The olefination of ketones using the organotitanium species formed from Cp 2Ti[P(OEt) 3] 2 and polychloromethane was studied. The reaction of the organotitanium species prepared from carbon tetrachloride with ketones produced the 1,1-dichloro-1-alkenes in good yields even when dialkyl ketones were employed. The similar olefination of ketones using chloroform afforded the 1-chloro-1-alkenes and 1,1-dichloro-1-alkenes, the ratio of which reflected the steric demand on the ketones. The titanocene chloromethylidene complex was suggested to be an active species of the reaction on the basis of the results obtained by the reaction using chloroform- d.