Stereoselective Synthesis of π-Enriched Conjugated Dienynals via Photochemical Alkynyl Carbene Insertion into Furans

The first photochemical carbene insertion reaction into furans is developed for the stereoselective synthesis of π-extended conjugated dienynal and dienynone scaffolds. The protocol harnesses sustainable visible light and does not demand any additives or photocatalysts. It provides a wide variety of densely functionalized dienynal/dienynone carboxylates in good yields with excellent selectivity (40 examples, up to 83% yield and (2<i>E</i>, 4<i>E</i>)-isomer). Furthermore, the developed strategy is scalable, and the downstream transformations are demonstrated toward obtaining valuable products.