Macrocycles cyclocondensation

A completely different kind of macro cycle, a calix-salen type macrocycle, was obtained in good yield by microwave irradiation of various dialdehydes and diamines [165]. This was the first example of a calix-type synthesis under microwave conditions and without the presence of a metal template. An example of a [3 -1- 3] cyclocondensed macrocycle 265, obtained from a bis aldehyde and a chiral diamine is reported in Scheme 97. 

Samuel Danishefsky s group at the Sloan Kettering Institute for Cancer Research in New York has also been active in the synthesis of the natural epothilones and biologically active analogs. One of their syntheses also used the olefin metathesis reaction (not shown). The synthesis in Scheme 13.62 used an alternative approach to create the macrocycle, as indicated in the retrosynthetic scheme. The stereochemistry at C(6), C(7), and C(8) was established by a TiCl4-mediated cyclocondensation (Step A). The thiazole-containing side chain was created by reaction sequences F and G. The... 

Silver(I) complexes with macrocyclic nitrogen ligands are also very numerous. Mono- or homodi-nuclear silver-containing molecular clefts can be synthesized from the cyclocondensation of functionalized alkanediamines or triamines with 2,6-diacetylpyridine, pyridine-2,6-dicarbalde-hyde, thiophene-2,5-dicarbaldehyde, furan-2,5-dicarbaldehyde, or pyrrole-2,5-dicarbaldehyde in the presence of silver(I).486 97 The clefts are derived from bibracchial tetraimine Schiff base macrocycles and have been used, via transmetallation reactions, to complex other metal centers. The incorporation of a range of functionalized triamines has provided the conformational flexibility to vary the homodinuclear intermetallic separation from ca. 3 A to an excess of 6 A, and also to incorporate anions as intermetallic spacers. Some examples of the silver(I) complexes obtained are shown in Figure 5. 

Gawronski et al.21 have used NMR spectroscopy, especially NOE experiments in order to assign conformation of the chiral calixsalen-type macrocycles, products from the [3 + 3] cyclocondensation of the trans-1,2-diaminocyclohexane with hydroxydialdehydes. It was shown that the macrocycles had C3-symmetrical structure and s-syn conformation of imine C—H/cyclohexane axial C—H bond systems and s-trans conformation of the bis-imine unit. 

Bis(bromomethyl)quinoxalines 263 was treated with aldehydes 264 to obtain 265 . Macrocyclization to 266 was completed by cyclocondensation of the aldehydes 265 with the appropriate diaminoalkanes. Elwahy used this chemistry to synthesize new macrocyclic ligands containing the quinoxaline subunit. 

Scheme 3.22 Schiff base reactions (a) 1 1 cyclocondensation templated by small metal ions (b) larger macrocycles are obtained with larger templates.

Tetraoxa[22]porphyrin-(2.2.2.2) bisperchlorate 4.158 has also been prepared via the McMurry-type condensation of 2,5-diformyl furan 4.159. Here, the intermediate product of the cyclocondensation was determined to be the dihydro compound 4.160. It was isolated in 0.8% yield," and was determined to possess a cis-trans-cis-trans orientation of the single and double mew-like bonds (Scheme 4.4.3). The unsaturated bonds present in 4.160 posed no significant barrier to aromatiza-tion, however. Indeed, 4.160 underwent smooth oxidation to the 22 jr-electron macrocycle 4.158 upon treatment with DDQ, while maintaining the cis-trans-cis-trans conformation found in the dihydro species 4.160. 

The metal-templated cyclocondensation of the appropriate dicarbonyl precursor with a functionalized diamine gives the so-called bibracchial (doubly pendant-armed) SB macrocycles (Scheme 20). This area has been reviewed.20 Pendant arm macrocycles and their metal complexes have also attracted attention. Arms bearing additional potential ligating groups have been introduced at both carbon and nitrogen atoms of macrocycles which have generally been based on polyaza or... 

Bibracchial tetraimine SB macrocycle complexes derived from cyclocondensation of functionalized triamines with (56a), (56b), (58), (59), and (60) have been prepared in the presence of appropriate metal templates such as barium(II) and silver(l).193... 

A 2 2 cyclocondensation process was a by-product when the crab-like cyclization was used to form the nine-membered macrocycles. Thus, [18]N(, accompanied the desired [9]N3 when the crab-like starting material was reacted with a primary amine. An exception to this general process was observed for the cyclization reaction using the monoamine derivative of diethylene glycol where only the [9]N3 formed (Krakowiak et al., 1990b). Presumably,... 

The cyclocondensation of various diamines (some containing internal sulfur atoms) and aromatic dialdehydes is a useful route to the thiaaza-crown macrocycles. The resulting bis Schiff bases were reduced with sodium borohy-dride in good yields (method Z-10) (Baldwin et al., 1987 Lindoy and Smith,... 

Cyclocondensations of one molecule of a polyamine with carbonyl compounds are important methods for the preparation of other unsaturated peraza macrocycles. The reaction of acetone or an aldehyde such as propionaldehyde or a butyraldehyde, with triethylenetetraamine gave a tetraaza macrocycle,... 

The high-dilution cyclocondensation of diacid dichlorides with diamines has been used to form the peraza-crown macrocycles (Stetter and Marx, 1957 Stetter and Mayer, 1961). In these cases, the internal secondary amines were protected by tosyl groups. This cyclization reaction was very clean and gave... 

Methyl oleate (methyl c -q-octadecenoate) is an attractive functionalized olefin for metathesis because of its ready availability and the utility of the metathesis products. An early example is the proposed route to civetone by metathesis of methyl oleate followed by cyclocondensation (Eqs. lla,b). Civetone is a seven-teen-membered unsaturated macrocyclic ketone (d5-9-cycloheptadecen-l-one) identical with the natural compound (civet cat). It has an intense musk odour, and is therefore an attractive perfume component. 

Metal complexes of Schiff-base macrocycle can be prepared by cyclocondensation of pyridine-2,6-di-carboxaldehyde with benzene-1.2-diamine in the presence of Sr Pb -", or The metal-free mac-... 

Calix[4]resorcinarenes, a subclass of calixarenes, are large cyclic tetramers that have found applications as macrocyclic receptors, host molecules, host-guest complexes, and so on (Botta et al, 2005 Martinez et al., 2000 Leyton et al., 2005 Yonetake et al, 2001). It shonld be noted that the synthesis of calix[4]resorcinarenes was first reported in the late nineteenth century by Bayer based on the concentrated sulfuric acid-catalyzed cyclocondensation of benzaldehyde and resorcinol (Bayer, 1872). These cyclic compounds were synthesized by TSA (Scheme 3.8) (Karami etal.,2012f). 

Keywords Borazines Boron heterocycles Boroxins Cyclocondensation Heteraborines Heteraboroles Isoelectronic Isosteric Macrocycles... 

In contrast to dap, 2,6-dfp undergoes 2 + 2 cyclocondensation reactions with 3,3-triamines in the absence of metal ions as template. Using bis(3-aminopropyl)-methylamine or lV,lV-bis(3-aminopropyl)-A, iV -dimethyl-l,2-diaminoethane as ligsons is supposed to give the 28-membered ring-expanded macrocycles L708 and L709, respectively (Eq. 3.34) [82]. 

Calix[10-12]arenes Lamartine and coworkers [17] have obtained the p-tert-butylcalix[10 and 12]arenes C[10] and C[12], through a cyclocondensation of linear phenolic ohgomers (a 6 + 3 procedure), under basic conditions. These macrocycles were isolated even up to half-gram scale by usual work-up (several crystallizations and purifications by column cromatography). 

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