Kinetic and mechanistic studies of triethylamine-catalyzed phenylselenolactonization of 4-pentenoic acid

Abstract

The aim of this work is exploration of kinetic and mechanistic aspects of triethylaminecatalyzed phenylselenolactonization of 4-pentenoic acid by means of phenylselenenyl halides (PhSeCl and PhSeBr). The major product of these reactions is Ȗ-lactone with PhSefunctionalizated side chain, which can be easily transformed in numerous useful functional groups by very simple chemical reactions. In addition, the importance of Ȗ-lactones is reflected in the fact that a large number of these molecules present strucutural units of biologicaly active compounds.1 The kinetic and mechanism for these reactions have been investigated by the UV-Vis spectrophotometry. The rate constants, as well as thermodynamic parameters (ΔH≠, ΔS≠) have been determined using UV-Vis method at three different temperatures (288, 298 and 308K) in THF as solvent. The large negative values for the entropy of activation and low enthalpy of activation with both reagents support the SN2 mechanism, and obtained values for the rate constants have indicated higher reactivity of PhSeCl as reagent for cyclization.