Photochemical synthesis of [2.2](3,8)-pyridazinophane and quinolinophane-2(1H)-one as well as synthesis of [2](5,8)-quinolinophanes and fused spiro-pyranoindanoparacyclophanes

Syntheses of various classes of unreported heterophanes derived from [2.2]paracyclophane are herein reported. The key to their successful synthesis depends on the photochemical synthesis of pyridazinophane and quinolinophane-2(1H)-one from freshly prepared 4-([2.2]paracyclophanyl)-azo-4′-[2.2]paracyclophane and 4-([2.2]paracyclophanyl)cinnnamanilide, respectively. Reactions of 4-amino-[2.2]paracyclophane with either acetyl- or benzoylacetone afforded condensed products. Then ring closure using polyphosphoric acid (PPA) at 120°C gave, in near quantitative yields, quinolinophanes. Reactions of [2](4,7)-indano-[2]paracyclophane-1-ylidene-propanedinitrile with active methylene compounds afforded fused spiro-pyranoindanoparacyclophane derivatives.     

Stereoselective synthesis of homoallylic alcohols of the [2.2]paracyclophane series and their use as auxiliaries in asymmetric allylboration of aldehydes

Stereoselectivity of allylboration of 4-formyl[2.2]paracyclophane, 4-acetyl[2.2]paracyclophane, and 4-hydroxy-5-formyl[2.2]paracyclophane was studied and the relative configurations of the homoallylic alcohols obtained were established. Optically pure (Sp,Sc)-(+)-4-(4-hydroxy-1-methylbut-3-enyl)[2.2]paracyclophane and (Rc,Sc)-(+)-4-hydroxy-5-(4-hydroxybut-3-enyl)[2.2]paracyclophane were synthesized. The possibility of using (Sp,Sc)-(+)-4-(4-hydroxy-4-methylbut-3-enyl)[2.2]paracyclophane as a recoverable chiral auxiliary in asymmetric allylboration of aldehydes was demonstrated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–921, May, 2000.     

Novel ligands based on bromosubstituted hydroxycarbonyl [2.2]paracyclophane derivatives: synthesis and application in asymmetric catalysis

New planar-chiral hydroxycarbonyl [2.2]paracyclophane derivatives, 4-acetyl-13-bromo-5-hydroxy[2.2]paracyclophane (Br-АНРС, 63%) and 4-benzoyl-13-bromo-5-hydroxy[2.2]paracyclophane (Br-BHPC, 53%), were synthesized and reacted with the enantiomers of α-phenylethylamine to form corresponding Schiff bases, 12-bromo-4-hydroxy-5[1-(1-phenyl-ethylimino)-ethyl]-[2.2]paracyclophane and 12-bromo-4-hydroxy-5[1-(1-phenyl-ethylimino)-(phenyl)methylen-[2.2]paracyclophane. The diastereomers of the imines were resolved and their absolute configurations and consequently the corresponding configurations of the enantiomers of Br-АНРС were determined by X-ray diffraction. Enantiomerically pure Schiff bases were applied as ligands to form catalysts for the enantioselective addition reaction of diethylzinc with benzaldehyde where 1-phenylpropanol was obtained with 77–91% ee.     

Diastereoselective Hartwig-Buchwald reaction of chiral amines with rac-[2.2]paracyclophane derivatives

A Hartwig-Buchwald addition of a variety of chiral amines to rac-4-bromo-[2.2]paracyclophane and rac-trifluoromethanesulfonic acid (4-[2.2]paracyclophane) ester was performed with high diastereoselectivities. Kinetic racemic resolution of the starting materials was achieved, providing a rapid access to enantiomerically enriched 4-bromo-[2.2]paracyclophane and the corresponding enantiomerically pure [2.2]paracyclophane amines. Additionally, the first reaction of a secondary amine with a [2.2]paracyclophane halide was achieved.     

