title: Gold-catalyzed cycloisomerization of 1,6,8-dienyne carbonates and esters to cis-cyclohepta-4,8-diene-fused pyrrolidines.
abstract: A synthetic approach that provides access to cis-cyclohepta-4,8-diene-fused pyrrolidines efficiently through Au(I) -catalyzed cycloisomerization of 1,6,8-dienyne carbonates and esters at a low catalyst loading of 2 mol % is reported. Starting carbonates and esters with a pendant alkyl group on the terminal alkenyl carbon center were found to favor tandem 1,2-acyloxy migration/cyclopropanation followed by Cope rearrangement of the resulting cis-3-azabicyclo[3.1.0]hexane intermediate. On the other hand, substrates containing a terminal diene or starting materials in which the distal alkene moiety bears a phenyl substituent were observed to undergo competitive but reversible 1,3-acyloxy migration prior to the nitrogen-containing bicyclic ring formation. The delineated reaction mechanism also provides experimental evidence for the reversible interconversion between the oft-proposed organogold intermediates obtained in this step of the tandem process.
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore), Fax: (+65) 67911961.
authors.forename: Weidong
authors.initials: W
authors.lastname: Rao
authors.lastname: Sally
authors.forename: Stuart Neil
authors.initials: SN
authors.lastname: Berry
authors.forename: Philip Wai Hong
authors.initials: PW
authors.lastname: Chan
keywords: alkynes; gold; homogenous catalysis; multicomponent reactions; nitrogen heterocycles