Modular Synthesis of Cross‐Conjugated Triethynylethylenes via Double Sonogashira Coupling: A Platform for π‐Extended Frameworks

Abstract This study presents an efficient chemoselective synthesis of a series of Y‐shaped cross‐conjugated triethynylethylenes. The rapid synthesis of these densely conjugated triethynylethylenes was achieved in a short reaction time of 1–1.5 h through dual Sonogashira cross‐coupling of bifunctional 4,4‐dibromobut‐3‐en‐1‐ynes with terminal alkynes under ambient conditions. This method proved highly effective for gram‐scale synthesis, yielding a library of 58 triethynylethylenes with good to excellent yields (upto 98%). It was found that the generated triethynylethylenes were amenable to late‐stage functionalization via Heck reaction and could also be subjected to annulation reactions to furnish polycyclic aromatic hydrocarbons (PAHs). The process operates under mild reaction conditions in short reaction time, avoids the use of hazardous alkynyl metal reagents, and supports a wide range of substrates.