Synthesis of C1-symmetric chiral tripodal oxazolines through an oxazoline exchange reaction with amino alcohols

Breaking the C3-Symmetry of Chiral Tripodal Oxazolines: Enantio-Discrimination of Chiral Organoammonium Ions

“…Recently, we disclosed a novel method for the synthesis of the type IIa oxazolines through an oxazoline exchange reaction with amino alcohols mediated by ZnCl 2 . Using this novel method we were able to synthesize various C 1 -BTOs.…”

The development and application of chiral trisoxazolines in asymmetric catalysis and molecular recognition

“…1 Most recently, a novel oxazoline exchange reaction with amino alcohols was also introduced for the synthesis of trisoxazolines. 11 The first chiral trisoxazoline 3 derived from nitrilotriacetate 1 was developed by Katsuki's group, using a direct strategy to construct three oxazolines in concert. 10,12 Nitrilotriacetate 1 reacted with different amino alcohols smoothly under a solvent-free condition.…”

“…With this methodology, modular synthesis of trisoxazoline 6 became more effective than the sequential formation of the third oxazoline via the use of a cyano group as the precursor in bisoxazoline 15 (method A). The scope of this method was demonstrated by the successful synthesis of several heterochiral trisoxazolines 6i-m. 11 Most recently, our group also successfully expanded the pseudo-C 3 -symmetric trisoxazoline 8 based ligand library by modular synthesis, as shown in Scheme 11. This improvement allowed the incorporation of a broad variety of substituents to the stereogenic centre such as benzyl, tert-butyl and indenyl groups to construct homochiral and heterochiral trisoxazolines.…”

Modular Synthesis of Chiral Homo- and Heterotrisoxazolines. Improving the Enantioselectivity in the Asymmetric Michael Addition of Indole to Benzylidene Malonate

“…One directly constructs the three oxazolines from the corresponding carboxylic acids or derivatives thereof. The advantage of this method is to enable the synthesis of such ligands in relatively few steps, and thus, this strategy is mostly adopted. 2e-i However, the direct synthesis suffered from poor yields in the key step sometimes, and most of all, this method is limited to the preparation of chiral homo-trisoxazolines with identical oxazoline subunits, as in the case of the synthesis of pseudo- C 3 -symmetric trisoxazoline 1a 5a…”

“…Another way is by modular synthesis, developed by Florio and Gade. Florio et al developed a novel tris(oxazolinyl)cyclopropane via “trimerization” of metalated 2-chloroalkyl-2-oxazolines. 2b,i Almost at the same time, Gade and co-workers reported the preparation of C 3 -symmetric trisoxazolines from bisoxazoline by addition−elimination reaction. 2c,k Very recently, to synthesize a chiral benzene-based hetero-trisoxazoline, Ahn et al described an oxazoline exchange reaction with amino alcohols 2a. The most promising character of these modular methods is to enable the synthesis of trisoxazolines with different oxazoline subunits, so that both chiral homo- and hetero-trisoxazolines can be synthesized at will.…”