BACKSIDE ACTIVATION OF SIGMA(C-C)-BONDS WITH CR(VI)-REAGENTS

The transformations of stable propellanes 3,6-dehydrohomoadamantane (1 ) and 1,5- dehydrobicyclo[3.3.1]nonane (2) on treatment with chromyl o xidants in different solvents were studied. Hydrocarbon 1 with CrO2Cl2 in nonpolar solvents forms 3,6-dichloro- (3) and 3-chloro-6-hydroxy- (4) homoadamantanes in the course of backside oxidative addition to th e strained C-C bond and 3-oxobicyclo[3.3.1]nonane-7-spirocyclopropane (5) as a result of the oxidative cyclobutane ring contraction. CrO2(OA c)(2)/Ac2O and CrO2(OCOCF3)(2)/(CF3CO)(2)O result only in oxidative ad dition with the formation of the mixtures of the corresponding 6-hydro xy-3-acetates (7,9) and 3,6-diacetates (6,8). In the case of 2 the onl y oxidative addition takes place. Possible mechanisms of the backside oxidative addition to the C-C bond are discussed. (C) 1997, Elsevier S cience Ltd. All rights reserved.