Oxidative Amino-Dehydrogenations

In Section II the oxidative amino-dehydrogenation of monoazines, quinolines, naphthyridines, diazines, quinazolines, quinoxalines, triazines, tetrazines, and their bicyclic analogs is extensively discussed. Section III deals with the oxidative imino-dehydrogenation of quaternised azinium salts and Section IV with NMR data of the covalent a-adducts and their kinetic and thermodynamic stabilities. 

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Site specificity was found to be considerably higher in oxidative amino-dehydrogenation reactions with derivatives of 3-nitropyridine. 2-R-3-nitropyridine (R = C1, OMe) when treated with liquid ammonia and permanganate gives a reasonable yield of 6-amino-2-R-3-nitropyridine (R = C1, OMe) 6-R-3-nitropyridine yields 2-amino-6-R-3-nitropyridine (R = C1, OMe) (Scheme 4) (91LAC875). The corresponding 4-amino compounds are only obtained in small amounts. A similar observation was made on the low temperature oxidative amination of 2-amino-5-R-3-nitropyridines (R = H, Cl, Br). 

Oxidative amino-dehydrogenation of 2-, 4-, and 6-hydroxy-3-nitropyri-dines and of 4-amino- and 6-amino-3-nitropyridines met little success. 

Due to its enhanced jr-deficiency 3,5-dinitropyridine has a lower site selectivity and it can be expected that oxidative amino-dehydrogenations will take place at all three positions 2, 4, and 6. This has indeed been found. 3,5-Dinitropyridine gives a complex mixture of 2-amino-, 2,6-diamino-, 2,4-diamino-, and 2,4,6-triamino-3,5-dinitropyridines (Scheme 5) (85JOC484, 93ACS95). Mixtures of diamino- and triamino-3,5-dinitropyridines have also been found in the oxidative amination of 2-R-3,5-dinitropyridines (R = NH2, OH, Cl, OMe) and 4-R-3,5-dinitropyridines (R = NH2, Cl). 

The oxidative amino-dehydrogenation of azines is treated by Henk van der Plas (Wageningen University, the Netherlands) who has played a major role in exploiting this interesting field emphasizing developments that occurred since the review of related work by McGill and Rappa in Advances in Heterocyclic Chemistry, Volume 44, which appeared in 1988. 

Oxidative amino-dehydrogenation of azines , van der Plas, H., Adv. Heterocycl. Chem., 2004, 86, 42. 

R 535 H. van der Plas, Oxidative Amino-Dehydrogenation of Azines , Adv.Heterocycl.Chem., 2004,86,1... 

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