| dc.description.abstract | Alkynes are versatile and valuable synthetic precursors in a variety of organic
transformations and have found tremendous applications in materials science and pharmaceutical
chemistry. In recent years, there has been a tremendous growth in the development of transitionmetal
catalyzed organic transformations by alkynes coupling reactions such as ring constructions
(carbocycles and heterocycles), hydroarylation and hydroamination. This thesis describes the
development of new transition metal catalyst for alkyne coupling reactions. The results are
highlighted by chemoselective coupling between internal alkynes and N-H aromatic ketimines to
synthesize indenamine, dihydroisoquinoline, and 2-aza-1,3-butadiene derivatives.
Chapter 1 introduces background for alkyne coupling reactions towards hydrometalation,
hydroarylation and hydroamination. Also this chapter provides new strategies developed towards
C-H activation and hydroamination by using late transition metal catalysts.
Chapter 2 describes catalytic development of rhodium catalyzed redox-neutral [4+2]
annulation of N-H aromatic ketimines and alkynes to synthesize multi-substituted 3,4-
dihydroisoquinolines (DHIQs) in high chemo-selectivity over competing annulation processes,
exclusive cis-diastereoselectivity, and distinct regioselectivity for alkyne addition.
Chapter 3 describes development of earth abundant metal nickel as the catalyst for the
Nickel (0)/NHC-based catalyst system for alkyne hydroimination with aromatic N−H ketimines
as N-nucleophiles. To demonstrate the potential of current method for practical synthesis, we
also carried out a gram-scale alkyne hydroimination with benzophenone imine.
Chapter 4 describes catalyst development for oxidative [4+2] imine/alkyne annulation
with unconventional regioselectivity. Even though there are numerous methods towards the
synthesis of isoquinoline derivative here in this chapter we proposed a different pathway for C-N bond formation compared to other reported methods. In spite of moderate yields for the
unsymmetrical alkynes the regioselectivity is different from other reported isoquinoline products
by oxidative [4+2] annulations.
Chapter 5 describes about Ni/NHC catalyst development towards stereoselective
semihydrogenation of alkynes by usig simple alcohol, isopropanol as the hydrogen source. Here
we report new Ni-NHC complexes derived from Ni(0)-mediated facile C−H activation at the
methyl position of IPr, one of the most commonly used NHC ligands in nickel catalysis. Results
from stoichiometric transformations suggest that such cyclometalation provides a low-energy
access to NHC-ligated Ni(II) hydride species that are envisioned as key reactive intermediates in
many catalytic processes. | en_US |
