Metal-Free Allylic Oxidation with Molecular Oxygen Catalyzed by g-C.sub.3N.sub.4 and N-Hydroxyphthalimide

• Published in: Catalysis letters Vol. 144; no. 4; pp. 717 - 722
• Main Authors: Liu, Guiyin, Tang, Ruiren, Wang, Zhen
• Format: Journal Article
• Language: English
• Published: Springer 01.04.2014
• Subjects: Boron nitride; Oxidation-reduction reactions
• DOI: 10.1007/s10562-014-1200-1
• ISSN: 1011-372X

Polymeric graphitic carbon nitride (g-C.sub.3N.sub.4) is a layered graphite-like nitrogen-rich material, bearing the potential ability to reductively adsorb molecular oxygen for catalytic allylic oxidation. Furthermore, N-hydroxyphthalimide (NHPI) has been recognized as an efficient catalyst for aerobic oxidation of various organic compounds under mild conditions in the presence of various co-catalysts. We present here a promising strategy for employing such nitride-rich g-C.sub.3N.sub.4 combined with NHPI to form an all-organic metal-free composite and have examined its activity for allylic oxidation with molecular oxygen as the primary terminal oxidant. In the case of allylic oxidation [alpha]-isophorone catalyzed by g-C.sub.3N.sub.4/NHPI gave priority to its corresponding carbonyl compound and epoxide. The effects of various reaction conditions on the catalytic reaction were optimized, affording 74.8 % conversion with 44.4 % selectivity of ketoisophorone at 130 °C in 5 h. Repeated runs demonstrated that the catalyst was stable for at least three cycles without noticeable loss of its catalytic activity.