Visible Light Photocatalyzed Redox-Neutral Organic Reactions and Synthesis of Novel Metal-Organic Frameworks

274 Pages·2017·12.32 MB·English

by  Basudev Sahoo (auth.)

Springer Theses
Recognizing Outstanding Ph.D. Research
Basudev Sahoo

Visible Light
Photocatalyzed
Redox-Neutral Organic
Reactions and
Synthesis of Novel
Metal-Organic
Frameworks
Springer Theses
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Basudev Sahoo
Visible Light Photocatalyzed
Redox-Neutral Organic
Reactions and Synthesis
of Novel Metal-Organic
Frameworks
Doctoral Thesis accepted by
ü
University of M nster, Germany
123
Author Supervisor
Dr. Basudev Sahoo Prof. FrankGlorius
Angewandte Homogenkatalyse Organisch Chemisches Institut Westfälische
LIKAT Rostock Wilhelms-Universität Münster
Rostock Münster
Germany Germany
ISSN 2190-5053 ISSN 2190-5061 (electronic)
SpringerTheses
ISBN978-3-319-48349-8 ISBN978-3-319-48350-4 (eBook)
DOI 10.1007/978-3-319-48350-4
LibraryofCongressControlNumber:2016955421
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To my beloved parents, brothers and
sisters-in-law
’
Supervisor s Foreword
InDr.BasudevSahoo’sthesiswork,conceptuallynovelandsyntheticallyvaluable
methodsweredevelopedusingvisiblelightphotocatalysis.Thisemergingfieldhas
become an indispensable tool for organic synthesis and employs environmentally
benign and abundant visible light in the presence of a photosensitizer as an
attractive alternative to harmful UV light in photo-mediated reactions. During his
doctoral studies, Dr. Sahoo merged the concept of gold catalysis with visible light
photocatalysis in a dual catalytic fashion, demonstrating the compatibility of these
two important and challenging catalytic modes for the first time. This novel dual
catalytic system allowed for the development of mild protocols for the difunc-
tionalization of non-activated alkenes and has since been expanded upon and
employedinfurtherreactionsbyusandothergroups.Moreover,hisknowledgeand
expertise in photocatalysis helped him to develop a novel trifluoromethylation
method which combined radical addition chemistry with a polar rearrangement to
synthesizevaluablefluorinatedcompounds.Theincorporationoffluorinatedgroups
ontoorganicmoleculesisattractingincreasingattentionasthesecompoundsfeature
heavily in pharmaceuticals, agrochemicals, and material research. Since
nitrogen-based heterocycles make a large class of bioactive compounds, a mild
method for the synthesis of indolizine heterocycles was also developed using a
photochemical approach, which has been seldom explored for this class of com-
pound.Duringthisstudy,theproductofthereactionwasfoundtomediateitsown
formation under photochemical conditions. This rarely observed phenomenon
obviated the need for an external photocatalyst and could inspire the future
development of autocatalytic photochemical reactions. In addition to his work on
photocatalysis, he has also been engaged in synthetic work focused on the prepa-
ration of highly porous metal-organic framework (MOF) materials. The scientific
vii
viii Supervisor’sForeword
contributions made by Dr. Sahoo, presented in this thesis, have significantly
acceleratedthedevelopmentofthefieldshehasworkedon,andhaveinspiredmany
new projects in my group.
Münster, Germany Prof. Frank Glorius
April 2016
Abstract
Visible light-mediated photocatalysis has emerged as an environmental friendly
elegant approach for streamlined organic synthesis. Recently, many conceptually
novel and challenging advancements have been accomplished in this growing
research area. The content of this thesis is about the developments of novel
methodologies for synthesis of valuable organic compounds using visible light
photocatalysis as toolbox and also synthesis of novel metal-organic frameworks
(MOFs) as characteristic porous materials.
IninitialphaseofmyPh.D.work,anoveldualcatalyticsystemcombininggold
with visible light photoredox catalysis has been developed for selective intra- and
intermolecular heteroarylation of non-activated alkenes under mild reaction
conditions (Scheme 1.1). In this work, the compatibility of gold catalysis with
photoredox catalysis was demonstrated for the first time. Furthermore, this
methodology benefits from mild reaction conditions and readily available light
sources and avoids the use of strong external oxidants in contrast to previous
methods.
The second part of my Ph.D. work was concentrated on the visible light
photoredox-catalyzed semipinacol rearrangement for trifluoromethylation of
cycloalkanols (Scheme 1.2). This protocol gives access to a novel class of densely
/
R1
N2 Photoredox
R3 Nu
Nu Catalysis
+ or R2 R3
R1
R2 I Gold regioselective,stereoretentive
Ar R3 Catalysis no srotooicmh itoemmepterirca touxried ant
Scheme 1.1 Dual gold and visible light photoredox-catalyzed heteroarylation of non-activated
alkenes
ix
x Abstract
Semipinacol Rearrangement
HO X Photoredox X
( )n Catalysis O ( )nCF
3
( )m ( )m
Y Y
R R
S
OTf
CF
3
Scheme 1.2 Visible light photoredox-catalyzed trifluoromethylation via semipinacol
rearrangement
R3 R3
N EWG
R1 O O External
R1
Photocatalyst N
EWG
N
Br R2
R2
+ No external photocatalyst
+ Product can promote other photoredox reactions
Scheme1.3 Visiblelightphotocatalyticsynthesisofpolycyclicindolizines
functionalized trifluoromethylated cycloalkanones with all carbon quaternary cen-
ters. Interestingly, these reactions proceed via radical–polar crossover followed by
1,2-alkylmigration.Tothebestofourknowledge,thismethodologyrepresentsthe
first report of 1,2-alkyl migration in visible light-mediated photoredox catalysis.
InthirdpartofmyPh.D.work,wehavedevelopedanovelmethodologyforthe
synthesis of valuable polycyclic indolizines under visible light-mediated reaction
conditions (Scheme 1.3). To our delight, these reactions do not need any external
photosensitizing agents in contrast to conventional photocatalysis, but do need
visiblelightirradiation.Variousanalyticalandlaboratoryexperimentsindicatethat
indolizine products are responsible in some way for their own formation, although
further insightful investigations required for complete elucidation of mechanism.
Furthermore,gratifyingly,thisindolizineproductcanpromoteotherphotocatalyzed
reactions in lieu of standard photocatalyst.
InfinalphaseofmyPh.D.work,atriarylboranelinkerwiththreecarboxylicacid
anchoring groups, (4,4′,4″-boranetriyltris(3,5-dimethylbenzoic acid) (H TPB)), has
3
been successfully developed and incorporated into the metal-organic frameworks
along with a linear BDC co-linker to give mixed MOFs, DUT-6 (Boron)
(Scheme 1.4). This new DUT-6 (Boron) showed fluorescent activity and exhibited