Ring expansion reactionsvia endocyclic cleavage of cyclopropylcarbinyl radicals

Cleavage of cyclopropyl ketones mediated by alkylmercury(ii) hydridesA preliminary account of part of this work was presented at the 12th National Symposium of Organic Chemistry (XII SINAQO), Córdoba, Argentina, November 1999. Abstract published in Molecules (online computer file), 2000, 5, 447.Electronic supplementary information (ESI) available: UHF/6-31G**-calculated structures, spin-density surfaces, cartesian coordinates, total atomic spin densities and Fermi-contact data for simplified models of radi

“…1b), the latter being regioselectively cleaved. Recently it has been argued that exocyclic cleavage can be avoided in bicyclo[n.1.0] radicals (n = 3-5), 14 although this was accomplished by introduction of a benzyloxycarbonyl substituent on the cyclopropane ring that stabilized the incipient radical in the endo-cleavage transition state. 15 In our case, the cleavage of radical 20, derived from 10a, exemplifies stabilization by a phenyl group (Fig.…”

“…0.5 h). The reaction mixture was filtered, diluted with water (150 cm 3 ), and extracted with dichloromethane to give enol acetate 9 (2.03 g, 88%), ν max (KBr)/cm Ϫ1 (5), 123 (49), 109 (14), 83 (9), 69 (14), 55 (21), 43 (100).…”

Novel methods for the synthesis of three-, four-, five-, six- and seven-membered, saturated and partially unsaturated carbocycles

“…203 Similarly, radicals generated from thiocarbamates 367 rearrange to give six-, seven-and eight-membered carbocycles 368 in good yield (Scheme 158). 204 1-(Trimethylsilyloxy)bicyclo[n.1.0]alkanes 369 and bicyclo-[n.1.0]alkanols 370 react with a catalytic amount of vanadyl acetylacetonate under an oxygen atmosphere to afford six-, seven-and eight-membered β-hydroxyketones 371 and β-diketones 372 in 55-85% yield (Scheme 159). 205…”