An expedient route to 2,3-substituted and fused benzo[a]quinolizine-4-thione framework via ring annulation with beta-oxodithioesters.
[figure: see text] An efficient highly convergent route to hitherto unreported 2,3-substituted and annulated benzo[a]quinolizine-4-thiones 3 has been developed. The methodology involves ring annulation of 3,4-dihydro-6,7-dimethoxy-1-methylisoquinoline 1 with a variety of readily accessible acyclic and cyclic beta-oxodithioesters 2 in the presence of triethylamine in refluxing benzene. These benzo[a]quinolizine-4-thiones can be readily converted to the corresponding benzo[a]quinolizine-4-ones 5 via dethiomethylative hydrolysis of the respective benzo[a]quinolizinium salts 4 obtained by alkylation of 3 with methyl iodide.
Roy
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Department of Chemistry, Indian Institute of Technology, Kanpur-208 016, India.
Nandi
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Ila
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Junjappa
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D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry; D007202:Indicators and Reagents; D008968:Molecular Conformation; D015394:Molecular Structure; D011807:Quinolizines / Q000138:chemical synthesis* / Q000737:chemistry; D013871:Thiones / Q000138:chemical synthesis / Q000737:chemistry
D000470:Alkaloids; D004952:Esters; D007202:Indicators and Reagents; D011807:Quinolizines; D013871:Thiones