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Atropisomeric chromophores as substr...

Vallavoju, Nandini.

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Atropisomeric chromophores as substrates and catalysts for asymmetric light induced transformations.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Atropisomeric chromophores as substrates and catalysts for asymmetric light induced transformations./
作者:	Vallavoju, Nandini.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2016,
面頁冊數:	401 p.
附註:	Source: Dissertation Abstracts International, Volume: 77-10(E), Section: B.
Contained By:	Dissertation Abstracts International77-10B(E).
標題:	Organic chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10118420
ISBN:	9781339797519

Atropisomeric chromophores as substrates and catalysts for asymmetric light induced transformations.
Vallavoju, Nandini.

Atropisomeric chromophores as substrates and catalysts for asymmetric light induced transformations. - Ann Arbor : ProQuest Dissertations & Theses, 2016 - 401 p.

Source: Dissertation Abstracts International, Volume: 77-10(E), Section: B.

Thesis (Ph.D.)--North Dakota State University, 2016.

Photochemical transformations hold a unique place as they can provide access to molecules with unique stereochemical and structurally complex scaffolds, thus serving as a complementary approach to thermal transformations. However, asymmetric photoreactions have been under-explored due to the challenges in controlling the nature of the excited state(s). Various elegant strategies have been developed by chemists to address this bottleneck and achieved varying degrees of success. This dissertation describes a novel and unique strategy that employs atropisomeric thioureas as organo-photocatalysts to perform desired chemical transformations. The motivation of the thesis is to develop an alternative strategy that does not depend on energy/electron transfer processes to initiate the photoreactions. This dissertation describes another unique strategy that employs atropisomeric chromophores where axial chirality in the reactant is transferred to point chirality in the photoproduct(s). This research explains about rotamers control in the ground state that allows stereospecific phototransformations in the excited state(s) thus leading to enantioenriched product(s).

ISBN: 9781339797519Subjects--Topical Terms:

523952
Organic chemistry.

Atropisomeric chromophores as substrates and catalysts for asymmetric light induced transformations.
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245 1 0 $a Atropisomeric chromophores as substrates and catalysts for asymmetric light induced transformations.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2016
300 $a 401 p.
500 $a Source: Dissertation Abstracts International, Volume: 77-10(E), Section: B.
500 $a Adviser: Jayaraman Sivaguru.
502 $a Thesis (Ph.D.)--North Dakota State University, 2016.
520 $a Photochemical transformations hold a unique place as they can provide access to molecules with unique stereochemical and structurally complex scaffolds, thus serving as a complementary approach to thermal transformations. However, asymmetric photoreactions have been under-explored due to the challenges in controlling the nature of the excited state(s). Various elegant strategies have been developed by chemists to address this bottleneck and achieved varying degrees of success. This dissertation describes a novel and unique strategy that employs atropisomeric thioureas as organo-photocatalysts to perform desired chemical transformations. The motivation of the thesis is to develop an alternative strategy that does not depend on energy/electron transfer processes to initiate the photoreactions. This dissertation describes another unique strategy that employs atropisomeric chromophores where axial chirality in the reactant is transferred to point chirality in the photoproduct(s). This research explains about rotamers control in the ground state that allows stereospecific phototransformations in the excited state(s) thus leading to enantioenriched product(s).
520 $a The chapter 1 introduces the fundamental differences between asymmetric photochemical reactions and conventional thermal method. Further, an overview of various methodologies developed towards asymmetric photochemical transformations are detailed.
520 $a In chapter 2 and chapter 3, various thiourea-based organo-photocatalysts were developed for enantioselective intramolecular [2+2] photocycloaddition of coumarin derivatives. The atropisomeric thioureas were found to be efficient in promoting the photocycloaddition leading to the corresponding products with high enantioselectivity (77-96% ee) at low catalyst loading (1-10 mol%). The photocatalytic cycle is proposed to proceed by the mechanism of 'energy sharing' via the formation of both static and dynamic complexes (exciplex formation), which is promoted by hydrogen bonding.
520 $a Chapter 4 describes the intermolecular [2+2]-photocycloaddition of coumarin with tetramethylethylene promoted by thiourea catalysts. The photocatalytic cycle of coumarin mediated by thioureas is proposed to proceed via a combination of minimized aggregation, enhanced intersystem crossing and altered excited state lifetime(s), which is promoted by hydrogen bonding.
520 $a Chapter 5 describes the enantiospecific hydrogen abstraction of atropisomeric enone carboxamides leading to spiro-beta-lactam photoproduct(s). Divergent photoreactivity was observed based on restricted bond rotation(s) in atropisomeric substrates, when compared to their achiral analogue. The hydrogen abstraction also proceeded efficiently under visible light sensitized irradiation.
590 $a School code: 0157.
650 4 $a Organic chemistry. $3 523952
650 4 $a Analytical chemistry. $3 3168300
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710 2 $a North Dakota State University. $b Chemistry and Biochemistry. $3 2097832
773 0 $t Dissertation Abstracts International $g 77-10B(E).
790 $a 0157
791 $a Ph.D.
792 $a 2016
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10118420