Triazino and tetrazino fused systems

The synthesis, crystal structure and anticancer activity of derivatives of ethyl and methyl (tetrahydroimidazo[2,l-c][l,2,4]triazin-3-yl) formate and acetate have been reported 06EJM539 06EJM1373 . 

The synthesis of the pyrazolo[4,3-e][l,2,4]triazine 52-53 family of natural products, fluvine A, pseudoiodinine and nostocine A have been reported 06JA5646 . 

Pyrazolo[4,3-e][l,2,4]triazine derivatives have been prepared from oximes of 5-aryl- and 5-formyl-l,2,4-triazines 06MI191 . Novel pyrazolo[5,1 -c][ 1,2,4]triazines incorporating an Af-(2-oxoethyl)phthalimide moiety have been reported 06JCR(S)6 . 

The synthesis and structures of 6-amino-l,2,4-triazolo[3,4-/][l,2,4]triazin-8(7i/)-one derivatives 06MI169 06MI444 and of dihydrotetrazolo[5,l-c][l,2,4]triazines have been described 06H1595 . 

Pyrazolo[l,5-a][l,3,5]triazines 58 were obtained by an efficient one-step reaction from iminodithiocarbonates 54 and pyrazole 55, or by an alternative two-step reaction form the aroyl isothiocyanates 56 and pyrazole 55 06TL5441 . 

The synthesis of l,2,4-triazolo[ l,5-J][l,2,4]triazine-5-thiones has been developed in a one pot reaction from 4-amino-l,2,4-triazine-3-thione-5-one and aryl nitriles 05JHC 1021 . 

A novel method for the synthesis of imidazo[5,l [l,2,4]triazin-4(3/7)-ones 57 has been reported by cyclization of A-aminoimidazoles 56, and the method applied for the synthesis of vardenafil 05JOC7331  

A novel one-pot three component synthesis of l,2,4-triazino[3,4-6]thiazolones 60 has been described by condensation of mercaptotriazinones 58, 5-aryl-furan-2-carboxaldehyde 59 and chloroacetic acid 05SC333 . 

Reversible metathesis reactions of 6,7-dihydropyrazolo[l,5-c/][l,2,4]triazin-4-ones and aliphatic aldehydes or ketones have been reported to generate thermodynamically controlled mixtures of heterocycles 05OL4483 . 

The palladium-catalyzed regioselective arylation of imidazo[l,2-fe][l,2,4]triazine 63 afforded 2, 6-difluoro-5 -[3-(l-hydroxy-l-methylethyl)-imidazo[l,2-Z)][l,2,4]triazin-7-yl]biphenylcarbonitrile 65 05JOC5938 . 

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