Preparation of [2,5-Diisopropylcyclohexane-1,4- bis(indenyl)]titanium Dichloride and [2,5-Diisopropylcyclohexane-1,4-bis(tetrahydroindenyl)]- titanium Dichloride and Their Comparison as Catalysts for

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• 作者：Ronald L. Halterman ; Chengjiang Zhu ; Zhouliang Chen ; Melinda S. Dunlap ; Masood A. Khan ; and Kenneth M. Nicholas
• 刊名：Organometallics
• 出版年：2000
• 出版时间：September 18, 2000
• 年：2000
• 卷：19
• 期：19
• 页码：3824 - 3829
• 全文大小：145K
• 年卷期：v.19,no.19(September 18, 2000)
• ISSN：1520-6041

文摘

The nonracemic bis(indene) (+)-(1R,2R,4R,5R)-1,4-bis(3'-indenyl)-2,5-diisopropylcyclohexane (10) was synthesized in 60% yield from the addition of indenyllithium to thecorresponding bis(methanesulfonate) ester of 2,4-diisopropyl-1,4-cyclohexanediol. Deprotonation of bis(indene) 10 with n-BuLi followed by metalation with TiCl₃ and oxidative workup(HCl, air, chloroform) gave the single stereoisomeric 2,5-diisopropylcyclohexane-1,4-diyl-bridged bis(indenyl)titanium dichloride 3 in 80% yield. Attempts to form the correspondingbis(indenyl)zirconium dichloride were unsuccessful. Catalytic hydrogenation of bis(indenyl)titanium dichloride 3 gave the 2,5-diisopropylcyclohexane-1,4-diyl-bridged bis(tetrahydroindenyl)titanium dichloride 4 in 76% yield. The solid-state structure of 4 was determined byX-ray crystallographic methods. Nonracemic mixtures of chiral bis(indenyl)titanium dichloride 3 and bis(tetrahydroindenyl)titanium dichloride 4 were examined as catalysts for thepinacol coupling of benzaldehyde in the presence of manganese metal. The enantioselectivitiesfor dihydrobenzoin were 0% with bis(indenyl) 3 and 32% with bis(tetrahydroindenyl) 4 togive the first comparison of enantioselectivities with corresponding bis(indenyl) and bis(tetrahydroindenyl) complexes.