Enyne Metathesis
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1-[3-(Triisopropylsilanyloxy)-phenyl]-but-3-en-1-ol
(9):
1H NMR
the homoallylic alcohol. The crude mixture was then purified by flash
column chromatography (SiO2; eluted with hexanes/diethyl ether 25:1) to
give the pure cyclic dialkenylboronic acid 6.
(500 MHz, CDCl3): d = 7.19 (t, J=2.8 Hz, 1H), 6.92 (d, J=7.8 Hz, 1H),
6.89 (s, 1H), 6.80–6.78 (m, 1H), 5.80 (dddd, J=16.3, 13.8, 7.3, 7.1 Hz,
1H), 5.14–5.13 (m, 2H), 4.69 (dd, J=3.7, 2.7 Hz, 1H), 2.51–2.47 (m, 2H),
2.05–1.60 (brs, 1H), 1.26 (sept, J=3.9 Hz, 3H), 1.10 (d, J=3.7 Hz, 18H);
13C NMR (125 MHz, CDCl3): d = 158.0, 145.5, 134.4, 129.3, 118.9, 118.4,
118.3, 117.3, 73.1, 43.8, 17.9, 12.6; IR (neat): n˜ = 3376, 3076, 2944, 2893,
2867, 1642, 1603, 1586, 1484, 1464, 1443, 1385, 1280, 1155, 1058, 1004,
3-(1-Isopropyl-vinyl)-6-{4-[2-(triisopropylsilanyloxy)-ethoxy]-phenyl}-5,6-
dihydro[1,2]oxaborinin-2-ol (18): 1H NMR (500 MHz, CDCl3): d = 7.19
(d, J=8.3 Hz, 2H), 6.79 (d, J=8.8 Hz, 2H), 6.51 (dd, J=4.6, 2.4 Hz, 1H),
4.92 (dd, J=11.5, 4.4 Hz, 1H), 4.86 (s, 1H), 4.70 (s, 1H), 3.96 (d, J=
6.8 Hz, 2H), 3.93 (d, J=6.3 Hz, 2H), 3.23 (s, 1H), 2.48–2.54 (m, 1H),
2.39 (ddd, J=17.7, 5.9, 4.4 Hz, 1H), 2.29 (ddd, J=17.6, 11.5, 2.9 Hz, 1H),
0.95–0.96 (m, 21H), 0.92 (d, J=6.8 Hz, 3H), 0.88 (d, J=6.8 Hz, 3H);
13C NMR (100 MHz, CDCl3): d = 158.2, 156.3, 141.3, 135.2, 126.6, 114.3,
960, 915, 882, 832, 788, 682 cmÀ1
C19H32O2Si+NH4: 338.2516; found: 338.2494 [M+NH4]+.
1-[4-(Triisopropylsilanyloxy)-phenyl]-but-3-en-1-ol (13):
; HRMS (ApCI): m/z: calcd for
1H NMR
(500 MHz, CDCl3): d = 7.20 (d, J=8.3 Hz, 2H), 6.86 (d, J=8.8 Hz, 2H),
5.79 (dddd, J=17.2, 10.2, 7.3, 7.1 Hz, 1H), 5.13–5.12 (m, 1H), 5.13 (d, J=
23.9 Hz, 1H), 4.67 (appt, J=6.4 Hz, 1H), 2.49 (appt, J=6.8 Hz, 2H),
1.99 (s, 1H), 1.24 (septet, J=7.8 Hz, 3H), 1.10 (d, J=7.3 Hz, 18H);
13C NMR (125 MHz, CDCl3): d = 155.7; 136.6, 134.9, 127.2, 120.0, 118.4,
73.3, 44.0, 18.1, 12.9; IR (neat): n˜ = 3358, 2944, 2867, 1641, 1608, 1510,
108.0, 74.6, 69.3, 62.2, 36.6, 31.4, 22.5, 17.7, 13.8, 11.8; IR (neat): n˜ =
3401, 2942, 2867, 1613, 1513, 1463, 1384, 1318, 1304, 1249, 1174, 1133,
1068, 1014, 996, 964, 918, 883, 829, 743, 682, 658 cmÀ1; HRMS (TOF MS
ES+): m/z: calcd for C26H43BO4Si: 459.3102; found: 459.3105 [M+H+].
