Highly stereoselective synthesis of trans-4-trifluoromethylsulfonyl-2,3-dihydrofurans from arsonium ylides and (E)-α-trifluoromethylsulfonyl-α,β-unsaturated ketones

The reactions of arsonium bromides with (E)-α-trifluoromethylsulfonyl-α,β-unsaturated ketones in the presence of Cs2CO3 or K2CO3 proceeded smoothly under refluxing condition in dichloromethane (DCM) to give the corresponding trifluoromethylated trans-2,3-dihydrofurans in good to excellent yields with high stereoselectivity.