Ring-closing metathesis with Pauson-Khand reaction

A branching pathway based on the chemistry of Michael adducts (7) was developed by Porco (Scheme 27.2) [47]. Reduction of the nitro group triggered lactamization to yield y-lactams such as 8. In contrast, with appropriately positioned alkenyl and alkynyl substituents, cyclization via ring-closing metathesis or Pauson-Khand reaction was possible. With =allyl and R =C=CCH20Me, enyne metathesis yielded the cyclic diene 9. In contrast, with R =C=CH and R = allyl, a Pauson-Khand reaction allowed the remarkable bridged cyclopentenone 10 to be obtained. 

The chapter ends with a rather miscellaneous collection of reactions such as one example of an electrocyclic ring closure 19. There are more important examples of ring closing olefin metathesis (RCM) and other organometallic reactions such as the Pauson-Khand reaction and co-trimerisation. 

---