Ester Exchange Reactions Catalyzed by Lanthenoid Alkoxid

镧系三-z-丙氧化物在一定条件下作为酯交换和酯醇交换反应的催化剂。镧系催化剂的催化活性高于常用的铝烷氧化物和钛烷氧化物。在这些反应中，伯醇和仲醇及其酯以高收率生成所需的酯。这些反应对具有长烷基链的酯类也表现出很高的适用性。但叔醇酯在此条件下的反应活性较差。酯交换反应适用于6-己内酯开环聚合，使聚合物具有高Mn和窄Mw/Mn值。镧系三-2-丙醇还催化羰基化合物与原甲酸甲酯的缩醛化反应。在该反应中，类镧三磺酸盐的催化活性优于醇氧化物。在磺酸盐的存在下，缩醛反应非常快，并以极好的收率生成了各种酮和醛的缩醛。α， β -不饱和醛与酮的Michael反应不成功，但得到相应的醛缩产物。-、-不饱和酮反应生成罗宾逊加合物，经迈克尔反应和醛醇缩合形成罗宾逊加合物。虽然这些反应不是催化性的，但使用化学计量量的2-丙氨酸导致了高收率。镧系三-2-丙醇是醛酮醛化反应的有效催化剂。环酮反应的缩合产物产率高，非环酮反应的缩合产物产率低。醛类反应产率高，生成β -羟基醛；2-丙醇反应在高温下生成1,3-二醇，以2-丙醇为供氢体，由meerwein - ponndorf - verley还原醛类反应生成。

Lanthanoid tri-z-propoxides acted as catalysts for the ester interchange and esteralcohol exchange reaction under mind conditions. The catalytic activity of the lanthanoid catalysts was higher than those of aluminum and titanium alkoxides which are commonly used for these reactions. In these reactions, primary and secondary alcohols and their esters gave the desired esters in high yields. These reactions also exhibited high applicability to the esters having a long alky1 chain. However, the reactivity of the esters of tertiary alcohols was poor under these conditions. The ester exchange reaction was applicable to the ring-opening polymerization of 6-hexanolide which gave the polymer having high Mn and narrow Mw/Mn values.Lanthanoid tri-2-propoxides also catalyzed the acetalization of carbony1 compounds with methy1 orthoformate. In this reaction however, lanthanoid trisulfonates were superior to the alkoxides in catalyticactivity. The acetalizationin the presence of the sulfonates was very fast and gave the acetals of various ketones and aldehydes in excellent yields.The Michael reaction of alpha, beta-unsaturated aldehyde with ketones was unsuccessful but gave the corresponding aldol condensation products. The reaction of alpha, beta-unsaturated ketones gave Robinson adducts which were formed via Michael reaction and then aldol condensation. Though these reactions were not catalytic, the use of stoichiometric amounts of 2-propxides resulted in high yields.Lanthanoid tri-2-propoxides were efficient catalysts for the aldol reaction of aldehydes and ketones. The reaction of cyclic ketones gave the condensation products in high yields, while that of noncyclic ketones produced the products in poor yields. The reaction of aldehydes formed beta-hydoxy aldehydes in good yields, whereas the reaction in 2-propanol at elevated temperatures formed 1,3-diol which were produced from Meerwein-Ponndorf-Verleyreduction of the aldols with 2-propanol as hydrogen donor.