A Convenient Synthesis of 2,3-Dihydro-4<i>H</i>-thiopyrano[2,3-<i>b</i>]-, -[2,3-<i>c</i>]-, or -[3,2-<i>c</i>]pyridin-4-ones by the Reaction of the Corresponding 1-(Chloropyridinyl)alk-2-en-1-ones with NaSH
作者:Kazuhiro Kobayashi、Ayumi Imaoka
DOI:10.1002/hlca.201200543
日期:2013.4
Abstract2,3‐Dihydro‐4H‐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 iPr2NLi (LDA) and α,β‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2, which were oxidized with MnO2 to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3. The reactions of 3 with NaSH⋅n H2O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4H‐thiopyrano[2,3‐c]pyridin‐4‐ones 8 and 2,3‐dihydro‐4H‐thiopyrano[3,2‐c]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine (5) and 4‐chloropyridine (9), respectively.