The dramatic effect of thiophenol on the reaction pathway of ethyl 4-chloromethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate with thiophenolates: ring expansion versus nucleophilic substitution

Benzene imine (1) ⇌ 1H-azepine (2) isomerization occurs through sequential valence and endo–exo isomerism. Quantum chemical and quasiclassical trajectory (QCT) simulations reveal the coupled reaction pathway ‒ ring-expansion followed by...

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Uncatalyzed reactions of α-(trihaloethylidene)nitroalkanes with push–pull enamines: a new type of ring–ring tautomerism in cyclobutane derivatives and the dramatic effect of the trihalomethyl group on the reaction pathway

Tetrahedron Letters ◽

10.1016/j.tetlet.2011.08.109 ◽

2011 ◽

Vol 52 (44) ◽

pp. 5764-5768 ◽

Cited By ~ 25

Author(s):

Vladislav Yu. Korotaev ◽

Alexey Yu. Barkov ◽

Pavel A. Slepukhin ◽

Mikhail I. Kodess ◽

Vyacheslav Ya. Sosnovskikh

Keyword(s):

Reaction Pathway ◽

Dramatic Effect ◽

New Type ◽

Cyclobutane Derivatives

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ChemInform Abstract: Intramolecular Nucleophilic Substitution at the C-4 Position of Functionalized Oxetanes: A Ring Expansion for the Construction of Various Heterocycles.

ChemInform ◽

10.1002/chin.199711037 ◽

2010 ◽

Vol 28 (11) ◽

pp. no-no

Author(s):

T. BACH ◽

K. KATHER

Keyword(s):

Nucleophilic Substitution ◽

Ring Expansion ◽

Intramolecular Nucleophilic Substitution

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Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.16.47 ◽

2020 ◽

Vol 16 ◽

pp. 515-523 ◽

Cited By ~ 1

Author(s):

Svetlana V Amosova ◽

Andrey A Filippov ◽

Nataliya A Makhaeva ◽

Alexander I Albanov ◽

Vladimir A Potapov

Keyword(s):

Nucleophilic Substitution ◽

Nucleophilic Addition ◽

Stereoselective Synthesis ◽

Ring Expansion ◽

Nucleophilic Attack ◽

Substitution Reactions ◽

Ring Contraction ◽

Rearrangement Reaction ◽

High Yields ◽

Alkyl Propiolates

The reaction of 2-(bromomethyl)-1,3-thiaselenole with potassium selenocyanate proceeded via a rearrangement with ring expansion, leading to a six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate (kinetic product) which in turn underwent rearrangement with ring contraction to a 1,3-thiaselenol-2-ylmethyl selenocyanate (thermodynamic product). These rearrangements occurred by a nucleophilic attack of the selenocyanate anion at two different carbon atoms of the seleniranium intermediate. The efficient regioselective synthesis of alkyl, allyl, 2-propynyl, benzyl, 4-fluorobenzyl, and 2-pyridinylmethyl 1,3-thiaselenol-2-ylmethyl selenides was developed based on the generation of sodium 1,3-thiaselenol-2-ylmethylselenolate from 1,3-thiaselenol-2-ylmethyl selenocyanate or bis(1,3-thiaselenol-2-ylmethyl) diselenide followed by nucleophilic substitution reactions. Sodium 1,3-thiaselenol-2-ylmethylselenolate underwent nucleophilic addition to alkyl propiolates in a regio- and stereoselective manner affording 1,3-thiaselenol-2-ylmethyl vinyl selenides in high yields predominantly with Z-configuration. Not a single representative of the 1,3-thiaselenol-2-ylmethyl selenide scaffold has been previously described in the literature.

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On the Concerted Ring Opening of Protonated Squalene Oxide and A-Ring Formation in the Biosynthesis of Lanosterol

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20030202 ◽

2003 ◽

Vol 68 (1) ◽

pp. 202-210 ◽

Cited By ~ 10

Author(s):

B. Andes Hess

Keyword(s):

Ring Opening ◽

Density Functional ◽

Reaction Pathway ◽

Ring Expansion ◽

Membered Ring ◽

Ring Formation ◽

Ring Closure ◽

Primary Role ◽

Transition Structure

Density functional calculations were performed on a model system of squalene oxide to study the mechanism of the formation of ring A in the biosynthesis of lanosterol from squalene. When (2Z)-6,7-epoxy-3,7-dimethyloct-2-ene was protonated, it was calculated to undergo a very facile ring opening of the oxirane in concert with the formation of the six-membered ring of the 4-(hydroxymethyl)-1,2,3,3-tetramethy1cyclohexyl cation. A study of the reaction pathway (IRC) indicates a very early transition structure in which the carbon- carbon double bond participates anchimerically in the ring-opening of the protonated oxirane. It is suggested that the primary role of the enzyme in this first step of the biosynthesis of lanosterol is protonation of the oxirane ring along with holding the substrate in the proper conformation for the concerted ring-closure to occur. The similarity between this mechanism and that recently proposed for concerted C-ring expansion and D-ring formation in the biosynthesis of lanosterol is discussed.

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