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A mechanism study and an investigation of the reason for the stereoselectivity in the [4+2] cycloaddition reaction between cyclopentadiene and gem-substituted ethylene electrophiles

Aitouna Abdelhak Ouled, Barhoumi Ali, Zeroual Abdellah

Scientiae Radices

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2023

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Vol. 2, Iss. 3

217--228

EN

The Molecular Electron Density Theory is applied to the [4+2] cycloaddition reaction between cyclopentadiene and gem-substituted ethylene electrophiles. Calculations are made for reactions, activation energies, and reactivity indices. The results of the experiment are perfectly consistent with activation energies, which unequivocally show that this cyclization’s are is highly stereoselective, in addition, based on ELF examination, the mechanism of these [4+2] cycloadditions occurs in two phases, The mechanisms of these reactions demonstrate that the term "pericyclic reaction" is no more relevant in the 21st century and has been replaced by the term "pseudocyclic".

2

Asymetryczne reakcje pericykliczne katalizowane kompleksami magnezu

Czombik Anna

Wiadomości Chemiczne

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2022

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[Z] 76, 9-10

755--788

EN

II Group-metals, like magnesium, are one of the most widespread elements in the environment. The abundance of II-group metals in the Earth’s crust is over 108 times greater than the precious metals. For the industrial applications, the important factors are the low costs of production and higher accessibility of their compounds. This puts the spotlight on alkaline-earth metals competing with transition elements as catalysts in organic synthesis. Features of their derivatives, like mild Lewis acidity and strong Brønsted basicity enabled them to catalyze reactions where Lewis-acidactivation of the substrate is essential. In this review the emphasis was put on magnesium-catalyzed pericyclic reactions, which are recognized as one of the most important methods of new carbon-carbon or carbon-heteroatom bonds formation. Using the catalysts based on II-group metal cations and chiral ligands, a highly stereoselective conversion of achiral substrates into enantioenriched products is possible. The Mg-based catalysts have been used in Diels-Alder, ene and 1,3-dipolar additions. Described synthesis methods were characterized by high efficiency (chemical yields and enantiomeric excesses). Where applicable, the relationships between the structure of catalyst/substrates, conditions and efficiency were discussed. Just now there are a few applications, for example in synthesis of alkaloid (–)-manzacidine or antibiotic of algal origin – (–)-malyngolide.

3

Tandem pericyclic reactions in synthesis of azines. Part I. PM3 study of thermal behavior of 1-aza-1,3,5-hexatrienes

Suwiński J., Mohamed M.

Zeszyty Naukowe. Chemia / Politechnika Śląska

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2002

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z. 147

5-13

EN

This paper presents results of PM3 calculations of the disrotatory thermal electrocyclization of several simple azahexatrienes and a short review of selected papers concerning formation of azines in thermal processes starting from aza-1,3,5-hexatriene derivatives and occurring, we believe, as tandem pericyclic processes involving disrotatory electrocyclization followed by a concerted elimination or other thermal reactions. The results of calculations in some cases support the mechanistic propositions based on the results of synthetic experiments, in the other ones they seem to deny them, pointing out to pericyclic processes.

PL

W pracy przedstawiono wyniki obliczeń metodą PM3 dysrotacyjnej termicznej elektrocyklizacji szeregu prostych azaheksatrienów i krótki przegląd wybranych prac dotyczących tworzenia azyn w termicznych procesach wychodząc z aza-1,3,5-heksatrienu lub jego pochodnych i zachodzących, jak sądzimy, zgodnie z mechanizmem dysrotacyjnej elektrocyklizacji wraz z następczą uzgodnioną eliminacją lub innym termicznym procesem. Wyniki naszych obliczeń w niektórych przypadkach potwierdzają mechanizmy proponowane na podstawie eksperymentów, w innych wydają się im zaprzeczać, wskazując na procesy pericykliczne.

4

Reactions of 1-Arylbuta-1,3-dienes Generated from 3-Allyl-1,3-dihydro-2,1-benzisothiazole 2,2-Dioxides

Wojciechowski K., Modrzejewska H.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 11

1587-1593

EN

Thermal (215_C) extrusion of sulfur dioxide from 3-allyl-1,3-dihydro-2,1-benzisothiazole 2,2-dioxides (3-allylbenzosultams) leads to aza-ortho-xylylenes, which by [1,5] sigmatropic hydrogen shift transform into 1-(2-aminophenyl)buta-1,3-dienes. In the presence of dienophiles, N-phenylmaleimide (NPMI) or dimethyl fumarate, these dienes enter Diels-Alder reaction and the formed adducts transform into 6a,7,8,10a-tetrahydro-5H-phenanthridin-6-one derivatives. Aza-ortho-xylylene 16 generated from 3,3-diallylbenzosultam 15 transforms into arylcyclohexadiene 19, which finally adds NPMI to form bicyclo[2.2.2]octene derivative 20.

5

Quantum chemical calculations on S-centered 1,3-dipoles : 2. Reactivity of thiocarbonyl S-imides in perycyclic reactions

Mlostoń G., Fabian J.

Polish Journal of Chemistry

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1999

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vol. 73 nr 4

683-692

EN

Results of high level quantum chemical calculations on thiocarbonyl S-imides 1 are reported. The reactivity of thioformaldehyde S-imide (1a) (CH2S+NH-) in pericyclic reactions was calculated by density functional theory using gradient corrected functionals in conjunction with 6-31+G(d,p) and 6-31+G(3df, 3dp) basis sets. For the sake of comparison, conventional ab initio quantum chemical calculations at correlated levels of theory, such as MP2, QCISD(T) G1 and G2(MP2), were also performed. The predicted reactivity of the parent compound is compared with those of some closely related ylides (S-centered 1,3-dipoles), such as thioformaldehyde S-methylide (2a), thioformaldehyde S- oxide (3a) and thioformaldehyde S-sulfide (4a). To show the effect of substitution on structure and reactivity a series of acyclic and cyclic substituted thiocarbonyl S-imides 1b-k was calculated. The 1,3-electrocyclic ring closure of 1a to form thiaziridines 5 is predicted to be exothermic process by about 10 kcal/mol with activation energies of about 30 kcal/mol. The calculated reaction energies are considerably affected by higher angular momentum polarization functions, such as f-functions. In the case of some substituted thiocarbonyl S-imides, such as thiotropone S-imide (1i) and thiofluorenone S-imide (1j), the exothermicity of the ring closure reaction is lower than that of the parent compound. The concerted prototype [3+2]-cycloaddition of 1a with ethylene is strongly exothermic (about 50 kcal/mol) with the activation energy of about 20 kcal/mol. The energetics of both types of the pericyclic reactions of 1a appears closely related to that of 4a but differs more strongly from that of 3a. The contemporary knowledge on thiocarbonyl S-imides 1 is reviewed and discussed in conjunction with theoretical results.