THIENO BENZOPYRANS AND THIOPYRANO BENZOPYRANS,INTERMEDIATES FOR THEIR PREPARATION AND METHOD OF MAKING THEM

1298620 Thionobenzopyran and thiopyranobenzopyran derivatives ARTHUR D LITTLE Inc 13 July 1970 [25 Aug 1969] 28148/72 Divided out of 1298619 Heading C2C Novel benzopyrans having the Formula I wherein R 2 is C 1-20 alkyl or a cycloalkylalkyl in which the cycloalkyl moiety is C 3-8 and the alkyl moiety is C 1-6 , m is 1 or 2, n is 0 or 1 and the sum of m + n is 2 or 3 may be prepared by condensing an ester in which the COOAlkyl and = O groups are attached to adjacent carbon atoms with a resorcinol in the presence of an acid catalyst. The compounds may be used as intermediates in the synthesis of therapeutic thienobenzopyrans and thiopyranobenzopyrans of the parent case. The intermediate methyl 3-oxo-2,3,4,5-tetrahydrothiophene-2-carboxylate may be formed by cyclization of methyl 3 - (methoxycarbonylmethylthio)propionate which is in turn formed by a literative method. Methyl 4-oxo-2,3,4,5- tetrahydrothiophene-3-carboxylate is formed as a by-product in the cyclization.