Spelling suggestions: "subject:"arganic compounds bsynthesis"" "subject:"arganic compounds csynthesis""
371 |
Synthesis of bisquinolines through conventional and unconventional energy sourcesMakhanya, Talent Raymond January 2011 (has links)
Thesis submitted in fulfilment of the requirements for the Degree of Master of Technology: Organic Chemistry, Durban University of Technology, 2011. / Malaria, the most prevalent parasitic disease, is considered a neglected disease owing to insufficient research and development in synthesis and therapy worldwide. Therapy failures are frequent and are due to a variety of factors such as the intrinsic characteristics of the disease, conditions of transmission, and the difficult control of spreading through tropical areas. Primary factors are the complexity of the parasite life cycle and the development of drug resistance. Another critical factor is the increasing number of immune-compromised patients that suffer from malaria and human immunodeficiency virus (HIV) co-infections. Most of the drugs currently available to treat malaria are quinoline derivatives modelled on the quinine molecule, found in the bark of Cinchona trees. Over the last 50 years the use of quinine has declined owing to the development of synthetic 4-aminoquinolines such as chloroquine. However, the malaria parasite is rapidly becoming resistant to the drugs currently available. Recently bisquinoline compounds were found more potent than chloroquine against both chloroquine-sensitive and resistant strains of malaria; this improved efficacy and prompted an increased interest in the design of these anti-malarial drugs. Although several synthetic methods are available to synthesise bisquinolines, we report the synthesis of bisquinolines from simple, readily available and cost- effective starting compounds. The synthesis was accomplished in four reaction steps using the Claisen condensation, Vilsmeir-Haack reaction, formation of a Schiff
base and thermal cyclization, sequentially. We used a conventional energy source and microwave irradiation for the synthesis, wherever possible, of 2, 4-dichloro-3, 4'-biquinoline and 2, 4-dichloro-7'-methoxy-3, 4'-biquinoline.
In the first step, 3-acyl-2, 4-dihydroxyquinoline is synthesised from an equimolar mixture of methyl-2-aminobenzoate and ethyl acetoacetate by microwave irradiation for 3 minutes; the yield is 90 % whereas by 6 hours refluxing the yield is 75 %. This is followed by the synthesis of 3-chloro-3-(2,4-dichloroquinolin-3yl) acrylaldehyde, by combining DMF and POCl3 at 00C to form the electrophile which reacts with 3-acyl-2,4-dihydroxyquinoline under microwave irradiation for 5 minutes; the yield is 65 % whereas by 6 hours refluxing the yield is 50 %. In the next step, several protocols to prepare a Schiff base 3-chloro-3-(2, 4-dichloroquinolin-3-yl) allylidene aniline are investigated with the best yield of 75% obtained by microwave irradiation for 5 minutes. Subsequently three aniline derivatives viz, 4-methoxyaniline, 4-chloroaniline and 4-methylaniline, are used as substrate to prepare 3-chloro-3-(2,4-dichloroquinolin-3-yl) allylidene-4-methoxyaniline, 3-chloro-3-(2 ,4-dichloroquinolin-3-yl) allylidene-4-methylaniline and 3-chloro-3-(2, 4-dichloroquinolin-3-yl) allylidene-4-chloro aniline at 68, 78 and 64 % yield, respectively. In the final step, 2, 4-dichloro-3, 4'-biquinoline is prepared; several methods were investigated, however, the best yield is 24 % which is obtained under alkaline conditions in the presence of K2CO3 and DMF by microwave irradiation for 10 minutes. The 2, 4-dichloro-7'-methoxy-3, 4'-biquinoline derivative is also prepared in 18 % yield under the same alkaline conditions. The outline of the total synthesis of bisquinoline is presented graphically below. / National Research Fund.
|
372 |
Tin-bemiddeling van inositolderivatiseringPrinsloo, Mare-Loe 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The aim of this thesis is to use tin-mediated reactions to differentiate between the four
zones in the myo-inositol ring that consists of five contiguous equatorial and one axial
hydroxyl groups. It is expected to give chemical control over the hexitol that can be
put to good use in commercializing the phosphate derivatives of myo-inositol that are
of pharmaceutical value.
