In this review we cover various approaches to meta- and paracyclophanes involving popular reactions Generally, we have included a strategy where the reaction was used for assembling the cyclophane skeleton for further functionalization In several instances, after the cyclophane is made several popular reactions are used and these are not covered here We included various natural products related to cyclophanes To keep the length of the review at a manageable level the literature related to orthocyclophanes was not included

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-11-142.pdf

Selected synthetic strategies to cyclophanes.

Numerous transition metal complexes of strained cyclophanes are known, including the metals Cr, Mo, W, Fe, Ru, Co, Rh, Ir, Ni, Cu, Ag and U. The complexed phanes turned out to be valuable subjects for NMR-examinations in order to draw a map of the magnetic environment of sandwich complexes, e.g. di(benzene)chromium and ferrocene, and they provided an insight into the effect of ring current disrupture, due to metal complexation. First attempts were carried out to derivatize the cyclophanes using the metal fragment as an auxiliary group, which is easily introduced as well as removed. In this context a tricarbonylchromium complex of a chiral [2.2]metacyclophane was prepared recently and its absolute configuration, containing two elements of chirality, was determined by X-ray crystallography. Complexation of the cyclophanes was also used for the purpose of the preparation of numerous novel phanes which were not yet available via other routes, e.g. syn-[2.2]metacyclophane, and phanes, which contain anti-aromatic π-decks and are only stable when complexed with the metal. Removing the stabilizing metal unit lead to valence isomerism, which gave interesting hydrocarbons, e.g. propella[34]prismane.

Transition metal complexes of (strained) cyclophanes

The chiroptical properties, such as electronic and vibrational circular dichroism and optical rotation, of planar chiral cyclophanes have attracted much attention in recent years. Although the chemistry of cyclophanes has been extensively explored for more than 60 years, the studies on chiral cyclophanes are rather limited. Experimentally, the use of chiral stationary phases in HPLC becomes more popular and facilitates the enantiomer separation of chiral cyclophanes of interest. Almost all chiral cyclophanes can be readily separated, in analytical and preparative scales, most typically on a Daicel OD type column, which is based on cellulose tris(3,5-dimethylphenylcarbamate). The CD spectra of chiral cyclophanes are unique in their fairly large, significantly coupled Cotton effects observed in all the 1 B b, 1 L a, and 1 L b band regions. Theoretically, the time-dependent density functional theory, or TD-DFT, method becomes a cost-efficient, yet accurate, theoretical method to reproduce the electronic circular dichroisms and the absorption spectra of a variety of cyclophanes. The direct comparison of the experimental CD spectra with the theoretical ones readily leads to the unambiguous assignment of the absolute configuration of cyclophanes. In addition, the analysis of configuration interaction and molecular orbitals allows detailed interpretation of the electronic transitions and Cotton effects in the UV and CD spectra. Through the study of the CD spectra of chiral cyclophanes as model systems, the effects of intra- and intermolecular interactions on the chiroptical properties of molecules can be explored, and the results thus obtained are valuable in comprehensively elucidating the structure-chiroptical property relationship. In this review the recent progress in experimental and theoretical investigations of the electronic CD spectra of chiral cyclophanes is discussed.

Recent theoretical and experimental advances in the electronic circular dichroisms of planar chiral cyclophanes.

8 – Arene and Heteroarene Complexes of Chromium, Molybdenum and Tungsten

Tricarbonylchromium complexes of [5]- and [6]metacyclophane: an experimental and theoretical study

Tricarbonylchromium Complexes of Chiral [2.2]Metacyclophanes: Syntheses, Structures, and Chiroptical Properties



HPLC-baseline separations of three racemic cyclophanes 3, 4, and 6 on cellulose tris(3,5-dimethylphenyl)carbamate led to their enantiomers with high optical purity. Complexation of (-)-3 and (+)-3 with triamminetricarbonylchromium yielded chiral Cr(CO)3 complexes (-)-(S)P-(3S)M-3a and (+)-(R)P-(3R)M-3a stereoselectively. Derivatisation of the complexes by lithiation and reaction with electrophiles gave new substituted chiral Cr(CO)3 complexes of [2.2]metacyclophanes regio-selectively. X-ray structure analyses of one chiral chromium complex (-)-(R)P-(5S)M-14a and three chiral chromium-free ligands (-)-(S)P-3, (-)-(S)P-4, and (-)-(S)P-6 led to the assignment of the absolute configurations of all chiral compounds discussed here. The influences of substituents on the chiroptical properties are investigated. The helicity of [2.2]metacyclophanes is discussed. For the first time X-ray structure analyses were performed of a bis-Cr(CO)3 complex (9a) as well as of the first chromium complex 10a of a heteraphane. Dethioketalisation of (-)-(S)P-3 with NBS gave (-)-(S)P-18, the absolute chirality of which has been known, under retention of configuration.

Tricarbonylchrom‐Komplexe von chiralen [2.2]Metacyclophanen: Darstellung, Struktur und chiroptische Eigenschaften

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Tricarbonylchrom‐Komplexe von chiralen [2.2]Metacyclophanen: Darstellung, Struktur und chiroptische Eigenschaften