The Journal of Organic Chemistry
Article
144.2 (CqAr), 133.8 (CHAr), 129.5 (CHAr), 129.24 (CHAr), 129.20
(CHAr), 128.9 (CHAr), 127.56 (CHAr), 126.9 (CHAr).
NMR (400.0 MHz; Acetone-d6 + D2O) δH: 7.63 (d, J = 7.2 Hz, 1HAr),
7.26 (dd, J = 7.2, 1.2 Hz, 1HAr), 7.18−7.11 (m, 3HAr), 6.85 (m, 1HAr),
6.79 (d, 1H, J = 2.8 Hz, 1HAr), 4.44 (s, 2H), 3.68 (br s, OH). 13C
NMR (100.6 MHz; Acetone-d6 + D2O) δC: 146.4 (CqAr), 135.2
(CHAr), 130.3 (CHAr), 128.0 (CHAr), 127.3 (CHAr), 126.1 (CHAr),
125.6 (CHAr), 124.3 (CHAr), 35.8 (CH2). 11B NMR (160.4 MHz;
Acetone-d6 + D2O) δB: 29.7 (br s). νmax (neat, cm−1): 3206 (br), 1737,
1596, 1567, 1483, 1444, 1339, 1307, 1288, 1256, 1194, 1063, 1034,
831. HRMS (ESI-TOF) m/z: [M − H]− calcd for C11H10BO2S
217.0500; found, 217.0489.
(2-(Thiophen-2-yl)phenyl)boronic Acid (7b). Following general
procedure C, the title compound was prepared using aryl bromide 9b
(100 mg, 0.42 mmol) in 9.8 mL of dry THF, n-BuLi (0.28 mL, 0.46
mmol, 2.2 M in hexane), and B(OMe)3 (0.45 mL, 3.99 mmol).
Recrystallization from pentane yielded desired pure product 7b as a
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colorless solid (67 mg, 0.33 mmol, 79%). Mp 75−77 °C. H NMR
(400.0 MHz; Acetone-d6 + D2O) δH: 7.51 (d, J = 6.8 Hz, 1HAr), 7.41−
7.39 (m, 2HAr), 7.37−7.33 (m, 1HAr), 7.29−7.325 (m, 1HAr), 7.19 (d,
J = 3.2 Hz, 1HAr), 7.05 (dd, J = 4.8, 3.6 Hz, 1HAr), 3.46 (br s, OH).
13C NMR (100.6 MHz; Acetone-d6 + D2O) δC: 146.5 (CqAr), 138.0
(CqAr), 133.6 (CHAr), 129.5 (CHAr), 129.2 (CHAr), 128.4 (CHAr),
127.5 (CHAr), 126.2 (CHAr), 126.1 (CHAr). 11B NMR (160.4 MHz;
Acetone-d6 + D2O) δB: 30.1 (br s). νmax (neat, cm−1): 3303 (br), 1713,
1592, 1481, 1423, 1331, 1277, 1162, 1121, 1009, 831, 804. HRMS
(ESI-TOF) m/z: [M − H]− calcd for C10H8BO2S, 203.0344; found,
203.0330.
(2-(Thiophen-3-ylmethyl)phenyl)boronic Acid (7g). Following
general procedure C, the title compound was prepared using aryl
bromide 9g (280 mg, 1.11 mmol) in 11.8 mL of dry THF, n-BuLi
(0.51 mL, 1.22 mmol, 2.4 M in hexane), and B(OMe)3 (1.18 mL,
10.55 mmol). Recrystallization from pentane yielded desired pure
product 7g as a colorless solid (198 mg, 0.91 mmol, 82%). Mp 95−96
°C. 1H NMR (400.0 MHz; Acetone-d6 + D2O) δH: 7.60 (d, J = 6.8 Hz,
1HAr), 7.28 (dd, J = 4.8, 3.2 Hz, 1HAr), 7.23 (d, J = 7.2 Hz, 1HAr),
7.15−7.10 (m, 2HAr), 7.00 (s, 1HAr), 6.94 (d, J = 4.8 Hz, 1HAr), 4.24
(s, 2H), 3.45 (br s, OH). 13C NMR (100.6 MHz; Acetone-d6 + D2O)
δC: 146.3 (CqAr), 143.9 (CHAr), 134.9 (CHAr), 130.1 (CHAr), 130.0
(CHAr), 129.5 (CHAr), 125.9 (CHAr), 125.8 (CHAr), 121.4 (CHAr),
36.5 (CH2). 11B NMR (160.4 MHz; Acetone-d6 + D2O) δB: 30.0 (br
s). νmax (neat, cm−1): 3214 (br), 1739, 1598, 1564, 1481, 1444, 1431,
1333, 1193, 1160, 1103, 1072, 1044, 995, 781, 749. HRMS (ESI-TOF)
m/z: [M − H]− calcd for C11H10BO2S, 217.0500; found, 217.0493.
