N. PraveenGanesh, P. Y. Chavant
FULL PAPER
45 min to the NaBH4 suspension, during which time the tempera-
ture increased to 40 °C. The evolved gases were bubbled through
the solution of diol in the second flask. Throughout the process, a
small stream of nitrogen (2–5 bubbles per second) was applied to
the whole apparatus to ensure complete transfer of the diborane.
At the end of the addition of methanesulfonic acid, the temperature
of the second flask was increased to 20 °C and the flow of N2
was continued for 1 h. This step allowed the elimination of excess
diborane from the solution of MPBH. The solution was transferred
to a volumetric flask and diluted to 50 mL. 11B and 1H NMR indi-
cated that the conversion of diol was quantitative. Thus, the solu-
tion was considered 1 in MPBH. The solution could be kept
at 4 °C for several months without any change. Storage at room
temperature was deleterious.
(dd, J = 13.7, 11.8 Hz, 1 H), 1.36 (s, 3 H), 1.35 (s, 3 H), 1.33 (d, J
= 6.7 Hz, 3 H) ppm. 13C NMR (75.5 MHz, CDCl3): δ = 140.1 (C),
133.8 (CH), 128.2 (CH), 70.7 (C), 64.8 (CH), 46.0 (CH2), 31.3
(CH3), 28.1 (CH3), 23.2 (CH3), 21.6 (CH3) ppm. 11B NMR
(96.3 MHz, CDCl ): δ = 27.1 ppm. IR (neat): ν = 2971, 2932, 2908,
˜
3
1612, 1406, 815, 766, 724 cm–1. MS (DCI): m/z (%) = 236 (100) [M
+ NH4]+, 144 (50). HRMS (ES): calcd. for C13H19O211B 218.1473;
found 218.1479.
2-(4-Bromophenyl)-4,4,6-trimethyl-1,3,2-dioxaborinane (4d): Yield
185 mg, 65%. 1H NMR (400 MHz, CDCl3): δ = 7.66 (d, J =
8.2 Hz, 2 H), 7.45 (d, J = 8.2 Hz, 2 H), 4.32 (dqd, J = 11.7, 6.2,
3.0 Hz, 1 H), 1.86 (dd, J = 13.9, 3.0 Hz, 1 H), 1.57 (dd, J = 13.9,
11.7 Hz, 1 H), 1.36 (s, 3 H), 1.35 (s, 3 H), 1.33 (d, J = 6.2 Hz, 3
H) ppm. 13C NMR (75.5 MHz, CDCl3): δ = 135.4 (2ϫCH), 133.7
(C), 130.6 (2ϫCH), 125.1 (C), 71.2 (C), 65.1 (CH), 46.0 (CH2),
31.2 (CH3), 28.1 (CH3), 23.1 (CH3) ppm. 11B NMR (96.3 MHz,
4,4,6-Trimethyl-1,3,2-dioxaborinane (1: MPBH):[11] 1H NMR
(300 MHz, CDCl3): δ = 4.16 (dqd, J = 11.8, 6.2, 3.0 Hz, 1 H), 1.76
(ddd, J = 13.9, 3.0, 1.7 Hz, 1 H), 1.50 (dd, J = 13.9, 11.8 Hz, 1 H),
1.27 (s, 3 H), 1.26 (s, 3 H), 1.23 (d, J = 6.21 Hz, 3 H) ppm. 13C
NMR (75.5 MHz, CDCl3): δ = 70.8, 64.6, 46.1, 31.0, 28.1,
CDCl ): δ = 26.7 ppm. IR (neat): ν = 2968, 2928, 2906, 1583, 1403,
˜
3
1304, 823, 767, 723 cm–1. MS (DCI): m/z (%) = 284 (100) [M]+,
283 (27), 282 (98), 281 (29). HRMS (ES): calcd. for C12H16BrO211B
282.0463; found 282.0459.
