INDEX Diels-Alder reaction

Solvents exert their influence on organic reactions through a complicated mixture of all possible types of noncovalent interactions. Chemists have tried to unravel this entanglement and, ideally, want to assess the relative importance of all interactions separately. In a typical approach, a property of a reaction (e.g. its rate or selectivity) is measured in a laige number of different solvents. All these solvents have unique characteristics, quantified by their physical properties (i.e. refractive index, dielectric constant) or empirical parameters (e.g. ET(30)-value, AN). Linear correlations between a reaction property and one or more of these solvent properties (Linear Free Energy Relationships - LFER) reveal which noncovalent interactions are of major importance. The major drawback of this approach lies in the fact that the solvent parameters are often not independent. Alternatively, theoretical models and computer simulations can provide valuable information. Both methods have been applied successfully in studies of the solvent effects on Diels-Alder reactions. 

The first chapter presents the general aspects of the reaction Chapters 2-6 illustrate the various methods and their applications in organic synthesis. At the end of each chapter a list of graphically abstracted Diels-Alder reactions is presented to show selected synthetic applications of the specific methodology. The discussion of the various topics is not exhaustive because our aim has been to emphasize the synthetic potential of each method. Chapter 7 reports a list of books, reviews, monographs and symposia proceedings which have appeared since 1990 and an index of keywords to help the reader find a particular paper of interest. 

An increase of char yield is generally reflected as an improvement in oxygen index. In the styrylpyridine based polyesters and polycarbonate an intermolecular thermally induced Diels-Alder reaction has occurred through the double bond, this increased the char yield and decreased the flammability. The Fries rearrangement, as well as dimerization and isomerization, occurred simultaneously during the UV irradiation of p-VPPB, but no dimerization or isomerization occurred for p,p -BVPDPC, probably due to steric effects. 

Diazo transfer reactions p-Toluenesulfonyl azide, 226 Diazotization Sodium nitrite, 170, 282 Dicarboxylation (see Addition reactions to carbon-carbon multiple bonds) Diels-Alder reaction (For a list of dienes and dienophiles see Type of Compound Index)... 

S CONTENTS Introduction to the Series An Editor s Foreword, Albert Padwa. Preface, Dennis P. Curran. Intramolecular 1,3-Dipolar Cycloaddition Chemistry, Albert Padwa and Allen M. Schoffstall. Stereochemical and Synthetic Studies of the Intramolecular Diels-Alder Reaction, William R. Roush. Thermal Reaction of Cyclopropenone Ketals, Key Mechanistic Features, Scope and Application of the Cycloaddition Reactions of Cyclopropenone Ketals and p - Delocalized Singlet Vinyl Carbenes Three Carbon 1,1-/1,3-Dipoles, Dale L. Boger and Christine E. Brotherton-Pleiss. Index. 

This year, following a consultation exercise involving members of the Editorial Board, and partly in the interest of getting the Volume published as soon as possible after the end of the year being reviewed, the Index is less comprehensive than formerly. It now includes only systematic heterocyclic ring system names. Thus, wherever a pyrrole is discussed, that would be indexed under pyrroles wherever pyrido[3,4-i]indoles are mentioned an indexed entry under that name will be found similarly aceanthryleno[l,2-e][l,2,4]triazines , azirines , 2f/-pyran-2-ones , 1,2,4-triazoles etc. etc. are listed. But, subjects like 4-ethyl-5-methylpyrrole , 5-acylazirines , 6-alkyl-2//-pyran-2-ones , 3-alkylamino-l,2,4-triazoles , are not listed as such in the Index. Diels-Alder reaction or Fleck coupling etc., are also not indexed. 

The aromaticity index of the ring system (20) has been calculated and compared with related systems <87T4725>. Quantum chemical calculation for the formation of some derivatives of ring system (24) (e.g., (130), see 8.17.6.5.2) suggested that the cyclization is quite asynchronous and can be regarded as a Diels-Alder reaction of inverse electron demand <90JCS(P2)1943>. 

A sense of the growth in importance of the Diels-Alder reaction is gained by looking at the Cumulative Indexes of Chemical Abstract. Only two entries were listed under the name Diels-Alder reaction in the ten-year period from 1927 to 1936, whereas such entries had increased to 180 by the decade spanning 1947 to 1956, during which time Diels and Alder shared the Nobel Prize in Chemistry. In the five-year period from 1987 to 1991, a total of about 2400 entries appeared under this heading, and the number of citations presently exceeds 800 per year. 

The basis of this concept [32] is a simple parallel intuitively felt by Evans [154], between the ease of certain reactions and the arrangement of corresponding transition states. Thus, e.g., the ease of a majority of Diels-Alder reactions is related to the fact that transient structure created by approaching the diene and dienophilic components is isoconjugated, or in other words, topologically equivalent, with the aromatic benzene and as a such should be therefore stabilized, at least in part, as the benzene itself. This simple idea was revived by Dewar [32] who also generalized it into the form of simple rule that (thermally) allowed reactions proceed via aromatic transition states. The proposed theoretical justification of the above criterion arises from a simple idea of direct quantitative evaluation of the resemblance of electron structure of expected transition states with the appropriate aromatic standards. The quantitative measure of this resemblance is the similarily index (102), where Q and ref represent the density matrices of the expected transition state and the appropriate reference standard respectively. 

Taber, Douglass F., 1948 —. Intramolecular Diels-Alder and Alder ene reactions. (Reactivity and structure v. 18). Bibliography p. Includes indexes. 1. Diels-Alder reaction. I. Title. II. Series. 

Hence, cation-radical copolymerization leads to the formation of a polymer having a lower molecular weight and polydispersity index than the polymer got by cation-radical polymerization— homocyclobutanation. Nevertheless, copolymerization occnrs nnder very mild conditions and is regio-and stereospecihc (Bauld et al. 1998a). This reaction appears to occnr by a step-growth mechanism, rather than the more efficient cation-radical chain mechanism proposed for poly(cyclobutanation). As the authors concluded, the apparent suppression of the chain mechanism is viewed as an inherent problem with the copolymerization format of cation-radical Diels-Alder polymerization. ... 

The aromaticities of symmetry-allowed and -forbidden transition states for electrocyclic reactions and sigmatropic rearrangements involving two, four, and six r-electrons, and Diels-Alder cycloadditions, have been investigated by ab initio CASSCF calculations and analysis based on an index of deviation from aromaticity. The order of the aromaticity levels was found to correspond to the energy barriers for some of the reactions studied, and also to the allowed or forbidden nature of the transition states.2 The uses of catalytic metal vinylidene complexes in electrocycliza-tion, [l,5]-hydrogen shift reactions, and 2 + 2-cycloadditions, and the mechanisms of these transformations, have been reviewed.3... 

Dielectric constant A value that serves as an index of the ability of a substance to resist the transmission of an electrostatic force from one charged body to another the lower the value, the greater the resistance. Diels-Alder reation A reaction involving the addition of an ethylenic double bond to a conjugated diene. 

CONTENTS Facial Diastereoselection in Diels-Alder Cycloadditions and Related Reactions Understanding Planar Interactions and Establishing Synthetic Potential, A. G. Faille and Yee-Fung Lu. Substituent and Structural Effects in the Ozonolysis of Cyclic Vinylogous Esters. W. H. Bunnelle. N-Metalated Azomethine Ylides, S. Kanemasa and Otohiko Tsuge. Azomethine Ylide Cy-cloadditlons via 1,2- Prototropy and Metallo-Dipole Formation from Imines, R. Grigg and V. Sridharan. Index. 

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