Enantioselective N‐Heterocyclic Carbene Catalyzed Aza‐Benzoin Reaction of Enals with Activated Ketimines

N‐Heterocyclic Carbene Catalyzed [4+3] Annulation of Enals and o‐Quinone Methides: Highly Enantioselective Synthesis of Benzo‐ε‐Lactones

“…To further take the advantage of hydrogen bonding, the NHCs B1-B3 with an a,a-bis(3,5-di(trifluoromethyl)phenyl) hydroxy substituent were tested. B1 and B2, which worked well for the aza-benzoin reaction of enals with activated ketimines, [22] showed comparable results as A2 (entries 3 and 4). Much better performance was observed (90 % yield, 3:1 d.r.…”

Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes

“…80 Ye demonstrated the coupling of enals with trifluoromethyl ketones with excellent enantioselectivity, using chiral triazolium B 23 . 81 Interestingly, these conditions tolerated other electron withdrawing groups on the imine (Scheme 29). …”

An Overview the N-Heterocyclic Carbene-Catalyzed Aza-Benzoin Condensation Reaction

“…The choice of the catalyst is the key factor that controls the chemoselectivity of these three species. Ye studied the influence of steric and electronic factors of a series of L-pyroglutamic acid-derived triazolium salts on the reactivity of cynnamaldehyde with N-Boc-protected trifluoromethyl phenyl ketimine (Scheme 17) [36].…”

“…Scheme 17. Selected examples of enantioselective intermolecular aza-benzoin condensation using enals from Ref [36].…”

“…The aza-benzoin products were obtained with good yields and high enantiomeric excesses (Scheme 18). [36].…”