Reaktive E =C (p—p)π-Systeme, X Darstellung und Reaktivität von Perfluor-3-phosphapent-2-en / Reactive E = C (p-p)π-Systems, X Preparation and Reactivity of Perfluoro-3-phosphapent-2-ene

1986 ◽  
Vol 41 (8) ◽  
pp. 974-980 ◽  
Author(s):  
Joseph Grobe ◽  
Jürgen Szameitat
Keyword(s):  
Double Bond ◽  
Room Temperature ◽  
Diels Alder ◽  
Cycloaddition Reactions ◽  
Dilute Solution ◽  
Concerted Mechanism ◽  
Thermal Elimination ◽  
Acidic Compounds ◽  
New Compounds ◽  
First Time

Abstract Perfluoro-3-phosphapent-2-ene F5C2 P =C (F )CF3 (1) has been prepared for the first time by thermal elimination of trimethyltin fluoride Me3SnF from trim ethylstannyl-bis(pentafluoroethyl)- phosphane Me3SnP(C2F5) 2 at 300 °C/10−3 Torr. 1 is found to be less stable than F3CP = CF2 in dilute solution at room temperature, forming several 1,3-diphosphabutane dimers. Reactivity studies accomplished till now include (i) the dienophilicity of 1 in [2+4] cycloaddition reactions with butadiene, 2,3-dim ethylbutadiene, cyclopentadiene, 1,3-cyclohexadiene, 2-methylbutadiene, and 2-methylfuran leading by a concerted mechanism to the Diels-Alder-adducts 2-7 in about 80% yield, (ii) the addition of proton acidic compounds HX (X = OMe, Br, NMe2, NEt2) to the PC double bond affording chiral phosphanes of the type F5C2 P(X)CF(CF3)H [X = OMe (8). Br (9). NMe2 (10). NEt2 (11)]. thus proving a stronger polarity δ+P =δ−C for 1 than for F3CP = CF2. New compounds have been characterized by NMR and MS measurements.

scholarly journals Enhancing the reactivity of 1,2-diphospholes in cycloaddition reactions

2015 ◽  
Vol 11 ◽  
pp. 169-173 ◽  
Author(s):  
Almaz Zagidullin ◽  
Vasili Miluykov ◽  
Elena Oshchepkova ◽  
Artem Tufatullin ◽  
Olga Kataeva ◽  
...  
Keyword(s):  
Room Temperature ◽  
Cycloaddition Reaction ◽  
Alder Reaction ◽  
Diels Alder ◽  
Alkyl Halides ◽  
Ethyl Iodide ◽  
Para Position ◽  
Cycloaddition Reactions ◽  
Diels Alder Reaction ◽  
Heating Up

Two different approaches have been employed to enhance the reactivity of 1-alkyl-1,2-diphospholes – the introduction of electron-withdrawing groups either at the phosphorus atoms or in the para-position of the arene ring. The alkylation of sodium 1,2-diphospha-3,4,5-triphenylcyclopentadienide with alkyl halides Hal-CH2-R (R = CN, COOEt, OMe, CH2OEt) results in corresponding 1-alkyl-3,4,5-triphenyl-1,2-diphospholes (alkyl = CH2CN (1a), CH2COOEt (1b), CH2OMe (1c), and (CH2)2OEt (1d)), which spontaneously undergo the intermolecular [4 + 2] cycloaddition reactions at room temperature to form the mixture of the cycloadducts, 2a–c, respectively. However the alkylation of sodium 1,2-diphospha-3,4,5-tri(p-fluorophenyl)cyclopentadienide with ethyl iodide leads to stable 1-ethyl-3,4,5-tris(p-fluorophenyl)-1,2-diphosphole (1e), which forms the [4 + 2] cycloadduct 2,3,4,4a,5,6-hexa(p-fluorophenyl)-1-ethyl-1,7,7a-triphospha-4,7-(ethylphosphinidene)indene (2e) only upon heating up to 60 °C. With further heating to 120 °C with N-phenylmaleimide, the cycloadducts 2a–c and 2e undergo the retro-Diels–Alder reaction and form only one product of the [4 + 2] cycloaddition reaction 3a–с, 3e with good yields up to 65%.

scholarly journals Synthesis of 5-arylacetylene 1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

