Abstract
Allylic cyclobutanols 1,10, 21,27,32,39, 51, and 58 are oxidatively fragmented by Mn(0Ac)a-2H20 in EtOH to give tertiary radicals as shown in eq 1. These tertiary radicals undergo both 6-endo-cyclization to the ,ß-unsaturated ketone to afford -keto radicals and 5-exo-cyclization to provide d-ketocyclopentylmethylradicals. The -ketoradicalsproducedby6-endo-cyclizationare reduced to ketones or dimerize. The j8-keto radicals formed by 5-exo-cyclization are oxidized by Cu(OAc>2 to yield methylenecyclopentanones and rearrange to give 3-oxocycIohexyl radicals that are oxidized by Cu(OAc>2 to afford cyclohexenones. Acetylenic cyclobutanols 47, 49, and 65 are oxidatively fragmentedbyMn(0Ac)3-2H20inEtOHtoprovidetertiaryradicalsthatcyclizetogive -ketovinyl radicals, which abstract a hydrogen atom to yield methylenecyclopentanones. Pentenylcyclobutanol 75 is oxidatively fragmented by Mn(0Ac)3*2H20 to afford tertiary radical 74, which cyclizes to furnish cyclopentylmethyl radicals 77 and 78, which are
76 and 79.