Cyclic compounds macrocyclic

The strength of this bonding depends on the kind of ether Simple ethers form relatively weak complexes with metal ions but Charles J Pedersen of Du Pont discovered that cer tain polyethers form much more stable complexes with metal ions than do simple ethers Pedersen prepared a series of macrocyclic polyethers cyclic compounds contain mg four or more oxygens m a ring of 12 or more atoms He called these compounds crown ethers, because their molecular models resemble crowns Systematic nomencla ture of crown ethers is somewhat cumbersome and so Pedersen devised a shorthand description whereby the word crown is preceded by the total number of atoms m the ring and is followed by the number of oxygen atoms... 

All cyclic compounds of types 83-88 have been characterized by their diagnostically simple and C-NMR spectra. Some general regularities can be observed, namely, a small but steady upfield shift in the C-NMR spectra of the carbon signals of the polyacetylenic macrocycle with increasing ring sizes. 

Only two general methods have been developed for the synthesis of the macrocyclic annulenes.9 The first of these, developed by Sondheimer and co-workers, involves the oxidative coupling of a suitable terminal diacetylene to a macrocyclic polyacetylene of required ring size, using typically cupric acetate in pyridine. The cyclic compound is then transformed to a dehydroannulene, usually by prototropic rearrangement effected by potassium i-butoxide. Finally, partial catalytic hydrogenation of the triple bonds to double bonds leads to the annulene. 

Various cyclic compounds from three-membered rings to macrocycles have been prepared by intramolecular allylation. A typical example of this cyclization is the reaction of the monoacetate of 1,4-butenediol derivative 91 with the active methylene compound 92, which afforded the allylic alcohol 93. The three-membered chrysantemic acid derivatives 94 and 95 were then prepared after acetylation of 93, followed by Pd-catalysed intramolecular allylation [53],... 

Dienes are cyclized by intramolecular metathesis. In particular, cyclic alkenes 43 and ethylene are formed by the ring-closing metathesis of the a,co-diene 46. This is the reverse reaction of ethenolysis. Alkene metathesis is reversible, and usually an equilibrium mixture of alkenes is formed. However, the metathesis of a,co-dienes 46 generates ethylene as one product, which can be removed easily from reaction mixtures to afford cyclic compounds 43 nearly quantitatively. This is a most useful reaction, because from not only five to eight membered rings, but also macrocycles can be prepared by RCM under high-dilution conditions. However, it should be noted that RCM is an intramolecular reaction and competitive with acyclic diene metathesis polymerization (ADMET), which is intermolecular to form the polymer 47. In addition, the polymer 47 may be formed by ROMP of the cyclic compounds 43. 

Abstract Phthalocyanines represent a versatile class of functional dyes which have found applications in various disciplines ranging from materials science, catalysis, nanotechnology to medicine. The intrinsic properties of the macrocycles as well as their molecular arrangements, both in solution and in the condensed phase, can be altered through rational chemical modification. Conjugation of other functional units to phthalocyanines can also complement the characteristics of the macrocycles. All these approaches can improve the performance of these macro-cyclic compounds as advanced functional materials. The purpose of this article is to provide an up-to-date review of the current research status of phthalocyanine-containing supramolecular systems. The formation, structures, and properties of self-assembled phthalocyanines as well as the non-covalent hetero-arrays containing phthalocyanines and other functional units are reviewed herein. 

The synthesis of macrocyclic compounds can be accomplished by ring forming or by ring enlargement processes. The starting materials for the ring enlargement approach are, of course, cyclic compounds themselves, presumably easier to prepare than the ultimate product. 

In 1973, Van Dorp et al. found a number of interesting macro-cyclic compounds, including some with both double and triple unsaturated bonds (26), but made no attempt to determine their biological significance. They compared the macrocyclic ketones and the fatty acids found in civet and muskrat gland and concluded that there is evidently no correlation between the macrocyclic ketone composition and the fatty acid composition. For example, cycloheptadecanone was the most prominent peak in the muskrat gland (41% of the macrocyclic ketones), whereas the stearic acid from which it could have been formed, was among the minor components (3%) of the fatty acids. 

Indeed, this MCR worked extremely well by simply stirring the three components in trifluoroethanol (TFE) at room temperature. Interestingly, no high-dilution conditions were required for the above transformation. Authors prepared 12-, 15-and 18-membered macrocycles and even nine-membered medium-sized cycles in excellent yields with diastereoselectivities. Two examples were depicted in Scheme 11. Thus, stirring a TFE solution of aziridine aldehyde 29, dipeptide 30 and ferf-butyl isocyanide at room temperature for 4 h afforded a nine-membered cycle 31 in 83% yield. Similarly, a 18-membered cyclopeptide 33 was obtained in 77% yield by the reaction of 29, pentapeptide 32 and ferf-butyl isocyanide. In both examples, the cyclic compounds 31 and 33 were formed with high diastereoselectivities (dr > 20/1). This is intriguing, as Ugi reaction provided generally low to moderate stereoselection when chiral substrates was used as inputs ([66-72] for enantioselective isocyanide-based MCRs, see [73-80]). 

Carbohydrate crown ethers were obtained with ethylene spacers from a crown ether point of view, the carbohydrate vicinal diols are replacing one ethylene glycol unit [181,182], Cyclic compounds synthesized include bis-gluco-15-crown-5 82, bis-gluco-21-crown-7, and tetra-gluco-24-crown-8 (O Scheme 14). These chiral macrocycles could serve as catalysts in the asymmetric Michael addition of methyl a-phenylacetate to methyl acrylate. With the goal to study molecular interactions, P,P, and Q, Q -bis-maltosides with aliphatic two-, three-, or four-earbon spacers were synthesized [183]. Spaced cyclodextrins were prepared to study their supramolecular properties [184,185]. 

For the purposes of this review we will restrict macrocycles to those cyclic compounds with at least three heteroatoms within the ring and with at least two carbon atoms between each adjacent pair of heteroatoms. The following discussion will concentrate on macrocycles containing only S or Se or Te donor atoms, with occasional reference to mixed-donor macrocycles containing one or more of these donor types as appropriate. 

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