Polystyrene-supported Al

Friedel-Crafts Reactions. Aluminum trifluoromethanesulfonate has been used for the Friedel-Crafts alkylation reaction of toluene with isopropyl and tert-butyl chlorides (eq 1), and for the acylation of benzene and toluene with acetyl and benzoyl chlorides in low to moderate yields. Intramolecular Friedel-Crafts acylation of an aromatic compound with Meldrum s acid has also been reported using catalytic amounts of Al(OTf)3. Acylation of 2-methoxynaphthalene with acetic anhydride has been reported using Al(OTf)3 and lithium perchlorate as an additive to afford the corresponding 6-acetylated adduct in 83% yield. Effective acylation of arenes with carboxylic acids has also been disclosed using polystyrene-supported Al(OTf)3. ... 

An efficient tetrahydropyranyl and tetrahydrofuranyl protection of various alcohols and phenols has been reported using Al(OTf)3 as a catalyst. The reaction proceeded efficiently with only 1.5 equiv of dihydropyran or dihydrofuran and 1 mol % of Al(OTf)3 at room tenperature (eq 3). The deprotection was also possible in the presence of methanol and Al(OTf)3. Polystyrene-supported Al(OTf)3 was also disclosed for the formation of thio-acetals and acylals. ... 

Acylation of aldehydes has also been possible over polystyrene-supported Al(OTf)3 catalysts affording valuable acylals (Equation (8.54)) [137]. This catalyst exhibited comparable activity with AICI3 and Al(OT 3, but with added advantages involving the abhity to be recycled, nontoxicity, noncorrosiveness, and ease of and high chemoselectivity. 

The preparation of polystyrene-supported selenosulfonates and their application for the synthesis of acetylenic sulfones have been reported by Huang et al. (Scheme 3.3) [126],... 

A novel photostabilization process of anchoring ligands onto a polystyrene support which would eliminate the possibility of leaching the metal moieties by the coordinating solvent is due to Cais et al. [24]. A typical system is the... 

Progress in process development for the synthesis of 2 recently was made by Behr and co-workers. Extraction of a palladium-phosphine catalyst by use of 1,2,4-butanetriol as extractant offers an effective separation from 2 and also an easy catalyst recycling [14]. Fitter et al. have shown that immobilization of homogeneous palladium catalysts on a polystyrene support is an alternative to the homogeneously catalyzed synthesis which enables easy catalyst recovery [15]. 

Cheng et al. [316] synthesized the polymer-bound 2-sulfony-l, 3-dienes from the corresponding support-bound suhblene, which upon thermal S02-extrusion gave the highly reactive diene (345), which could be trapped with dienophiles. The synthesis on a polystyrene support begins with polymer-bound lithium phenyl-sulfinate. S-Alkylation with trans-3, 4-dibromosulfolane (343) in the presence of pyridine gave the resin-bound 3-(phenylsulfonyl)-3-sulfolene. Thermal SO2 extrusion had to be performed in xylene under reflux, which restricts the use of this reaction to PS/DVB-resins. Neither the IRORY-Kans [317] nor the Synphase Crowns [199], which are made of polypropylene, are compatible with these reaction conditions, in which polypropylene is dissolved (Scheme 72) ... 

Small amounts of pyridine have been purified by vapour-phase chromatography, using a 180-cm column of polyethyleneglycol-400 (Shell 5%) on Embacel at 100°, with argon as carrier gas. The Karl Fischer titration can be used for determining water content. A colour test for pyrrole as a contaminant is described by Biddiscombe et al. [JChem Soc 1957 1954]. The 1 1-hydrochloride crystallises from EtOH with m 144°, b 218-219°/760mm (see below) and is hygroscopic. The 1 2-hydrochloride has m 46° [58888-58-7] and the picrate has m 165-166° [1152-90-5]. [Beilstein 20 H 181, 20 I 54, 20 II 96, 20 III/IV 2205, 20/5 V 160.] Polystyrene-supported pyridine is commercially available. 

However, the Japanese group has noted partial cleavage of the diisopropylsi-lanediyl linkage under the acidic conditions needed for the DMTr group removal [245, 247]. To circumvent this nuisance, Kobori et al. [247] have prepared a highly cross-linked polystyrene-supported phenyldiisopropylsilyl ether linker that proved to be completely stable to detritylation and used it successfully for oligonucleotide synthesis without N-protection by O-selective phosphoramidite chemistry [246] and pyrophosphate formation on solid phase [248]. The anchor can be cleaved under almost neutral conditions by 1M TBAF-AcOH in THF (90% release after 1 h) or 0.2 M triethylamine trihydrofluoride in the presence of 0.4 M triethylamine for 4h. 

Tomoi ct al. described the immobilization of TBD I by using a strategy involving the reaction of the lithium-TBD salt 2 with a chloromcthylated polystyrene 3 various polystyrene supported TBD materials (PTBD) 4 with degrees of base functionalization ranging from 1.12 to 2.40 mmol/g were prepared (Scheme 1). 

A polystyrene-supported rac-Ph2Si(Ind)2ZrCl2 was prepared by the procedure indicated in Scheme 15. 69 Combined with MAO (Al/Zr = 5000), this catalyst polymerizes ethylene at temperatures as high as 150 °C. Elemental mapping indicates that the catalyst is evenly distributed and located only on the surface of the polystyrene bead, and no Zr is contained inside the bead polymer growth occurs, then, only on the surface. "... 

Ohtani et al. used polystyrene-supported ammonium fluoride as a phase transfer catalyst (triphase catalysis) for several base-catalyzed reactions, such as cyanoethylation, Knoevenage reaction, Claisen condensation and Michael addition. The catalytic activity of the polystyrene-supported ammonium fluid was comparable to that of tetrabutylammonium fluoride (TBAF). The ionic loading and the ammonium structure of the fluoride polymers hardly affected the catalytic efficiency. The reaction was fast in a non-polar solvent (e.g., octane or toluene) from which the rate-determining step of the base-catalyzed reaction is very similar to that of the nucleophilic substitution reactions. 

Subsequently, we and Toy et al. found that insoluble polystyrene-supported triphenylphosphine is an effective catalyst for the reactions between vV-tosyli-mines and methyl vinyl ketone. The corresponding aza-MBH adducts were obtained in excellent yields and the catalysts could be reused.Subsequently, the non-phosphane-bearing styrene aromatic rings have been functionalized with polar groups and a series of such catalysts were examined for their... 

Recently, polystyrene-supported pyrrole-2-carbohydrazide (PSP) was combined with Cu(l) to make up a recyclable catalytic system (Cu(l)/PSP) for the N-(hetero)ary-lation of amines and imidazole (Huang et al., 2013). This heterogeneous catalyst could also be successfully applied to the assembly of imidazo[l,2-a]quinoxaline through the intramolecular cyclization of A -(2-iodophenyl)-l//-imidazole-2-carboxamide (Scheme 4.39). 

Franzen [56] has reviewed advances in the Suzuki, Heck, and Stille reactions in solid-state organic synthesis. There are basically two ways of adapting the Stille reaction to solid-state conditions. Either the organotin moiety or the organic residue can be attached to a solid support Nicolaou et al. [57] reported a very elegant intramolecular reaction of a polystyrene-supported vinyltin spedes bearing a terminal vinyl iodide moiety to give a 1,3-diene (Scheme 6.16) this reaction formed part of a synthesis of the natural product (S)-zearalenone. 

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