As point of departure 1,2-0-cyclohexylidene-myo-inositol (II.I) was synthesized that
contains a tetrol with one end adjacent to an axial acetal oxygen and the other end
adjacent to an equatorial acetal oxygen. The selective protection of position 3 (Dmyo-
inositol) was investigated. Various problems lead to the selective silylation of
the acetal at position 5. The silane forms the basis of the subsequent investigation
because the cyclitol is now divided into an isolated mono-ol and a trans-diol allowing
for easier differentiation between the various hydroxyl groups.
It was indeed possible to differentiate the trans-diol from the mono-ol by using
carbonylation and allylidenation. Ring closure occurs in both cases. In the
carbonylation case the resultant five-membered ring is less stable than that of the
allylidene due to the Sp² hybridized carbon atom of the carbonate compared to theSp³
hybridized carbon of the allylidene group.
Preliminary work was done on the racerrue 1,2-0-cyclohexylidene-myo-inositol
(II.VII) in order to use the acquired technology on the chiral camphor analog. The
transition from racemic to chiral proved problematic since the camphor acetal is
difficult to prepare and its selective silylation differs from that observed for
cyc1ohexylidene. The camphor acetal itself was silylated in the process.
(S)-( -)-Camphanic chloride was therefore used as chiral auxiliary in the protection of
position six of the racemic 1,2,3,4,5-protected myo-inositol, thus solving the problems
encountered in the protection of position six whilst combining the protection and
chiral induction steps. The resultant diastereomers could both be used in the synthesis
of IP₃ and IP₄ respectively, eliminating the disposal of half ofthe product. This project lead to the development of useful chiral differentially protected myoinositol
derivatives, which could be useful in synthesis of various other myo-inositol
derivatives.
Besides the synthesis of useful chiral differentially protected myo-inositol derivatives,
this investigation developed new applications in the tin-mediated derivatization of
sugars.
The following compounds were synthesized during this investigation. Bold numbers
indicates novel compounds. / AFRIKAANSE OPSOMMING: Die doel van hierdie proefskrif is om met behulp van tin-bemiddelde reaksies
onderskeid te maak tussen die vier sones in die mia-inositolring, wat bestaan uit vyf
aaneenlopende ekwatoriale hidroksigroepe en een aksiale hidroksigroep. Die
verwagting was om vinnig, effektiewe chemiese beheer oor die genoemde heksitol te
verkry om sodoende chemies en kommersiëel munt te slaan uit die farmaseutiese
werking van die fosfaatafgeleides van mia-inositol.
As eerste uitgangspunt is 1,2-0-sikloheksilideen-mia-inositol (II.I) berei, wat lei tot
die vorming van 'n tetrol waarvan die een punt naasliggend aan 'n aksiale
asetaalsuurstofatoom en die ander punt naasliggend aan 'n ekwatoriale asetaalsuurstof
is. As voortsetting is die selektiewe beskerming van posisie 3 (D-mia-inositol)
ondersoek. Velerlei probleme lei tot die selektiewe sililering van die asetaal by
posisie 5 (II.VII). Die silieleter vorm die basis van al die daaropvolgende ondersoeke
omdat dit die siklitol in 'n trans-diol en 'n geïsoleerde mono-ol verdeel en die
verskillende hidroksigroepe daarvan makliker van mekaar onderskei kan word.
Dit is inderdaad moontlik om die trans-diol van die mono-ol te onderskei deur
karbonilering of allilidenering. In albei gevalle vind ringannulering plaas. In die
geval van die karbonilering is die gevormde vyflidring minder stabiel as wat die geval
is vir die allilideengroep. Die rede hiervoor is dat die karbonaatkoolstofatoom Sp²-
gehibridiseer is terwyl die ooreenstemmende koolstofatoom van die allilideen Sp³-
gehibridiseer is.
Ontwikkelingswerk is op die rasemiese 1,2-0-sikloheksilideen-mia-inositol (II.VII)
gedoen ten einde dit op die chirale kamferasetaalanaloog toe te pas. Die oorgang van
rasemies na chiraal is egter problematies aangesien die kamferasetaal moeiliker vorm
en selfs as dit vorm toon die reaksies, soos byvoorbeeld die sililering, ander
selektiwiteit as wat die geval is vir die rasemiese mengsel. Sililering van die
kamferasetaallei tot sililering van die kamfer self.
(S)-(-)-kamfanoïelchloried is gevolglik as chirale hulpreagens gebruik om posisie 6
van die rasemiese 1,2,3,4,5-beskermde-mia-inositol te beskerm. Hierdie benadering los die problematiek rondom die beskerming van posisie 6 sowel as die induksie van
chiraliteit op. Die twee diastereomere wat op hierdie wyse vorm, kan albei in die
sintese van onderskeidelik IP₃ en IP₄ gebruik word, wat die verlies aan helfte van die
produk verhoed.
