45 research outputs found
Developing Methodologies for the Synthesis of Heterocyclic Libraries: Parallel Synthesis of Flavours, Maleimides, alpha-beta-Unsaturated-gamma-Butryrolactams and Isoquinolines
No full textTitle: Developing Methodologies for the Synthesis of Heterocyclic Libraries: Parallel Synthesis of Flavons, Maleimines, α-β-Unsaturated-γ-Butyrolactams and Isoquinolines, Author: Emelia Awuah, Location: MillsParallel synthesis technologies that allow for rapid generation of compound
collections that can be screened and quickly provide useful structure-activity
relationships are needed to probe and understand biological systems. Synthetic strategies
that are robust and allow the rapid access to a library of flavones, maleimides, α-β-unsaturated-γ-butyrolactams and isoquinolines are described. A Pd2(dba)3.CHCl3 catalyst system incorporating the 1,3,5,7-tetramethyl-2,4,8-
trioxa-6-phenyl-6-phosphaadamantane (PA-Ph) ligand permits the generation of a library
of substituted flavones via sequential microwave-assisted copper free Sonogashira and
carbonylation annulation reactions under mild conditions. Application of this protocol is
described for several aryl iodides and bromides with TMS-acetylenes allowing for the
"one pot" synthesis of a diverse collection of substituted flavones. Synthetic strategies that led to the generation of libraries of bisaryl-maleirnides,
anilinoaryl-maleimides and bisanilino-maleimides as well as bisaryl substituted α-β-unsaturated-γ-butyrolactams are described. The reaction protocol also takes advantage of
Pd-cross-coupling reactions using the catalytic system mentioned above as well as
Michael addition / elimination reactions. Reaction conditions that allow for the control
necessary for the synthesis of a library of symmetrical and non-symmetrical 3,4-
disubstituted maleimides from N-(p-methoxybenzyl)-3,4-dibromomaleimide as well as
symmetrical and non-symmetrical 3,4-disubstituted α-β-Unsaturated-γ-Butyrolactams from 3,4-dibromo-1-(4-methoxybenzyl)-1H-pyrrol-2(5H)-one are presented. Protocol for facile deprotection of the p-methoxybenzyl group to generate the final products of both
3,4-disubstituted maleimides and 3,4-substituted α-β-unsaturated-γ-butyrolactams is also
described. A robust parallel synthetic strategy that makes use of simple, cheap and readily
available precursors is described for the preparation of a library of substituted
isoquinolines. The approach involves microwave-assisted Pictet-Spengler and Bischler-Napieralski
cyclizations. In addition, a Pd-catalyzed cross-coupling reaction protocol
using the Pd/PA-Ph provides access to a diverse collection of C1 and C4 substituted
isoquinolines via the activation of an isoquinolin-1 (2H)-one scaffold. A protocol for the Pd- catalyzed α-arylation of active methylene compounds using
the palladium complex of 1,3,5,7-tetramethyl-6-(isobutyl)-2,4,8-trioxa-6-phosphaadamantane
(P A-iBu) to generate products that served as precursors for a diverse
collection of substituted isoquinolines is also described.ThesisDoctor of Philosophy (PhD
Caroline Emelia Stephen
No full textExcerpt: Caroline Emelia Stephen, born on December 8, 1834, was notable for a number of reasons. Her connections were impressive: she was the unmarried daughter of Sir James Stephen (the noted Under-Secretary for the Colonies in 1836-1847), the sister of Leslie Stephen (author of the Oxford Dictionary of National Biography), sister-in-law to Minny Thackeray Stephen and Anny Thackeray Ritchie (daughters of William Makepeace Thackeray), and aunt to Virginia Woolf and Vanessa Bell. Her grandfather, also Sir James Stephen, wrote the legislation that ended slavery in England. Known as a Quaker mystic, she is credited with bringing about the revival of the Society of Friends in the latter part of the nineteenth century through writings about her conversion
ChemInform Abstract: Strategies and Synthetic Methods Directed Toward the Preparation of Libraries of Substituted Isoquinolines.
No full textStrategies and Synthetic Methods Directed Toward the Preparation of Libraries of Substituted Isoquinolines
No full textChemInform Abstract: Access to Flavones via a Microwave‐Assisted, One‐Pot Sonogashira—Carbonylation—Annulation Reaction.
No full textDevelopment of Methods for the Synthesis of Libraries of Substituted Maleimides and α,β-Unsaturated-γ-butyrolactams
No full textAssessing the Challenges to Sustainable Mining: A Supply Chain Perspective (A Case of Li Tong Mining Company in Ghana)
No full textThe mining industry contributes significantly to the economic growth of the country however frequent occurrences of collapsed pits, less regard for the disposal of waste into river bodies, poor service conditions to staff of small- scale mining companies and poor corporate social responsibility to mining communities have raised a lot of international concerns. These challenges can be highly minimized when the mining industry shifts from unsustainable patterns of operations. The high cost of sustainable operations and many other challenges are key de-motivational challenges to the adoption of sustainable practices.The study revealed that management and staff of the industry have little knowledge in sustainable mining practices whilst others perceive a low senior management support. The researchers found a positive effect of the challenges on their inability to practice sustainability and recommend a periodic rigorous training for all staff and management of all small scale mining companies and also recommend that the Minerals and Mining Act and the Environmental Protection Agency (EPA) Act are implemented to the later
Development of Methods for the Synthesis of Libraries of Substituted Maleimides and α,β-Unsaturated-γ-butyrolactams
No full textSynthetic methods for the preparation of maleimide and α,β-unsaturated-γ-butyrolactam compound collections are described. These routes take advantage of Pd cross-coupling and conjugate addition/elimination reactions to permit the facile production of bisaryl-maleimides, anilinoaryl-maleimides, and bisanilino-maleimides while allowing control over the synthesis of symmetrical or nonsymmetrical derivatives. Similarly, the chemistry developed allows for the generation of bisaryl substituted α,β-unsaturated-γ-butyrolactams. The scope and limitations of the approaches are presented
Access to Flavones via a Microwave-Assisted, One-Pot Sonogashira−Carbonylation−Annulation Reaction
No full textPalladium complexes of 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phosphaadamantane are shown to be effective catalytic systems facilitating the sequential application of a microwave-assisted Sonogashira and carbonylative annulation reaction for the preparation of substituted flavones
Strategies and Synthetic Methods Directed Toward the Preparation of Libraries of Substituted Isoquinolines
No full textStrategies for the production of substituted isoquinoline libraries were developed and explored. Routes involving microwave-assisted variants of the Bischler−Napieralski or Pictet−Spengler reaction allowed for cyclization of substituted β-arylethylamine derivatives. The dihydroisoquinolines and tetrahydroisoquinolines thus generated could then be oxidized to their corresponding isoquinoline analogues. An alternate strategy, however, involving the preparation and activation of isoquinolin-1(2H)-ones is demonstrated to be a more practical, rapid, and efficient route to C1- and C4-substituted isoquinoline libraries
