Synthesis of 2-Aryl-3-sulfonylchromans via Knoevenagel Condensation and Reduction Protocol.

In this article, a concise, easy-operational, and high-yield method for the synthesis of 2-aryl-3-sulfonylchromans is described by two-step routes: (i) NH4OAc mediated Knoevenagel condensation of β-ketosulfones and o-hydroxybenzaldehydes in a cosolvent of toluene and THF at reflux for 10 h, and (ii) NaBH4 promoted regio- and stereocontrolled reduction of the resulting 2-arylchromen-2-ols in a cosolvent of MeOH and THF at rt for 1 h. This protocol provides a highly effective (4+2) annulation via one carbon-oxygen and one carbon-carbon bond formations.