3-(1-Isopropyl-vinyl)-6-{3-[2-(triisopropylsilanyloxy)-ethoxy]-phenyl}-5,6-
dihydro[1,2]oxaborinin-2-ol (6): 1H NMR (500 MHz, CDCl3): d = 7.19
(t, J=7.8 Hz, 1H), 6.94 (brs, 1H), 6.86 (d, J=7.8 Hz, 1H), 6.77 (dd, J=
8.1, 2.0 Hz, 1H), 6.61 (dd, J=6.1, 2.4 Hz, 1H), 5.03 (dd, J=12.0, 3.9 Hz,
1H), 4.84 (d, J=1.9 Hz, 1H), 4.73 (s, 1H), 4.04–4.00 (m, 4H), 3.35 (s,
1H), 2.64–2.60 (m, 1H), 2.44 (ddd, J=17.6, 6.4, 3.9 Hz, 1H), 2.32 (ddd,
J=17.6, 12.2, 2.4 Hz, 1H), 1.12–1.06 (m, 3H), 1.06–0.99 (m, 21H), 0.96
(d, J=6.8, 3H); 13C NMR (125 MHz, CDCl3): d = 159.1, 158.7, 142.1,
129.5, 129.3, 117.9, 113.9, 111.2, 107.6, 75.3, 69.3, 62.4, 37.2, 31.7, 22.2,
18.1, 12.7, 12.2; IR (neat): n˜ = 3374, 2933, 2862, 1600, 1456, 1380, 1313,
1262, 1123, 1067, 1015, 995, 882 cmÀ1; LRMS (TOF MS ES+): m/z: calcd
for C26H43BO4Si+NH4: 476.3; found: 476.3 [M+NH4+].
1464, 1387, 1266, 1168, 1056, 997, 913, 883, 838, 683 cmÀ1
; HRMS
(ApCI): m/z: calcd for C19H32O2Si+NH4: 338.2516; found: 338.2523
[M+NH4+].
Representative procedure for solid-phase allylation
Reaction sequence used for the generation of 15: A flame-dried, 5 mL ta-
pered flask was charged with macrobeads (58.1 mg, 1.3 mmolgÀ1
,
0.075 mmol) functionalized with the appropriate substituted benzalde-
hyde and THF (1.5 mL) was added. The beads were allowed to swell at
ambient temperature for 10 min before the flask was cooled to À788C
and allylmagnesium bromide (0.75 mL, 0.750 mmol, 10.0 equiv) added
dropwise. A stream of argon that was bubbled through it agitated the
mixture. After 6 h at À788C, the mixture was warmed to 238C and agitat-
ed on a rotary shaker for 19 h. CH2Cl2 (3 mL) was added, causing the
beads to float, and they were transferred to a plastic fritted column.
Beads were rinsed successively with THF (3), THF/H2O (3:1, 3),
THF/H2O (1:1, 3), THF/H2O (1:3, 3), H2O (3), CH3OH (3), THF/
H2O (1:1, 3), THF (3), CH2Cl2 (3), CHCl3 (3), and CDCl3 (1).
The beads were then dried for 24 h in vacuo to afford immobilized homo-
allylic alcohol 15 (53.0 mg).
3-(1-Butyl-vinyl)-6-{3-[2-(triisopropylsilanyloxy)-ethoxy]-phenyl}-5,6-di-
hydro-[1,2]oxaborinin-2-ol (21): 1H NMR (500 MHz, CDCl3): d = 7.18
(t, J=8.1 Hz, 1H), 6.91–6.88 (m, 1H), 6.76 (dd, J=8.4, 2.6 Hz, 1H), 6.61
(dd, J=6.2, 2.6 Hz, 1H), 5.12 (d, J=2.2 Hz, 1H), 4.97 (dd, J=11.7,
3.7 Hz, 1H), 4.81 (s, 1H), 4.00–3.96 (m, 4H), 2.45 (ddd, J=17.6, 6.2,
4.0 Hz, 1H), 2.33 (ddd, J=17.6, 11.9, 2.6 Hz, 1H), 2.20–2.15 (m, 2H),
1.33–1.17 (m, 6H), 1.07–0.99 (m, 21H), 0.82 (t, J=7.32 Hz, 3H);
13C NMR (125 MHz, CDCl3): d = 159.2, 149.2, 144.9, 141.2, 129.5, 118.0,
113.3, 112.4, 112.1, 74.8, 69.4, 62.4, 36.8, 34.6, 30.7, 22.6, 18.0, 14.0, 12.1;
IR (thin film from CDCl3): n˜ = 3412, 2930, 2868, 1726, 1598, 1454, 1383,
1311, 1260, 1121, 1065, 1014, 993, 962, 880, 772, 736 cmÀ1; LRMS (TOF
MS ES+): m/z: calcd for C27H45BO4Si+NH4: 490.3; found: 490.3
[M+NH4+].
Macrobead-bound
1-[4-(diisopropylsilanyloxy)-phenyl]-but-3-en-1-ol
(15): MAS 1H NMR (600 MHz, CDCl3/CD3OD 9:1): d = 7.1–6.2 (m, 4
H + polymer), 5.7–5.6 (brs, 1H), 5.0–4.9 (m, 2H), 4.6–4.5 (brs, 1H),
4.3–4.2 (brs, polymer), 2.5–2.3 (brs, 2H), 1.8–1.0 (m, polymer), 1.0–0.8
(brs, 14H).