Synthesis of [2.2]paracyclophane-pseudo-ortho-dicarboxylic acid

An efficient three-step synthesis of [2.2]paracyclophane-pseudo-ortho-dicarboxylic acid by dibromination of [2.2]paracyclophane, thermal isomerization of the resultingpseudopara-dibromide topseudo-ortho-isomer, followed by lithiation/carboxylation was developed. The possibility of preparation of two other novelpseudo-ortho-disubstituted carbonyl derivatives, 4-carboxy-12-(1-oxopenthyl)-[2.2]paracyclophane and di(4-carboxy[2.2]paracyclophanyl-12)ketone, was demonstrated when an excess of lithiation reagent (4 or 10 eq.) was used in the final step. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2001–2004, November, 1997.     

Planar chiral hydroxy derivatives of [2.2]paracyclophane as auxiliaries for asymmetric allylboration

Allylboronic esters with various structures were synthesized for the first time based on [2.2]paracyclophane derivatives containing one or two hydroxy groups. It was demonstrated that these esters can be used as chiral inductors in the asymmetric allylboration of benzaldehyde. The highest enantiomeric excess of 1-phenylbut-3-en-1-ol (60%) was achieved in the reactions with acyclic bis-O,O′-(paracyclophanyl) allylboronates based on (S)-4-hydroxy-and (S)-12-bromo-4-hydroxy[2.2]paracyclophanes. (S)-4-Hydroxy[2.2]paracyclophane was studied by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2149–2155, November, 2007.     

Synthesis, characterization, and spectroscopy of 4,7,12,15-[2.2]paracyclophane containing donor and acceptor groups: impact of substitution patterns on through-space charge transfer

This paper reports the synthesis of 4,7,12,15-tetra(4'-dihexylaminostyryl)[2.2]paracyclophane (1), 4-(4'-dihexylaminostyryl)-7,12,15-tri(4' '-nitrostyryl)[2.2]paracyclophane (2), 4,7-bis(4'-dihexylaminostyryl)-12,15-bis(4' '-nitrostyryl)-[2.2]paracyclophane (3), 4,7,12-tris(4'-dihexylaminostyryl)-15-(4' '-nitrostyryl)[2.2]paracyclophane (4), 4,15-bis(4'-dihexylaminostyryl)-7,12-bis(4' '-nitrostyryl)[2.2]paracyclophane (5), and 4,12-bis(4'-dihexylaminostyryl)-7,15-bis(4' '-nitrostyryl)[2.2]paracyclophane (6). These molecules represent different combinations of bringing together distyrylbenzene chromophores containing donor and acceptor groups across a [2.2]paracyclophane (pCp) bridge. X-ray diffraction studies show that the lattice arrangements of 1 and 3 are considerably different from those of the parent chromophores 1,4-bis(4'dihexylaminostyryl)benzene (DD) and 1,4-di(4'-nitrostyryl)benzene (AA). Differences are brought about by the constraint by the pCp bridge and by virtue of chirality in the "paired" species. The absorption and emission spectra of 1-6 are also presented. Clear evidence of delocalization across the pCp structure is observed. Further, in the case of 2, 3, and 4, emission from the second excited state takes place.     

An improved synthesis of (S)-(+)- and (R)-(−)-4-ethenyl[2.2]paracyclophane

The resolution of the 4-acetyl[2.2]paracyclophane by the SAMP-hydrazone method is described. A new, short, high yield synthesis of both enantiomers (S)-(+)- and (R)-(−)-4-ethenyl[2.2]paracyclophane is reported.     