(2-(Furan-2-ylmethyl)phenyl)boronic Acid (7h). To a solution of
furan (0.91 mL, 12.48 mmol) in 25 mL of anhydrous Et2O at 0 °C was
added n-BuLi (5.27 mL, 115.59 mmol, 2.2 M in hexane). The solution
was heated under reflux for 4 h. The reaction mixture was then cooled
to 0 °C, and a solution of 2-bromobenzyl bromide (2.75 g, 11 mmol)
in anhydrous ether (7.5 mL) was added dropwise. The solution was
further heated under reflux for 16 h. After cooling, the mixture was
poured onto crushed ice. The ether layer was separated, washed with
brine, and dried to give a brown orange oil (1.56 g) constituted of an
inseparable combination of 9h and 2-bromobenzyl bromide (ratio 2:1)
used without further purification in the next step.23 The presence of 9h
was confirmed by 1H NMR [δH 4.10 (s, 2H)]. To crude 9h (200 mg)
in 19.5 mL of dry THF were added n-BuLi (1 mL, 1.87 mmol, 1.9 M
in hexane) and B(OMe)3 (1 mL, 8.08 mmol) according to general
procedure C. Recrystallization from pentane yielded desired pure
product 7h as an off-white solid (85 mg, 0.42 mmol, 75%). Caution:
(2-((Methylthio)methyl)phenyl)boronic Acid (7c). Following gen-
eral procedure C, the title compound was prepared using aryl bromide
9c (282 mg, 1.3 mmol) in 30 mL of dry THF, n-BuLi (0.65 mL, 1.43
mmol, 2.2 M in hexane), and B(OMe)3 (1.4 mL, 12.35 mmol). The
crude mixture was purified by flash chromatography on silica gel and
eluted with cyclohexane then cyclohexane/EtOAc (80:20) to yield
desired product 7c as a colorless solid (125 mg, 0.69 mmol, 53%).
TLC Rf = 0.2 (cyclohexane/EtOAc: 80/20). Mp 80−82 °C. 1H NMR
(400.0 MHz; Acetone-d6 + D2O) δH: 7.62 (d, J = 7.2, 1HAr), 7.29−
7.21 (m, 2HAr), 7.17−7.15 (m, 1HAr), 3.95 (s, 2H), 3.43 (br s, OH),
1.91 (s, 3H). 13C NMR (100.6 MHz; Acetone-d6 + D2O) δC: 144.1
(CqAr), 135.3 (CHAr), 130.2 (CHAr), 129.8 (CHAr), 126.7 (CqAr), 38.3
(CH2), 14.7 (CH3). 11B NMR (160.4 MHz; Acetone-d6 + D2O) δB:
29.3 (br s). νmax (neat, cm−1): 3283 (br), 1738, 1596, 1485, 1438,
1422, 1302, 1176, 1126, 1086, 1013, 983, 806. HRMS (ESI-TOF) m/
z: [M − H]− calcd for C8H10BO2S, 181.0501; found, 181.0497.
(2-((Ethylthio)methyl)phenyl)boronic Acid (7d). Following general
procedure C, the title compound was prepared using aryl bromide 9d
(600 mg, 2.6 mmol) in 60 mL of dry THF, n-BuLi (1.3 mL, 2.86
mmol, 2.2 M in hexane), and B(OMe)3 (2.8 mL, 24.7 mmol).
Recrystallization from pentane yielded desired pure product 7d as a
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colorless solid (310 mg, 1.58 mmol, 61%). Mp 58−60 °C. H NMR
(400.0 MHz; Acetone-d6 + D2O) δH: 7.61 (d, J = 7.7 Hz, 1HAr), 7.48−
7.23 (m, 2HAr), 7.18−7.16 (m, 1HAr), 3.99 (s, 2H), 3.45 (br s, OH),
2.39 (q, J = 7.6 Hz, 2H), 1.15 (t, J = 5.6 Hz, 3H). 13C NMR (100.6
MHz; Acetone-d6 + D2O) δC: 144.2 (CqAr), 135.2 (CHAr), 130.1
(CHAr), 129.8 (CHAr), 126.6 (CHAr), 36.1 (CH2), 25.6 (CH2), 14.8
(CH3). 11B NMR (160.4 MHz; Acetone-d6 + D2O) δB: 29.4 (br s).
νmax (neat, cm−1): 3284 (br), 1739, 1596, 1485, 1439, 1422, 1350,
1229, 1217, 1116, 1084, 807. HRMS (ESI-TOF) m/z: [M − H]− calcd
for C9H12BO2S, 195.0657; found, 195.0659.
