Ligated Regioselective PdII Catalysis to Access β-Aryl-Bearing Aldehydes, Ketones, and β-Keto Esters (original) (raw)
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The dual Pd/proline-catalyzed r-allylation reaction of a variety of enolizable ketones and aldehydes with allylic alcohols is described. In this reaction, the choice of a large-bite angle ligand Xantphos and proline as the organocatalyst was essential for generation of the crucial π-allyl Pd intermediate from allylic alcohol, followed by nucleophilic attack of the enamine formed in situ from the corresponding enolizable carbonyl substrate and proline.
Pd-Catalyzed Enantio- and Regioselective Formation of Allylic Aryl Ethers
Organic Letters
A general methodology for the synthesis of enantioenriched tertiary allylic aryl ethers through Pd-catalyzed decarboxylative reactions of vinyl cyclic carbonates and phenols is presented. Switching of the regioselectivity toward the formation of linear products by a judicious choice of the ligand is also reported. Experimental details and spectra for new products (PDF), X-ray data for compound 3e (CIF)
Asian Journal of Organic Chemistry, 2019
Herein, we report an unprecedented, fast, highly efficient,transition-metal-free, modified Favorskii reaction type direct alkynylation as well as (E)-alkenylation protocol towards the synthesis of α,β-unsaturated ketones 5a-u and propargyl alcohols 4a-c, 7a-k and 9a-j via the identification of the combination of Cs2CO3 and Et3N as weak bases in upto 99% yields. In this reaction, aromatic aldehydes afforded α,β-unsaturated ketones and aliphatic aldehydes furnished propargyl alcohols, respectively. The operationally simple protocol, large substrate scope, gramscale synthesis, and practical synthetic applications to bioactive heterocyclic scaffolds 10-13 further highlight the practicality of this methodology. The proposed mechanistic pathway illustrates the involvement of weak base-assisted propargylation of carbonyl compounds followed by allenol-enone tautomerism to furnish (E)alkenylated product.
Palladium-Catalyzed γ-Arylation of α,β-Unsaturated Esters from Silyl Ketene Acetals
Angewandte Chemie International Edition, 2010
The palladium-catalyzed coupling of enolates with aryl and vinyl electrophiles has become a useful method for the construction of carbon-carbon bonds. Although many palladium complexes have been identified that catalyze the coupling of enolates of ketones, esters, amides, and aldehydes with haloarenes, the vinylogous coupling of dienolates of a,bunsaturated carbonyl compounds with haloarenes (g-arylation) has been less studied. g-Aryl a,b-unsaturated carbonyl compounds are useful building blocks because they can be further functionalized at the carbonyl or olefinic positions. To develop a catalyst for the g-arylation of a,b-unsaturated carbonyl compounds, one must address several issues, including the regioselectivity for forming products from a-, b-, or g-arylation, the selectivity for monoarylation versus diarylation, and the potential condensation of the reactive products. The selectivity for formation of products from aor g-arylation versus b-arylation depends on whether an enolate complex forms by transmetalation with the arylpalladium halide intermediate, as occurs during the a-arylation of carbonyl compounds, or whether it forms by insertion of the a,b-unsaturated carbonyl compound into the metal-aryl bond, as occurs during a Heck reaction. The selectivity for products from a-versus g-arylation likely depends on the stability and reactivity of the series of isomeric arylpalladium dienolate intermediates that result from transmetalation.
ChemCatChem, 2017
Selective synthesis is in the core of modern organic chemistry. In this communication, a novel ligand-dependent palladium-catalyzed carbonylation procedure for the divergent synthesis of aldehydes and carboxylic acids from easily available aryl halides has been established. Under the same reaction conditions, the reaction pathways can be controlled by the ligands applied to give formylated and carboxylated products selectively. Sterically hindered monodentate ligand facilitates the reductive carbonylation and provides aldehydes, while bidentate ligand prefers carboxylation reaction and produce carboxylic acids. A wide range of functional groups were tolerated with moderate to excellent yields in general.
Chemistry - A European Journal, 2012
Scheme 3. Scope of Pd II-catalyzed dehydrogenative coupling of 1 with different phenols. Yields of isolated products are reported. Reaction conditions: 1 (0.6 mmol, 1.5 equiv), 2 (0.4 mmol, 1.0 equiv), [PdA C H T U N G T R E N N U N G (tfa) 2 ] (10 mol %), TFA/DCE (4:1, 0.5 mL) under an oxygen-filled balloon at 20-25 8C. [a] 1 (2.34 g, 1.4 equiv), 2 (1.08 g, 1.0 equiv), [PdA C H T U N G T R E N N U N G (tfa) 2 ] (5 mol %), TFA/DCE (4:1, 12.5 mL) under an oxygen-filled balloon at 20 8C. [b] X-ray structure of 3 v is available [CCDC 880392], see the Supporting Information. [17] Scheme 4. Plausible reaction mechanism of dehydrogenative b-arylation of 1 a with 2 a.