Polymer Supported Reagents: Efficient Method for Synthesis of Methylene Diesters

Abstract

In continuation of our work on polymer supported r e a~t i o n s l -~ we now report a simple and efficient method for synthesis of methylene diesters. The use of anion exchange resin for reaction between carboxylate acid anion And dichlorornethane combines the advantage of solid phase synthesis and anionic activation. Only diesters were formed from all the acids used here, except p-nitrobenzoic acid. In case of p-nitrobenzoic acid, methylene dieeter ( 6 0 % ) and chloromethyl ester (35%) were formed. The TEA salt of p-nitrobenzoic acid did not react' in boiling dichloromethane. This clearly indicates high anionic activation due to anion exchange resin than that due to the TBA salt. In addition to this reaction times were also considerably shortened (Table).This method is particularly useful to prepare monomers like lb, difunctional monomers li and methylene dieeters of heterocyclic acids like lj and lk. The reaction work up was extremely simple and products were obtained simply by filtration and evaporation of the solvent. The proceso is extremely simple, clean and cheap as resin can be reused. In case of dichloromethane reaction times are much higher (50 to 90 h). In this case 5 to 8 hrs are required. EXPERIMENTAL Preparation of exchange resin Supported carboxylate anion :packed in a column washed with 59 aqueous sodium salt of carboxylic acid (100 ml) until complete removal of chloride ion. The resin was then successively washed with water, alcohol and ether. for 10 hrs. The exchange capacity was determined by passing 1 M sodium chloride solution (100 ml) through the resin (0.3 g) in a column. The amount of carboxylate anion in the eluent was titrated with 0.01 N hydrochloric acid using methyl orange as an indicator.1 . 4 -1.2 m mol/g of dry resin. Preparation of diesters :Ion exchange resin supported carboxylate anion (5 m o l ) was reflwed in 20 ml dibromomethane for the time mentioned in the table. The resin was filtered off, washed with some more quantity of solvent to remove adsorbed product. Evaporation of the solvent furnished methylene diesters in quantitative yields and purity (Table).Commercial strongly basic anion exchange resin Amberlite IRA-400 (Cl-) 5 g Finally dried in V~C U O at SOOC over P2O5The exchange capacity was found to be ' To whom correspondence should be made.-241 -

A New Route for the Synthesis of Methylene Dibenzoate by Using An Ionic Liquid

“…For example, the benzoylation of methylenediacetamide [18] gives MDB. Other methods for preparing MDB have involved 1,8-diazabicyclo [5.4.0]undec-7-ene-methyl iodide [19] or the condensation of a potassium or sodium salt from a carboxylic acid with bishalogen methane under phase-transfer-catalysis conditions, using poly(ethylene glycol)-600 (PEG-600) [20], 18-crown-6, [21], resin [22], hexamethylphosphoramide [23] and quaternary ammonium salts [24][25] as catalysts. Researchers [26] have prepared MDB by refluxing a mixture of benzoic acid, tetrabutyl ammonium sulfate and sodium hydroxide in dichloromethane for 4 days.…”

Synthesis of esters from aldehydes or carboxylic acids with dichloromethane, dichloroethane or dichloropropane under mild conditions

“…6) or CH 2 Br 2 (ref. 7) with a carboxylic acid [eqn (1)]. For unsymmetric methylene diesters, a common route employs acyl chlorides, which react with aldehydes to give an achloro esters in the presence of ZnCl 2 , 5 and these further react with different carboxylic acids to afford the unsymmetric diesters [eqn (2)].…”

Direct Synthesis of Methylene‐Bridged Bis‐biaryl Carboxylates via Cascade Suzuki Coupling and CH2Cl2‐Based Bis‐esterification

“…Currently, the reaction of CH 2 I 2 , CH 2 Br 2 , or CH 2 Cl 2 with a carboxylic acid constitutes the prominent approach in the synthesis of methylene‐bridged bis‐carboxylates (Scheme A). The major restriction of such direct double nucleophilic substitution reaction lies in the product diversity associated with the only possible variation in carboxylic acid substrate.…”