N-Heterocyclic Carbene-Promoted Rauhut–Currier Reactions between Vinyl Sulfones and ?,?-Unsaturated Aldehydes

Abstract

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 Umpolung of Styrenes: Mechanistic Elucidation and Selective Tail-to-Tail Dimerization

“…These first intermolecular Michael umpolung reactions constitute a groundbreaking proof of principle but suffered from the fact that only α-substituted acrylates were suitable substrates and the limited scope of the cross-coupling of two different Michael acceptors. The combination of NHCs with Michael acceptors also led to further interesting reactions, similar to the Morita–Baylis–Hillman reaction . In addition, the group of Scheidt has shown that NHCs add to vinyl sulfones, turning these into reactive nucleophiles. , …”

Enantioselective N‐Heterocyclic Carbene Catalyzed Bis(enoate) Rauhut–Currier Reaction

“…Specifically, in 2018, Anand and co‐workers introduced a non‐enantioselective intermolecular RC reaction, with two low‐yielding enoate‐enone example. The groups of Scheidt and Chi have reported elegant, and mechanistically distinct, RC reactions exploiting NHCs as cooperative catalysts or initiators. However, the direct application of chiral NHCs as the sole catalyst is yet to be reported.…”

Highly Enantioselective Intermolecular Cross Rauhut–Currier Reaction Catalyzed by a Multifunctional Lewis Base Catalyst

“…RC reactions mediated by a Lewis base made use of the binding affinity of the catalyst to one of the olefins. Examples of catalysts and substrates include DBU with 2‐cyclohexen‐1‐one,7a an N‐heterocyclic carbene with α,β‐unsaturated aldehydes,7b an imidazole–LiCl catalyst system with nitroolefins,7c,d and phosphine with maleimide 7e. Other concerns and studies focused on domino cyclizations initiated by cross RC reactions 8.…”