Copper-Catalyzed Oxy-Alkynylation of Diazo Compounds with Hypervalent Iodine Reagents

Alkynes have found widespread applications
in synthetic chemistry,
biology, and materials sciences. In recent years, methods based on
electrophilic alkynylation with hypervalent iodine reagents have made
acetylene synthesis more flexible and efficient, but they lead to
the formation of one equivalent of an iodoarene as side-product. Herein,
a more efficient strategy involving a copper-catalyzed oxy-alkynylation
of diazo compounds with ethynylbenziodoxol­(on)­e (EBX) reagents is
described, which proceeds with generation of nitrogen gas as the only
waste. This reaction is remarkable for its broad scope in both EBX
reagents and diazo compounds. In addition, vinyl diazo compounds gave
enynes selectively as single geometric isomers. The functional groups
introduced during the transformation served as easy handles to access
useful building blocks for synthetic and medicinal chemistry.