Synthesis of Some New Tetrahydrobenzo[b]thiophene Derivatives and Tetrahydrobenzothienopyrimidine Derivatives Under Microwave Irradiation

Abstract

2-Phenyl-5,6,7,8-tetrahydro-4H-benzothieno[2,3-d][1,3]oxazin-4-one (4) was reacted with either aliphatic or aromatic primary amines such as benzylamine, cyclohexylamine, p-toluidine, and/or p-anisidine to give carboxamide derivatives 5a–d, respectively. A bifunctional nucleophile such as ethanolamine was also reacted with 4, giving the carboxamide derivative 5e. Aminolysis of 4 with secondary amines such as piperidine and/or morpholine afforded the benzamide derivatives 6a and/or 6b, respectively. Fusion of 4 with hydrazine hydrate yielded the pyrimidine derivative 7 and carbohydrazide derivative 8. Thiation of 4 with phosphorous pentasulfide gave thienothiazine derivative 9, which reacted with benzylamine to give the pyrimidine derivative 10. Carbon nucleophiles such as ethyl cyanoacetate and/or malononitrile were subjected to react with 4 to give oxopropanoate 11 and/or oxopropanoic acid 12 derivatives, respectively. Microwave irradiation of 4 and formamide yielded the pyrimidinone derivative 13, which were subjected to react with phosphorous pentasulfide, a mixture of phosphorous oxychloride and phosphorous pentachloride and/or methyl iodide, to give 14, 15, and/or 16, respectively.

Keywords:

• Microwave
• tetrahydrobenzothiophene
• tetrahydrothienopyrimidine