NitropyridineS. 9*. Synthesis of substituted 3-amino-5-nitropyridines

Abstract

The discovery of bacteriostatic activity of Sulfidine was the stimulus for the study of the chemistry of isomeric aminopyridines with the objective of converting them into promising sulfamide preparations [2].Aminopyridines with nitrogroups on the pyridine nucleus have been insufficiently well studied, which is explained by their low accessibility. Exceptions are 2-amino-3-nitro-and 5-nitropyridines and their derivatives, which are accessible thanks to the activity of 2-aminopyridine to electrophilic substitution [3]. The number of publications connected with the preparation of substituted 3-amino-5-nitropyridines is limited to those describing the synthesis of 3-amino-5-nitropyridine [4-7], 3-amino-2-methyl-5-nitropyridine [8], and 3-amino-5-nitrocollidine [9].The objective of the present work was the synthesis of the previously unknown 3-amino-5-nitropyridines 2a,b, 4, 6b,c, and 9a-c based on the available nitropyridines 1a,b, 3a-c, and 7a-c which contain acetyl, amide, and carboxyl groups at position 3 of the pyridine nucleus, The choice of the variant of the sextet rearrangement in the synthesis of 3-amino-5-nitropyridines was determined by the availability of the corresponding 5-nitropyridines. 3-Amino-5-nitropyridines 2a,b were obtained by the Schmidt reaction starting from 3-acetyl-5-nitropyridines 1a,b by a one-stage synthesis which we had developed earlier [10,11]: N Ac O 2 N Me R N NH 2 R Me O 2 N 1. NaN 3 , H 2 SO 4 2. H 2 O,  1a,b 2a,b 1,2 a R = Me, b R = Ph

The rearrangement of 3-nitropyridinium salts to 3-nitropyrroles

“…38 We returned to this reaction after developing a convenient method of synthesis of the initial 3-amino-5-nitropyridines 1, which were previously unknown. 39 The starting 3-benzoylamino-5-nitropyridines 2 were synthesized by benzoylation (SchottenBaumann reaction) of 3-amino-5-nitropyridines 1 with benzoyl chloride ( The necessary pyridinium salts 3a-e were obtained by alkylation of pyridines 2a-e with dimethyl sulfate and methyl fluorosulfonate. Hygroscopic pyridinium methyl sulfates were transformed into the less-soluble pyridinium perchlorates 3 by replacement of the methyl sulfate anion to perchlorate ( Table 2).…”

Unexpected Formation of 5‐Nitro‐1H‐benzimidazoles by Nucleophilic Recyclization of 1‐Methyl‐5‐nitropyridinium Salts

“…Pyridines ( 2a , 2b , 2c ) were synthesized via benzoylation of 3‐aminopyridines ( 1a , 1b , 1c ) (Schotten–Baumann reaction). 3‐Aminopyridines ( 1a , 1b , 1c ) were obtained earlier by different sextet rearrangements (Curtius, Hofmann, and Schmidt rearrangements) and described in our previous work . Pyridinium salts ( 3a , 3b , 3c ) were synthesized via alkylation of 3‐benzoylamino‐5‐nitropyridines ( 2a , 2b , 2c ) by dimethyl sulfate and fluorosulfuric acid methyl ester (Scheme ).…”

“…Monitoring of the course of reactions and purity of the compounds obtained was by TLC on Silufol UV‐254 plates. 3‐Aminopyridines ( 1a , 1b , 1c ) was synthesized according to the procedures described in .…”

“…Benzoyl chloride 1.08 g (7.7 mmol) was added dropwise to a solution of 3‐aminopyridine ( 1a , 1b , 1c ) (7 mmol) in absolute pyridine (5 mL) at 0°C. The mixture was stirred 10 min at 0°C and then 2 h at RT.…”