Macrocycles substitution reactions

A similar synthetic approach was used in the synthesis of polyfluorinated oxygen-and nitrogen-containing macrocycles. Substitution reaction of fluorinated pyridines... 

Kinetics and mechanisms of substitution reactions of octahedral macrocyclic amine complexes. C. K. Poon, Coord. Chem. Rev., 1973,10,1-35 (130). 

Omori, T. Substitution Reactions of Technetium Compounds. 176, 253-274 (1996). Ostrowicky, A., Koepp, E., Vogtle, F. The Vesium Effect Synthesis of Medio- and Macrocyclic Compounds. 161, 37-68 (1991). 

An 8000-member library of trisamino- and aminooxy-l,3,5-triazines has been prepared by use of highly effective, microwave-assisted nucleophilic substitution of polypropylene (PP) or cellulose membrane-bound monochlorotriazines. The key step relied on the microwave-promoted substitution of the chlorine atom in monochlorotriazines (Scheme 12.7) [35]. Whereas the conventional procedure required relatively harsh conditions such as 80 °C for 5 h or very long reaction times (4 days), all substitution reactions were found to proceed within 6 min, with both amines and solutions of cesium salts of phenols, and use of microwave irradiation in a domestic oven under atmospheric reaction conditions. The reactions were conducted by applying a SPOT-synthesis technique [36] on 18 x 26 cm cellulose membranes leading to a spatially addressed parallel assembly of the desired triazines after cleavage with TFA vapor. This concept was later also extended to other halogenated heterocycles, such as 2,4,6-trichloropyrimidine, 4,6-dichloro-5-nitropyrimidine, and 2,6,8-trichloro-7-methylpurine, and applied to the synthesis of macrocyclic peptidomimetics [37]. 

Annulene was the first macrocyclic annulene containing (4n -j- 2) zr-electrons to be synthesized. The compound is of considerable interest, since it is the type of annulene that was predicted to be aromatic by Hiickel.10 It proved to be aromatic in practice, as evidenced from the proton magnetic resonance spectrum,8-11 the X-ray crystallographic analysis,18 and the fact that electrophilic substitution reactions could be effected.13... 

Electrophilic substitution reactions on alkynylsilanes are also known. In 1978 K. Ultimootd, M. Tanaka and coworkers by an intramolecular reaction carried out the synthesis of a macrocyclic ketone. 

In the area of allenic non-natural product chemistry, the synthesis of the [34]alle-nophane 14 (Scheme 2.4) is particularly noteworthy, with all four of its allenic bridges being formed through subsequent SN2 substitution reactions of propargylic acetates with a methyl magnesium cuprate [14] (see Section 2.5 for an alternative synthesis of macrocyclic allenes). 

Sulfonamide groups incorporated in rotaxanes enable the construction of new topological assemblies provided with mechanically and covalently bonded subunits. Methylation of a [2]rotaxane containing a sulfonamide unit in the axle revealed that the substitution reaction is not sterically hindered by the macrocycle. Similar to the synthesis of the pretzelane 96, the two sulfonamide groups of rotaxane 80m were bridged with 95 to form 100 in 71% yield (Figure 39) [46]. The additional covalent bond converts the former [2]rotaxane into a [l]rotaxane and reduces the mobility of the wheel along the axle. Rotaxanes 80m and 100 are his-... 

The field of nickel complexes with macrocydic ligands is enormous and continuous interest in this area in recent years has resulted in innumerable publications. A number of books and review articles are also available covering the general argument of the bonding capability of the various macrocydic ligands towards transition and non-transition metals. 22 2627 Synthetic procedures for metal complexes with some tetraaza macrocycles have been reported.2628 Kinetics and mechanism of substitution reactions of six-coordinate macrocydic complexes have also been reviewed.2629... 

Binuclear complexes have also been obtained by the electrophilic substitution reaction of [Ni(Me2[Z]dienatoN4)]+ (Z = 13,14) with -substituted benzoyl chlorides (Scheme 53), 2791 A series of dimeric nickel(II) complexes of type (385) has been synthesized as outlined in Scheme 54.2792 In the complex with m-xylene bridges the two nickel(II) atoms are 1360 pm apart, separated by the cavity of the pair of 16-membered macrocyclic ligands. 

Nickel(II) complexes with cryptands are still rare. In general the encapsulation of nickel(II) in this type of macrocyclic ligand makes the complexes extraordinarily resistant to dissociation and substitution reactions. 

It was found that the 15-membered macrocyclic complexes were significantly less acidic. Similar reversible protonations have been shown to occur in related macrocyclic complexes36 37 and this work has been developed by Busch into a major study of ligand reactions,38 which are summarized in equations (16)—(19). It is significant that these reactions include not only typical substitution reactions such as acylation and nitration (equations 16 and 19), but also nucleophilic addition to isocyanates (equation 17) and to a, 3-unsaturated esters (equation 18). 

The analogy between imines and carbonyls was introduced earlier, and just as 1,3-dike-tonate complexes undergo electrophilic substitution reactions at the 2-position, so do their nitrogen analogues. Reactions of this type are commonly observed in macrocyclic ligands, and many examples are known. Electrophilic reactions ranging from nitration and Friedel-Crafts acylation to Michael addition have been described. Reactions of 1,3-diimi-nes and of 3-iminoketones are well known. The reactions are useful for the synthesis of derivatised macrocyclic complexes, as in the preparation of the nickel(n) complex of a nitro-substituted ligand depicted in Fig. 5-12. 

A convenient and efficient synthetic route to a new class of macrocyclic aryl ether ether sulfide oligomers was reported. The process is shown in Fig. 28. This new class of cyclic oligomers is prepared in excellent yield by quantitative chemical reduction of macrocyclic aryl ether ether sulfoxide oligomers with oxalyl chloride and tetrabutylammonium iodide. The cyclic sulfoxide oligomeric precursors are prepared in high yields by an aromatic nucleophilic substitution reaction from bis(4-fluorophenyl) sulfoxide with potassium salts of bisphenols under high-dilution conditions [99]. 

As a further development of these ideas, macrocylic libraries have been prepared recently which, whilst they have some preorganisational properties, still mix well. Libraries 4, see Scheme 3, are based on macrocycles of the type 17,14 and were "mixed" using transesterification, and Libraries 5 on macrocycles of the type 18,1516 were"mixed" using nucleophilic aromatic substitution reactions catalysed by cesium fluoride. 

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