Hansch, Corwin et al. published their research in Journal of Organic Chemistry in 1955 | CAS: 66490-20-8

Synthesis of 6-substituted thianaphthenes was written by Hansch, Corwin;Schmidhalter, Beno. And the article was included in Journal of Organic Chemistry in 1955.Synthetic Route of C8H5ClS This article mentions the following:

When 2,4-HS(H₂N)C₆H₃Et is dehydrogenated according to H., et al. (C.A. 45, 6542c), at 445°, 81% 6-amino-thianaphthene (I), m. 114-15°, is obtained (Bz derivative, m. 129.5-30°). I picrate, yellow needles, m. 198-200° (decomposition). Diazotizing 4.37 g. I in 25 cc. H₂O and 10 cc. HCl with 2.76 g. NaNO₂ in 5 cc. H₂O at below 5° and heating the diazo solution 0.5 h. on a water bath with 8.8 g. CuCl in 25 cc. HCl and 7.5 cc. H₂O give 3.46 g. 6-chloro analog, m. 42-3° [picrate (II), m. 74-5°]. Diazotizing 3 g. I and refluxing the solution with 20 cc. H₂SO₄ and 15 cc. H₂O give 0.5 g. 6-hydroxy analog (III), m. 102-2.5° (p-nitrobenzoate, prepared by refluxing III with p-O₂NC₆H₄COCl and C₅H₅N 1 h., m. 149-50°). Diazotizing 10 g. I and adding the solution to a mixture of 9.8 g. CuCl in 15 cc. H₂O, 12.4 g. NaCN in 35 cc. H₂O, and 50 cc. PhMe at 0°, stirring the mixture 1 h., and heating it 2 h. at 60° give 3.8 g. 6-cyano analog, b_0.1 105-6°, m. 41.5-2°, which (0.5 g.), refluxed with 5 cc. 75% H₂SO₄, gives 463 mg. corresponding acid, m. 215-16°. Diazotizing 15.4 g. 2,4-(H₂N)ClC₆H₃CO₂H in 50 cc. H₂O and 20 cc. HCl at 0° with 6.9 g. NaNO₂ in 15 cc. H₂O, pouring the solution into 24 g. Na₂S.9H₂O and 3.6 g. NaOH in 35 cc. H₂O at below 5°, keeping the mixture several hrs., and acidifying it give 7.82 g. [5,2-Cl(HO₂C) C₆H₃]₂S₂, m. 309-11° (decomposition), which (7 g.) is refluxed 0.5 h. with 11.5 g. Na₂CO₃ and 8.5 g. Na₂S₂O₄ in 85 cc. H₂O, then CH₂ClCO₂Na (from 8.5 g. acid) in 110 cc. H₂O is added, and the mixture refluxed 1 h., giving 7.24 g. 4,2-Cl(HO₂C)C₆H₃SCH₂CO₂H (IV), m. 190-5° (decomposition). Refluxing 3 g. IV with 1.5 g. NaOAc and 8 cc. Ac₂O 1 h., diluting the mixture with Et₂O, and evaporating the washed (NaHCO₃) Et₂O solution leave 2.14 g. oil which, refluxed with 50 cc. 10% NaOH and steam distilled, gives 1 g. 3-hydroxy-6-chlorothianaphthene (V), m. 143°. Refluxing 0.8 g. V in 12 cc. AcOH 1 h. with 2 g. Zn dust, making the solution alk., steam distilling it, and treating the distilled oil with picric acid give 0.6 g. II. Refluxing 5 g. 4-oxo-4,5,6,7-tetrahydrothianaphthene (VI) in 25 cc. C₅H₅N and 25 cc. absolute EtOH 8 h. with 5 g. H₂NOH.HCl gives 4.8 g. VI oxime (VII), m. 131-2°. Dry HCl is passed into 3.8 g. VII in 25 cc. AcOH and 4 cc. Ac₂O 0.5 h. at 20° and 2 h. at 100°, the cooled mixture diluted with H₂O and extracted with Et₂O, giving 1.1 g. 4-aminothianaphthene (VIII) (Ac derivative, m. 133-4°). Diazotizing VIII and treating the diazo solution with CuCl in HCl give 4-chlorothianaphthene, isolated as picrate, m. 135-6°. In the experiment, the researchers used many compounds, for example, 6-Chlorobenzothiophene (cas: 66490-20-8Synthetic Route of C8H5ClS).

6-Chlorobenzothiophene (cas: 66490-20-8) belongs to benzothiophene derivatives. Functionalized benzothiophenes are important constructs found in molecules with wide ranging biological activity and in organic materials. Due to its aromaticity, thiophenes do not exhibit the same properties as conventional thioethers.Synthetic Route of C8H5ClS

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem