Solvent effects in copper(I)-mediated 5-endo cyclisation of secondary bromo-enamides

摘要

Secondary bromoenamides 5,14-18, 32 and 33 undergo efficient 5-endo cyclisation reactions to give #alpha#, #beta#-unsaturated monoene lactams 9, 19-23, 34 and 35 under atom transfer conditions mediated by CuBr and the tripyridylamine 6 in refluxing toluene (59-87%). Changing the solvent to refluxing 1,2-dichloroethane furnishes #alpha#, #beta#-unsaturated diene lactams 26-31, 36 and 37 insted (42-86%).