Cyclopropyl activation of adjacent methylene groups in spiro[2.n]alkanes and bicyclo[n.1.0]alkanes

Abstract

The hydrogens at C(2) in spiro[2.n]alkanes are abstracted above five times more rapidly than ‘normal’ secondary hydrogens by t-butoxyl radicals, because of favourable overlap of the p-orbital at C(2) with the HOMO of the adjacent cyclopropyl ring; the hydrogenes at C(2) in bicyclo[n.1.0]alkanes are less activated because the cyclopropyl ring orientation is less favourable for overlap.