Étude cinétique de l'ouverture thermique de la liaison C—C d'aziridines et d'époxydes dipôles-1,3 potentiels: I. Méthode d'étude expérimentale

1985 ◽  
Vol 63 (8) ◽  
pp. 2245-2252 ◽  
Author(s):  
Aïcha Derdour ◽  
Fernand Texier
Keyword(s):  
Rate Constants ◽  
Heterocyclic Compounds ◽  
The Other ◽  
Azomethine Ylide ◽  
Carbon Bond ◽  
Experimental Rate ◽  
Carbon Carbon Bond ◽  
Kinetic Treatment

The thermolysis of the 2-cyanoaziridines (1), 2-alkoxycarbonylaziridines (2), 2-arylaziridines (3), and 2,2-dicyano-3-aryloxiranes (4) leads to a rupture of the carbon –carbon bond yielding an azomethine ylide and the ylide of a carbonyl. The reaction of these ylides of azomethine with methyl acetylene dicarboxylate (MADC) leads to the formation of a 3-pyroline, which is transformed, according to the substituants, to a 2-pyrroline or to pyrrole. The addition of the ylides of carbonyl leads to the formation of dihydrofurans. Through the kinetic treatment of the addition of these heterocyclic compounds (1 to 4) to MADC, it is possible to determine the rate constants for the opening of the C—C bond (k1). In the case of the aziridines 1, the rates have been determined by ir while hplc has been used in the other cases. Relative to the heterocyclic compounds, the order of the experimental rate constants (kex) is always equal to one. In the cases of theN-cyclohexyl-2-cyano-3-alkylaziridines and of the N-cyclohexyl-2-carbomethoxy-3-phenylaziridine, kex varies with the concentration of MADC and this implies that the rate constants for the cycloaddition of the ylide of azomethine and its reclosing to give aziridine are similar. In the other cases, kex is independent of the concentration of MADC and this implies that the heterocyclic compounds are slowly transformed into 1,3-dipoles, followed by a rapid cycloaddition, [Formula: see text]. [Journal translation]

Palladium-mediated cascade or multicomponent reactions: A new route to carbo- and heterocyclic compounds

2006 ◽  
Vol 78 (2) ◽  
pp. 231-239 ◽  
Author(s):  
Geneviève Balme ◽  
Didier Bouyssi ◽  
Nuno Monteiro
Keyword(s):  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Heterocyclic Compounds ◽  
Multicomponent Reactions ◽  
Addition Reaction ◽  
Carbon Bond ◽  
Bond Forming ◽  
Carbon Nucleophiles ◽  
Carbon Carbon Bond

In recent years, new processes based on transition-metal-mediated intramolecular addition reaction of heteronucleophiles and stabilized carbon nucleophiles to unactivated alkenes and alkynes have been developed in our laboratory. In this article, we summarize a number of recent synthetic applications of these new processes. Emphasis is placed on the development of multicomponent reactions based on a Pd-mediated intramolecular cyclization coupled with a carbon-carbon bond-forming reaction. Applications of this methodology to the synthesis of natural lignans are also reported.

Preparation of heterocyclic compounds via carbon-carbon bond formation catalyzed by an antibody

1996 ◽  
Vol 2 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Tomoya Kitazume ◽  
Takashi Tsukamoto ◽  
Kouichi Murata ◽  
Koutaro Yoshimura
Keyword(s):  
Heterocyclic Compounds ◽  
Bond Formation ◽  
Carbon Bond ◽  
Carbon Carbon Bond

Electrooxidative Cyclization of Hydroquinolyl Alcohols, Hydroquinolylamines, and Dimethyl Aminomalonates

2007 ◽  
Vol 60 (4) ◽  
pp. 236 ◽  
Author(s):  
Mitsuhiro Okimoto ◽  
Takashi Yoshida ◽  
Masayuki Hoshi ◽  
Kazuyuki Hattori ◽  
Masashi Komata ◽  
...  
Keyword(s):  
Intramolecular Cyclization ◽  
Potassium Iodide ◽  
Sodium Methoxide ◽  
Heterocyclic Compounds ◽  
Bond Formation ◽  
Sodium Cyanide ◽  
Carbon Bond ◽  
Carbon Carbon Bond

Several hydroquinolyl alcohols and amines were electrochemically oxidized in methanol in the presence of sodium methoxide and potassium iodide to afford the corresponding intramolecular cyclization products. Furthermore, several amino malonates were electrochemically oxidized to yield the corresponding heterocyclic compounds through an intramolecular carbon–carbon bond formation in the presence of sodium cyanide in methanol.

