Organic sulfur mechanisms. 20. Sulfenes from 1-haloalkanesulfinic acids: the 'abnormal route'

Abstract

1-Haloalkanesulfinic acids react with water, p-toluidine, or an enamine in the presence of added base to give products expected from an intermediate sulfene. It is concluded that sulfenes are formed, and hence may be presumed to react, via the 'abnormal route', i.e., loss of a nucleophile from the carbon (rather than the sulfur) of the incipient sulfene, or, for the reverse process, addition of a nucleophile to the carbon (rather than the sulfur) of the sulfene. Since addition at the sulfur is well precedented, these conclusions indicate that sulfene is an 'ambifunctional' electrophile of a previously unknown kind. The mechanism of the sulfene formation is discussed in the light of deuterium labelling and kinetic experiments.