Hydroxy-substituted triarylcarbenium bromides. Synthesis, structure, derivatization and facile conversion to highly substituted xanthenes †
作者:Maarten B. Dinger、Michael J. Scott
DOI:10.1039/b001032o
日期:——
The tris(3,5-dialkyl-2-hydroxyphenyl)carbenium bromides (2a) (3-tert-butyl, 5-methyl) and 2b (3,5-di-tert-butyl) have been prepared by the oxidation of the corresponding tris(3,5-dialkyl-2-hydroxyphenyl)methanes with bromine. Compound 2a has been fully characterized by a single crystal X-ray study, which shows that the bromide, atypically, does not bind to the central carbon atom. The materials 2 are reactive, and the trityl alcohol (4a), methyl (7a, 7b) and phenyl (8a) derivatives can be readily prepared in good yield by reaction of 2 with the appropriate anions; X-ray structures for 4a, 7b (as its lithium salt) and 8a are reported. In solution, 2a and 4a undergo a facile, uncatalyzed, controllable intramolecular dehydration to produce the corresponding xanthene derivatives; X-ray structures for the xanthene carbocation (bromide salt) (3a) and the 9-hydroxy derivative (5a) are also reported.
三(3,5-二烷基-2-羟基苯基)溴化碳(2a)(3-叔丁基,5-甲基)和2b(3,5-二叔丁基)是通过氧化相应的三(3,5-二烷基-2-羟基苯基)甲烷与溴。化合物 2a 已通过单晶 X 射线研究得到充分表征,表明溴化物非典型地不与中心碳原子结合。材料2具有反应性,通过2与适当的阴离子反应,可以容易地以良好的产率制备三苯甲基醇(4a)、甲基(7a,7b)和苯基(8a)衍生物;报道了 4a、7b(作为其锂盐)和 8a 的 X 射线结构。在溶液中,2a和4a经历简单、非催化、可控的分子内脱水,生成相应的呫吨衍生物;还报道了呫吨碳阳离子(溴化物盐)(3a)和 9-羟基衍生物(5a)的 X 射线结构。