The first three aromatic tribromides of the [2.2]paracyclophane series

From the reaction mixtures in the uncatalyzed polybromination of [2.2]paracyclophane by the action of excess Br₂ in CCl₄, there have been found along with the known products — 4,15- and 4,16-dibromo[2.2]paracyclophanes — two new aromatic tribromides of this series, which have been isolated in pure form: 4,12,15- and 4,15,16-tribromo[2.2]paracyclophanes. Special experiments demonstrated that the mixtures of these tribromides are formed as a result of competitive monobromination of 4,15-dibromo[2.2]paracyclophane; the 4,15,16-tribromo[2.2]paracyclophane, together with still another newly isolated isomer of this series — 4,8,12-tribromo[2.2]paracyclophane — is formed as a result of competitive monobromination of 4,16-dibromo[2.2]paracyclophane. As an explanation of the features of the orienting effect of substituents in these competing reactions, a rule was proposed: On the conventional orientation (from the electronic point of view) of entry of the bromine atom into the substituted ring (para > ortho > meta), a steric limitation is imposed on its attack in the pseudo-gem-position, owing to the bulky bromine atom that is transannularly positioned above it in the neighboring aromatic ring. The structures of all of the tribromides were established on the basis of elemental analyses, mass spectrometry, and¹H NMR spectrometry (including PMR using the homonuclear Overhauser effect). The data obtained in this work indicate that the 4,12,15-tribromo[2.2]paracyclophane and 4,15,16-tribromo[2.2]paracyclophane are predecessors of the two tetrabromides previously obtained by Cram — 4,7,12,15- and 4,5,15,16-tetrabromo[2.2]paracyclophanes; and the 4,8,12-tribromo[2.2]paracyclophane is a possible predecessor of 4,8,12,16-tetrabromo[2.2]paracyclophane, which is unknown up to the present time.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1837–1843, August, 1992.     

New chiral β-diketones based on [2.2]paracyclophane

Two chiral β-diketones, 1,3-bis[(S)-(4-[2.2]paracyclophanyl)]propane-1,3-dione (BPPD) and [1-(S)-(4-[2.2]paracyclophanyl)-3-phenyl]propane-1,3-dione (PPPD), were synthesized by acylation of (S)-4-acetyl[2.2]paracyclophane with methyl esters from the corresponding carboxylic acids. 4-Acetyl[2.2]paracyclophane was synthesized in a quantitative yield by the reaction of [2.2]paracyclophane-4-carboxylic acid with methyllithium.     

Design and synthesis of planar chiral heterocyclic carbene precursors derived from [2.2]paracyclophane

A unique family of planar chiral symmetrical N-heterocyclic carbene precursors with restricted flexibility derived from [2.2]paracyclopane were obtained by a new synthetic route. The resolution of 4-amino-13-bromo[2.2]paracyclophane was achieved with relatively high efficiency. Starting from (4 S p,13 R p)-4-amino-13-bromo[2.2]paracyclophane, the planar chiral pseudogem-disubstituted [2.2]paracyclophanyl dihydroimidazoliums were prepared in a four-step sequence with good yields. The resulting dihydroimidazolium salts were fully characterized with a series of methods including single-crystal X-ray diffraction technique.     

Synthesis of novel mono- and diaryl-substituted [2.2]paracyclophanes

The cross-coupling reactions of 4-bromo[2.2]paracyclophane withp-tolylmagnesium bromide in the presence of various palladium and nickel complexes have been studied. It was found that [1,1 -bis(diphenylphosphinoferrocene)]palladium dichloride (PdCl₂ · dppf) shows the highest catalitic activity in this reaction. A series of new mono- and diaryl [2.2]paracyclophane derivatives with various substituents in the arene ring have been synthesized using this catalyst. It was shown that it is possible to cross-couple organozinc [2.2]paracyclophane derivatives with aromatic bromides. The composition and structure of the compounds obtained have been established on the basis of elemental analysis and spectral data. Some correlations between the structure and spectral parameters of mono- and diarylsubstituted [2.2]paracyclophanes have been found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1081–1085, June, 1994.The present work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-5246).The authors wish to express their gratitude to Prof. N. A. Bumagin for his scientific interest and helpful discussions.     

