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)].
ABSTRACT
A highly useful method for the construction of cyclopentanone derivatives fused with aromatic ring based on hydrorhodation-1,4-rhodium migration sequence is achieved. Treatment of 1-aryl-prop-2-yn-1-ols, which are easily accessible via an addition of acetylides to the corresponding aryl aldehydes, with a catalytic amount of [Rh(cod)2]2(BF4) and P(p-tolyl)3 in the presence of a base gives cyclopentanone derivatives in moderate to good yield.
Subject(s)
Acetylene/chemistry , Alkynes/chemistry , Rhenium/chemistry , Catalysis , Cyclization , EthersABSTRACT
[reaction: see text] A highly useful method for the construction of polycyclic compounds based on the amine-controlled exo- and endo-selective cyclizations of omega-alkynyl silyl enol ethers catalyzed by W(CO)5L is reported. When bis-alkynyl silyl enol ethers were treated with a catalytic amount of W(CO)6, DABCO, and water under photoirradiation, synthetically useful tricyclic ketones were obtained in good yield.