Domino Synthesis of Thiochromenes through Cu-Catalyzed Incorporation of Sulfur Using Xanthate Surrogate

An
efficient domino reaction has been developed for the synthesis
of thiochromenes through Cu-catalyzed in situ incorporation of sulfur.
This domino method avoids the use of less accessible and unpleasant
arenethiols as starting materials, instead utilizes very stable aryl
halides along with potassium ethyl xanthate as an odorless sulfur
surrogate. The domino methodology proceeds through C(aryl)-S coupling, thioester cleavage, sulfa-Michael addition, aldol reaction,
and elimination reaction sequences to provide thiochromenes in good
yields