On the mechanism of a new dihalocyclopropane‐dihalomethyl vinyl rearrangement

Abstract

A tentative mechanism for a new dihalocyclopropane-dihalomethyl vinyl rearrangement is discussed following some isotopic labelling and substituted cyclohexene studies on fused cyclohexene-cyclopropane (norcarane) compounds.

On a novel dihalocyclopropane– dihalomethylvinyl rearrangement:Additional mechanistic evidence

“…In our last study [2], we discussed the three most plausible mechanistic pathways and concluded that, under Hiyama conditions, the overall results tend to indicate the absence of the ionic intermediates.…”

“…In our previous two papers, we have shown that this rearrangement proceeds via a unique pathway of a Hiyama-like system, where the presence of two neighbouring oxidation state metal cations is necessary [1,2]. This reaction did not follow the Makosza pathway of ring extension, which would lead, in the case of for example bicyclic compounds such as cis-fused 7,7-dichlorocarenes (1) (with gem-dichlorocyclopropane ring condensed on the cyclohexane frame), to halogenated cycloheptene (3) compounds [3,4].…”

“…The reaction could also be used as another way to obtain α, β-unsaturated aldehydes or acids, and in that respect is one more method of synthesis of alpha, beta-unsaturated carbonyl compounds from various unactivated olefins. Under rigorously controlled hydrolytic conditions, we were able to halt the reaction at the aldehyde stage [2,8]. In some cases allenic structures are also available.…”

Recent advances in the syntheses, transformations and applications of 1,1-dihalocyclopropanes

“…86,87 Here, the reaction proceeds via a biradical mechanism involving Cr intermediate and the mechanistic study was performed by isotopic labeling. 86,87 Here, the reaction proceeds via a biradical mechanism involving Cr intermediate and the mechanistic study was performed by isotopic labeling.…”

“…A detailed mechanistic study of the rearrangement of both exocyclic and endocyclic dihalocyclopropane to cyclohexene was also reported. 86,87 Here, the reaction proceeds via a biradical mechanism involving Cr intermediate and the mechanistic study was performed by isotopic labeling. Under acidic conditions in the presence of Cr 2+ /Cr 3+ , dihalocyclopropanes generate a dihalomethyl vinyl derivative; the existence of the latter was presumed since a mixture of α,β-unsaturated aldehyde and acid along with dehalogenated products were isolated from the reaction mixture (Scheme 55).…”