Wittig reactions of ylide anions derived from stabilised ylides

1989 ◽  
pp. 568 ◽  
Author(s):  
Eugene G. Mckenna ◽  
Brian J. Walker
Keyword(s):  
Wittig Reactions

Synthesis of 8-HEPE and 10-HDoHE in both (R)- and (S)-Forms via Wittig Reactions with COOH-Ylides

Synlett ◽  
2019 ◽  
Vol 30 (03) ◽  
pp. 338-342
Author(s):  
Yuta Suganuma ◽  
Shun Saito ◽  
Yuichi Kobayashi
Keyword(s):  
Docosahexaenoic Acid ◽  
Eicosapentaenoic Acid ◽  
Wittig Reaction ◽  
Phosphonium Salt ◽  
Wittig Reactions

Wittig reactions using carboxy (CO2H) ylides derived from a carboxylic phosphonium salt and NaN(TMS)2 (NaHMDS) in a 1:1 ratio were applied to the synthesis of 8-HEPE and 10-HDoHE, which are metabolites of eicosapentaenoic acid and docosahexaenoic acid, respectively. The attempted Wittig reaction of 3-(TBS-oxy)pentadeca-4E,6Z,9Z,12Z-tetraenal with the carboxy ylide (2 equiv) derived from Br– Ph3P+(CH2)4CO2H and NaHMDS (1:1) competed with the elimination of the TBS-oxy group at C3 to give a mixture of the Wittig product and the elimination product in 45–50% and 30–40% yields, respectively. The elimination was suppressed completely by using three equiv of the carboxy ylides in THF/HMPA (7–8:1), and the subsequent desilylation gave 8-HEPE in (R)- and (S)-forms. Similarly, both enantiomers of 10-HDoHE were synthesized.

Silylated Ylides as Components for Wittig Reactions

1973 ◽  
Vol 12 (4) ◽  
pp. 321-322 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Herbert Stühler
Keyword(s):  
Wittig Reactions

Hydrophobic Encapsulated Phosphonium Salts-Synthesis of Weakly Coordinating Cations and their Application in Wittig Reactions

2015 ◽  
Vol 21 (25) ◽  
pp. 9119-9125 ◽  
Author(s):  
Ralf Moritz ◽  
Manfred Wagner ◽  
Dieter Schollmeyer ◽  
Martin Baumgarten ◽  
Klaus Müllen
Keyword(s):  
Phosphonium Salts ◽  
Weakly Coordinating ◽  
Wittig Reactions

Crystal structures of highly stabilized ylides: methyl(3-methoxy,2-methoxycarbonylbenzoyl) triphenyl- phosphoranylideneacetate and methyl(2-methoxycarb-6-nitrobenzoyl)triphenyl phos phoranyl ideneacetate and the salt methyl(triphenylphosphoranylidene)acetate tetrafluoroborate

1998 ◽  
Vol 76 (12) ◽  
pp. 1844-1852
Author(s):  
Fernande D Rochon ◽  
Robert Melanson ◽  
Margaret M Kayser
Keyword(s):  
Key Words ◽  
Crystal Structures ◽  
Nitro Derivative ◽  
Transient Species ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ionic Salt ◽  
Higher Temperature ◽  
Cyclic Anhydrides ◽  
Wittig Reactions

At lower temperatures stabilized ylides react with unsymmetrically substituted phthalic anhydrides to give two acyclic adducts. When the reactions are allowed to proceed at higher temperature enol lactones are formed. Identification of the acyclic intermediates was necessary to understand the mechanism of these Wittig reactions. The transient species trapped in the reaction with trimethyloxonium tetrafluoroborate were unambiguously identified by crystallographic methods. The crystal structures of the tetrafluoroborate salt of methyl(triphenylphosphoranyl idene)- acetate (8), methyl(3-methoxy,2-methoxycarbonylbenzoyl)triphenylphosphoranylideneacetate (6β), and methyl(2-methoxycarbonyl,6-nitrobenzoyl)triphenylphosphoranylideneacetate (7α) were studied by X-ray diffraction. The ionic salt (8) is monoclinic, P21c,a= 12.640(5), b = 13.945(9), c = 14.825(6) Å, β = 125.32(3)°, Z = 4, and R = 0.065 (F >5.4 σ(F)). Crystal 6 β is monoclinic, P21c,a = 16.391(16), b = 9.029(6), c = 19.835(19) Å, β = 116.60(6)°, Z = 4, and R = 0.070 (F > 4.6 σ(F)), while crystal 7α is also monoclinic, P21c,a = 9.513(5), b = 9.361(3), c = 30.908(13) Å, β = 98.42(3)°, Z = 4, and R = 0.057 (F >5 σ(F)). In the BF 4- salt (12), the four P-C distances are equal (1.791(5)-1.801(7) Å) with identical tetrahedral angles. For the two triphenylphosphoranylideneacetate compounds, the fourth P-C(1) bond is shorter (1.762(6)-1.734(5) Å) than the three P-C(Ph) bonds (avg. 1.809(5) Å). The angles C(1)-P-C(Ph) are also larger (avg. 112.9(2)° for 6β and 111.9(2)° for 7α) than the C(Ph)-P-C(Ph) angles (avg. 105.8(2)° for 6 β and 106.9(2)° for 7α). These values suggest a multiple nature for the P-C(1) bond. In the nitro derivative, the nitro and the ester groups are disordered equally in positions 2 and 6. Key words: Wittig reactions, cyclic anhydrides, stabilized ylide, phosphoranylidenes, crystal structures.

