Ruthenium‐Catalyzed Cascade Reactions of Diynes with Norbornadiene – Synthesis of Norbornene Derivatives

Abstract Norbornene derivatives 7–11 were prepared from norbornadiene and the corresponding diynes by Ru‐catalyzed [(2+2)+2] cycloaddition and subsequent transfer hydrogenation. The structure and stereochemistry of the cycloadducts were confirmed by X‐ray crystal analysis. This procedure provides high diastereoselectivity to generate norbornenes 7–11 in up to 82 % yield. The scope and limitations of this reaction were investigated. Compounds that contained the skeleton of 1,7‐diaryl‐1,6‐heptadiynes were suitable starting materials. Additionly, 9h was empolyed in the synthesis of polynorbornene 31 by ring‐opening metathesis polymerization (ROMP). The number‐average molecular weight (Mn) and polymer‐distribution index (PDI) of this new polymer were determined to be 28.6 kDa and 1.35, respectively.