1,1-Diphenylalkenes. Part II. Alkylation of 1,1-diphenylpropene carbanions. The principle of least motion

Carbanions of the type [Ph2CCHCHR]– were alkylated in liquid ammonia. A preponderance of α-alkylation occurred when R was H or Me, in accord with the principle of least motion. Contrary to predictions, exclusive α-alkylation occurred when R was Ph. The mechanism and synthetic utility of these reactions are discussed.