Effect of remote heteroatom substituents on stereochemistry in 1,2 h migration to divalent carbon. Evidence for “negative” hyperconjugation of carbene lone pair
Aryloxymethylchlorocarbene generated by photolysis of the corresponding diazirine afforded α-aryloxy-β-chloroalkene. The thermodynamically less stable Z-products are the major isomers and its content becomes dominant as more electron-withdrawing groups are introduced on phenyl ring.