457 research outputs found
Sulfoxides as an intramolecular sulfenylating agent for indoles and diverse applications of the sulfide-sulfoxide redox cycle in organic chemistry
This dissertation involves study of various aspects of sulfoxide chemistry. Specifically designed t-butyl and propanenitrile sulfoxides tethered to indole-2-carboxamide were used as a source of intramolecular sulfenylating agents to synthesize novel indolo[3,2-b]-1-5-benzothiazepinones which are structurally analogous to the other biologically active benzothiazepinones. This study reveals that the intramolecular cyclization of sulfoxide follows an electrophilic sulfenylation (Sulfoxide Electrophilic Sulfenylation, SES) reaction pathway. Evidence of the absence of sulfenic acid as a transient reactive intermediate in such intramolecular cyclization is also provided.
In another study, sulfoxide was used as a “protecting group” of thioether to synthesize 8-membered, indole substituted, thiazocine-2-acetic acid derivative via Ring Closing Metathesis (RCM). Protection (oxidation) of inert (to RCM) sulfide to sulfoxide followed by RCM produced cyclized product in good yields. Deprotection (reduction) of sulfoxide was achieved using Lawessons Reagent (L.R.). Application of the sulfide-sulfoxide redox cycle to solve the existing difficulties in using RCM methodology to thioethers is illustrated.
A new design of a “molecular brake”, based on the sulfide-sulfoxide redox cycle is described. N-Ar rotation in simple isoindolines is controlled by the oxidation state of the proximate sulfur atom. Sulfide [S(II)] shows “free” [brake OFF] N-Ar rotation whereas sulfoxide displayed hindered [brake ON] N-Ar rotation. The semi-empirical molecular orbital (PM3) calculations revealed concerted pyramidalization of amidic nitrogen with N-Ar rotation
Study protocol for a randomised controlled trial of electronic cigarettes versus nicotine patch for smoking cessation
PMCID: PMC3602285This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Algorithm for Solving Tri-diagonal Finite Volume Discretized Linear Systems
In this paper we present efficient computational algorithms for solving finite volume discretized tri-diagonal linear systems. The implementation of the algorithm for steady state finite volume structured grids linear system using MS Excel is presented. An example is given in order to illustrate the algorithms
Fourier Neural Operator Networks: A Fast and General Solver for the Photoacoustic Wave Equation
Simulation tools for photoacoustic wave propagation have played a key role in
advancing photoacoustic imaging by providing quantitative and qualitative
insights into parameters affecting image quality. Classical methods for
numerically solving the photoacoustic wave equation relies on a fine
discretization of space and can become computationally expensive for large
computational grids. In this work, we apply Fourier Neural Operator (FNO)
networks as a fast data-driven deep learning method for solving the 2D
photoacoustic wave equation in a homogeneous medium. Comparisons between the
FNO network and pseudo-spectral time domain approach demonstrated that the FNO
network generated comparable simulations with small errors and was several
orders of magnitude faster. Moreover, the FNO network was generalizable and can
generate simulations not observed in the training data
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