Ss. Mandal et al., Studies in sulfur heterocycles. Part 15. Condensed heterocycles derived from thieno[2,3-c]- and thieno[3,2-c]-thiopyrans, J CHEM S P1, (18), 1999, pp. 2639-2644
Several tricyclic compounds obtained by annelation of five- and six-membere
d nitrogen heterocycles onto thieno[2,3-c]- and thieno[3,2-c]-thiopyran are
reported. New expedient syntheses of 7H-thieno[2,3-c]thiopyran-4(5H)-one a
nd 4H-thieno[3,2-c]thiopyran-7(6H)-one are also reported.