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Keywords:

  • cascade reactions;
  • sulfur compounds;
  • annulation
Thumbnail image of graphical abstract

As many as three stereogenic centers were introduced in one step in the preparatively simple cascade reaction of 1-benzothiopyrylium salts with 2-siloxy-1,3-butadienes. The cascade comprises 1,2-additions and subsequent intramolecular 1,4-additions and gives the all-cis-thioxanthon rac-3 in 91% yield from the starting compounds 1 and 2, formed in situ. A diastereoselective synthesis of such compounds was not previously known.