W(CO)<sub>5</sub>(L)-Catalyzed Endo-Selective Cyclization of Allenyl Silyl Enol Ethers: An Efficient Method for the Cyclopentene Annulation onto α,β-Unsaturated Ketones
作者:Tomoya Miura、Koichi Kiyota、Hiroyuki Kusama、Kooyeon Lee、Hyunseok Kim、Sunggak Kim、Phil Ho Lee、Nobuharu Iwasawa
DOI:10.1021/ol034365a
日期:2003.5.1
undergo W(CO)(5)(L)-catalyzed 5-endo cyclization to give the corresponding cyclopentene derivatives in good yield. Furthermore, this novel W(CO)(5)(L)-catalyzed cyclization of allenyl silylenolethers proceeds in a 6-endo manner when 5-siloxy-1,2,5-trienes are employed as a substrate. In these reactions, effective electrophilic activation of allenyl compounds for attack by silylenolethers is achieved
[reaction: see text] On treatment of 5-siloxyhexa-1,2,5-trienes with a catalytic amount of W(CO)(6) under photoirradiation, formal Cope rearrangement proceeded to give 2-siloxyhex-1-en-5-ynes in good yield. The electrophilic activation of the allenyl moiety by W(CO)(5) triggers the intramolecular attack of the silyl enol ether in a 6-endo manner to produce a cyclohexenyl tungsten species. Carbon-carbon
a catalytic amount of W(CO)6 under photoirradiation, two types of synthetically useful compounds, that is, 6-endo-cyclized products or formal Cope rearrangement products, are obtained selectively via the same intermediates simply by changing reaction conditions. In these reactions, electrophilic activation of the allene moiety is effectively achieved by coordination of W(CO)5, allowing intramolecular