2021 ◽  
Author(s):  
Andrey I Puzanov ◽  
Dmitry S Ryabukhin ◽  
Anna S Zalivatskaya ◽  
Dmitriy N Zakusilo ◽  
Darya S Mikson ◽  
...  
Keyword(s):  
Double Bond ◽  
Dft Calculations ◽  
Reaction Mechanisms ◽  
Room Temperature ◽  
Triflic Acid ◽  
Activation Conditions ◽  
First Time ◽  
Vinyl Triflates ◽  
Derivatives Of ◽  
Acetylene Derivatives

Acetylene derivatives of 1,2,4-oxadiazoles, 5-(2-arylethynyl)-3-aryl-1,2,4-oxadiazoles, have been obtained, for the first time, from 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles by their bromination at the carbon-carbon double bond followed by di-dehydrobromination with NaNH2 in liquid NH3.  Reaction of the acetylene 1,2,4-oxadiazoles with arenes in neat triflic acid TfOH (CF3SO3H) at room temperature for 1 h result in the formation of E-/Z-5-(2,2-diarylethenyl)-3-aryl-1,2,4-oxadiazoles as products of regioselective hydroarylation of the acetylene bond. Addition of TfOH to acetylene bond of these oxadiazoles gives rise quantitatively to E-/Z-vinyl triflates. Reaction cationic intermediates have been studied by DFT calculations. The reaction mechanisms have been discussed.

scholarly journals Computational Study of the Stereoselectivity Profiles of the Diels-Alder Cycloaddition Reactions of Cyclopentadiene and Butadiene with Cyclopropenes

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Theoretical Models ◽  
Diels Alder ◽  
Cycloaddition Reactions ◽  
Free Energies ◽  
Differential Activation ◽  
Activation Free Energy ◽  
The Difference ◽  
First Time

The <i>endo</i> and <i>exo</i> stereoselectivities of the Diels-Alder (DA) cycloaddition reactions of 3,3-disubstituted cyclopropenes with butadiene and cyclopentadiene, the latter for the first time, were investigated by means of density functional and quantum chemical calculations for a comparison. To establish distinction between the selectivites, activation free energies were systematically estimated in the gas phase and also in solvents. The differential activation free energies clearly predict exclusive <i>endo</i> configuration of the products formed from the reaction of the unsubstituted cyclopropene with butadiene and cyclopentadiene. However, the results were found to be markedly different for the substituted cyclopropenes from available experimental selectivities. It was also discovered that butadiene and cyclopentadiene are markedly different in their respective stereospecific product yields, nevertheless the difference between the two was only a methylene group. The failure of the differential activation free energy approach to predict the experimental stereoselectivities of the DA reactions of several perhalocyclopropenes with cyclopentadiene is probably due to yet insufficient development of the various theoretical models dealing with the <i>endo</i> and <i>exo</i> DA preferences.

scholarly journals Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

2013 ◽  
Vol 9 ◽  
pp. 2137-2146 ◽  
Author(s):  
Peter A Wade ◽  
Alma Pipic ◽  
Matthias Zeller ◽  
Panagiota Tsetsakos
Keyword(s):  
Double Bond ◽  
Substituent Effects ◽  
Product Formation ◽  
Sigmatropic Rearrangement ◽  
Diels Alder ◽  
Initial Assessment ◽  
Concerted Mechanism ◽  
Rearrangement Process ◽  
Zwitterionic Intermediate ◽  
Nitronic Ester

The tin(IV)-catalyzed reaction of β-nitrostyrene with (E)-3-methyl-1,3-pentadiene in toluene afforded two major nitronic ester cycloadducts in 27% and 29% yield that arise from the reaction at the less substituted diene double bond. Also present were four cycloadducts from the reaction at the higher substituted diene double bond, two of which were the formal cycloadducts of (Z)-3-methyl-1,3-pentadiene. A Friedel–Crafts alkylation product from the reaction of the diene, β-nitrostyrene, and toluene was also obtained in 10% yield. The tin(IV)-catalyzed reaction of β-nitrostyrene with (Z)-3-methyl-1,3-pentadiene in dichloromethane afforded four nitronic ester cycloadducts all derived from the reaction at the higher substituted double bond. One cycloadduct was isolated in 45% yield and two others are formal adducts of the E-isomer of the diene. The product formation in these reactions is consistent with a stepwise mechanism involving a zwitterionic intermediate. The initially isolated nitronic ester cycloadducts underwent tin(IV)-catalyzed interconversion, presumably via zwitterion intermediates. Cycloadducts derived from the reaction at the less substituted double bond of (E)-3-methyl-1,3-pentadiene underwent a [3,3]-sigmatropic rearrangement on heating to afford 4-nitrocyclohexenes. Cycloadducts derived from the reaction at the higher substituted diene double bond of either diene failed to undergo a thermal rearrangement. Rates and success of the rearrangement are consistent with a concerted mechanism possessing a dipolar transition state. An initial assessment of substituent effects on the rearrangement process is presented.

