Huisgen, Rolf and Mayr, Herbert
Reactions of cyclobutenones with nucleophilic reagents via vinylketen intermediates.
In: Journal of the Chemical Society, Chemical Communications, No. 2: pp. 55-56
While strong nucleophiles add to the endocyclic double bond of cyclobutenones to yield cyclobutanones, weaker nucleophiles (e.g. alcohols, aniline) interact with the vinylketens which are thermally or photochemically generated from cyclobutenones; the alcohol adducts reveal the steric course of this ring opening which is virtually irreversible for phenylated and alkylated cyclobutenones.