Pyridinium hydroxide

Improved procedures for the Chichibabin amination of pyridine derivatives have been reported (83JAP(K)58-208266, 83USP4386209, 83USP4405790). A general method has been developed for the conversion of 2-aminopyri-dines into 2-pyridones via 2-cthoxycarbonyl-l-(2-pyridyl)pyridinium ions 15. The pyridinium ions 15 are easily made from the 2-aminopyridines 14 and the corresponding pyrylium salt 13. On treatment with aqueous sodium hydroxide, pyridinium ions 15 are converted into the l-(substituted-2-pyridyl-carbonyl)-2-pyridones 16, which are readily hydrolyzed to the 2-pyridones 17 and the picolinic acid 18 (83JCS(P1)2623). 

An acidimetric quantitative determination is based on treatment of the hydantoia with silver nitrate and pyridine ia aqueous solution. Complexation of the silver ion at N-3 Hberates a proton, and the pyridinium ions thus formed are titrated usiag phenolphthaleia as an iadicator. In a different approach, the acidity of N-3—H is direcdy determined by neutralization with tetrabutylammonium hydroxide or sodium methoxide ia dimethylformarnide. 

Pyridinium hydroxide, anhydro-4-mercapto-2,8-methoxyphenyl-6-oxo-1,3-diphenyl-synthesis, 6, 343... 

Thiadiazolo[4,5-d]pyridinium hydroxide, anhydro-3,6-dimethyl-5-hydroxy-7(6)-oxo-... 

Thiazolo[3,2-a]pyridinium hydroxide, anhydro-7-bromo-3a-carboxy-2,3-dihydro-8-hydroxy-2ft5-dimethyl-l 0-0X0-X-ray diffraction, 6, 670... 

Thiazolo[3,2,-a]pyridinium hydroxide, anhydro-8-hydroxy-photolysis, 6, 682... 

The addition (150-157) of Grignard reagents, alkoxides, hydroxide, sulfides, cyanide, and enolate anions to pyridinium and isoquinolinium salts again provides a variety of cyclic enamines of potential synthetic use. 

Combination of the hydroxyl ion with the mesomeric cation involves the removal of a double bond. For the quaternary pyridinium compounds this causes the total loss of the aromaticity. For quaternary quinolinium and isoquinolinium compounds, the aromatic character of one of the two rings is lost, and for the quaternary acridinium compounds that of one out of three. Hence., the order of stabilities of these compounds (determined by Hantzsch ) is explained. - Comparison of quaternary 3,4-dihydroisoquinolinium compounds and their isoquinolinium analogs with respect to the equilibrium (5) (4) shows that a much higher hydroxyl ion concentration is necessary for the isoquinolinium ions to form the carbinolamine. This is because the transition from the quaternary 3,4-dihydroisoquinolinium ions into the undissociated carbinolamine involves significantly smaller loss of mesomeric energy than that for the quaternary isoquinolinium hydroxides. ... 

Methyl- and 4-methyl-pyridinium methiodides yield cyanine-type dyes with chloroform and alcohohc potassium hydroxide, e.g. via the methylene dihydropyridine (51) with attack by dichlorocarbene at the active methylene group (cf. ref. 92a). 

A different type of denitrocyclization reaction reported by Krohnke et al. involving C-nucleophiles is represented by treatment of some A-(2,4,6-trini-trobenzyl)pyridinium salts, e.g. 168, with sodium hydroxide providing high... 

Methylation of nicotine to the pyridinium iodide with methyl iodide, followed by its conversion to the hydroxide with silver oxide in water, oxidation with potassium permanganate to the A -methyl nicotinic acid hydroxide and subsequent deprotonation with silver oxide yielded Trigollenine as colorless needles (1897CB2117). In a later publication, the formation of nicotinic acid from nicotine was described. Esterification followed by aminolysis and methylation yielded the A -methylnicotinamide... 

Theoretical calculations (B3LYP/6-31G ) indicated that in their NMR spectra C(2) and C(9) carbons of n /2ydro-(2-hydroxy-4-oxo-4//-pyrido[l,2-n]pyrimidinium)hydroxide mesoionic forms appeared at significantly higher field (ca. 159-160 ppm and 115-116 ppm, respectively), than in the 2-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-one tautomers (ca. 169-173 ppm and 130 ppm, respectively) (00JCS(P2)2096). C(8) carbon of mesoions (pyridine-y type carbon) appeared at lower field (144-146 ppm) than 6-C (140 ppm, pyridine-o type carbon), as is typical of pyridinium compounds. 

The solid state structures of anhydro-(3-methy - and 3-phenyl-2-hydroxy-4-oxo-47/-pyrido[l,2-n]pyridinium)hydroxides, 2-methoxy-3-methyl-47/-and 2-(2-pyridylamino)-47/-pyrido[l, 2-n]pyrimidin-4-ones were established by X-ray diffraction analysis. The amide type N(5)-C(4)-0 bonds are unusually long (144-149 pm) showing no sign of an amide type conjugation. 

