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.