Rhodium(III)-catalyzed amide-directed C-H activation and [4+2] cycloaddition for modular assembly of nitrogen heterocycles
Date
2017
Authors
Semakul, Natthawat, author
Rovis, Tomislav, advisor
Kennan, Alan, committee member
Shi, Yian, committee member
McCullagh, Martin, committee member
Kipper, Matt, committee member
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Abstract
This dissertation describes the ligand and reaction developments by amide-directed rhodium(III)-catalyzed C(sp2)-H bond activation followed by amidoannulation with alkenes to form nitrogen-containing heterocycles. Chapter 1 details the ligand development for stereoselective synthesis of [4.1.0] dihydroisoquinolones through benzamidation of cyclopropenes mediated by Rh(III) catalysis. Quantum chemical calculations revealed the important role of heptamethylindenyl (Ind*) ligand and O-substituted ester of benzhydroxamate for achieving high diastereoselectivity in cyclopropene insertion. Efforts toward stereoselective synthesis of [4.1.0] dihydroisoquinolones have been also studied by streptavidin-based artificial metalloenzyme. Chapter 2 presents the stereoselective synthesis of [4.2.0] dihydroisoquinolones via the benzamidation of cyclobutenes. The transformation proved to have a broad substrate scope and functional group tolerance that generates the cyclobutane-fused azacycles with excellent diastereoselectivity. The artificial metalloenzymes can render this reaction asymmetric furnishing the dihydroisoquinolone products in moderate enantioselectivity. Chapter 3 communicates Rh(III)-catalyzed C-H activation and [4+2] annulation reaction of N-pivaloyloxy acrylamides with alkenes for an efficient synthesis of α,β-unsaturated-δ-lactams. This process offers a platform for the rapid assembly of a diverse set of delta-lactams from simple and abundant precursors. These lactams could serve as useful building blocks to access substituted piperidines.
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Subject
amides
heteroannulation
rhodium(III) catalysis
C-H activation
alkenes
N-heterocycles