Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, USA.
J Am Chem Soc. 2011 Oct 26;133(42):16774-7. doi: 10.1021/ja207218f. Epub 2011 Oct 3.
Lithium enolates are widely used nucleophiles with a complicated and only partially understood solution chemistry. Deprotonation of 4-fluoroacetophenone in THF with lithium diisopropylamide occurs through direct reaction of the amide dimer to yield a mixed enolate-amide dimer (3), then an enolate homodimer (1-Li)(2), and finally an enolate tetramer (1-Li)(4), the equilibrium structure. Aldol reactions of both the metastable dimer and the stable tetramer of the enolate were investigated. Each reacted directly with the aldehyde to give a mixed enolate-aldolate aggregate, with the dimer only about 20 times as reactive as the tetramer at -120 °C.
锂烯醇盐是一种广泛应用的亲核试剂，其溶液化学性质复杂，且部分内容尚未完全了解。在四氢呋喃中，用二异丙基氨基化锂对 4-氟苯乙酮进行脱质子化反应，通过酰胺二聚体的直接反应生成混合烯醇盐-酰胺二聚体（3），然后是烯醇盐均二聚体（1-Li）（2），最后是烯醇盐四聚体（1-Li）（4），即平衡结构。对烯醇盐的亚稳二聚体和稳定四聚体的醛醇缩合反应进行了研究。两者都直接与醛反应，生成混合烯醇盐-醇醛缩合产物，在-120°C 时，二聚体的反应活性仅为四聚体的约 20 倍。
