Useful N-Heterocyclic Carbene Precatalysts “Bode Catalysts”

Recently, there have been many reports on carbon-carbon bond forming processes mediated by N-heterocyclic carbene (NHC) catalysts. Bode et al. have reported the high-yield and highly enantioselective synthesis of heterocyclic compounds using an NHC precatalyst 2. For example, an NHC in situ generated from 2 catalyzes the inverse electron demand Diels–Alder reaction of activated α,β-unsaturated aldehydes with α,β-unsaturated imines to afford the dihydropyridinones with remarkable enantioselectivities.^1a)

In case of using α-chloroaldehydes and α,β-unsaturated ketones, the oxodiene Diels–Alder reaction proceeds to afford the desired products with excellent enatioselectivities, with no more than 0.5 mol% of the catalyst.^1b)

In addition, an achiral precatalyst 3 is also a useful precursor for the NHC-catalyzed redox esterification^2a) and amidation^2b) of α-functionalized aldehydes.

*For easier handling, 3 is sold as a perchlorate salt, instead of a chloride salt as reported in the literatures.