Stereodivergent Access to Trisubstituted Alkenylboronate Esters through Alkene Isomerization
作者:Lucas Segura、Itai Massad、Masamichi Ogasawara、Ilan Marek
DOI:10.1021/acs.orglett.1c03513
日期:2021.12.3
We report an efficient method for the preparation of synthetically valuable trisubstituted alkenylboronate esters through alkene isomerization of their readily available 1,1-disubstituted regioisomeric counterparts. Either stereoisomer of the target alkenylboronate motif can be obtained at will from the same starting material by employing different isomerization catalysts.
Reaction Pathways and Redox States in α‐Selective Cobalt‐Catalyzed Hydroborations of Alkynes
作者:Clemens K. Blasius、Vladislav Vasilenko、Regina Matveeva、Hubert Wadepohl、Lutz H. Gade
DOI:10.1002/anie.202009625
日期:2020.12.14
Cobalt(II) alkyl complexes supported by a monoanionic NNN pincer ligand are pre‐catalysts for the regioselective hydroboration of terminal alkynes, yielding the Markovnikov products with α:β‐(E) ratios of up to 97:3. A cobalt(II) hydride and a cobalt(II) vinyl complex appear to determine the main reaction pathway. In a background reaction the highly reactive hydrido species specifically converts to
NHC–Cu-Catalyzed Protoboration of Monosubstituted Allenes. Ligand-Controlled Site Selectivity, Application to Synthesis and Mechanism
作者:Fanke Meng、Byunghyuck Jung、Fredrik Haeffner、Amir H. Hoveyda
DOI:10.1021/ol4004178
日期:2013.3.15
Two types of NHC-Cu complexes catalyze protoborations of terminal allenes to afford valuable 1,1- or trisubstituted vinylboron species with high site selectivity and stereoselectivity. The scope of the method, application to natural product synthesis, and mechanistic basis for the observed selectivity trends are presented.