The Chemistry of Stable Carbenes. Part 2. Benzoin-type condensations of formaldehyde catalyzed by stable carbenes
作者:J. Henrique Teles、Johann-Peter Melder、Klaus Ebel、Regina Schneider、Eugen Gehrer、Wolfgang Harder、Stefan Brode、Dieter Enders、Klaus Breuer、Gerhard Raabe
DOI:10.1002/hlca.19960790108
日期:1996.2.7
Stable carbenes derived from thiazole, 1H-imidazole, and 4H-1,2,4-triazole are efficient catalysts for benzointype condensations of formaldehyde. Catalysts derived from N-substituted thiazolium salts trimerize formaldehyde to dihydroxyacetone (II). Catalysts based on 1,4-disubstituted 4H-1,2,4-triazol-1-ium salts give glycolaldehyde (I) as the main product and no II, whereas N,N′-disubstituted 1H-imidazol-3-ium
衍生自噻唑,1 H-咪唑和4 H -1,2,4-三唑的稳定卡宾是甲醛的苯偶姻型缩合反应的有效催化剂。由N-取代的噻唑鎓盐衍生的催化剂将甲醛三聚为二羟基丙酮(II)。基于1,4-二取代的4 H -1,2,4-三唑-1-鎓盐的催化剂以乙醇醛(I)为主要产物而没有II,而N,N'-二取代的1 H-咪唑-3-铵盐产生两种产物的混合物。在催化循环中分离几种中间体可以更好地了解反应机理。