Fluvenes and thermochromic ethylenes. Part LXVIII. The stereochemistry of the Wittig–Horner reaction with fulvenic and related ketones

Abstract

The Wittig–Horner reaction with asymmetrically substituted derivatives of 5H-dibenzo[a,d]cyclohepten-5-one, 10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-one, and thioxanthen-9-one has been shown to yield mixtures of two geometrical isomers. The isomers have not been isolated, but their presence has been proven by t.l.c, electric dipole moment measurements, and n.m.r. spectroscopy; the cis–trans ratios determined by these methods are 1 : 1 in the first and third cases, and 1 : 2 in the second.