Gold-catalyzed Transformations of Alkynes into Highly Functionalized Heterocycles via Atom-economy Process
| Autor: | Sahani, Rajkumar Lalji, 瑞吉 |
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| Rok vydání: | 2017 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 105 This dissertation describes development of new synthetic organic transformation using gold and silver catalysts. The use of these metals enable mild, selective and efficient transformation to give a range of heterocyclic products from readily available substrates. This thesis is divided into four chapters for ease of understanding. Chapter one is comprised of Gold-catalyzed cycloadditions of ynamides with azidoalkenes or 2H-azirines to give [3+2]- or [4+3]-cycloadducts in three classes. Cycloadditions of ynamides with 2H-azirine species afford pyrrole products in two regioselectivities, when the Cβ-substituent 2H-azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron-rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3]-cycloadditions to deliver 1H-benzo[d]-azepine products instead. Chapter two is comprised of Gold-catalyzed [4+n]-annulations (n = 3, 4) of tert-butyl propiolate derivatives with epoxides or oxetanes to yield seven- or eight-membered oxacyclic products efficiently. In the context of the [4+3]-annulations, product analysis reveals a retention of stereochemistry in an intramolecular SN2 attack of an epoxide. We also report a [4+5]-annulation between one tert-butyl propiolate and γ-lactol, to manifest the utility toward medium-sized rings. Chapter three is comprised of development of two new gold-catalyzed annulations of isoxazoles with propiolates. Most isoxazoles follow an initial O-attack at alkynes to afford [4+1]-annulation products; this process results in a remarkable alkyne cleavage of initial propiolates. Unsubstituted isoxazoles proceed through a N-attack regioselectivity to yield formal [2+2+1]/[4+2]-annulation products. We postulate that these two annulation products arise initially from two seven-membered heterocyclic intermediates, further preceding to products. Chapter four is comprised of a distinct gold-catalyzed annulation between anthranils and propiolates. Most of anthranils and propiolates follow a O-attack pathway to enable [4+2]-annulations, yielding oxireno[2,3-c]quinoline-2-carboxylates; Some propiolates and anthranils having electron rich substitutions resulted in quinolone and quinolin-4(1H)-one derivatives. One-pot synthesis of highly oxygenated tetrahydroquionolines from anthranils and propiolates is also achived through relay catalysis with Au(I) and Zn(II) catalysts. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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