The document summarizes Pieter Otten's research publications and patents related to using phosphine oxides as reagents for synthesizing thioamides, selenoamides, and other organosulfur and organoselenium compounds. It also describes Otten's work developing fluorescent indicators for measuring magnesium and calcium ions intracellularly and designing NMR-active reporter molecules for detecting gene expression.
The [2,3]-Wittig rearrangement is a special class of [2,3]-sigma tropic rearrangement which involves an α-oxy carbanions as the migrating terminus to afford various types of homoallylic alcohols.
This PPT is usefull for aspirants of JEE-IIT, CSIR-NET and UPSC exams in CHEMISTRY section. It is also usefull for grduates and Post graduates students of Indian Universities.
The [2,3]-Wittig rearrangement is a special class of [2,3]-sigma tropic rearrangement which involves an α-oxy carbanions as the migrating terminus to afford various types of homoallylic alcohols.
This PPT is usefull for aspirants of JEE-IIT, CSIR-NET and UPSC exams in CHEMISTRY section. It is also usefull for grduates and Post graduates students of Indian Universities.
Cross-Coupling of Unactivated Arenes: Direct Arene C-H Bond Arylation (Concepts of C-H Activation/Functionalization and its Recent Developments), Importance in the Drug Discovery Research
Isotopes are two atoms of the same element that have the same number of protons but different numbers of neutrons. Isotopes are specified by the mass number.
The video lecture for this presentation is available at the following link on YouTube
https://youtu.be/3sxal579RNM
The presenation will be useful for Ug/PG (Chemistry) students
Cross-Coupling of Unactivated Arenes: Direct Arene C-H Bond Arylation (Concepts of C-H Activation/Functionalization and its Recent Developments), Importance in the Drug Discovery Research
Isotopes are two atoms of the same element that have the same number of protons but different numbers of neutrons. Isotopes are specified by the mass number.
The video lecture for this presentation is available at the following link on YouTube
https://youtu.be/3sxal579RNM
The presenation will be useful for Ug/PG (Chemistry) students
Green Chemistry Catalysts for Transfer Hydrogenation Reactions: Synthesis, ch...Karam Idrees
The poster that I presented at the 253rd American Chemical Society National Meeting and Exposition in San Francisco,
CA. It highlights some of my research at Millersville University under the mentorship of Dr. Edward Rajaseelan.
Synthesis, Spectroscopic study & Biological Activity Of Some Organotin(Iv) De...IOSR Journals
Some di-and triorganotin(IV) derivatives of (2E)-N-methyl-(2
oxo1,2diphenylethylidne)hydrazinecarbothioamide synthesised by the reactions of the corresponding di and
triorganotin(IV) chlorides with the sodium salt of (2E)-N-methyl-(2-
oxo1,2diphenylethylidne)hydrazinecarbothioamide in different molar ratios. These derivatives have been
characterized by elemental analyses ,molecular weights, conductivity measurements and spectral(IR, 1H, 13C
and 119 Sn NMR) studies.
Alkali P-Nitrophenolates for Short Wavelength Laser GenerationEditor IJCATR
Single crystals of alkali p-Nitrophenolates namely sodium p-nitrophenolate dihydrate (SPNP), potassium p- nitrophenolate
monohydrate (PPNP) and lithium p-nitrophenolate trihydrate (LPNP) using Group I elements (Na, K, Li) and p-nitrophenols were grown
by solvent evaporation method. Single crystal XRD analysis shows that SPNP and LPNP crystallize in noncentrosymmetric space group
while PPNP is centrosymmetric. Using Autox software, all the peaks in the recorded powder XRD spectrum of the samples were identified
and indexed. The FT – IR spectra of the sample reveals the characteristic vibrations of the functional groups present in alkalinitrophenolates.
A weak absorption band around the region 1589–1641 cm-1 confirms the presence of the phenolic ring. A broad
intermolecular hydrogen bonded OH stretching at 3325 cm-1 of p- nitrophenol is shifted which shows the increase in the polarizable nature
of p–nitrophenol and thus easily forms a metal (sodium/ potassium/ lithium) coordination compound. UV-Vis spectrum shows that all the
crystals are transparent above 400 nm and has a wide optical window in the visible region. Intense absorption peak in the UV region may
be due to the colored nature of the compound. Addition of metal ion (sodium/potassium) modifies the optical transparency of the original
molecule (p-nitro phenol) and consequently introduces a bath chromic shift of 90/40 nm in the crystal transparency of the samples. Kurtz
powder technique result shows that the relative SHG efficiency of SPNP and LPNP was nearly 5 and 9.25 times of KDP.
Reaction of aniline with ammonium persulphate and concentrated hydrochloric a...Maciej Przybyłek
In this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.
Exploring Career Paths in Cybersecurity for Technical CommunicatorsBen Woelk, CISSP, CPTC
Brief overview of career options in cybersecurity for technical communicators. Includes discussion of my career path, certification options, NICE and NIST resources.
New Explore Careers and College Majors 2024.pdfDr. Mary Askew
Explore Careers and College Majors is a new online, interactive, self-guided career, major and college planning system.
