|Budget Amount *help
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 1999 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1998 : ¥2,500,000 (Direct Cost : ¥2,500,000)
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.