Zwitterionic Ring-Opened Oxyphosphonium Species from the Ph3P–I2 Mediated Reactions of Benzo[d]oxazol-2(3H)‑ones with Secondary Amines

Instead of the expected substituted 2-aminobenzo­[d]­oxazoles, relatively stable ring-opened oxyphosphonium betaines were isolated for the first time from the Ph3P–I2-mediated reactions of benzo­[d]­oxazol-2­(3H)-ones with acyclic secondary amines. The structure of one of these compounds was unambiguously confirmed by single-crystal X-ray analysis. Thermolysis of the betaines gave rise to 2-dialkylaminobenzoxazoles with concomitant loss of triphenylphosphine oxide, suggesting their possible role as intermediates in an alternative reaction path.本研究首次从三苯基膦-碘（Ph3P–I2）介导的苯并[d]恶唑-2(3H)-酮与非环二级胺的反应体系中，分离得到了相对稳定的开环氧鏻内盐，而非预期的取代2-氨基苯并[d]恶唑。其中一种化合物的结构通过单晶X射线衍射分析得到了明确确证。对该类氧鏻内盐进行热解，可生成2-二烷基氨基苯并恶唑，同时伴随三苯基氧膦的脱除，这表明其可能作为替代反应路径的中间体参与反应。