The preparation and type II intramolecular [4 + 4] cycloaddition of a bis-diene is described in connection with studies on the synthesis of taxol (1), crispolide (2), and vulgarolide (3). The required bis-diene is prepared by a carboalumination of an alkyne, giving an iodide which is then coupled in the presence of palladium to a vinyltin to give a stereodefined diene. Elaboration of this system involves the reaction of 2-lithio-1, 3-butadiene with a dienal to give a bis-1,3-diene tethered at the terminus of one diene and the internal position of the other. Cycloaddition of this bis-diene mediated by a nickel(0)/tri-o-biphenyl phosphite catalyst provides a bicyclo[5.3.1]undecadiene, a ring system common to a variety of complex molecules.
本文描述了一种二
烯的制备及其类型 II 分子内 [4 + 4] 环加成,涉及
紫杉醇(1)、脆朊醇(2)和普通醇(3)的合成研究。所需的二
烯通过
炭铝合成法从
炔烃制备,得到的
碘化物随后在
钯的存在下与
乙烯锡偶联,形成立体定义的二
烯。该体系的进一步转化涉及2-
锂-
1,3-丁二烯与一个二
烯醛反应,生成一个双1,3-二
烯,该
双烯在一个二
烯的末端和另一个的内部位置上连接。通过
镍(0)/三-o-
苯基
磷酸盐
催化剂催化的该
双烯的环加成反应生成了一个双环[5.3.1]十一
烯,这是一种在多种复杂分子中常见的环系。