Pyridine with formic acid

Thiation of [l,2,4]triazino[3,2-h]quinazoline-3,10-dione 782 with phosphorus pentasulfide in pyridine proceeded selectively to give the 3-thioxo analogue 783. The latter was converted to the corresponding 3-methylthio derivative 784 by reaction with methyl iodide. Treatment of 784 with hydrazine gave 785, which was converted to 786 and 787 by cyclization with formic acid or carbon disulfide (90JHC591). Cyclization of 785 with sodium nitrite in hydrochloric acid gave 788 (90JHC591). 

This reduction has also been achieved by treating the nitrile with sodium hypophosphite (NaH2P02 ) and Raney nickel in aqueous acetic acid - pyridine or formic acid. 

The pyridine ring is easily reduced in the form of its quaternary salts to give hexahydro derivatives by catalytic hydrogenation [446], and to tetrahydro and hexahydro derivatives by reduction with alane aluminum hydride) [447], sodium aluminum hydride [448], sodium bis 2-methoxyethoxy)aluminum hydride [448], sodium borohydride [447], potassium borohydride [449], sodium in ethanol [444, 450], and formic acid [318]. Reductions with hydrides give predominantly 1,2,5,6-tetrahydro derivatives while electroreduction and reduction with formic acid give more hexahydro derivatives [451,452]. 

LiAIH(OEt)3,345 DIBALH,346 and NaAIH4.347 The metal hydride method is useful for aliphatic and aromatic nitriles. Reduction to the aldehyde has also been accomplished by treatment of the nitrile with sodium hypophosphate and Raney nickel in aqueous acetic acid-pyridine or formic acid,348 and with zinc and a Cob(I)alamin catalyst in aqueous acetic... 

The Me2SO-oxalyl chloride method34 was successfully used13 to obtain2-(6-deoxy-2,3-0-isopropylidene-a-L-h/xo-hexopyranosyl-4-ulose)-8-nitro-t>-triazolo[l,5-fl]pyridine (49a) in 62% yield from the partially protected L-rhamnose nucleoside 48a. Treatment of 49a with formic acid gave the free ketonucleoside 50a. Hydrogenation over 10% Pd-C afforded the amino derivative 49b. 

Pyrazole incorporation was effected by reaction of hydrazine with poly(diethynylbenzene) (190 Scheme 91) (72MI11108). The pyrazole-functional adduct (191) was a white, fibrous material soluble in DMF, DMSO, pyridine and formic acid. Films of the polymer were quite strong and were equally stable in air or nitrogen, with decomposition occurring at ca. 450 °C. 

The commonly encountered compounds in this class are the formyl, acetyl and benzoyl derivatives. The formation of the N-formyl compound is readily accomplished by heating the amino compound with formic acid in the presence of acetic anhydride.223 Alternatively, formic acid in the presence of dicyclohexl-carbodiimide (DCC) in pyridine solution is a suitable method for the protection of amino acid esters.224... 

Sodium p-aminosalicylate dihydrate (21.1 g.) and D-glucose (19.8 g.) were dissolved in water (100 ml.) and the solution was brought to pH 5.5 with formic acid. After 3 days at room temperature, the solution was cooled to 0°, treated with 10% formic acid, and allowed to stand for one hour at 0° to crystallize. Colorless needles (29 g., 92% yield) were isolated m. p., 152° with browning but no liberation of gas [a]D —143° (in pyridine). 

The fluorination of quinoline was performed in a microstructured reactor operated in the annular-flow regime, which contained one microchannel with two consecutive feeds for gas and liquid [311,312]. The role of the solvent was large. The reaction was totally unselective in acetonitrile and gave only tarlike products. With formic acid, a mixture of mono- and polyfluorinated products besides tar was formed. No tar formation was observed with concentrated sulfuric acid as solvent at 0-5 °C. In this way, a high selectivity of about 91% at medium conversion was achieved. Substitution was effective only in the electron-rich benzenoid core and not in the electron-poor pyridine-type core. The reactivity at the various positions in the quinoline molecule is 5 > 8 > 6 and thus driven by the vicinity to the heteroatom nitrogen that corresponds to the electrophilic reactivity known from proton/deuterium exchange studies in strong acid media. 

