Categories: C-B Bond Formation > Synthesis of boronic acids and boronates >
Synthesis of alkylboronic acids and alkylboronates
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A catalyst formed in situ from NiBr2 • diglyme and a pybox ligand
accomplishes Miyaura-type borylations of unactivated tertiary, secondary, and
primary alkyl halides with diboron reagents to furnish alkylboronates. The
method exhibits good functional-group compatibility and is regiospecific.
A. S. Dudnik, G. C. Fu, J. Am. Chem. Soc., 2012,
134, 10693-10697.
orylation of primary and secondary alkyl chlorides, bromides, and iodides
with diboron proceeded in the presence of copper(I)/Xantphos as catalyst and a
stoichiometric amount of K(O-t-Bu) as base. Menthyl halides afforded the
corresponding borylation product with excellent diastereoselectivity, whereas (R)-2-bromo-5-phenylpentane
gave a racemic product.
H. Ito, K. Kubota, Org. Lett., 2012,
14, 890-893.
Aliphatic, aromatic, heteroaromatic, vinyl, or allylic Grignard reagents eact
with pinacolborane at ambient temperature in tetrahydrofuran to afford the
corresponding pinacolboronates. The initially formed dialkoxy alkylborohydride
intermediate quickly eliminates hydridomagnesium bromide and affords the product
boronic ester in very good yield. This reaction also can be carried out under
Barbier conditions.
J. W. Clary, T. J. Rettenmaier, R. Snelling, W. Bryks, J. Banwell, W. T. Wipke,
B. Singaram, J. Org. Chem., 2011,
76, 9602-9610.
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.
Using bis(pinacolato)diboron, catalytic amounts of CuII, and various
amine bases in water under atmospheric conditions at rt, acyclic and cyclic
α,β-unsaturated ketones and esters are β-borylated in good yield. Mechanistic
investigations suggest that the role of the amine is not only to coordinate to
CuII but also to activate a nucleophilic water molecule to form a
reactive sp2-sp3 diboron complex.
S. B. Thorpe, J. A. Calderone, W. L. Santos, Org. Lett., 2012,
14, 1918-1921.
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.
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.
Related
The Suzuki-Miyaura cross-coupling reaction between a diborylmethane derivative
and allyl halides or benzyl halides proceeded efficiently in the presence of an
appropriate Pd-catalyst at room temperature. The present approach provides
functionalized homoallylboronates and alkylboronates with excellent regio- and
chemoselectivities.
K. Endo, T. Ohkubo, T. Ishioka, T. Shibata, J. Org. Chem., 2012,
77, 4826-4831.
K. Endo, T. Ohkubo, T. Ishioka, T. Shibata, J. Org. Chem., 2012,
77, 4826-4831.
