Acylation. Part XXVI. The kinetics and mechanism of the addition of carboxylic acids to ketens in diethyl ether and in dichlorobenzene solution
作者:J. M. Briody、P. J. Lillford、D. P. N. Satchell
DOI:10.1039/j29680000885
日期:——
The addition of carboxylic acids to dimethylketen in ether solution and to diphenyl- and mesitylphenyl-keten in o-dichlorobenzene solution has been studied kinetically at 25°. In ether the rate equation takes the form: –d[Keten]/dt=k[RCO2H][Keten] and in dichlorobenzene it is normally –d[Keten]/dt=k[(RCO2H)2][Keten]. The reactivities of the acids, the substituent effect of the mesityl group, and the
加入的羧酸,以乙醚溶液dimethylketen和二苯基和mesitylphenyl-keten在Ö二氯苯溶液已经动力学在25℃的研究。在乙醚中,速率方程的形式为:–d [Keten] / d t = k [RCO 2 H] [Keten];在二氯苯中,通常为–d [Keten] / d t = k [(RCO 2 H)2] [基滕]。酸的反应性,均三甲苯基的取代作用和氢同位素作用均与每种溶剂中存在两种不同的添加路径一致。传统上较弱的酸采取的一种途径涉及环状过渡态和该酸对酮的羰基碳原子的亲核攻击。通过该路径的添加速度与酸强度成反比。可供研究的最强酸使用的另一种非环状路径涉及质子从酸到酮的β-碳原子或氧原子的直接转移。
Concave Reagents, 21. Selective Acylations of Primary and Secondary Alcohols by Ketenes
作者:Wolfgang Schyja、Sönke Petersen、Ulrich Lüning
DOI:10.1002/jlac.199619961223
日期:1996.12
Concavepyridines 1 were used to catalyze the addition of primary and secondary alcohols to ketenes 4, and the kinetic data of these catalyses were determined. In inter- and intramolecular competitions the use of 1e–g led to improved selectivities for the acylation of primary alcohols in comparison with secondary alcohols. All primary alcohols react at comparable rates. Observed rate constants were
Stereoelectronic Effects in the Nucleophilic Addition to the sp-Hybridized Carbon of a Ketene and Vinyl Cation: When Is a Mesityl Effectively Smaller than a Phenyl Ring?<sup>1</sup>
作者:Hiroshi Yamataka、Oleg Aleksiuk、Silvio E. Biali、Zvi Rappoport
DOI:10.1021/ja962573a
日期:1996.1.1
occurs preferentially from the side of the formally bulkier mesityl ring. Ketene 3 and the two diastereomeric transitionstates obtained by attack of MeLi on its CO were calculated by abinitiocalculations. 3 adopts a conformation with a planar Ph-CC moiety while the mesityl is nearly perpendicular to this plane. Since the attack on the CO group occurs in the plane of the CC double bond, the coplanar