| STUDY |
Meanwhile, in the lab of Matthias Selke, an associate professor of chemistry at California State University, Los Angeles, a project started in 2000 by a high school intern has led to direct observation of a new phosphine species, namely tris(orthomethoxyphenyl)phosphadioxirane, and its application to alkene epoxidation. The high school student, Timothy Dong, who is now a chemistry undergraduate at California Institute of Technology, was assigned to analyze the products of the reaction of certain bulky phosphines with singlet oxygen at room temperature. The reaction with triplet oxygen is well known, but little work had been done with singlet oxygen, and Selke was curious. Dong's results, together with those of others in the Selke lab, strongly suggested the involvement of a phosphadioxirane intermediate as the first product of the reaction between singlet oxygen and the bulky phosphines [Org. Lett., 3, 3719 (2001)]. Direct observation of the intermediate could not be done at that time as reactions were run at room temperature. Selke, with postdoctoral research associate Ruomei Gao and graduate students David G. Ho, Jeff Celaje, and Ha-Yong Chung, have since carried out experiments with bulky ortho-substituted phosphines at –80 °C and have now prepared a phosphadioxirane. 31P and 17O nuclear magnetic resonance spectroscopies reveal a peroxide bound in a triangle to phosphorus, as predicted by others through ab initio calculations. Furthermore, the researchers have shown the utility of the phosphadioxirane in low-temperature olefin epoxidation. In all cases tested, the epoxide is the sole product, with yields ranging from 60 to 80%. |
|
Want more information ? Interested in the hidden information ? Click here and do your request. |