Nicotinamide 1,6-dihydro

It was shown that dibenzothiophene oxide 17 is inert to 1-benzyl-l,4-dihydro nicotinamide (BNAH) but that, in the presence of catalytic amounts of metalloporphyrin, 17 is reduced quantitatively by BNAH. From experimental results with different catalysts [meso-tetraphenylporphinato iron(III) chloride (TPPFeCl) being the best] and a series of substituted sulfoxides, Oae and coworkers80 suggest an initial SET from BNAH to Fe1 followed by a second SET from the catalyst to the sulfoxide. The results are also consistent with an initial coordination of the substrate to Fem, thus weakening the sulfur-oxygen bond in a way reminiscent of the reduction of sulfoxides with sodium borohydride in the presence of catalytic amounts of cobalt chloride81. 

Cultures of Bacillus sp. oxidized naphthalene to (-r)-fran5-l,2-dihydro-l,2-dihydroxy-naphthalene. In the presence of reduced nicotinamide adeninedinucleotide phosphate (NADPH2) and ferrous ions, a cell extract oxidized naphthalene to fra/ 5-naphthalenediol (Gibson, 1968). Hydroxylation by pure microbial cultures yielded an unidentified phenol, 1- and 2-hydroxynaphthalene (Smith and Rosazza, 1974). 

Two derivatives of nicotinamide (pyridine-3-carboxylic amide), one of the B2 vitamins, nicotinamide adenine dinucleotide (NAD ) and nicotinamide adenine dinucleotide phosphate (NADP ), serve as redox coenzymes. Of the three heterocyclic ring systems found in these coenzymes, i.e. those of purine, ribose and pyridine, it is the pyridine portion that is reactive in redox reactions. Biologically, two oxidation states are important the oxidized form, NAD(P)+, and the 1,4-dihydro isomer of the two-electron reduced form, NAD(P)H (Scheme 1). Nicotinamide coenzymes interconvert between these two oxidation states in... 

The Mg2+ ion also shows an acceleration effect on the photoreduction of dimethylfumarate and some other related olefins by 1-benzyl-1,4-dihydro-nicotinamide (BNAH) used as an NADH model compound via photosensitized electron transfer from BNAH to [Ru(bpy)3]2+ (Scheme 16) [160]. In this case, however, the complex formation of BNAH with Mg2+ results in an increase in the one-electron oxidation potential of BNAH [87]... 

Giindel and Kramer194 transformed the quaternary salt (138) derived from nicotinamide to 3,4-dihydro-2H-pyrido[ 1,2-a]pyrimidine (139). 

The electrochemistry of N-substituted nicotinamides (101) dominates the reports on ring-substituted pyridinium ions. There is also some controversy about the products of reduction. Elving et al. have reviewed this area up to about 1975.158 Apparently there is little doubt that a dihydro product, either 102 or 103, and dimer, either 104 or 105, are formed (Scheme 36). The latest... 

Naphthylacetamide, 32, 94 a-Naphthylcyanamide, 31, 20 -Naphthyl ethyl ether, 32, 97 -Naphthyl methyl ether, 32, 100 Neophyl chloride, 32, 90 Nicotinamide, 30, 3 Nicotinonitrile, 1,2-dihydro-... 

Cyanide ions attack the 4-position in pyridinium salts. For example, nicotinamide pyr-iV-methiodide (143, R = CHS) and di-phosphopyridine nucleotide give the 4-cyano- 1,4-dihydro derivatives (144) 328,329 3-Acetyl-iV-benzylpyridinium chloride similarly gives the 4-cyano-1,4-dihydro derivative and no attack at C-2 has been reported.330 Hydrosulfite reduction of nicotinamide quaternary salts... 

It must, nonetheless, be emphasized that the products of reduction of pyrimidine have not been unequivocally identified, largely due to their instability in the presence of air (oxygen). Furthermore, the UV absorption spectra of the reduction products of waves I and II (kmax284 nm, smax 1.5 x 103) are suggestive of rapid conversion (proton-catalyzed hydration ) of the products, since both the dimer and the dihydro derivative possess a reduced system of aromatic bonds relative to the parent pyrimidine, as a result of which the UV absorption maximum should be shifted to the violet, whereas it is, in fact, shifted 44 nm to the red (from 240 nm to 284 nm) for both products. Of possible relevance to this is the fact that the reduced rings of 4-aminopyrimidine 102) and nicotinamide 103) undergo acidic hydration to form products absorbing at 280 to 290 nm. 

Hantzsch ester or 1-benzyl-1,4-dihydro nicotinamide, A, 20 h in MeCN hydrolysis... 

Finally, mention must be made of the nicotinamide nucleosides. Fischer and Raske observed the quaternization of tetra-O-acetyl-a-D-glucopyranosyl bromide with pyridine, and Karrer and coworkers extended this reaction to the synthesis of quaternary, nicotinamide nucleosides. The condensation has been improved by Haynes and Todd, who used acetonitrile as solvent. With tri-O-acetyl-a-D-ribofuranosyl bromide, D-ribofuranosylnicotinamide—a structural unit of coenzyme I (DPN)—was obtained, and this was reduced with sodium dithionite to the dihydro derivative. 

Sodium cyanoborohydride (10) produces mainly 1,4-dihydropyridines (11) in the reduction of 3,5-di-cyano- and 3,5-diethoxycarbonyl-pyridines, diborane produces more of the 1,2-isomer. With NBH, mixtures of 1,2- and 1,4-dihydro adducts are produced, the latter predominating when carried out in pyridine solution. Nicotinamide (13) in ethanol can be reduced to (8) in moderate yield at 140 C in diglyme the tetrahydropyridine (8) was isolated in admixture with the piperidine (14), presumably via dehydration of the amide. 3-Nitropyridine affords 3-nitropiperidine in moderate yield when reduced in ethanol. The carboxylic acid and halo derivatives of pyridine are generally not reactive toward NBH. 

A novel electron transfer free radical mechanism has been elucidated for sodium naphthalenide induced demercuration. A new reductant for the cleavage of the C—Hg bond, A -benzyl-1,4-dihydro-nicotinamide (BNAH), has also been proposed it reduces alkylmercury(II) acetates via an electron transfer chain substitution mechanism. ... 

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