An efficient N-heterocyclic carbene (NHC)-catalyzed asymmetric conjugate addition
reaction to afford synthetically challenging benzofuranone derivatives having vicinal
all-carbon quaternary and tertiary stereocenters is presented. The reaction operates
solely through noncovalent interaction between a newly designed NHC and the substrates,
providing access to a series of functionalized benzofuranones in good yields and with
high ee values. The protocol applies to preparative-scale synthesis. A catalytic cycle
involving a noncovalent substrate–NHC interaction is implicated in the process, based
on a mechanistic control study.
Key words
asymmetric catalysis - N-heterocyclic carbenes - noncovalent interaction - conjugate
addition - benzofuranones - maleimides