Transannular Hydrogen Bonding in Planar‐Chiral [2.2]Paracyclophane‐Bisamides

A series of [2.2]paracyclophane‐bisamide regioisomers and alkylated comparators were designed, synthesized, and characterized in order to better understand the transannular hydrogen bonding of [2.2]paracyclophane‐based molecular recognition units. X‐Ray crystallography shows that transannular hydrogen bonding is maintained in the solid‐state, but no stereospecific self‐recognition is observed. The assignment of both transannularly and intermolecularly hydrogen bonded N?H stretches could be made by infrared spectroscopy, and the effect of transannular hydrogen bonding on amide bond rotation dynamics is observed by ¹H‐NMR in nonpolar solvents. The consequences of transannular hydrogen bonding on the optical properties of [2.2]paracyclophane is observed by comparing alkylated and non‐alkylated pseudo‐ortho 4,12‐[2.2]paracyclophane‐bisamides. Finally, optical resolution of 4‐mono‐[2.2]paracyclophane and pseudo‐ortho 4,12‐[2.2]paracyclophane‐bisamides was achieved through the corresponding sulfinyl diastereoisomers for circular dichroism studies. Transannular hydrogen bonding in [2.2]paracyclophane‐amides allows preorganization for self‐complementary intermolecular assembly, but is weak enough to allow rapid rotation of the amides even in nonpolar solvents.     

Binuclear rhenium(I) complexes with bridging [2.2]paracyclophane-diimine ligands: probing electronic coupling through pi-pi interactions

Two pseudo-para substituted bis-diimino[2.2]paracyclophane ligands (4,16-bis(picolinaldimine)-[2.2]paracyclophane (BPPc) and 4,16-bis(methyl-picolinaldimine)-[2.2]paracyclophane (BmPPc)) were prepared by the condensation reaction of the appropriate picolinaldimine with 4,16-diamino-[2.2]paracyclophane (2). An improved synthesis of 2 from [2.2]paracyclophane also is reported. BPPc (3a): monoclinic, P2(1)/c, a = 8.2238(11) A, b = 15.336(2) A, c = 8.4532(11) A, beta = 98.578(3) degrees, V = 1054.2(2) A(3), Z = 2. To investigate the binding properties of the bis-diimino[2.2]paracyclophane ligands, binuclear rhenium(I) tricarbonyl chloride complexes [Re(CO)(3)Cl](2)(micro-BPPc) (5a) and [Re(CO)(3)Cl](2)(micro-BmPPc) (5b) were prepared and fully characterized by infrared spectroscopy, (1)H NMR spectroscopy, elemental analysis, UV-visible absorption spectroscopy, and cyclic voltammetry. Two model complexes, Re(tolyl-pyCa)(CO)(3)Cl (4) (tolyl-pyCa = N-(p-tolyl)-2-pyridinecarboxaldimine) and [Re(CO)(3)Cl](2)(micro-PBP) (6) (PBP = p-phenylenebis(picolinaldimine)), also are reported. The dimeric compounds 5 and 6 each undergo two one-electron, predominantly diimine-centered reduction processes. Spectroscopic data and comproportionation constants (5a, 23 +/- 9; 5b, 23 +/- 9; 6, 2750 +/- 540) are consistent with relatively weak interactions between the diimine groups mediated by the paracyclophane bridging group, and these results are consistent with steric and electronic factors.     

Water-soluble [2.2]paracyclophane chromophores with large two-photon action cross sections

A series of alpha,omega-donor-substituted distyrylbenzene dimers held together by the [2.2]paracyclophane core were designed, synthesized, and characterized. Different substituents were chosen to modulate the strength of the donor nitrogen groups and to allow the molecules to be either neutral and soluble in nonpolar organic solvents or charged and water-soluble. The specific neutral structures are (in order of decreasing donor strength) 4,7,12,15-tetra[N,N-bis(6' '-chlorohexyl)-4'-aminostyryl]-[2.2]paracyclophane (1N), 4,7,12,15-tetra[(N-(6' '-chlorohexyl)carbazol-3'-yl)vinyl]-[2.2]paracyclophane (2N), and 4,7,12,15-tetra[N,N-bis(4' '-(6' '-chlorohexyl)phenyl)-4'-aminostyryl]-[2.2]paracyclophane (3N). The charged species are 4,7,12,15-tetra[N,N-bis(6' '-(N,N,N-trimethylammonium)hexyl)-4'-aminostyryl]-[2.2]paracyclophane octaiodide (1C), 4,7,12,15-tetra[(N-(6' '-(N,N,N-trimethylammonium)hexyl)carbazol-3'-yl)vinyl]-[2.2]paracyclophane octaiodide (2C), and 4,7,12,15-tetra[N,N-bis(4' '-(6' '-(N,N,N-trimethylammonium)hexyl)phenyl)-4'-aminostyryl]-[2.2]paracyclophane octaiodide (3C). Two-photon excitation spectra, measured using the two-photon induced fluorescence technique, show in toluene the following trend for the two-photon cross sections (delta): 3N > 2N > 1N. In water the delta values follow the same order, 3C approximately 2C > 1C, but are smaller (approximately one-third). Significantly, the fluorescence quantum yield (eta) in water decreases much more for 1, relative to 2 and 3. The two-photon action cross sections (deltaeta) of 2C and 3C are 294 GM and 359 GM, respectively. These values are among the highest reported thus far. These results show that, to maximize the deltaeta in this class of chromophores, one needs to fine-tune the magnitude of the charge transfer character of the excited state, to minimize fluorescence quenching in polar media.     

