scholarly journals Cascade Approaches Towards the Synthesis of Daphnioldhanin A Alkaloid

2021 ◽  
Author(s):  
◽  
Ashna Ashneen Khan
Keyword(s):  
Diazo Compound ◽  
Radical Addition ◽  
Ring System ◽  
Membered Ring ◽  
The Core ◽  
Modelling Studies ◽  
Stability Issues ◽  
Future Work ◽  
Carbon System ◽  
Radical Approach

<p>Daphnioldhanin A 1.6 is a recent alkaloid obtained from Daphyniphyllum plants. The core structure as shown consists of a 5,5,7 tricyclic ring system, which is a challenging ring system and to date has not been reported in any other natural product. This project focussed on using two cascade approaches in forming this ring system, namely radical addition and cyclisation cascade and carbene cycloaddition cyclisation cascade CCCC. Using the radical approach would require a 5-endo trig cyclisation, which is disfavoured by Baldwin's rules, but has been reported in systems which have an hetereoatom (carbonyl, nitrogen or sulfur) incorporated in the ring. In our case, the 5-endo trig cyclisation is needed in an all carbon containing ring, and preliminary modelling studies have shown that the energy for the 4-exo trig cyclisation product is higher than that of the 5-endo trig cyclisation product. Therefore, the radical approach if successful will eventuate in a novel 5-endo trig cyclisation in an all carbon system. However, due to stability issues with the radical precursors this method had to be abandoned and attention focused on the CCCC approach. For the CCCC approach, rhodium catalysed cascade cyclisation is intended on diazo compound 1.22. The presence of the intramolecular double bond enhances the second cyclisation to occur which will form the 5 and 7-membered ring simultaneously along with oxo-bridge resulting in the functionalised pentacyclic ring system which would be very similar to the proposed 5,5,7 core of Daphnioldhanin A. The desired diazo compound could not synthesised due to failure in forming the anhydride for the acid and future work would be focussed on forming acid derivatives in order to form the diazo compound 1.22 before using rhodium catalysed cyclisation to form the functionalised pentacyclic compound.</p>

scholarly journals Cascade Approaches Towards the Synthesis of Daphnioldhanin A Alkaloid

2021 ◽  
Author(s):  
◽  
Ashna Ashneen Khan
Keyword(s):  
Diazo Compound ◽  
Radical Addition ◽  
Ring System ◽  
Membered Ring ◽  
The Core ◽  
Modelling Studies ◽  
Stability Issues ◽  
Future Work ◽  
Carbon System ◽  
Radical Approach

<p>Daphnioldhanin A 1.6 is a recent alkaloid obtained from Daphyniphyllum plants. The core structure as shown consists of a 5,5,7 tricyclic ring system, which is a challenging ring system and to date has not been reported in any other natural product. This project focussed on using two cascade approaches in forming this ring system, namely radical addition and cyclisation cascade and carbene cycloaddition cyclisation cascade CCCC. Using the radical approach would require a 5-endo trig cyclisation, which is disfavoured by Baldwin's rules, but has been reported in systems which have an hetereoatom (carbonyl, nitrogen or sulfur) incorporated in the ring. In our case, the 5-endo trig cyclisation is needed in an all carbon containing ring, and preliminary modelling studies have shown that the energy for the 4-exo trig cyclisation product is higher than that of the 5-endo trig cyclisation product. Therefore, the radical approach if successful will eventuate in a novel 5-endo trig cyclisation in an all carbon system. However, due to stability issues with the radical precursors this method had to be abandoned and attention focused on the CCCC approach. For the CCCC approach, rhodium catalysed cascade cyclisation is intended on diazo compound 1.22. The presence of the intramolecular double bond enhances the second cyclisation to occur which will form the 5 and 7-membered ring simultaneously along with oxo-bridge resulting in the functionalised pentacyclic ring system which would be very similar to the proposed 5,5,7 core of Daphnioldhanin A. The desired diazo compound could not synthesised due to failure in forming the anhydride for the acid and future work would be focussed on forming acid derivatives in order to form the diazo compound 1.22 before using rhodium catalysed cyclisation to form the functionalised pentacyclic compound.</p>

Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

2020 ◽  
Author(s):  
Marat Korsik ◽  
Edwin Tse ◽  
David Smith ◽  
William Lewis ◽  
Peter J. Rutledge ◽  
...  
Keyword(s):  
Heterocyclic Ring ◽  
Ring System ◽  
Substitution Reactions ◽  
Laboratory Notebook ◽  
Polar Solvents ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Core ◽  
Nmr Data

<p></p><p>We have discovered and studied a <i>tele</i>substitution reaction in a biologically important heterocyclic ring system. Conditions that favour the <i>tele</i>-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the <i>in vivo </i>active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium.</p> <p> </p> <p>Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds. </p><br><p></p>

scholarly journals Auction-Based Consensus of Autonomous Vehicles for Multi-Target Dynamic Task Allocation and Path Planning in an Unknown Obstacle Environment

