N-heterocyclic carbene-catalyzed generation of alpha,beta-unsaturated acyl imidazoliums: synthesis of dihydropyranones by their reaction with enolates.
Catalytic generation of alpha,beta-unsaturated acyl imidazolium cations and enolates has been achieved, and their involvement in a Michael addition acylation sequence exploited, to provide a range of dihydropyranones. alpha,beta-Unsaturated enol esters, or alpha,beta-unsaturated acid fluorides in association with TMS enol ethers, serve as appropriate substrates for this reaction. The transformation can also be achieved enantioselectively using catalysts derived from chiral triazolium salts.
Ryan
Sarah J
SJ
School of Chemistry, Monash University, Clayton 3800, Victoria, Australia.
Candish
Lisa
L
Lupton
David W
DW