| Abstract
| - The palladium-catalyzed cross-coupling of aryl halides or vinylic halides or triflates and 1-(1-alkynyl)cyclobutanols affords good yields of stereoisomerically pure 2-arylidene- or 2-(2-alkenylidene)cyclopentanones, respectively. The process involves (1) oxidative addition of the organichalide or triflate to Pd(0), (2) regioselective, intermolecular carbopalladation of the carbon−carbontriple bond of the 1-(1-alkynyl)cyclobutanol to produce a vinylic palladium intermediate, (3)regioselective ring expansion to a palladacycle, and (4) reductive elimination of the 2-alkylidenecyclopentanone with simultaneous regeneration of the Pd(0) catalyst. Generally, the best results areobtained by employing 10 mol % of Pd(OAc)2, 20 mol % of PPh3, 2 equiv of the aryl or vinylic iodideor vinylic triflate, 2 equiv of diisopropylethylamine, and n-Bu4NCl in DMF as the solvent.
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