Václav Janout

Polymer-supported dimethyl sulfoxide as phase-transfer catalyst

SummaryCrosslinked polystyrenes with pendant -CH2SOCH3 grouping are efficient phase-transfer catalysts in liquid-liquid reactions of 1-bromooctane with several inorganic nucleophiles. Direct introduction of -CH2SOCH3 grouping into polystyrene by the reaction of a halogenated polystyrene with methylsulfinyl-methylsodium is described.

Polymer-supported oligo(N-acetyliminoethylenes) new phase transfer catalysts

SummaryOligo(N-acetyliminoethylenes), both free and grafted on polystyrene, polymethacrylate and cellulose were prepared by the ring-opening polymerization of 2-methyloxazoline. Their phase transfer catalytic activity in nucleophilic substitution reactions was examined.

Solid-phase cosolvents. A polymer analog of N-methyl-2-pyrrolidone based on crosslinked polystyrene

Abstract Polymer analogs of N-methyl-2-pyrrolidone were prepared by reacting crosslinked polystyrene with N-hydroxymethyl-2-pyrrolidone. These polymers are effective catalysts of nucleophilic substitution reactions carried out under liquid-solid (L-S) and liquid-solid-liquid conditions.

Poly(styrylmethylthiol) as an efficient debrominating reagent of 1,2-dibromides

Abstract Dibromides are readily debrominated by means of poly(styrylmethyl thiolate) with formation of the respective olefins. The polymeric reagent with a high content of sulphhydryl groups can be easily prepared from chloromethylated polystyrene; it extends possibilities of protection-deprotection reactions of the double bond.

The co-operative effect in the activation of the phenoxide anion with oligo(oxyethylenes) containing quaternary ammonium groups

An unusual increase in activity accompanying the catalysis of a model substitution reaction between sodium phenoxide and 1-bromo-octane with oligo(oxyethylenes), linear or bound to the polymer, was observed after the introduction of quaternary ammonium groups as terminal groups into the oligo(oxyethylene) chain.

Pseudocrown ethers based on polyphosphazene as effective catalysts of nucleophilic substitution reactions

SummaryPolymer pseudocrownethers based on polyphosphazene are active catalysts of nucleophilic substitution reactions. With respect to the catalytic activity, polyphosphazene is a more suitable carrier of oligo(oxyethylenes) than poly(styrene-co-divinylbenzene). With increasing length of oligo(oxyethylene) branches the catalytic activity of polymers increases. The favorable effect of the content of pseudocrownether structures is particularly visible in polymers having a longer oligo(oxyethylene) chain in those reactions in which the polymer acts as a solid cosolvent. The catalysts preserve their activity also if reused.

Polymer-supported aza-15-crown-5 as effective catalyst for phase-transfer reactions

SummaryImmobilized aza-15-crown-5 were prepared by the reaction of chloromethylated polystyrene resin with N-(2-hydroxyethyl)-aza-15-crown-5. These polymer-supported crowns were very effective catalysts of nucleophilic substitution reactions carried out under the conditions of the two-phase (L-S) or three-phase (L-S-L) catalysis.

Polymer reagents: preparation of polymer esters of thiocarboxylic acids based on crosslinked polystyrene

SummaryThe process of acylation of polymer thiols based on microporous poly (styrene-co-divinylbenzene) (crosslinking agent content 1–2%) with carboxylic acids was investigated depending of the degree of functionalization, on the crosslinking of the polymer carrier and on the structure of acids. In the presence of dicyclohexylcarbodiimide and 4-dimethylaminopyridine the acylation reactions can be conducted to high degrees of the transformation of SH groups already at room temperature. The extent of such refunctionalization reactions depends neither on the degree of functionalization of the starting polymer thiol nor on the structure of the acids. Reactions of polymer esters of thiocarboxylic acids with primary, secondary and tertiary alcohols activated with mercury (II) trifluoroacetate lead to low ester yields.