Inherently Chiral Calixarenes: Synthesis, Optical Resolution, Chiral Recognition and Asymmetric Catalysis

Abstract

Inherently chiral calixarenes, whose chirality is based on the absence of a planar symmetry or an inversion center in the molecules as a whole through the asymmetric array of several achiral groups upon the three-dimensional calix-skeletons, are challenging and attractive chiral molecules, because of their potential in supramolecular chemistry. The synthesis and optical resolution of all varieties of inherently chiral calixarenes are systematically discussed and classified, and their applications in chiral recognition and asymmetric catalysis are thoroughly illustrated in this review.

Enantioselective complexation of 1‐phenylethanol with chiral compounds bearing urea moiety

“…After axially chiral and centrally chiral molecules, inherently chiral calix [4]arene [25][26][27][28][29] was chosen as the next type of chiral residue. The ureido derivative 6 (see Figure 10) was prepared from a pure enantiomer of 4-amino- 25,26,27,28-tetrapropoxycalix[4]arene by the condensation with 3,5-bis(trifluoromethyl)phenyl isocyanate.…”

Selective nitration of calix[4]arenes that easily gave inherently chiral calix[4]arenes

“…Therefore, by selective ipso-nitration, the resultant mononitrocalix [4]arene 2 and trinitrocalix [4]arene 4 would be inherently chiral calixarenes (Scheme 1), which would be one of the most concise methods for synthesis of this class of chiral calixarenes. However, while inherently chiral calixarenes usually exhibit excellent properties in chiral recognition, the synthesis of them is generally difficult and needs complex reaction route [25][26][27][28][29][30].…”

Qualitative Analysis of the Helical Electronic Energy of Inherently Chiral Calix[4]arenes: An Approach to Effectively Assign Their Absolute Configuration

“…Conformational inversion combined with functionalization at different positions can produce a variety of inherently chiral calixarenes [1,2,3,6]. It is known that there are two types of helices: the physical helix originated from asymmetric orbital twisting; and the geometrical helix originated from purely geometrical twisting, in many chiral molecules [29].…”

“…Although the first example of inherently chiral calixarene [7] appeared in 1982 and all varieties of them have been reported by now [1,2,3,6], only a few of them have been characterized by absolute configuration assignment, which seriously impedes their application in chiral recognition [8,9,10,11,12,13,14] and asymmetrical catalysis [10,11,15,16,17,18,19,20]. Therefore, the development of effective approaches for the absolute configuration assignment of inherently chiral calixarenes is of great importance.…”