Benzyl pyridinium chloride

Lithium cyclopentadienylide with benzyl pyridinium chloride gives i the pyridone methide (85) (see below and p. 328). 

In the aldohexose series, 5-(benzylamino)-l,2-0-cyclohexylidene-5-deoxy-L-idurononitrile gives, on acid hydrolysis, an almost quantitative yield of N-benzyl-2-cyano-5-hydroxypyridinium chloride. On partial, catalytic hydrogenation of this aminonitrile, 5-(benzylamino)-I,2-0-cyclohexylidene-5-deoxy-L- do-hexodialdo-l,4-furanose is obtained. This compound is reducible with sodium borohydride to crystalline 5-(benzylamino)-l,2-0-cyclohexylidene-5-deoxy-L-idofur-anose which, on removal of the cyclohexylidene group with acid, forms the intermediate 5-(benzylamino)-5-deoxy-L-idopyranose this then loses three molecules of water per molecule, to give N-benzyl-5-hydroxy-2-(hydroxymethyl)pyridinium chloride. It is therefore clear that the transformation of 5-aminoaldoses into pyridine derivatives in acid solution is not prevented by the monoalkylation of the amino group. 

CMCs of these polyfluorinated surfactants are of the order of 10 5 m.47 Plots of the observed H chemical shifts versus surfactant concentration of cetyl trimethyl ammonium chloride, cetyl pyridinium chloride, cetyl dimethyl phenyl ammonium chloride, cetyl dimethyl benzyl ammonium chloride, cetyl dimethy 1-2-phenyl ethyl ammonium chloride, and cetyl dimethyl-3-phenyl propyl ammonium chloride, are sigmoidal and were fitted to a model based on the mass action. The H chemical shift-based CMC values are in excellent agreement with those determined by the surface tension method.48 The micellization processes of dodecyl trimethyl ammonium halides (chloride and bromide) studied by calorimetric titration show different behaviors at 298 K. However, these disappear at 313 K, while the results measured by the chemical shift versus surfactant concentration do not show this difference.49 The CMC of 3-aminopropyl triethoxy silane in toluene is ca. 0.47m, measured by H and l3C chemical shifts.50 The CMC of optically active potassium A -n-dodecanoyl alaminate measured by H and l3C chemical shifts is lower (11-15 him) in D20 than that in a mixed solvent of 1,4-dioxane and D20 (19mM).-51 The H chemical shift shows that the CMC of resorcinol-type calix[4] phosphoric esters having four alkyl side-chains, [4]Ar 5P-R-n, is insensitive to the length of the side-chains, n.52 The CMC values of a family of surfactants, the sodium cyclohexyl alkanoates, with different lengths of the alkanoate side-chains, were obtained from 13C chemical-shift measurements. The results show that these amphiphiles have high CMCs (0.12-1.02 m).-53... 

If instead of benzyl alcohols the corresponding quaternary salts were used, namely 1-benzyl and l-(4-chlorobenzyl)pyridinium chlorides, the reaction with diamine and sulphur resulted in poor yields of IPs (35%). Unlike the above compounds, N, A-dimethylbenzylamine did not react with o-DAP and sulphur. However, the reaction can take place intramolecularly when the N-benzyl group is a structural fragment of the diamine molecule. When both 3-amino-4-benzylaminopyridine 31... 

Benzyl dimethyl alkyl ammonium cUaide, dialkyl dimethyl ammonium chloride lauryl pyridinium chloride, cetyl pyridinium chloride, benzalkonium chloride Polyhexamethylene biguanide... 

There are three potential options for the mechanism of Grob fragmentation reactions, one concerted and two stepwise. The stepwise reactions, which result from initial loss of either the nucleofuge or electrofuge, are less useful in synthesis since they often promote side reactions. However, one highly efficient stepwise transformation was reported by Kato. Treatment of diol 6 with pyridinium chloride results in formation of benzyl carbocation 8. Cleavage of this alcohol yields monocycle 9 and, ultimately, the ketone product 10. ... 

Trimethylsilyl iodide 17, which can be generated in situ by reaction of trimethyl-silyl chloride (TCS) 14 with Nal in acetonitrile [1], converts alcohols 11, in high yields at room temperature, into their iodides 773a, HI, and hexamethyldisiloxane (HMDSO) 7 [1-8, 12]. Likewise esters such as benzyl benzoate are cleaved by Me3SiCl 14/NaI in acetonitrile under reflux [Ij. Reactions of alcohols 11 with trimethylsilyl bromide 16 in chloroform or, for in situ synthesis of 16 from liBr and TCS 14 in acetonitrile and with HMDS 2 and pyridinium bromide perbromide, proceed only on heating in acetonitrile or chloroform to give the bromides 773 b in nearly quantitative yield [3, 8, 12] (Scheme 6.1). 

