HALOGENATED KETENES .31. CYCLOADDITION OF DICHLOROKETENE WITH HINDERED OLEFINS

The cycloaddition of dichloroketene with tri-and tetrasubstituted ethylenes and other unreactive olefins utilizing an improved procedure has been accomplished. This procedure involves the preparation of dichloroketene by the zinc dechlorination of trichloroacetyl chloride in the presence of the olefins. The reactive ketene is formed so as to deter polymerization of the ketene in favor of cycloaddition. Dichloroketene has been added to 2, 3-dimethyl-2-butene, 1-methylcyclohexene, 2-methyl-2-butene, 2, 5-dimethyl-2, 4-hexadiene, α-pinene, and 5-methylene-2-norbornene. The yields for the cycloaddition of dichloroketene with cyclohexene, 1-pentene, and norbornene have been significantly improved. The cycloaddition of chloroketene with 2-methyl-2-butene and 2, 3-dimethyl-2-butene has been accomplished in a similar manner. The reductive removal of the chlorine atoms from several of the 2, 2-di-chlorocyclobutanones with tri-n-butyltin hydride or zinc and acetic acid is also reported. © 1979, American Chemical Society. All rights reserved.