2- amino pyridin

Note that p-acetamidobenzenesulphonyl chloride will similarly react with primary and secondary amines, and the products, after hydrolysis of the acetyl group, may furnish notable drugs e.g., the condensation products with 2-amino-pyridine and 2-aminothiazole, after remo al of the acetyl groups, provide the drugs commonly known as sulphapyridine (M B 693) and sulphathidzole respectively. 

Reaction of 2-cyano-3-(4-methoxyphenyl)acroyl chloride and 2-amino-pyridine in boiling benzene in the presence of NEt3 for 5 h gave a 2 1 mixture of 3-cyano-4-(4-methoxyphenyl)-3,4-dihydro-2//-pyrido[l, 2-n]pyr-imidin-2-one and 2- [2-cyano-3-(4-methoxyphenyl)acroyl]amino pyridine (01SUL151). 

Reaction of 2 equiv of 2-aminopyridines with 2-hydropolyfluoroalk-2-anoates 351 in MeCN in the presence of NEts at 90 °C for 50 h afforded a mixture of the isomeric 2-oxo-2H- and 4-oxo-4//-pyrido[l,2-n]pyrimidines 110 and 111. Reaction of 3 equiv of 2-amino-pyridines and 2-hydropoly-fluoroalk-2-enoates 351 in MeCN in the presence K2CO3 could be accelerated by ultrasonic irradiation (125W). 2-Amino-6-methylpyridine yielded only 2-substituted 6-methyl-4//-pyrido[l,2-n]pyrimidin-4-ones 111 (R = 6-Me), whereas 2-amino-5-bromopyridine gave a mixture of 7-bromo-4//-pyrido[l,2-n]pyrimidin-4-one (111, R = 7-Br, R = CF2C1) and 2-(chlor-o,difluoromethyl)-6-bromoimidazo[l, 2-n]pyrimidine-3-carboxylate in 44 and 8% yields, respectively (97JCS(P 1)981). Reactions in the presence of K2CO3 in MeCN at 90°C for 60h afforded only imidazo[l,2-n]pyrimidine-3-carboxylates. 

Almost accidentally, Bienayme and Bouzid discovered that heterocyclic amidines 9-76 as 2-amino-pyridines and 2-amino-pyrimidines can participate in an acid-catalyzed three-component reachon with aldehydes and isocyanides, providing 3-amino-imidazo[l,2-a]pyridines as well as the corresponding pyrimidines and related compounds 9-78 (Scheme 9.15) [55]. In this reachon, electron-rich or -poor (hetero)aromatic and even sterically hindered aliphatic aldehydes can be used with good results. A reasonable rahonale for the formation of 9-78 involves a non-con-certed [4+1] cycloaddition between the isocyanide and the intermediate iminium ion 9-77, followed by a [1,3] hydride shift. 

Likewise, an efficient one-pot multicomponent synthesis of annelated 2-amino pyridines (e.g., 17) utilizing [4+2] cycloadditions has been described <06JOC3494>. The process involves the in situ generation of 1-aza-1,3-butadiene from a palladium-catalyzed coupling-isomerization reaction of aryl halides (e.g., 18) with propargyl V-tosylamines (e.g., 19). The resulting butadiene then undergoes cycloadditions with V.S -ketene acetals (e.g., 20) to form annelated pyridines (e.g., 17). 

Isopropylidene /V-(3-benzyloxy-2-pyridyl)- and /V-(5-benzyloxy-4-pyri-midinyl)aminomethylenemalonates were prepared in the reactions of isopropylidene methoxymethylenemalonate (420) with 3-benzyloxy-2-amino-pyridine or 5-benzyloxy-4-aminopyrimidine (89TL1529). 

Laser-based refractive index detector, Cuprammonium reagent,4-Aminobenzoic acid reagent, Indirect detection methods for cyclodex-trins, and sugar phosphates Reversible derivatization using 2-amino-pyridine ... 

Sulfapyridine Sulfapyridine, iV -(2-pyridyl)-sulfanilamide (33.1.21), is also synthesized by an analogous scheme from 4-acetylaminobenzenesulfonyl chloride and 2-amino-pyridine [21-23]. 

Setzt man als Amidin-Komponente Amino-hetarene (z. B. 2-Amino-pyridine, 2- bzw. 4-Amino-pyrimidine) ein, so erhalt man Imidazole, bei denen liber die Positionen 1 und 2 des Imidazol-Rings ein heterocyclischer Ring anelliert ist96 98 ... 

Bei der Einwirkung von Phosgcn auf 2-Amino-pyridin-N-oxid erfolgt glatte Cyelisierung ohne Isolierung einer Zwischenstufe unter Bildung von 2-Oxo-2II-yrido[l,2-b]-],2,4-oxadiazol (Schmp. 185-1870)84 ... 

Diamino- und 2,4-Diamino-pyridin werden in salzsaurer Losung in guten Ausbeuten mit diazotiertem 2-Amino-pyridin bzw. Phenyldiazoniumchlorid gekuppelt2 ... 

