Bridged Azabicycles by Ring-Closing Metathesis

Significance

A diallylboration and Ru-catalyzed ring-closing metathesis route to bridged azabicycles is reported. It features a reductive trans-diallylation of mono- or disubstituted pyridines, isoquinoline and pyrrole followed by successive heating with triallylborane (1 equiv) under which conditions a deprotonation (isopropylene evoluation), deallylation and allylation sequence occurs to give the cis-isomer. Boc protection yields key heterocyclic precursors for the metathesis reactions. The Grubbs first and second generation catalysts I and II are employed in the ring-closing metathesis to give aza-bicyclo[4.3.1]deca-3,7-dienes and aza-bicyclo[4.2.1]nonene derivatives, respectively, in excellent yields (89-98%).