derivatives by the reaction between benzoyl peroxides and triphenylmethyl in aromatic solvents has been studied. Triphenylmethylation of a solvent molecule is a reaction between benzoyloxy sigma complex and triphenylmethyl. This mechanism has been evidenced by the analysis of isomer ratios of o-, m-, and p-methoxytetraphenylmethanes. These isomer ratios were controlled by the ratios of isomeric benzoyloxy-anisole
Efficient acetylation and benzoylation of alcohols and phenols with acetic and benzoic anhydrides have been carried out under catalysis of bismuth(III) salts including BiCl3, Bi(TFA)3 and Bi(OTf)3. Selective acetylation and benzoylation of alcohols in the presence of phenols is an additional advantage of this procedure.
Stabilities of Trityl-Protected Substrates: The Wide Mechanistic Spectrum of Trityl Ester Hydrolyses
作者:Markus Horn、Herbert Mayr
DOI:10.1002/chem.200902669
日期:2010.7.5
rates of para‐substituted triphenylmethyl (trityl) acetates, benzoates, and para‐nitrobenzoates have been determined in aqueous acetonitrile and aqueous acetone at 25 °C. Conventional and stopped‐flow techniques have been used to evaluate rate constants ranging from 1.38×10−5 to 2.15×102 s−1 by conductimetry and photospectrometry methods. The varying stabilities of the differently substituted tritylium
在25°C的乙腈水溶液和丙酮水溶液中测定了对位取代的三苯甲基(三苯甲基)乙酸酯,苯甲酸酯和对硝基苯甲酸酯的电离速率。常规和停止流技术已用于评估速率常数,范围为1.38×10 -5到2.15×10 2 s -1通过电导和光度法。不同取代的三苯甲基离子的不同稳定性说明了反应机理的逐渐变化。弱稳定的碳阳离子通过其共价前体的电离缓慢生成,并被水快速捕获。更好稳定的碳正离子会更快地生成并积累,因此在单个实验中可以将水的电离和捕获作为单独的步骤进行观察。最后,高度稳定的tr离子不会与水反应,只能测量其形成速率。电离速率常数与Winstein的电离功率Y线性相关。低坡度(0.17 < m<0.58)表示非类碳化过渡状态。尽管对于对称取代的三苯甲基衍生物,电离速率与Hammett-Brown的σ +参数之间的相关性极好,但观察到非对称取代的系统的偏差。电离速率(log k ion)和水溶液中碳正离子的稳定性(p
Trimethysilyl triflate in organic synthesis11Part 11 of this series. Part 10: S. Murata and R. Noyori, Tetrahedron Letters 2107 (1981).
作者:R. Noyori、S. Murata、M. Suzuki
DOI:10.1016/s0040-4020(01)93263-6
日期:——
Trimethylsilyl triflate is a powerful silylating agent for organic compounds and acts as a catalyst which accelerates a variety of nucleophilic reactions in aprotic media. The reactions proceed via one-center, electrophilic coordination of the silyl group to hetero functional groups and exhibit unique selectivities.
Zinc chloride homogeneous catalysis in the tritylation of hydroxyl- and amide-bearing molecules
作者:Maurizio Maltese、Maria Cecilia Vergari、Maria Pia Donzello
DOI:10.1016/j.tetlet.2010.11.095
日期:2011.1
A tritylation protocol based on the transfer of the triphenylmethylcarbenium ion from trityl acetate to substrates having hydroxyls, in the presence of catalytic amounts of ZnCl2, is described. The advantages of this method are broad scope, mild conditions, and easy handling. The comparison with the procedure based on the use of equimolar mixture of TrCl and ZnCl2 in the presence of TEA shows that