Heteroring Annulation Using TandemN-Acylamide Methylenation-RCM

Significance

Sequential Petasis and Grubbs metathesis reactions are involved in the construction of indoles, 1,4-dihydroquinolines, and 1,2-dihydroisoquinolines from simple ortho-substituted anilines and benzylamines. Thus methylenation of N-acylamides and Grubbs’ II catalyzed ring-closing metathesis (RCM) of the resulting enamides lead to heteroannulated products in moderate overall yields. This reaction sequence appears to be general and may be also used to synthesize other heterocyclic compounds such as benz­azepines and benzoxazepines. Slow RCM reactions and alkene isomerization appear to be responsible for the low yields of these processes whose scope was insufficiently tested.