Prototropy of 2-methyl-1,3-diphenylpropenes. Stability of the intermediary carbanions

Abstract

The prototropy of 2-methyl-1,3-diphenylpropenes under basic catalysis has been studied. The free energy of the carbanions generated from the substrate increases in the order trans–trans > trans–cis, indicating that the [1,2] interactions of the carbanion are dominant. This result is in contrast with the stability order found for related systems; the disagreement has been ascribed to the presence of the 2-methyl group.