The stereoselectivity of addition of benzoyloxyl radicals to cyclohexenes

Abstract

The reactions of benzoyloxyl radicals with cyclohexene and with 4-tert-butylcyclohexene, in the presence of the free radical scavenger 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl, are reported. The major reaction observed was diaxial addition; however, the diequatorial and axial/equatorial products were also significant. The overall ratio of axial to equatorial addition of benzoyloxyl radicals to the alkene was 3:2. The aminoxyl trapping reaction was more selective with a ratio of trans to cis addition of ca. 4:1. The stereoselectivity of the addition of benzoyloxyl radicals to cyclohexenes and of the trapping of cyclohexyl radicals is discussed in terms of steric and polar factors.