Dichloromethane → 3,6-dibenzyl-5,6,7,8-tetrahydro-1H-pyrido[4,3-d]pyrimidine-2,4-dione

Participants

Reaction Conditions

Reaction Steps

A mixture of 165 g of methyl 4-amino-1-benzyl-1,2,5,6-tetrahydropyridine-3-carboxylate, 68 g of triethylamine and 100 g of benzyl isocyanate in 700 ml of toluene was heated at the reflux temperature for 8 h, with stirring. After cooling, the reaction mixture was concentrated under reduced pressure. The residue was dissolved in 300 ml of ethanol, 58 g of sodium ethylate in 400 ml of ethanol were added and the mixture was heated at 80° C. for 1.5 h, with stirring. After this mixture had been concentrated under reduced pressure, the residue was worked up by extraction with dichloromethane and water and the combined and dried dichloromethane extracts were concentrated under reduced pressure. The combined aqueous phases were adjusted to pH 7 with conc. hydrochloric acid. After drying, the precipitate formed was combined with the concentrated dichloromethane extracts and the mixture was purified by recrystallization from ethanol to give 81 g of 3,6-dibenzyl-5,6,7,8-tetrahydro-1H-pyrido[4,3-d]pyrimidine-2,4-dione. 10 g of this base were dissolved in dichloromethane and the hydrochloride was precipitated by the addition of a solution of hydrochloric acid in ether. Recrystallization from ethanol/water (volume ratio 1:1) gave 10.1 g of 3,6-dibenzyl-5,6,7,8-tetrahydro-1H-pyrido[4,3-d]pyrimidine-2,4-dione hydrochloride.

Provenance & Evidence