An intriguing use of a quaternary ammonium salt in a two-phase reaction is to be found with the regeneration of 1 -benzyl-1,4-dihydronicotinamide by sodium dithionite in a biomimetic reduction of thiones to thiols [12], The use of sodium dithionite in the presence of sodium carbonate for the 1,4-reduction of the pyri-dinium salts to 1,4-dihydropyridines is well established but, as both the dithionite and the pyridinium salts are soluble in water and the dihydropyridine and the thione are insoluble in the aqueous phase and totally soluble in the organic phase, it is difficult to identify the role of the quaternary ammonium salt in the reduction cycle. It is clear, however, that in the presence of benzyltriethylammonium chloride, the pyridine system is involved in as many as ten reduction cycles during the complete conversion of the thione into the thiol. In the absence of the catalyst, the thione is recovered quantitatively from the reaction mixture. As yet, the procedure does not appear to have any synthetic utility. 

The remaining three steps are accomplished without purification of the intermediate products. The secondary hydroxy group is protected by acetylation and the benzyl ether is removed by hydrogenolysis to provide a primary alcohol. The alcohol is oxidized to a carboxylic acid by ruthenium(III) chloride or pyridinium dichromate. This method has been applied to the synthesis of various enzyme inhibitors containing the 1-hydroxyethylene isostere. 

A compound prepared and first described as nicotinium dichromate (NDC) by Palomo et al.,379 was later shown by X-ray-crystal analysis380 to be a betainic mixed anhydride of nicotinic and chromic acid (NACAA). Because of its unique structure, it deserves a close scrutiny of its oxidative properties.381 Replacement of the chloride anion in the quaternary ammonium resin, Dowex 1-X8, for the dichromate anion, leads to a polymer supported dichromate, which is able to make selective benzylic oxidations.382 Finally, poly[vinyl(pyridinium dichromate)] (PVPDC), a polymeric analogue of PDC, must be mentioned whose use in the oxidation of alcohols allows for a very easy work-up.383... 

C-(w-propyl)-N-phenylnitrone to N-phenylmaleimide, 46, 96 semicarbazide hydrochloride to ami-noacetone hydrochloride, 45,1 tetraphenylcyclopentadienone to diphenyl acetylene, 46, 44 Alcohols, synthesis of equatorial, 47, 19 Aldehydes, aromatic, synthesis of, 47,1 /8-chloro-og3-unsaturated, from ketones and dimethylformamide-phosphorus oxychloride, 46, 20 from alkyl halides, 47, 97 from oxidation of alcohols with dimethyl sulfoxide, dicyclohexyl carbodiimide, and pyridinium trifluoroacetate, 47, 27 Alkylation, of 2-carbomethoxycyclo-pentanone with benzyl chloride, 45, 7... 

Ac, acetyl AIBN, azobis(isobutanonitrile) All, allyl AR, aryl Bn, benzyl f-BOC, ferf-butoxycarbonyl Bu, Butyl Bz, benzoyl CAN, ceric ammonium nitrate Cbz, benzyloxycarbonyl m-CPBA, m-chloroperoxybenzoic acid DAST, diethylaminosulfur trifluoride DBU, l,8-diazabicyclo[5.4.0]undec-7-ene DCC, /V. /V - d i eye I oh e x y I c ar bo -diimide DCM, dichloromethyl DCMME, dichloromethyl methyl ether DDQ, 2,3-dichloro-5,6-dicyano-l,4-benzoquinone DEAD, diethyl azodicarboxylate l-(+)-DET, L-(+)-diethyl tartrate l-DIPT, L-diisopropyl tartrate d-DIPT, D-diisopropyl tartrate DMAP, 4-dimethylaminopyridine DME, 1,2-dimethoxyethane DMF, /V./V-dimethylformamide DMP, 2,2-dimethoxypropane Et, ethyl Im, imidazole KHMDS, potassium hexamethyldisilazane Me, methyl Me2SO, dimethyl sulfoxide MOM, methoxymethyl MOMC1, methoxymethyl chloride Ms, methylsulfonyl MS, molecular sieves NBS, N-bromosuccinimide NIS, /V-iodosuccinimide NMO, /V-methylmorpho-line N-oxide PCC, pyridinium chlorochromate Ph, phenyl PMB, / -methoxvbenzyl PPTs, pyridiniump-toluenesulfonate i-Pr, isopropyl Py, pyridine rt, room temperature TBAF, tetrabutylammonium fluoride TBS, ferf-butyl dimethylsilyl TBDMSC1, f-butylchlorodimethylsilane Tf, trifhioromethylsulfonyl Tf20, trifluoromethylsulfonic anhydride TFA, trifluoroacetic acid THF, tetrahydrofuran TMS, trimethylsilyl TPAP, tetra-n-propylammonium perruthenate / -TsOH. / -toluenesulfonic acid... 

Carboxylation of the potassium salt of 3-hydroxy-6-methylpyridine (145) gave the picolinic acid 146(84MI16). The Hammick condensation reaction of picolinic acid with benzaldehyde has been studied with regard to the effect of solvent, temperature, and molar ratio of reactants (85MI5). Benzoyl chloride, or benzaldehyde, and l-benzyl-4,6-diphenylpyridinium-2-carboxylate afford 2-benzoyl-4,6-diphenylpyridine (85JCS(P1)2167). Sulfur and 1,4,6-triaryl-pyridinium-2-carboxylates 147 in xylene at 140°C give the corresponding pyridine-2-thiones 148(838149). 

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