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Alkene derivatives carbon nucleophile reactions

Formation of TT-allylpalladium complexes from alkenes and PdCl2, and the reaction of the complexes with carbon nucleophiles constitutes alkylation of alkenes with carbon nucleophiles via TT-allylpalladium complexes as a stoichiometric reaction, offering a method of oxidative functionalization of alkenes, and can be applied to syntheses of a number of natural products [85]. For example, functionalization of pinene (186) was carried out via the reaction of the TT-allylpalladium 187 with a phenylsulfinyl group to give 188, and converted to the pinene derivative 189 [86]. TT-Allyl complex formation takes place particularly easily from the a, - or unsaturated carbonyl compounds. The reaction of the complex 191, formed from 3-penten-2-one (190), with a carbon nucleophile to lead to 192 is an example of y-alkylation of a,jS-unsaturated ketones or esters [87]. [Pg.54]

Among several propargylic derivatives, the propargylic carbonates 3 were found to be the most reactive and they have been used most extensively because of their high reactivity[2,2a]. The allenylpalladium methoxide 4, formed as an intermediate in catalytic reactions of the methyl propargylic carbonate 3, undergoes two types of transformations. One is substitution of cr-bonded Pd. which proceeds by either insertion or transmetallation. The insertion of an alkene, for example, into the Pd—C cr-bond and elimination of/i-hydrogen affords the allenyl compound 5 (1.2,4-triene). Alkene and CO insertions are typical. The substitution of Pd methoxide with hard carbon nucleophiles or terminal alkynes in the presence of Cul takes place via transmetallation to yield the allenyl compound 6. By these reactions, various allenyl derivatives can be prepared. [Pg.453]

The most common method to prepare cyclopropenyl derivatives is the reaction between an electrophilic carbenoid and an alkene. On the other hand, sp3-geminated organodimetal compounds possess two nucleophilic sites on the same carbon, so should lead to nucleophilic [2+ 1] reaction with 1,2-diketones. Indeed, the reaction of bis(iodozincio)methane (3) with 1,2-diketones shows a novel [2+1] reaction to form c -cyclopropanediol diastereoselectively as shown in Scheme 3467. [Pg.671]

Active methylene and methine compounds bearing a leaving group (X) on the y-carbon atom can afford cyclopropyl derivatives via 1,3-elimination of HX. 1,2-Elimination to give alkenes and direct nucleophilic substitution by base may compete with the 1,3-elimination, particularly in the preparation of excessively strained cyclopropyl derivatives. The preferred reaction course is, however, highly dependent on reaction conditions, especially on the nature of the base and solvent employed, as exemplified by the reactions of 4 (equation 7) 4. [Pg.264]

Otherwise, unsaturation may be introduced by use of carbonyl-containing carbohydrate derivatives and carbon nucleophiles that contain alkene (or, if desired, alkyne) functionality, a notable illustration being the tin-or indium-mediated C-l allylation of unprotected sugars. As an illustration, D-arabinose, treated with allyl bromide in aqueous ethanol in the presence of tin gives, after acetylation, 278 in 85% yield.258 In this procedure aldoses react better than do ketoses, and pentoses better than hexoses. More usual is the use of Grignard reactions to give, for example, the octynes 279. [Pg.106]

Type III reactions proceed by attack of a nucleophile at the central sp carbon of the allenyl system of the complexes 5. Reactions of soft carbon nucleophiles derived from active methylene compounds, such as /i-kcto esters or malonates, and oxygen nucleophiles belong to this type. The attack of the nucleophile generates the intermediates 9, which are regarded as the palladium-carbene complexes 10. The intermediates 9 pick up a proton from the active methylene compound and n-allylpalladium complexes 11 are formed, which undergo further reaction with the nucleophile, as expected, and hence the alkenes 12 are formed by the introduction of two nucleophiles. [Pg.201]

It was determined that carbon nucleophiles derived from carbon acids with p/fa > 22 or so are sufficiently reactive to combine with the diene ligand rapidly at —78°C to produce an anionic intermediate (Scheme 25). With a few exceptions, the regioselectivity favors formation of the homoallyl anionic complex from addition at C-2, by kinetic control. This intermediate can be quenched with protons to give the terminal alkene, or can react with excess CO to produce an acyl iron intermediate. Following the recipes of Collman s reaction, the acyl iron intermediate can lead to methyl ketones, aldehydes, or carboxylic acids. The processes are illustrated with the 1,3-cyclohexadiene complex (Scheme 25). ... [Pg.3305]

