title: Tungsten(0)- and rhenium(I)-catalyzed tandem cyclization of acetylenic dienol silyl ethers based on geminal carbo-functionalization of alkynes.
abstract: Tungsten(0)- and rhenium(I)-catalyzed reactions of acetylenic dienol silyl ethers based on the concept of geminal carbo-functionalization of alkynes are reported. Treatment of 3-siloxy-1,3-diene-7-ynes with catalytic amounts of [W(CO)(6)] or [ReCl(CO)(5)] under photoirradiation conditions gives synthetically useful bicyclo[3.3.0]octane derivatives in good yields. Extremely high catalytic activity is noted for the rhenium(I) complex. The reaction has been extended to substrates containing a nitrogen atom in their tethers. In this case, two kinds of synthetically useful heterocyclic compounds-the 2-azabicyclo[3.3.0]octane derivatives 9 and the monocyclic dihydropyrroles 10, with allenyl substituents-are obtained, and selective preparation of either product can be achieved through the use of an appropriate combination of the nitrogen substituent and the type of the rhenium(I) catalyst. The 2-azabicyclo[3.3.0]octane derivatives 9 are obtained selectively by carrying out treatment of N-Ns derivatives in the presence of [ReCl(CO)(4)(PPh(3))], whereas the dihydropyrrole derivatives 10 are obtained by treatment of N-Mbs derivatives with [ReCl(CO)(5)]/AgSbF(6) . Finally, we have applied this geminal carbo-functionalization to one-carbon-elongated substrates containing N-Ts moieties in their tethers. Selective 5-exo cyclization is achieved in the presence of gold(I) or rhenium(I) catalysts, whereas 6-endo cyclization is observed on use of [W(CO)(6)].
authors.affiliation: Department of Chemistry, Tokyo Institute of Technology, 2-12-1, O-okayama, Tokyo 1528551, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kusama
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Karibe
authors.forename: Rie
authors.initials: R
authors.lastname: Imai
authors.forename: Yuji
authors.initials: Y
authors.lastname: Onizawa
authors.forename: Hokuto
authors.initials: H
authors.lastname: Yamabe
authors.forename: Nobuharu
authors.initials: N
authors.lastname: Iwasawa