Nitrosonium complexes of [2.2]paracyclophane

The reaction of [2.2]paracyclophane with nitrosonium tetrachloroaluminate was studied by NMR (¹H, ¹³C) spectroscopy using deuterium isotopic perturbation technique. The resulting cationic complexes containing one and two nitrosonium ions are involved in fast (on the NMR time scale) interconversion. Quantum-chemical calculations performed on the DFT level (using triple zeta basis set) indicate the higher stability of 2η single-charged π-complexes relative to σ complexes corresponding to the addition of NO⁺ ion at the ipso and ortho positions. The formation of the single-charged π-complex is energetically more favorable, compared to the double-charged π-complex. The affinity of NO⁺ for [2.2]paracyclophane is much greater than for p-xylene, presumably due to stacking interaction between the aromatic rings in the π-complex.     

Porphyrin system containing [2.2]paracyclophane units

Meso-tetrakis([2.2]paracyclophanyl)porphyrin was obtained from [2.2]paracyclophanecarbaldehyde and pyrrole. Replacement of phenyl groups in meso-tetraphenylporphyrin by paracyclophanyl substituents remarkably influences the electronic structure of the molecule, causing bathochromic shifts of all uv-vis absorption bands, and changing the ring current of the porphyrin core. The shifts in the electron spectrum are substantially greater than those observed for other porphyrin derivatives characterized by their extended π-electron systems, such as meso-tetrakis(2-phenylethenyl)porphyrin and meso-tetrakisbiphenylporphyrin.     

Novel iron complexes of [2.2]paracyclophane

The synthesis of [2.2]paracyclophane-iron complexes $\text{4}$ (R=H or Me) is described.     

Molecular structure of 4,15-dibromo[2.2]paracyclophane

An x-ray structural study has shown that the nature of the steric distortions in [2,2]paracyclophane remains practically unchanged when Br-substituents are introduced into positions 4 and 15.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 588–590, March, 1990.     

A preparative microwave method for the isomerisation of 4,16-dibromo[2.2]paracyclophane into 4,12-dibromo[2.2]paracyclophane

4,16-Dibromo[2.2]paracyclophane (4) is isomerised to 4,12-dibromo[2.2]paracyclophane (1) by the application of microwaves in DMF solution.     

Atropisomerism of a monosubstituted perfluoro[2.2]paracyclophane. A combined synthetic, kinetic, spectroscopic and computational study

The product of S(N)Ar addition of the enolate of ethyl acetoacetate to perfluoro[2.2]para-cyclophane exists entirely as its enol tautomer 5. This enol exhibits two NMR signals for its enolic proton, and these signals were shown to derive from the presence of two, equal energy conformations that were observable as distinct, stable conformations at room temperature, but which when heated, interconverted with an energy barrier of 23.5 kcal mol(-1). These atropisomers were characterized by NMR, with details of this analysis being provided. Computational work corroborated the NMR conclusions, and provided additional insight into all structural, thermodynamic and kinetic results. Enol product 5 was cyclized, under basic conditions, to form a benzofuran product 6. Its structure was confirmed by NMR, with further structural and mechanistic insights being provided by calculations.     

Ethynyl[2.2]paracyclophanes and 4-isocyano[2.2]paracyclophane as ligands in organometallic chemistry

An alternative synthesis of (±)-4-ethynyl[2.2]paracyclophane (PCPCCH) (5) and 4,16-diethynyl[2.2]paracyclophane (6) via the Corey-Fuchs reaction has been developed. The olefinic intermediate 4-dibromovinyl[2.2]paracyclophane (3) has been isolated and structurally characterized. The racemic terminal alkyne 5 was employed as starting material for assembling of a luminescent extended π-conjugated system containing a thiophene unit and for a catalytic bis-silylation reaction yielding the olefinic dithioether Z-PhSCH₂Me₂SiC(H)C(PCP)SiMe₂CH₂SPh (9). The dimetallatetrahedran [Co₂(CO)₆(μ-η²-PCP-CCH)] (10) has been prepared and its crystal structure determined by an X-ray diffraction analysis. Alkyne 5 has also been used for the preparation of the Pt(0) complex [Pt(PPh₃)₂(PCPCCH)] (11) and the heterodinuclear dimetallacyclopentenone [(OC)₂Fe{μC(O)C(PCP)C(H)}(μ-dppm)Pt(PPh₃)] (12). The synthesis and reactivity of 4-isocyano[2.2]paracyclophane (15) towards heterobimetallic iron-platinum and palladium-platinum complexes is also presented. Opening of the dative iron → platinum bond of [(OC)₄Fe(μ-dppm)PtCl₂] (16) occurred upon addition of 15 to a CH₂Cl₂ solution of 16 leading to [(OC)₄Fe{μ-dppm}PtCl₂(CNPCP)] (17). Treatment of [ClPd(μ-dppm)₂PtCl] (18) with isocyanide 15 in a 1:1 ratio affords the A-frame compound [ClPd(μ-dppm)₂(μ-CNPCP)PtCl] (19), resulting from formal insertion of 15 into the Pd-Pt bond. Addition of 2 equiv. of 15-18 leads to the ionic A-frame compound [ClPd(μ-dppm)₂(μ-CNPCP)Pt(CNPCP)]Cl (20).     

