The stereochemistry of the Wittig reactions of allylic phosphoranes and phosphonate esters with aldehydes

1977 ◽  
Vol 55 (7) ◽  
pp. 1218-1228 ◽  
Author(s):  
Richard Neville Gedye ◽  
Kenneth Charles Westaway ◽  
Parkash Arora ◽  
Robert Bisson ◽  
Aly Hamdy Khalil
Keyword(s):  
Double Bond ◽  
Main Product ◽  
Triethyl Phosphite ◽  
Geometric Isomer ◽  
Major Product ◽  
General Mechanism ◽  
Phosphonium Salts ◽  
Phosphonate Esters ◽  
Wittig Reactions

Methyl Z- and E-4-bromo-3-methylbut-2-enoate 13 and 14 react with triethyl phosphite stereospecifically with retention of configuration to give the corresponding Z- and E-phospho-nate esters 8 and 9. The Z- and E-phosphonates react with aldehydes with extensive stereomutation of the double bond. Rapid equilibration to a mixture of one part E-phosphonate to two parts Z-phosphonate occurs when either geometric isomer is treated with base. Despite this, the E-2,E-4 ester 16 is the chief product of the reaction. Methyl E-β-ionylideneacetate 16b is the major product of the reaction of either isomer with β-cyclocitral and with cyclohexene car-boxaldehyde only the E-2,E-4 isomer 16c is formed. Benzaldehyde reacts with the phosphonates to give a mixture of the E-2,E-4 and Z-2,E-4 isomers 16a and 15a in a 4:1 ratio. Although the corresponding Z- and E-phosphonium salts 6 and 7, obtained stereospecifically from the bromo esters, react by the same general mechanism as the phosphonates the main product with benzaldehyde is the Z-2,Z-4 isomer 17a.

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

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.

Intramolecular Michael Addition of N- and O-Centred Nucleophiles to Tethered Acrylates. The Role of Double-Bond Geometry in Controlling the Diastereo- selectivity of Cyclizations Leading to 2,6-Disubstituted Tetrahydropyrans and Piperidines.

1998 ◽  
Vol 51 (1) ◽  
pp. 9 ◽  
Author(s):  
Martin G. Banwell ◽  
Brett D. Bissett ◽  
Chinh T. Bui ◽  
Ha T. T. Pham ◽  
Gregory W. Simpson
Keyword(s):  
Double Bond ◽  
Total Synthesis ◽  
Michael Addition ◽  
Reductive Amination ◽  
Major Product ◽  
Enantioselective Synthesis ◽  
Cyclization Reactions ◽  
Glandular Secretion

The oxyanion derived from hydroxyacrylate E-(5) undergoes smooth intramolecular Michael addition to give the trans-2,6-disubstituted tetrahydropyran (7) as the major product of reaction. In contrast, the oxyanion obtained from isomer Z-(5) cyclizes to give the cis-2,6-disubstituted tetrahydropyran (6) as the major product. Such chemistry has been extended to the enantioselective synthesis of (+)-(6) the acquisition of which constitutes a formal total synthesis of acid (+)-(2), a constituent of the glandular secretion from the civet cat (Viverra civetta). Reductive amination of keto acrylate (12) affords an intermediate amine which cyclizes, in situ, to give the cis-2,6-disubstituted piperidine (26). Analogous treatment of compound (13) delivers the isomeric trans-2,6-disubstituted piperidine (27) as the exclusive product of reaction. Transition state structures have been proposed to account for the diastereoselectivities observed in all of the cyclization reactions.

Reaktionen koordinierter Liganden, III [1]. Stabilisierung von Dimenthyldiphosphen und Menthylphosphiniden als Brückenliganden in Metallcarbonylkomplexen / Reaction of Coordinated Ligands, III [1]. Stabilization of Dim enthyldiphosphene and Menthylphosphinidene as Bridging Ligands in Metal Carbonyl Complexes

1986 ◽  
Vol 41 (5) ◽  
pp. 629-639 ◽  
Author(s):  
Anna-Margarete Hinke ◽  
Axel Hinke ◽  
Wilhelm Kuchen ◽  
Wolfgang Hönle
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Complex Formation ◽  
Main Product ◽  
Metal Carbonyl ◽  
Crystal Structure Analysis ◽  
Carbonyl Complexes ◽  
Bridging Ligands ◽  
Metal Carbonyl Complexes ◽  
Chromium Compounds

