γ-Selective Cross-Coupling of Allylic Silanolate Salts with Aromatic Bromides Using Trialkylphosphonium Tetrafluoroborate Salts Prepared Directly from Phosphine•Borane Adducts
Scott E. Denmark* and Nathan S. Werner
*Roger Adams Laboratory, Department of Chemistry, University of Illinois, 600 South Mathews Avenue, Urbana, Illinois 61801, United States, Email: sdenmarkillinois.edu
S. E. Denmark, N. S. Werner, Org. Lett., 2011, 13, 4596-4599.
DOI: 10.1021/ol2017998 (free Supporting Information)
A γ-selective, palladium-catalyzed cross-coupling of sodium (Z)-2-butenyldiethylsilanolate provides high yields and site selectivity with electron-rich, electron-poor, sterically hindered, and heteroaromatic bromides. The use of a configurationally homogeneous (Z)-silanolate, nontransferable ethyl groups, and a sterically bulky trialkylphosphonium tetrafluoroborate salt are critical to the success of the method.
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