C
K. Wang, R. W. Bates
Paper
Synthesis
Hydroboration; General Procedure Method A
1H NMR (400 MHz, CDCl3): δ = 6.74 (t, J = 7.5 Hz, 1 H), 6.58 (ddd, J =
18.0, 7.7, 3.6 Hz, 1 H), 5.43 (d, J = 18.0 Hz, 1 H), 3.73 (s, 3 H), 2.23–2.11
(m, 2 H), 2.06–2.00 (m, 2 H), 1.83 (s, 3 H), 1.65–1.39 (m, 3 H), 1.27 (s,
12 H), 0.91 (d, J = 4.0 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 168.9, 153.0, 142.9, 127.6, 83.2, 51.9,
43.6, 35.5, 32.3, 26.4, 25.0, 19.7, 12.5.
Tri(2-furyl)phosphine (4.7 mg, 0.02 mmol) and [Rh(CO)2Cl]2 (3.9 mg,
0.01 mmol) were mixed in toluene (10 mL) at r.t. The mixture was
stirred for 10 min and then the alkyne (1 mmol) in toluene (1 mL) and
4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1, 174 μL, 1.2 mmol) were
added. The mixture was stirred under N2 at r.t. (TLC monitoring). Af-
ter quenching with H2O, the mixture was extracted with Et2O. The or-
ganic phase was dried (MgSO4) and then concentrated under reduced
pressure. The residue was purified by column chromatography (silica
gel).
MS (ESI): m/z = 323.02 [M + H]+.
HRMS (EI): m/z [M + Na]+ calcd for C18H31BO4Na: 345.2213; found:
345.2221.
(E)-4,4,5,5-Tetramethyl-2-styryl-1,3,2-dioxaborolane (4)17
Hydroboration; General Procedure Method B
Colourless oil; yield: 369 mg (81%, Method A).
1H NMR (400 MHz, CDCl3): δ = 7.48–7.26 (m, 6 H), 6.17 (d, J = 16.0 Hz,
Following Method A, but with a ratio of tri(2-furyl)phosphine/
[Rh(CO)2Cl]2 1:1 [i.e., ratio (2-furyl)3P/Rh 2:1].
1 H), 1.32 (s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 149.7, 137.7, 129.1, 128.7, 127.2,
Hydroboration; General Procedure Method C
116.5 (br), 83.6, 24.7.
Following Method A, but with preformed Rh[P(2-furyl)3]2(CO)Cl (0.02
mmol) as the catalyst.
(E)-2-(Hex-1-enyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (5)18
Rh[P(2-furyl)3]2(CO)Cl (9)
Colourless oil; yield: 1.030 g (80%, Method A).
1H NMR (400 MHz, CDCl3): δ = 6.3 (dt, J = 16.0, 6.8 Hz, 1 H), 5.42 (d, J =
16.0 Hz, 1 H), 2.15 (dt, J = 6.8, 6.4 Hz, 2 H), 1.42–1.26 (m, 16 H), 0.88
(t, J = 7.3 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 154.9, 118.8 (br), 83.2, 35.7, 30.6, 25.0,
22.5, 14.1.
Tri(2-furyl)phosphine (474 mg, 2.04 mmol) was added to a solution
of [Rh(CO)2Cl]2 (200 mg, 0.51 mmol) in toluene (20 mL) at r.t. A pale
yellow precipitate appeared immediately. The mixture was stirred for
10 min and then cooled to 0 °C. The mixture was filtered and washed
with cold EtOH (2 × 10 mL) and Et2O (2 × 10 mL), and then the pale
yellow solid was dried by suction in air to give pale yellow cubic crys-
tals; yield: 640 mg (99%); mp 168–169 °C.
(E)-tert-Butyldimethyl[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
IR (neat): 2021, 1380, 1210, 1120, 1000, 720 cm–1
.
2-yl)allyloxy]silane (6)19
Colourless oil; yield: 280 mg (80%, Method A).
