Summary
8-Chloro-1-thionaphthol, prepared fromperi-acid, was condensed with bromoacetaldehyde dimethyl acetal to give 8-chloro-1-naphthylω-dimethoxyethyl sulphide (IV). Ring-closure of (IV) gave 3′-chlorobenzo-(1′:2′, 6:7)-thionaphthene (V), which on dechlorination gave 6:7-benzothionaphthene (II). The cyclization product fromα-naphthylω-dimethoxyethyl sulphide (I) reported in the previous communication being different from (II) is therefore naphtho-(1′:8′-bc)-thiapyran (III).
9-Chloronaphtho-(1′:8′-bc)-thiapyran (VII) was prepared from Tobias acid in a manner similar to (V), but dechlorination of (VII) to (III) could not be carried out due to the low yields of (VII) in the cyclization of 2-chloro-1-naphthylω-dimethoxyethyl sulphide (VI).
The literature on the cyclization of certain relatedα-substituted naphthyl, naphthoxy and thionaphthoxy derivatives is discussed.
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Communicated by Dr. K. Venkataraman,f.a.sc.
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Dikshit, V.K., Tilak, B.D. A new synthesis of thiophenes and thiapyrans. Proc. Indian Acad. Sci. (Math. Sci.) 33, 78 (1951). https://doi.org/10.1007/BF03172186
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DOI: https://doi.org/10.1007/BF03172186