Development of dehydrogenation reaction using palladium catalyst and ethylene system

综述了最近报道的以分子氧为氧化剂的醇在铜、钚、钯等过渡金属催化量存在下的氧化过程。还描述了醇与简单烯烃(如乙烯)之间的氢转移反应对醇的氧化。也就是说，在乙烯气氛下，在活性碳(Pd-C)上催化量的钯可以将一些苄基和烯丙醇转化为相应的羰基化合物。Pd(OAc)2和乙酸乙烯酯的组合也有效。碳水化合物(D-糖基)和类固醇上的羟基的选择性氧化以及更简单的体系已经实现。Pd-C/乙酸/02体系也实现了氧化芳构化反应。在氧气气氛下，1，3，5-三取代吡唑和Hantzsch-1，4-二氢吡啶在醋酸中催化处理，可有效地转化为相应的吡唑和吡啶。在氧气气氛下，以活性碳(Darco KB)为催化剂，由2-氨基酚和醛直接合成了2-芳基苯并恶唑类化合物。这些环境友好的氧化方法有可能取代传统的化学计量比铬和其他金属氧化剂。

Recently reported oxidation process of alcohols using molecular oxygen as an oxidizing agent in the presence of catalytic amount of transition metals such as copper, ruthenium, and palladium compounds will be reviewed. Oxidation of alcohols based on hydrogen transfer reaction between alcohols and simple olefins such as ethylene is also described. That is, some benzylic and allylic alcohols can be converted into the corresponding carbonyl compounds using a catalytic amount of palladium on activated carbon (Pd-C) under ethylene atmosphere. The combination of Pd(OAc)2 and vinyl acetate also works efficiently. Selective oxidation of hydroxy groups on carbohydrates (D-glycals) and steroids as well as simpler systems has been achieved. Oxidative aromatization reaction has been also realized by Pd-C/acetic acid/02 system. 1,3,5-Trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines were converted into the corresponding pyrazoles and pyridines effectively by the treatment of a catalytic amount of Pd/C in acetic acid under oxygen atmosphere. Direct synthesis of 2-arylbenzoxazoles from 2-aminophenols and aldehydes was achieved in the presence of activated carbon (Darco KB) under oxygen atmosphere. These environmentally benign oxidation methods have potentialities to replace the conventional stoichiometric chromium and other metal oxidizing agents.