2- -1,3-xylylene- crown

Markies PR, Akkerman OS, Bickelhaupt F, Smeets WJJ, Spek AL (1994) Complexation of bis(p-tert-butylphenyl)magnesium with xylylene crown ethers and glymes. Organometallics 13 2616-2627... 

Reinhoudt, Gray, Smit and Veenstra prepared a number of monomer and dimer crowns based on a variety of substituted xylylene units. They first conducted the reaction of 1,2-dibromomethylbenzene and a polyethylene glycol with sodium hydride or potassium Z-butoxide in toluene solution. Mixtures of the 1 1 and 2 2 (monomer and dimer) products were isolated and some polymer was formed . The reaction was conducted at temperatures from 30—60° and appeared to be complete in a maximum of one hour. The authors noted that the highest yield of 1 1 cyclic product was obtained with disodium tetraethylene glycolate instead of dipotassium hexaethylene gly-colate (see also Chap. 2) . Chloromethylation of 1,3-benzodioxole followed by reaction with disodium tetraethylene glycolate afforded the macrocycle (29% yield) illustrated in Eq. (3.20). 

An example of this is found in the synthesis of a crown containing a mefa-xylylene unit (see also Sect. 3.5) and a convergent methoxyl group. 4-Methyl-2,6-bishydroxymethyl-anisole was treated with pentaethylene glycol and sodium hydride in THF solution to afford the crown (mp 71—73°) shown in Eq. (3.52) in 59% yield. 

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]. 

SCHEME 27.18 5 Bromo l,3-xylylene-15-crown-4 deprotometalation using a diarylmagnesium. 

Scheme 4 Synthesis of 2-(phenylcalcio)-l,3-xylylene-[18]crown-5 via halogen-metal exchange reaction of bromoarene with diphenylcalcium...

Markies PR, Nomoto T, Schat G, Akkerman OS, Bickelhaupt F (1991) Unusual Metalation and Halogen-Metal Exchange Reactions between 1,3-Xylyl Crown Ethers and Organomagnesium Reagents. X-ray Structure of 2-[(p-ter/-Butylphenyl)magnesio]-l,3-xylylene-18-crown-5. Organometallics 10 3826-3837... 

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