Methoxy-4//-pyrido[],2-n]pyrimidin-4-one was prepared from 2-chloro-4//-pyrido[],2-n]pyrimidin-4-one with NaOMe in MeOH for 16h, and from n /iyJro-(2-hydroxy-4-oxo-4//-pyrido[l, 2-n]pyridinium)hydroxide with Me2S04 in the presence of NaOMe in MeOH for 3h at room temperature in 93% and 41% yields, respectively (99JCS(P2)1087). 2-(2-Hydroxyethoxy)-4//-pyrido[],2-n]pyrimidin-4-one was prepared from the 2-chloro derivative with HOCH2CH2OH in the presence of K2CO3 at 160 °C for 1 h (00BMC751). 

Chemical Name (6R-trans)-1-[ [2-Carboxy-8-oxo-7-[(2-thienylacetyl)amino] -5-thia-1-azabi-cyclo[4.2.0]oct-2-en-3-yl] methyl] pyridinium hydroxide inner salt... 

B) Preparation of 2-(Hydroxyiminomethyl)-1-Methyl Pyridinium Chloride An aqueous solution of 15 ml of 1-methyl-2-picolinium chloride having a concentration of 477 mg/ml Is covered with 50 ml of benzene in an atmosphere of nitrogen and cooled to below 10°C. An aqueous solution of sodium hydroxide is added dropwise and the mixture is stirred for 5 minutes and allowed to stratify. The aqueous phase Is then drawn off and the benzene solution is added slowly to a solution of 3 ml of nitrosyl chloride in 175 ml of benzene containing 0.5 ml of dimethyl formamide at about 10°C in an atmosphere of nitrogen with good agitation. The mixture is then stirred for 1.5 hours and then extracted with four... 

Glutaconaldehyde (8) 2-Pentenedial (9) (821-42-1) Glutaconaldehyde, sodium salt, dihydrate Glutaconaldehyde, ion (1 ) sodium (8) 2-Pentenedial, ion (1 ), sodium (9) (24290-36-6) Pyridinium-1-sulfonate Pyridinium, 1-sulfo-, hydroxide, inner salt (8,9) (42824-16-8)... 

In a 500-ml., three-necked, round-bottomed flask fitted with a mechanical stirrer and a thermometer is placed 42 g. (1.05 mole) of sodium hydroxide dissolved in 168 ml. of water. The contents of the flask are cooled to —20° and stirred vigorously as 48 g. (0.30 mole) of pyridinium-1-sulfonate (Note 1), which has been previously chilled to — 20°, is added in one portion. The mixture is stirred for 20 minutes while the temperature is kept below —5° (Note 2). The cooling bath is removed, and the mixture is stirred and warmed gradually to 20° over 20 minutes. The temperature of the dark orange mixture is then raised to 55-60° and after 1 hour is lowered again to —5°. The brown crystals that separate are filtered by suction, pressed into a compact filter cake, and washed with three 100-ml. portions of acetone (Note 3). The yield of this crude product amounts to 46-52 g. after drying on filter paper overnight or at 50° (1 mm.) for 1 hour. (Note 4). 

The pyridinium ion (acid 2) as the analyte can be titrated with quaternary ammonium hydroxide (base 3) as it concerns the determination of H+ of the Brensted acid pyridinium, a potentiometric measurement of the pH titration curve and its inflection point is most obvious. In the aprotic, but protophilic, solvent pyridine no stronger acid can exist (see reactions 4.37 and 4.38) than the pyridinium ion itself hence there is a levelling effect but in theory only on the acid side. 

Benzylic quaternary phosphonium and ammonium salts are dealky-lated by mild heating and/or nucleophilic anions, particularly iodide (9) and thiolate (10), but also hydroxide (11). Most N-benzyl-pyridinium or quaternary aryl ammonium compounds are particularly susceptible (12). Decompositions of this sort have seriously limited the usefulness of solid phase-transfer catalysts derived from (chloromethyl)polystyrene (13, 14). 

Ring D inversion seems to be a crucial step in biogenetic transformations of protoberberines to related alkaloids such as rhoeadine, retroprotoberberine, spirobenzylisoquinoline, and indenobenzazepine alkaloids. 8,14-Cyclober-bin-13-ol 478 derived from berberine (15) was successively treated with ethyl chloroformate, silver nitrate, and pyridinium dichromate (PDC) in dimethyl-formamide to give the keto oxazolidinone 479 (Scheme 98). Heating of 479 with 10% aqueous sodium hydroxide in ethanol effected hydrolysis, retro-aldol reaction, cyclization, and dehydration to provide successfully the... 

Treatment of 1-pyridinium sulphonate with sodium or potassium hydroxide generates sodium or potassium salts of 5-hydroxy-2,4-pentadienal (glutaconaldehyde), which are starting materials for a variety of transformations (equation 178)171b 301. For example, the reaction of the potassium salt with a carbon electrophile has been used for the preparation of a dienol aldehyde (equation 179)mb which was an intermediate in the total synthesis of a mutagen, (S)-3-(dodeca-l,3,5,7,9-pentaenyloxy)propane-l,2-diol. 

SAQ 8.26 The following table contains the rate constant k for the demethylation reaction of /V-methyl pyridinium bromide by aqueous sodium hydroxide as a function of temperature ... 

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