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Pd-Catalyzed Hydroborylation of Alkynes: A Ligand Controlled Regioselectivity Switch for the Synthesis of α- or β-Vinylboronates

Author:
Ojha, Devi Prasan, Prabhu, Kandikere Ramaiah
Source:
Organic letters 2016 v.18 no.3 pp. 432-435
ISSN:
1523-7052
Subject:
alkynes, carbenes, catalysts, catalytic activity, chemical reactions, chemical structure, heterocyclic nitrogen compounds, ligands, palladium, regioselectivity, solvents
Abstract:
A ligand controlled selective hydroborylation of alkynes to α- or β-vinylboronates has been developed using a Pd catalyst. The high α-selectivity displayed by this reaction can be switched to furnish β-vinylboronates by altering the ligand from a trialkylphosphine to N-heterocyclic carbene. A variety of terminal alkynes are shown to furnish the corresponding α- or β-vinylboronates in good to excellent selectivity and yield. The mechanistic studies suggest that the solvent is the proton source and bromobenzene functions as an important additive in driving this reaction forward.
Agid:
5792272