键解离的能量学,尤其是R–H键杂合自由能(p K a),在促进化学成为一门科学方面发挥了核心作用。尽管在文献中对酸度进行了研究,但目前的知识仅限于经典分子溶剂中的知识,并且无法扩展以预测离子介质中酸度的变化。由于后者现在非常流行于替代挥发性有机溶剂,因此迫切需要了解随着介质组成从中性分子转换为带电离子而改变键裂解的驱动力的方法。在这里,我们描述了一种测量绝对值p K a的通用方法在纯离子液体(IL)中。概述了保证精确测量的标准条件。确定了四个IL中所选的18 C–H型指示剂酸的p K a,并构建了方便的指示剂平台以轻松扩展酸度标度。这些绝对的p K a使得首次可以将IL中的键能与分子溶剂中以及气相中的键能进行直接比较,并且应该能够用作校准适合于该研究的计算方法的标准参数。在离子介质中。分析了IL中阳离子和阴离子与结构的关系。
The synthesis of α-acetoxy sulfides and their lewis acid-mediated reactions
作者:George A. Kraus、Hiroshi Maeda
DOI:10.1016/0040-4039(95)00349-h
日期:1995.4
α-Acetoxy sulfides can be conveniently prepared by the reaction of dithioacetals with mercuric acetate at ambient temperature. They react with allyltrimethylsilane, enol silyl ethers, and cyanotrimethylsilane in the presence of SnCl4 to afford butenyl sulfides, γ-keto sulfides and α-cyano sulfides, respectively.
Equilibrium Acidities of Nitroalkanes in an Ionic Liquid
作者:Feixiang Gao、Pengju Ji、Jin-Pei Cheng
DOI:10.1021/acs.joc.8b02183
日期:2018.12.21
The acidity ladder scale in [BMPY][NTf2] was successfully expanded toward the weak acidity region for about five more pK units compared to the previously established one. This allows the acidities of a series of 13 aliphatic and aromatic nitroalkanes to be determined accurately by the UV–vis spectroscopic method. The acidity of nitroalkane in [BMPY][NTf2] covers ∼8 pK units and is significantly weaker
thioacetals to give the corresponding γ-ketosulfides in good yields with high stereoselectivity. In a similar manner, γ-ketosulfides are obtained in good yields by the one pot reaction directly fromketones and thioacetals via tin(II) enolates.
In the presence of gallium chloride, dithioacetals reacted with allylstannanes to give the corresponding homoallyl sulfides in high yields. The present method could be applied to the chemoselective allylation of bis(dithioacetal) of keto aldehyde, and the dithioacetal arising from keto function reacted with allylstannane exclusively.