Phenylacetylene macrocyclizations

Henze, O., Lentz, D., Schafer, A., Franke, P., and Schluter, A. D. (2002) Phenylacetylene macrocycles with two opposing bipyridine donor sites synthesis, X-ray structure determinations, and Ru complexation, Chem. Eur. J. 8, 357-365 and references therein, (b) Henze, O., Ph.D. Thesis, FU Berlin, Germany, 2000, http //www.diss.fu-berlin.de/2000/47/. 

Fig. 6.2 Phenylacetylene macrocycle 1 (PAM) with pure para-substituted phenylenes and macrocycle 2 containing both para- and meta-substituted phenylenes. Additionally,...

Scheme 6.24 Alkyne metathesis for the preparation of hexameric phenylacetylene macrocycles in high yields.

Figure 5.9. The versatile technology by Moore et alJ101 has been used for the creation of phenylacetylene macrocycles PAMs).

Another example of rotary motion in a molecular system is provided by the molecular turnstile prepared by Moore and Bedard [30]. The turnstile architecture consists of a hexa(phenylacetylene) macrocyclic frame with a... 

In summary, the turnstile represents a new example of rotation in a molecular system. The fact that phenylacetylene macrocycles form discotic liquid crystals suggests the possibility that turnstiles might function as discotic ferroelectric liquid crystals [34]. A dipole appropriately incorporated on the spindle might allow for its own rotation to be controlled rapidly and reversibly by an external field. 

Tsuji proved the usefulness of this building block in the synthesis of less strained phenylacetylene macrocycles [29, 33]. Sonogashira alkynylation, Glaser-Ellington... 

In phenylacetylene macrocycles (26 and 27), acetylene-linking units have been employed in the constmction of a conjugated ring to give a discotic architecture. 

Discotic liquid crystals of phenylacetylene macrocycles 29 were first reported by Zhang and Moore in 1994 [136]. Their synthesis involves the stepwise build-up of phenylacetylene hexamers [137] followed by a macrocyclization step [138]. The key reactions of the synthesis (Scheme 33) are the palladium-catalysed coupling of aryl iodides and acetylenes, and the selective deprotection steps allowing the ends of the growing oligomer to be distinguished. The synthesis shown is just one of the many possible sequences that can be used to prepare the macrocycles. The mesophase behaviour of the discotic derivatives prepared to date is shown in Table 35 [136]. In some ways... 

Scheme 33. Synthesis of phenylacetylene macrocycles. Reagents (a) K2C03/Me0H (b) Pd(0) (c) MeI/110 C.

Table 35. Transition temperatures for discotic phenylacetylene macrocycles (see Scheme 33 for structures).

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