One-pot three-component synthesis of quinoxaline and phenazine ring systems using Fischer carbene complexes

• Priyabrata Roy and
• Binay Krishna Ghorai

Beilstein J. Org. Chem. 2010, 6, No. 52, doi:10.3762/bjoc.6.52

• parent organisms [2][3]. These compounds show diverse biological activities such as antibacterial, antifungal, antiviral and antitumor properties [4][5][6][7][8]. While rarely found in nature, quinoxalines are well known in the pharmaceutical industry and have been shown to possess a broad spectrum of

Preparation, structures and preliminary host–guest studies of fluorinated syn-bis-quinoxaline molecular tweezers

• Markus Etzkorn,
• Jacob C. Timmerman,
• Matthew D. Brooker,
• Xin Yu and
• Michael Gerken

Beilstein J. Org. Chem. 2010, 6, No. 39, doi:10.3762/bjoc.6.39

• , host–guest NMR studies of compound 16c in solution show chemical exchange between the unbound and bound electron-rich guest, N,N,N′,N′-tetramethyl-p-phenylenediamine. Keywords: crystal structure; fluorine; molecular tweezers; quinoxalines; self-association; Introduction A broad variety of

• potentials of belt-shaped compounds 2a–c and predicted the complexation of halide anions in the cavity of 2c [16][17][18]. Intrigued by Chou’s communication on the spectroscopic properties of non-fluorinated bis-quinoxalines of type 3 and 4a [19], we targeted on the corresponding fluorinated derivatives – in

• association with electron-rich guest compounds. Results and Discussion Synthesis of fluorinated bis-quinoxalines The general route [19] to bis-quinoxaline targets (Scheme 2) utilizes a twofold Diels–Alder reaction of a cycloalkadiene (5,6) with cyclopentadienone derivatives (7), subsequent oxidation of the

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