Synthesis of Chromenes by Cyclizative Condensation of Phenols with alpha,beta-Unsaturated Carbonyl Compounds over Halide Cluster Catalysts

摘要

When phenols were reacted with alpha,beta-unsaturated carbonyl compounds in a He stream over a silica gel-supported niobium halide cluster with an octahedral metal framework, [(Nb6Cl12)Cl-2(H2O)(4)]center dot 4H(2)O, at 200-350 degrees C, the catalytic activity of the cluster for cyclizative condensation developed to yield the corresponding chromenes selectively. The reaction can be seen as a substantial extension of Dobner-von Miller quinoline synthesis using phenol instead of aniline. The halide clusters of tantalum and tungsten also catalyzed the reaction.