Electron-Withdrawing Substituents Decrease the Electrophilicity of the Carbonyl Carbon. An Investigation with the Aid of <sup>13</sup>C NMR Chemical Shifts, ν(CO) Frequency Values, Charge Densities, and Isodesmic Reactions To Interprete Substituent Effects on Reactivity
electron-withdrawing substituents destabilize the carbonyl derivatives investigated. So, a significant ground-state destabilization of carboxylic acid esters, and carbonyl compounds in general, due to the decreased resonance stabilization, is proposed as a novel concept to explain both the increase in their reactivity and the changes in the chemical shifts and carbonyl frequencies induced by electron-withdrawing
The Trifluoroacetate Method of Peptide Synthesis. I. The Synthesis and Use of Trifluoroacetate Reagents
作者:Shumpei Sakakibara、Noriyoshi Inukai
DOI:10.1246/bcsj.38.1979
日期:1965.11
thiophenol and N-hydroxyimide derivatives, which are known as hydroxylic partners of various active carboxylic acid ester, have been synthesized, and it has been found that they are good reagents for the preparation of the respective active esters of acylamino acids by the ester-exchange reaction in pyridine. The new method is especially effective in the preparation of p-nitrophenyl, 2,4,5-trichlorophenyl
A Practical and Highly Efficient Synthesis of α-(Trimethylsilyl)-difluoroacetates
作者:Hideki Amii、Takeshi Kobayashi、Kenji Uneyama
DOI:10.1055/s-2000-8718
日期:——
An efficient method for the gram scale preparation of α-(trimethylsilyl)difluoroacetates is described. The key step involves Mg(0)-promoted selective C-F bond cleavage of readily available trifluoroacetates.
Reactions of the readily accessible electrophile, trifluoroacetyl triflate: a very reactive agent for trifluoroacetylations at oxygen, nitrogen, carbon, or halogen centers