Pyridine 2-benzylpyridine

Relatively few pyridines with substituents other than alkyl groups have so far been examined, and with some of these the reaction has been carried out only in the presence of added solvent. A comparison of the reactivities of these pyridines is therefore difficult. It has, however, been established that the presence of benzoyl groups in the 3- and 4-positions causes a very marked drop in the yields of the corresponding 2,2 -bipyridines. The 3- and 4-benzylpyridines were found to be more reactive but even in the absence of solvent, and in vacuo, 4-benzylpyridine gave only about one-third of the yield of the 2,2 -bipyridine compared with pyridine itself. Ethyl nicotinate in the absence of solvent and under vacuum -- gave a similar yield of biaryl but 4-phenylpyridine was found to be less reactive. 

Because allyltrimethylsilane 82 or benzyltrimethylsilane 83 can be regarded as combinations of the hard trimethylsilyl cation and the soff allyl or benzyl anions, pyridine N-oxide 860 reacts with excess 82 or 83 in the presence of catalytic amounts of tetrabutylammonium fluoride di- or trihydrate in THF to give 2-allyl-or 2-benzylpyridines 948 and 950 [60]. The general reaction of silicon reagents such as 82 and 83 or of trimethylsilyl cyanide 18 with fluoride to generate allyl or... 

Reaction of pyridine N-oxide 860 with excess allyltrimethylsilane 82 affords, via 947, 2-propenylpyridine 948 in 53% yield as the only reaction product which can be isolated. Ehmination of trimethylsilanol 4 from 947 is apparently followed by fluoride-catalyzed isomerization of 2-allylpyridine into 2-propenylpyridine 948. 3-Methylpyridine-N-oxide 867 a is converted into 2-propenyl-3-methylpyridine in 69% yield. Likewise, fluoride-catalyzed addition of excess benzyltrimethylsilane 83 to 860 furnishes, via 949, 2-benzylpyridine 950 in 70% yield. The generated leaving group trimethylsilanol 4 reacts with excess allyltrimethylsilane 82 or benzyltrimethylsilane 83 in the presence of fluoride to give hexamethyldisiloxane (HMDSO) 7 and propylene or toluene, respectively [60] (Scheme 7.16). 

Analogous to its reaction with carbonyl compounds (see 6.3.4), benzyltrimethyl-silane undergoes a fluoride-induced nucleophilic substitution reaction on pyridine-1-oxides and quinoline-l-oxide to form 2-benzylpyridines (>70%) and 2-benzyl-quinoline (65%), respectively [57], Allyltrimethylsilane reacts with pyridine-l-oxide to produce 2-propenylpyridine (56%). 

The results of some of the many aminations of pyridine and its derivatives that have been carried out appear in Table 14. Yields are quoted where possible but these should not be used for quantitative comparisons as reaction and work up conditions vary widely. 2-Alkylpyridines aminate at the vacant a-position, except when the substituent is very large. 2-f-Butylpyridine does not undergo the Chichibabin reaction, probably because the bulky 2-f-butyl group prevents adsorption on to the sodamide surface. In contrast, 2-phenylpyridine undergoes amination in very good yield. Aminations of 2- and 4-methyl-pyridines do not involve attack on the anhydrobases in aprotic solvents, but some ionization does take place in liquid ammonia. 4-Benzylpyridine forms a carbanion (148) which is only aminated with difficulty by a second mole of sodamide (equation 103). 

The intermediacy of an anhydro base (57) was referred to in Scheme 46. Analogous anhydro bases (pyridone methides) can be formed by deprotonation of quaternary salts of 2- and 4-benzylpyridines and the like. The pyridone methides are usually highly reactive and not readily isolable some stable examples are shown in Scheme 49. Pyridine methides are intermediates in the base-catalyzed alkylation and acylation reactions of pyridinium salts at the exocyclic carbon. Compounds of type (60) have been estimated to have 25-30% dipolar character. Protonation of (60) occurs at the 2 - and 3 -positions in the ratio 4 1 respectively (70JCS(C)800). 

Benzylpyridine (called 2-, 3- or 4-Benzyl-pyridin in Get), CJ2HnN mw 169.22, N 8.28%. This compd exists in 3 isomeric forms ... 

Hydrogenation of 2- and 4-phenyl- or -benzylpyridines usually occurs preferentially in the pyridine ring.18,27,29 In trifluoroacetic acid over platinum oxide, however, 4-phenyl- and 4-(3-phenylpropyl)pyridines gave the products hydrogenated in the benzene ring in 87 and 96% yields, respectively. The hydrogenation of 2-phenylpyridine... 

Several closely related arylgold(III) complexes have also been formed in the course of cyclometalation processes. The reaction of substituted pyridine ligands such as 2-phenylpyridine or 2-benzylpyridines (denoted HL) with [AuCL ]- at ambient temperature... 

In an analogous reaction, 2-benzylpyridine was prepared from reaction of pyridine N-oxide and benzyltrimethylsilane in the presence of tetrabutylammonium fluoride. Substituent effects on... 

Pyridine derivatives are important as pharmaceuticals. Nicotinic acid derivatives are used as vasodilators, anticoagulants and hypolipidaemic agents. Derivatives of isonicotinic acid (pyridine-4-carboxylic acid) such as isoniazide 215 and ethionamide 216 are used as tuberculostatics, and of 2-benzylpyridine in the form of pheniramine 217 as antihistamine. 

Pyridine has long been used as a solvent in the production of rubber chemicals, textile water-repellant agents, and in the synthesis of drugs. The derivatives 2-benzylpyridine and 2-aminopyridine are used in the preparation of antihistamines. Another market for pyridine is in the manufacture of the nonpersistent herbicides diquat and paraquat. 

Pyridine 1°. See Pyridine Pyridine, 2-benzoyl-. See 2-Benzoylpyridine Pyridine, 2-benzyl-. See 2-Benzylpyridine Pyridine-3-carbinol. See Pyridine-3-methanol Pyridine-3-carbonic acid. See Nicotinic acid 4-Pyridinecarboxaldehyde, 3-hydroxy-2-methyl-5-[(phosphonooxy) methyl]-. See Pyridoxal 5-phosphate... 

Structures of cytochrome P450 2B6 bound to 4-benzylpyridine and 4-(4-nitrobenzyl)pyridine insight into inhibitor binding and rearrangement of active siteside chains. Mol Pharmacol 80 1047-1055... 

When 2-benzylpyridine, paraformaldehyde, and dimethylamine hydrochloride are heated in water for 24 hours, 2-(2-dimethylaminoethyl-I-phenyl)pyridine dihydrochloride (IX-248) results. ... 

In a series of papers, Ford and co-workers described the photophysical and photochemical properties of these luminescent clusters in detail [46-58]. In addition to complexes 4a and 4b, time-resolved emission spectra of the tetranu-clear copper(I) iodide clusters [Qi4l4(L)4] with a series of substituted pyridines [L = 4-tert-butylpyridine (4c), 4-benzylpyridine (4d), pyridine-dj (4e), 4-phe-nylpyridine (4f), 3-chloropyridine (4g), piperidine (4h), P"Bu3 (4i)] have also been studied [49]. The photophysical data are summarized in Table 1. In general, in toluene solution at 294 K, the complexes revealed a low-energy emission at 678-698 nm and a weaker, higher energy emission at 473-537 nm. The emission spectrum of 4a in toluene at 294 K is shown in Fig. 2... 

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