Abstract
Abstract 6-Mercapto-1-methylquinolin-2(1 H )-one ( 3 ) was prepared in situ by the reductive cleavage of the corresponding disulfide 2 with Zn dust and acid. The disulfide 2 was in turn prepared via xanthate after diazotisation of 6-amino-1-methylquinolin-2-(1 H )-one ( 1 ). 6-(4-Aryloxybut-2-ynylthio)-1-methylquinolin-2(1 H )-ones ( 5a-e ) were prepared from thiol 3 and 1-aryloxy-4-chlorobut-2-ynes ( 4 ). The sulfides 5a-e were then converted into the corresponding sulfoxides 6a-e by treatment with one equivalent of m -CPBA in CH 2 Cl 2 at 0–5°C for 30 min. The sulfoxides 6a-e were refluxed in CCl 4 for 1 h to give the monothio-hemiacetals 7a-e in almost quantitative yields which were then converted into the 1-aryloxyacetyl-1,2-dihydro-6-methylthieno[3,2- f ]quinolin-7(6 H )-ones ( 11a-e ) in almost quantitative yields by simply dissolving in absolute MeOH. Dehydrogenative elimination of product 11a-e when treated with acid generates 1-acetyl-6-methylthieno[3,2- f ]quinolin-7(6 H )-one ( 12 ) in 70–76% yield.
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