Macrocycles reactivity

The subject matter of this chapter will be subdivided into sections concerning template synthesis of the complexes structural and thermodynamic properties of the complexes with synthetic cyclic polyamines complexes with mixed-donor macrocycles reactivity of the complexes cryptates and complexes with phthalocyanines and porphyrins. 

On the experimental side, Endicott and co-workers have shown that in chloride-bridged reactions of a series of couples LM(III/II), where L is a tetraazo macrocycle, reactivity is strongly influenced by the total number of electrons in the three-center system A" -C1-B, falling off in a series from A = B = Ni(II) to A = B = Co(II). Effective mixing of metal and bridge orbitals is also significant. " ... 

Stmctural and chemical modification of urethane containing polymer matri-ces with macrocycles - calixarenes having reactive hydrazide groups have been carried out and stmcture, physico chemical and sensor properties of polyure-thanesemicarbazides (PUS) synthesised have been studied. The polymers obtained (on the base of polypropylene glycol MM 1000 and polysiloxane diol MM 860, hexamethylene diisocyanate and calixarene dihydrazide) are identified by IR-spectroscopy, size exclusion chromatography (SEC), DSC, WAXS and SAXS methods. 

An interesting use of the Camps quinoline synthesis is in the ring contraction of macrocycles. Treatment of 9 member ring 24 with sodium hydroxide in water furnished quinolin-4-ol 25, while 26 furnishes exclusively quinolin-2-ol 27 under the same reaction conditions (no yield was given for either reaction). The reaction does not work with smaller macrocycles. The authors rationalize the difference in reactivity based upon ground state conformation differences, but do not elaborate. 

The high stability of porphyrins and metalloporphyrins is based on their aromaticity, so that porphyrins are not only most widespread in biological systems but also are found as geoporphyrins in sediments and have even been detected in interstellar space. The stability of the porphyrin ring system can be demonstrated by treatment with strong acids, which leave the macrocycle untouched. The instability of porphyrins occurs in reduction and oxidation reactions especially in the presence of light. The most common chemical reactivity of the porphyrin nucleus is electrophilic substitution which is typical for aromatic compounds. 

The search for the racemic form of 15, prepared by allylic cyclopropanation of farnesyl diazoacetate 14, prompted the use of Rh2(OAc)4 for this process. But, instead of 15, addition occurred to the terminal double bond exclusively and in high yield (Eq. 6) [65]. This example initiated studies that have demonstrated the generality of the process [66-68] and its suitability for asymmetric cyclopropanation [69]. Since carbon-hydrogen insertion is in competition with addition, only the most reactive carboxamidate-ligated catalysts effect macrocyclic cyclopropanation [70] (Eq. 7), and CuPF6/bis-oxazoline 28 generally produces the highest level of enantiocontrol. 

The results obtained with the various metathesis substrates depicted in Scheme 44 demonstrate the lack of a stereopredictive model for the RCM-based formation of macrocycles, not only by the strong influence that may be exhibited by remote substituents, but also by the fact that the use of more reactive second-generation catalysts may be unfavorable for the stereochemical outcome of the reaction. Dienes 212a-f illustrate the influence of the substitution pattern. All reactions were performed with Grubbs first-generation catalyst A... 

Electronic effects on the reactions of [Rh(Por)h dimers and hydrides were probed by varying the porphyrin macrocycle. OEP and TPP vary considerably in their properties, with OEP being one of the strongest and TPP one of the weakest (7-donors among porphyrin derivatives. However. Rh(Por)]2, Rh(Por)H, and Rh(Por)r showed the same reactivity in a variety of reactions for both OEP and TPP, indicating that electronic effects relating to the porphyrin ligand have... 

Stability towards heating, irradiation and exposure to air was also reported for [n]pericyclinosilanes 70-72 [20, 21], and even the highly strained 74 [24]. But, in contrast to the hydrocarbons, the pericyclinosilanes did not react with bromine [21 ]. On the other hand, the presence of the silicon atoms brings about a specific reactivity of these macrocycles making them labile and capable of changes in ring size. Thus, when a mixture of compounds 70-72 a (n = 6) was... 

With sp bond angles calculated to be around 162°, macrocycle 131 would be highly strained and was therefore expected to be quite reactive [79]. The octa-cobalt complex 132, on the other hand, should be readily isolable. Indeed, 132 was prepared easily from 133 in five steps, and was isolated as stable, deep maroon crystals (Scheme 30). All spectroscopic data supported formation of the strain-free dimeric structure. Unfortunately, all attempts to liberate 132 from the cobalt units led only to insoluble materials. Diederich et al. observed similar problems when trying to prepare the cyclocarbons [5c]. Whether the failure to prepare these two classes of macrocycles is due to the extreme reactivity of the distorted polyyne moiety or to the lack of a viable synthetic route is not certain. Thus, isolation and characterization of smaller bent hexatriyne- and octatetrayne-containing systems is an important goal that should help answer these questions. 

Recently, we have prepared an oligo(cyclooctene) snpported Co-salen catalyst (A), with the idea that the higher local concentration of Co-salen species in the macrocyclic framework would enhance the reactivity and enantioselectivity in the HKR reaction (18). 

Using 1,4,8,11-tetraazacyclotetradecane, the structure of complex (800) (distorted trigonal planar Cu-Cu 6.739 A) was determined. Reactivity with 02 was investigated to demonstrate the formation of trans-l,2-peroxo species.585 As part of their work with copper(I) complexes with 02, the structure of a dicopper(I) complex ((801) distorted tetrahedral 7.04 A), supported by macrocyclic ligand environment, was reported by Comba and co-workers. Tolman and co-workers structurally characterized a three-coordinate copper(I)-phenoxide complex (802) (planar T-shaped) that models the reduced form of GO.587 The copper(I) analogue [Cu(L)][CF3-SO3]-0.43MeOI I (803) of a copper(II) complex (534) was also reported to demonstrate the role of ligand framework conformability in CV /Cu1 redox potentials.434 Wilson and co-workers... 

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