DOI

10.17077/etd.ht7fgz3v

Document Type

Dissertation

Date of Degree

Summer 2017

Access Restrictions

.

Degree Name

PhD (Doctor of Philosophy)

Degree In

Chemistry

First Advisor

Pigge, F. C.

First Committee Member

Wiemer, David F.

Second Committee Member

Nguyen, Hien M.

Third Committee Member

Forbes, Tori Z.

Fourth Committee Member

Tivanski, Alexei V.

Abstract

Aza-heterocycles such as pyridines, imidazoles, piperidines, etc. are ubiquitous structural motifs found in various natural products and pharmacologically active compounds. Thus, they are of unparalleled importance to synthetic, medicinal, and materials chemists. Despite their structural significance, organic transformations available for the functionalization of these heterocycles remain underdeveloped. The development of several synthetic methods to construct aza-heterocyclic building blocks is described in this thesis, which, in turn, should facilitate the assembly of more elaborate frameworks present in bioactive molecules.

An intramolecular palladium catalyzed Mizoroki-Heck cyclization of 4-alkylidene dihydropyridines with tethered aryl iodide electrophiles is demonstrated. This provides access to substituted isoindolinones and oxindoles in high yields. An asymmetric variant of this reaction using chiral phosphine ligands delivers enantioenriched oxindoles and isoindolinones. Additionally, an intramolecular Mizoroki-Heck reaction for the synthesis of 2-substituted pyridine derivatives is also developed. An array of fused isoindolinones is constructed as a mixture of diastereomers and further manipulated using chemical transformations to yield the corresponding pyridine and piperdine derivatives.

Moreover, a formal [3+2] cyclocondensation of alkylidene dihydropyridines and aryl diazonium salts has been discovered for the synthesis of triazole derivatives. Tertiary amides deliver substituted 1,2,4-triazolium salts, whereas, secondary amides provide substituted, neutral 1,2,4-triazoles in excellent yields, under mild reaction conditions.

Furthermore, an intramolecular direct arylation of 2- and 4-substituted alkylpyridines is developed for the synthesis of 2,3- and 3,4-cyclized pyridines. It is shown that 4-alkylpyridines tethered to aryl halides participate in a palladium catalyzed direct arylation to give fused 7-membered lactams in excellent yields.

Lastly, an intramolecular cyclization of 1,2-alkylimidazoles is reported. Alkylidene imidazolines tethered to electrophilic keto-amide sidechains participate in an aldol-like reaction to yield γ-lactam products in good yields as mixtures of diastereomers.

Keywords

Anhydrobases, Aza-heterocycles, Heck reaction, Pyridines, Triazoles

Pages

xviii, 421 pages

Bibliography

Includes bibliographical references (pages 410-421).

Copyright

Copyright © 2017 Madhur Satish Joshi

Included in

Chemistry Commons

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