Synthesis of benzoxepinopyrrolidines/spiropyrrolidines via oxa-Pictet-Spengler and [3+2] cycloaddition reactions

A convenient one-pot synthesis of 2-benzoxepines generated from (E)-2-nitro-3-arylprop-2-en-1-ols with paraformaldehyde via oxa-Pictet-Spengler cyclization is described. Furthermore, the 1,3-dipolar cycloaddition of 2-benzoxepines with azomethine ylides using isatin/paraformaldehyde led to the formation of tricyclic benzoxepinopyrrolidine and pentacyclic benzoxepinospiropyrrolidine oxindole architectures for the first time.