CYCLIZATION BY AN INTRAMOLECULAR ALLENE INSERTION INTO π-ALLYLIC PALLADIUMS AND BY CARBONYLATION

在以乙酸为溶剂的π-烯丙基钯中间体分子内插入烯烃的环化反应研究中，我们还发现了以乙酸烯丙酯为底物的丙二烯环可以进行钯（0）催化的多米诺式插入和羰基化反应，环化在区域选择性和立体选择性方面都受到高度控制：I. E、由具有丙二烯对应物的某些乙酸烯丙酯与钯（0）催化剂在一氧化碳气氛下氧化加成形成的π-烯丙基钯中间体经历容易的丙二烯插入，（五元环）σ-乙烯基钯中间体或另一种π-烯丙基钯中间体，其也构成五元环体系，后两种中间体之后是羰基化，得到具有羰基官能团的五元稠环体系。作为最近的研究结果之一，我们以5-烯基-1，6，7-辛三烯酯为起始原料，通过钯（0）催化的连续（多米诺）插入-羰基化反应，以可观的产率制备了一个四环稠合的五元环体系，如5-烯基-1，6，7-辛三烯酯，（3-丁烯基）-5-甲基-1，6，7-辛烯-3-基乙酸酯和5，8-二甲基-5-（1，2-丙二烯基）-2，8-壬二烯基乙酸酯。值得注意的是，本发明的催化反应在一次操作中产生六个碳-碳键。尝试通过本发明的多米诺骨牌式环化-羰基化并伴随引入角甲基的方式来进行Capnellene和相关Capnellenol（三环倍半萜之一）的短步骤合成。

On a line of research program of the cyclization strategy which rely on an intramolecular alkene insertion into π-allylic palladium intermediate in acetic acid as a necessary solvent, we have also found the palladium(0)-catalyzed, domino-type insertion and Carbonylation to take place by the use of an allene moiety tethered with an allylic acetate as the substrate, the cyclization being highly controlled in terms of both regio- and stereoselectivity : I. E., the π-allylic palladium intermediate, formed from oxidative addition of certain allylic acetate having an allene counterpart with palladium(0) catalyst under a carbon monoxide atmosphere, undergoes facile allene insertion to give either cyclized (five-membered ring) σ-vinylic palladium intermediate or another π-allylic palladium intermediate, which constitutes also a five-membered ring system, the latter two intermediates being followed by carbonylation, to afford five-membered condensed ring systems with carbonyl functionalities. Thus, the strategy provides a unique procedure for condensed polycycles.As one of recent results, we have prepared a four-ring-condensed five-membered ring systems in an appreciable yield by the palladium(0)-catalyzed successive (domino) insertion-carbonylation staring from 5-alkenyl-1, 6, 7-octatrienyl esters, such as 5-(3-butenyl)-5-methyl-1, 6, 7-octarien-3-yl acetate and 5, 8-dimethyl-5-(1, 2-propadienyl)-2, 8-nonadienyl acetate. It is worthy of note that the present catalytic reaction creates six carbon-carbon bonds in one operation. An attempted shortstep synthesis of capnellene and related capnellenol, one of tricyclic sesquiterpenes, as undertaken by way of the present domino-type cyclization-carbonylation with concomitant introduction of an angular methyl group.