22.9 ppm. 11B NMR (96 MHz, CDCl3): δ
170 Hz) ppm. IR (neat): ν = 2551, 2498 cm–1.
= 25.2 (d, J =
˜
4,4,6-Trimethyl-2-(naphthalen-1-yl)-1,3,2-dioxaborinane (4f): Yield
136 mg, 60%. 1H NMR (400 MHz, CDCl3): δ = 8.79 (d, J =
8.4 Hz, 1 H), 8.02 (d, J = 6.8 Hz, 1 H), 7.85 (d, J = 8.3 Hz, 1 H),
7.79 (d, J = 8.1 Hz, 1 H), 7.50–7.38 (m, 3 H), 4.42 (dqd, J = 12.0,
6.2, 3.0 Hz, 1 H), 1.88 (dd, J = 13.6, 3.0 Hz, 1 H), 1.67 (dd, J =
13.6, 12.0 Hz, 1 H), 1.44 (s, 3 H), 1.43 (s, 3 H), 1.40 (d, J = 6.2 Hz,
3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 136.8 (C), 134.2
(CH), 133.4 (C), 130.6 (CH), 128.4 (CH), 128.4 (CH), 125.8 (CH),
125.1 (CH), 125.0 (CH), 71.5 (C), 65.3 (CH), 46.0 (CH2), 31.4
(CH3), 28.3 (CH3), 23.3 (CH3) ppm. 11B NMR (128 MHz, CDCl3):
General Procedure for the Borylation of Aryl Halides: In a 20-mL
Schlenk tube, [PdCl2(TPP)2] (21 mg, 0.03 mmol) was dissolved in
toluene (4.0 mL). TEA (0.420 mL, 3.0 mmol), the aryl halide
(1.0 mmol) and a 1 solution of MPBH in toluene (1.5 mL,
1.5 mmol) were then added and the reaction mixture stirred for the
indicated time at 80 °C. After completion of the reaction, the mix-
ture was diluted with diethyl ether and washed once with brine.
The organic layer was dried with MgSO4 and the solvent removed
under reduced pressure. The residue was purified by flash column
chromatography (SiO2 deactivated with 3% Et3N, eluent: pentane/
ether) to give the expected arylboronate (Table 2).
δ = 27.8 ppm. IR (neat): ν = 3038, 2973, 2926, 1509, 1459, 1303,
˜
804, 779 cm–1. MS (DCI): m/z (%) = 272 (100) [M + NH4]+, 271
(62), 144 (29). HRMS (APPI-APCI): calcd. for C16H19O211B
254.1473; found 254.1463.
The same procedure was repeated on a 10-mmol scale (Table 2,
entry 1): In
a 50-mL Schlenk tube, [PdCl2(TPP)2] (140 mg,
Methyl 4-(4,4,6-Trimethyl-1,3,2-dioxaborinan-2-yl)benzoate (4g):
0.2 mmol) was dissolved in toluene (40 mL). TEA (4.20 mL,
3.0 mmol), 4-iodoanisole (3a; 2.30 g, 10 mmol) and a 1 solution
of MPBH in toluene (15 mL; 15 mmol) were then added and the
reaction mixture stirred for 3 h at 80 °C. The mixture was diluted
with diethyl ether (100 mL) and washed once with brine (10 mL).
The organic layer was dried with MgSO4 and concentrated. The
material was purified by kugelrohr distillation.
1
Yield 179 mg, 68%. H NMR (300 MHz, CDCl3): δ = 8.00 (d, J =
8.1 Hz, 2 H), 7.88 (d, J = 8.1 Hz, 2 H), 4.38 (dqd, J = 11.5, 6.2,
3.0 Hz, 1 H), 3.93 (s, 3 H), 1.91 (dd, J = 13.9, 3.0 Hz, 1 H), 1.62
(dd, J = 13.9, 11.5 Hz, 1 H), 1.41 (s, 3 H), 1.40 (s, 3 H), 1.38 (d, J
= 6.2 Hz, 3 H) ppm. 13C NMR (75.5 MHz, CDCl3): δ = 167.3 (C),
133.6 (C), 131.4 (CH), 128.3 (CH), 71.2 (C), 65.1 (CH), 51.9 (CH3),
45.9 (CH2), 31.1 (CH3), 28.1 (CH3), 23.0 (CH3) ppm. 11B NMR
[2-(4-Methoxyphenyl)-4,4,6-trimethyl-1,3,2-dioxaborinane (4a; RN
934558-31-3, 208 mg, 89%], 2-phenyl-4,4,6-trimethyl-1,3,2-diox-
aborinane (4e; RN 15961-35-0, 123 mg, 81% isolated yield) and 4-
(4,4,6-trimethyl-1,3,2-dioxaborinan-2-yl)]phenylamine, (4k; RN
934558-32-4, 135 mg, 71%) have been described elsewhere.[15]
(96.3 MHz, CDCl ): δ = 27.1 ppm. IR (neat): ν = 2971, 2949, 2908,
˜
3
1725, 1561, 1432, 1166, 766, 711 cm–1. MS (ESI): m/z = 263 [M +
H]+, 279 [M + Na]+. HRMS (APPI-APCI): calcd. for C14H20O411B
263.14492; found 263.14503.
