One-pot Synthesis of Alkynylated Coumarins via Rhodium-Catalyzed Annulation of Aryl Thiocarbamates with 1,3-Diynes or Terminal Alkynes

A convenient and selective synthesis of alkynylated coumarins from various aryl thiocarbamates and 1,3-diynes or terminal alkynes via rhodium-catalyzed C-H bond activation has been developed. In this transformation, both symmetrical and asymmetrical 1,3-diynes could be applicable, obtaining various 3-alkynylated coumarins in moderate to excellent yields. When the substituent is aryl group, the resulting compounds were found to exhibit intense fluorescence in the range of 412-443nm with quantum yield of up to 0.57 in CH2Cl2. Moreover, the internal alkynes were readily converted to 1,2-dione, olefins, alkanes, and bisheterocycles under certain conditions.