N-Heterocyclic carbenes as chiral Brønsted base catalysts: a highly diastereo- and enantioselective 1,6-addition reaction

Abstract

Highly diastereo- and enantioselective 1,6-addition of β-keto amides to p-quinone methides catalyzed by N-heterocyclic carbenes via ion-pair interaction is developed.

Scandium(III)‐Catalysed Decarboxylative Addition of β‐Ketoacids to para‐Quinone Methides: Evidence for 1,6‐Addition and Base‐Assisted Decarboxylation Tandem Process

“…But surprisingly, the catalytic conjugate addition reactions of p ‐QMs became prevalent very recently, especially those examples of reacting with 1,3‐dicarbonyl compounds are rare . Generally, these reactions can be classified into different catalytic system: (1) Fan's chiral ammonium phase‐transfer catalyst and Cao & Wu's amide‐phosphonium salt as bifunctional phase‐transfer catalyst;, (2) Guin's NHCs and Anand's carbenes as brønsted base catalysts;,, (3) Wang's Mn(OAc) 3 ⋅H 2 O/ferrocenyl triazole ligands catalytic system . To the best of our knowledge, there is no report of catalytic decarboxylative addition to p ‐QMs by using β ‐ketoacids as 1,3‐dicarbonyl nucleophiles.…”

Polyfunctional Sterically Hindered Catechols with Additional Phenolic Group and Their Triphenylantimony(V) Catecholates: Synthesis, Structure, and Redox Properties

“…The CV data for thioethers L1-L3 and triphenylantimony(V) catecholates 1 and 2 in CH2Cl2 (GC anode, С = 3•10 −3 М, Ar, 0.15 M Bu4NClO4, vs Ag/AgCl/KCl(sat.)). The oxygen-to-carbon bonds O(1)-C(1) and O(2)-C(2) (1.358(2) and 1.366(2) Å, respectively) are ordinary and typical for catecholato complexes of different metals [65], and bond O(3)-C(19) (1.376(2) Å) is the longest O-C bond in 1, which is typical for sterically hindered phenols [66][67][68]. The six-membered carbon ring C(1-6) is aromatic, with average C-C bond distances of 1.400 ± 0.015 Å, which is very close to the same value for catechol L 1 .…”

“…The oxygen-to-carbon bonds O(1)-C(1) and O(2)-C(2) (1.358(2) and 1.366(2) Å, respectively) are ordinary and typical for catecholato complexes of different metals [65], and bond O(3)-C(19) (1.376(2) Å) is the longest O-C bond in 1, which is typical for sterically hindered phenols [66][67][68]. The six- Figure 1.…”

An efficient construction of CN bond under catalyst‐free and room temperature conditions

“…para ‐Quinone methides ( p ‐QMs) are found in many natural products 4 and are often used in los of significant processes. Under investigation, 1,6‐conjugate addition, 5 [2 + 1], 6 [3 + 2], 7 [4 + 1], 8 [4 + 2] 9 ‐cyclization reaction, 9 Rauhut–Currier reaction, 10 intramolecular click cycloaddition 11 1,6‐addition/cyclization, 12 and asymmetric 1,6‐addition, 13 were effectively developed by many research groups. Recently, we also reported the Ru‐Catalyzed δ ‐arylation of p‐ QMs with aryl diazonium salts to give Fuchsones 14 .…”