An electrophilictrifluoromethylation of ketene silyl acetals (KSAs) by hypervalent iodine reagents 1 and 2 has been developed. The reaction proceeds under very mild conditions in the presence of a catalytic amount of trimethylsilyl bis(trifluoromethanesulfonyl)imide (up to 2.5 mol %) as a Lewis acid providing a direct access to a variety of secondary, tertiary, and quaternaryα-trifluoromethyl esters
Treatment of silyl enol ethers of various carbonylcompounds with Et2Zn and fluoroalkyl halides (Rf–X) in the presence of RhCl(PPh3)3 in DME gave the corresponding α-Rf carbonylcompounds. A highlyreactive alkyl-rhodium complex which was derived from RhCl(PPh3)3 and Et2Zn must be crucial in this reaction by accelerating the reaction rate and improving the yields dramatically. This reaction overcomes
在RhME(PPh 3)3存在下,在DME中用Et 2 Zn和氟代烷基卤化物(R f –X)处理各种羰基化合物的甲硅烷基烯醇醚,得到相应的α- Rf羰基化合物。衍生自RhCl(PPh 3)3和Et 2 Zn的高反应性烷基铑络合物必须通过加快反应速率和显着提高产率来在该反应中发挥关键作用。该反应克服了由于R f –X的反极化而在合成α- Rf羰基化合物时遇到的困难。
Catalytic, Enantioselective Alkylation of α-Imino Esters: The Synthesis of Nonnatural α-Amino Acid Derivatives
作者:Dana Ferraris、Brandon Young、Christopher Cox、Travis Dudding、William J. Drury、Lev Ryzhkov、Andrew E. Taggi、Thomas Lectka
DOI:10.1021/ja016838j
日期:2002.1.1
Methodology for the practical synthesis of nonnatural amino acids has been developed through the catalytic, asymmetric alkylation of α-imino esters and N,O-acetals by enol silanes, ketene acetals, alkenes, and allylsilanes using chiral transition metal-phosphine complexes as catalysts (1−5 mol %). The alkylation products, which are prepared with high enantioselectivity (up to 99% ee) and diastereoselectivity
α-Allylation of Carbonyl Compounds via Silyl Enol Ethers and Silyl Ketene Acetals using a Hypervalent Iodine Reagent†
作者:Robert M. Moriarty、Widanagamage R. Epa、Om Prakash
DOI:10.1039/a701224a
日期:——
allyltrimethylsilane with iodosobenzene and trimethylsilyl trifluoromethanesulfonate followed by treatment with trimethylsilyl enolethers of ketones or trimethylsilyl ketene acetals of esters/lactones provides a new method for the α-allylation of the corresponding carbonylcompounds.