Phane properties of [2.2]paracyclophane/dehydrobenzoannulene hybrids

A series of [2.2]paracyclophane/dehydrobenzo[14]annulene (PC/DBA) hybrids (hydrocarbons 5, 6, 9, 10 b, and 10 c), [2.2]paracyclophane/dehydro[14]annulene (PC/DA) hybrids (7 and 8) and suitable model systems (11, 12, and 33) has been synthesized. Comparison of the electronic absorption spectra in each series of compounds provides further insight into the global communication between the decks in the [2.2]paracyclophane unit.     

Cyclophane,XIV : darstellung polymethylierter [2.2]paracyclophane

Starting from 4, 5, 12, 13-tetrakis(methoxycarbonyl)[2.2]paracyclophane ($\text{1}$), the penta-($\text{4}$), hexa-($\text{6a}$–$\text{c}$), hepta-($\text{7}$), and octamethyl-($\text{8}$) derivatives have been prepared by a repetitive formylation-reduction sequence.     

Vapor deposition polymerization of heteroatom-bridged [2.2]paracyclophanes: 1,9-dithia[2.2]paracyclophane and 1,9-dithia[2.2]paracyclophane-1,1,9,9-tetroxide

1,9-Dithia[2.2]paracyclophane-1,1,9,9-tetroxide ( 3 ) was synthesized as white needles in a high yield from 1,9-dithia[2.2]paracyclophane ( 2 ) by oxidation with m-chloroperbenzoic acid, and its molecular structure was determined with single-crystal X-ray diffraction analysis. Vapor deposition polymerizations of 2 and 3 gave amorphous and brittle polymer films along with considerable amounts of nonpolymeric byproducts. A polymer film from 2 was a copolymer of p-(phenylene-methylenesulfide) with p-(phenylene-methylene) units, and a polymer film from 3 was a homopolymer of p-(phenylene-methylene) units with head-to-tail, head-to-head, and tail-to-tail placements. The elimination of sulfur atoms in 2 and sulfone units in 3 took place during their pyrolysis reactions. Plausible mechanisms for vapor deposition polymerizations of both cyclophanes are proposed. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1892–1900, 2001     

Dimeric Radical Cation of 4,5,7,8-Tetramethyl[2.2]paracyclophane

Electrolytic oxidation of 4,5,7,8-tetramethyl[2.2]paracyclophane (I) yields a paramagnetic species which by ESR. spectroscopic evidence must be ascribed to the dimeric radical cation I₂ · ⊕. Analogous dimers are obtained from the 12, 13, 15, 16-tetradeuterio- and 1, 1, 10, 10, 12, 13, 15, 16-octadeuterio-derivatives of I so that all coupling constants can be unequivocally assigned to sets of equivalent protons. The hyperfine data for I₂ · ⊕ are consistent with an effective D_2h or D_2d symmetry, the four benzene rings lying in parallel planes.     

The synthesis of enantiomerically pure [2.2]paracyclophane derivatives

[2.2]Paracyclophane is a fascinating molecule that offers great potential in a wide range of chemical disciplines. Currently, the synthesis of the majority of enantiomerically pure [2.2]paracyclophane derivatives is based on the resolution of a small number of starting materials or individual resolution procedures are developed for each new compound. The development of more general routes to these valuable compounds via the resolution of a common intermediate is discussed. Ultimately, it would be preferable to synthesise these valuable compounds without recourse to resolution and ideas for this rewarding goal are postulated.     

Synthesis of 1,1,9,9-tetrafluoro[2.2]paracyclophane and its polymerization by vapor deposition method

1,1,9,9-Tetrafluoro[2.2]paracyclophane ( 1 ) was prepared successfully as white crystals in 72% yield via two-step reactions from 1,9-diketo[2.2]-paracyclophane. The polymerization of 1 by the vapor deposition method was carried out at pyrolysis temperature range of 400 to 800°C and deposition temperature range of ?20 to 20°C, and a tough, transparent poly(α,α-difluoro-p-xylylene) film was obtained in 72% yield at the pyrolysis temperature of 750°C and the deposition temperature of ?20°C. It was found that the pyrolysis of 1 gave a reactive α,α-difluoro-p-xylylene, which polymerized on the head-to-tail addition to give poly(α,α-difluoro-p-xylylene). Some properties such as solubility, thermal stability, glass transition temperature, and density for poly(α,α-difluoro-p-xylylene) were studied. © 1995 John Wiley & Sons, Inc.     

Synthesis of planar chiral [2.2]paracyclophane Schiff bases for the enantioselective Henry reaction

A series of diastereomerically pure Schiff base ligands based on [2.2]paracyclophane backbones were synthesized and separated. The new planar chiral [2.2]paracyclophane Schiff bases were used as ligands in Cu-catalyzed asymmetric Henry reactions with high yields and enantioselectivities.