A quantum chemical AM1 study of a Diels–Alder and retro-Diels–Alder tandem reaction
01 Jan 1994-Journal of The Chemical Society-perkin Transactions 1 (The Royal Society of Chemistry)-Iss: 2, pp 281-284
TL;DR: An AM1 study on two convergent Diels-Alder reactions has shown that the formal transfer of an alkoxy substituent from a dienophile to a diene through a diels-alder/retro-Diels-alger tandem reaction is feasible as mentioned in this paper.
Abstract: An AM1 study on a two convergent Diels–Alder reactions has shown that the formal transfer of an alkoxy substituent from a dienophile to a diene through a Diels–Alder/retro-Diels–Alder tandem reaction is feasible.
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TL;DR: In this paper, the formation of a ball-and-chain model adduct through a Diels-Alder reaction between 2,3-dimethylidene-bicyclo[2.2]octane (C 10 H 14 ) and buckminsterfullerene (C 60 ) has been studied theoretically by means of the AM1 semi-empirical method.
49 citations
TL;DR: A comprehensive review of the literature on retro Diels-Alder reactions can be found in this article, with a focus on expelling C-C dienophiles, i.e. those reactions that generate a new carbon-carbon double or triple bond in the dienophile.
Abstract: The Diels–Alder (“DA”) reaction is so familiar to organic chemists that the retro-Diels–Alder or retro-diene reaction (hereafter “rDA”) requires no conceptual introduction. However, a working definition is needed to indicate the coverage of this review. The intent is to include all reported examples of the general skeletal process excluded in this chapter.
Any of the atoms in the starting material (cycloadduct) may be carbon or heteroatom, and substituents on all positions are allowed. In addition, any bond order available to the element in any oxidation state is included, as well as bonding to non-nearest neighbor atoms (bicyclics, etc.).
The volume of literature required separation of this review into two parts. Part I covers all expelled C–C dienophiles, i.e. those reactions that generate a new carbon-carbon double or triple bond in the dienophile that is formed. Part II, to appear later, covers those expelled dienophiles in which one or both atoms is a heteroatom.
Certain specific topics are intentionally omitted. These are: rDA reactions invoked under mass spectral conditions; rDA reactions of polymeric substrates; Electrocyclic processes, some of which are arguably very similar to rDA reactions (these are not addressed unless needed for clarification of an rDA sequence); and a thorough discussion of homo-rDA reactions.
CAS-Online searches resulted in ca. 1,300 references, of which ca. 900 proved pertinent to the rDA topic as defined and delimited above. Active literature searching was halted in April 1995, but occasional more recent articles are included.
Over 2,500 pertinent references were eventually found. Most were obtained by perusal of primary literature (articles) and secondary sources (books and reviews). Computer based search success was limited mainly by the failure of authors or abstractors to key-word this topic, an especially common occurrence when the expelled dienophile was a simple substance such as N2 or CO2. Overall, approximately 3,500 books, chapters, reviews, articles, and abstracts were consulted in an effort to make this review as comprehensive as possible. This was done with the certainty that some pertinent literature would be missed, tempered by the view that these omissions are probably also lost to any future rational search method.
Many secondary sources proved valuable not only for in-depth discussion of certain rDA reaction types, but also for providing comparisons with related topics. To assist the reader, these secondary sources are referenced (alphabetically by first author within broad subject areas) with a title or brief note on the topic(s) addressed. The first group lists earlier reviews with primary focus on rDA reactions, followed by items of Historical/General Interest, reviews that deal with Experimental Methods, DA reactions (general and specific), reviews of Related Topics (these impinge in more or less significant ways on rDA reactions), and general treatments of Theory and Mechanism.
Keywords:
retro Diels-Alder reactions;
dienophiles;
mechanism;
scope;
limitations;
acid catalysis;
base induced reactions;
scavengers;
reactivity comparisons;
acetylenic dienophiles;
alkyl ethylenes;
alkyl alkenes;
aryl substituted alkenes;
vinyl substituted alkenes;
heteroatom substituted alkenes;
ketenes;
experimental conditions;
tabular survey
48 citations
TL;DR: A novel and convenient route for the preparation of chiral tricyclic iminolactones 9 and 10 from camphorquinone has been developed and the extremely high endo-face selectivity for alkylation is discussed using semiempirical calculations.
Abstract: A novel and convenient route for the preparation of chiral tricyclic iminolactones 9 and 10 from camphorquinone has been developed. Alkylation of iminolactones 9 and 10 provided iminolactones 16 and 17 in high yields which were, in turn, alkylated again to afford the α,α-disubstituted products in good yields (70−90%) and excellent diastereoselectivities (>98%). Hydrolysis of the alkylated iminolactones furnished the desired α,α-disubstituted α-amino acids in good yields and high enantiomeric excesses with good recovery yields of the chiral auxiliary 12 and 13. The extremely high endo-face selectivity for alkylation is discussed using semiempirical (MOPAC 93) calculations.
