Reductive Coupling of Terpenic Allylic Halides Catalyzed by Cp2TiCl: A Short and Efficient Asymmetric Synthesis of Onocerane Triterpenes
摘要:
Titanocene chloride catalyzes the regioselective alpha,alpha '-homocoupling of terpenic allylic halides. This process has been employed in the short and effective synthesis of terpenoids such as beta-onoceradiene (1), beta-onocerin (2), and squalene (3). Evidence is presented for eta(1)-allyltitanium species being involved in the coupling.