The synthesis and directed ortho-lithiation of 4-tert-butylsulfinyl[2.2]paracyclophane

The ortho-lithiation of one diastereoisomer of 4-tert-butylsulfinyl[2.2]paracyclophane is the key step to the synthesis of a range of 4,5-disubstituted [2.2]paracyclophane derivatives.     

Structure Determination of an Unusual [2.2]paracyclophane Derivative by NMR Spectroscopy

Our ongoing study on cycloaddition reactions of dienes with different dienophiles afforded a great variety of derivatives with interesting molecular structures and electronic behavior. A new type of angularly annelated [2.2]paracyclophane (3) has been synthesize by the Diels–Alder reaction of 4-(2-propenyl[2.2]paracyclophane (1) and 1,4-benzoquinone (2) under high pressure conditions. The structure determination of this compound has been achieved by NMR measurements and semiempirical calculations.     

A novel class of bidentate ligands with a conformationally flexible biphenyl unit built into a planar chiral [2.2]paracyclophane backbone

We report the synthesis of a novel class of planar chiral bidentate aryl[2.2]paracyclophane ligands. For the first time in the [2.2]paracyclophanyl series the Pd-catalyzed Suzuki cross-coupling was employed for the formation of the arylparacyclophanyl skeleton. From the two possible approaches: (a) cross-coupling of [2.2]paracyalophanylboronic acids with aryl halides; (b) cross-coupling of [2.2]paracyclophanyl halides with arylboronic acids, the latter was found to be more efficient. This approach was successfully used for the synthesis of a wide range of aryl[2.2]paracyclophanes with different types of substitution patterns (ortho-, pseudo-ortho- or pseudo-gem-arrangement of the functionally-substituted aryl fragment with respect to the substituent in the paracyclophane ring).     

Synthesis of perfluoro[2.2]paracyclophane

A synthesis of perfluoro[2.2]paracyclophane has been sought ever since the partially fluorinated octafluoro[2.2]paracyclophane (AF4) was prepared and its chemistry studied. This compound has now been prepared in 39% yield from the precursor, 1,4-bis(chlorodifluoromethyl)-2,3,5,6-tetrafluorobenzene by its reaction with Zn when heated in acetonitrile at 100 degrees C. Two preparations of the precursor, first from 1,4-dicyano-2,3,5,6-tetrachlorobenzene and an improved method beginning from 1,2,4,5-tetrachlorobenzene, are also described as are key comparisons to our related synthesis of AF4.     

Suzuki aryl cross-coupling chemistry using derivatives of 1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane

An exploration into the scope of Suzuki aryl cross-coupling chemistry using derivatives of 1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane is reported. The coupling of 4-iodo-1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane with various aryl boronic acids and boronic acid pinacol esters was successful, with the exception of very sterically demanding systems, such as mesityl. The synthesis of the previously unreported 1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophanyl-4-boronic acid is described, together with various Suzuki aryl cross-coupling reactions of this new system. Using standard Suzuki methodology, it was possible to prepare dicyclophanes bearing two octafluoro[2.2]paracyclophane units separated by both one and two benzene rings.