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A Convenient Synthesis of 2,3‐Dihydro‐4 H ‐thiopyrano[2,3‐ b ]‐, ‐[2,3‐ c ]‐, or ‐[3,2‐ c ]pyridin‐4‐ones by the Reaction of the Corresponding 1‐(Chloropyridinyl)alk‐2‐en‐1‐ones with NaSH
Author(s) -
Kobayashi Kazuhiro,
Imaoka Ayumi
Publication year - 2013
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201200543
Subject(s) - chemistry , medicinal chemistry , stereochemistry , sequence (biology) , biochemistry
2,3‐Dihydro‐4 H ‐thiopyrano[2,3‐ b ]pyridin‐4‐ones 4 were prepared by a three‐step sequence from commercially available 2‐chloropyridine ( 1 ). Thus, successive treatment of 1 with i Pr 2 NLi (LDA) and α , β ‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2 , which were oxidized with MnO 2 to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3 . The reactions of 3 with NaSH⋅ n H 2 O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4 H ‐thiopyrano[2,3‐ c ]pyridin‐4‐ones 8 and 2,3‐dihydro‐4 H ‐thiopyrano[3,2‐ c ]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine ( 5 ) and 4‐chloropyridine ( 9 ), respectively.