Arenes side-chain derivatives

Dienes also can alkylate arenes to give products which are generally cyclic. For example, isoprene reacts with 1,2,4-trimethylbenzene in the presence of H2SO4 to give an indane derivative (equation 91). A large number of phenols have been used for alkylations with dienes. The products are either allylated phenols, or products derived by further ring closure of the phenolic oxygen with the side chain derived from the diene. 

The possibility that Ru(II) can form Jt-complexes with the aromatic side-chains of proteins is an intriguing one. Such complexes are known for simple amino acids derivatives of e.g. tryptophan [50], but have yet to be characterized for protein adducts ofRu(II) arenes. They are known for cyclopentadiene complexes. Reaction of strapped cyclopentadienyl complexes [(ri -C5,Ti -N-C5H4(CH2)nNH2)-Ru(CH3CN)2] (n = 2,3) with proteins such as the hormone secretin in water can lead to sandwich complexes by ruthenation of the arene side chain of the phenylalanine residue (Fig. 2.19) [103]. 

Some of the common aromatics found in crude oil are the simple derivatives of benzene in which one or more alkyl groups (CHg) are attached to the basic benzene molecule as a side chain which takes the place of a hydrogen atom. These arenes are either liquids or solids under standard conditions. 

Reactions Involving Alkyl and Alkenyl Side Chains in Arenes and Arene Derivatives... 

Benzene derivatives with saturated or unsaturated C-containing side chains are arenes. Examples are cumene or isopropylbenzene, C(,H CH(CH,)2, and styrene or phenylethene, Cf,H,CH=CH2. 

When alkylarenes are cocondensed with Re atoms, C H activation of the ahphatic side chains occurs and a variety of novel arene derivatives of Re with /r-arylidene and hydride bridges, [Re2( -arene)2(/(r-CHAr)(/r-H)2], are formed, for example, products containing o-xylyl ligands. Similar reactions are observed with saturated hydrocarbons, for example, cocondensation with CMc4 gives (146). 

Polymerization of phthalocyanines in water occurs for derivatives substituted with oligo (ethylene oxide) side-chains (27c).167 168 In the lyotropic mesophases in water supramolecular polymers are present, and a comparative aggregation study between tetraphen-ylporphyrins and phthalocyanines proved the polymerization of the phthalocyanines to be stronger.168 The strong arene—arene interactions and the flatness of the aromatic core in the phthalocyanines causes them to aggregate more strongly, also mediated by the additional hydrophobic effect. 

Similarly, chromium-complexed benzylic cations are also stabilized and organic reactions based on the benzylic cation species have been developed. For example, planar chiral o-substituted benzaldehyde dimethylacetal chromium complexes 4 were treated with 3-buten-l-ol in the presence of TiCl4 to give tet-rahydropyran derivatives with high diastereoselectivity (Eq. 5) [5]. The chromium-complexed benzylic oxonium ion 6 would be also generated and subsequent intramolecular cyclization afforded the cyclization product 7. Furthermore, the chromium-complexed benzyl alcohol derivative having electron-rich arene ring at the side chain produced tetrahydroisoquinoline skeleton by treatment with Lewis acid with stereochemical retention at the benzylic position (Eq. 6) [6]. 

Our original interest in pyrogallol[4]arene-derived capsules was to prepare molecules that had relatively long aUcyl side chains. There were two initial notions associated with this research direction. The first was to see if the capsule would comprise a stable scaffold upon which a p5e do-bilayer type membrane could be constructed. The octahedral capsule would have 24 alkyl chains radiating from it in all directions. For example, exposure of the capsule to phospholipids might create a p ewd/o-liposome. The concept of a phospholipid encrusted pyrogallol[4]arene capsule is illustrated schematically in Fig. 8.6. 

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