(±)-Methyl (E)-2,6-Dimethylnon-2-en-8-ynoate (2)
1H NMR (400 MHz, CDCl3): δ = 6.67 (dt, J = 18.0, 3.6 Hz, 1 H), 5.75 (dd,
J = 18.0, 1.8 Hz, 1 H), 4.24 (dd, J = 3.6, 1.4 Hz, 2 H), 1.27 (s, 9 H), 0.91 (s,
12 H), 0.06 (s, 6 H).
O3 in O2 was bubbled through a solution of 4,8-dimethylnon-7-en-1-
yne16 (1.00 g, 6.65 mmol) in CH2Cl2 (20 mL) at –78 °C (TLC monitor-
ing). When the starting material had been consumed, the mixture
was flushed with O2 for 10 min. After warming to r.t., methyl 2-
(triphenylphosphoranylidene)propanoate (2.32 g, 6.65 mmol) was
added and the mixture was heated at reflux for 4 h. The mixture was
cooled to r.t., and the solvent was removed under reduced pressure.
The residue was taken up in the minimum amount of CH2Cl2, and ex-
cess hexane was added. The precipitate was removed by filtration
through Celite, the filtrate was concentrated in vacuo and purified via
column chromatography to give ester 2 (1.00 g, 77%) as a colourless
oil.
13C NMR (100 MHz, CDCl3): δ = 152.4, 83.4, 64.8, 26.2, 25.0, 18.7, –5.1.
(E)-2-[4-(Methoxymethoxy)pent-1-enyl]-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (7)
Colourless oil; yield: 299 mg (75%, Method A).
IR (neat): 2976, 2929, 2887, 1635, 1466, 1400, 1363, 1321, 1146,
1130, 1101, 1038, 970, 918, 849 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 6.62–6.54 (m, 1 H), 5.47 (d, J = 16.0 Hz,
1 H), 4.65–4.58 (m, 2 H), 3.80–3.75 (m, 1 H), 3.20 (s, 3 H), 2.43–2.24
(m, 2 H), 1.23 (s, 12 H), 1.14 (d, J = 5.9 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 150.4, 121.5 (br), 95.0, 83.2, 72.4, 55.4,
43.6, 25.0, 20.4.
IR (neat): 3302, 2114, 1713, 1651, 1381, 1265, 1096, 934, 818, 741,
633 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 6.75 (t, J = 7.3 Hz, 1 H), 3.73 (s, 3 H),
2.20–2.14 (m, 4 H), 1.96 (s, 1 H), 1.84 (s, 3 H), 1.72–1.60 (m, 3 H), 1.00
(d, J = 6.4 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 168.8, 142.4, 127.9, 83.0, 69.7, 51.9,
34.7, 32.2, 26.4, 25.8, 19.5, 12.6.
MS (ESI): m/z = 257.
HRMS (EI): m/z [M + H]+ calcd for C13H26BO4: 257.1924; found:
257.1937.
MS (ESI): m/z = 217.99 [M + Na]+.
HRMS (EI): m/z [M + H]+ calcd for C12H19O2: 195.1385; found:
(E)-2-Methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)but-
3-en-2-ol (8)20
195.1383.
Colourless oil; yield: 306 mg (61%, Method A).
1H NMR (400 MHz, CDCl3): δ = 6.69 (d, J = 20.0 Hz, 1 H), 5.59 (d, J =
20.0 Hz, 1 H), 1.72 (br, 1 H), 1.29–1.17 (m, 18 H).
13C NMR (100 MHz, CDCl3): δ = 160.0, 113.7 (br), 83.5, 72.0, 29.3, 24.8.
(±)-Methyl (2E,8E)-2,6-Dimethyl-9-(4,4,5,5-tetramethyl-1,3,2-di-
oxaborolan-2-yl)nona-2,8-dienoate (3)
Colourless oil; yield: 639 mg (77%, Method C).
IR (neat): 3390, 2978, 2953, 2926, 2872, 1713, 1634, 1435, 1362,
1321, 1269, 1250, 1165, 1146, 1092 cm–1
.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–D