Kinetic study of dichlorocarbene addition to olefins via a quaternized highly branched polyacrylamide as a new multi-site phase transfer catalyst

Abstract

A quaternized highly branched polyacrylamide was synthesized and used as an efficient multi-site polymeric phase transfer catalyst in dichlorocyclopropanation reaction. The quaternized highly branched polyacrylamide was synthesized via two steps. First, a highly branched polyacrylamide was synthesized via self-condensing vinyl polymerization using appropriate molar ratio of monomer to diperiodatocuprate(III) solution. In the second step, 3-acrylamidopropyltrimethylammonium iodide was polymerized on peripheral area of the highly branched polyacrylamide in the presence of diperiodatocuprate(III) solution. The thermal behavior of highly branched polyacrylamide and that of the quaternized highly branched polyacrylamide was studied by DSC and TGA analyses. Then the activity of the synthesized quaternized highly branched polyacrylamide was investigated as phase transfer catalyst in dichlorocyclopropanation of olefins in biphasic medium. To this purpose, the synthesized catalyst was used in generating dichlorocarbene from chloroform in aqueous sodium hydroxide solution which was subsequently added to olefins. This catalyst is very active and its application yields high volume of products which are obtained in relatively short time. Various factors which influence the rate of dichlorocyclopropanation reaction, such as base concentration, stirring speed, temperature and amount of catalyst, are studied and a mechanism for addition reaction of dichlorocarbene to olefins is proposed. This efficient phase transfer catalyst was reused several times without any loss of activity.