A-Aminopyridine

The structure of malonyl-a-aminopyridine (cf. 121) has been discussed by Snyder and Robinson/ who interpreted the infrared and ultraviolet spectra and the fact that it could be converted into a monochloro derivative (122, R = Cl) to indicate that the intra-molecularly hydrogen-bonded hydroxy form 122 (R = OH) was predominant. However, comparison of the basicities of the methoxy compound 122 (R = OMe), the mesomeric betaine 123 (R = Me), and the parent compound indicates that in aqueous solution the last exists mainly in the zwitterion form 123 (R = H), ... 

The reaction is not limited to Z—CH2—Z compounds. Other acidic CH hydrogens, which include, for example, the methyl hydrogens of a-aminopyridines, the methyl hydrogens of ynamines of the form CH3CSCNR2 (the product in this... 

Synonyms AI3-15287 Amino-2-pyridine a-Aminopyridine o-Aminopyridine BRN 0105785 l,2-Dihydro-2-iminopyridine CCRIS 4747 EINECS 207-998-4 NSC 431 2-Pyridinamine Pyridinamine a-Pyridylamine 2-Pyridylamine UN 2671. 

Aminopropane, see Isopropylamine Amino-2-pyridine, see 2-Aminopyridine a-Aminopyridine, see 2-Aminopyridine o-Aminopyridine, see 2-Aminopyridine 2-Aminotoluene, see o-Toluidine o-Aminotoluene, see o-Toluidine Ammonia anhydrous, see Ammonia Ammonia gas, see Ammonia Amoxone, see 2,4-D... 

Problem 20.25 Explain why (a) pyridine and NaNH give a-aminopyridine, (f>) 4-chloropyridine and NaOMe give 4-methoxypyridine, (c) 3-chloropyridine and NaOMe give no reaction. 

Chichibabin96 prepared the first representatives of pyridopyrimidines of type 63. Instead of assuming the 63 zwitterionic form, Chichibabin used the 2,4-dioxo structure and named the compounds malonyl-a-aminopyridines. 

Malonyl-a-aminopyridine 37 was prepared in 45% yield when malonic acid was reacted with 2-aminopyridine in boiling pyridine in the presence of mole equivalents of benzenesulfonyl chloride for 15 minutes (83MI19). Malonyl-a-aminopyridine 37 was also obtained in the reactions of 2-aminopyridine and excess diethyl malonate by heating in the absence of a solvent. 9-Methyl-, 9-chloro-, and 7-methyl derivatives 109 (R = 9-Me, 9-C1, 7-Me) were prepared from the appropriate 2-aminopyridine and diethyl malonate in boiling xylene in 20-53% yields (90ZC98). 

Different malonyl-a-aminopyridines 110 (R = H, Me) were prepared from 2-aminopyridine and its methyl-substituted derivatives with diethyl 2-substituted malonates at 160-180°C with continuous distillation of the ethanol formed, or with bis(2,4,6-trichlorophenyl) 2-substituted malonates in acetone under reflux, or at ambient temperature in the presence of triethylamine (91T675). 

Chloro-4//-pyrido[ 1,2-a]pyrimidin-4-one 370 (R = H) was obtained in the reaction of malonyl-a-aminopyridine 37 and phosphoryl chloride at 100°C (92MI23). 

Nitrosation of malonyl-a-aminopyridine (37) in 2 N hydrochloric acid at 0°C with a 1 N aqueous sodium nitrite afforded the 3-nitroso derivative 329 [91IJC(B)839]. 2-Amino-3-nitroso-4//-pyrido[l,2-a]pyrimidin-4-one was prepared from 2-amino-4//-pyrido[l, 2-a]pyrimidin-4-one by treatment of 1 N sodium nitrite in 2 N hydrochloric acid at 0°C for 30 minutes (92MI23). 

Malonyl-a-aminopyridine (37) reacted with aryldiazonium chloride in ethanol in the presence of sodium acetate to give 3-arylhydrazono-2,4-dioxopyrido[ 1,2-a]pyrimidines (89MI6). Heating compound 37 in for-... 

Reactions of malonyl-a-aminopyridines 109 with excess aromatic aldehydes at reflux for 10-30 minutes afforded tricyclic pyridopyranopyrimi-dines 467 (90ZC98). In the first step of the reaction condensation product 466 was formed, which reacted with ketene in a (4 + 2)-cycloaddition to yield tricyclic compounds 467. Ketene was formed by decomposition of another molecule of malonyl-a-aminopyridine 109 together with the... 

