Categories: C-B Bond Formation > Synthesis of boronic acids and boronates >
Synthesis of arylboronic acids and arylboronates
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The presence of bis[2-(N,N-dimethylamino)ethyl] ether allows a
selective halide-magnesium exchange of iodo- and bromoaromatics bearing
sensitive carboxylic ester and cyano groups with isopropylmagnesium
chloride. A subsequent reaction with trimethylborate as electrophile
afforded arylboronic acids in good to excellent yields.
X.-J. Wang, X. Sun, L. Zhang, Y. Xu, D. Krishnamurthy, C. H. Senanayake,
Org. Lett.,
2006,
8, 305-307.
The combination of Pd(dba)2 and bis(2-di-tert-butylphosphinophenyl)ether
is an efficient catalyst system for the crosscoupling of pinacolborane with
aryl bromides. This system enables the synthesis of ortho-, meta-,
and para-substituted electron-rich and -deficient arylboronates. A
temperature of 120°C was required for the conversion of electron-rich aryl
chlorides.
M. Murata, T. Sambommatsu, S. Watanabe, Y. Masuda, Synlett, 2006,
1867-1870.
The CuI-catalyzed coupling reaction of pinacolborane with aryl iodides under
the action of sodium hydride in THF at room temperature provided the
corresponding arylboronates in good yields. Aryl bromides gave poor
conversion.
W. Zhu, D. Ma, Org. Lett.,
2006,
8, 261-263.
Arylboronic acids and aryl trifluoroborates are synthesized in a one-pot
sequence by Ir-catalyzed borylation of arenes. To prepare the arylboronic acids,
the Ir-catalyzed borylation is followed by oxidative cleavage of the pinacol
boronates with NaIO4. To prepare the aryltrifluoroborate, the
Ir-catalyzed borylation is followed by displacement of pinacol by KHF2.
J. M. Murphy, C. C. Tzschucke, J. F. Hartwig, Org. Lett., 2007,
9, 757-760.
The palladium catalysed cross-coupling reaction of aryl iodides and bromides
with pinacolborane in 1,3-dialkylimidazolium tetrafluoroborates and
hexafluorophosphates offers simple product isolation by extraction
and shorter reaction time as compared to conventional solvents.
A. Wolan, M. Zaidlewicz, Org. Biomol. Chem., 2003, 1,
3724-3276.
meta- and para-dibromoarenes can be converted to
isopropoxide-protected bromo arylboronates. A subsequent metal-halogen exchange
and reaction with an electrophile leads to functionalized arylboronates in a
one-pot manner.
Q. Jiang, M. Ryan, P. Zhichkin, J. Org. Chem.,
2007,
72, 6618-6620.
