3.4- Dihydrothieno 2,3-d pyrimidine

Vovk MV, Bolbut AV, Boiko VI, Pirozhenko W, Chemega AN, Tolmachev AA (2004) Synthesis of 2-trihalomethyl-3,4-dihydrothieno[2,3-d]pyrimidin-4-ones. Chem Heterocycl Compd 40 370-376... 

The action of NaBH4 on 141 (X = X = Cl) gave 2-chloro-3,4-dihydro-thieno[3,4-d]pyrimidines 142, which were used for the synthesis of 2-substituted dihydrothieno[3,4-d]pyrimidines via nucleophilic substitution reactions (81JMC376). 

Benzamido-3-cyano-4,5-dihydrothiophenes (321) cyclize at 120°C with cyclohexylamine, morpholine, piperidine, and pyrrolidine to the corresponding 4-amino-2-phenyl-5,6-dihydrothieno [2,3-d ] pyrimidines (322).181 However, when 321 and 2 equivalents of dimethylamine hydrochloride in pyridine were refluxed for 5 hr, the 4-oxothieno [2,3-d] pyrimidine 323 was formed nearly quantitatively181 (Scheme 92). Ethyl iV-(3-cyano-4,5-dihydro-2-thienyl)oxamates (324) give, with cyanomethylene compounds in the presence of triethylamine, thieno[2,3-d]pyrimidines (325).182... 

Several 4-amino-2-methyIthieno[2,3-d]pyrimidines 49c were synthesized directly by heating o-aminocarbonitriles 48 in a methanolic solution of acetamidine hydrochloride containing sodium ethoxide (83CPB1177). By an indirect route, 4-amino-2-substituted methyl-5,6-dihydrothieno[2,3-d]-... 

---