2-Methoxy-l ,2,4-triazines

A similar migration of the methyl group was found in 3-methoxy-l,2,4-triazine 2-oxides 18 under the same conditions to afford the 2-methoxy-l,2,4-triazin-3(2H)-on 125 (84TL1677). 

Heating 3-methoxy-l,2,4-triazine (70) for 2 hours to 200 °C led to the isolation of 2-methyl-l,2,4-triazin-3-one (352) <53CR(235)1310). When 6-methoxy-5-dimethylamino-... 

Dichloro-5-methoxy-l,2,4-triazine (1.80 g, 10 mmol) in anhyd benzene (30 mL) was hydrogenated in the presence of Et3N (3.30 mL, 24 mmol) and 10 % Pd/C catalyst. The temperature was kept below 20 °C. After absorption of the theoretical amount of hydrogen (448 mL) the catalyst was filtered, the filtrate evaporated and the residue purified by sublimation (40°C/0.2 Torr) yield 1.07 g (97%) colorless crystals mp 49 °C. 

Methoxy-l,2,4-triazin-3-amine and 3,6-dichloro-l,2,4-triazin-5-amine are transformed into the imino-/4-sulfanes by reaction with dimethylsulfide bis(trifluoromethanesulfonate) (from DMS0/Tf20),292 e.g. formation of 16. 

Methoxy-l,2,4-triazine 1-oxide (93) with methyl iodide in methanol at room temperature for 10 days produced 2-methyl-1,2,4-triazin-3-one 1-oxide (94). 3-Methoxy-l,2,4-triazine 2-oxide (95)... 

Neat heating of 3-phenyl-5-methoxy-l,2,4-triazine (118) in the presence of dimethyl ethyne-dicarboxylate gave methyl 2,9-dimethoxy-3,4-bis(carbomethoxy)-7-phenyl[ 1,3]oxazino[2,3-/][l, 2,4]-triazine-2-yl]propiolate (119) and other products (120) and (121) (Scheme 15) <77LA1718>. 

J(P1)2549, 2004S2893>, as exemplified by the reaction of 3-methylthio-5-methoxy-l,2,4-triazine 85 with phenyllithium leading to 3-methylthio-5-methoxy-6-phenyl-l,2,4-triazine 86 (Scheme 48) <2002J(P1)2549>. 

Nucleophilic substitution of hydrogen Sn can also be combined with the displacement of a good leaving group as illustrated by the reaction of 3-phenyl-5-methoxy-l,2,4-triazine with resorcinol, proceeding via the intermediate o -adduct and affording benzofuro[2,3-e]-l,2,4-triazine according to the tandem Sn -Sn cyclization protocol (Scheme 57) [175]. 

Derivatives of 3-oxo-l,2,4-triazine 1-oxide undergo alkylation with various alkylating agents. Thus the reaction of 3-methoxy-l,2,4-triazine 1-oxide 20 with 2,3,5-tii-(9-benzoyl-/3-D-ribofuranosyl bromide, followed by the removal of the benzoyl protection with sodium methoxide, leads to an abnormal nucleoside 4-(/3-D-iibofuranosyl)-l,2,4-triazin-3(4//)-one 1-oxide 21 (73JOC3277). 

The reaction of 4-methoxy-3-nitropyridines 129 with guanidine under similar conditions results in 3-aminopyrido[3,4-e]-l,2,4-triazine 1-oxides 130 (76MI). 

Reaction of l,2,4-triazin-5-ones (151, 152) or 5-methoxy-l,2,4-triazines (156) with Grignard reagents afford, depending on the structure of the 1,2,4-triazine used, 1,2,4-triazines (153), 3,4-dihydro- (154), or 1,6-dihydro-1,2,4-triazin-5-ones (155) (73JHC559). 

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