A facile one-pot synthesis of 2-(prop-2-yn-1-ylidene)-2,3-dihydro-1,4-thiazepines

Abstract

An unprecedented method for the synthesis of 2-(prop-2-yn-1-ylidene)-2,3-dihydro-1,4-thiazepines from N-(2,4-pentadiynyl) β-enaminones is reported. Upon treatment with Lawesson’s reagent, N-(2,4-pentadiynyl) β-enaminones were thionated to furnish N-(2,4-pentadiynyl) β-enaminothiones, which immediately underwent 7-exo-dig cyclization to generate 2-(prop-2-yn-1-ylidene)-2,3-dihydro-1,4-thiazepines in one-pot. A general trend was observed for various N-(2,4-pentadiynyl) β-enaminones and cyclization proceeded with broad functional group tolerance. This operationally easy method may provide quick access to a library of functionalized 1,4-thiazepines in the field of pharmaceutical chemistry.

Graphical Abstract

Keywords:

• Alkynes
• cyclization
• β-enaminones
• Lawesson’s reagent
• N-propargylic N-(2,4-pentadiynyl) β-enaminothiones
• 1,4-thiazepines

Additional information

Funding

We thank the Scientific and Technological Research Council of Turkey [TUBITAK, Grant No. 114Z811] and the Research Fund of Middle East Technical University [METU, Grant No. GAP-103-2018-2770] for financial support of this research.