The electrochemical behavior of malonyl-a-aminopyridines 661 was investigated by Gullu et al. in acetonitrile or a mixture of trifluoroacetic acid and dichloromethane containing tetrabutylammonium tetrafluoro-borate or triethylammonium trifluoroacetate in a water-jacketed, two-compartment glass cell equipped with a platinum disk anode at 1.50 V (Ag/ Ag+) and a carbon-rod secondary electrode (91T675). Controlled potential anodic oxidation of 661 afforded labile coupled carboxylic acids 662 (R2 = COOH), which easily decarboxylated to compounds 662 (R2 = H) under the work-up conditions. Sometimes, the carboxylic acid 662 (R2 = COOH) could be isolated or when the reaction mixture was treated with methanol, methyl ester 662 (R = H, R1 = Bu, R2 = COOMe) was obtained in 40% yield. 

The application of malonyl-a-aminopyridine (37) was claimed in shampoo as a coupler (81GEP3009833). The 3-butyl derivative of malonyl-a-aminopyridine (694, R = Bu) inhibited senescence of illuminated soybean seedlings under low carbon dioxide conditions, but did not decrease leaf light transmission at ambient carbon dioxide levels (84MI14). 3-Arylazo derivatives of malonyl-a-aminopyridine (694, R = Ar—N= N—) are used as dyestuffs, and the effect of the substituents of the aryl ring on the color of azo dyes was investigated (89MI6). 

Similarly, a novel one-pot microwave-assisted reaction has been described by Hulme and co-workers that enables the selective formation of 3-iminoaryl-imidazo[l,2-a]pyridines 19 and imidazo[l,2-a]pyridyn-3-ylamino-2-acetonitriles 20, in good yields. Reactions were performed in methanol by mixing a suitable a-aminopyridine, an aldehyde and trimethylsilylcyanide (TMSCN) with polymer-bound scandium triflate, to afford either product 19 or 20 (Scheme 16). Initially, the 3-iminoaryl-imidazo[l,2-a]pyridine 19, was observed as a minor side product (0-10%) during the pseudo-Ugi reaction affording the 3-aminoimidazo[l,2-a]pyridine 18. However, by increasing the aldehyde input to 2.2 equiv the reaction could be directed to the formation of 19 in moderate yields. Interestingly, low yields of... 

SYNS o-AMINOPYRIDINE a-AMINOPYRIDINE AMINO-2-PYRIDINE o-PYRIDINAMINE a-PYRIDYLAMINE... 

SYNS AH ANISOPYRADAMINE ANTHISAN MALEATE ANTIHIST N-DIMETHYLAMINOETHYL-N-p-METHOXY-a-AMINOPYRIDINE MALEATE 2-((2-piMETHYLAMINO)ETHYL)(p-METHOXYBENZYL)-AMINO)PYRIDINE BIMALEATE 2-((2-piMETHYL-AMINO)ETHYL)(p-METHOXYBENZYL)AMINO)-PYRIDINE MALEATE NJSI-DIMETHYL-N -(4-METHOXYBENZYL)-N -(2-PYRIDYL)ETHYLENEDI-AMINE MALEATE HISTATEX MEPYRAMINE MALEATE N-p-METHOXYBENZYL-N -N -DIMETHYL-... 

AMINOPYRIDINE see AMIOOO p-AMINOPYRIDINE see AMI500 m-AMINOPYRIDINE (DOT see AMI250 a-AMINOPYRIDINE see AMIOOO Y-AMINOPYRIDINE see AMI500... 

Multicomponent reactions have been described for several syntheses of imidazoles. Highly efficient methods for the syntheses of spiroimidazolinones via microwave-assisted three-component one-pot sequential reactions or one-pot domino reactions have been described <06JOC3137>. Multicomponent reactions between 2-aminopyrimidine, aldehydes and isonitriles afforded imidazo[l,2-a]pyrimidines <06TL947>. Two novel one-step microwave mediated syntheses of arrays of 3-iminoaryl-imidazo[l,2-a]pyridines and imidazo[l,2-a]pyridyn-3-ylamino-2-acetonitriles were synthesized by multicomponent reactions under microwave condition in methanol by simply mixing a-aminopyridines, aldehydes, and trimethylsilylcyanide catalyzed by polymer-bound scandium triflate <06TL2989>. 3-Aminoimidazo[l,2-a]pyridines have been synthesized via the multicomponent reaction of aldehydes, isocyanides and 2-aminopyridines in the presence of the ionic liquid l-butyl-3-methylimidazolium bromide [bmim]Br<06TL3031>. 

---