Treatment of (3,3-dialkyl-2,2-dichlorocyclopropyl)methanols with hydrobromic acid gives 2-cyclopentenones through postulated intermediates, 3-chlorocyclopentadienyl cations. Another method which sh...
The Rearrangement of 2,3-Epoxysulfonates and Its Application to Natural Products Syntheses: Formal Synthesis of (−)-Aphanorphine and Total Syntheses of (−)-α-Herbertenol and (−)-Herbertenediol
作者:Yasuyuki Kita、Junko Futamura、Yusuke Ohba、Yoshinari Sawama、Jnaneshwara K. Ganesh、Hiromichi Fujioka
DOI:10.1021/jo034573g
日期:2003.7.1
The Lewis acid treatment of 2,3-epoxysulfonates with 2,3-dialkyl substituents or 2-alkyl-3-aryl substituents produced the rearrangementproducts via C3-cleavage of the oxirane ring in high yields. On the other hand, 2-aryl-3-alkyl-2,3-epoxysulfonates produced the products via C2-cleavage of the oxirane ring. The sulfonyloxy groups of the alpha-sulfonyloxy ketones, having a chiral benzylic quaternary
Monocyclopentadienyl complexes in which the cyclopentadienyl system bears at least one bridged donor and at least one aryl group and a catalyst system comprising at least one of the monocyclopentadienyl complexes, and also processes for preparing them, the use of the catalyst system for the polymerization or copolymerization of olefins and a process for preparing polyolefins by polymerization or copolymerization of olefins in the presence of the catalyst system and the preparation of the associated cyclopentadienyl system.
Monocyclopentadienyl complexes in which the cyclopentadienyl system bears at least one bridged donor and at least one aryl group and a catalyst system comprising at least one of the monocyclopentadienyl complexes, and also processes for preparing them, the use of the catalyst system for the polymerization or copolymerization of olefins and a process for preparing polyolefins by polymerization or copolymerization of olefins in the presence of the catalyst system and the preparation of the associated cyclopentadienyl system.
Reaction of cyclic .alpha.-hydroxy epoxides with a strong base: a new 1,2-rearrangement, evidence for a carbenoid pathway.
作者:Eric Doris、Luc Dechoux、Charles Mioskowski
DOI:10.1021/ja00156a006
日期:1995.12
Several substituted five- and six-membered cyclic alpha,beta-unsaturated ketones are readily available by treatment of the corresponding alpha-hydroxy epoxides with an organolithium reagent. The reaction involves a new carbenoid 1,2-alkyl rearrangement. Evidence for the carbenoid intermediate has been obtained by an intramolecular trapping of the highly reactive species.