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In organic chemistry, a cyclophane is a hydrocarbon consisting of an aromatic unit (typically a benzene ring) and a Catenation that forms a bridge between two non-adjacent positions of the aromatic ring. More complex derivatives with multiple aromatic units and bridges forming cagelike structures are also known. Cyclophanes are well-studied examples of strained organic compounds. (2025). 9783527603961, Wiley-VCH. ISBN 9783527603961
A non-bonding nitrogen to arene distance of 244 pm is recorded for a pyridinophane and in the unusual superphane the two benzene rings are separated by a mere 262 pm. Other representative of this group are in-methylcyclophanes, in-ketocyclophanes and in, in-Bis(hydrosilane).
Metacyclophanes are generally less strained and thus more easily prepared than paracyclophanes. Shown below is the route to a 1414metaparacyclophane in scheme 4Scheme 4. Reaction scheme: with para-ring in place ring closure of meta part by nucleophilic displacement of alkyl halide by sulfide. Then oxidation of sulfide to sulfone by hydrogen peroxide followed by in-situ Ramberg-Bäcklund Reaction with halide donor dibromodifluoromethane and base potassium hydroxide. Final step hydrogenation of alkene by hydrogen and palladium on carbon featuring a in-situ Ramberg-Bäcklund Reaction converting the sulfone 3 to the alkene 4.
Haouamine A is a paracyclophane found in a certain species of tunicate. Because of its potential application as an anticancer drug it is also available from total synthesis via an alkyne - pyrone Diels-Alder reaction in the crucial step with expulsion of carbon dioxide ( scheme 5). The authors mark the biosynthetic origin as mysterious
In this compound the deviation from planarity is 13° for the benzene ring and 17° for the bridgehead carbons. An alternative cyclophane formation strategy in scheme 6Scheme 6. Reaction scheme: step I elimination reaction of methanol with trifluoroethanol and diisopropylamine, step II methylation with dimethyl sulfate. Ns = Nosylate was developed based on aromatization of the ring well after the formation of the bridge.
Two additional types of cyclophanes were discovered in nature when they were isolated from two species of cyanobacteria from the family Nostocacae. These two classes of cyclophanes are both 7,7 paracyclophanes and were named after the species from which they were extracted: cylindrocyclophanes from Cylindrospermum lichenforme and nostocyclophanes from Nostoc linckia.
The 2.2paracyclophane-1,9-diene has been applied in ROMP to a poly(p-phenylene vinylene) with alternating cis-alkene and trans-alkene bonds using Grubbs' second generation catalyst:
The driving force for ring-opening and polymerization is strain relief. The reaction is believed to be a living polymerization due to the lack of competing reactions.
Because the two benzene rings are in close proximity this cyclophane type also serves as guinea pig for photochemical dimerization reactions as illustrated by this example:
The product formed has an octahedrane skeleton. When the amine group is replaced by a methylene group no reaction takes place: the dimerization requires through-bond overlap between the aromatic and the sigma bond in the C-N bond in the reactants LUMO.
Various synthetic methods for producing janusene have been developed since the original cycloaddition reaction was discovered, including microwave assisted reactions and acetylene transfer from 5,6,7,8-tetrafluorobenzobarrelene.
In "1(1,3)-benzenacyclopentadecaphane", the "1" refers to the first position of the ring as a "superatom", the "(1,3)" describes the "meta" location, "benzena" refers to the ring, and the "pentadeca" (15) describes the chain length counting the ring as one atom.
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