Halogenopyridines reactions with

An efficient method for an aromatic nucleophilic-substitution reaction using a solid-liquid transfer catalysis coupled with MWI was applied to the reaction of halogenopyridine 168 with alkoxides or phenoxides in the presence of 18-crown-6 as... 

Bromopyridine has been aminated by reaction with sodamide or potas-samide in liquid ammonia (see also p. 214) and, in moderate yield, with sodio-methylaniline and related compounds in this connection it is interesting that sodium or potassium salts of arenesulphonamides give 2-arenesulphonyl-aminopyridines with 2-halogenopyridines, whilst sulphanilamide itself gives... 

Many examples are known in which a 2,4- or 2,6-dihalogenopyridine is converted by reaction with ammonia either into a diaminopyridine or into an amino-halogenopyridine, depending on the severity of the conditions used, the presence or absence of a catalyst and the character of other substituents present 52a, i6i , 672, 677a, 680 qualitative results of these studies are... 

Two other modifications of the preparation of 2- and 4-halogenopyridines from amines have been used. 2-Aminopyridines, when treated with sodium ethoxide and amyl nitrite, give diazotates which have been converted by reaction with acids into 2-chloro-, -bromo- and -iodo-pyridinesi 4-Nitraminopyridine, with sodium nitrite in concentrated hydrochloric acid,... 

Arylation of aminopyridines by reaction with halogenobenzenes, usually in the presence of copper, is well known382-4 Tertiary amines can be prepared335. The special case of reaction with halogenopyridines has been mentioned (p. 211), and also the formation of di-(2-pyridyl) amine from 2-aminopyridine and its hydrochloride (p. 210). 

Ciamician reported the formation of 3-halogenopyridines in low yield from the reaction of pyrryl potassium with chloroform, or bromo-form, in ether. Similar reactions of pyrrole with benzal chloride and methylene iodide gave 3-phenylpyridine and traces of pyridine, respectively. These reactions were later reinvestigated by Alexander... 

Whereas only one dehydrobenzene, benzyne, has been detected, two pyridynes are possible. Thus, the scheme we can write ab initio for the action of a nucleophile on the isomeric monosubstituted derivatives of pyridine involving 2,3- (26) and/or 3,4-pyridyne (31) is more complicated than that for the analogous reaction of the corresponding benzene derivative. The validity of this scheme can be checked using data available in the hterature on reactions of halogenopyridines with potassium amide and hthium piperidide involving pyridynes. 

The first amination of a halogenopyridine involving a rearrangement was carried out by Levine and Leake in 1955 in an attempt to prepare 3-phenacylpyridine. When 3-bromopyridine (27, X = Br) was allowed to react with sodium amide in liquid ammonia in the presence of sodio-acetophenone, the reaction mixture obtained consisted chiefly of amorphous nitrogenous material from which only 10% of 4-aminopyridine (34, Y = NH2) and 13.5% of 4-phenacylpyridine were isolated. 

The reactions of various halogenopyridines with lithium piperidide and piperidine have been studied by Kauffmann and Boettcher. ... 

None of the 3-halogenopyridines yield 2-piperidinopyridine. This substance was obtained as the only product from the reaction of 2-fluoropyridine (24, X = F) with lithium piperidide under the same conditions in 97% yield. Finally, it was found that 4-chloropyridine (32, X = Cl) was converted in 95% total yield into a mixture of 0.4% of 3-piperidino- (29, Y = NC5H10) and 99.6% of 4-piperidino-pyridine (34, Y = NCsHio)- Thus, in contrast to the amination with potassium amide, 4-chloropyridine reacts with lithium piperidide almost exclusively via the addition product 33 (X = Cl, Y = NC5H10). 

Those reactions of halogenopyridines with potassium amide and lithium piperidide which proceed via 3,4-pyridyne form the 3- and 4-substituted pyridine derivatives in ratios of 1 2 and 1 1, respectively (see Section II, A, 1). It appears that the ring nitrogen atom has an orienting effect on these additions, but the quantitative divergence of the addition of ammonia and piperidine is not understood at present. 

The other major approach to triazolo[4,3-a]pyridines is from pyridines or from 2-halogenopyridines, with the addition of a three-atom fragment to form the triazole ring. Reaction between pyridine or 4-methylpyridine and... 

Those reactions of halogenopyridines with potassium amide and lithium piperidide which proceed via 3,4-pyridyne form the 3- and... 

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