Alkynylation of steroids via Pd-free Sonogashira coupling

Abstract

Cu-catalyzed Pd-free Sonogashira coupling has been proposed as a straightforward and convenient route to valuable steroidal enynes. A biligand catalyst system based on Ph₃P and TMEDA has been designed. The protocol was utilized for the efficient coupling of iodosteroids with diverse terminal alkynes and 1-trimethylsilylalkynes. A possible role of an auxiliary ligand as a phase-transfer catalyst for a sparingly soluble inorganic base (K₂CO₃) was revealed.