Cross Carbonyl-Olefin Metathesis (XCOM) of Unactivated Olefins

A method for the olefination of aryl aldehydes with unactivated alkenes via cross carbonyl-olefin metathesis (XCOM) is described. Reaction of an aldehyde substrate and a cis-1,2-disubstituted or monosubstituted olefin with the HBF4 salt of 2,3-diazabicyclo[2.2.2]octane results in high-yielding olefination with exclusive trans stereoselectivity. The reaction is shown to accommodate a range of substitution patterns on the aryl aldehyde and a diverse set of functional groups, including protic functionality that would complicate traditional olefination methods. We show that product inhibition arising from the aliphatic aldehyde side product limits catalytic turnover, but that distillative removal of this component renders catalysis feasible.