A-Allyl ketones

Propargylic alcohol, after lithiation, reacts with CO to generate the lithium carbonate 243, which undergoes oxypalladation. The reaction of allyl chloride yields the cyclic carbonate 244 and PdCl2. By this reaction hydroxy and allyl groups are introduced into the triple bond to give the a-allyl ketone 245[129]. Also the formation of 248 from the keto alkyne 246 with C02 via in situ formation of the carbonate 247 is catalyzed by Pd(0)[130],... 

A Pd(0)-catalyzed Claisen rearrangement with a subsequent intramolecular Heck vinylation has been demonstrated by Watson and coworkers [84], Upon treatment with Pd(PPh3)4 the allyl vinyl ether undergoes a Pd(0)-catalyzed 1,3 oxygen to carbon allyl shift to afford an a-allyl ketone that... 

The formation of a-allylated ketones through allylation of selenium-stabilized enolates, generated by deprotonation of a-selanylated ketones, can be explained by three general postulated mechanisms depending on the nature of the RSe substituent and the allyl halide used [37] (Scheme 29). The first ex-... 

Displacement of a cyano group in a-cyanoketones is possible. Treatment of the a-cyanoketone with Sml2 followed by addition of an excess of allyl bromide gave the a-allyl ketone derivative. a-Cyano amines react with allyl bromide and then zinc metal to give homoallylic amines after treatment with dilute acetic acid in... 

Trabanco and coworkers developed an operationally simple method for the a-allylation of aryl alkanones with ally] alcohol under microwave irradiation conditions (Scheme 10.35) [77]. The corresponding a-allyl ketones were obtained in moderate to good yields with minor quantities of diallylation by-products. 

In 2009, Breit et al. [109d] have extended the enamine strategy to unactivated allyl alcohols as substrates for the allyhc substitution (Scheme 12.47). When (d/l)-proline is used as the amine component, the carboxylic acid moiety in situ activates the allylic alcohol for abstraction of water and formation of a tt-allylpalladium complex. Subsequent nucleophilic attack of the enamine leads to the a-allylated ketones or aldehydes. Interestingly, the use of enantiopure prohne has no effect on the stereochemical outcome of the reaction with prochiral substrates. 

Intermolecular capture of cationic intermediates resulting from Nazarov cyclizations has been demonstrated with added nucleophiles. For example, allyl silanes can be used to either generate a-allyl ketones or [3 + 2] cyclization products. ... 

Yet another alternative that is complementary with that mentioned above involves the base-promoted reaction of ketones with allyl chloroformates to form the corresponding allyl enol carbonates followed by their Pd-catalyzed decomposition to give a-allylated ketones (Scheme 4). 

In extensions of some earlier studies, Wada et al. have shown that a useful method of cyclopentane annelation is by rearrangement of protonated cyclopropyl ketones, to y-hydroxy-ketones, viz. (51), followed by oxidation to 1,4-diones and base-catalysed cyclization (Scheme 16). Both oxidation of a-allyl-ketones, using PdCl2-CuCl in DMF under an oxygen atmosphere, and the oxidative cleavage of t-cyclobutanols using Jones reagent provide alternative new approaches to... 

Nicolaou et al. used the same sulfonate ester system to prove the compatibility of sulfonate esters with carbon-carbon bond-forming reactions [305]. Functionalization and a simultaneous cleavage procedure have been applied successfully by the use of Grignard reagents 585, the Nagata reagent 583 and stannane as well as lithium organic compounds (579, 581). All compounds namely a-allyl ketone 580, epoxide 582, a-cyano ketone 584 and carbinol 586 could be isolated in 65-85% yield (Scheme 85). 

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