Disproportionation of thiachromens to thiachromans and thianaphthalenium salts involving hydride transfer

✍ Scribed by B.D. Tilak; V.M. Vaidya

• Publisher: Elsevier Science
• Year: 1963
• Tongue: French
• Weight: 437 KB
• Volume: 4
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)90660-4

✦ Synopsis

The chemistry of thiachromans, thiachromens, arcmatic thiachramens and thianaphthaleniwn salts has not been widely studied. A few examples 1,2,3. of aromatic thiachrcanens have been reported bjj us earlier. A new synthesis of 4-methylt.hiachromans involviry cyclodehydration of aryl 3-oxo-butyl s.ulphides (I) is now reported. The latter were prepared in good yields (72 -99$) by Michael addition of aryl mercaptans to methyl vinyl ketone (~AVK) in presence of piperidine. Gyclcdehydration of (I), with polyphosphoric acid (WA) was expected to yield thiachromens (II) which would then lead to the desired thiachromans (Ill) by reduction. Me (' ) AT' =aryl se!??d?e 1 B.D. Tilak, Proc. Ind. Acad, Sci, &, 71 (1'351) 2 B.D. Tilak, Tetrahedron & 84 (1960) 3 H.S. Desai, Ph.D. thesis, Bcubay University (1959) .87 Disproportionation of thiachromens No.8 However, when the keto-sulphides (I) ore cyclised by treat+lUeA with PPA, we always obtained thiachramano (III) (yields > 35,%),