Abstract Reduction of MentPBr2M(CO)5 1 (M = Cr, W) with magnesium in THF yields the diphos­phene complex (CO)5M(Ment)P=P(Ment)M(CO)5 2 as the main product. In addition, a phosphinidene complex, (CO)5M(Ment)PM(CO)5 (3) is also formed. The latter is obtained in larger amounts, if the reaction is carried out in the presence of M(CO)5THF. The proposed structures are confirmed by NMR and UV data as well as - in the case of the chromium compounds (2a, 3a) - by crystal structure analysis. Compound 2a is obtained only as the frans-isomer. The P-P distance in 2a (204.0 pm) indicates a double bond which does not participate in the complex formation. The P-Cr distance in 3a (average: 230.3 pm) is within the low est range found for this element combination. Reaction of 2a with LiAlH4 yields the diphosphane complex (CO)5CrMent(H)P-P(H)MentCr(CO)5 4 as a mixture of “meso” and “rac” diastereomers.

The Reaction of 5-Substituted-2-Norbornenes with Phenylselenyl Chloride

2008 ◽  
Vol 61 (4) ◽  
pp. 283 ◽  
Author(s):  
D. Alan R. Happer ◽  
Thomas Francis ◽  
Jonathan M. White
Keyword(s):  
Double Bond ◽  
Product Distribution ◽  
Major Product ◽  
Factors Influencing

In dichloromethane, 5-substituted-2-norbornenes add phenylselenyl chloride across the double bond to give adducts in which the phenylselanyl substituent is exo and the chloro endo. The relative yields of the two regioisomeric adducts are reported for several of these. For most, the formation of the 2-chloro-3-phenyselanyl adduct is favoured. The main exceptions are when the 5-substituent is exo and a good resonance donor, where the 3-chloro-2-phenylselanyl adduct is the major product. Possible factors influencing the product distribution are discussed.

Synthesis of Non-Conjugated Trienes via In Situ Hydrovinylation/Wittig Olefination of Unsaturated Phosphonium Salts

Synthesis ◽  
2017 ◽  
Vol 50 (08) ◽  
pp. 1711-1720 ◽  
Author(s):  
Gerhard Hilt ◽  
Monika Ballmann ◽  
Felicia Weber ◽  
Lars Sattler
Keyword(s):  
Double Bond ◽  
Phosphonium Salts ◽  
The Third ◽  
Wittig Olefination ◽  
Conjugated Trienes

A cobalt-catalysed 1,4-hydrovinylation reaction is successfully applied in a sequential three-component transformation of unsaturated phosphonium bromides, 1,3-dienes, and aldehydes leading to non-conjugated products with a 1,4-diene subunit in good to excellent yields. The hydrovinylation provides regioselectively diene structures with one exo double bond whereas the third double bond can be introduced via an in situ Wittig or Horner–Wadsworth–Emmons olefination leading to 1,4,7-trienes suitable for further double bond functionalisations.

Déplacements homolytiques intramoléculaires. 2. Décomposition du perpentène-4 oate de tert-butyle dans les éthers

1984 ◽  
Vol 62 (11) ◽  
pp. 2385-2390 ◽  
Author(s):  
A. Kharrat ◽  
C. Gardrat ◽  
B. Maillard
Keyword(s):  
Double Bond ◽  
Main Product ◽  
Similar Reaction ◽  
Tert Butyl ◽  
Lower Temperature ◽  
Induced Decomposition

The thermolysis of tert-butyl perpent-4-enoate 1 in THF led to several compounds; the main product, 5-(2-tetrahydrofuryl)-4-pentanolide (yield 42%) comes from an induced decomposition of the perester occurring with the addition of 2-tetrahydrofuryl radical to the double bond. A similar reaction was performed at a lower temperature, using butyl perdicarbonate as initiator, but did not define the mechanism (concerted or two-step). The thermolysis of 1 in ethers (THP, oxepane, 1,4-dioxane, dipropyl ether) appears to be a useful synthetic tool: several new γ-lactones have been obtained in this way.

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