Allylation and Propargylation

In the past decade much effort in organoindium chemistry has been devoted to study of carbonyl allylation and aUylindation of carbon-carbon multiple bonds with allylic indium reagents. Apart from the conventional transmetalation of allyl-lifhium or aUyl Grignard reagents with indium(III) halides, a method widely used for preparation of allyhndium(III) compounds is the oxidative addition of metallic indium or indium(I) iodide to aUyhc substrates [3, 6]. Transmetalation of allylstan-nane with indium(III) chloride also gives allylindium(III) [7]. Allylindium(I) was recently prepared by transmetalation of allylmercury with metallic indium in water this compound is regarded as an intermediate in the allylation of carbonyl compounds in aqueous media [8]. A new method of preparation of allylic in-dium(III) reagents - reductive transmetalation of a 7r-allylpalladium(ll) complex with indium(I) salts has been reported this enables the use of a wide variety of allylic compounds and solvents [9]. 

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Copper(I) halide-catalyzed coupling reactions of perfluoro Gngnard reagents with allyl and propargyl halides have been reported [256], The acetylenic copper compound may be an intermediate in these reactions. 

With enamines of cyclic ketones direct C alkylation occurs with allyl and propargyl as well as alkyl halides. The reaction is again sensitive to the polarity of the solvent (29). The pyrrolidine enamine of cyclohexanone on reaction with ethyl iodide in dioxane gave 25% of 2-ethylcyclohexanone on hydrolysis, while in chloroform the yield was increased to 32%. 

CH2(OMe)2, CH2CI2, TfOH, 4 h, 25°, 65% yield. This method is suitable for the formation of primary, secondary, allylic, and propargylic MOM ethers. Tertiary alcohols fail to give a complete reaction. 1,3-Diols give methylene acetals (89% yield). 

D. The Double [2,3]Sigmatropic Rearrangement of Allylic and Propargylic Sulfoxylates... 

Cathodic behaviour of allylic and propargylic sulphones in low-acidity... 

Benzylic, allylic and propargylic positions enhance the cathodic cleavage rate of C— heteroatom bonds as, for example, in the reduction of benzylic and allylic halides or alcohols56. Similar activated sulphones, due to their acidity, are in a class apart. Figure 8 shows the similitude between the cathodic behaviour of an allylic sulphone and its isomer, i.e., the corresponding vinylic sulphone when the electrolyses are run in an aprotic solvent. However, in the presence of an excess of proton donor, discrepancies appear. 

A small library of highly functionalized pyrrolines 95 was synthesized by reaction of allylic and propargylic isocyanides 94 with thiols followed by radical cyclization (Scheme 33). The radical reaction was carried out using a radical initiator (AIBN) under flash heating microwave irradiation [67]. 

Allylic and Propargylic Coupling With a Halide Substrate... 

The difference in reactivity between the anions generated from LDA and LHMDS is difficult to rationalize, but nonetheless reproducible. The same effect has been observed with substituted allyl halides and propargyl halides. Instability of the product under the reaction conditions may account for this phenomenon. Thus, for alkylation of allylic and propargylic halides, LHMDS and KHMDS are the bases of choice. 

Reisse used activated zinc for aqueous Barbier-type reactions.66 Submicromic zinc powder produced by pulsed sono-electroreduction is about three times more effective than the commercial variety. The stereochemical course of the allylation and propargylation of several aldehydes with crotyl and propenyl halides using zinc powder as the... 

A chemoenzymatic methodology has been developed using indium-mediated allylation (and propargylation) of heterocyclic aldehydes under aqueous conditions followed by Pseudomonas cepacia lipase-catalyzed enantioselective acylation of racemic homoallylic and homo-propargylic alcohols in organic media.192... 

Reactions of Allylation and Propargylation Allylation of prochiral and chiral nitrones (292) with allylmagnesium chloride leads to homoallylic hydroxylamines (416), which via an iodo cyclization step are converted to 5-(iodomethyl)isoxazolidines (417) (Scheme 2.186) (202, 213, 666-668). 

Double bonds in conjugation to a carbonyl group and allylic and propargylic alcohols. But the isolated double and triple bonds are inert. 

The isomerisation of allyl and propargylic alcohols involves the 1,3-shift of an oxygen atom rather than a hydrogen atom. Isomerisation of allyl alcohols can be catalysed by a variety of metal oxo complexes and in this instance the reaction does not involve metal carbon bonds as we will see. One could imagine that allylic metal species can participate in isomerisation of allylic compounds, but for the alcohols themselves this is not an easy reaction. In chapter 13 reactions of allyl acetates and the like, which are more prone to... 

Relatively few examples involving a phosphorous atom in the a-heteroatom-alkylcuprate have appeared [176]. Such cuprates have been treated with allylic and propargylic substrates, but have not been reported to undergo conjugate addition... 

Scheme 18 Coupling of an allenylidene ligand with allyl and propargyl alcohol...

This unusual reactivity was subsequently extended to a broad variety of allylic and propargylic amines, in combination with other ruthenium(II) metal fragments, allowing the isolation of aminoaUenylidene complexes 33-35 [47 9] (Fig. 6). In addition, the S3mthesis of the thio-allenylidene [44] and seleno-aUenylidene [50] derivatives 36 from the in situ generated butatrienylidene tra s-[RuCl (=C=C=C=CH2)(L2)2] (L2 = dppm, dppe) and the corresponding aUyl sulfides... 

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