Studies on Asymmetric Hydrogenation

由于现有的均相催化剂缺乏反应性和/或立体选择性，因此迫切需要开发立体选择性加氢的实用方法。新型Ru （II）配合物的分子式为反式rucl_2（膦）_2（1,2-二胺）或反式rucl_2（二膦）（1,2-二胺），在2-丙醇中具有碱碱效应，易于多种简单酮的加氢。例如，底物/催化剂摩尔比为240万的苯乙酮在45 atm下，在30℃下加氢，定量得到1-苯乙醇。转换频率（TOF），定义为每摩尔Ru催化剂每小时生成的摩尔数，接近228,000。即使在大气中的氢气压力下，反应也能以合理的速度进行。这种混合配体催化剂在烯烃或内部乙炔键存在的情况下对羰基功能进行化学选择性加氢。使用庚醛和1-辛烯等摩尔混合物的反应显示羰基/烯烃选择性高达1500。此外，许多具有碳*碳多重键的酮和醛在羰基上优先氢化，从而生成不饱和醇。共轭和非共轭的烯醛或烯酮都可以使用。用2,2′-双（二苯基膦）-1,1′-二萘基（BINAP）和某些手性1,2-二胺如1,2-二苯基乙二胺和1-烷基-2,2-双（对甲氧基苯基）-1,2-乙二胺修饰Ru催化剂，可实现简单酮的高度对映选择性加氢。烷基芳基酮和线性α、β -不饱和酮在室温下，在1- 8atm的H_2条件下加氢，得到相应的手性醇，收率接近100%，ee高达99%。由于催化剂成本低，操作简单，并且具有环保意识，该方法对大规模反应特别有用。

The development of practical methods effecting stereoselective hydrogenation of simple ketones is highly desirable, since the existing homogeneous catalysts lack reactivity and/or stereoselectivity. New Ru (II) complexes having a formula of trans-RuCl_2 (phosphine) _2 (1,2-diamine) or trans-RuCl_2 (diphosphine) (1,2-diamine) in 2-propanol containing alkaline base effect facile hydrogenation of a wide variety of simple ketones. For example, hydrogenation of acetophenone with a substrate/catalyst molar ratio of 2,400,000 under 45 atm at 30'C gives 1-phenylethanol quantitatively. The turnover frequency (TOF), defined as the moles of product per mol Ru catalyst per hour, approaches 228,000. The reaction proceeds at a reasonable rate even under atmospheric pressure of hydrogen.This mixed-ligand catalyst effects chemoselective hydrogenation of a carbonyl function in the presence of an olefinic or internal acetylenic bond. The reaction using an equimolar mixture of heptanal and 1-octene displays a carbonyl/olefin selectivity as high as 1500. Furthermore, a wide range of ketones and aldehydes possessing a carbon*carbon multiple bond are hydrogenated preferentially at the carbonyl group, leading to unsaturated alcohols. Both conjugated and unconjugated enals or enones can be used.Highly enantioselective hydrogenation of simple ketones is achievable when the Ru catalyst is modified by 2,2'-bis (diphenylphosphino)-1,1'-binaphthyl (BINAP) and certain chiral 1,2-diamines such as 1,2-diphenylethylenediamine and 1-alkyl-2,2-bis (p-methoxyphenyl)-1,2-ethylenediamine. The hydrogenation of alkyl aryl ketones and linear alpha, beta-unsaturated ketones under 1-8 atm of H_2 at room temperature affords the corresponding chiral alcohols in near 100% yield and in up to 99% ee.This procedure is particularly useful for a large-scale reaction because of the low cost of the catalyst, operational simplicity, and environmental consciousness.