Chiral Cyclophanes Research Articles

First asymmetric synthesis of planar chiral [2.2]metacyclophanes

A general three step asymmetric synthesis of planar chiral [2.2]metacyclophanes utilizing selective benzylic and aryl metalations is described. The final enantioselective step is achieved using a (-)-sparteine mediated aryl metalation, following which electrophile reaction gives planar chiral cyclophanes with enantiomeric ratios (er) above 90 : 10.

ChemInform Abstract: Recent Theoretical and Experimental Advances in the Electronic Circular Dichroisms of Planar Chiral Cyclophanes

AbstractReview: 63 refs.

ChemInform Abstract: A Novel Class of Neutral Chiral Cyclophanes from α,α′- Trehalose.

The synthesis and preliminary complexation studies of a new class of chiral cyclophanes 1–6, with properties comparable to cyclodextrins and cyclophanes, is described.

Planar chiral asymmetric naphthalenediimide cyclophanes: synthesis, characterization and tunable FRET properties

A series of planar chiral asymmetric naphthalenediimide (NDI) cyclophanes () consisting of two different NDIs interlinked by rigid meta-dimethylenebenzene spacers was synthesized. A modular synthetic strategy based on the dichloro cyclophane as common precursor gave a straightforward access to racemic mixtures of the NDI cyclophane dyes . In particular the substitution of both chlorine atoms of by tert-butylsulfanyl-, methoxy- and piperidinyl-groups provided racemic mixtures of the fluorescent NDI cyclophane dyes , and respectively. Fluorescence spectroscopy revealed chemically tuneable intramolecular FRET properties, as the spectral overlap between the emission of the unsubstituted NDI and the absorption of the core-substituted NDI subunit of the cyclophane could be adjusted by the core substituents. The racemic nature of the samples of cyclophanes , and in the case of the di-tert-butylsulfanyl functionalized cyclophane the enrichment of both enantiomers, was demonstrated by HPLC using a chiral stationary phase. The solid state structure of was determined by X-ray analysis. A periodic arrangement of both enantiomers of the planar chiral cyclophane in pillars such that NDI- and 2,6-core substituted NDI chromophores alternate periodically was observed.

Quantum Chemical Study on the Circular Dichroism Spectra and Specific Rotation of Donor−Acceptor Cyclophanes

The structures of donor,acceptor-substituted cyclophanes were optimized by DFT and MP2 methods and compared with the X-ray crystallographic structures. The electronic circular dichroism (CD) spectra of these chiral cyclophanes were simulated by time dependent density functional theory (TD-DFT) with several functionals including different amounts of "exact" Hartree-Fock exchange. The experimental oscillator and rotatory strengths were best reproduced by the BH-LYP/TZV2P method. The specific rotation and vibrational circular dichroism (VCD) spectra were also calculated at the BH-LYP/aug-cc-pVDZ and B3-LYP/6-31G(d) levels, respectively, and compared with the experimental data. Better performance was obtained with the ECD, rather than the specific rotation or the VCD spectral calculations in view of the computation time and accuracy for the determination of absolute configuration (AC). The exciton coupling model can be applied only for the cyclophanes without CT-character. However, the split pattern found in the experiment does not appear to originate from a simple two-transition coupling, indicating that this method should be applied with caution to the AC determination. This conclusion was supported by the TD-DFT investigations of the transition moments and the roles of excited-state electronic configuration associated with these split bands. Cyclophanes with donor-acceptor interactions showed Cotton effects at the CT band and couplets at the 1La and 1Lb bands. Although the degree of charge transfer between the rings is very small, as revealed by a Mulliken-Hash analysis, the split Cotton effects are due to a large separation in energy of the donor and acceptor orbitals. The effect of the distance and angle between the donor and acceptor moieties in model (intermolecular) CT complexes on the calculated CD spectra was also studied and compared with those obtained for various paracyclophanes.

Synthesis of annularly functionalised BINOL-based chiral cyclophanes

Chiral cyclophanes with annular functionality were synthesised by coupling carbonyl dibromides with ( S)-BINOL. Semi-empirical calculations by MOPAC (PM3) were also performed on the cyclophanes prepared to view their cavity sizes.

Allenophane and Allenoacetylenic Macrocycles: A New Class of Chiral Cyclophanes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF.

Allenophane and Allenoacetylenic Macrocycles: A New Class of Chiral Cyclophanes

Allenophane and Allenoacetylenic Macrocycles: A New Class of Chiral Cyclophanes

Synthesis of Chiral Macrocycles by Cyclodimerization of Diamines with Stepwise Nucleophilic Aromatic Substitution of 1,5-Difluoro-2,4-dinitrobenzene

Chiral cyclophanes were synthesized by cyclodimerization of 2,7-diaza-1,2,3,6,7,8-hexahydropyrene N-acylated with l-amino acids through stepwise nucleophilic aromatic substitution of 1,5-difluoro-2,4-dinitrobenzene.

