Synthese de (e)-arylidene et allylidene cyclopentanes par une annelation catalysee par un complexe de palladium(0)
摘要:
When treated with an unsaturated halide in a palladium-catalyzed process, the anions from gamma-acetylenic malonates 4 and 5 stereospecifically lead to cyclopentanes having an exo tri- or tetra-substituted double bond. This reaction which forms simultaneously two carbon-carbon bonds is believed to proceed by nucleophilic attack of the anion on the triple bond activated by the sigma-aryl or sigma-vinyl palladium complex.
Pd-catalyzed intramolecular addition of active methylene compounds to alkynes, followed by subsequent cross-coupling with (hetero)aryl bromides and chlorides. The reaction proceeds under mild conditions, providing excellent functional group tolerance, including unprotected OH, NH2 groups, enolizable ketones, or a variety of heterocycles. Mechanistic studies point towards a catalyticcycle involving oxidative