Highly diastereoselective functionalisation of calix[4]resorcinarene derivatives and acid catalysed epimerisation reactions

Gihani, M. T. El; Heaney, H.; Slawin, Alexandra M. Z.

doi:10.1016/0040-4039(95)00882-d

Cited by 20 publications

(10 citation statements)

References 25 publications

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“…This has inevitably meant that only very small amounts of optically pure material has been available for use in other studies. A solution to this problem was provided by studies carried out by us5a,5b and others,5c with the use of chiral nonracemic (α‐methylbenzyl)amines, and resulted in the highly diastereoselective formation of tetrabenzoxazines derived from a number of resorcin[4]arenes, for example the compounds 2 . The methylation of the residual phenolic hydroxy groups present in the single diastereoisomers was achieved in high yields on multigram scales in order to preclude diastereoisomerization as well as the loss of axial chirality after ring opening of the 1,3‐oxazine ring and removal of the chiral auxiliary 6a.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2006

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The preparation of a series of diastereoisomeric tetracamphorsulfonates derived from racemic tetramethoxyresorcin [4]arenes was achieved by reactions with an excess of (S)-(+)-10-camphorsulfonyl chloride in pyridine followed by isolation using flash chromatography. Tetradeprotonation of a number of tetramethoxyresorcin[4]arenes using n-butyllithium in tetrahydrofuran, followed by reactions using (S)-(+)-10-camphorsulfonyl chloride, gave the same tetracamphorsulfonates. Mono-, di-and tricamphorsulfonates were also prepared following selective deprotonation. In the reactions with tetraisopropyloxy-and tetracyclopentyloxyresorcin[4]arenes, only the mono-and dicamphorsulfonates were formed. X-ray crystallographic analysis established the absolute configurations of three diastereoisomerically pure tetracamphorsulfonates, including a diastereoisomer preparedThe chemistry of calixarenes is widely studied and has provided a diverse range of molecular assemblies that have been used for a variety of purposes; the topic continues to generate considerable interest.[1] The acid-catalysed interaction of aldehydes with resorcinol provides a high-yield route to a range of cyclic tetramers that has made the study of resorcin [4]arenes, for example 1, particularly attractive. [2] The dissymmetry generated by the unsymmetrical substitution of calixarenes is recognized as being related to the nonplanar structures of the parent compounds, [3a] although a number of chiral calixarene conformers are racemized thermally by processes involving "through-the-annulus rota- [a]

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Section: Methodsmentioning

confidence: 99%

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

et al. 2006

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“…This has inevitably only allowed for a very small amount of optically pure material to be available for use in other studies 9. An exception to this problem was provided by studies carried out by us,9a and others,9b,9c with the use of optically pure (α‐methylbenzyl)amines and formaldehyde. This reaction resulted in the highly diastereoselective formation of tetrabenzoxazines derived from a number of octahydroxyresorcin[4]arenes, for example 2a .…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2006

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The measurement of the pKa of racemic tetramethoxyresorcin[4]arenes explains the failure to obtain good yields in attempted Mannich reactions of these substrates under classical reaction conditions. The failure is related to the lack of adequate concentrations of the iminium ions that results from the reduced acid strength of tetraalkoxyresorcin[4]arenes compared with that of the parent octahydroxyresorcin[4]arenes. However, the preparation of a series of Mannich bases derived from racemic tetraalkoxyresorcin[4]arenes was accomplished under microwave‐assisted aprotic reaction conditions and the use of preformed iminium ion intermediates. When the reactions were carried out with the use of chiral bis(aminol) ethers, mixtures of diastereomers were obtained that could be separated by flash chromatography. The absolute configurations of the enantiomerically pure tetrabenzoxazine derivatives were established in some cases by X‐ray crystallographic analysis and by a comparison of the nuclear magnetic resonance spectroscopic data. The alkylation of racemic tetramethoxyresorcin[4]arenes was achieved with the use of an excess of 2‐bromo‐N‐[(R)‐(+)‐(α‐methylbenzyl)]acetamide in acetonitrile containing potassium carbonate. Enantioselective ligand‐assisted reactions of aromatic aldehydes are also reported with the use of dialkylzinc reagents both in the absence and in the presence of terminal alkynes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…Furthermore, to the best of our knowledge, there exist no structures of a resorcinarene tetrabenzoxazine containing long upper rim arms bonded to the benzoxazine nitrogen atom. The previous examples include short chain (hydroxyethyl group), different types of substituted rings, or unsubstituted ring bonded to the benzoxazine nitrogen atom via very short spacer . As in 1 , where upper rim arm snugly fits in the cavity of another tetrabenzoxazine molecule, yet the slightly elongated aliphatic oxalyl chain of 2 is twisted, as shown by the C50‐C51‐C52‐N53 and C250‐C251‐C252‐N253 torsion angles of 84.3(14) and 69.7(8)°.…”

Section: Resultsmentioning

confidence: 99%

Self‐Complementary Dimers of Oxalamide‐Functionalized Resorcinarene Tetrabenzoxazines

Džolić

Beyeh

Cetina

et al. 2017

Chemistry An Asian Journal

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Self-complementarity is a useful concept in supramolecular chemistry, molecular biology and polymeric systems. Two resorcinarene tetrabenzoxazines decorated with four oxalamide groups were synthesized and characterized. The oxalamide groups possessed self-complementary hydrogen bonding sites between the carbonyls and amide groups. The self-complementary nature of the oxalamide groups resulted in self-included dimeric assemblies. The hydrogen bonding interactions within the tetrabenzoxazines gave rise to the formation of dimers, which were confirmed by single-crystal X-ray diffractions analysis and supported by NMR spectroscopy and mass spectrometry. The self-included dimers were connected by numerous and strong intermolecular N-H⋅⋅⋅O and C-H⋅⋅⋅O hydrogen bonds supplemented with C-H⋅⋅⋅π interactions, forming one-dimensional polymers, which were then further linked into three-dimensional networks.

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Highly diastereoselective functionalisation of calix[4]resorcinarene derivatives and acid catalysed epimerisation reactions

Cited by 20 publications

References 25 publications

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

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

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

Self‐Complementary Dimers of Oxalamide‐Functionalized Resorcinarene Tetrabenzoxazines

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Highly diastereoselective functionalisation of calix[4]resorcinarene derivatives and acid catalysed epimerisation reactions

Cited by 20 publications

References 25 publications

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

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

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

Self‐Complementary Dimers of Oxalamide‐Functionalized Resorcinarene Tetrabenzoxazines

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

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