N-Tritylhydroxylamines: preparations, structures, base strengths, and reactions with nitrous acid and perchloric acid
作者:Moisés Canle L.、William Clegg、Ibrahim Demirtas、Mark R. J. Elsegood、Johanna Haider、Howard Maskill、Peter C. Miatt
DOI:10.1039/b103569j
日期:——
N-Trityl, N-(4-methoxytrityl), N-(4,4′-dimethoxytrityl), and N-(4,4′,4″-trimethoxytrityl) derivatives of hydroxylamine, O-methylhydroxylamine, and O-benzylhydroxylamine have been prepared and characterised. Additionally, N,O-ditrityl- and N,O-bis(4,4′-dimethoxytrityl)-hydroxylamines have been made, and the X-ray crystal structure of the former has been determined. The pKa value of O-benzylhydroxylammonium in water (6.2) and of its N-trityl analogue in aqueous acetonitrile (7.5) have been measured. The N-tritylhydroxylamines all decompose under aqueous acidic conditions to give the corresponding trityl alcohols, and rate constants for uncatalysed and hydronium ion catalysed reactions of N-(4,4′-dimethoxytrityl)-O-methylhydroxylamine have been measured by stopped flow kinetics at 25 °C.
This compound compares in reactivity with N-alkyl-N-(4,4′-dimethoxytrityl)amines rather than with 4,4′-dimethoxytritylamine. Attempted nitrosation of N-tritylhydroxylamine and its O-alkyl derivatives gave trityl alcohol, the intermediate N-nitroso compound being detectable but too unstable to isolate. From N-trityl-O-benzylhydroxylamine, attempted nitrosation led to the formation of triphenylmethane in addition to trityl alcohol, benzyl alcohol, and trityl benzyl ether. The mildly acidic conditions used for attempted nitrosation of methoxy-substituted N-tritylhydroxylamines led to deamination before addition of the nitrosating agent.
已经制备并表征了羟胺、O-甲基羟胺和O-苄基羟胺的N-三苯甲基、N-(4-甲氧基三苯甲基)、N-(4,4'-二甲氧基三苯甲基)和N-(4,4',4''-三甲氧基三苯甲基)衍生物。此外,还制备了N,O-二三苯甲基和N,O-双(4,4'-二甲氧基三苯甲基)羟胺,并测定了前者的X射线晶体结构。测量了O-苄基羟胺盐在水中(pKa 6.2)及其N-三苯甲基类似物在乙腈水溶液中(pKa 7.5)的pKa值。所有N-三苯甲基羟胺在酸性水溶液条件下均分解生成相应的三苯甲基醇,通过停流动力学在25°C下测量了N-(4,4'-二甲氧基三苯甲基)-O-甲基羟胺的无催化反应和质子催化反应的速率常数。该化合物的反应性介于N-烷基-N-(4,4'-二甲氧基三苯甲基)胺和4,4'-二甲氧基三苯甲基胺之间。试图对N-三苯甲基羟胺及其O-烷基衍生物进行亚硝化反应,生成三苯甲基醇,中间体N-亚硝基化合物可检测到但过于不稳定而无法分离。从N-三苯甲基-O-苄基羟胺出发,试图进行亚硝化反应除了生成三苯甲基醇外,还形成了三苯甲烷、苄醇和三苯甲基苄基醚。对甲氧基取代的N-三苯甲基羟胺试图进行亚硝化反应时的轻微酸性条件,在加入亚硝化试剂之前先发生了脱氨反应。