4-(4,4,6-Trimethyl-1,3,2-dioxaborinan-2-yl)benzonitrile (4h): Yield
166 mg, 73%. 1H NMR (300 MHz, CDCl3): δ = 7.88 (d, J =
7.9 Hz, 2 H), 7.59 (d, J = 7.9 Hz, 2 H), 4.35 (dqd, J = 11.6, 6.2,
3.0 Hz, 1 H), 1.89 (dd, J = 14.0, 3.0 Hz, 1 H), 1.59 (dd, J = 14.0,
11.6 Hz, 1 H), 1.38 (s, 3 H), 1.37 (s, 3 H), 1.35 (d, J = 6.2 Hz, 3
H) ppm. 13C NMR (75.5 MHz, CDCl3): δ = 134.1 (CH), 130.8
(CH), 119.2 (C), 113.5 (C), 71.6 (C), 65.3 (CH), 45.9 (CH2), 31.1
(CH3), 28.1 (CH3), 23.0 (CH3) ppm. 11B NMR (128 MHz, CDCl3):
Dimethyl[4-(4,4,6-trimethyl-1,3,2-dioxaborinan-2-yl)phenyl]amine (4b):
1
Yield 205 mg, 83%. H NMR (400 MHz, CDCl3): δ = 7.67 (d, J =
8.7 Hz, 2 H), 6.67 (d, J = 8.7 Hz, 2 H), 4.29 (dqd, J = 11.7, 6.2,
3.0 Hz, 1 H), 2.95 (s, 6 H), 1.81 (dd, J = 13.8, 3.0 Hz, 1 H), 1.54
(dd, J = 13.8, 11.7 Hz, 1 H), 1.34 (s, 3 H), 1.32 (s, 3 H), 1.31 (d, J
= 6.2 Hz, 3 H) ppm. 13C NMR (75.5 MHz, CDCl3): δ = 152.1 (C),
135.0 (CH), 111.4 (CH), 70.5 (C), 64.6 (CH), 46.1 (CH2), 40.3
(2ϫCH3), 31.4 (CH3), 28.2 (CH3), 23.3 (CH3) ppm. 11B NMR
δ = 26.3 ppm. IR (neat): ν = 2972, 2928, 2226, 1408, 1304, 1164,
˜
834, 768, 738 cm–1. MS (DCI): m/z (%) = 247 (100) [M + NH4]+.
(128 MHz, CDCl ): δ = 26.9 ppm. IR (neat): ν = 2970, 2930, 2906,
˜
3
1605, 1300, 945, 816 cm–1. MS (DCI): m/z = 248 [M + H]+. HRMS
HRMS (ES): calcd. for C13H16NO211B 229.1269; found 229.1277.
(ES): calcd. for C14H23O2N10B 247.18527; found 247.18500.
4,4,6-Trimethyl-2-(3-nitrophenyl)-1,3,2-dioxaborinane (4i): Yield
125 mg, 50%. 1H NMR (400 MHz, CDCl3): δ = 8.62 (d, J =
2.5 Hz, 1 H), 8.23 (ddd, J = 7.7, 2.5, 1.1 Hz, 1 H), 8.10 (td, J =
7.7, 1.1 Hz, 1 H), 7.49 (t, J = 7.7 Hz, 1 H), 4.38 (dqd, J = 11.8,
2-(4-Methylphenyl)-4,4,6-trimethyl-1,3,2-dioxaborinane (4c): Yield
171 mg, 85%. 1H NMR (300 MHz, CDCl3): δ = 7.70 (d, J =
7.7 Hz, 2 H), 7.14 (d, J = 7.7 Hz, 2 H), 4.32 (dqd, J = 11.8, 6.7,
3.0 Hz, 1 H), 2.34 (s, 3 H), 1.84 (dd, J = 13.7, 3.0 Hz, 1 H), 1.57 6.2, 3.0 Hz, 1 H), 1.91 (dd, J = 13.9, 3.0 Hz, 1 H), 1.62 (dd, J =
4694
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Eur. J. Org. Chem. 2008, 4690–4696