Department of Organic Chemistry, Institute of Biotechnology, University of Granada, Avda. Fuentenueva, 18071 Granada, Spain.
J Am Chem Soc. 2010 Jan 13;132(1):254-9. doi: 10.1021/ja906083c.
Investigations detailed herein, including density functional theory (DFT) calculations, demonstrate that the formation of either alkoxy- or hydroxy-Ti(III) complexes considerably decreases the energy of activation for C-O bond homolysis. As a consequence of this observation, we described two new synthetic applications of Nugent's reagent in organic chemistry. The first of these applications is an one-step methodology for deoxygenation-reduction of alcohols, including benzylic and allylic alcohols and 1,2-dihydroxy compounds. Additionally, we have also proved that Ti(III) is capable of mediating carbonyl coupling-olefination. In this sense, and despite the fact that for over 35 years it has been widely accepted that either Ti(II) or Ti(0) was the active species in the reductive process of the McMurry reaction, the mechanistic evidence presented proves the involvement of Ti(III) pinacolates in the deoxygenation step of the herein described Nugent's reagent-mediated McMurry olefination. This observation sheds some light on probably one of the mechanistically more complex transformations in organic chemistry. Finally, we have also proved that both of these processes can be performed catalytically in Cp(2)TiCl(2) by using trimethylsilyl chloride (TMSCl) as the final oxygen trap.
本文中的研究，包括密度泛函理论（DFT）计算，表明烷氧基或羟基-Ti(III) 配合物的形成大大降低了 C-O 键均裂的活化能。由于这一观察结果，我们在有机化学中描述了 Nugent 试剂的两个新的合成应用。这些应用中的第一个是一种一步法脱醇还原醇的方法，包括苄基和烯丙基醇以及 1,2-二醇化合物。此外，我们还证明了 Ti(III) 能够介导羰基偶联-烯烃化。在这方面，尽管三十多年来人们普遍认为在 McMurry 反应的还原过程中，Ti(II) 或 Ti(0) 是活性物种，但提出的机理证据证明了 Ti(III) 频哪醇盐在本文所述的 Nugent 试剂介导的 McMurry 烯烃化中脱氧步骤的参与。这一观察结果为有机化学中可能更复杂的转化之一提供了一些线索。最后，我们还证明，这两种过程都可以在 Cp(2)TiCl(2) 中使用三甲基氯硅烷（TMSCl）作为最终的氧捕获剂进行催化。
