A number of new 2-methyl- and 2-arylvinyl-3-nitropyridines were synthesized and their reactions with thiols were studied. It was found that 3-NO2 tends to be selectively substituted under the action of sulfur nucleophiles in the presence of another nucleofuge in position 5. Correlations between the substitution pattern and regioselectivity as well as photophysical properties were established. Some synthesized compounds possessed a large Stokes shift.
An efficient method was developed for the synthesis of 5,7-dinitroquinoline and its N-oxide. The reactions of these compounds with either thiols or sodium azide resulted in the regiospecific substitution of 5-NO 2 group and the formation of previously unknown quinoline derivatives.The 5-azido derivatives underwentr eactions with 1,3-dicarbonyl compounds and, depending on the nature of reagent, afforded either 5-(1,2,3-triazol)-1-yl-or 5-amino-7-nitroquinolines, which have been previously inaccessible by using other methods.Scheme1.Synthesis of 5,7-dinitroquinolines 1 and 2 (DMF = N,N-dimethylformamide). [a] Dr.A .M.S tarosotnikov,V .V .Nikol'skiy,A.N.B orodulya, Dr.Scheme2.Reactions of 5,7-dinitroquinolines with O-and N-nucleophiles. Scheme3.Reactions of 5,7-dinitroquinolines with thiols. Scheme4.Nucleophilic aromatic substitution of the nitro group(Nu = nuclophile).
An efficient method was developed for the synthesis of novel pyrido[2, 3-a]phenoxazines and phenothiazines. The base-promoted reaction of 8-chloro-5,7-dinitroquinoline with binucleophiles (o-aminophenols and o-aminothiophenols) results in substitution of the chlorine atom followed by replacement of the nitro group. In case of aminothiophenols the products of in situ Smiles rearrangement were isolated.
One of the most important and flexible tools for nitroarenes functionalization is nucleophilic aromatic substitution (SNAr). This reaction generally requires number of conjugated electron-withdrawing groups and SNAr of non-activated nitro groups is rather uncommon. Most of these examples were obtained on polynitrobenzenes, but little is known about reactions of nonactivated 3-nitropyridines. Here we report synthesis of several 2-methyl-3-nitropyridines and their reactions with various aromatic aldehydes, leading to corresponding 2-styrylpyridines under mild conditions. Both 2-methyl-and 2-styryl-3-nitropyridines readily react with thiolate-anions and give substitution products in good yields. Chemo-and regioselectivity is discussed, some of 2styrylpyridines also showed remarkable fluorescent properties.
An efficient method for the synthesis of pyrazolo [4,3-b]pyridines has been developed on the basis of readily available 2-chloro-3-nitropyridines via a sequence of SNAr and modified Japp–Klingemann reactions. The method offers a number of advantages including utilization of stable arenediazonium tosylates, operational simplicity as well as combining the azo-coupling, deacylation and pyrazole ring annulation steps in a one-pot manner. An unusual rearrangement (C-N-migration of the acetyl group) was observed and a plausible mechanism was proposed based on the isolated intermediates and NMR experiments. In addition, the developed protocol was successfully applied to the synthesis of 1-arylindazoles combining the Japp–Klingemann reaction and cyclization of the resulting hydrazone as a one-pot procedure.
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