Benzylpyridines

According to U.S. Patent 2,676,964 to 1.0 mol of potassium amide in 3 liters of liquid ammonia, is added 1.0 mol of 2-benzylpyridine. After 15 minutes, 1.1 mols of 3reaction product decomposed with water and ether extracted. The ether layer is dried over Sodium sulfate and after evaporation the residue is distilled, giving the 3-phenyl-3-(2-pyridyl)-N,N-dimethylpropylamine, BP 139°-142°C/1-2 mm. The maleate is produced by reaction with maleic acid. 

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). 

Au( N) CI3 adducts are readily obtained by reaction of AU2CI6 or [ AuCU] with a variety of substituted heterocyclic ligands including 2-phenylpyridine [9], 2-benzylpyridines [10],... 

Scheme 2.1 Production of cyclometallated derivatives [Au(N,C)Cl2] from 2-benzylpyridines by refluxing in MeCN/H20.

Bnpy-H) = cyclometalated 2-benzylpyridine, saccH = saccharine. (6-Bnbipy-H) = cyclometalated 6-(l,l-dimethylbenzyl)-2,2 -bipyridine. 

Fuchita, Y, leda, H Tsunemune, Y, Rinoshita-Nagaoka, J. and Rawano, H. (1998) Synthesis, structure and reactivity of a new six-membered cycloaurated complex of 2-benzoylpyridine [AuCl2(pcp-C, N)] [pep = 2-(2-pyridylcarbonyl) phenyl]. Comparison with the qfcloaurated complex derived from 2-benzylpyridine. Journal of the Chemical Society, Dalton Transactions, (5), 791. 

Interestingly, the Fischer indole synthesis does not easily proceed from acetaldehyde to afford indole. Usually, indole-2-carboxylic acid is prepared from phenylhydrazine with a pyruvate ester followed by hydrolysis. Traditional methods for decarboxylation of indole-2-carboxylic acid to form indole are not environmentally benign. They include pyrolysis or heating with copper-bronze powder, copper(I) chloride, copper chromite, copper acetate or copper(II) oxide, in for example, heat-transfer oils, glycerol, quinoline or 2-benzylpyridine. Decomposition of the product during lengthy thermolysis or purification affects the yields. 

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%). 

Cyclopalladated complexes provide a potential use for regiospecifically controlled organic syntheses.1 Various substituents can be introduced onto the palladated carbon position by reactions of cyclopalladated complexes with various reagents.2-4 Cyclopalladation of aryl-substituted nitrogen or phosphorus bases has been performed mainly by use of [PdCl4]2- or PdCl2(NCPh)2 in the presence or absence of an acetate salt, but this method appears to have limit in applicability.5,6 Here, we describe a preparation of a rare six-membered cyclopalladated complex of 2-benzylpyridine by use of palladium(II) acetate,7 which seems to be a better starting material for syntheses of cyclopalladated species.6,7 Only five reports of six-membered cyclopalladated complexes have appeared.7,8... 

Caution. The procedure should be carried out in a well-ventilated hood owing to the toxic nature of 2-benzylpyridine. 

Palladium(II) acetate was purchased from Nippon Engelhard, and used without further purification. 2-Benzylpyridine (0.46 g, 2.72 mmol) is added to a solution of palladium(II) acetate (0.60 g, 2.67 mmol) in acetic acid (50 mL). This solution is stirred at 25 °C for 24 h affording a pale yellow precipitate. This precipitate is collected on a medium-porosity fritted glass filter and washed with water, methanol, and diethyl ether. Yield 0.80 g (89%), mp 268 °C (dec under air in a capillary tube). 

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