Electrostatic Control of Regioselectivity in Competing Biomolecular Eliminations

Article abstract of DOI:10.1021/jo00216a017

The isomeric trans-11,12-dichloro-9,10-dihydro-9,10-ethano-1-anthroic acids (1 and 2) have been prepared and characterized.Base-induced dehydrochlorinations of these and the corresponding cis-dichloroethano derivatives 3 and 4 were conducted under several sets of base/solvent conditions.Preparations and dehydrochlorinations of 2-ethanoic acid (15) and the corresponding cis-dichloro isomer 16 are also reported.Regioselectivities in vinyl halide formations are highest with K⁺O^--t-Bu/t-BuOH/18 crown-6, conditions under which ion aggregation is minimized.The results of these studies indicate that both the syn and quasi-anti eliminations possess some carbanionic character but with most of the charge remaining on the attacking base in the transition states.