The Dienyl Pauson-Khand Reaction

A study aimed at determining whether intermediates in the [4+2] cycloaddition of dienynes could be trapped with CO has led to the development of a dienyl Pauson-Khand reaction by Wender and co-workers.  In principle multifunctional compounds such as (1) can react by a number of pathways, but by optimising the reaction conditions and the solvent a high yield (89%) of (2) can be realised.

Interestingly the yield was improved by reducing the catalyst loading ([RhCl(CO)(PPh₃)₂] – AgSbF₆) and this also allowed the reaction to be carried out under 1 atmosphere of CO.  In addition this must be one of the few examples in the literature where the isolated yield of product (89%) is higher than the GC yield in solution (88%), albeit only just!  (Angew. Chem. Internat. Ed.. 2003, 42, 1853-1857).