C3-Symmetric chiral trisimidazoline: the role of a third imidazoline and its application to the nitro Michael reaction and the α-amination of β-ketoesters

Recent Advances in the Synthesis of Imidazolines (2009–2020)

“…[14] In recent years, many imidazoline compounds have been used as chiral auxiliaries [15] in enantioselective reactions, as a result of the relative ease of insertion of chirality around the imidazoline ring. Many common reactions, including Michael reactions, [16] Mannichtype reactions, [17] Friedel-Crafts reactions, [18] Mizoroki-Heck reactions, [19] Diels-Alder reactions, [20] Henry reactions, [21] Suzuki-Miyaura coupling reactions [22] have utilized imidazoline catalysts to achieved outstanding enantioselectivities.…”

The Role of Symmetry in Asymmetric Catalysis

“…When this catalyst was assessed in the same conjugate addition as the other catalysts, the product was obtained with 79 % ee , i.e. with higher selectivity than using 10 , although not as high as using 11 ; a likely explanation to the observed enantioselectivities is that with 12 , reaction at the site surrounded by two imidazoline rings was favored, although blocking of the remaining sites was incomplete 24…”

“…They studied chiral imidazolines as catalysts for conjugate additions of β‐ketoesters to nitroolefins. [23] Comparison of the result using catalysts 9 – 11 with one, two, or three imidazoline units, respectively, led to the conclusion that the catalytic reaction preferentially occurred at sites surrounded by two imidazoline units 24. This assumption was supported by comparison of the rates of reactions catalyzed by 10 and 11 (use of 7.5 mol % of 10 and 5 mol % of 11 resulted in comparable reaction rates); a reaction taking place in the neighborhood of a single imidazoline was slow and also unselective.…”

Phenylalanine‐Derived Imidazolines Bearing Heteroaromatic Pendants: Synthesis, Characterization, and Application in the Asymmetric Henry Reaction

“…-W ithin last two decades,i midazolines evolved into widely investigated compounds,mainly due to their prospectiveapplications in pharmaceutics and organic synthesis.S hortly aftert he discovery of the imidazoline receptor (imidazoline binding site)in1984 [1] [2], imidazoline became amedicinally interesting organic scaffold. Imidazolines were also tested as organocatalysts in diastereoselective synthesis of trans-b-lactams [25]a nd in nitro Michael reaction [26] [27]achieving chemical yields up to 51% and 98% with diastereomeric ratios 50 :1 and 20 :1,respectively. Va riousi midazoline complexes with different transition metals and ions were successfully applied as optically active catalysts in asymmetric reactions such as Henry [3] [4], Heck [5 -9], Suzuki [10] [11], DielsÀAlder [12] [13], and FriedelÀCrafts reactions [14 -19],a sw ell as in allylic substitutions [20 -22] and asymmetric reductions [23] [24].…”

“…Apart from very popular 4,5-diphenylimidazolines [4][12] [14 -18][20] [23][24] [26] [27], we have recently reported on two new series of imidazolines including hexahydro-1H-benzo[d]imidazoles (cyclohexane-imidazolines) [ 43]a nd camphorimidazolines [44] [45]with different substituents at C(2) (Fig. 1).…”