Catalysts 2 catenane

A chiral [4]pseudocatenane 16 was synthesized from chiral triptycene-based /m( crown ether) and three equivalents of hw[p-(but-3-enyloxy)benzyl]ammonium salt in CH2CI2 in the presence of Grubbs II catalyst, followed by reduction <06CEJ5603>. Several novel calix[4]arenocrowns were prepared by a simple one-pot reaction of calix[4]monohydroquinone diacetate with bw-tosylates, e.g. l,4-bw[2-(2-(2-(2-tosyloxy-ethoxy)ethoxy)ethoxy)ethoxy)benzene, in dry MeCN in the presence of NaOH the self-assembly into calix[4]areno[2]catenanes with a dicationic salt and />-bfr(bromomethyl)-benzene was also demonstrated <06TL6012>. 

Exercise 31-9 Explain how an alkene-metathesis catalyst might convert a cyclo-alkene into (a) a long-chain unsaturated polymer, (b) a mixture of large-ring polymers, and (c) a catenane (interlocking carbon rings like two links in a chain). 

RCM and RORCM reactions in the presence of Grubbs catalysts 151 <1996JA100> and 152 <19990L953> have also been employed for catenane synthesis under reversible thermodynamic conditions. The isomeric ( /Z)-mixture of [2]catenanes 179 was obtained <1998NJC1019> by RCM of an appropriate diimide bearing ethenyl-terminated alkyl chain in the presence of crown ether 170 and catalyst 151. Similarly, initial pseudorotaxane formation followed by metathesis reaction of the double bonds present on the secondary alkylammonium ion axle has afforded [3]catenane 180 as well as [2]catenane 181 <2003TL5773>. 

Catalyst - A substance that participates in a particular chemical reaction and thereby increases its rate but without a net change in the amount of that substance in the system. [3] Catenanes, catena compounds - Hydrocarbons having two or more rings connected in the manner of links of a chain, without a covalent bond. More generally, the class catena compounds embraces functional derivatives and hetero analogues. [5] Cation - A positively charged atomic or molecular particle. Centipoise (cP) - A common non-Sl unit of viscosity, equal to mPa s. 

Bria et al. synthesized a tetracationic cyclophane-aromatic crown ether-type side-chain poly[2]catenane 59 by employing click chemistry, via route iii (Scheme 17.18) [111]. First, the template-directed coupling reaction between bis(bipyridinium) salt 28 and the alkyne-substituted p-xylylene dibromide 55, in the presence of dinaphtho crown ether 54, afforded an alkyne-functionalized [2]catenane 56 [112], Substitution of the chloro group on styrene-vinylbenzyl chloride copolymer 57 (M = 3.7 kDa, M , = 6.3 kDa) with sodium azide gave the azide-functionalized polymer 58 [83,113-115]. By employing CuS04/ascorbic acid as catalyst [116-120], click chemistry between azide-functionaUzed polymer 58 and alkyne-functionalized [2]catenane 56 afforded the side-chain poly[2]catenane 59, the successful formation of which was confirmed with Fourier transform infrared (FTIR) and NMR analyses. Unfortunately, both of these techniques revealed that the reaction of the azide groups was incomplete, and the observation was ascribed to a Coulombic repulsion of the cyclophane units and steric hindrance caused by the bulky catenane units[121]. 

A review has been published on cyclodextrins as building blocks for supramolecular structures and functional units. Included was a treatment of the the synthesis of cyclodextrins, their inclusion properties, catenanes derived from them and their use as catalysts. 

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