title: Acceleration of metallacycle-mediated alkyne-alkyne cross-coupling with TMSCl.
abstract: Investigation of titanium-centered metallacycle-mediated cross-coupling between unsymmetrical internal alkynes has led to the discovery that TMSCl significantly accelerates the C-C bond forming event. We report a collection of results that compare the efficiency of this reaction employing Ti(Oi-Pr)4/2n-BuLi in PhMe with and without TMSCl, demonstrating in every case that the presence of TMSCl has a profound impact on efficiency. While relevant in the context of developing this fundamental bond-forming process as an entry to more complex organometallic transformations, these modified reaction conditions allow coupling processes to be run at > 10 times the concentrations previously possible [in 2.4Mn-BuLi (hexanes)], without the requirement of additional solvent. Finally, we demonstrate the effectiveness of these modified reaction conditions for the annulative cross-coupling between TMS-alkynes and 1,6-enynes leading to the formation of angularly substituted hydrindanes with, now well appreciated, high levels of regio- and stereoselection.
authors.affiliation: Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755.
authors.forename: James S
authors.initials: JS
authors.lastname: Cassidy
authors.affiliation: Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755.
authors.forename: Haruki
authors.initials: H
authors.lastname: Mizoguchi
authors.affiliation: Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755.
authors.forename: Glenn C
authors.initials: GC
authors.lastname: Micalizio
keywords: 1,3-Dienes; Directed reactions; Metallacycle-mediated cross-coupling; Titanium isopropoxide