Synthesis and Characterization of Novel Functionally Substituted Planar Pyrimidothienoisoquinolines and Nonplanar (3a R, 4 S, 9a S)-pyrazolo[3,4- g]isoquinolines

Abstract

7-Acetyl-8-aryl-4-cyano-1,6-dimethyl-6-hydroxy-5,6,7,8-tetrahydroisoquinolin-3(2H)-thiones 2a,b are prepared and dehydrated to give 7-acetyl-8-aryl-4-cyano-1,6-dimethyl-6-hydroxy-7,8-dihydrodroisoquinolin-3(2H)-thiones 6a,b via a novel method by heating with acetyl chloride in acetic acid. The reaction of both compounds 2a,b and 6a,b with N-aryl-2-chloroacetamides 7a-c under two different conditions gave the same corresponding products, 7-acetyl-8-aryl-3-(N-aryl)carbamoylmethylsulfanyl-4-cyano-1,6-dimethyl-7,8-dihydroisoquinolines 8a-e, in high yields. On treatment of compounds 8a,b,e in methanol with a slightly excess molar amount of sodium methoxide, they underwent intramolecular Thorpe-Ziegler cyclization followed by spontaneous aromatization, providing the planar 7-acetyl-1-amino-6-aryl-2-(N-aryl)carbamoyl-5,8-dimethyl-8,9-dihydrothieno[2,3-c] isoquinolines 9a,b,e in good yield. Cyclocondensation reactions of 6a,b with phenyl hydrazine, thiosemicarbazide, or hydrazine hydrate led to the formation of nonplanar (3aR, 4S, 9aS)-pyrazolo[3,4-g]isoquinolines 11a, 11b, and 13, respectively. The reaction of compound 13 with 2-chloromethylquinazolin-4(3H)-one in the presence of anhydrous sodium acetate gave the expected thienopyrazoloisoquinolone 14. Heating the latter compound (14) with triethyl orthoformate in glacial acetic acid afforded the fused heptacyclic compound 15. All of the synthesized compounds were characterized based on their full spectral analyses such as IR, 1H nuclear magnetic resonance (NMR), and mass spectrometry (MS). Moreover, the crystal structure of compound 6a was elucidated by X-ray diffraction analysis.