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Synthesis of boronic acids and boronates
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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.
Hydroboration of terminal and internal alkenes with pinacolborane was
carried out at room temperature in the presence of an iridium(I) catalyst.
Addition of dppm to [Ir(cod)Cl]2 gave the best catalyst for
hydroboration of aliphatic terminal and internal alkenes at room
temperature, resulting in addition of the boron atom to the terminal carbon
of 1-alkenes with a selectivity of more than 99%. On the other hand, a
complex prepared from dppe and [Ir(cod)Cl]2 resulted in the best
yields for vinylarenes. These complexes exhibited higher levels of catalyst
activity and selectivity than those of corresponding rhodium complexes.
Y. Yamamoto, R. Fujikawa, T. Umemoto, N. Miyaura, Tetrahedron,
2004,
60, 10695-10700.
Methylpentanediolborane can be prepared easily by reaction of hexyleneglycol
with borane dimethylsulfide or B2H6 generated from NaBH4
and I2. MPBH hydroborates stereo- and regioselectively highly
functionalized alkynes. MPBH compares favorably with pinacolborane in terms of
reactivity. The obtained vinylboronic esters are air- and chromatography-stable.
N. PraveenGanesh, S. d'Hondt, P. Y. Chavant, J. Org. Chem., 2007,
72, 4510-4514.
Preparation of (E)-1-Alkenylboronic Acid Pinacol Esters via Transfer of
Alkenyl Group from Boron to Boron
K. Shirakawa, A. Arase, M. Hoshi, Synthesis,
2004,
1814-1820.
4-Substituted 1,2-oxaborol-2(5H)-ols were prepared through
copper-catalyzed carbomagnesation of propargyl alcohol, followed by the
transmetallation of magnesium to boron in a one-pot procedure. The
Suzuki-Miyaura cross-coupling of these new 2,2-disubstituted alkenylboronic
acids with aryl halides afforded stereodefined 2,3-disubstituted allyl
alcohols in good to excellent yields.
G.-H. Fang, Z.-J. Yan, M.-Z. Deng,
Synthesis, 2006, 1148-1154.
A copper-catalyzed γ-selective and stereospecific substitution reaction of
allylic carbonates with bis(pinacolato)diboron afforded allylboron
compounds. Functionalized allylboronates that have an acetal, ester, or
isolated alkene were prepared. The reaction of optically active allylic
carbonates underwent complete chirality transfer.
H. Ito, C. Kawakami, M. Sawamura, J. Am. Chem. Soc.,
2005,
127, 16034-16035.
A new method for the synthesis of organoborates starting from α,β-unsaturated
acetals was developed. The available alkoxy-functionalized butadienyl- and
styrylboronic esters cross couple effectively with a broad spectrum of aryl
halides under mild conditions. This method provides an effective
approach to aromatic ketones.
P. B. Tivola, A. Deagostino, C. Prandi, P. Venturello, Org. Lett.,
2002,
4, 1275-1277.
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.
An efficient and practical protocol allows the protection of various aryl
and aliphatic amines using (Boc)2O in the presence of a catalytic
amount of iodine under solvent-free conditions at ambient temperature.
R. Varala, S. Nuvula, S. R. Adapa, J. Org. Chem., 2006,
71, 8283-8286.
3-Substituted-2-alkoxycarbonyl allylboronates are readily produced by
the cross-coupling of Baylis-Hillman acetate adducts and
bis(pinacolato)diboron in the presence of palladium catalyst. Subsequent
addition of excess aqueous KHF2 gives stable allyl
trifluoroborate salts.
G. W. Kabalka B. Venkataiah, G. Dong, J. Org. Chem., 2004,
69, 5807-5809.
A new method for the synthesis of substituted 2-acylallylmetal reagents in a
highly regio- and stereoselective fashion involving a three-component
assembly of allenes, acyl chlorides, and bimetallic reagents (B-B, Si-Si,
and Sn-Sn) catalyzed by phosphine-free palladium complexes is described.
F.-Y. Yang, M. Shanmugasundaram, S.-Y. Chuang, P.-J. Ku, M.-Y. Wu, C.-H.
Cheng, J. Am. Chem. Soc.,
2003,
125, 12576-12583.
Palladium-catalyzed coupling reactions of functionalized allylboronic acids
with various iodobenzenes under standard Suzuki-Miyaura coupling conditions
afforded selectively the branched allylic products in high to excellent
yields.
S. Sebelius, V. J. Olsson, O. A. Wallner, K J. Szabó, J. Am. Chem. Soc.,
2006,
128, 8150-8151.
S. Sebelius, V. J. Olsson, O. A. Wallner, K J. Szabó, J. Am. Chem. Soc.,
2006,
128, 8150-8151.
Alkynylboration of alkynes with alkynyl(pinacol)boranes in the presence of
nickel catalysts gave cis-1-borylbut-1-en-3-yne derivatives. Some
boryl-substituted enynes were reacted with sp2 halides under
Suzuki-Miyaura coupling conditions.
M. Suginome, M. Shirakura, A. Yamamoto, J. Am. Chem. Soc., 2006,
128, 14438-14439.
Pd-catalyzed diboration of prochiral allenes occurs exclusively at the
internal position and is accelerated in the presence of Lewis basic ligands.
A chiral ligand was employed, and the enantiomeric excess of a variety of
diboration products was found to be in the range of 86-92% ee.
N. F. Pelz, A. R. Woodward, H. E. Burks, J. D. Sieber, J. P. Morken, J. Am. Chem. Soc.,
2004,
126, 16328-16329.
Related:
The cobalt-catalyzed Diels-Alder reaction of alkynyl pinacol boronic esters with various dienes generates cycloadducts in very good regioselectivity. A reaction sequence (Diels-Alder reaction, Suzuki coupling, DDQ oxidation) was successfully performed as a one pot operation without isolation of the intermediates.
G. Hilt, K. I. Smolko, Angew. Chem., 2003, 115, 2901-2903.
1-Alkenylboronic acid pinacol esters have been synthesized via a palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with 1-alkenyl halides or triflates in toluene at 50°C in the presence of KOPh in high yields with complete retention of configuration of the double bonds. A one-pot synthesis of unsymmetrical 1,3-dienes via the borylation-coupling sequence has been developed.
J. Takagi, K. Takahashi, T. Ishiyama, N. Miyaura, J. Am. Chem. Soc.,
2002,
124, 8001-8006.
Pd-catalyzed enantioselective diborations of prochiral allenes followed by allylation reactions with primary imines provide vinyl boronates which may be oxidized to give nonracemic Mannich products. Alternatively, enantiomerically enriched homoallylic amine derivatives may be obtained by protonation and Suzuki cross-coupling of the vinyl boronate.
J. D. Sieber, J. P. Morken, J. Am. Chem. Soc.,
2006,
128, 74-75.
