A general set of conditions that achieves the union of aryl halides and divinyl or enyne carbinols to afford tri-or tetrasubstituted olefins in good yields (up to 83%) is described. The mechanism by which this proceeds is believed to involve the intermediacy of a cyclopropanol, followed by a novel skeletal reorganization. The ability to suppress β-hydride elimination of organopalladium intermediates appears to be critical to the success of these processes.The formation of carbon-carbon bonds is of fundamental importance in the synthesis of complex organic molecules. Among the metal-catalyzed methods available for C-C bond construction, the Heck reaction is arguably one of the most useful because it employs relatively stable and easily accessible starting materials. 1 As part of a general synthetic program aimed at the facile construction of seven-membered ring containing compounds (e.g., 3, Scheme 1), we became interested in utilizing a Stille-Ortar variant 2 of the Heck reaction that employed ditriflate 1 and divinyl carbinols (e.g., 2) for this purpose. Surprisingly, a complex mixture, which included enal and bisenal products (4 and 5, respectively), was realized under standard Heck reaction conditions employing PdCl 2 (PPh 3 ) 2 (3 mol %) and Hünig's base (3 equiv) at 80 °C with DMF as solvent.We decided to pursue this transformation further with the aim of developing a wide-ranging and high-yielding method as well as added insight into the mechanism of this novel rearrangement. However, the reaction of 2 with a variety of simple aryl halides and triflates was found not to be general, as these predominantly formed the standard Heck products.Perusal of the literature revealed a single, isolated example of this reaction reported by Gribble as part of a study of the Pd-mediated synthesis of 3-vinyl and 3-alkynyl indoles. 3 In our hands, the reaction of 3-indolyl triflate with 2 under the conditions reported by Gribble proceeded in only 35% isolated yield, prompting further study.
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