Aromatic macrocyclic compounds

Additionally to the theoretical data and synthetic techniques for various metal complexes presented in Chaps. 2-A, we would like to pay special attention to three kinds of coordination compounds (complexes of phthalocyanines, quinones, and radioactive elements), whose syntheses, in our opinion, have been insufficiently generalized in monographs and textbooks on synthetic coordination chemistry. This choice is caused by the facts that phthalocyanines, as n-aromatic macrocyclic compounds, possess unusual thermal stability (nonstandard for organic and organometallic species) the quinone complexes have free-radical properties and coordination and organometallic compounds of radioactive elements are interesting at least for the reasons of necessity of special precautions in their syntheses and applications in the nuclear industry and nuclear medicine. So, this chapter is dedicated to the peculiarities of structure and properties and the main synthetic procedures for the complexes above. 

Figure 26 Structures of some of the aromatic macrocyclic compounds used in nanotube formation.

Other commonly occurring chemical groups ia essential oils iaclude aromatics such as P-phenethyl alcohol, eugenol, vanillin, ben2aldehyde, cinnamaldehyde, etc heterocycHcs such as iadole (qv), pyra2iaes, thia2oles, etc hydrocarbons (Liaear, branched, saturated, or unsaturated) oxygenated compounds such as alcohols, acids, aldehydes, ketones, ethers and macrocyclic compounds such as the macrocyclic musks, which can be both saturated and unsaturated. 

The H NMR spectra of the compounds 273a and 274a as Bp4 salts appearing in equation 92 (Section VII.C.8), show die chemical shifts expected for the aromatic protons in the various types of aromatic systems present in these compounds ". NOESY of the macrocyclic compound 262 (equation 90, Section VII.C.3) points to interaction between the Me protons of the f-Bu groups and the remote methine protons. This is in accordance with the structure as determined from single crystal XRD of this compound ". ... 

Ansamycins are a class of macrocyclic compounds in which non-adjacent positions on an aromatic ring system are spanned by the long aliphatic bridge (Latin ansa = handle). The aromatic portion may be a substituted naphthalene or naphthaquinone, or alternatively a substituted benzene ring. The macrocycle in the ansamycins is closed by an amide rather than an ester linkage, i.e. ansamycins are lactams. The only ansamycins currently used therapeutically are semi-synthetic naphthalene-based macrocycles produced from rifamycin B. 

Although pure aliphatic compounds with a high persistent length are known, as for example [njstaffanes, shape-persistent macrocyclic compounds are dominated by structures with an aromatic backbone. 

The H chemical shifts of phthalocyanine and porphyrine complexes with hexacoordinate siliconas well as theoretical calculations of the contribution to H magnetic shieldingshow a high degree of aromatic nature of the macrocycle compounds of this type can even be used as diamagnetic shift reagents... 

Conversion of the non-aromatic macrocycles 4.147 and 4.148 into their respective aromatic salts was achieved (in 82% and 90% yield, respectively) via iron(III)-mediated oxidation, followed by treatment with perchloric acid. The designation of these compounds as aromatic was based upon H NMR experiments whereby, for instance, the maximum difference in the chemical shifts of the internal and external meso- i]f protons for 4.149 was determined to be 20.93 ppm (in DCO2D at room temperature). 

Several macrocyclic compounds have been prepared using Wittig reactions including tetraepoxyannulenes, which utilized the ylide derived from phos-phonium salt (57), and rotaxanes, molecules in which one or more macrocyclic components are trapped around a rod section of a dumbbell-shaped molecule, obtained by treating terephthaldehyde derivatives with dibenzylic bis(triphenyl-phosphonium)-stoppered [2]rotaxane (58). Aromatic triesters have been obtained by the (ethoxycarbonylmethylene)triphenylphosphorane-catalysedcyclo-trimerisation of ethyl propynoate. ... 

Topics that have formed the subjects of reviews this year include contemporary issues in electron transport research, dynamics of bimolecular photoelectron transfer reactions, photophysical properties of functionalised fullerene derivatives, carbon-carbon bond formation via radical ions, photoinduced electron transfer processes in ketone, aldehyde, and ester synthesis, photochemical reactions between arenenitriles and benzylic donors, photo-oxidation of conjugated dienes, photoredox reactions of aromatic nitro compounds, electron transfer-mediated photochemistry of some unsaturated nitrogen-containing compounds, reactions of 02( Ag), carbon dioxide activation by aza-macrocyclic complexes, and photochromism of chalcone derivatives. ... 

The aromatic Claisen rearrangement was employed in the synthesis of building blocks for various macrocyclic compounds, such as pendant-capped porphyrins , multidentate macrocycles containing 1,3,4-oxadiazole, imine and phenol subunits, as well as to prepare longithorone B, a sixteen-membered farnesylated para-benzoquinone . 

The metalloporphyrins as macrocyclic compounds have a few sites for specific and universal solvation and are able to axial coordination of some ligands. At the present time chemical modification of macrocycle is a main way of increasing of selectivity of molecular complex formation. The data obtained earlier [1,2] show that the selectivity may be increased due to specific %-% interactions of the metalloporphyrins with aromatic molecules. Aromatic molecules coplanar to the macrocycle will rise geometrical requirements to axial coordinating ligands. In particular, the results of the thermodynamic study of the axial coordination of n-propylamine by zinc(II) porphyrins in benzene have demonstrated the formation of the complexes of the metalloporphyrin containing both w-propylamine and benzene [2], The aim of this work is to study the molecular complexes of zinc (II) porphyrins prepared by slow crystallization from saturated solutions in benzene, w-propylamine and mixed solvent benzene - -propylamine. 

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