Transition metal-catalyzed functionalization of alkynes and arenes.
Bathoju Chandra Chary.
Date of Issue2013
School of Physical and Mathematical Sciences
Transition metal-catalyzed reactions are one of the most powerful and direct approaches for the synthesis of organic molecules. During the past several decades, new synthetic methodologies come out continuously. The work of the thesis has been directed towards establishing transition metal-catalyzed functionalization of alkynes and arenes. This thesis is divided into two parts. Part I: Au(I)-catalyzed addition of diphenyl phosphate, Brønsted acids to alkynes and their further applications. Part II: Pd- and Rh-catalyzed functionalization of arenes using organophosphoryl directing groups In Part I, we demonstrated Au(I)-catalyzed regio- and stereo-selective addition of diphenyl phosphate to alkynes to furnish kinetically controlled the Markovnikov products and their isomerization to thermodynamically stable enolates. This methodology also extended to other Brønsted acids like carboxylic acids and sulfonic acids. To extend this approach, application of this methodology on haloalkynes provided Z-halo vinyl phosphates in a regio- and stereo-selective manner, whereas consecutive Pd-catalyzed cross-coupling reaction of Z-halo vinyl phosphates gave stereodefined trisubstituted olefins. In addition, alkynyl hydrogen phosphate in an endo- or exo-dig ring closure provided a variety of cyclic vinyl phosphates under very mild conditions. In Part II, due to importance of organophosphates in biological and organic chemistry, we aimed to explore C-H activation reactions of arenes using phosphoryl related directing groups. In Chapter V, we developed a novel Pd(II)-catalyzed protocol for C−H arylation at room temperature in which the phosphoramidate group was utilized as a directing group for the first time. Diaryliodonium triflates were used as an aryl source for these reactions. In Chapter VI, Rh(III)-catalyzed ortho-olefination reactions of dialkyl arylphosphonates were studied. In this mild and efficient process, the phosphonic ester were utilized successfully as a new directing group. In addition, mono-selectivity for unsubstituted substrates using a phosphonic diamide directing group was also achieved.