Pyridin-4-ones nitration

Ha.logena.tlon, One review provides detailed discussion of direct and indirect methods for both mono- and polyhalogenation (20). As with nitration, halogenation under acidic conditions favors reaction in the benzenoid ring, whereas reaction at the 3-position takes place in the neutral molecule. Radical reactions in the pyridine ring can be important under more vigorous conditions. 

Electrophilic substitution reactions of unsubstituted quinoxaline or phenazine are unusual however, in view of the increased resonance possibilities in the transition states leading to the products one would predict that electrophilic substitution should be more facile than with pyrazine itself (c/. the relationship between pyridine and quinoline). In the case of quinoxaline, electron localization calculations (57JCS2521) indicate the highest electron density at positions 5 and 8 and substitution would be expected to occur at these positions. Nitration is only effected under forcing conditions, e.g. with concentrated nitric acid and oleum at 90 °C for 24 hours a 1.5% yield of 5-nitroquinoxaline (19) is obtained. The major product is 5,6-dinitroquinoxaline (20), formed in 24% yield. 

Furo[3,4-d]pyridazine-1,4-diones synthesis, 4, 985 Furopyridazines, 4, 984 Furo[2,3-6]pyridine, 3-amino-synthesis, 4, 977 Furo[2,3-6]pyridine, 4-methyl-synthesis, 4, 976 Furo[2,3-6]pyridine, 6-methyl-synthesis, 4, 976 Furo[2,3-6]pyridine, 5-nitro-synthesis, 4, 977 Furo[3,2-c]pyridine, 4-allyl-synthesis, 4, 982 Furopyri dines H NMR, 4, 983 physical data, 4, 983 properties, 4, 982 synthesis, 4, 974-982 UV spectroscopy, 4, 983 Furo[6]pyri dines HMO data, 4, 975 Furo[2,3-6]pyri dines synthesis, 4, 974-977 7, 512 Furo[3,2-6]pyri dines C NMR, 4, 982 synthesis, 4, 648, 981 Furo[c]pyri dines HMO data, 4, 976 Furo[2,3-c]pyri dines synthesis, 4, 977 Furo[3,2-c]pyri dines nitration, 4, 983 synthesis, 4, 978-981 Furo[3,4-c]pyri dines synthesis, 4, 982 Furo[3,2-c]pyridin-3-ols synthesis, 4, 980 Furo[2,3-6]pyridin-6-ones synthesis, 4, 976 Furo[3,4-c]pyridin-4-ones synthesis, 4, 982... 

Tridentate 2,6-bis(thiomorpholinomethyl)pyridine (173) forms only the 1 1 complex [Ni(173)(N03)2] with Ni11. However, the geometry around the metal center is octahedral due to coordination of two nitrates, one as a monodenate and the other as a bidentate ligand.578... 

Furazan compound 278 was obtained as a by-product from cholestan-3-one oxime 277 by prolonged heating in an acetic anhydride-pyridine mixture followed by treating with acetyl nitrate prepared from acetic anhydride and nitric acid (Equation 53) <1997T16161>. 

Nitration with tetranitromethane proceeds along the ion-radical ronte. Tetranitromethane is a smooth nitrating agent and mild oxidizer. It is convenient for nitration of highly activated snbstrates snch as phenols, azulene, and heterocycles in the presence of pyridine, N,iV-dialkylaniline, etc. As shown (Morkovnik 1988), these reactions inclnde one-electron transfer ... 

Pyrazine and pyrimidine heterocycles, like pyridine, are electron deficient and need the presence of an activating/electron-releasing group to allow efficient electrophilic nitration to occur. An example of this strategy is seen during the synthesis of 2,6-diamino-3,5-dinitropyrazine (ANPz) (183) where one of the chloro groups of 2,6-dichloropyrazine (180) is substituted for a... 

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