Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 20 for “"Radical Cyclization"”.
-
Radical cyclization approach to a chemoenzymatic synthesis of morphine
… as a model for use in the well-known Bergman cyclization reaction as a "latent benzene reagent". Bergman cycloaromatization of similar enediynes has been demonstrated and the cyclization temperatures to form the benzenoid diradicals lies in the region 40-70°C. Cache molecular modeling of …
-
Asymmetric Total Synthesis of the Pentacyclic Indole Alkaloid (+)-Tacamonine
… of our approach based on the use of key radical cyclization methodology to ultimately accomplish a total synthesis of the target. An investigation of the diastereoselectivity displayed in the radical cyclization step is also described through computational methods. Our route followed a …
-
Model Studies Towards the Total Synthesis of Lyconadin A via An Acyl Radical Cascade Reaction
… of Lyconadin A was proposed via an acyl radical cascade reaction. To investigate the possibility and stereoselectivity of the cascade cyclization, phenyl selenoester 16 was chosen as a model substrate to study the 7-exo-5-exo radical cyclization. A synthetic route to phenyl selenoester 16 …
-
Synthesis of Dimeric Pyrrole-Imidazole Alkaloids
… challenges. A manganese(III)-mediated oxidative radical cyclization has been developed to construct the core skeleton of these pyrrole-imidazole dimers and its mechanism is investigated by the methods of computational chemistry. Ent-15-epi-5,11-dioxomassadine has been synthesized by using a …
-
Radical decarboxylation strategies for the synthesis of nitrogen-containing heterocycles
… this thesis describes the use of novel delayed radical precursors in Mn (OAc)3·2H2O mediated oxidative radical cyclization-fragmentation-dimerization processes from Banilides. The first part presents a sequential oxidative radical cyclization-decarboxylative-dimerization process from β-oxoacids, …
-
Total synthesis of Galbulimima alkaloids. Resin-bound glycosyl phosphates as glycosyl donors.
… introduction of the C-ring via radical cyclization chemistry followed by an enamine-ketone addition for construction of the CDE-ring system allowed rapid entry to the pentacyclic core of these alkaloids. The absolute stereochemistry of natural (-)-galbulimima alkaloid 13 is now …
-
Transition Metal-Mediated Higher-Order Cycloaddition Reactions: Application To The Total Synthesis Of Complex Natural Products
… [6ð + 2ð] cycloaddition reaction and a radical cyclization reaction.</p>
-
Studies towards the syntheses of the citreamicins
… reaction was accomplished. Finally, a novel acyl radical cyclization was employed to construct the pentacyclic core of citreamicin η under mild reaction conditions.
-
Predicting Chemical Reactions at the MechanisticLevel through Deep Reinforcement Learning
… pre-trained on an open database of elementary radical reactions (RMechDB). Then, we use proximal policy optimization (PPO) to fine-tune the model and predict reasonable reaction mechanisms for two case studies: a radical oxidation of the terpene limonene, and a radical cyclization cascade in …
-
1. Chromium(0)- Promoted Higher Order Cycloaddition Reactions: Studies Toward The Total Synthesis Of The Cyclocitrinols And Echinopines A And B 2. Total Synthesis Of (±)-Debromoflustramine B Via [4+1] Cyclization Of An Indole Isocyanate And A Bis(alkylthio)carbene
… [6p+2p] cycloaddition, followed by a novel radical cyclization with a cyclic conjugated diene, in only five steps.</p> <p>A novel [4+1] cyclization of an indole isocyante and bis(alkylthio)carbene has been used for an efficient and protecting group free total synthesis of …
-
Biomimetic synthesis of meroterpenoid natural products using dearomatization strategies
… key biomimetic synthetic step was an oxidative radical cyclization cascade reaction, where four new carbon-carbon bonds, four new carbocyclic rings and five new stereocentres were formed in the one step. The first total synthesis of merochlorin A was achieved in five linear steps from …
-
Towards a Formal Total Synthesis of Triptolide Via a Gold-catalyzed Cyclization Cascade
… core of triptolide using a gold-catalyzed cyclization cascade reaction. We explored a number of synthetic routes towards a common linear precursor, and our successes and failures are discussed herein. We also report numerous unsuccessful efforts towards an oxidative gold-catalyzed …
-
Total synthesis of Class II and Class III Galbulimima Alkaloids
… in the form of the necessary C16-enone. A vinyl-radical cyclization secured the C-ring while successful execution of our strategy for introduction of the CDE-ring system in complex galbulimima alkaloids provided the target pentacycle with complete diastereoselection. II. Total Synthesis of …
-
Studies on Syntheses of 1-Azaspirocycles, 2,6-Disubstituted 3-Piperidinols and cls-Decahydroquinolines
… were prepared by employing a 6-exo-trig free-radical cyclization reaction as the key step. The stereoselectivity observed in the free-radical cyclization step was found to be governed by allylic 1,2-strain arising from the interaction of the N-(p-methoxybenzyl) group and the C6 substituent in …
-
Synthetic Efforts Toward Hypoestoxide, Platensimycin, And Guttiferone G
… by using relay ring closing metathesis, and post-cyclization modifications were controlled by the shape of the molecule. Platensimycin is a recently isolated natural product produced by Streptomyces platensis. It was discovered in a novel antibiotic assay by screening a large number of South …
-
I. Radical Cyclizations Mediated by Transition Metal Hydrides II. Study toward the Total Synthesis of Pluraflavin A III. Cytoprotective Polyacetylenes Inspired by Panaxytriol
The first part of the thesis describes radical cyclizations mediated by transition metal hydrides. CpCr(CO)₃H and (H₂O)₂Co(dmgBF₂)₂ under H₂ gas catalyzed the radical cyclization of 1,6-dienes to form 5- and 6-membered rings and the cyclization of a 1,6,11 triene to form a substituted decalin. …
-
Application of Mn(III) Oxidative Cyclizations to Natural Product Synthesis
… a brief review of manganese(III) acetate free radical oxidative cyclization chemistry and its application toward functionalizing nitrogen containing heterocycles. Exploration of a cyclopropane ring opening reaction using indoline, and subsequent manganese(III) cyclization chemistry will be …
-
An Acyl Radical Cascade Model for the Total Synthesis of Lyconadin A
… to 1 based on a novel 7-exo-trig/6-exo-trig acyl radical cascade cyclization. The synthesis of model acyl radical cascade precursor 23 will be presented. Key features of this synthesis include the suppression of competing elimination during the alkylation of a hindered phenethyl bromide and the …
-
Assessment of Reactivity Descriptors for the Study of Chemical Reactions
… The largest group of applications concerns radical reactions. The majority of them occur during the formation of coke, which is a side process of thermal cracking of hydrocarbons. Radical systems are particularly interesting and challenging. However so far only a handful of papers examined …
-
A Radical Approach to Syntheses and Mechanisms
The critically important nature of radical and radical ion mechanisms in biology and chemistry continues to be recognized as our understanding of these unique transient species grows. The work presented herein demonstrates the versatility of kinetic studies for understanding the elementary chemical …