Stereoselective And Stereospecific Reactions Pdf Creator

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Diels–Alder reaction

Pericyclic reactions are important class of chemical reaction because they occur stereospecifically often with a high degree of regio-, stereoselectivity, and atom economy.

This dissertation summarizes our efforts — using chemical computations — to better understand how these reactions occur in both biological and abiological settings.

This dissertation is divided into two portions; the first of which describes quantum mechanical studies of biosynthetic and enzyme-catalyzed cycloadditions. Chapter 1, 2, and 3 detail studies of these enzymatic processes. Using state-of-the-art density functional theory, we have determined whether these reactions are feasible biosynthetic transformations, elucidated the mechanistic subtleties of these reactions, and proposed how enzymes may catalyze such transformations. Chapter 1 describes a computational study of a strained biosynthetic transannular 1,3-dipolar cycloaddition.

Computations reveal that substrate preorganization overrides distortion in the transitions, resulting in a reaction is feasible. Strategic hydrogen bonding, according to theory, can accelerate the reaction by fold.

Chapter 2 summarizes a computational investigation of the Diels-Alder reaction involved in the biosynthesis of spinosyn A. Chapter 3 discusses an ongoing collaboration with the Tang laboratory at UCLA and involves an effort to understand the intramolecular Diels-Alder reaction involved in the biosynthesis of cholesterol-reducing agent, lovastatin. We have modeled the reaction of a related cycloaddition performed experimentally, and computations recapitulate the selectivity observed experimentally for this nonenzymatic process.

The stereochemical outcome of the enzymatic reaction diverges from the outcome of its synthetic analogue. Computation of the reactive conformer of the model substrate suggests that substrate preorganization could accelerate the intramolecular Diels-Alder reaction by approximately a fold.

Theoretical studies of stereoselective electrocyclic reactions are described in Chapters 4, 5, 6, 7, and 8. These reactions have been examined by experimentally by chemists in the laboratory and, subsequently, have been modeled using quantum mechanical computations.

From this computational work, we have determined the stereoselectivity of several synthetically relevant electrocyclic reactions, the effect of substituents of the reactivity of the electrocyclization precursors.

In Chapter 4, we summarize our work with Dr. Gregg Barcan and Prof. Ohyun Kwon to elucidate the origins of 1,6-stereoinduction of a triene electrocyclization employed in their total synthesis of reserpine. Allylic strain destabilizes the disfavored mode of ring closure. According to both theory and experiment, stereoselectivity is shown to be sensitive to the size of the substituent involved in the A1,3 strain. These cascades reaction occur spontaneously in a growing number of natural products.

Here we determined the influence terminal substitution on the reactivities, thermodynamics, and stereoselectivities of these reactions. Where possible, the diastereoselectivity of this cascade is controlled by a steric effect that destabilizes the endo mode of electrocyclic ring closure. Chapter 6 reviews a density functional theory study of a series of torquoselective triene and Nazarov electrocyclizations of bridged bicyclic substrates.

We find that the torquoselectivities of highly exo selective ring closures are controlled by action of torsional effect that acts in concert with either steric attraction or repulsion. In one case, a Nazarov cyclization, a through space orbital interaction overrides this exo selectivity.

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Transannular rearrangement pdf merge

A pi bond is broken on the dienophile during the course of the Diels-Alder reaction, and the hybridization goes from sp 2 to sp 3. So what happens to the stereochemistry of the groups attached the pi bond? Take the two dienophiles maleic acid and fumaric acid for example. These two molecules are diastereomers , differing only in the orientation of the two carboxylic acid groups about the double bond. This pair of diastereomers makes an excellent probe for determining how the stereochemistry of the dienophile pi bond is affected in the Diels-Alder reaction.

Metal-catalyzed reactions often allow access to reactivity that would be otherwise unavailable to researchers using more conventional synthetic methods. The Jarvo lab has worked to develop both stereoselective and stereospecific metal-catalyzed reactions that proceed with high stereochemical fidelity to produce synthetically useful products. In Chapter 1 the enantioselective silver-catalyzed propargylation of N-sulfonylketimines is described. This reaction proceeds in high yield and excellent enantiomeric ratio and is compatible with a wide variety of diaryl and aryl-alkylketimines. The synthetic transformation of one of the homopropargylic products via Sonogashira cross-coupling proceeds with high stereochemical fidelity.


Foremost, I would like to thank my creator (Allah) for making me a functionality present in organic molecules with complete stereospecificity.


Transannular rearrangement pdf merge

ASAP Articles are edited and published online ahead of issue. See all articles. JOC publishes Special Issues that focus on timely topics in organic chemistry, featuring work by top authors in the field. Presenting cutting-edge contributions driven by a renaissance in the field of carbohydrate chemistry.

In organic chemistry , the Diels—Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene , commonly termed the dienophile , to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a concerted mechanism. It was first described by Otto Diels and Kurt Alder in

Pdf k look inside references cited by pdf previous on the concentration potential next. This is a pdf file of an unedited manuscript that has been accepted for publication.

Stereochemistry of the Diels-Alder Reaction

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New Syllabus for M. Sc (Regular) in Chemistry PDF Creator - PDF4Free v Acyclic systems up to 4 chiral centers: Compounds with asymmetric carbons in enantrotopic and diastereotopic atoms, groups and faces, stereospecific and.


Pericyclic reactions are important class of chemical reaction because they occur stereospecifically often with a high degree of regio-, stereoselectivity, and atom economy. This dissertation summarizes our efforts — using chemical computations — to better understand how these reactions occur in both biological and abiological settings. This dissertation is divided into two portions; the first of which describes quantum mechanical studies of biosynthetic and enzyme-catalyzed cycloadditions. Chapter 1, 2, and 3 detail studies of these enzymatic processes.

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    Organic Chemistry Stereoselectivity in organic synthesis • Stereospecific reactions - a reaction where the mechanism means the stereochemistry of the.

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    In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated The reaction is an example of a concerted pericyclic reaction. the vast majority of Diels–Alder reactions exhibit stereospecific, syn addition of the two This is a stereoselective situation based on the relative orientation of the two.

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