for 6 h.In the process of reaction,DDQ abstracted a hydrogen atom from NHPI to generate a highly reactive PINO free radical and hydroquinone.Then,PINO abstracted a hydrogen atom from alcohols to generate aldehydes or ketones.Finally,NO from NaNO2 decomposition in the reaction media catalyzed the oxidation of hydroquinone to quinone by O2.