Isomerization cyanopyridines

Nicotinamide (118) forms the 1,6-dihydropyridine (119) and the 6,6 -dimer (120) upon polarography in aqueous solution. The 4-isomer (121 Scheme 24) generates the aldehyde (122) when reduced in 0.8 M hydrochloric acid and the alcohol (123) in an alcoholic citric acid buffer solution. The thioamides produce the 4-aminomethyl- or 4-cyano-pyridines under related conditions. The isomeric cyanopyridines... 

Among these methods, Thorpe isomerization of substituted 2-alkylthio-3-cyanopyridines is of considerable interest. The advantages of this approach are that the starting 3-cyanopyridine-2(l //)-thiones (7) are readily accessible, diverse 3-cyanopyridine-2(l //)-thiones can be used, one-pot procedures can be employed, and the final products are prepared in high yields. The mechanism of this transformation can be represented by the Scheme (1985MI1, 1989MI2) ... 

Photolysis of six-coordinate [Fe(CN)s en]3 results in the loss of one cyanide to give287 the chelated complex [Fe(CN)4en]2 in high quantum yield. With ligands such as the cyanopyridines that have two donor sites [Fe(CN)5L]" complexes have been observed to exhibit coordination isomerization. Several such compounds have been studied288,289 and interestingly some of the isomerizations involve an intramolecular mechanism. 

The fusion of alkali arylsulfonates with potassium cyanide forms aromatic nitriles by a replacement of the sulfo group. For the most part, the yields are low, although the reaction has been applied successfully in the preparation of naphthonitriles and cyanopyridines. Sometimes potassium ferrocyanide is substituted for the alkali cyanide with better results. Ten isomeric cyanonaphthalenesulfonates have been converted to the dinitriles by fusion with this reagent in yields ranging from 8% to 75%. Migration of the cyano group from the beta to the alpha position has been observed in the formation of these Compounds. ... 

The mass spectra of cyanopyridines which were isotopically labeled showed that they isomerize to one another, probably through Dewar intermediates (Scheme 39).98... 

Write structures for the isomeric compounds C7H6N2O (formed in a ratio of 4 3) when 3-cyanopyridine methiodide is reacted with alkaline potassium ferricyanide. 

Chromium(ii) reduction of the three isomeric nitrile-bonded cyanopyridine complexes proceeds with efficient transfer of the ligand from chromium to cobalt. The protonated forms of the complexes are relatively unreactive. Reduction of the 2-isomer leads to the unexpected product (16), consistent with the sequence of reactions (61). The other two isomers lead to the complexes [Cr(H20)s(NC5H4CN)] +,... 

Several derivatives of racemic amino-sugars have been synthesized from heterocyclic precursors. Thus, the four isomeric methyl 3-amino-3,4-dideoxy-DL-pentopyranosides have been derived from dihydro-(4 )-pyran, as indicated in Scheme 29, furfural has been converted into derivatives of 6-acetamido-6-deoxy-DL-mannopyranose, ° and 3-cyanopyridine has been transformed into the racemic nojirimycin (5-amino-5-deoxy-DL-glucopyranose) derivative (122) by the sequence of reactions outlined in Scheme 30. ... 

Such ligands as the cyanopyridines can coordinate at two different positions to the iron of the [Fe(CN)5] moiety. The kinetics of isomerization (14) (15) (and the analogues 3-cyanopyridine reaction) were studied... 

In addition, some kinetic studies on the oxidative ammonolysis of 2-picoline using V-Sn/TiOj catalysts were reported [34]. The majority of work on this particular reaction was carried out by Russian researchers and in particular Suvorov s group [35]. It is also noteworthy that most of their results were published in Russian journals [e.g., 36]. Moreover, VPO catalysts (e.g., a-VOPO phase) were also applied by our group for the ammoxidation of three isomeric picolines to their corresponding cyanopyridines [3]. 

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