A special type of pseudo-polymorphism is that related to the proton transfer along an X-H Y interaction. The motion may not be associated with a phase transition, but may well imply the transformation of a molecular crystal into a molecular salt. Wilson [34] has discussed, on the basis of an elegant neutron diffraction study, the migration of the proton along an O-H O bond in a co-crystal urea-phosphoric acid (1 1) whereby the proton migrates towards the mid-point of the hydrogen bond as the temperature is increased, becoming essentially centred at T > 300 K. Wiechert and Mootz [35] isolated two crystalline materials composed of pyridine and formic acid of different composition. In the 1 1 co-crystal the formic acid molecule retains its proton and transfer to the basic N-atom on the... 

Piperideines unsubstituted at the nitrogen atom may be prepared from the corresponding pyridine compounds by partial reduction with sodium and boiling alcohols (the Ladenburg reduction), by electrolytic reduction, or, preferably, by reduction with aluminum hydride. l-Alkyl-3-piperideines are prepared by reduction of quaternary pyridinium salts with formic acid (the Lukes reduction) or with complex hydrides. 

Reduction of quaternary pyridinium halides (or, more precisely, formates) with formic acid in the presence of potassium formate at about 150°C is usually referred to as the Lukes reduction.80-95 Instead of potassium formate, triethylamine may be used, especially with quaternary pyridinium iodides.85,86 Mixtures of l-alkyl-3-piperideines (77) and 1-alkylpiperidines (78) are usually obtained. Formation of piperideines (77) might be explained by analogy with the Ladenburg reduction of pyridine bases the double bond at position 3 is resistant toward further reduction by formic acid or by... 

B. R. Lakshmanan. J. Indian Inst. Sci. 36A, 218-23 (1954). Raman binary mixtures of pyridine with formic, propionic, and butyric acids. 

Fic. 3. Chromatographic fractionation of a mixture of tryptophan metabolites on an ion-exchange column of Amberlite IR-120 ( 28 X 0.9 cm). The temperature was held at 37 °C and the flow rate was adjusted at 12 ml per hour with formic acid-pyridine buffers. The metabolite concentration is given as (ig/ml after fluorometric readings. Effluent was collected in 2-ml fractions. The following abbreviations are used KA, kynurenic acid XA, xanthurenic acid AHA, o-aminohippuric acid K, kynurenine 30HAA, 3-hydroxyanthranilic acid 30HK, 3-hydroxykynurenine. 

The polymerization of fluoral [61] has been studied in detail by Busfield [64]. It was found that fluoral polymerized very slowly in the presence of 2 mole % of formic acid but extremely quickly in the presence of as little as 0.2 mole % of a tertiary amine such as pyridine or trimethyl amine. Gasphase polymerization of fluoral was studied with trimethyl amine and it was found that the ceiling temperature was 73°C. The half life (50% conversion to polymer) of fluoral polymerization with formic acid was 12 h but for pyridine or trimethyl amine it was about 30 sec. 

Polymer-bound isonitrile (423), obtained from TentaGel-NH2 through treatment of the resin with formic acid and acetic anhydride, followed by dehydration of the resulting formamide with tosyl chloride and pyridine, has been employed in the preparation of N-substituted amino add ester [349]. Thus, Ugi MCR, performed in the presence of an alcohol instead of the carboxylic component, gave rise to an imino-ether spedes (426). Several Lewis acids were tested in searching for optimal reaction conditions. Boron trifluoride etherate displayed the better yields in term of desired product of the Ugi-type reaction. Amino acid methyl esters (427) were thus obtained when using methanol as the alcohol component, after deavage from the resin of the intermediate imino-ethers by an acetone/water mixture (Scheme 87). 

Buiten (108), studying distillation problems, observed that a mixture of pyridine and formic acid evolved carbon monoxide when heated to about 150°C. We repeated this experiment, using a 1 1 (weight) mixture of y-pycoline and formic acid and a mixture of triethylene diamine and formic acid. In both cases the gas evolved principally contained CO. In the latter case also 4% H2 -f 4% C02 was present in the CO evolved. Although these basic compounds can form salts with formic acid (as is evident from the high boiling points), the decomposition products are practically identical with those formed in acid media. 

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