A Conformationally Flexible Tetrahydroxycalix[4]arene Adopting the Unusual 1,3-Alternate Conformation

Abstract

The use of a chiral solvating agent enabled the determination of the NMR-silent ring-inversion process of the ketocalixarene 3. Spectroscopic and crystal data indicate that 3 adopts the unusual 1,3-alternate conformation.

Calix[6]arene Derivatives with Differently Modified Bridges

“…In this isomer, for a given enantiomer, the four stereocenters (the brominated carbons) possess identical configurations (i.e., either RRRR or SSSS ). In the crystal conformation, pairs or rings attached to a given carbonyl group adopt an anti arrangement (i.e., they are oriented in opposite directions: one “up” and one “down”), as previously observed in other ketocalixarene derivatives , …”

Semifield testing of a bioremediation tool for atrazine‐contaminated soils: Evaluating the efficacy on soil and aquatic compartments

“…It can therefore be expected that these keto‐bridged calixaromatics will have a smaller conformational space than the compounds discussed before. Based on the X‐ray structures reported by Görmar118 and more recently by Seri,119–121 ketocalixarenes in general are apt to adopt a 1,3‐alternate conformation from the X‐ray crystal structure, though none of the available studies focused on compounds 9 , 10 . Figure 6 shows the lowest‐energy conformations of these two compounds.…”

The robust, readily available cobalt(iii) trication [Co(NH2CHPhCHPhNH2)3]3+ is a progenitor of broadly applicable chirality and prochirality sensing agents

“… 77 Far fewer CSAs have been applied to prochirality sensing, and the eight functional groups represented in Table 3 exceed the sum of all those in the literature we have been able to locate. 48 – 54 …”