Síntese de derivados de benzo[b]furanos via dupla ciclização intramolecular promovida por t-BuOK

Abstract

In this work, we reported the developed study for the preparation of substituted benzo[b]furans via double anionic intramolecular cyclization process promoted by t-BuOK. Firstly, a variety of 5H-benzo[d]benzofuro[3,2-b]azepines 2 was prepared by the reaction of 2-((2- ethynyl)benzyloxy)benzonitriles 1 with a catalytic amount of t-BuOK (Equation 1). Subsequently, the aryldiynes 3 were subjected to carbocyclization reaction promoted by t- BuOK, which allowed the synthesis of 5aH-benzo[4,5]cyclohepta[1,2-b]benzofurans 4 in good yields (Equation 2). Both methodologies proceeded selectively through a 5-exo-dig intramolecular cyclization followed by a 7-endo-dig cyclization furnishing the benzo[b]furans in a one pot procedure.