Date of Award

5-27-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Science

First Advisor

Anindya Ghosh

Abstract

Carbon dioxide (CO2) is an abundant, environmentally benign and renewable source of carbon. Use of CO2 may potentially end the use of other toxic C1 synthons, such as phosgene, carbon monoxide, and isocyanate. However, the extreme inertness of CO2 presents great difficulty for its use in organic synthesis. In Chapter 3, the synthesis of cyclic carbonates from corresponding epoxides under low pressures of CO2 (300 psi), relatively mild temperature (130 oC) using chlorostannoxane catalysts is discussed. Activities of the catalysts have been optimized in the pressure range of 100-700 psi, temperature range of 100-130 oC, with reference to propylene oxide. Using butyl and phenyl groups as representative substituents on the metal centers of chlorostannoxanes, the effect of change in the nature of the catalyst on the synthesis of cyclic carbonates of various epoxides has been studied. Activity of 1,3-Dichloro-tetra-n-butyl-distannoxane (1a) was studied on various epoxides under the considered reaction conditions. In chapter 4, discussion about the synthesis of 2-oxazolidinones from 2-amino alcohols and CO2 in the presence of chlorostannoxanes while using methanol as co-solvent is presented. We were able to produce considerable turnover numbers (TONs), as high as 138 over the reaction period of 6 hours. A discussion about the influence of various reaction parameters such as temperature, pressure, substrate and catalyst concentrations on the activity of 1a catalyst is also presented Chapter 5 discusses about the capability of chlorostannoxanes in the synthesis of 2-oxazolidinones from 2-amino alcohols (2AA) and diethyl carbonate. A study on the change in activity of the catalysts over the period of time using two different substituents (butyl and phenyl) at Sna and Snb centers of chlorostannoxanes is also reported. In this report, a series of 2AAs, both chiral and achiral have been studied in order to understand the structure-reactivity relationship. Interestingly, recovered chlorostannoxane catalysts showed efficiency in producing 2-oxazolidnones (OXZ) similar to that of the original one. Additionally, the reaction kinetics and the possible mechanism of the catalytic pathway have been discussed. The present work also addresses for the first time the effect of substituents on Sn to understand the mechanistic route of OXZ formation.

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