1.2.3.4- Tetrahydrobenzo pyrimidines

The pyrimidine derivative (177 R = Me) is obtained by dehydrogenation of 2-acetamido-4,5,6,7-tetrahydrobenzo[ ]thiophene-3-carb-oxamide.114 The related compound (177 R = H) is obtained by treatment of ethyl 2-aminobenzo[6]thiophene-3-carboxylate with formamide.114... 

Indolin-2-on-3yl)hydrazino-5,6,7,8-tetrahydrobenzo[fe]thieno[2,3-d]-pyrimidine 185 showed 10-20% herbicidal activity against pigweed, velvet leaf, red millet, green foxtail, and soya bean (81JHC1277). 

Formamide is a powerful C-N-heterocyclization reagent. 2-Formamidino derivatives are intermediates. Robins transformed 3-aminopyrazole-4-carboxamide to a 4-oxopyrazolo[3,4-d]pyrimidine (155)95 by heating in formamide. In boiling formamide, 155 was obtained from ethyl 3-aminopyrazole 4-carboxylate (38)31 (Scheme 35). From the enamino ester 59 and formamide a 5,6,7,8-tetrahydrobenzo [b] thieno [2,3-d ] pyrimidin-4-one (156) was obtained,96 as well as the aromatic thionaphtheno[2,3-d]-pyrimidine (157).97 This heterocyclization method shows broad applicability... 

Chloromethyl-5,6,7,8-tetrahydrobenzo [b]thicno[2,3-d] pyrimidin-4(3// )-one 179 decreased the levels of all types of lipids in hyperlipemic rabbits and of triglycerides in guinea pigs and rats. Furthermore, acute and chronic toxicity studies showed the compound to be safe. It was concluded that compound 179 can be developed as a potential antihyperlipaemic drug (90AF567). 

Ethoxalyl chloride (Et02C—COC1) in pyridine converted 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide to the 2-ethoxalylamino analog, which was heated at 260°C to give ethyl 5,6,7,8-tetrahydro-4-oxobenzo-thieno[2,3-d]pyrimidine-2-carboxylate (142) (moderate yield).215... 

Prasad et al. described [93] an expeditious synthesis of 6-substituted-2,3,4-trihydropyrimido[l,2-c]9,10,ll, 12-tetrahydrobenzo[b]thieno[3,2-e]pyrimidines (92) under microwave irradiation in good yield (Scheme 29). The first... 

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