Kinetic Study of Carbophilic Lewis Acid Catalyzed Oxyboration and the Noninnocent Role of Sodium Chloride
作者:Joel S. Johnson、Eugene Chong、Kim N. Tu、Suzanne A. Blum
DOI:10.1021/acs.organomet.5b00939
日期:2016.3.14
In the present study, the oxyboration reaction catalyzed by IPtAuTFA in the presence and absence of NaTFA has been examined with kinetic studies, mass spectrometry, and H-1 NMR. and 11B NMR spectroscopy. Data from monitoring the reactions over the temperature range from 30 to 70 degrees C, the catalyst range from 1.3 to 7.5 mol %, and the NaTFA additive range from 2.5 to 30 niol % suggests a mechanism that involves rate-determining catalyst generation. Data from additive studies that replaced NaTFA with NaBARF (BARF = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) or Bu(4)NTFA as an alternative additive suggest that catalyst quenching from residual NaCl remaining from a one-pot substrate synthesis/reaction method is the cause of this effect, despite the low solubility of this NaCl byproduct in toluene. Material produced through an alternative, sodium chloride-free substrate synthesis exhibited faster reaction rates, consistent with a change in rate-determining step that depended on the substrate synthesis route.