3-(1-Isopropyl-vinyl)-6-[4-(triisopropylsilanyloxy)-phenyl]-5,6-dihydro-
[1,2]oxaborinin-2-ol (14): 1H NMR (500 MHz, CDCl3): d = 7.15 (d, J=
8.3 Hz, 2H), 6.77 (d, J=8.8 Hz, 2H), 6.54–6.53 (m, 1H), 4.94 (dd, J=
11.5, 3.4 Hz, 1H), 4.88 (s, 1H), 4.73 (s, 1H), 3.26 (s, 1H), 2.53 (sept, J=
6.8 Hz, 1H), 2.40 (ddd, J=17.5, 5.1, 4.4 Hz, 1H), 2.34–2.28 (m, 1H), 1.16
(sept, J=7.8 Hz, 3H), 1.00 (d, J=7.3 Hz, 18H), 0.94 (m, 3H), 0.90 (m,
3H); 13C NMR (125 MHz, CDCl3): d = 156.4, 155.2, 141.3, 135.5, 126.5,
119.6, 108.1, 74.6, 36.6, 31.2, 22.0, 21.6, 17.8, 12.6 cmÀ1; IR (thin film from
CDCl3): n˜ = 3422, 2945, 2867, 1010, 1512, 1463, 1383, 1318, 1264, 1168,
1093, 1014, 914, 884, 833, 683 cmÀ1; LRMS (TOF MS ES+): m/z: calcd
for C24H39BO3Si: 416.3; found: 416.3 [M+H+].
Representative procedure for comparative studies in the solution phase
Reaction using Hoveyda–Grubbs pre-catalyst 2: To a solution of the al-
kynylboronic ester 25 (55.0 mg, 0.280 mmol) in toluene (0.25 mL) was
added the homoallylic alcohol 5 (53.8 mg, 0.148 mmol) as a solution in
toluene (0.2 mL), and residual homoallylic alcohol was introduced with
two additional toluene rinses (20.15 mL). After 5 min, catalyst
2
(4.6 mg, 5 mol%) was introduced as a solid. The vessel was purged with
argon, then heated at 808C for 24 h. The crude reaction mixture was
cooled to 238C, then concentrated in vacuo, giving a dark brown oil,
1
which was taken up in CDCl3 and assayed by H NMR at 500 MHz, using
3-(1-Isopropyl-vinyl)-6-[3-(triisopropylsilanyloxy)-phenyl]-5,6-dihydro-
[1,2]oxaborinin-2-ol (10): 1H NMR (400 MHz, CDCl3): d = 7.14 (t, J=
8.0 Hz, 1H), 6.92–6.87 (m, 2H), 6.74 (dd, J=8.2, 1.5 Hz, 1H), 6.58 (app
d, J=3.3 Hz, 1H), 4.99 (dd, J=11.5, 3.7 Hz, 1H), 4.94 (s, 1H), 4.78 (s,
1H), 2.60–2.54 (m, 1H), 2.50–2.43 (m, 1H), 2.35–2.28 (m, 1H), 1.24–1.14
(m, 3H), 1.03 (d, J=7.7 Hz, 18H), 0.99 (d, J=6.6 Hz, 3H), 0.94 (d, J=
7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3): d = 156.5, 156.2, 144.8, 141.4,
129.3, 119.0, 118.2, 117.1, 108.4, 74.8, 36.8, 31.4, 22.2, 21.8, 18.0, 12.8; IR
(thin film from CDCl3): n˜ = 3878, 2923, 2867, 1605, 1585, 1485, 1463,
1381, 1314, 1282, 1154, 1077, 1005, 877, 841, 785, 728, 682 cmÀ1; LRMS
(TOF MS ES+): m/z: calcd for C24H39BO3Si: 416.3; observed 416.3
[M+H+].
increased relaxation time. Conversions are measured relative to the
dienyl proton at 6.6 ppm in the alkenyl boronic ester and the two alkene
protons at 5.1–5.2 ppm in the homoallylic alcohol. The crude mixture was
then purified by flash column chromatography (silica gel; eluted with
hexanes/diethyl ether 25:1) to give the pure cyclic dialkenylboronic acid
6.
Reaction using Grubbs pre-catalyst 3: To a solution of the alkynylboronic
ester 25 (61.2 mg, 0.312 mmol) in toluene (0.25 mL) was added the homo-
allylic alcohol 5 (59.9 mg, 0.164 mmol) as a solution in toluene (0.2 mL),
and residual homoallylic alcohol was introduced with two additional tolu-
ene rinses (20.15 mL). After 5 min, catalyst 3 (7.0 mg, 5 mol%) was in-
troduced as a solid. The vessel was purged with argon, then heated at
808C for 24 h. The crude reaction mixture was cooled to 238C, then con-
centrated in vacuo, giving a dark brown oil, which was taken up in
CDCl3 and assayed by 1H NMR at 500 MHz, using increased relaxation
time. Conversions are measured relative to the alkene proton at 6.6 ppm
in the alkenyl boronic ester and the two alkene protons at 5.1–5.2 ppm in
Representative procedure for comparative studies on the solid phase
Reaction using Hoveyda–Grubbs pre-catalyst 2: To the alkynylboronic
ester 25 (12.7 mg, 0.065 mmol) was added the macrobead bound homoal-
lylic alcohol 15 (6.6 mg, 1.3 mmolgÀ1) in one portion, with the beads no-
ticeably swelling. Toluene (0.25 mL) was added, and the beads were al-
Chem. Eur. J. 2005, 11, 5086 – 5093
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5091