Pyridyl pyridine 1-oxides

Pyridinol A -oxide, hi83 Pyridinols, hi79 thru hi81 2(l//)-Pyridone, hl79 2-(2-Pyridyl)pyridine, d790... 

A number of syntheses of substituted 2,3 -bipyridines are worthy of note. Tetracyclone heated at 215°C with nicotinonitrile affords 3,4,5,6-tetraphenyl-2,3 -bipyridine, whereas 3,4-di(2-pyridyl)pyridine is obtained by an oxidative degradation of the corresponding 6,7-disubstituted thiazolo[3,2-a]-pyridinium salt. Nicotinic acid on UV irradiation in aqueous solution at pH 4-6 gives 2,3 -bipyridine-5-carboxylic acid, whereas irradiation of picolinic acid in the same pH range in the absence of metal ions gives some 2,3 -bipyridine. 6,6 -Diphenyl-2,3 -bipyridine is thought to be formed from... 

The reaction depicted also proceeds between pyridine oxide in its neutral form and the double amount of benzophenone metal-ketyl. Pyridine bases (not N-oxides) do not react with the ketyls. The N-oxides of pyridine and y-picoline give both the N-oxide of the pyridyl carbinol and the pyridyl carbinol without the N-oxide oxygen. Yields can be 70 and 80%, respectively (depending on the metal nature in the metal-ketyl). Having pronounced physiological activity, these compounds are the key materials in syntheses of atropine-like drugs. 

The alkaline hydrolysis of phosphonium salts gives phosphine oxides and hydrocarbons resulting from the most stable carbanions in each case. O Benzyl tris(2-pyridyl)phosphonium bromide (17) undergoes rapid alkaline hydrolysis at room temperature to give good yields of benzylbis(2-pyridyl) phosphine oxide and pyridine. ... 

Generally similar to these reactions is that which occurs between pyridine oxides and pyridine in the presence of j -toluenesulphonyl chloride. Thus, 2-and 4-chloropyridine 1-oxide give 2-chloro-4- and 4-chloro-2-pyridyl-... 

Pyridine, 2,6-di(2-pyridyl)thiomethyl-synthesis, 2, 435 Pyridine, 2-ethoxy-iV-oxide... 

While pyridine and quinoline N-oxides do not react directly with enamines, they have been found to form a-pyridyl and 2-quinolinyl-2 -cyclohexanones in good yields after prior acylation (371,372). 

In the other extreme, ethyl 3-oxohexanoate 75 required fusion with 3-pyridyl-hydrazide 73a or 3-hydrazinocarbonyl-pyridine-l-oxide 73b at 120°C in order to give the corresponding pyrazol-3-ones 76a,b (92AF1350) (Scheme 22). Depending on the reaction conditions, the reaction of ethyl 3-oxo-3-phenylpropanoate 77 and cyanomethylhydrazide 78 gave different products. Thus, fusion at 140°C gave pyrazol-3-one 79 and N,A -bis(cyanoacetyl)hydrazine 80, while heating in ethanol... 

Cyclization of 3-cyano-2-[(3-hydroxypropyl)amino]-5-(4-pyridyl)pyri-dine-l -oxide (298) in POCI3 yielded 9-cyano-7-(4-pyridyl)-3,4-dihydro-2/f-pyrido[],2-n]-pyrimidine I -oxide (299) (94EJM175). After heating 3-cyano-4-trifluoromethyl-6-phenyl-2-[(3-hydroxypropyl- and 3-hydroxybutyl)-amino] pyridines in boiling POCI3 for 1 h, the product was treated with aqueous NH4OH to yield 6-phenyl-8-trifluoromethyl-9-cyano-3,4-dihydro-2//-pyr-ido-[l,2-n]pyrimidine and its 4-methyl derivative (01CHE329). 

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