SYNTHESIS OF ISOTOPICALLY LABELLED OLEFINS VIA THE WITTIG REACTION

1965 ◽  
Vol 43 (5) ◽  
pp. 1614-1624 ◽  
Author(s):  
J. G. Atkinson ◽  
M. H. Fisher ◽  
D. Horley ◽  
A. T. Morse ◽  
R. S. Stuart ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Dimethyl Sulfoxide ◽  
Wittig Reaction ◽  
Low Molecular Weight ◽  
Phosphonium Salts ◽  
Reaction Conditions ◽  
Selective Labelling ◽  
Wittig Reactions

A new application of the Wittig reaction to the preparation of olefins of low molecular weight which allows selective labelling in the vinyl or allyl positions with isotopes of hydrogen and carbon has been developed. Using the modification of the Wittig reaction introduced by E. J. Corey, in which a solution of the methylsulfinyl carbanion in dimethyl sulfoxide serves as the base, a series of olefins from C2 to C8 were synthesized. The synthesis was applied to the preparation of the following labelled compounds: 5-methylene-14C-bicyclo[2.2.1]hept-2-ene; propene-1-14C; 1-butene-1-14C; propene-1-d1; 2-methylpropene-1,1-d2; 2-methyl-d3-propene-3,3,3-d3; 2-methyl-2-butene-4,4,4-d3; 2-methyl-d3-2-butene-1,1,1-d3; methylene-d2-cyclohexane. For the synthesis of carbon-labelled olefins the reaction has few limitations since the intermediates and products are isotopically stable under the reaction conditions. Deuterium-labelled olefins can be obtained from deuterated formaldehyde or β-deuterated phosphonium salts, but α-deuteroketones and aldehydes and α-deuterophosphonium salts lose the isotope to the solvent.In all the Wittig reactions, benzene was formed as a by-product in 10–15% yield. The mechanism of benzene formation is probably analogous to that proposed by Seyferth involving the decomposition of a pentacovalent phosphorous intermediate.

Structural Characterization and Electrochemical Study of Novel Ferrocene Derivatives Prepared from [(β-Ferrocenylvinyl)imino]phosphorane by Aza Wittig Reactions

1997 ◽  
Vol 16 (26) ◽  
pp. 5836-5843 ◽  
Author(s):  
Pedro Molina ◽  
Aurelia Pastor ◽  
M. Jesús Vilaplana ◽  
M. Desamparados Velasco ◽  
M. Carmen Ramirez de Arellano
Keyword(s):  
Structural Characterization ◽  
Electrochemical Study ◽  
Ferrocene Derivatives ◽  
Wittig Reactions

7H-Imidazo[1.2-a]-und -[1.5-a]azepin-7-one / 7H-Imidazo[1,2-a]-and -[1,5-a]azepine-7-ones

1981 ◽  
Vol 36 (3) ◽  
pp. 383-385 ◽  
Author(s):  
Ulrich Wolf
Keyword(s):  
Dimethylformamide Dimethylacetal ◽  
Wittig Reactions

Wittig reactions of imidazole-2- and 4(5)-carboxaldehyde yield the compounds 3 and 4. These vinyl ketones react with N,N-dimethylformamide-dimethylacetal to produce the eneamino-ketones 5 and 6, which are converted into the imidazo-azepine-7-ones (7) and 8.

Total Synthesis of Resolvin T4

Synlett ◽  
2021 ◽  
Author(s):  
Narihito Ogawa ◽  
Kohei Arai ◽  
Yuichi Kobayashi
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Transfer Hydrogenation ◽  
Asymmetric Transfer Hydrogenation ◽  
Ring Opening Reaction ◽  
Propargylic Alcohol ◽  
Chiral Centers ◽  
Wittig Reactions

AbstractA total synthesis of resolvin T4 was achieved by connecting three intermediates by Wittig reactions. The enal in the C1–C10 part was constructed through reduction of a propargylic alcohol with Red-Al followed by oxidation. The enal moiety in the C11–C16 part was synthesized by a ring-opening reaction of a silyl epoxide followed by a Peterson elimination. The chiral centers at C7 and C13 were constructed by ruthenium-catalyzed asymmetric transfer hydrogenation.

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