Determination of the Absolute Configuration of Inherently Chiral Resorc[4]arenes

Abstract

The absolute configuration of twelve inherently chiral resorc‐arenes was determined using a combination of the X‐ray structure of (–)‐3a and optical rotation as well as NMR techniques. Starting from a racemic mixture of 1 both diastereomers (–)‐3a and (+)‐3b can be obtained in high yields in two steps and the absolute configuration of these diastereomers could be determined by X‐ray analysis. Using enantiomerically pure (–)‐1 for the same reactions, however, (+)‐3b is formed. The alkylation of (–)‐1 with (S)‐2‐methylbutyl tosylate and the methylation of (–)‐5a lead to the same resorcarene (–)‐4a, while the alkylation of (+)‐1 and the methylation of (+)‐5b yield in resorcarene (+)‐4b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The Preparation and Absolute Configurations of Enantiomerically Pure C4‐Symmetric Tetraalkoxyresorcin[4]arenes Obtained from Camphorsulfonate Derivatives

“…The Loughborough group also prepared and used the racemic mixture of resorcin[4]arenes 7 in order to prepare tetracamphorsulfonates also with the use of ( S )‐(+)‐10‐camphorsulfonyl chloride. A very recent publication10 also used the absolute configurations that were reported earlier 9. The Bielefeld group repeated the experiments with an enantiomerically pure sample of compound 7 ,11 that involved the formation of a crystalline amide: those results confirmed the initial results of the Loughborough and Curtin groups.…”

“…The absolute configurations of the enantiomeric tetraalkoxyresorcin[4]arenes could also be established by reference to the known absolute configurations of chiral nonracemic tetrabenzoxazines such as the compounds 5 and 6 , whose structures were known from X‐ray crystallographic data 6b. When the study, conducted at Loughborough and Curtin, including the determination of the absolute configurations of a number of camphorsulfonates derived from racemic tetraalkoxyresorcin[4]arenes and their hydrolysis products, was almost ready for publication, the absolute configurations of the tetramethoxyresorcinarenes 7 derived from 3‐methylbutanal and 3‐methoxyphenol were published 9. The Loughborough and Curtin groups were surprised that the results of their study were not in agreement with the published results, and the Loughborough group therefore repeated their experiments.…”

Mannich and O‐Alkylation Reactions of Tetraalkoxyresorcin[4]arenes – The Use of Some Products in Ligand‐Assisted Reactions

“…The absolute stereochemistry of compound ( M , R , R )‐ 20a was established by single‐crystal X‐ray structure determination, shown in Figure 8 41. After this part of the study had been completed, the successful aminolysis of a compound related to 18 was reported in which the reaction of an esterwas heated with ( S )‐(–)‐(α‐methylbenzyl)amine at 160 °C 37b,42…”

Enthalpies of solution of C-alkylresorcin[4]arenes in alcohols at T= 298.15 K

“…The C-alkylresorcin [4]arenes are capable of forming solvates with the recrystallized solvent and several studies have reported the presence of these solvates [8,18,[22][23][24][25]. In the present work, the formation of solvates was avoided using vacuum techniques and high temperatures, as was mentioned in Section 2.1.…”