A new carbene-catalyzed [4 + 2] annulation of 2H-azirine-2-carbaldehydes with ketones was developed, thus providing the 2,3-dihydro-6H-1,3-oxazin-6-one core structures with broad scope and good to excellent yields. Notably, the azolium aza-dienolates generated from the addition of NHCs to 2H-azirines are first uncovered.
A chiral carbene-catalyzed
[3+3] annulation of α-bromoenals
with 2-aminobenzimidazoles providing pyrimido[1,2-a]benzimidazoles has been described. This protocol features a broad
scope and good functional group tolerance. Biological studies indicated
that the formed pyrimido[1,2-a]benzimidazole exhibited
moderate cytotoxic activity against tumor cells.
An N-heterocyclic carbene-catalyzed annulation of ynals and amidines has been reported to construct pyrimidin-4-ones. The protocol features a broad substrate scope and mild conditions. Furthermore, an oxidative strategy to catalytically generate ynal-derived acyl azolium intermediates is discussed in this mechanistic study.
The unprecedented enantioselective NHC-catalyzed [3 + 3] annulation of α-bromoenals with amidines via a dual C−N bond formation is described. The protocol allows a rapid preparation of 5,6-dihydropyrimidinones in acceptable yields with good enantioselectivities.
The first study of oxidative synthesis of simple tert-butyl peresters and amides enabled by N-heterocyclic carbene-catalysis using N-fluorobenzenesulfonimide (NFSI) as oxidant is described. The reaction proceeds with green, high yield, board substrate scope and room temperature.
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