Abstract A facile and highly stereoselective methodology for the preparation of highly functionalized trans-1,2-cyclopropanes containing benzoimidazolyl, cyano, aryl, and carbonyl groups 3 is described. Arsonium bromides 2 reacted with electron-deficient olefins 1 in the presence of KF·2H2O to provide 3 exclusively with high stereoselectivity in moderate to good yields.