Halogenated Ketenes. 36. Reactions of Chloroketenes with Ketene Acetals

Article abstract of DOI:10.1021/jo00333a022

The products of the reactions of ketenes and ketene acetals are dependent upon substitution in the ketene acetals.Dichloroketene reacts with dimethylketene dimethyl acetal to regiospecifically yield the cyclobutanone.The reaction of methylchloroketene and ketene diethyl acetal yields an acyclic product, an acylketene acetal.Chloro-, dichloro-, and methylchloroketenes react with O-silylated ketene acetals to yield acyclic unsaturated esters.Dichloroketene reacts with the acylketene acetal, (α-chloropropionyl)ketene diethyl acetal, to yield a (4 + 2) cycloaddition product, a δ-lactone.All of these results are consistent with a two-step process involving a dipolar intermediate.