29 citations
TL;DR: In this paper, the transition structures and energetics of Diels-Alder reactions of allene with cyclopentadiene and hexachlorocyclopentadene and fluoroallenes were investigated using semi-empirical MO methods at AM1 and PM3 levels.
Abstract: Transition structures and energetics of Diels–Alder reactions of allene with cyclopentadiene and hexachlorocyclopentadiene, and fluoroallenes with cyclopentadiene and furan have been investigated using semiempirical MO methods at AM1 and PM3 levels. Allene and fluoroallenes react through an asynchronous transition structure in which the terminal carbon atom involved in the reaction pyramidalizes and the central carbon atom triangulates and this deformation accounts for almost half the reaction barrier. Allene is found to be a less reactive dienophile compared to ethylene, contrary to expectations, and its reactivity enhances with fluorine substitution up to 1,1-difluoroallene and declines on further substitution of fluorine. Tetrachloroallene is found to be less reactive than allene itself. The reactivity of furan in such cumulene reactions is found to be almost the same as that of cyclopentadiene. While PM3 predictions in certain cases are not reliable AM1 reaction barriers explain reasonably the reactivities and stereochemical preferences of the above reactions.
21 citations
TL;DR: A theoretical study is performed of the Diels-Alder reactions of various o-quinodimethanes (QDM) with C(60) by the AM1 model and limited ab initio and DFT techniques, showing the overall aromaticity effect shown by the aromatization as well as the aromaticity of C( 60) seems to accelerate these reactions at an increased rate.
Abstract: A theoretical study is performed of the Diels−Alder reactions of various o-quinodimethanes (QDM) with C60 by the AM1 model and limited ab initio and DFT techniques. All reactions are shown to proceed through a concerted transition state possessing a considerable net aromaticity as evidenced from bond orders and magnetic criteria such as the magnetic susceptibility exhaltations (MSE) and nucleus independent chemical shifts (NICS) and produce different kinds of aromatic stabilized fullerene cycloadducts. Computations show that a strong LUMO-dienophile control of C60 is realized by the influence of pyramidalization, but its high reactivity over alkene appears to be governed by the global aromaticity on fullerene rather than its strain. The aromatic functionalization occurring in QDM upon cycloaddition drastically increases the reaction rate and exothermicity of all QDM-C60 reactions as compared to the butadiene-C60 reaction. In fact, the simultaneously existing aromatic destabilization in fullerene indicates...
21 citations
References
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TL;DR: In this paper, a new parametric quantum mechanical molecular model, AM1 (Austin Model l), based on the NDDO approximation, is described, in which the major weaknesses of MNDO, in particular failure to reproduce hydrogen bonds, have been overcome without any increase in computing time.
Abstract: A new parametric quantum mechanical molecular model, AM1 (Austin Model l), based on the NDDO approximation, is described. In it the major weaknesses of MNDO, in particular failure to reproduce hydrogen bonds, have been overcome without any increase in computing time. Results for 167 molecules are reported. Parameters are currently available for C, H, 0, and N.
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TL;DR: A number of theorems are proved to show that it always converges and that it converges rapidly, and this method has been used to solve a system of one hundred non-linear simultaneous equations.
Abstract: © The British Computer Society Issue Section: Articles Download all figures A powerful iterative descent method for finding a local minimum of a function of several variables is described. A number of theorems are proved to show that it always converges and that it converges rapidly. Numerical tests on a variety of functions confirm these theorems. The method has been used to solve a system of one hundred non-linear simultaneous equations. Related articles in Web of Science
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TL;DR: In this article, a detailed analysis of the geometries, energies, and electronic characteristics of the transition structures of pericyclic reactions is provided. But the analysis is restricted to a single class of reactions.
Abstract: Twenty-five years after the discovery of a vast class of organic reactions named “pericyclic reactions” by Woodward and Hoffmann, ab initio quantum mechanics provides a detailed analysis of the geometries, energies, and electronic characteristics of the transition structures of these reactions. Common features are found in all these reactions, and generalizations permit prediction of other transition-structure geometries and energies. At the same time, great diversity is observed—from strongly bonded, rigid, closed-shell entities to weakly interacting, flexible diradical structures.
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TL;DR: An algorithm is presented for minimizing real valued differentiable functions on an TV-dimensional manifold and a proof is given for convergence within iV-iterations to the exact minimum and variance matrix for quadratic functions.
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467 citations