Overcrowded molecules. Part VIII. Addition of diphenylketen to (Z)-2-benzylidene-3-diphenylmethylene-2,3-dihydro-5-methylbenzofuran

Abstract

Diphenylketen, through its carbonyl double bond, adds to the 1,4-positions of the conjugated diene. (Z)-2-benzylidene-3-diphenylmethylene-2,3-dihydro-5-methylbenzofuran, to give the vinyl ether, 3-diphenylmethylene-3,4-dihydro-8-methyl-1,1,4-triphenyl-1H-pyrano[4,3-b]benzofuran (7; X = O, R = Me). The mechanism of this unusual keten–diene reaction is discussed.