Synthesis of a new class of electron rich chiral cyclophanes with large cavities

BINOL based electron rich chiral cyclophanes possessing large cavities have been synthesized starting from m-terphenyl dibromide and methyl m-/ p-cinnamate. The presence of double bonds in the chiral cyclophanes makes them electron rich as revealed by C–T complexation studies of such cyclophanes donors with guests like TCNE, TCNQ and DDQ.

Synthesis of an annularly linked bicyclic chiral cyclophane by pre-organization of a dibromide

An annularly linked bicyclic chiral cyclophane was synthesized from a suitable pre-organized chiral dibromide.

ChemInform Abstract: Synthesis of Chiral Cyclophanes Based on meta‐Terphenyl and Pyridyl Blocks.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of bicyclic cyclophanes with chiral cages by sixfold coupling

Coupling of (S)-binol with various tribromides afforded bicyclic cyclophanes by six fold coupling. Coupling of tricarbonyl tribromide with binol gave a novel chiral cyclophane with six co-ordination sites for complexation.

Synthesis of chiral cyclophanes based on meta-terphenyl and pyridyl blocks

Coupling of m-terphenyl dibromide with binol afforded the corresponding optically active cyclophane. Chiral cyclophanes were also obtained by the coupling of p-nitrophenol or 4,4″-bis(bromomethyl)-1,3-dibenzylbenzene with binol.

Synthesis, structure and AM1 conformational study of [3]paracyclo[3](1,3)indolophane, a novel chiral cyclophane

The title compound 5 was synthesized in seven steps with an overall yield of 22%. The two bridges were formed by a conjugate addition of indole to a Michael acceptor and by an intramolecular N-alkylation, respectively. A dynamic NMR study revealed the presence of a conformational process with an activation barrier of 10.9±0.2 kcal/mol, which was assigned to a ring flipping process that interconverts two enantiomeric sets of equilibrating bridge conformers. In the crystal structure of 5, both bridges adopt the pseudo-chair conformation, in accord with the lowest energy conformation identified by an AM1 conformational search.

Convenient Synthesis of Chiral Cyclophanes that Can Coordinate to Metals

Optically pure cyclophanes possessing a 1,3-dicarbonyl moiety were conveniently synthesized from alkanedioyl dichloride in four steps. The intramolecular [4+2]cycloaddition of bis(acylketene)s generated by thermal decomposition of bis(4,6-dioxo-1,3-dioxane) proceeded smoothly, giving cyclophane pyranones in high yields. The compounds possessing 7−10 bridging methylenes were resolved by imine formation with (R)-1-phenylethylamine, followed by basic hydrolysis. These cyclophanes are optically active versions of acetylacetone or salicylaldehyde and formed complexes with metals such as copper and europium. X-ray analysis of the chiral copper complex indicated the pentacoordinated structure of the copper metal with syn configuration of the two bridging chains.

Chiral Molecular Recognition in a Tripeptide Benzylviologen Cyclophane Host

A cationic chiral cyclophane was synthesized and studied as a host for chiral and racemic π-donor molecules. The cyclophane host has a rigid binding cavity flanked by (S)-(valine-leucine-alanine) and N,N‘-dibenzyl-4,4‘-bipyridinium subunits, which allow for hydrogen-bonding and π-stacking interactions with included aromatic guest molecules. 1H NMR binding titrations were performed with several different pharmaceutically interesting guest molecules including β-blockers, NSAIDs, and amino acids and amino acid derivatives. The host−guest complexation constants were generally small for neutral and cationic guests (0−39 M-1 at 20 °C in water/acetone mixtures). However, a (R)/(S) enantioselectivity ratio of 13 ± 5 was found for DOPA, a strongly π-donating cationic guest. Two-dimensional NOESY 1H NMR spectra confirm that (R)-DOPA binds inside the cavity of the host and that there is no measurable interaction of the cavity with (S)-DOPA under the same conditions.

ChemInform Abstract: New Optically Active Diporphyrin Having a Chiral Cyclophane as a Spacer.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

New optically active diporphyrin having a chiral cyclophane as a spacer

Optically active dimeric porphyrin covalently linked by a chiral cyclophane was synthesized; the two porphyrin chromophores were disposed in a slipped cofacial fashion, which was found to be tunable by cooperative coordination of diamines with various chain lengths.

New Optically Active Diporphyrin Having a Chiral Cyclophane as a Spacer

Abstract Optically active dimeric porphyrin covalently linked by a chiral cyclophane was synthesized; the two porphyrin chromophores were disposed in a slipped cofacial fashion, which was found to be tunable by cooperative coordination of diamines with various chain lengths.