Activation of a Carbon–Carbon Bond in Internal Alkynes: Vinylidene Rearrangement of Disubstituted Alkynes at an Ir Complex

Synlett ◽  
2017 ◽  
Vol 29 (06) ◽  
pp. 727-730 ◽  
Author(s):  
Youichi Ishii ◽  
Takuya Kuwabara ◽  
Shuhei Takamori ◽  
Satoshi Kishi ◽  
Takahiro Watanabe ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Metal Center ◽  
The Other ◽  
Carbon Bond ◽  
13C Labeling ◽  
Carbon Carbon Bond ◽  
Internal Alkynes ◽  
Selective Formation

Reactions of [Cp*Ir(PPh3)Cl2] with various internal acyl­alkynes in the presence of NaBArF 4 resulted in the selective formation of iridacycles via vinylidene rearrangement. 13C-labeling experiments revealed that the acyl group selectively migrates to the other acetylenic carbon atom. This trend is the same as that in the vinylidene rearrangement of internal alkynes at a group 8 metal center.

scholarly journals Formation Mechanism of a Nonterrestrial C6H Radical: An Ab Initio/RRKM Study on the Reaction of Tetracarbon with Acetylene

2019 ◽  
Author(s):  
Tong Zhu ◽  
Chih-Hao Chin ◽  
John ZH Zhang
Keyword(s):  
Hydrogen Atom ◽  
Ab Initio ◽  
Rate Constants ◽  
Kinetic Equations ◽  
Branching Ratios ◽  
The Other ◽  
Formation Mechanisms ◽  
Hydrogen Elimination ◽  
Carbon Carbon Bond ◽  
Product Branching

This study examined the formation mechanisms of singlet (rhombic) and triplet (linear) C4 with acetylene by using accurate ab initio CCSD(T)/cc-pVTZ/B3LYP/6-311G(d,p) calculations, followed by a kinetic analysis of various reaction pathways and computations of relative product yields in combustion and planetary atmospheres. These calculations were combined with the Rice–Ramsperger–Kassel–Marcus (RRKM) calculations of reaction rate constants for predicting product-branching ratios, which depend on the collision energy under single-collision conditions. The results show that the initial reaction begins with the formation of an intermediate t-i2, with entrance barriers of 3.8 kcal/mol, and an intermediate s-i1 without entrance barriers. On the triplet surface, the t-i2 rearranged the other C6H2 isomers, including t-i3, t-i4, and t-i6, through hydrogen migration; the t-i2, t-i3, t-i4, t-i5, and t-i6 isomers lost a hydrogen atom, and produced the most stable linear isomer of C6H, with an overall reaction exothermicity of 11 kcal/mol. Hydrogen elimination from the t-i10 isomer led to the formation of the annular C6H isomer, HC3C3 + H, at 23.9 kcal/mol above l-C4 + C2H2. On the singlet surfaces, s-i1 rearranged the other C6H2 isomers, including s-i2 and s-i4, through carbon–carbon bond cleavage. The s-i6 and s-i11 isomers also lost a hydrogen atom, and produced the linear C6H radical. Hydrogen elimination from the s-i4 isomer led to the formation of the annular C6H isomer. The s-i5 lost a hydrogen atom, and produced the six-member ring c-C6H isomer, at 2.1 kcal/mol higher than l-C4 + C2H2. The 1,1-H2 loss from the s-i10 isomer produced the linear hexacarbon l-C6 + H2 product, with an endothermicity of 2.3 kcal/mol and a 1,1-H2 loss from the s-i11 isomer, producing in the cyclic hexacarbon c-C6 + H2 product, with an exothermicity of 11.2 kcal/mol. The product-branching ratios obtained by solving kinetic equations with individual rate constants calculated using the RRKM and VTST theories for determining the collision energies between 5 kcal/mol and 25 kcal/mol show that l-C6H + H is the dominant reaction product, whereas HC3C3 + H, l-C6 + H2, c-C6H + H, and c-C6 + H2 are minor products with branching ratios. The s-i6 isomer was calculated to be the most stable C6H2 species, even more favorable than t-i3 (by 76 kcal/mol).

ROTAMERISM DURING DEMETHYLATION OF THE 2,5-DIMETHOXY-2,5-DIMETHYL-3,4-DIPHENYLHEXANES

1954 ◽  
Vol 32 (8) ◽  
pp. 729-743 ◽  
Author(s):  
J. G. Smith ◽  
George F Wright
Keyword(s):  
The Other ◽  
Stable Conformation ◽  
Carbon Bond ◽  
Other Hand ◽  
Carbon Carbon Bond ◽  
Central Carbon

The fission of methanol from the diastereomeric 2,5-dimethoxy-2,5-dimethyl-3,4-diphenylhexanes leads to products which are best explained in terms of restriction about the central carbon-carbon bond. As would be expected from its stable conformation the dd,ll diastereomer easily forms the 2,2,5,5-tetramethyl-3,4-diphenyltetrahydrofuran, but the meso diastereomer forms a tetrahydrofuran with difficulty. On the other hand the meso diastereomer readily undergoes Friedel-Crafts types of condensation leading in different media to either 3,3-dimethyl-1-isopropenyl-2-phenylindane, 3,3-dimethyl-1-isopropyl-2-phenylindene or 5,5,10,10-tetramethyl-4b,5,9b, 10-tetrahydroindeno[2,1-α]-indene. These indenes are the expected products from a consideration of the conformation of the meso-dimethoxydimethyldiphenylhexane which is most free from steric restriction.

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