Tandem carbonyl ene cyclization-cycloalkylation: a route to trifluoromethyl diterpenoids.
摘要:
A new sequential carbonyl-ene cyclizatian/cycloalkylation of trifluoromethyl ketones catalyzed by aluminum Lewis acids is described. From ketone 1, the 4-CF3-4-OH cis-octahydrophenanthrene 6 is obtained in 50 % yield. From ketone 2, with MeAlCl(2) a total stereoselective route to the 4-CF3-trans-10-methyl podocarpatrienol 8 (90 % yield) has been found. These studies also exhibited some striking results in the stereochemical outcome of ene cyclizations.
Tandem carbonyl ene cyclization-cycloalkylation: a route to trifluoromethyl diterpenoids.
摘要:
A new sequential carbonyl-ene cyclizatian/cycloalkylation of trifluoromethyl ketones catalyzed by aluminum Lewis acids is described. From ketone 1, the 4-CF3-4-OH cis-octahydrophenanthrene 6 is obtained in 50 % yield. From ketone 2, with MeAlCl(2) a total stereoselective route to the 4-CF3-trans-10-methyl podocarpatrienol 8 (90 % yield) has been found. These studies also exhibited some striking results in the stereochemical outcome of ene cyclizations.
Acid-Catalyzed Intramolecular [2+2] Cycloaddition of Ene-allenones: Facile Access to Bicyclo[<i>n</i>.2.0] Frameworks
作者:Jun-Feng Zhao、Teck-Peng Loh
DOI:10.1002/anie.200902471
日期:2009.9.14
Two plus two equals a bicycle: A highly efficient acid‐catalyzed intramolecular [2+2] cycloaddition of ene‐allenones affords strained bicyclo[n.2.0] frameworks, which contain vicinal all‐carbon quaternary and tertiary centers (see scheme; Tf: trifluoromethanesulfonyl), under mild conditions with excellent yields and chemo‐, regio‐, and diastereoselectivities.
This paper describes highly efficient catalyticenantioselective cationic polyene cyclization and catalyticenantioselective intramolecular carbonyl-enereaction in good to high yields with high enantioselectivities. The intimate relationship and mechanistic differences between the two enantioselectivereactions were studied in detail. In addition, the cyclization products are versatile and useful building