No abstract

Triphenylphosphane (TPP) has been utilized as a novel and efficient catalyst for the Knoevenagel condensation of aldehydes with acidic methylene compounds such as ethyl cyanoacetate and malononitrile to afford substituted olefins. The reaction proceeds smoothly under mild and solvent‐free conditions and the products are obtained in excellent yields with an E‐geometry. This method is applicable for a wide range of aldehydes including aromatic, aliphatic and heterocyclic substrates. Microwave irradiation has been used to achieve enhanced reaction rates and improved yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Biginelli three-component condensation of an aldehyde, β-keto ester, and urea proceeds smoothly on the surface of the silver salt of heteropolyacid (HPA), i.e. Ag 3 PW 12 O 40 , in water to afford the corresponding 3,4-dihydropyrimidinones in high-to-quantitative yields under mild conditions. The heterogeneous solid acid provides ease of separation of the catalyst and isolation of the products. The recovered catalyst can be recycled in subsequent reactions with consistent activity.

By employing ligands in the PdII‐mediated arylative isomerization of allyl alcohols, a milder and regioselective access to the versatile building blocks β‐aryl aldehydes and ketones was developed. This new and chelation‐controlled protocol enabled the compatibility of wide range of functionalities to generate dihydrochalcones, α‐benzyl‐α′‐alkyl acetones, dihydrocinnamaldehydes, and α‐benzyl β‐keto esters (from Baylis–Hillman adducts). A practical multigram synthesis of an intermediate for Propafenone was also demonstrated.

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