Chemoselective N-Heterocyclic Carbene-Catalyzed Cross-Benzoin Reactions: Importance of the Fused Ring in Triazolium Salts

Abstract

Morpholinone- and piperidinone-derived triazolium salts are shown to catalyze highly chemoselective cross-benzoin reactions between aliphatic and aromatic aldehydes. The reaction scope includes ortho-, meta-, and para-substituted benzaldehyde derivatives with a range of electron-donating and -withdrawing groups as well as branched and unbranched aliphatic aldehydes. Catalytic loadings as low as 5 mol % give excellent yields in these reactions (up to 99%).

Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes

“…Gravel engineered a catalytic system that selectively forms the cross-benzoin products between aliphatic aldehydes and aryl aldehydes. 61 Remarkably, the catalyst selectively forms the Breslow intermediate with the aliphatic aldehyde, and then adds to the aromatic aldehyde, obviating the need for a large excess of one aldehyde. Furthermore, using related chiral triazolium A 20 , Gravel effected the reaction in a promising 40% ee.…”

Theoretical investigation on the chemoselective N-heterocyclic carbene-catalyzed cross-benzoin reactions

“…[2][3][4] Since NHC compounds are often more economical and environmentally friendly compared with CNanion catalyst, 5 the metal-free catalyzed processes are interesting alternatives to classical organic transformations. 6 Although the NHC-catalyzed cross-benzoin reaction dates back to 1943, 7 the chemoselective coupling of two different aldehydes, still remains elusive up to now, 8 which has become the focus in this research field. 6 Although the NHC-catalyzed cross-benzoin reaction dates back to 1943, 7 the chemoselective coupling of two different aldehydes, still remains elusive up to now, 8 which has become the focus in this research field.…”

Foundations and strategies of the construction of hybrid catalysts for optimized performances

“…Coordination of N 2 to a homogeneous transition metal complex is sought to achieve nitrogen fixation under mild conditions, but reports of the catalytic reduction of N 2 to NH 3 are limited 9 . Chirik and colleagues 10 reported zirconium complexes that allow direct Aldol reaction Proline 40 Chitosan aerogel 41 Aldolase 42 Alkene epoxidation Fe complex 43 A family of isoreticular chiral MOFs 44 P450 BM-3 139-3 45 Alkene hydration H + Acidic zeolite 46 Phenolic acid decarboxylases 47 Alkene hydrogenation Fe complexes 48 Supported metal clusters 49 Old Yellow Enzymes 50 Benzoin condensation N-heterocyclic carbene 51 Polymer-supported imidazolium salts 52 Benzaldehyde lyase 53 Epoxide ring opening (salen)Co 54 Chromium complexes bound to silicates 55 Halohydrin dehalogenase 56 Esterification NaOH Silicates MCM-41 57 Coenzyme A 58 Glucose isomerization Organic Brønsted base 59 Tin-containing zeolites 60 Glucopyranose mutarotation 61 Halogenation Pd complexes 62 Pd@MOF nanocomposites 63 Halogenases 64 Hydrolysis of esters Cyclodextrin dimer 65 MOF UiO-66-NH 2…”