Arylations of electron-rich heteroatom-substituted olefins were performed with arylboronic acids. This appears to constitute the first example of palladium(II)-catalyzed internal Heck arylations. The novel protocol exploits oxygen gas for environmentally benign reoxidation and a stable 1,10-phenanthroline bidentate ligand to promote the palladium(II) regeneration and to control the regioselectivity. Internal arylation is strongly favored with electron-rich arylboronic acids. DFT calculations support a charge-driven selectivity rationale, where phenyls substituted with electron-donating groups prefer the electron-poor alpha-carbon of the olefin. Experiments, verified by calculations, confirm the cationic nature of the catalytic route. This Heck methodology provides a facile and mild access to functionalized enamides. Controlled microwave heating and increased oxygen pressure were used to further reduce the reaction time to 1 h.

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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.

The useful and selective reactivity of arylboronic acids makes them favourite building blocks for many modern organic chemistry applications like the metal-mediated formation of C-C, C-O, C-N, and C-S bonds. This report describes oxidative Heck coupling reactions of arylboronic acids and olefins, which were conveniently and rapidly (5-30 min) carried out under air with temperature-controlled microwave heating. Different reaction conditions were investigated with regard to both microwave heating capability and chemical productivity. Copper(II) acetate was identified as a microwave compatible reoxidant of Pd(0). The scope and limitations of this high-speed chemistry protocol with diverse olefins and organoboronic acids are discussed.

Carboxylic acid estersCarboxylic acid esters Q 0530 The First Ligand-Modulated Oxidative Heck Vinylation. Efficient Catalysis with Molecular Oxygen as Palladium(0) Oxidant. -(ANDAPPAN, M. M. S.; NILSSON, P.; LARHED*, M.; Chem. Commun. (Cambridge) 2004, 2, 218-219; Dep. Org. Pharm. Chem., Biomed. Cent., Uppsala Univ., S-751 23 Uppsala, Swed.; Eng.) -M. Paetzel