Unexpected switch in regioselectivity of tether-directed Bingel-type biscyclopropanations depending on the leaving groups at tethered active ethylene moieties

The regioselectivity of tether-directed Bingel-type biscyclopropanations of 60]fullerene was switched depending on the leaving groups at tethered active methylene moieties; the reactions of 60]fullerene with unhalogenated tethered bis(active methylene) derivatives/I2 and with brominated derivatives in the presence of 1,7-diazabicyclo5.4.0]undec-7-ene gave trans-4-adducts predominantly, while the reactions with chlorinated derivatives afforded equatorial-adducts almost exclusively.