Exploration of Unique Reactivity of Organotitanocene Complexes and Its Application to Organic Synthesis

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1.In the presence of triethyl phosphite, titanium carbene complexes generated by the reaction of thioacetals with a titanocene(II) species reacted with ethylene to produce terminal olefins with one carbon homologation. When the reaction was carried out in the absence of triethyl phosphite, terminal olefins with two more carbons were produced. The latter type reaction was also observed when the carbene complexes were treated with styrene derivatives.2.The reaction of the carbene complexes with vinyl pivalate selectively gave cyclopropanes via the intermediary cyclopropyltitanium species. Vinylcyclopropanes were also obtained by the reaction of carbene complexes with 1,3-dienes.3.The titanocene(II)-promoted inter-and intra-molecular reactions of thioacetals with anilides produced reductive alkylation products, acyclic and cyclic amines, respectively.4.The reaction of alkyl halides bearing a β-substituent with the titanocene(II) reagent produced titanium carbene complexes, yields of which … More were dependent on the bulkiness of β-substituent. These titanium reagents were successfully applied to the olefination of various carbonyl compounds. Similar carbonyl olefination utilizing an alkyl chloromethyl ether-titanocene(II) system gave a variety of enol ethers.5.The oxidative coupling of bis(phenylthio) methyltributylstannane with lithium alkoxides produced dithioorthoformates. Treatment of these compounds with the titanocene(II) species afforded alkoxymethylidenetitanocenes, which gave enol ethers on treatment with carbonyl compounds including carboxylic acid derivatives.6.The reaction of alkynylcarbene complexes, generated by the treatment of alkynyl thioacetals with the titanocene(II) reagent, with terminal olefins gave alkynylcyclopropanes. In the case of the reaction utilizing the alkynyl thioacetals having a trialkylsilyl group at α-position, the cyclopropanation regioselectively occurred at γ-position. Similarly the carbonyl olefination utilizing α-trialkylsilyl alkynyl thioacetals produced 1-trialkylsilylalk-3-en-1-ynes preferentially.7.The treatment of titanium carbene complexes generated from thioacetals with acetylene produced polyacetylene as free-standing conducting films. Less