2021 ◽  
Vol 11 (11) ◽  
pp. 5057
Author(s):  
Wan-Yu Yu ◽  
Xiao-Qiang Huang ◽  
Hung-Yi Luo ◽  
Von-Wun Soo ◽  
Yung-Lung Lee
Keyword(s):  
Path Planning ◽  
Task Allocation ◽  
Autonomous Vehicles ◽  
Autonomous Vehicle ◽  
Dynamic Task ◽  
The Core ◽  
Dynamic Task Allocation ◽  
Vehicle Technology ◽  
Future Work ◽  
Complicated Task

The autonomous vehicle technology has recently been developed rapidly in a wide variety of applications. However, coordinating a team of autonomous vehicles to complete missions in an unknown and changing environment has been a challenging and complicated task. We modify the consensus-based auction algorithm (CBAA) so that it can dynamically reallocate tasks among autonomous vehicles that can flexibly find a path to reach multiple dynamic targets while avoiding unexpected obstacles and staying close as a group as possible simultaneously. We propose the core algorithms and simulate with many scenarios empirically to illustrate how the proposed framework works. Specifically, we show that how autonomous vehicles could reallocate the tasks among each other in finding dynamically changing paths while certain targets may appear and disappear during the movement mission. We also discuss some challenging problems as a future work.

scholarly journals Homocoupling Reactions of Azoles and Their Applications in Coordination Chemistry

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5950
Author(s):  
Steffen B. Mogensen ◽  
Mercedes K. Taylor ◽  
Ji-Woong Lee
Keyword(s):  
Coordination Chemistry ◽  
Reaction Mechanisms ◽  
Metal Organic Frameworks ◽  
Ring System ◽  
Membered Ring ◽  
Materials Chemistry ◽  
Structural Class ◽  
Basic Nitrogen ◽  
Metal Organic ◽  
Metal Catalyzed

Pyrazole, a member of the structural class of azoles, exhibits molecular properties of interest in pharmaceuticals and materials chemistry, owing to the two adjacent nitrogen atoms in the five-membered ring system. The weakly basic nitrogen atoms of deprotonated pyrazoles have been applied in coordination chemistry, particularly to access coordination polymers and metal-organic frameworks, and homocoupling reactions can in principle provide facile access to bipyrazole ligands. In this context, we summarize recent advances in homocoupling reactions of pyrazoles and other types of azoles (imidazoles, triazoles and tetrazoles) to highlight the utility of homocoupling reactions in synthesizing symmetric bi-heteroaryl systems compared with traditional synthesis. Metal-free reactions and transition-metal catalyzed homocoupling reactions are discussed with reaction mechanisms in detail.

Untersuchungen zur Ringkontraktion am 1,4-Dithia-2,6-diaza-3,5-diborinan-System/ Studies on Ring Contraction of the l,4-Dithia-2,6-diaza-3,5-diborinane System

1988 ◽  
Vol 43 (8) ◽  
pp. 959-962 ◽  
Author(s):  
Carl Habben ◽  
Anton Meiler ◽  
Stefan Pusch
Keyword(s):  
Mass Spectra ◽  
Ring System ◽  
Membered Ring ◽  
Ring Contraction ◽  
C Nmr

AbstractThe 1,4-dithia-2,6-diaza-3,5-diborinanes 1a-d react with elemental sodium with formation of the 1,3-diaza-2,4-diboretidines 2a-d. By use of more sodium in case of 1 d or 3,5-bis(diethylamino)- 2-cyclohexyl-6-trimethylsilyldiborinane, the 1,3-thiaza-2,4-diboretidines 3 were formed. 3.5-Dimethyl-2,6-bis(trimethylsilyl)-1,4-dithia-2,6-diaza-3,5-diborinane gives the borazine 4, The reaction of di-t-butyl-sulfurdiimide with 2,6-di-t-butyl-3,5-dimethyl-1,4-dithia-2,6-diaza-3,5-diborinane leads by ring contraction to the four-membered ring system 5. 1H, 11B, 13C NMR and mass spectra are reported and discussed.

Reaktion von N-Trimethylsilyl-N′(N″ -trimethylsilylammodiphenylphosphoranylidenimino) sulfamid mit Wolframoxitetrachlorid und die Struktur von (Cl3WNPPh2N)2 Reaction of N-Trimethylsilyl-N′(N″ -trimethylsilylaminodiphenylphosphoranylidene)sulfamide with Tungstenoxitetrachloride and the Structure of (Cl3WNPPh2N)2

1992 ◽  
Vol 47 (2) ◽  
pp. 171-174 ◽  
Author(s):  
H. W. Roesky ◽  
T. Raubold ◽  
M. Noltemeyer ◽  
M. Witt ◽  
R. Bohra
Keyword(s):  
Molecular Structure ◽  
Structure Analysis ◽  
Ring System ◽  
Membered Ring ◽  
X Ray

1The reaction of ClSO2N = PPh2Cl () with NH3 yields H2NSO2N = PPh2NH2 (2).This compound is converted to Me3Si(H)NSO2N = PPh2N(H)SiMe3 (3) by Me3SiNMe2. 3 reacts with WOCl4 under elimination of (Me3Si)2O and ClSO2NH2 to yield the eight-membered ring system (Cl3WNPPh2N)2 (4).The molecular structure of 4 was investigated by an X-ray structure analysis.

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