Tetrasubstituted compounds olefin synthesis

Hernandez, D., Larson, G. L. Chemistry of a-silyl carbonyl compounds. 9. Synthesis of tri- and tetrasubstituted olefins from a-silyl esters. J. Org. Chem. 1984, 49, 4285-4287. 

Stereoselective synthesis of tetrasubstituted alkenes remains a challenging task. A unique solution to this problem is to use torquoselectivity-controlled oletina-tion of carbonyl compounds with ynolates, which is summarized in Chapter 1. In general, the stereoselective synthesis of Z-alkenes, which are thermodynamically less favorable, is more difficult than the synthesis of corresponding -isomers. In Chapter 2, various methods for stereoselective synthesis of Z-alkenes are reviewed. Finally, the C=C double bond formation through catalytic carbene transformation has recently emerged as a new approach toward olefin synthesis. Two chapters covering olefin synthesis based on catalytic carbene transformations are included (Chapter 5 and Chapter 8). 

Najera and co-workers have also successfully employed BTFP sulfones in the synthesis of tri- and tetrasubstituted olefins by reacting with carbonyl compounds in the presence of phosphazene base P4-f-Bu at room temperature in THF. ... 

Homer-Wadsworth-Emmons reactions encounter serious problems of reactivity, stereoselectivity, and generality when used to form tetrasubstituted olefins. Most studies on the synthesis of tetrasubstituted olefins exploit alternative routes based on carbometalation of alkynes [17-19]. However, these processes have difficulties associated with the regioselectivity of the initial carbometalation and with reactivity during the final coupling. Here we describe stereoselective s3mtheses of tetrasubstituted olefins, via the olefination of carbonyl compounds with ynolates, as well as some synthetic applications [20,21]. 

Stereoselective Synthesis of Tetrasubstituted Alkenes via Torquoselectivity-Controlled Olefination of Carbonyl Compounds... 

Review Shindo M, Mori S. Torquoselective olefination of carbonyl compounds with ynolates highly efficient stereoselective synthesis of tetrasubstituted alkenes. Synlett 2008 2231-2243. 

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