Preparation of medium-sized ring trans-cycloalkene derivatives from halogenocyclopropane intermediates by silver perchlorate-promoted solvolysis

Abstract

8,8-Dibromobicyclo[5.1.0]octane (8c), 9,9-dibromobicyclo[6.1.0]nonane (9c), and 9,9-dibromobicyclo[6.1.0]-non-4-ene (19a) readily undergo ring expansion in the presence of high concentrations of silver perchlorate to give, in methanol solution, the corresponding trans-cycloalkenyl ethers [(11a), (13a), and (20a), respectively] and, in aqueous acetone solution, the corresponding trans-cycloalkenols [(11b), (13b), and (20b), respectively] in high yields. The dichloro-compounds (8d), (9d), and (19b) undergo silver perchlorate-promoted methanolysis and hydrolysis in the same way. Compounds (8c), (8d), (19a), and (19b) all undergo stereospecific solvolysis to give only one of two possible diastereoisomers. exo-8-Bromobicyclo[5.1.0]octane (8a) and exo-9-bromobicyclo-[6.1.0]nonane (9a) rapidly undergo silver perchlorate-promoted methanolysis and hydrolysis to give the respective trans-cycloalkenyl ethers [(6b) and (7b)] and trans-cycloalkenols [(6c) and (7c)] in high yields; their endo-isomers are solvolysed much less readily to give the corresponding cis-isomers in lower yields. The silver perchlorate-promoted solvolysis of 10,10-dibromo-, exo-10-bromo-, and endo-10-bromo-bicyclo[7.1.0]decanes [(10c), (10a), and (10b), respectively] are also described. The main products of silver perchlorate-promoted solvolysis of 5,5,10,10-tetrabromotricyclo[7.1.0.0^4,6]decane (21) are trans,trans-cyclodeca-1,6-diene derivatives. The interconversion of the diastereoisomers of the above 3-substituted trans-cyclo-octene, -cyclononene, and -cyclodecene derivatives is discussed.