Synthesis and Antimicrobial Activity of Novel Piperidinyl Tetrahydrothieno[2,3-c]isoquinolines and Related Heterocycles
A novel series of 1-amino-2-substituted-5-piperidinyl-
6,7,8,9-tertahydrothieno[2,3-c]isoquinolines (4a−e) was synthesized
upon treatment of 4-cyano-1-piperidinyl-5,6,7,8-tetrahydroisoquinline-
3(2H)-thione (2) with α-halo carbonyl compounds such as
chloroacetone, ethyl chloroacetate, 2-bromoacetophenone, chloroacetamide,
and chloroacetanilide. Construction the pyrrolyl ring
associated with the thienotetrahydroisoquinoline moiety was achieved
by treatment of compounds 4a, b with 2,5-dimethoxytertahydrofuran
in acetic acid. 1-Pyrrolyl-2-substituted-thieno[2,3-c]isoquinolines 5a
and 5b which in turn were used as multipurpose precursors for
synthesis of other new heterocycles. Assignments of the chemical
structures of the respectively synthesized thienotetrahydroisoquinolines
and their derivatives were established on the bases of elemental
and spectral techniques (Fourier transform infrared, 1H NMR, 13C
NMR, and mass spectroscopy). Furthermore, certain compounds were screened for their antimicrobial activity which revealed
promising activities against various pathogenic strains of bacteria and fungi.