Intramolecular Cyclization of 2,7- or 2,8-Bis-unsaturated Esters Mediated by (η<sup>2</sup>-Propene)Ti(O-<i>i</i>-Pr)<sub>2</sub>. Facile Construction of Mono- and Bicyclic Skeletons with Stereoselective Introduction of a Side Chain. A Synthesis of <i>d</i>-Sabinene
作者:Hirokazu Urabe、Ken Suzuki、Fumie Sato
DOI:10.1021/ja9716160
日期:1997.10.1
tert-Butyl 2-en-7-ynoate 6 was treated with (η2-propene)Ti(O-i-Pr)2 (3), generated in situ from Ti(O-i-Pr)4 or Ti(O-i-Pr)3Cl and i-PrMgCl, in ether at −50 to −20 °C to afford the product 8 in good yield. The presence of the intermediate titanabicycle 7 was verified by bis-deuterolysis with excess D2O. When the titanabicycle 7 was treated with 1.1 equiv of i-PrOD and then worked up as usual, the monodeuterated
叔丁基 2-en-7-ynoate 6 用 (η2-propene)Ti(Oi-Pr)2 (3) 处理,由 Ti(Oi-Pr)4 或 Ti(Oi-Pr)3Cl 和i-PrMgCl,在-50至-20°C的乙醚中以良好的产率提供产物8。中间体钛双环 7 的存在通过用过量 D2O 进行双氘分解来验证。当钛双环 7 用 1.1 当量的 i-PrOD 处理然后照常处理时,得到了具有高位点选择性和立体选择性的单氘化产物 10。其他亲电子试剂如醛和酮也以高度立体选择性的方式与钛双环反应,得到具有立体定义侧链的环戊烷。相反,在相同条件下用 3 处理相应的乙酯,8-(三甲基甲硅烷基)-(E)-2-辛烯-7-炔酸乙酯(28),然后加入 1。1当量的s-BuOH以80%的产率提供2-(三甲基甲硅烷基)-1-双环[3.3.0]辛烯-3-一(32)。用 i-PrOD、EtCHO 和 Et2CO 代替 s-BuOH 淬灭相同的反应混合物