Quasiphosphonium intermediates. Part 3. Preparation, structure, and reactivity of alkoxyphosphonium halides in the reactions of neopentyl diphenylphosphinite, dineopentyl phenylphosphonite, and trineopentyl phosphite with halogenomethanes and the effect of phenoxy-substituents on the mechanism of alkyl–oxygen fission in Michaelis–Arbuzov reactions
作者:Harry R. Hudson、Aloysius Kow、John C. Roberts
DOI:10.1039/p29830001363
日期:——
of the phosphonium halide ion-pair with SN2-type fission of the alkyl–oxygen bond. Rates for chloride, bromide, and iodide are similar. In a more ionising medium (deuterioacetonitrile) dissociation leads to stabilisation of the intermediates and to deviation from first-order decomposition. Previously determined X-ray diffraction data for the bromides, together with relative rates of decomposition in
新戊基二苯基次膦酸酯与氯甲烷,溴甲烷或碘甲烷的反应以及二戊基苯基次膦酸酯与溴甲烷或碘甲烷的反应产生结晶的烷氧基phosph卤化物。在氘代氯仿中,这些中间体通过一阶过程分解,该过程涉及速率确定卤化phospho离子对的崩溃以及烷基-氧键的S N 2型裂变。氯化物,溴化物和碘化物的比率相似。在离子化程度更高的介质(氘代乙腈)中,离解可导致中间体稳定并偏离一级分解。先前确定的溴化物X射线衍射数据,以及一系列Ph中间体的氘代氯仿中的相对分解速率n(RO) 3– n [MeX] -(n= 0、1或2)表明,烷氧基phosph中间体的稳定性和反应性很大程度上取决于配体的诱导效应而不是介晶效应。在某些情况下,磷上苯氧基取代基的存在可能导致烷基-氧键发生S N 1型裂变。