Comparative study on the reactivity of propargyl and alkynyl sulfides in palladium-catalyzed domino reactions

International audienceThree types of sulfides bearing a propargyl or an alkynyl moiety have been studied in cyclocarbopalladation/cross-coupling domino palladium-catalyzed sequences. The reactivity of different types of sulfured starting materials has been compared as well as the difference in behavior of these compounds depending on the type of cross coupling ending the domino sequence. It appeared that these cascades were constantly more efficient on the propargyl benzyl thioether. In addition, it has been demonstrated that domino sequences ending with Stille, SuzukieMiyaura, or MizorokieHeck lead efficiently and selectively to the desired cyclized products. Notably, when the introduction of an alkyne is targeted at the end of the cascade, it appeared that the Sonogashira coupling leads every time to the desired cyclic product in the mixture with the product resulting from the direct coupling between the aryl moiety of the substrate and the alkyne used as partner. Finishing the domino sequence with a Stille coupling instead of a Sonogashira one allowed improving significantly the ratio of the mixture in favor of the desired cyclized compound

Microwaves make hydroformylation a rapid and easy process

Hydroformylation of alkenes can be carried out in a few minutes under microwave activation at a relatively low pressure (40 psi) using commercially available catalysts and ligands. The 80 mL vial of a Discover microwave oven was connected to a cylinder of CO and H2, and after filling the reactor at 40 psi, a mixture of an alkene, the Wilkinson catalyst, and XANTPHOS was submitted to microwave irradiation giving, after 4 min, high conversion into the corresponding aldehyde without formation of the isomerized alkene. © 2006 American Chemical Society

Molecular Diversity of Cyclooctatetraenes through Palladium-Catalyzed Cascade Reactions

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