Research in the laboratory of H.M.I. Osborn showed that the use of cyclohexene derivatives as nucleophiles in the Lewis acid-mediated Type I carbon-Ferrier reaction of 3-0-acetylated glycals can be used to prepare unsaturated 3-linked C-disaccharides. The incorporation of the alkene took place with one equivalent of glucal in the presence of boron-trifluoride etherate in 33% yield. The desired C-disaccharide was obtained by selective hydrogenation of the exocyclic double bond in the presence of an endocyclic one. [Pg.169]

With an acceptor-substituted alkene moiety tethered to the molecule, the intermediate silyl enol ether may undergo an intramolecular [2-I-2] cycloaddition.The silyl-assisted addition of hydrogen halides to cyclopropanes is not restricted to ketones with carbonyl groups as activating function or iodide as nucleophile. Esters and other acid derivatives underwent similar reactions when treated with iodotrimethylsilane alone or in the presence of an additional catalyst such as mercury(II) or zinc(II) chloride.Subsequent treatment of the y-iodo ester with potassium carbonate in tetrahydrofuran gave the respective y-butyrolactones in good yield. [Pg.2098]

The classical Vilsmeier-Haack reaction - involves electrophilic substitution of a suitable carbon nucleophile with a chloromethyleneiminium salt, for example salt (1). Suitable carbon nucleophiles are generally electron-rich aromatic compounds such as V,N-dimethylaniline (2), alkene derivatives such as styrene (3) or activated methyl or methylene compounds such as 2,4,6-trinitrotoluene (4 Scheme I). These compounds (2-4) react with salt (1) giving, after loss of hydrogen chloride, the corresponding im-inium salts (5-7). Hydrolysis of iminium salt (5) affords aldehyde derivative (8) and this transformation (Ar—H - Ar—CHO) is the well-known Vilsmeier-Haack formylation reaction. Hydrolysis of iminium... [Pg.777]

Finally, the C—C bond formation by the reaction of 7r-complexes of Pd derived from alkenes, dienes, and other 7r-compounds with enolates and related carbon nucleophiles a la Wacker reaction (Method VI in Scheme 1) provides yet another alternative, as exemplified by the results shown in Scheme For a more general discussion of the C—C bond formation via Wacker-type reaction of Pd rr-complexes with carbanions, the reader is referred to Sect. V.3.4. [Pg.696]

The Morita-Baylis-Hillman reaction is, in general, a carbon-carbon bondforming reaction of an a,(3-unsaturated compound with an aldehyde mediated by an organic nucleophilic base resulting in the formation of an allylic alcohol. Morita reported the use of a phosphine as catalyst and Baylis and Hillman used a tertiary amine. Variation of the electrophile to electron-deficient alkenes in a Michael-Michael elimination sequence leads to homo- and heterodimerisation and is known as the Rauhut-Currier reaction. The electrophilic aldehyde could be substituted by an imine or derivative in the aza-Morita-Baylis-Hillman reaction. Recently, there has been an increase in the use of this reaction for the construction of many different targets using many different amine derived catalysts. Scheme 2.2 shows a general view of this reaction and the accepted mechanism. ... [Pg.10]

Several examples of gold-catalyzed addition reactions of carbon nucleophiles to unactivated alkenes have been reported in recent years. Yao and Li obtained adducts with high regioselectivity from 3-diketones and various alkenes (styrene derivatives, conjugated dienes, enol ethers) in the presence of cationic gold species prepared in situ from AuCls and AgOTf (Scheme 4-15). This hydroalkylation is... [Pg.444]

The structure of 71 indicates that the Hg is at the less hindered carbon atom, and experiments show that there is a carbocation intermediate. The reaction with mercuric acetate can be related to the reaction of HBr in that the more stable carbocation is formed as a new C-Hg or C-H bond is formed. It is known that alkenes react with an acid catalyst and water to produce an alcohol (see Section 10.3). Using this as an analogy, the OH unit in 71 is derived from the reaction of the nucleophilic water with an intermediate carbocation. [Pg.448]


See other pages where Alkene derivatives carbon nucleophile reactions is mentioned: [Pg.62]    [Pg.38]    [Pg.156]    [Pg.224]    [Pg.68]    [Pg.659]    [Pg.357]    [Pg.85]    [Pg.357]    [Pg.45]    [Pg.102]    [Pg.276]    [Pg.230]    [Pg.3548]    [Pg.286]    [Pg.669]    [Pg.169]    [Pg.212]    [Pg.3547]    [Pg.114]    [Pg.65]    [Pg.1923]    [Pg.1342]    [Pg.372]    [Pg.627]   


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Alkene derivatives reactions

Alkenes carbon nucleophiles

Alkenes derivatives

Carbon alkenes

Carbon nucleophile

Carbon nucleophiles

Nucleophiles alkenes

Nucleophiles derivatives

Nucleophilic reactions alkenes

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