The effect of base concentration on orientation in E2 reactions: A common feature in metal alkoxide promoted olefin formation from alkyl halides and tosylates

Abstract

The title effect has been investigated in the reactions of three 2-butyl (X = I, Br, OTs) and four 2-decyl (X = I, Br, Cl, OTs derivatives with t-C4H9OK/t-C4H9OH, t-C4H9OK/tetrahydrofuran and t-C4H9ONa/t-C4H9OH as the base-solvent system. It has been found that a gradual increase of base concentration induces marked changes in positional as well as geometrical orientation by simultaneously increasing the 1-alkene/2-alkene and cis-2-alkene/trans-2-alkene ratios. The variations in orientation observed for the different substrates and/or base-solvent combinations are very similar. Concentration-dependent competition of dissociated and associated alkoxide species in the reaction or concentration-dependent solvation of leaving group by metal alkoxides are proposed to account for the changes in orientation.