Substituent-Controlled Electrocyclization of 2,4-Dienones: Synthesis of 2,3,6-Trisubstituted 2H-Pyran-5-carboxylates and Their Transformations
作者:Wei Peng、Toshiaki Hirabaru、Hiroyuki Kawafuchi、Tsutomu Inokuchi
DOI:10.1002/ejoc.201100780
日期:2011.10
A facile access to 2,3,6-trisubstituted 2H-pyran-5-carboxylates is developed by employing 2-alkyl-2-enals as reactants with acetoacetates. The reaction involves Knoevenagel condensation followed by a 6π-electrocyclization, in which the presence of the C2 alkyl substituent in the enals favors the formation of (E)-Knoevenagel adducts for the ensuing electrocyclization. The resulting 2H-pyrans are hydrogenated
通过使用 2-烷基-2-烯醛作为与乙酰乙酸酯的反应物,可以轻松获得 2,3,6-三取代的 2H-吡喃-5-羧酸酯。该反应涉及 Knoevenagel 缩合,然后是 6π-电环化,其中烯醛中 C2 烷基取代基的存在有利于形成 (E)-Knoevenagel 加合物,用于随后的电环化。所得的 2H-吡喃被氢化形成 3,4-二氢-2H-吡喃并通过单线态氧环加成转化为内过氧化物。