O-Dinitriles

The preparation of pyridine compounds from a,o>-dinitrile systems has been studied by several workers. Johnson et al.101 found that 3-hydroxyglutaronitriles (128) or glutacononitriles (129) react readily with anhydrous hydrogen bromide or iodide to yield the 2-amino-6-halopyridines (130) as their salts, although in no case does hydrogen chloride cause cyclization to the expected 2-amino-6-chloropyridine. 

Intramolecular cycloaddition does not occur with a,(o-dinitriles each cyano group instead undergoes independent cocycloaddition with two molecules of alkyne to afford high yields of di(2-pyridyl)alkanes. The reaction may also be controlled to give high yields of 2-((o-cyanoalkyl)pyridines. ... 

An interesting cationic reaction takes place if a-(o-dinitriles are treated with anhydrous halogen acids. Howard as well as Osborn and Johnson et al. studied the reaction of HBr with succinonitrile, glutaronitrile and phthalonitrile, and obtained cyclic products of the general formula... 

Cyclization of a,o)-dinitriles under acidic conditions has been reviewed thoroughly by Johnson and Madronero. Anhydrous hydrogen halides are favored for such reactions and a wide range of five-, six-and seven-numbered heterocyclic systems are produced. 

Using the different methods, it was possible to design an excellent catalyst for a bulk product such as caprolactam. The first advantage of the biocatalysis in this route is able to carry out this reaction at neutral pH. The second is to selectively obtain the a,co-cyanoacid starting from the a,(o-dinitrile. No other type of catalysis can do this. 

Goerdeler s general synthesis3 of 5-amino-1,2,4-thiadiazoles by the cyclization of N-thiocyanatoamidino compounds formed in situ has been further exploited.114-116 l-Amino-3-iminoisoindoleninium thiocyanates (144), which are accessible from o-dinitriles, can function as the amidine, and yield, by the usual simultaneous action of bromine and sodium methoxide,117 or of sodium hypobromite,118 3-substituted 5-amino-l,2,4-thiadiazoles (145). 

Thorpe reaction org chem The reaction by which, in presence of lithium amides, a,(o-dinitriles undergo base-catalyzed condensation to cyclic iminonitriles, which can be hydrolyzed and decarboxylated to cyclic ketones. thorp re,ak-shan) TMPC See tetrakls(hydroxymethyl)phosphonium chloride, thuiia See thulium oxide. thir-le-a)... 

Aliphatic dinitriles which have more than one methylene group between their functional groups, and ar. dinitriles, except o-dinitriles, give good yields of cyanocarboxylic acid amides when treated with strongly basic anion exchange resins. F. e. s. G. Berther, B. 92, 2616 (1959) carboxylic acid amides from nitriies s. a. J. M. Bobbitt and D. A. Scola, J. Org. Ghem. 25, 560 (1960). 

Type B Syntheses [NCN + CS].—l-Amino-3-imino-isoindoleninium thiocyanates (60), which are accessible from o-dinitriles (59), are convertible into 3-substituted 5-amino-1,2,4-thiadiazoles (61) by the simultaneous action of bromine and sodium methoxide. The reactants (60) thus play the role of the linear amidines in Goerdeler s synthesis, of which the present modification is a useful extension/ ... 

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