Reactions between isocyanates and carbanions with an acetyl group at the carbanion center occur via rearrangement of the intermediate N-anions into isomeric C-anions by C -->N-migration of the MeC(O) group. The acetyl group undergoes migration easier than the ethoxycarbonyl group. The P-zwitterionic rearrangement products were subjected to X-ray diffraction analysis.
C→N migration of methoxycarbonyl and acetyl groups in reactions of functionally substituted carbanions with aryl isocyanates. Kinetics and mechanism of the reactions
作者:V. I. Galkin、Yu. V. Bakhtiyarova、D. B. Mal’tsev、I. V. Galkina、Yu. G. Gololobov、O. A. Linchenko
DOI:10.1007/s11172-006-0346-4
日期:2006.5
The kinetics and mechanism of C→N migrations of methoxycarbonyl and acetyl groups in the reactions of the sodium derivative of methyl (2-cyano-2-phenyl)acetate and 1,1-diacetyl-2-phenyl-2-tributylphosphonioethanide with arylisocyanates were studied by spectrophotometry. The reactions afford a prereaction complex via a concerted mechanism, according to which the nucleophilic attack of the carbanionic
(2-氰基-2-苯基)乙酸甲酯钠衍生物和1,1-二乙酰-2-苯基-2-三丁基膦酰乙烷与异氰酸芳基酯反应中甲氧基羰基和乙酰基的C→N迁移动力学和机理用分光光度法研究。该反应通过协同机制提供预反应复合物,根据该机制,碳离子中心对异氰酸酯基团的碳原子进行亲核攻击,随后氮原子对羰基碳原子进行亲核攻击,导致 CC 键断裂, 几乎同时发生在同一过渡态的框架内。