BigPatents India

A process for the preparation of carbamate esters of formula I, O R1 R-(CH2)n-CH2-O-C- N I R2 wherein R is an alkyl group containing 1-10 carbon atoms or an aromatic group such as phenyl, naphthyl, phenanthryl, or a heteroaromatic selected from quinoline and benzopyrans; n is 1 to 1 0;, Rl and R2 individually is a lower alkyl selected from methyl, ethyl, propyl, butyl, amyl; or a branched chain lower alkyl selected from isopropyl, isoamyl; or a cycloalkyl containing 3 to 8 carbon atoms; or an alkyl-aryl selected from benzyl, ethyl-phenyl; or an aromatic group selected from phenyl, substituted phenyl, naphthyl, which comprises reacting an appropriate alcohol of formula II, R-(CH2) n.CH2-OH II Wherein R is same as defined above in formula I and n is 1-10 with an appropriate amine of formula III, wherein R1 and R2 individually is same as defined above for the formula I; in an organic aprotic solvent selected from dimethylsulphoxide (DMSO), dimethylformamide(DMF), acetonitrile and hexamethyl phosphoramide (HMPA) with CO2, in the presence of triphenylphosphine (Ph3P) and diethylazadicarboxylate (DEAD) i.e.Mitsunobu's reagent, at an elevated temperature ranging between 80-I20°C for a period of 3-5 hrs; diluting the reaction mixture with distilled water, extraction with water immiscible organic solvant such as benzene, toluene, ethyl acetate and removal of the solvent to get the desired product.