Relay ring-closing metathesis, olefins

Hoye TR, Jeffrey CS, Tennakoon MA, Wang J, Zhao H. Relay Ring-Closing Metathesis (RRCM) A Strategy for Directing Metal Movement Throughout Olefin Metathesis Sequences. J Am Chem Soc. 2004 126(33) 10210-10211. 

RCM (1 to 2, Scheme 9.1) is one of the most common and important types of olefin metathesis reaction. Accommodation of considerable structural complexity within A in RCM substrates 1 is one of the hallmarks of this powerful and broadly applicable reaction. Nonetheless and despite significant advantages available by modification of external factors (for example, catalyst selection, additive use, solvent choice, or ethylene concentration), not every diene substrate 1 can be successfully cychzed to cycloaUcene 2. Because of the advent of relay ring-closing metathesis (RRCM, 4a to 4b to 3 to 2, Scheme 9.1), chemists now have an alternative for resuscitating/redirecting these otherwise lifeless/recalcitrant systems when such a limitation is encountered. 

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