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2. Horner-Wittig Reagents in Sulfur and Selenium Chemistry Pieter Otten and Arne van der Gen Leiden Institute of Chemistry Leiden University, The Netherlands P S Se
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4. Thioamide Synthesis Aminomethylphosphine oxides, excellent reagents for enamine formation, show a unique reactivity towards chalcogens to form amides R = aryl: reaction at r.t R = alkyl: reaction at 0 o C to quell deprotonation of formed thioalkanamides by the HW reagent
5. Selenoamide Synthesis “ Red selenium”, Se 8 , more reactive than metallic or gray Se; allows isolation of acidic selenoalkanamides at lower temperatures Reaction is sluggish at ambient.
6. Mechanistic Considerations One eq. of S gives < 50% yield, recover phosphine oxide All intermediates isolated and characterized. Mass balance accounted for. Intermediate trapped at low temperatures with MeI Independently confirmed
7. Crystal Structure Selenobenzamides Amino group reduces dihedral angle C=Se: 1.840 Å C-N: 1.331 Å = 53.3º C=Se: 1.824 Å = 81.1º C(5) is sp 2 -hydrid.
9. VT 13 C NMR Study: Rotational Barriers C=S and C=Se strongly e-withdrawing groups, + p fits only More polarizable Se more sensitive to + p than S o = Se * = S Eyring eq.: G* rot = 19.5T c x [9.971 + log(T c / )]
12. Mechanistic Considerations (Curtin-Hammett Principle) Trapped HW-adducts (R3 = Ph -60 o C, H 2 O): R1 = n-Pr: pro(E)/pro(Z) = 1/1, quant. R1 = c-Hex: pro(E)/pro(Z) = 1/1+ 22% (E)-vinyl selenide! Sterics facilitate elimination, k E increases R1 = phenyl, pro(E)/pro(Z) = 3/2. quant, pro-(E) and pro(Z) must rapidly equilibrate via reverse to aldehyde and/or epimerization and (E)-isomer is thermodynamic sink pro-(E) Pro-(Z)
13. Do HW adducts equilibrate? No vinyl selenide derived from propionaldehyde observed: no equilibration via reverse reaction with aliphatic aldehydes. Cannot rule out epimerization. Fast equilibration with aromatic aldehydes to explain discrepancy between pro-(E) and pro-(Z) ratio for isolated HW adduct (3/2) and strong E-selectivity for completed HW reaction.
14. Alternate Intermediate Warren proposes this late-stage intermediate to explain high pro-(Z) selectivity for simple alkyl phosphine oxides (R1 = alkyl) Pro-(E) Six-centered transition state. R1 equatorial to avoid 1,3-interaction with equatorial Ph. Low energy difference between SeR3 equatorial or axial, reflected by observed low stereoselectivity In HW-adducts. Pro-(Z)
17. Crystal Structure Confirms Z-geometry P -1 , a = 13.3146, b = 11.326, c = 9.395 Å; = 125.15 = 97.88, = 96.76; V = 1097.45 Å 3 , Z = 4, = 1.396 kg/dm 3
18. Mechanistic Considerations Phosphine oxide anion and carbonyl are in equilibrium w/ adduct. Fast when R1 = anion stabilizing aryl Rotation sets up for the oxaphosphetane. Sterics favor pro-(Z) intermediate Thermodynamic sink Elimination fast if R2 stabilizes double bond: aryl, vinyl
19. Mechanistic Considerations: Alternate Approach Surprisingly poor stereochemistry with bulky c-hexanecarboxaldehyde Li + ligated between P=O and S=O. R1 equatorial to avoid axial Ph. Aldehyde approaches with R2 pointing away from axial Ph. Must be an intermediate trough on the energy surface
20. Michael Addition P 2 1 , a = 6.371, b = 7.646, c = 12.364 Å; = 90.0 = 98.45, = 90.0; V = 595.7 Å 3 , Z = 2, = 1.50 kg/dm 3
21. Mechanistic Considerations A compact sodium complex is formed, dictating stereochemistry Malonitrile gives 1:1 mixture of diastereoisomers
22. Synthesis of S , N -ketene Acetals and Thioesters R2=aryl: pure ketene acetale after extractive work-up only. R2=alkyl, contaminated w/ condensation products. Carry thru to thioester for good use
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24. Fluorescent Magnesium Indicators Pieter Otten, Louis Levy, and Robert London, National Institute of Environmental Health Sciences, RTP, NC
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27. Why APTRA (Aminophenol Triacetic Acid)? At physiol. Mg 2+ , BAPTA binds two ions. Cut BAPTA in half to get to APTRA.
28. Pd coupling: fast, one step approach to quickly invest structural diversity
29. Suzuki Coupling K D, Mg = 2.3 mM K D, Ca = 70 M K D, Mg = 2.1 mM K D, Ca = 28 M K D, Mg = 1.8 mM K D, Ca = 17 M
31. Synthesis of 4-Oxo-4 H -quinolizine-3-carboxylates Known complexers of Mg 2+ to shut down bacterial DNA-gyrase w/ K D = 1 mM Explore reactivity to diversify quickly
40. NMR-active, Fluorinated Reporter Molecules Pieter Otten and Ralph P. Mason Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX
43. CF 3 -POL Triple the fluorines, triple the signal Does not penetrate rbc membrane
44. Fluorinated Gene Reporter Saline at 30 o C (♦) Plasma at 30 o C (□) Plasma at 37 o C (Δ) Top: pH = 4.5; t = 30 o C; β-gal ( Aspergillus Oryzae ) Bottom: pH = 7.3 -> 6.8; t = 37 o C; β-gal ( E. Coli ) pK a = 6.85