Reduction pyridine

Voltammetry studies on pyridine and pyridine derivatives have delineated some of the initial mechanistic steps of reduction.9-11 The half-wave potential was found to correlate with the n,n triplet energy.10 The mechanism of pyridine reduction in liquid ammonia was studied by Talcott among others this process was also studied on a synthetic scale.9,12 Evidence for an ECE... 

The possible mechanistic pathways can be shown using horizontal changes for electron transfer and vertical ones for proton transfer (Scheme 1). This scheme has been generalized and truncated to show only the reduction of A to AH2. Pyridine reduction would be extended from this scheme to reflect the six electrons and six protons involved. Of course, protonated monocationic species would probably be important only in acidic electrolytes, whereas dianions would normally be formed only in aprotic electrolytes at high junction potentials. The dication, AH22+ is an unlikely species when A is pyridine. 

The production of bipyridyls (1) and bipiperidyls (2) was observed on reduction of pyridine. Schering AG has a patent on a process for producing 4,4 -dipyridyls at the cathode of a divided or undivided cell using liquid ammonia as the solvent.26 The same bipyridyl was also formed during electrolysis of bromobenzene in pyridine solvent, using Mg electrodes.27 Bipiperidyls (2) were observed as products of pyridine reduction as early as... 

Dyes containing the pyridinium group linked to the diazo component via a carboxylic ester function (e.g., 40) [32017-47-3] are obtained by condensation of 4-nitrobenzoyl chloride with chloroethanol, reaction of the ester with pyridine, reduction of the nitro to an amino group, diazotization, and coupling with aromatic amines [124],... 

Explain the difference between these two pyridine reductions. 

In general this organocatalytic pyridine reduction procedure provides azadecalinones 19a-f as well as the tetrahydropyridines 19g-j in good isolated yields and with excellent enantioselectivities (up to 92% ee) (Rueping and Antonchick 2007). 

N- )onor and Mixed N- and O-Donor Ligands. The i.r. spectra of the adducts VOCI2-OMe,L (L = MeCN, 2,6-lutidine, a-pic, or 2,6-dimethylpyrazine) and VOCl20Me,2L (L = py or 2,6-dimethylpyrazine) could not be obtained because of the low thermal stability. With an excess of pyridine, reduction to VOCl2,py occurred. This type of reaction is common among the halides and their derivatives of the early transition metals. It prevented the isolation of pure products from reactions between VOCI3 or... 

Buta-l,2,3-trienes. Newkome et al. were able to prepare the unstable (Z)-and (E)-l,4-diphenyl-l,4-di(2-pyridyl)butatrienes, (2) and (3), by didehydrox-ylation of (1) with P214 in anhydrous pyridine. Reduction of (1) with the more usual reagents (SnCl2 or PBra) resulted mainly in formation of (4). 

In imidazo[l,2-a]pyridines, reduction of the six-membered ring occurred fairly readily and has been reported, when using palladium on charcoal as the catalyst, to be competitive with reduction of a nitro group or with debenzylation <89CPB2293, 86JCR(S)404>. A similar facile reduction has been reported for imidazo[l,5-a]pyridines <91JMC725>. 

The PTAD-diene protected 22-aldehyde analog has been used by Williams and Eyley to synthesize 24,25-dihydroxy derivatives via an aldol reaction with the tetra-hydropytanyl ether of 3-hydroxy-3-methyl-2-butanone followed by NaBH4/pyridine reduction [scheme (9)] The same starting aldehyde is also a precursor for synthesis of the 25,26-dihydroxy-5,7-diene [scheme (10)] ... 

The same method was also used for the synthesis of the anti-malarial compound mefloquine. Heterocyclization of 2-trifluoromethylaniline with trifluoroacetic acid ethyl ester provides 2,8-6w-(trifluoromethyl)-4-hydroxyquinoline. Bromination with phosphorous tribromide, followed a carbon monoxide introduction, affords 2,7-trifluoromethyl-4-carboxylic acid quinoline. Amide formation and pyridine reduction completes the synthesis providing mefloquine in high yields. ... 

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