Gold-catalyzed [4C+2C] cycloadditions of allenedienes, including an enantioselective version with new phosphoramidite-based catalysts: Mechanistic aspects of the divergence between [4C+3C] and [4C+2C] pathways

Isaac Alonso, Beatriz Trillo, Fernando López, Sergi Montserrat, Gregori Ujaque, Luis Castedo, Agustí Lledós, Jose L. Mascareñas

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211 Citations (Scopus)

Abstract

Gold(I) complexes featuring electron acceptor ligands such as phosphites and phosphoramidites catalyze the [4C+2C] intramolecular cycloaddition of allenedienes. The reaction is chemo- and stereoselective, and provides trans-fused bicyclic cycloadducts in good yields. Moreover, using novel chiral phosphoramidite-based gold catalysts it is possible to perform the reaction with excellent enantioselectivity. Experimental and theoretical data dismiss a cationic mechanism involving intermediate II and suggest that the formation of the [4C+2C] cycloadducts might arise from a 1,2-alkyl migration (ring contraction) in a cycloheptenyl Au-carbene intermediate (IV), itself arising from a [4C+3C] concerted cycloaddition of the allenediene. Therefore, these [4C+2C] allenediene cycloadditions and the previously reported [4C+3C] counterparts most likely share such cycloaddition step, differing in the final 1,2-migration step. © 2009 American Chemical Society.
Original languageEnglish
Pages (from-to)13020-13030
JournalJournal of the American Chemical Society
Volume131
Issue number36
DOIs
Publication statusPublished - 16 Sep 2009

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