Reaction of organotitanium species prepared from gem-dihalides and titanocene(II)

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Development of the new synthetic reactions utilizing organotitanium reagents prepared by the reaction of gem-dihalides with titanocene(II) species were studied. The carbonyl olefination using a gem-Dichloride-CpィイD22ィエD2Ti[P(OEt)ィイD23ィエD23]ィイD22ィエD2 System, transformation of ketones into 1-chloro and 1,1-dichloro-1-alkenes, and titanocene(II)-promoted cyclization of gem-dihalides having a terminal olefin moiety were examined and following results were obtained.1. Synthesis of tetrasubstituted olefins by the titanocene(II)-promoted olefination of carbonyl compounds using gem-dichlorides .... The organotitanium species prepared from gem-dichlorides and CpィイD22ィエD2Ti[P(OEt)ィイD23ィエD23]ィイD22ィエD2 reacted with ketones and carboxylic esters to afford tetrasubstituted olefins and trisubstituted enol ethers in good yields, respectively.2. Synthesis of 1-chloro and 1,1-dichloro-1-alkenes .... The reaction of the organotitanium species prepared from carbon tetrachloride with ketones produced the 1,1-dichloro-1-alkenes in good yields. The similar olefination of ketones using chloroform afforded the 1-chloro-1-alkenes and 1,1-dichloro-1-alkenes, the ratio of which refracted the steric demand on the ketones.3. Titanocene(II)-promoted cyclization of gem-dihalides having a terminal olefin moiety .... The bicyclo[n.1.0] derivatives were produced by the simple treatment of the gem-dihalides having a terminal olefin moiety with CpィイD22ィエD2Ti[P(OEt)ィイD23ィエD23]ィイD22ィエD2 in good yields. This result suggested that the organotitanium species generated by the reaction of gem-dihalide with CpィイD22ィエD2Ti[P(OEt)ィイD23ィエD23]ィイD22ィエD2 was different from the one prepared from thioacetal. This cyclization may proceed through gem-dititanium species.