Stable simple enols. 11. Equilibrium constants for the 1-alkyl-2,2-dimesitylethenol/1-alkyl-2,2-dimesitylethanone systems in hexane. The predominance of steric effects on Kenol values
various sterically congested sodium enolates, generated by quantitative deprotonation of stable enols (of diphenylacetaldehyde in the case of 5), with dichlorotitanocene afforded a series of novel titanium enolates 1-5. The crystal structure of 1 could be determined. Due to the considerable stericshielding of the β,β-diaryl moiety, all the titanium enolates exhibit an oustanding stabilitytowards hydrolysis
由稳定的烯醇(在5的情况下,二苯乙醛的定量)质子化所引起的各种空间拥塞的烯醇钠与二氯噻吩并茂的反应,提供了一系列新型的烯醇钛1-5。可以确定1的晶体结构。由于β,β-二芳基部分的相当大的空间屏蔽作用,所有的烯醇钛盐都表现出极好的水解稳定性,随着对CC双键的取代基的更高空间需求,该稳定性增加。通过UV光谱法研究了水解的动力学,其在THF /水(1:1)和乙腈/水(1:1)中为拟一级反应。在这些溶剂混合物中测得的拟一级反应速率常数在6.4·10的范围内-4 s -1 < k 1 <1.1·10 -3 s -1。为了进行比较,应该表现出通常的烯醇钛酸酯对水解敏感性的6的水解快约1000倍。
A comprehensive picture of the one-electron oxidation chemistry of enols, enolates and α-carbonyl radicals: oxidation potentials and characterization of radical intermediates
stable simple enols of amides. The results allow to clarify the primary reaction pathway of enolradicalcations as a rapid deprotonation and—if warranted by the redox potential and the strength of the oxidant—a follow-up oxidation of the resultant α-carbonyl radical to the α-carbonyl cation. Moreover, the experimental oxidation potentials were linearly correlated with AM1 computed ionization potentials
First characterisation of zirconium enolate radical cations in solution and their mesolytic bond cleavage to zirconocene cations
作者:Michael Schmittel、Rolf Söllner
DOI:10.1039/a708495a
日期:——
Zirconocene enolate radical cations are generated and characterised in solution for the first time; the sterically congested radical cations undergo a mesolytic Zr–O bond cleavage process yielding zirconocene cations, the kinetics of which are determined.
ester radicalcations is characterized in solution by cyclic voltammetry and EPR spectroscopy. Preparative transformations using one-electron oxidants or anodic oxidation yield benzofurans after O-CO bond cleavage. Mechanistic investigations and direct detection of radical intermediates reveal that all enol radicalcations undergo exclusively O-CO bond cleavage to provide alpha-carbonyl cations and acyl
A rearranged acetylene from an E1 solvolysis of a substituted α-trimethylsilylvinyl system
作者:Elana Zipori、Zvi Rappoport
DOI:10.1016/0040-4039(91)80177-8
日期:1991.10
The reaction of Mes2CC(OH)SiMe2R (RMe, SiMe3) with SOCl2 gives the rearrangedelimination product MesCCMes, presumably via β-mesityl participation in the solvolysis of the derived OSOCl derivative, followed by “Me3Si+“ loss from the rearranged ion MesC(Me3Si)C-Mes. Under the same conditions, the carbon analogue Mes2CC(OH)Bu-t gives the ketone Mes2CHCOBu-t and benzofurans via non-solvolytic reactions
ME的反应2 CC(OH)森达2 R(RMe,森达3)用的SOCl 2给出了重排的消除产物MesCCMes,通过在派生OSOCl衍生物的溶剂解β-基参与推测,随后重排离子MesC(Me 3 Si)C-Mes引起的“ Me 3 Si + ”损失。在相同条件下,碳类似物的Mes 2 CC(OH)卜叔给出了酮的Mes 2经由非溶剂化反应CHCOBu-t和苯并呋喃。