† Graduate
School of Pharmaceutical Sciences, The University
of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
School of Pharmaceutical Sciences, The University
of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
‡ Kanai
Life Science Catalysis Project, ERATO, Japan
Science Technology Agency, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Life Science Catalysis Project, ERATO, Japan
Science Technology Agency, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
J. Am. Chem. Soc., 2016, 138 (24), pp 7528–7531
DOI: 10.1021/jacs.6b04646
Publication Date (Web): June 07, 2016
Copyright © 2016 American Chemical Society
Abstract
We
report the first copper-catalyzed regio- and stereoselective
borylalkylation of dialkylsubstituted internal alkynes with
bis(pinacolato)diboron and alkyl halides. A catalytically generated
borylcopper species containing a novel π-accepting N-heterocyclic
carbene ligand chemoselectively reacted with unactivated internal
alkynes over alkyl halides. The intermediate alkenylcopper species
subsequently reacted with alkyl halides, affording the desired products.
The copper catalyst differentiated steric demands between the two
aliphatic substituents on the C≡C triple bond of the alkyne substrates
to exhibit high regioselectivity from a wide range of alkyne/alkyl
halide combinations. This method is useful for the straightforward
synthesis of trialkylsubstituted alkenylboronates, i.e., versatile
precursors for tetrasubstituted alkenes containing three or four
different alkylsubstituents, which are difficult to synthesize by other
methods.
report the first copper-catalyzed regio- and stereoselective
borylalkylation of dialkylsubstituted internal alkynes with
bis(pinacolato)diboron and alkyl halides. A catalytically generated
borylcopper species containing a novel π-accepting N-heterocyclic
carbene ligand chemoselectively reacted with unactivated internal
alkynes over alkyl halides. The intermediate alkenylcopper species
subsequently reacted with alkyl halides, affording the desired products.
The copper catalyst differentiated steric demands between the two
aliphatic substituents on the C≡C triple bond of the alkyne substrates
to exhibit high regioselectivity from a wide range of alkyne/alkyl
halide combinations. This method is useful for the straightforward
synthesis of trialkylsubstituted alkenylboronates, i.e., versatile
precursors for tetrasubstituted alkenes containing three or four
different alkylsubstituents, which are difficult to synthesize by other
methods.
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