Photochemical generation and trapping of oxyallyl in crystalline ketones

ORGN 102

Chao-Kuan Tsai, cktsai@chem.ucla.edu1, Christopher P. Suhrada, csuhrada@chem.ucla.edu2, Patrick McCarren1, Kendall N. Houk3, and Miguel Garcia-Garibay, mgg@chem.ucla.edu2. (1) Department of chemistry and Biochemistry, graduate student, UCLA, 607 Charles E. Young Dr. East, Los Angeles, CA 90095, (2) Department of Chemistry and Biochemistry, University of California, Los Angeles, BOX 951569, Los Angeles, CA 90095-1569, (3) Department of Chemistry and Biochemistry and California Nanosystems Institute, University of California, Los Angeles, 607 Charles E. Young Drive East, Box 951569, Los Angeles, CA 90095
Oxyallyl has been proposed as an intermediate in several organic reactions including a few biosyntheses. It has been debated whether oxyallyl is best described as a biradical or as a zwitterionic species. Several attempts have been reported in the literature to reveal the nature of oxyallyl via chemical trapping, detection in solution, and matrix isolation. While studying the solid-state photochemistry of a cyclobutanedione, we came across the formation of an intermediate that has spectral property consistent with those expected for oxyallyl. The characterization of the trapped oxyallyl was demonstrated using three different experiments—chemical trapping by a [4+2] cycloaddition, and spectroscopic detection by UV and EPR techniques to characterize the physically trapped oxyallyl. With the help of the rigidity of crystal lattice, the lifetime of photochemically generated oxyallyl from crystalline diketone has been extended to hours at room temperature for characterization. The combination of experimental and computational results suggests that the trapped oxyallyl prefers to exist as a zwitterionic rather than a biradical.

 

Process R&D, Physical Organic Chemistry, Heterocycles, Aromatics, Metal-Mediated Reactions
8:00 PM-10:00 PM, Sunday, March 25, 2007 Hyatt Regency Chicago -- Riverside Center, Poster

Division of Organic Chemistry

The 233rd ACS National Meeting, Chicago, IL, March 25-29, 2007