An efficient and highly stereoselective synthesis of novel trifluoromethylated trans-dihydrofuro[2,3-c]pyrazoles using arsonium ylides

An efficient approach of highly stereoselective synthesis of novel trifluoromethylated trans-4,5-dihydrofuro[2,3-c]pyrazoles has been described. Arsonium bromides 1 reacted smoothly with the electron-deficient alkenes (Z)-4-aryl-1-phenyl-3-(trifluoromethyl)-1H-pyrozol-5(4H)-ones 2 to give products trans-dihydrofuro[2,3-c]pyrazoles 3 with high stereoselectivity and in good to excellent yields, using CH2Cl2 as solvent and K2CO3 as base.