Macrocyclic cyclophanes

There is a close relationship between polycyclic compounds such as coronene 81198) or Staab s kekulene 82199) and the macrocyclic cyclophanes such as 83200). They can be described as perimeter structures in which an outer and inner perimeter can be considered. 

Cory RM, McPhail CL (1996) Transformations of a macrocyclic cyclophane belt into advanced [8]cyclacene and [Sjcyclacene triquinone precursors. Tetrahedron Lett 37(12) 1987-1990... 

The typical examples of macrocyclic cyclophanes, e.g., cyclotriver-atrylene, cyclotricatechylene, or tri-O-thymotide, form clathrate compounds. Significant host-host interaction affords a cage or a channel between the host molecules for guest accomodation in these lattice (cavity) inclusion crystals, (Host) (Guest). ... 

The first examples reported of totally synthetic uncharged host-uncharged guest intramolecular inclusion complexes elucidated by x-ray crystal structures were the calixarenes (125,126). This class of macrocyclic cyclophanes contains phenolic residues in a cyclic array linked by methylene groups all ortho to the hydroxy groups (Figure 2.53). 

Related macrocyclic cyclophanes synthesized by Tabushi (143, 144) utilize quaternary ammonium (145) (141) and sulphonium groups (156) (144) for their solubility as host molecules in water (Figure 2.63). 

Bisbenzylisoquinoline alkaloids form a large group (>150) of naturally occurring compounds in which two benzylisoquinoline moieties are joined by up to three ether links. Many of them have macrocyclic cyclophane-type structures, which makes them potentially capable of forming inclusion compounds with small guests. In addition, they have several stereogenic centers and may be useful... 

These topics are discussed in more detail in other chapters of this text. Formally, the pyrolytic elimination of sulphur dioxide from a sulphone, with the concomitant formation of a new carbon-carbon bond, constitutes a reduction at sulphur. These reductions have been valuable in the formation of new molecules, especially macrocycles and cyclophanes, and have been reviewed by Vogtle and Rossa205. Pyrolytic elimination of sulphur dioxide has been used by Julia and co workers in the formation of mixtures of isoprenoids206, and by Takayama and collaborators in the stereoselective synthesis of vitamin D, 19-alkanoic acids207. 

The penultimate example of macrocycles based on phenyl and acetylenic units has been the very recent report by Tobe [801 and Rubin [81] of cyclophane 134. Both groups generated 134 in the mass spectrometer by laser desorption of hexa-protected polyynes 135 (robust) and 136 (unstable), respectively (Scheme 31). 

Template effects have been used in rotaxane synthesis to direct threading of the axle through the wheel. Since macrocycHc compounds such as cyclodextrins, crown ethers, cyclophanes, and cucurbiturils form stable complexes with specific guest molecules, they have been widely used in the templated synthesis of rotax-anes as ring (wheel) components. Here, we briefly discuss macrocycles used in the synthesis of rotaxane dendrimers and their important features. 

MacrocycHc isophthalamides (the tetralactam macrocycles) have been used as a host to build rotaxanes and catenanes by Vogtle and others [15]. Structurally analogous to cyclophanes, their initial usage as a synthetic receptor was for... 

Several silver(I) complexes of the macrocyclic Schiff base derived from the [2+2] condensation of terephthalaldehyde and 3-azapentane-1,5-diamine or A,A -bis(3-aminopropyl)methylamine have been described.509,510 The reaction of 2,ll-diaza-difluoro-m-[3,3]-cyclophane with 2,6-bis (bromomethyl)pyridine lead to the 3 + 3 addition product, which gives a complex with two silver... 

With these features in mind, we envisioned a new family of macrocyclic ligands for olefin polymerization catalysis (Fig. 9) [131, 132], We utilized macrocycles as the ligand framework and installed the catalytic metal center in the core of the macrocycles. Appropriate intra-annular binding sites are introduced into cyclophane framework that not only match the coordination geometry of a chosen metal but also provide the appropriate electronic donation to metal center. The cyclophane framework would provide a microenvironment to shield the catalytic center from all angles, but leaving two cis coordination sites open in the front one for monomer coordination and the other for the growing polymer chain. This could potentially protect the catalytic center and prevent it from decomposition or vulnerable side reactions. 

Significant progress has been made in the synthesis and study of TTF-containing cyclophanes and macrocycles <00S824, OOEJOC2135, 99CHE795, 00JOC4120,... 

Macrocycles containing isoxazoline or isoxazole ring systems, potential receptors in host—guest chemistry, have been prepared by multiple (double, triple or quadruple) 1,3-dipolar cycloadditions of nitrile oxides, (prepared in situ from hydroxamoyl chlorides) to bifunctional calixarenes, ethylene glycols, or silanes containing unsaturated ester or alkene moieties (453). This one-pot synthetic method has been readily extended to the preparation of different types of macrocycles such as cyclophanes, bis-calix[4]arenes and sila-macrocycles. The ring size of macrocycles can be controlled by appropriate choices of the nitrile oxide precursors and the bifunctional dipolarophiles. Multiple cycloadditive macrocy-clization is a potentially useful method for the synthesis of macrocycles. 

The properties of natural macrocycles, the cyclodextrins, has stimulated interest in the preparation of synthetic macrocycles. Three basic types have been made macrocyclic amines, cyclophanes, and cyclic peptides. Hersh-field and Bender (33) prepared a bicyclic amine with hydroxamate sub-... 

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