A Divergent and Selective Synthesis of Isomeric Benzoxazoles from a Single N–Cl Imine
作者:Cheng-yi Chen、Teresa Andreani、Hongmei Li
DOI:10.1021/ol202844c
日期:2011.12.2
divergent and regioselective synthesis of either 3-substituted benzisoxazoles or 2-substituted benzoxazoles from readily accessible ortho-hydroxyaryl N–H ketimines is described. The reaction proceeds in two distinct pathways through a common N–Cl imine intermediate: (a) N–O bond formation to form benzisoxazole under anhydrous conditions and (b) NaOCl mediated Beckmann-type rearrangement to form benzoxazole
was found to act as an efficient oxidant to trigger the [1,2]-arylmigration towards the formation of the desired heterocycles. Depending on the substitution pattern, the results revealed another mechanistic pathway through which benzisoxazoles or 1H-indazoles could be formed. The Beckmann-type rearrangement strategy was applied to the synthesis of benzimidazole-containing biorelevant targets such as
by employing in situ generated BF3·H2O as fluoroboron souce and afforded a series of novel species of N,O π-conjugated boron complexes. Moreover, we achieved the Suzuki cross-coupling reaction of iodo-substituted complex with different boronic acids to further expand the structural diversity of N,O π-conjugated fluoroboron complexes.