Synthesis of Medium-Sized Bicyclic Compounds by Intramolecular Cyclization of Cyclic β-Keto Radicals Generated from Cyclopropanols Using Manganese(III) Tris(2-pyridinecarboxylate)

Bicyclic cyclopropanols having olefinic side chain are oxidized with Mn(pic)3 to generate cyclic β-keto radicals with ring-expansion, which cyclize intramolecularly affording bicyclic radical intermediates. The cyclized radicals are trapped with various radical-trapping reagents such as electron-rich or -deficient olefins, tributyltin hydride and diphenyl diselenide to give the corresponding functionalized products.