NEW GREEN TECHNOLOGIES FOR ORGANOCATALYTIC ASYMMETRIC EPOXIDATION APPLICATIONS IN SYNTHESIS

This thesis describes the application of asymmetric epoxidation reactions on chromene substrates mediated by Page’s iminium salt catalysts. Organocatalytic asymmetric epoxidation is an efficient tool to access enantiomerically rich epoxides. This study is divided into three main parts which are discussed in each chapter. The first part of this research is the preparation of iminium salt catalysts followed by synthesis of several chromene substrates. The final part is the application of the asymmetric epoxidation of the readily prepared iminium salts on chromene substrates. The first chapter reviews brief introduction and historical background of organocatalysis, chromene substrates and asymmetric epoxidation reactions. Towards the end of the chapter, several examples are described of past and current development of asymmetric epoxidation by organocatalysts. In the last part of Chapter 1, the discussion focuses on asymmetric epoxidation on chromene substrates. Chapter 2 discusses the preparation of Page’s iminium salts and improvement of previous methods followed by several approaches to synthesis of chromene substrates. The final part is discussing application of asymmetric epoxidation using synthesized iminium salts on the chromene substrates. Excellent enantioselectivities were observed in nonaqueous condition using TPPP as oxidant for 6-cyano-2,2’-dimethylchromene giving ee >99% while reactions under aqueous conditions afforded the corresponding diol giving ees as high as 71%. In Chapter 3, experimental procedures and data for all the compounds synthesized are included. Appendices contain HPLC trace data, NMR and IR data of several compounds.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2014

Author dc:creator

• Hassan, Noor

Language dc:language

en