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this is a hygroscopic and air sensitive product. Mp 77−78 °C. H
NMR (400.0 MHz; Acetone-d6 + D2O) δH: 7.60 (d, J = 8.0 Hz, 1HAr),
7.33 (d, J = 4.0 Hz, 1HAr), 7.26−7.22 (m, 2HAr), 7.12 (td, J = 8.0, 4
Hz, 1HAr), 6.24 (d, J = 4.0 Hz, 1HAr), 5.94 (d, J = 4.0 Hz, 1HAr), 4.23
(s, 2H), 3.45 (br s, OH). 13C NMR (100.6 MHz; Acetone-d6 + D2O)
δC: 156.6 (CqAr), 143.6 (CqAr), 141.8 (CHAr), 134.9 (CHAr), 130.0
(CHAr), 129.8 (CHAr), 126.1 (CHAr), 110.8 (CHAr), 106.5 (CHAr),
34.3 (CH2). 11B NMR (160.4 MHz; Acetone-d6 + D2O) δB: 29.3 (br
s). νmax (neat, cm−1): 3285 (br), 1599, 1568, 1506, 1487, 1441, 1342,
1264, 1148, 1124, 1086, 1071, 1008, 935, 895, 883, 797. HRMS (ESI-
TOF) m/z: [M − H]− calcd for C11H10BO3, 201.0728; found,
201.0712.
(2-((Isopropylthio)methyl)phenyl)boronic Acid (7e). Following
general procedure C, the title compound was prepared using aryl
bromide 9e (400 mg, 1.63 mmol) in 38 mL of dry THF, n-BuLi (0.82
mL, 1.79 mmol, 2.2 M in hexane), and B(OMe)3 (1.74 mL, 15.48
mmol). Recrystallization from pentane yielded desired pure product
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7e as a colorless solid (280 mg, 1.33 mmol, 82%). Mp 56−57 °C. H
NMR (400.0 MHz; Acetone-d6 + D2O) δH: 7.61 (d, J = 7.7 Hz, 1HAr),
7.28−7.27 (m, 2HAr), 7.19−7.15 (m, 1HAr), 4.03 (s, 2H), 3.49 (br s,
OH), 2.90 (sept, J = 6.8 Hz, 1H), 1.20 (t, J = 5.6 Hz, 3H). 13C NMR
(100.6 MHz; Acetone-d6 + D2O) δC: 144.1 (CqAr), 135.2 (CHAr),
130.0 (CHAr), 129.8 (CHAr), 126.6 (CHAr), 35.5 (CH2), 35.1 (CH),
23.5 (CH3). 11B NMR (160.4 MHz; Acetone-d6 + D2O) δB: 29.9 (br
s). νmax (neat, cm−1): 3302 (br), 1738, 1597, 1484, 1439, 1350, 1299,
1171, 1156, 1107, 1078, 1008, 785. HRMS (ESI-TOF) m/z: [M −
H]− calcd for C10H14BO2S, 209.0813; found, 209.0811.
(2-Benzylphenyl)boronic Acid (7i). Following general procedure C,
the title compound was prepared using aryl bromide 9i (565 mg, 2.28
mmol) in 53 mL of dry THF, n-BuLi (2.5 M in hexane, 1 mL, 2.5
mmol), and B(OMe)3 (2.41 mL, 21.7 mmol, 9.5 equiv).
Recrystallization from pentane yielded desired pure product 7i as a
colorless solid (380 mg, 1.79 mmol, 79%). Mp 122−123 °C. 1H NMR
(400.0 MHz; Acetone-d6 + D2O) δH: 7.61 (d, J = 8.0 Hz, 1HAr), 7.26−
7.19 (m, 5HAr), 7.19−7.11 (m, 3HAr), 4.27 (s, 2H), 3.22 (s, OH). 13
C
NMR (100.6 MHz; Acetone-d6 + D2O) δC: 146.5 (CqAr), 143.4
(CqAr), 134.9 (CqAr), 130.2 (CHAr), 130.1 (CHAr), 129.7 (CHAr),
128.9 (CHAr), 126.3 (CHAr), 125.8 (CHAr), 41.6 (CH2). 11B NMR
(160.4 MHz; Acetone-d6 + D2O) δB: 29.7 (br s). νmax (neat, cm−1):
3304 (br), 1738, 1596, 1566, 1494, 1483, 1443, 1345, 1292, 1182,
1165, 1115, 1073, 1055, 1043, 747, 696. HRMS (ESI-TOF) m/z: [M
− H]− calcd for C13H12BO2, 211.0936; found, 211.0929.
(2-(Thiophen-2-ylmethyl)phenyl)boronic Acid (7f). Following
general procedure C, the title compound was prepared using aryl
bromide 9f (1.472 g, 5.81 mmol) in 133.6 mL of dry THF, n-BuLi
(2.56 mL, 6.39 mmol, 2.5 M in hexane), and B(OMe)3 (6.22 mL, 55.2
mmol). Recrystallization from pentane yielded desired pure product 7f
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as a colorless solid (1.12 g, 5.1 mmol, 88%). Mp 112−113 °C. H
H
J. Org. Chem. XXXX, XXX, XXX−XXX