Enantioselective synthesis of aza-beta-lactams via NHC-catalyzed [2 + 2] cycloaddition of ketenes with diazenedicarboxylates

N-Heterocyclic Carbene-Promoted Rauhut]Currier Reactions between Vinyl Sulfones and α,β-Unsaturated Aldehydes

N-heterocyclic carbenes (NHCs) promote the addition of 1,1-bis(phenylsulfonyl)ethylene to the α-position of α,β-unsaturated aldehydes. The proposed reaction pathway for this Rauhut-Currier-type reaction includes an unusual conjugate addition of an NHC to a bis-vinyl sulfone.

N-heterocyclic carbene-catalyzed rearrangements of vinyl sulfones

N-heterocyclic carbenes catalyze the rearrangement of 1,1-bis(arylsulfonyl)ethylene to the corresponding trans-1,2-bis(phenylsulfonyl) under mild conditions. Tandem rearrangement/cycloadditions have been developed to capitalize on this new process and generate highly substituted isoxazolines and additional heterocyclic compounds. Preliminary mechanistic studies support a new conjugate addition/Umpolung process involving the ejection and subsequent unusual re-addition of a sulfinate ion.