Conrad, J. C.; Eelman, M. D.; Silva, J. A. D.; Monfette, S.; Parnas, H. H.; Snelgrove, J. L.; Fogg, D. E. Oligomers as Intermediates in Ring-Closing Metathesis. J. Am. Chem. Soc. 2007, 129, 1024-1025.
Reading this communication changed the way I think about ring closing metathesis (RCM) reactions. Fogg and coworkers studied the pre-equilibrium product distributions of diene cyclization reactions to form medium and large rings and found that the kinetic products of many such reactions are linear diene oligomers, which equilibrate over time to desired RCM products. Eventually, the product distribution reflects the thermodynamics of the system, which is determined by substrate, concentration, and temperature. It just goes to show that equilibrium doesn’t always tell the whole story.