Syntheses of 2-Benzylbenzofuran Derivatives and 2-Aryl-nitrochroman Derivatives from Nitroalkene Precursors

Simple and straightforward methods for the synthesis of 2-benzylbenzofuran, 3-substituted 2-benzylbenzofuran, and 2-aryl-nitrochroman derivatives are described. Benzofurans were generated from nitroalkenes by reduction with NaBH₄ followed by a Nef reaction and acid-mediated cyclization, whereas 3-substituted 2-benzylbenzofurans were prepared from nitroalkenes by reactions with Grignard reagents followed by a Nef reaction and an acid-mediated cyclization in a one-pot process. The synthesis of chromans involved a Knoevenagel condensation and the 1,4-diazabicyclo[2.2.2]octane (DABCO) assisted cyclization of β-(2-hydroxyphenyl)-nitroethanes and benzaldehydes, also in a one-pot process. Simple and convenient methods for the synthesis of 2-benzylbenzofuran, 3-substituted 2-benzylbenzofuran, and 2-aryl-nitrochroman derivatives are described.