Macrocycles thiophene-pyrrole

Since analogous macrocyclic arrays with pyrrole rings have been termed calix[ ]pyrroles (cf. Gale PA, Sessler JL, Krai V, Lynch V (1996) J Am Chem Soc 118 5140) it would be appropriate to rename these thiophene-crowns as calix[n] thiophenes... 

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. 

The acid-catalyzed reaction of 2,5-di(acetoxymethyl)thiophene with a substituted pyrrole has been briefly mentioned in CHEC-IK1996) <1996CHEC-II(2)491 >. This type of reaction has now found extensive application in the synthesis of thiaporphyrins and other macrocycles containing one or more thiophene rings. A few examples are given below. 

Macrocyclic molecules that have the ability to bind anions continue to attract considerable synthetic effort. During the course of such studies, it has been found that hybrid calixpyrroles in which some pyrrole units are replaced by thiophenes are good receptors for Y-shaped anions such as carboxylates <2005JOC1511>. One such macrocyle is compound 176. The synthesis of this compound utilizes the same type of chemistry as has been adopted for the thiaporphyrins. The bis(bipyrrolyl)furan 174 was reacted with the diol 175 (1.1 molar ratio) in MeCN in the presence of a catalytic amount of Bp3-Et20 at 0°C to give 176 in 44% yield. 

Macrocycles 158 and 159 containing alternating thiophene and pyrrole rings are obtained by a Rothemund-type synthesis <2001CEJ5099>. The so-called tetrathiaoctaphyrin can be reduced to the dihydrotetrathiaoctaphyrin. Two dithiaporphyrin-like pockets behave as independent proton acceptors. Stepwise protonation leads to several cationic species. The interconversion of isomers in solution has been discussed and a new mechanism proposed. 

The formation of borylated heterocyclic componnds has attracted mnch interest with regard to their use as starting materials for cross-conpling reactions, the possible formation of interesting macrocyclic species, and their applications in optoelectronic materials. Several synthetic routes are available for the borylation of the five-membered heterocycles thiophene, furan, pyrrole, and related componnds (101-103 ... 

For the sake of simplicity, the term pyrrole-derived will be used to refer to any macrocycle that contains any combination of five-membered, one-heteroatom-containing cycles, including pyrrole, furan, thiophene, and related systems. According to common convention, the 2- and 5-positions of these five-membered heterocycles will typically be referred to as the alpha (a) positions, while the 3- and 4-... 

In 1964, Badger and coworkers described what was the first representative of a new class of heteroatom-bridged [18]annulenes. This they did with their report on the synthesis of the so-called [18]annulene trisulfide 2.335 (Figure 2.3.4). ° Macrocycle 2.335 represents just one of ten possible macrocycles (i.e., 2.335-2.344) of this type that could in theory be derived by formally substituting one, two or all three of the thiophene subunits with pyrrole and/or furan. Indeed, since the initial report of... 

For the purposes of this review, heterosapphyrins are defined as being sap-phyrin-like macrocycles in which a furan, thiophene, or selenophene subunit serves to replace one or more of the pyrrole rings. Interestingly, like the pentaazasapphyr-ins, this class of macrocycles has its origins in a serendipitous discovery. It occurred during efforts directed toward the synthesis of the heteroatom analogs of corrole. Specifically, as first reported by Johnson and coworkers in 1969, reaction of... 

Many macrocyclic SBs have been prepared by condensation of different dicarbonyl precursors (head units (55), see Scheme 16) such as 2,6-diformylpyridine (56, R = H, 56a), 2,6-diacetylpyridine (56, R = CH3, 56b), 2,6-diformyl-4-Z-phenol (57, Z = C1- 57a, CH3-, 57b), 2,6-diacetyl-4-Z-phenol (57, Z = C1—, 57c, Z = CH3, 57d) thiophene-2,5-dicarbaldehyde (58), furan-2,5-dicarbalde-hyde (59), pyrrole-2,5-dicarbaldehyde (60), 2,6-diformyl-4Z-thiophenol (61, Z = CH3, 61a Z Bu1, 61b) or /3-triketones (62) with a wide range of different diamines (lateral chains). The majority of SB macrocycles are symmetrical and contain either phenol or pyridine as head units. Asymmetrical SB macrocycles have also been prepared. The SB macrocycles are designated [1 + 1] and [2 + 2] depending on the number of head and lateral units present (see Scheme 17). With certain precursors (i.e., 2,6-diacetylpyridine and l,3-diamino-2-hydroxypropane) [3 + 3] and [4 + 4] macrocyclic complexes have also been synthesized.177-179 The [2 + 3] condensation products have also... 

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