(+/-)8-Amino-5,6,7,8-tetrahydroisoquinolines as novel antinociceptive agents

Synthesis, Characterization, and Crystal Structure of Some New Tetrahydroisoquinolines and Related Tetrahydrothieno[2,3-c]isoquinolines

The starting compounds 7-acetyl-8-aryl-4-cyano-1,6-dimethyl-6-hydroxy-5,6,7,8-tetrahydroisoquinoline(2H)-3-thiones 3a,b were synthesized and reacted with some N-aryl-2-chloroacetamides 4a-e in the presence of sodium acetate to produce 7-acetyl-8-aryl-3-(N-arylcarbamoylmethylsulfanyl)-4-cyano-1,6-dimethyl-6-hydroxy-5,6,7,8-tetrahydroisoquinolines 5a-g. Upon heating in ethanol containing sodium ethoxide, they underwent intramolecular Thorpe-Zeigler cyclization, affording the corresponding 7-acetyl-1-amino-6-aryl-2-(N-arylcarbamoyl)-5,8-dimethyl-8-hydroxy-6,7,8,9-tetrahydrothieno[2,3-c]isoquinolines 6a-g. Compounds 6c,g,f were converted into the corresponding 1-(1-pyrrolyl) derivatives 7a-c by heating with 2,5-dimethoxytetrahydrofuran in glacial acetic acid. Structures of all synthesized compounds were characterized by elemental and spectral analyses. Also, the crystal structure of compounds 5a was determined by X-ray diffraction analysis.

Crystallographic and spectroscopic characterization of 2-[(7-acetyl-4-cyano-6-hy-droxy-1,6-dimethyl-8-phenyl-5,6,7,8-tetra-hydro-isoquinolin-3-yl)sulfan-yl]-N-phenyl-acetamide

In the title mol-ecule, C28H27N3O3S, the heterocyclic portion of the tetra-hydro-iso-quinoline unit is planar and an intra-molecular N-H⋯N hydrogen bond and a C-H⋯π(ring) inter-action help to determine the overall conformation. In the crystal, a layer structure with the layers parallel to (10) is generated by O-H⋯O and C-H⋯O hydrogen bonds.

A facile synthesis of pyrrolo-(di)-benzazocinones via an intramolecular N-acyliminium ion cyclisation

A facile, moderate to high yielding synthesis of hexahydro-(di)-benzazocinones is described via an intramolecular N-acyliminium ion cyclisation. The iminium ion intermediates are formed from the readily available 4,4-diethoxybutyl amides with an excess of triflic acid. For electron-withdrawing substituents, better yields were obtained from the pre-formed 2-hydroxypyrrolidine amides. From NMR studies, at ambient temperatures the pyrrolo-benzazocin-3-ones exist as a slowly equilibrating mixture of two conformations.