Syntheses and reactions of some new dithia[3.1.3.1 ]paracyclophanes and [2.1.2.1] paracyclophanes

The syntheses of new dithia[3.1.3.1]paracyclophanes and [2.1.2.1] paracyclophanes are presented and their NMR spectroscopic properties are described. The possibility to synthesize new twin paracyclophanes by intramolecular coupling reactions of these cyclophanes is discussed.     

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).     

Tetracyanoresorcin[4]arene ion channel shows pH dependent conductivity change

A pH sensitive artificial ion channel, tetracyanoresorcin[4]arene, whose pK(a1) to pK(a3) are around pH 7, was synthesized. Conductivities for potassium ion were increased by the progress of dissociation at the channel mouth.     

Intramolecular reactions in pseudo-geminally substituted [2.2]paracyclophanes

A selection of pseudo-geminally substituted [2.2]paracyclophanes, the alkynes 6, 7, 10, 11 a, and 11 b and the alkenes 8 and 9 were prepared for the study of intraannular reactions between functional groups in direct juxtaposition. Whereas 9 and 10 provide the corresponding cyclobutane and cyclobutene derivatives on irradiation (12 and 13, respectively), the bis-alkynes 7 and 11 b do not lead to a cyclobutadiene intermediate. In the latter case the "half-closed" butadiene derivative 17 was isolated. A Paterno-Büchi reaction took place on irradiation of 8 and 6, although the oxetene intermediate 21 produced in the second example did not survive the reaction conditions (ring-opening to 22). Bromine addition to 9, 10, and 7 occurred with high stereoselectivity (formation of the dibromides 27, 30, and 33, respectively), and is rationalized by postulating the formation of the cationic intermediates 26, 29, and 32, respectively. To study the interaction of a carbocation with a facing triple bond, the alcohol 34 was prepared from 6. On acid treatment ring closure to the triply-bridged phane 38 took place, accompanied by the hydration of the triple bond to the ketoalcohol 37. In an interesting intraannular [2+3]cycloaddition reaction the bis-acetylene 11 a, on treatment with n-butyl lithium, provided the cyclopentadiene derivative 42. That the two triple bonds of a pseudo-geminal diacetylene can engage in a cyclization reaction leading to the cyclopentadienone complex 44 was also shown by treating 11 b with iron pentacarbonyl.     

Carbon-13 substituent chemical shifts of 4-substituted bicyclo[2.2.2]oct-1-yl cyanides

The carbon-13 substituent chemical shifts of 4-substituted bicyclo[2.2.2]oct-1-yl cyanides are a linear function of the substituent inductive parameters.     

Synthesis of o-benzoquinones derived from [2.2]- and [3.3]paracyclophanes

Oxidation of [2.2]- and [3.3]paracyclophanols with benzeneseleninic anhydride readily afforded the corresponding cyclophane-o-quinones which showed the intramolecular charge-transfer interactions.     

Stereoselective synthesis of enantiopure condensed [2.2]paracyclophanes

The Diels–Alder reaction of (S)-(+)-4-ethenyl[2.2]paracyclophane with 1,4-benzoquinone, N-phenylmaleimide and 3-nitrocyclohexen-1-one has been investigated under atmospheric and high pressure conditions. The synthesis of five optically active [2.2]paracyclophanes containing condensed polycyclic aromatic subunits is described. A structural analysis of the reaction products by ¹H and ¹³C NMR spectroscopy is also presented.     

Correlated flipping of four benzene rings in substituted [2.2.2.2]Paracyclophanetetraenes

Dynamic NMR spectroscopy and molecular mechanics calculations show that the flipping of the four benzene binge in certain substituted [2.2.2.2]paracyclophanetetraenes occurs in a correlated fashion.     

Syntheses and applications of disubstituted [2.2]paracyclophanes

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Electrochemical study of some bromo-substituted [2.2]paracyclophanes

The potentials of electrochemical oxidation ( ) and reduction ( ) of monobromo- and isomeric di- and tribromo[2.2]paracyclophanes as well as of mono-, di-, and tribromobenzenes were measured in acetonitrile. The similarity between the properties ofpseudo-para-disubstituted cyclophanes andmeta-disubstituted benzenes, on the one hand, andpseudo-meta-disubstituted cyclophanes andpara-disubstituted benzenes, on the other hand, was confirmed by the existence of a linear relationship between of bromo-substituted [2.2]paracyclophanes and of the corresponding bromo-substituted benzenes. The results were explained in terms of the qualitative theory of molecular orbitals, taking into account a through space interaction between the -systems of the benzene rings.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 839–845, May, 1994.The authors wish to express their gratitude to Professor R. Hoffmann (Cornell University, USA) for a useful discussion and criticisms of the text of this paper.This work was financially supported by the Russian Foundation for Basic Research (Project 93-03-5246).     

Asymmetric autocatalysis induced by chiral hydrocarbon [2.2]paracyclophanes

Chiral hydrocarbon [2.2]paracyclophanes act as chiral initiators in asymmetric autocatalysis in the addition of diisopropylzinc to pyrimidine-5-carbaldehyde and give highly enantiomerically enriched 5-pyrimidyl alkanol with a reversed sense of the enantioselectivity to that of other [2.2]paracyclophanes with heteroatoms.     

Regiodirected substitution of [2.2]paracyclophanedienes and [2.2]paracyclophanes through tricarbonylchronium complexation

4,7-dialkoxy[2.2]paracyclophanes and the corresponding 1,9-dienes are shown to undergo selective conplexation with Cr(CO)₃L₃-reagent on their less substituted benzene moiety. Lithiation/silytion of these complexes leads to arene- or bridge-substitution, respectively. An analagous behaviour is observed for the tricarbonylchromium[2.2]paracyclophane and its 1,9-diene.