Green oxidations: Titanium dioxide induced tandem oxidation coupling reactions

• Vineet Jeena and
• Ross S. Robinson

Beilstein J. Org. Chem. 2009, 5, No. 24, doi:10.3762/bjoc.5.24

• , quinoxalines have been synthesized in good yields from the corresponding α-hydroxyketones. Keywords: quinoxalines; tandem oxidation process; titanium dioxide; Introduction Titanium dioxide has found widespread industrial application ranging from whiteners in paint [1], and additives in food [2], to UV

• chemistry point of view, titanium dioxide’s main use has been to oxidize alcohols to its corresponding carbonyl derivatives which has been reported many times [8][9][10]. Titanium dioxide has also been used to synthesize dihydropyrazines [11], piperazines [12], and quinoxalines [13] although in low yields

• . Herein, we describe the application of titanium dioxide in conjunction with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as an oxidant in the synthesis of quinoxalines, via the tandem oxidation process (TOP) (Scheme 1). Results and Discussion Titanium dioxide in the anatase phase is a