Aryl-glyoxylsaure-arylhydrazonid-bromide reagieren mit 2-Amino-pyridin in Ethanol zu... 

Fig. 13.2. Illustration of the basic concept of Basis Products, (a) The PGVL reaction scheme of VRXN-2-00051 (formation of the H-imidazo[1,2-a]pyridine ring system using aminoheterocycles and alpha-halo ketones) is used for the illustration (b) The Basis Products of A are formed by all A reactants with one constant reactant (B CAP, 1 -bromopropan-2-one). The Basis products of are formed by all reactants with a constant A reactant (A CAP, 2-amino pyridine). The blue triangle and yellow hexagon represent two such basis products. The red star represents a product molecule which is related to those two corresponding basis products.

Reaction of 2-aminopyridine and the ketene mercaptals (92) in the presence of sodium ethoxide gave the 2-methylthio derivatives (93).161,162 2-Amino-pyridine and 2-phenyl-4-ethoxymethylene-5-oxazole gave the condensation product 94, which in the presence of sodium ethoxide at room temperature isomerized to 3-benzamido-4-oxo-4H-pyrtdo[l,2-< /]pyrimidine.163... 

Oxo-2//-pyrido[l,2- ]pyrimidines are easily hydrolyzed to 2-amino-pyridines on heating with alkalis.21... 

Tsuge and Noguchi469 prepared the 3-benzamido-4-oxo-4//-pyrido-[l,2-a]pyrimidine and its methyl substituted derivatives from 2-amino-pyridines and 2-phenyl-4-ethoxymethylene-5-oxazolone in boiling ethanol, without the isolation of the condensation products of type 94. The pyrido-pyrimidine was formed from 2-amino-6-methylpyridine, but in a longer reaction period and in low percentage yield. Condensation product 94 was cyclized in ethanol or polyphosphoric acid or acetic acid. 3-Benzamido-2-methyl-4-oxo-4A/-pyrido[l,2- ]pyrimidine was synthetized from 2-amino-pyridine and the appropriate oxazolone derivative. 

Iminophosphoranes typically form N,P-chelates 390. For the compounds with mixed phosphino- and amino-functions, apart from expected N,N,P-chelation 391, there are frequent cases when an amino group is excluded from coordination, 392 and 393. Diphenylphosphino-2-amino-pyridine may exhibit various co-ordination modes, monodentate 394, neutral and anionic chelating, 395 and 396, and bridging 397. Other chelating environments may be classical pincer 398, P,P- 399, or double 400. Also, transformation from the monodentately coordinated 401 to the bridging heterodinuclear 402 occurs quite frequently. 

In one prominent example such an unexpected reaction product was observed in three research laboratories independently. During attempts to synthesize a library of Ugi-type four-component products using various isonitriles, aldehydes, acids and amines the reaction did not gave the desired Ugi-type four-component reaction product when amino pyridine-like starting materials were used as the amine component. In the case of such 2-amino pyridine-type amines the clean formation of... 

Table 27. Selected examples of correlation between observed and calculated UV transitions (Del Bene and Jaffe). (Other studied compounds include benzene, pyridine, 1,2-diazine, 1,3-diazine, 1,4-diazine, cyclopentadienide ion, pyrazole, imidazole, 2-pyrrole-carboxaldehyde, furfural, benzonitrile, nitrosobenzene, phenol, phenoxide ion, pyridinium ion, 1-hydroxy-pyridinium ion, 2-cyano-pyridine, 3-cyano-pyridine, 4-cyano-pyridine, 2-amino-pyridine, 3-amino-pyridine, 4-amino-pyridine.)...

Amination of 3-nitropyridine with potassium permanganate in liquid ammonia, or an aliphatic amine, affords the 2-amino-pyridine 157 (Equation 83) <1999JPR75>. The nitropyridine 158 is aminated at C-6 with O-methylhy-droxylamine in the presence of ZnCl2 to give 159 in high yield (Equation 84) <1998CC1519>. 

In the photometric determination of copper, a coupling product formed between the diazonium salt from 2-amino-pyridine and resorcinol, or 4-(2-pyridinylazo)-l,3-benzenediol 21, has been used. Here the formed copper complex under acetate buffer exhibits an absorption peak at 520 nm, which is measured photometrically <2003KPU28>. Similarly for photometric determination of iron(ll), a coupling product formed between the diazonium salt of 2-amino-4,6-dihydroxypyrimidine and 8-hydroxyquinoline, or 6-hydroxy-2-(8-hydroxy-7-quinolinyl)azo-4(l//)-pyrimidinone 22, has been used. This reagent forms a blue complex with iron(n) ions with an absorption maximum at 625 nm that does not interfere with the presence of other metals <2003KD95>. 

The reaction of sodium alkylamides with pyridine gives 2-amino-pyridine derivatives,301 but this does not appear to have been exploited with substituted pyridines. Similarly, pyridine gives 2-hydrazinopyridine on treatment with sodium hydrazide/hydrazine followed by hydrolysis.301 ... 

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