Development of cost effective and environmentally benign methods for the derivatization functional group transformation of and#945; hydroxy carbonyl compounds

Abstract

In this thesis, an efficient, cost effective and environmentally benign approach for the derivatization of and#945;-hydroxy carbonyl compounds has been developed and presented. A variety of and#945;- hydroxy carbonyl compounds such as and#945;-hydroxy ketones, and#945;- hydroxy acid and and#945;-hydroxy ester have been synthesized from the diketones using the reported procedures. Since the conformational preferences of and#945;-hydroxy ketones can affect their reactivity, single crystal X-ray structural studies of a variety of and#945;- hydroxy ketones have been conducted to comprehend the conformational and packing features in the solid-state. Furthermore, the role of weak interactions such as hydrogen bonds, C-H O, C-H and#960; and and#960; and#960; etc., has also been investigated to explain the observed conformation(s) and crystal packing. Two types of reactions, namely, deoxygenation and deconstructive carbonyl olefination of and#945;-hydroxy carbonyl compounds have been developed under transition metal-free and mild reaction condition. A metal-free, direct and selective deoxygenation of a variety of and#945;-hydroxy carbonyl compounds has been achieved using triethylsilane (Et3SiH) as soluble hydride source and aq. HClO4 (70%) as a cheaper Brønsted acid catalyst to obtain an important class of and#945;,and#945;-diaryl carbonyl compounds such as 1,2,2-triaryl ethane, 2,2-diphenyl ethanoic acid and methyl 2,2-diphenyl acetate. Mechanistically, the intermediacy of and#945;-carbonyl cation has been proposed on the basis of atmospheric pressure chemical ionization (APCI) mass spectral data. In another development, a new complementary approach of Knoevenagel reaction has been established via deconstructive carbonyl olefination using and#945;-hydroxy ketones as carbonyl precursors. In this approach, KOtBu-assisted deconstructive carbonyl olefination of a variety of secondary and tertiary and#945;- hydroxy ketones have been achieved using arylacetonitriles as coupling partner to obtain 1,2-diaryl acrylonitriles under transition metal-free and mild reaction condition.