Categories: C-B Bond Formation > Synthesis of boronic acids and boronates >
Synthesis of alkylboronic acids and alkylboronates
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Hydroboration of terminal and internal aliphatic alkenes with
pinacolborane was carried out at room temperature in the presence of dppm and [Ir(cod)Cl]2 resulting in addition of the boron atom to the terminal carbon with a selectivity of more than
99%. A complex
prepared from dppe and [Ir(cod)Cl]2 resulted in the best yields for
vinylarenes.
Y. Yamamoto, R. Fujikawa, T. Umemoto, N. Miyaura, Tetrahedron,
2004,
60, 10695-10700.
Efficient and site selective boron-copper addition processes involving acyclic
and cyclic disubstituted aryl olefins are promoted with a readily available N-heterocyclic
carbene (NHC) complex. In situ protonation of the C-Cu bond in the presence of
MeOH leads to efficient catalyst turnover, constituting a net Cu-catalyzed
hydroboration process.
Y. Lee, A. H. Hoveyda, J. Am. Chem. Soc., 2008,
131, 3160-3161.
A simple protocol for the borylation of alkenes with use of impregnated copper
on magnetite showed a very broad scope. All type of olefins could be used with
similar results. The catalyst can be magnetically removed and reused several
times, showing similar activity.
R. Cano, D. J. Ramón, M. Yus, J. Org. Chem., 2010,
75, 3458-3460.
(E)- and (Z)-silyl and aryl-subsituted homoallylic
methanesulfonates were converted to the corresponding cis- and trans-1-silyl-2-borylcyclobutanes
as well as 1-phenyl-2-borylcyclobutanes in the presence of a CuCl/dppp catalyst,
bis(pinacolato)diboron, and K(O-t-Bu)in THF. Stereospecific
derivatizations of the cis- and trans-borylcyclobutanes were
carried out to demonstrate the utility of the borylcyclobutanes.
H. Ito, T. Toyoda, M. Sawamura, J. Am. Chem. Soc., 2010,
132, 5990-5992.
R. Cano, D. J. Ramón, M. Yus, J. Org. Chem., 2010,
75, 3458-3460.
A copper(I)-chiral secondary diamine complex catalyzes an enantioselective
conjugate boration of β,β-disubstituted enones in high yields and up to 99% ee.
The resulting chiral tertiary organoboronates can be converted to
enantiomerically enriched β-hydroxy ketones without any racemization.
I-H. Chen, M. Kanai, M. Shibasaki, Org. Lett., 2010,
12, 4098-4101.
A catalytic enantioselective conjugate boration of β-substituted cyclic enones
in the presence of a QuinoxP*-CuOtBu complex produced enantiomerically
enriched tertiary organoboronates. The substrate scope was broad, and high
enantioselectivity was produced using both β-aromatic and aliphatic (linear and
branched)-substituted cyclic enones with five- to seven-membered ring sizes.
I-H. Chen, L. Yin, W. Itano, M. Kanai, M. Shibasaki, J. Am. Chem. Soc., 2009,
131, 11284-11285.
Rhodium-catalyzed asymmetric hydroboration of 3,3-disubstituted cyclopropenes
gave 2,2-disubstituted cyclopropyl boronates with high degrees of diastereo- and
enantioselectivity. Suzuki cross-coupling reaction of selected
cyclopropylboronic derivatives produced corresponding optically active aryl- and
vinylcyclopropanes in good yields.
M. Rubina, M. Rubin, V. Gevorgyan, J. Am. Chem. Soc., 2003,
125, 7198-7199.
A dramatic rate acceleration in the copper-catalyzed addition of bis(pinacolato)diboron
to α,β-unsaturated carbonyl
compounds was realized by adding alcohol additives. Various α,β-unsaturated carbonyl compounds
were reacted to the corresponding β-boryl carbonyl compounds in high
yields.
R. Varala, S. Nuvula, S. R. Adapa, J. Org. Chem., 2006,
71, 8283-8286.
A nickel catalyst system enables the β-boration of di-, tri-, and
tetrasubstituted α,β-unsaturated esters and amides with bis(pinacolato)diboron
in good yields.
K. Hirano, H. Yorimitsu, K. Oshima, Org. Lett., 2007,
9, 5031-5033.
Aryl cyclopropyl ketones undergo nickel-catalyzed borylative ring opening with
bis(pinacolato)diboron to yield 4-oxoalkylboronates in good yield.
Y. Sumida, H. Yorimitsu, K. Oshima, J. Org. Chem., 2009,
74, 3196-3198.
Diboration of ketones with (ICy)CuOt-Bu as catalyst provides access to
various tertiary α-hydroxyboronate esters. The catalyst was generated in situ
with (ICy)CuCl and NaOt-Bu to afford a more efficient catalyst than the
preformed (ICy)CuOt-Bu. Treatment of the resulting products with silica
gel affords the corresponding α-hydroxyboronate esters.
M. L. McIntosh, C. M. Moore, T. B. Clark, Org. Lett., 2010,
12, 1996-1999.
