Base-Mediated Cyclocondensation of Salicylaldehydes and 2‑Bromoallyl Sulfones for the Synthesis of 3‑Sulfonylchromene Derivatives and Their Regioselective Friedel–Crafts Heteroarylation Reactions

Cesium carbonate-mediated reaction of 2-hydroxybenzaldehydes and 2-bromoallyl sulfones afforded 2H- and 4H-chromenol derivatives endowed with a 3-arylsulfonyl group. 2-Bromoallyl sulfones functioned as synthetic equivalents of allenyl sulfones under these conditions. The 2H- and 4H-chromenol derivatives underwent regioselective Friedel–Crafts reactions with heteroarenes in the presence of p-toluenesulfonic acid to afford 4-heteroaryl-4H-chromene derivatives in excellent yields.