Reaktive E=C(p-p)π-Systeme, VI [1] Reaktionen des Phosphaalkens F3CP=CF2 mit H-aciden Verbindungen/Reactive E = C(p-p)π-Systems, VI [1] Reactions of the Phosphaalkene F3CP = CF2 with H Acidic Compounds

1986 ◽  
Vol 41 (2) ◽  
pp. 149-161 ◽  
Author(s):  
Joseph Grobe ◽  
Duc Le Van ◽  
Jürgen Nientiedt
Keyword(s):  
Double Bond ◽  
Opposite Direction ◽  
Rate Of Reaction ◽  
Ph Dependent ◽  
Acidic Compounds ◽  
New Compounds ◽  
Derivatives Of

The reactions o f the perfluorophosphaalkene F3CP = CF2 (1) with HX compounds proceed via addition to the PC double bond yielding either secondary phosphanes F3CP(H)CF2X (X = OH, OR, NR2, PMe2) or PX derivatives F3CP(X)CF2H (X = Cl, Br, SMe, SeMe, AsMe2). The rate of reaction with H2O is strongly pH-dependent, but only at pH > 13 the opposite direction of addition is observed. Similar results are obtained for the addition of alcohols, for which the presence of OR- results in two effects: (i) Reversion of the addition direction to yield F3CP(OR)CF2H; (ii) HF elimination from F3CP(H)CF2OR to give substituted phosphaalkenes. With strong bases HNR2, the addition is followed immediately by HF elimination producing the surprisingly stable phosphaalkenes F3CP = C(F)NR2 (R = Me, Et). Secondary phosphanes of the type F3CP(H)CF2X (X = OMe, OEt, PMe2) are found to be suitable precursors for the preparation of novel heterosubstituted derivatives of 1 by elimination of HF with NMe3. New compounds were characterized by NMR, MS, GC/MS and GC/IR measurements.

scholarly journals Synthesis and Reactivity of Electron-Deficient 3-Vinylchromones

SynOpen ◽  
2021 ◽  
Vol 05 (03) ◽  
pp. 255-277
Author(s):  
Vyacheslav Y. Sosnovskikh
Keyword(s):  
Double Bond ◽  
Chemical Properties ◽  
Building Blocks ◽  
High Reactivity ◽  
Cycloaddition Reactions ◽  
Chemical Transformations ◽  
Pyrone Ring ◽  
The Past ◽  
Palladium Catalyzed ◽  
First Time

AbstractThe reported methods and data for the synthesis and reactivity of electron-deficient 3-vinylchromones containing electron-withdrawing­ groups at the exo-cyclic double bond are summarized and systematized for the first time. The main methods for obtaining these compounds are Knoevenagel condensation, Wittig reaction, and palladium-catalyzed cross-couplings. The most important chemical properties are transformations under the action of mono- and dinucleophiles, ambiphilic cyclizations, and cycloaddition reactions. The cross-conjugated and polyelectrophilic dienone system in 3-vinylchromones provides their high reactivity and makes these compounds valuable building blocks for the preparation of more complex heterocyclic systems. Chemical transformations of 3-vinylchromones usually begin with an attack of the C-2 atom and are accompanied by the opening of the pyrone ring followed by recyclization, in which the carbonyl group of chromone, an exo-double bond or a substituent on it can take part. The mechanisms of the reactions are discussed, the conditions for their implementation are described, and the yields of the resulting products are given. This review focuses on an analysis and generalization of the knowledge that has accumulated on the chemistry of electron-deficient 3-vinylchromones, mostly over the past 15 years.1 Introduction2 Synthesis of 3-Vinylchromones3 Reactions with Mononucleophiles4 Reactions with Dinucleophiles5 Ambiphilic Cyclization6 Cycloaddition Reactions7 Other Reactions8 Conclusion

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