SmI2-Promoted Reformatsky-Type Coupling Reactions in Exceptionally Hindered Contexts
摘要:
Highly substituted, very hindered enones were synthesized using a two-step procedure that utilizes a diiodosamarium-promoted Reformatsky-type coupling and dehydration using Martin sulfurane. Both alpha-chloro- and alpha-bromoketones were coupled with a variety of carbonyl nucleophiles to form the intermediate beta-hydroxyketones, occurring with excellent diastereoselectivity, favoring the syn isomer (R-1 = Me). This technique complements other methods,and enables the preparation of enones outside of the scope of current olefination methodology.
Highly Effective Vinylogous Mukaiyama−Michael Reaction Catalyzed by Silyl Methide Species Generated from 1,1,3,3-Tetrakis(trifluoromethanesulfonyl)propane
Silyl methide species in situ generated from 1,1,3,3-tetrakis(trifluoromethanesulfonyl)propane (Tf2CHCH2CHTf2) performed as an excellent acid catalyst for the vinylogous Mukaiyama-Michael reaction of alpha,beta-unsaturated ketones with 2-silyloxyfurans. Notably, the required loading of Tf2CHCH2CHTf2 to obtain the 1,4-adducts in reasonable yield was significantly low (from 0.05 to 1.0 mol %). This carbon acid-mediated VMM reaction provides a powerful synthetic methodology to construct highly substituted gamma-butenolide structure.