Acyclic Hydrocarbon α,ω-Dienes: From Biomass and Plastic Upcycling to Carbocycles, Precision Polymers, and Cross-Linked Elastomers.

Acyclic hydrocarbon α,ω-dienes constitute a large class of organic molecules featuring two CC bonds separated by methylene segments of variable length and with an open, linear chain. α,ω-Dienes serve as substrates and (co)monomers in a range of key chemical transformations. These include insertion (cyclo)polymerization, metathesis, cyclization, and hydroformylation to yield chemicals and polymers with potential applications in adhesives, lubricants, impact modifiers, automotive, membranes, and pharmaceuticals. The production of α,ω-dienes currently relies on the conversion of steam-cracking derivatives; however, the high cost, operational complexity, and substantial environmental burden associated to these technologies restrain their use to niche academic studies. The first section of this review provides a concise snapshot of emerging technologies for the production of such α,ω-dienes from biomass-derived feedstocks and via chemical plastic upcycling. These, alternative to petrochemicals, are critical to meet the pressing sustainability goals and to ensure the long-term accessibility of α,ω-dienes. The second and main section surveys the catalytic conversion of α,ω-dienes into carbocycles, (di)aldehydes, precision unsaturated poly(ethylene)s and elastomers. α,ω-Dienes act as modular, programmable molecular "Lego" blocks to access carbocycles, from strained rings to macrocycles, and to polymers with tailored functionalities and strategically placed cleavable sites that facilitate reuse, recycling, deconstruction, and predictable end-of-life behavior.