Preparation of 5,6-bis(4-methoxyphenyl)-3-methyl-1,2,4-triazine:
(A) 3-Hydroxy-5,6-bis(4-methoxyphenyl)-1,2,4-triazine 2 moles, 540 g of
anisil (4,4'-dimethoxybenzil), 222 g (2 moles) of semicarbazide hydrochloride,
180 g (2.2 moles) of sodium acetate, and 2.5 liters of acetic acid were heated
at reflux overnight. The cooled reaction mixture was poured into 5 liters of
water. The crude solid product was collected by filtration, washed with water,
and recrystallized from acetic acid, giving 434 g of 3-hydroxy-5,6-bis(4-
methoxyphenyl)-1,2,4-triazine; MP: about 272°-274°C.
(B) 3-Chloro-5,6-bis(4-methoxyphenyl)-1,2,4-triazine:
10 grams of 3-hydroxy-5,6-bis(4-methoxyphenyl)-1,2,4-triazine and 50 ml of
phosphorous oxychloride were heated at reflux for 1.5 hours. The cooled
mixture was poured onto crushed ice and the resultant mixture was extracted
with diethyl ether. The extract was washed successively with 2% sodium
hydroxide and water until the washings were neutral. The ether extract was
dried over anhydrous sodium sulfate and evaporated. The residue was taken
up in ether, filtered, and the filtrate was evaporated to yield 9.0 g of 3-chloro-
5,6-bis(4-methoxyphenyl)-1,2,4-triazine; MP: about 130°-132°C.
(C) 5,6-Bis(4-methoxyphenyl)-3-methyl-1,2,4-triazine:
To a slurry of 11.7 g (0.33 mole) of methyltriphenylphosphonium bromide in
150 ml of dry tetrahydrofuran at -35°C was added, over a 15-minute period,
20 ml (0.033 mole) of n-butyl lithium. The reaction mixture was stirred for
one hour. To the reaction mixture at -35° to -40°C was added over a 10-
minute period a solution of 5.7 g (0.0165 mole) of 3-chloro-5,6-bis(4-
methoxyphenyl)-1,2,4-triazine in 50 ml of tetrahydrofuran. The reaction
mixture was allowed to warm to ambient temperature and was stirred
overnight. A solution of 1.05 g (0.0165 mole) of sodium carbonate in 50 ml of
water was added dropwise to the reaction mixture which then was heated at
reflux for three hours. The reaction mixture was cooled, poured over ice, and
extracted with diethyl ether. The diethyl ether extract was washed with water,
dried over anhydrous sodium sulfate, and concentrated. The concentrate was
chromatographed over silica gel, with three fractions being collected. After
evaporation of solvent, the third fraction solidified; MP: about 109°-113°C.
The solid was identified as 5,6-bis(4-methoxyphenyl)-3-methyl-1,2,4-triazine
by nuclear magnetic resonance analysis, mass spectrographic analysis, and
elemental microanalysis.
