Macrocycle benzenoid

Most of the systems described in Chapter 5 contain small- or medium-sized or multinuclear benzenoid and non-benzenoid arenes. In Chapter 6, Hoger gives an overview over the mastery of the synthesis of macro- and megacycles. He shows different approaches towards shape-persistent macrocycles and carefully examines and discusses selected examples that display the advantages and disadvantages of macrocycle synthesis under kinetic and thermodynamic control. The template approach (both supramolecular and covalent) towards functionalized rings is also discussed and introduces a strong motif of supramolecular chemistry, which is much further developed but in a more polymer-oriented topic, in the next chapter. 

The properties of annulenes annelated with a 675 ring system are of considerable interest with respect to the participation of benzenoid tt electrons in the macrocyclic Ti-electron system. In the field of dehydroannulenes, a wide variety of annelated derivatives, such as 313314 315316317318 , 319... 

Novel photochemical (and thermal) reactions of macrocyclic oxa-sila-acetylenic ring systems (expected to show unusual optical properties because of electronic effects arising from orbital overlap of the acetylenic n system with the silicon a bonds and the oxygen lone-pair electrons) were described. While thermolysis in the presence of a transition metal carbonyl compound gave cyclization to both benzenoid and fulvene species, photolysis in the presence of the transition metal carbonyl compound (which catalyzes 1,2-silyl shifts across a carbon-carbon triple bond) gave fulvene and vinylidene products, the latter being readily photolyzed to the fulvene 159 (equation 101). 

As described in the introduction, macrocyclic lactams can be classified as ansamycins and other compounds, and the ansamycins consist of an ansa-chain and a chromophore-containing moiety. The ansamycins are typically divided into two groups, i.e., the naphthalenoid ansamycins and the benzenoid ansamycins, according to their chromophores. 

Resorcinylic macrolides are a family of natural products that possess a 14-membered macrolide core with a fused benzenoid subunit. A member of this family that has drawn significant scientific attention due to its antimalarial and cytotoxic activity is aigialomycin D. In one total synthesis of aigialomydn D, late-stage nickel-catalyzed macrocyclization was employed to afford the macrocyclic core [43]. Macrolide precursor 45 was cyclized in 61% yield in a 1 1 diastereoselectivity. Subsequent global deprotection and HPLC purification afforded aigialomycin D and the allylic alcohol epimer in 90% overall yield (Scheme 8.45). 

Consider now an interesting class of macrocyclic polyphenylenes which were synthesized [82]. For the simplest ones, some results of ESSA/TDDFT are displayed in Table 14.8. They demonstrate various patterns of spreading excitation over molecules with a peculiar benzenoid structure. 

It is expected that enlarging the aromatic macrocycle would enhance the columnar order due to intense, intermolecular n-n interactions and, thus, increase the charge carrier mobility. Hexa-peri-hexabenzocoronene (HBC) is one of the largest and most symmetrical of all-benzenoid polycyclic aromatic hydrocarbons, that function as a core fragment for DLCs. Hexa-peri-hexabenzocoronene contains 42 carbon atoms and 13 phenyl rings, so it can be considered as a nano-graphene. Mullen... 

Three classes of compounds, namely, nitroarenes, polycychc benzenoids, and macrocyclic ketones and lactones, possess musky odors. The latter have been used for the longest time in fragrance formulations. Efficient synthetic methods that can be scaled up are necessary to decrease their cost of production. Muscone (93) [45] and civetone [46], are two of the most important classical sources of musk odors. Muscone (93), the principal musk odorant perfume ingredient from the male musk... 

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