Behalwe die daarstelling van bruikbare chirale differensiëel-beskermde mioinositolafgeleides
wat gebruik kan word om 'n verskeidenheid chirale mioinositolafgeleides
te berei, het hierdie ondersoek nuwe toepassings in tin-bemiddelde
derivatisering van suikers daargestel.
Die volgende verbindings is gedurende die verloop van hierdie ondersoek
gesintetiseer, waar verbindings vir die eerste keer gesintetiseer is word dit aangedui
deur die verbinding se nommer vet (bold) te druk.
|
373 |
Sintese en spektroskopiese eienskappe van kruisgekonjugeerde diesters. Deel IIWoitkowiak, T. B. A. 03 1900 (has links)
Digitized from microfiche to pdf. / Please refer to full text.
|
374 |
Elektrofiele addisiereaksies in die sintese van hormone en feromoneVisagie, Hester E. 03 1900 (has links)
Digitized from microfiche to pdf format. / Thesis (PhD (Chemistry))--University of Stellenbosch, 1977. / Please refer to full text.
|
375 |
Evolving complex systems from simple moleculesSadownik, Jan January 2009 (has links)
Until very recently, synthetic chemistry has focussed on the creation of chemical entities with desirable properties through the programmed application of isolated chemical reactions, either individually or in a cascade that afford a target compound selectively. By contrast, biological systems operate using a plethora of complex interconnected signaling and metabolic networks with multiple checkpoint controls and feedback loops allowing biological systems to adapt and respond rapidly to external stimuli. Systems chemistry attempts to capture the complexity and emergent phenomena prevalent in the life sciences within a wholly synthetic chemical framework. In this approach, complex phenomena are expressed by a group of synthetic chemical entities designed to interact and react with many partners within the ensemble in programmed ways. In this manner, it should be possible to create synthetic chemical systems whose properties are not simply the linear sum of the attributes of the individual components. Chapter 1 discusses the role of complex networks in various aspects of chemistry- related research from the origin of life to nanotechnology. Further, it introduces the concept of Systems chemistry, giving various examples of dynamic covalent networks, self-replicating systems and molecular logic gates, showing the applications of complex system research. Chapter 2 discusses the components of replicator design. Further, it introduces a network based on recognition mediated reactions that is implemented by length- segregation of the substrates and displays properties of self-sorting. Chapter 3 presents a fully addressable chemical system based on auto- and cross- catalytic properties of product templates. The system is described by Boolean logic operations with different template inputs giving different template outputs. Chapter 4 introduces a dynamic network which fate is determined by a single recognition event. The replicator is capable of exploiting and dominating the exchanging pool of reagents in order to amplify its own formation at the expense of other species through the non-linear kinetics inherent in minimal replication. Chapter 5 focuses on the development of complex dynamic systems from structurally simple molecules. The new approach allows creating multicomponent networks with many reaction pathways operating simultaneously from readily available substrates.
|
376 |
Synthesis and redox behaviour of some tetramine complexes of rutheniumIII and iridium III鄧天祐, Tang, Tin-wu. January 1982 (has links)
published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
|
377 |
Synthesis of heterocycles via phenylseleno group transfer radical cyclization and chemoselective reductive amination promoted by InCl3李安怡, Lee, On-yi. January 2007 (has links)
published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy
|
378 |
Development of new polymer-supported reagents for organic synthesis, solvent effects in samarium promoted allylic alcohol cyclopropanationreactions and time resolved resonance studies of the photodeprotectionof p-hydroxyphenacyl caged phototrigger compoundsKan, Tze-wai, Jovi., 簡紫慧. January 2006 (has links)
published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy
|
379 |
Ruthenium porphyrins and dirhodium (II, II) carboxylates catalyzed ylide-mediated cycloadditions and carbenoid transfer reactionsZhou, Congying., 周聰穎. January 2004 (has links)
published_or_final_version / abstract / toc / Chemistry / Doctoral / Doctor of Philosophy
|
380 |
Application of the Nazarov cyclization reaction to the synthesis of guanacastepenes and taiwaniaquinoidsLi, Shuoliang., 李碩梁. January 2006 (has links)
published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy
|
Page generated in 0.0603 seconds