The Journal of Organic Chemistry
Note
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7431.
EXPERIMENTAL SECTION
ESI-HRMS data was obtained with a time-of-flight (TOF) detector in
negative ion mode. All NMR spectra were recorded at room
temperature on a 300 or 400 MHz spectrometer. p-Anisoleboronic
■
−
acid (20 mM) was converted to the ArBF3 using a solution of 1 M
KHF2 in 1 M HCl (buffered HF pH ∼2). For base-mediated
protodeboronation, commercially available boronic acids listed in
Table 1 were obtained from commercially available sources or
prepared according to our previous reports.6,34 For 35, commercially
available 3-phenolboronylpincacolate was brominated in NBS
according to the following method. A flame-dried round-bottom
flask was charged with 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)phenol (330 mg, 1.5 mmol), 3.2 equiv of N-bromosuccinimide (854
mg, 4.8 mmol), and 0.02 equiv of AuCl3 (10 mg, 0.03 mmol) along
with 3 mL of dry 1,2-dichloroethane (DCE). The reaction was heated
up to 80 °C for 12 h before quenching with 20 mL of water. The
aqueous layer was extracted twice with 20 mL of CH2Cl2. The organic
layers were combined and concentrated under vacuum. The crude
residue was chromatographed on using a gradient (0−20%) of ethyl
acetate in hexane to give 410 mg (2.2 equiv) as a white powder. Yield:
(17) Lennox, A. J. J.; Lloyd-Jones, G. C. Angew. Chem., Int. Ed. 2013,
52, 7362.
(18) Weissman, H.; Milstein, D. Chem. Commun. 1999, 1901.
(19) Hoshi, T.; Honma, T.; Mori, A.; Konishi, M.; Sato, T.;
Hagiwara, H.; Suzuki, T. J. Org. Chem. 2013, 78, 11513.
(20) Eseola, A. O.; Geibig, D.; Gorls, H.; Sun, W. H.; Hao, X.;
Woods, J. A. O.; Plass, W. J. Organomet. Chem. 2014, 754, 39.
(21) Batey, R. A.; Quach, T. D. Tetrahedron Lett. 2001, 42, 9099.
(22) Quach, T. D.; Batey, R. A. Org. Lett. 2003, 5, 4397.
(23) Kotha, S.; Lahiri, K.; Kashinath, D. Tetrahedron 2002, 58, 9633.
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Kennedy, L. E. J. Org. Chem. 2009, 74, 7364.
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(26) Molander, G. A.; Canturk, B. Angew. Chem., Int. Ed. 2009, 48,
9240.
(27) Kuivila, H. G.; Reuwer, J. F.; Mangravi, J. A. Can. J. Chem. 1963,
41, 3081.
1
64%. H NMR (300 MHz, CDCl3): 1.47 (s, 12H), 5.91 (s, 1H), 7.64
(s, 1H). 13C NMR: 24.89, 77.02, 85.30, 110.93, 113.48, 116.06, 134.55,
−
148.42. HRMS (ESI-TOF) m/z: [M]− Calcd for C12H14BBr3O3
451.8544; Found 451.8552.
To measure deboronation rates, stock solutions (20 mM) of the
boronic acids in Table 1 were prepared in water. Arylboronate (1
equiv) was reacted with 200 mM KOH for various time points.
Reactions were quenched with 1 equiv of HCl. For fluorinated
arylboronic acids, protodeboronation was monitored using 19F NMR
spectroscopy (300 MHz) using trifluoroethanol (TFE) as an internal
standard at −75 ppm (Figure 1). In most cases, starting material and
product were resolved by HPLC, and time-dependent rates of
deboronation were fitted to pseudo-first-order rate equations. Product
composition was confirmed by mass spectrometry (ESIMS and EI-
MS). For most compounds in question, conversion to a single
protodeboronated product was observed.
(28) Nahabedian, K.; Kuivila, H. G. J. Am. Chem. Soc. 1961, 83, 2167.
(29) Ting, R.; Harwig, C.; Lo, J.; Li, Y.; Adam, M. J.; Ruth, T. J.;
Perrin, D. M. J. Org. Chem. 2008, 73, 4662.
(30) Ting, R.; Lo, J.; Adam, M. J.; Ruth, T. J.; Perrin, D. M. J. Fluor.
Chem. 2008, 129, 349.
ASSOCIATED CONTENT
■
S
* Supporting Information
(31) Li, Y.; Asadi, A.; Perrin, D. M. J. Fluor. Chem. 2009, 130, 377.
(32) Ting, R.; Aguilera, T. A.; Crisp, J. L.; Hall, D. J.; Eckelman, W.
C.; Vera, D. R.; Tsien, R. Y. Bioconjugate Chem. 2010, 21, 1811.
(33) Liu, Z.; Li, Y.; Lozada, J.; Wong, M. Q.; Greene, J.; Lin, K.-S.;
Yapp, D.; Perrin, D. M. Nucl. Med. Biol. 2013, 40, 841.
(34) Liu, Z.; Hundal-Jabal, N.; Wong, M.; Yapp, D.; Lin, K. S.;
Benard, F.; Perrin, D. M. MedChemComm 2014, 5, 171.
(35) Charton, M. J. Am. Chem. Soc. 1969, 91, 615.
(36) Charton, M. J. Am. Chem. Soc. 1969, 91, 6649.
(37) Charton, M. Can. J. Chem. 1960, 38, 2493.
Analysis of screening techniques, UV, HPLC, and 19F NMR
spectra, corresponding mass spectra of products and graphical
extrapolation to rate constants, and characterization of
compound 35. This material is available free of charge via the
AUTHOR INFORMATION
■
Corresponding Author
(38) Noguchi, H.; Shioda, T.; Chou, C. M.; Suginome, M. Org. Lett.
2008, 10, 377.
Notes
(39) Iwadate, N.; Suginome, M. J. Organomet. Chem. 2009, 694,
1713.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by funds from NSERC.
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dx.doi.org/10.1021/jo500734z | J. Org. Chem. 2014, 79, 5365−5368