|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1991 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1990 : ¥1,700,000 (Direct Cost : ¥1,700,000)
The development of highly stereoselective and catalytic reactions has syntheses of natural products, pharmaceuticals, and other useful materials. Metallocenes such as titanocene dichloride and zirconocene dichloride have been used as a catalyst for polymerization (Zieglar-Natta catalyst), carbonetallation, and hydrogenation. Since metaflocenes have two sterically demanded ligands of cyclopentadenyl group, inmkuction of chirality on metahocenes may bring high asymmetric induction in the metallocene catalyzed reactions. Some optically active metahocenes whose substituted cyclopentadienyl groups were connected with alkylene chain had already been prepared by optical resolution. However, prior introduction of chirality into the alkylene chain of metallocenes seemed to eliminate the troublesome resolution step and to open an opportunity for the synthesis of various Kinds of optically active metahocenes.
The chiral alkylene chains were prepared from easily available (2S, 3S)-diethyl tartrate,
(S)-ethyl lactate, (S)-1, 3-butanediol, (2S, 3S)-2, 3-butanediol, (2S, 4S)-2, 4-pentanediol. On the other hand, indenyl group was employed as the substituted cyclopentadienyl part due to its higher chemical stability than ordinary'alkylcyclopentadienes. Then, several o]fftically active diindenyl ligands were synthesized by coupling of the two parts. Next complexation of the ligands with titanium or zirconium tetrachloride was found to be difficult and complex decomposition products were obtained in almost every case. After numerous experimentations, two crystalline titanocenes were produced by a treatment of titanium tetrachloride with (R)-1, 3-di(1 -indenyl) butane or (2R, 4R)-2, 4-di(l-indenyl) pentane and subsequent hydrogenation in 9-1 1% yield. The structure elucidation revealed that the crystalline products were eclipsed complex whose substituent arranged to same direction. Disappointingly, highly asymmetric induction could not be expected in the eclipsed complex catalyzed reaction. Quite recently, R. L. Halterman et al. reported a synthesis of optically active titanocene having binaphthyl axial asymmetry on the alkylene chain [Organometallics, 10, 2998(1991)]. Since it is not clear a reason for the difference between our result and Halterman's result at present, further experimentations are required. Less