硼氢化钠还原烯烃和炔烃的研究进展

Research Progress in Reduction of Alkenes and Alkynes by Sodium Borohydride

不饱和烃催化加氢一直是制备某些无法从自然界得到或合成的化合物的重要途径,在化工生产和科学研究中极其重要。传统不饱和烃的加氢不仅需要催化剂,而且需要较高的反应温度和氢气压力,反应条件相对苛刻,不仅对反应设备要求严格,而且在反应过程中存在安全隐患。因此亟需探索一种反应条件温和、催化效果优异的催化体系。1942年Brown发现了NaBH_(4),其是一种廉价、安全、稳定、易于处理且具有较强还原性的氢化物,一般用来还原醛酮羰基。Brown还在1962年首次报道了NaBH_(4)在催化剂的存在下还原简单烯烃,这是NaBH_(4)作为氢供体还原不饱和烃的第一个实例,该方法成为传统不饱和烃还原的替代性方法。NaBH_(4)能还原不饱和烃是基于催化剂的存在,催化剂分为贵金属催化剂和非贵金属催化剂,贵金属催化剂主要为Pd、In、Ru等,非贵金属主要为Cu、Co、Ni等。贵金属和非贵金属催化剂是指其金属盐或负载在载体上的金属纳米粒子,都具有高催化活性和化学稳定性。最初的研究主要以贵金属催化剂为主,然而贵金属催化剂在价格上相对昂贵,某些贵金属催化剂存在使用后即失活的缺点,这明显增加了成本。随着研究的深入,学者们逐渐倾向于非贵金属催化剂,非贵金属催化剂不仅价格低廉,而且在催化效果上与贵金属催化剂相差无几。目前,贵金属催化剂/NaBH_(4)催化体系下,不饱和烃的转化率最高可以达到99%;而非贵金属催化剂/NaBH_(4)催化体系下,不饱和烃的转化率最高可以达到98%。可见两种催化剂催化还原不饱和烃的转化率基本一致,催化活性基本相同。因此,无特殊要求时可以使用非贵金属催化剂代替某些贵金属催化剂。本文综述了近年来NaBH_(4)在不同非贵金属/贵金属催化剂条件下还原烯烃和炔烃的研究成果和进展,包括含有敏感保护基团的烯烃和炔烃,并进行了总结和展望。

Catalytic hydrogenation of unsaturated hydrocarbons has always been an important approach to prepare compounds which can not be obtained from nature,which is extreme important in industrial production and researches.Traditional hydrogenation of unsaturated hydrocarbons not only requires catalysts,but also higher reaction temperature and hydrogen pressure are needed,the reaction conditions are relatively harsh,which is not only extreme strict for reaction equipment,but also has obvious issues of potential safety in the reaction.Therefore,it is necessary to explore a catalytic system with mild reaction conditions and excellent catalytic effect.NaBH_(4) was discovered by Brown at the University of Chicago in 1942.Organic borohydride is generally applied to reduce the carbonyl groups of aldehydes and ketones as cheap,safe,stable,easily handling and highly reductive.In 1962,Brown first reported the reduction of simple alkynes by NaBH_(4) in the presence of catalyst.This is the first example of NaBH_(4) as a hydrogen donor for the reduction of unsaturated hydrocarbons,an alternative method for the reduction of unsaturated hydrocarbons was found.NaBH_(4) can reduce unsaturated hydrocarbons based on catalysts.The catalysts can be divided into precious metal and non-precious metal catalysts.The precious metal catalysts are mainly Pd,In,Ru and other metals,while the non-precious metals mainly include Cu,Co,Ni and other metals.Precious metal and non-precious metal catalysts are metal salts or metal nanoparticles supported on carrier,which have high catalytic activity and chemical stability.At first,precious metal catalysts were mainly studied,however the price of precious metal catalysts was relatively high,some precious metal catalysts were deactivated after application.Non-precious metal catalysts are gradually becoming the focus as researches continue,which are not only cheap,but also have similar catalytic effect with precious metal catalysts.Now,the conversion rate of unsaturated hydrocarbon can be boosted up to 99%in precious metal catalyst/NaBH_(4) catalytic system,98%conversion rate can be achieved in non-precious metal catalyst/NaBH_(4) catalytic system.It can be noted that the conversion rate and catalytic activity of the two catalysts are basically same.Therefore,non-precious metal catalysts can be applied instead of precious metal catalysts without special requirements.Here the essay reviews recent research results and advancements of alkenes and alkynes by NaBH_(4) under various non-precious metal/precious metal catalysts,including the alkynes and alkynes containing sensitive protective groups.The reduction of alkynes and alkynes by sodium borohydride are briefly introduced,summarized and prospected.