G. R. Stephenson, C. Roe, E. J. Sandoe
FULL PAPER
Following general procedure C (Variation 1), the aryllithium rea-
gent formed from (2-bromo-4,5-dimethoxyphenyl) methyloxyme-
thyl ether (2 equiv., 1.746 g, 6.0 mmol) and n-butyllithium (2.5 m in
hexanes) (2 equiv., 6.0 mmol, 2.4 mL) in diethyl ether (40 mL), was
treated with tricarbonyl[(1,2,3,4,5-η)-1,4-dimethoxycyclohexadi-
enyl]iron hexafluorophosphate (4) (1 equiv., 1.1 g, 3.0 mmol) in
dichloromethane (20 mL) for 1 h at –100 °C. Column chromatog-
raphy (diethyl ether/petroleum ether gradient) afforded 13a as a
(50 mL), was treated with hexafluorophosphate 4 (1.0 equiv.,
1.21 g, 3.31 mmol) in dichloromethane (40 mL) for 4 h at –78 °C.
Column chromatography eluting with a gradient of 2:1 to 1:1 hex-
ane/diethyl ether afforded 13c (1.02 g, 1.70 mmol, 51%) as a pale
brown gum; Rf = 0.28 (1:1 diethyl ether/hexane). 1H NMR
(400 MHz, CDCl3): δ = 7.40 (s, 1 H, 3Ј-H), 7.03 (s, 1 H, 6Ј-H),
3
3
5.29 (dd, JH,H = 6.8, 2.4 Hz, 1 H, 3-H), 4.91 (d, JH,H = 14.5 Hz,
3
1 H, OCH2), 4.77 (d, JH,H = 14.5 Hz, 1 H, OCH2), 3.92 (s, 3 H,
1
pale brown gum (0.460 g, 0.94 mmol, 31%). H NMR (270 MHz,
12-OMe), 3.87 (s, 3 H, 11-OMe), 3.64 (s, 3 H, 2-OMe), 3.29 (m, 1
3
CDCl3): δ = 7.08 (s, 1 H, 3Ј-C or 6Ј-C), 7.07 (s, 1 H, 3Ј-C or 6Ј- H, 1-H), 2.98 (d, JH,H = 6.8 Hz, 1 H, 4-H), 2.91 (s, 3 H, 5-OMe),
3
3
3
C), 5.31 (dd, JH,H = 6.9, 2.3 Hz, 1 H, 3-H), 4.71 (m, 4 H,
2.23 (dd, JH,H = 14.5, 3.8 Hz, 1 H, 6β-H), 2.09 (dd, JH,H = 14.5,
3
CH2OCH2), 3.93 (s, 3 H, Ar-OMe), 3.88 (s, 3 H, Ar-OMe), 3.64 (s,
2.1 Hz, 1 H, 6α-H), 1.17 (m, 3 H, CHSi), 1.09 (d, JH,H = 6.7 Hz,
3 H, 2-OMe), 3.41 (s, 3 H, OMe), 3.32 (m, 1 H, 1-H), 3.01 (d, 3JH,H
18 H, Me) ppm. 13C NMR (101 MHz, CDCl3): δ = 210.5 (Fe-CO),
147.7 (4Ј-C or 5Ј-C), 145.5 (4Ј-C or 5Ј-C), 139.9 (2-C), 134.0 (1Ј-
3
= 6.9 Hz, 1 H, 4-H), 2.93 (s, 3 H, 5-OMe), 2.34 (dd, JH,H = 14.8,
3
4.0 Hz, 1 H, 6β-H), 2.17 (dd, JH,H = 14.8, 2.0 Hz, 1 H, 6α-H) C), 132.5 (2Ј-C), 111.9 (6Ј-C), 110.3 (3Ј-C), 82.5 (5-C), 65.2 (3-C),
ppm. 13C NMR (67.8 MHz, CDCl3): δ = 210.4 (Fe-CO), 147.6 (4Ј- 62.3 (ArCH2O), 56.2 (Ar-OMe), 55.6 (Ar-OMe), 54.9 (4-C), 54.6
C or 5Ј-C), 146.3 (4Ј-C or 5Ј-C), 139.9 (2-C), 134.5 (1Ј-C or 2Ј-C),
(2-OMe), 51.4 (1-C), 49.2 (5-OMe), 42.3 (6-C), 18.1 (Me), 12.0
= 2942 and 2866 (C–H), 2049 and
130.2 (1Ј-C or 2Ј-C), 112.4 (6Ј-C), 111.8 (3Ј-C), 95.9 (OCH2O), 82.2 (CHSi) ppm. IR (CDCl ): ν
˜
3
max
(5-C), 66.6 (ArCH2O), 64.9 (3-C), 56.0 (OMeMOM), 55.6 (5Ј-OMe), 1984 and 1965 (C=O), 1581 and 1506 (C=C) cm–1. MS (CI): m/z
55.2 (4Ј-OMe), 54.7 (4-C), 54.4 (2-OMe), 51.3 (1-C), 49.2 (5-OMe),
42.8 (6-C) ppm. IR (neat): ν = 2938, 2048, 1980 (C=O), 1606,
(%) = 603 (5) [M + H]+, 571 (82), 486 (66), 430 (33), 257 (100).
HRMS (CI): m/z: calcd. for C29H43O828Si54Fe: 603.2071; found
603.2078 [M + H]+.
˜
max
1492, 1266, 1107, 1051, 798 cm–1. MS (EI): m/z (%) = 434 (14)
[M – 2CO]+, 406 (6) [M – 3CO]+, 374 (37), 344 (37), 318 (100), 314
(48), 257 (54), 226 (85), 211 (25), 195 (18), 166 (28), 151 (55).
HRMS (EI): m/z: calcd. for C20H2654FeO7 (M – 2CO): 434.1028;
found 434.1028, and tricarbonyl[(2,3,4,5-η)-4-methoxy-2,4-cyclo-
hexadien-1-one]iron(0)[49,50] (0.168 g, 0.64 mmol, 21%).
Preparation of (1-Arylcyclohexadienyl)iron Salts
(؎)-Tricarbonyl{(1,2,3,4,5-η)-4-methoxy-1-[3Ј-methoxy-2Ј-[2ЈЈ-(tri-
methylsilyl)ethoxymethoxy]phenyl]-2,4-cyclohexadienyl}iron(1+)
Hexafluorophosphate(1–) (7b): Following general procedure D
(Variation 2), triphenylcarbenium hexafluorophosphate (1 equiv.,
691 mg, 1.78 mmol), tricarbonyl{(1,2,3,4-η)-2,5β-dimethoxy-5α-
[3Ј-methoxy-2Ј-[(2ЈЈ-(trimethylsilyl)ethoxy]methoxyphenyl]-1,3-
cyclohexadiene}iron(0) (6b) (1 equiv., 948 mg, 1.78 mmol) and po-
tassium carbonate (0.98 equiv., 140 mg, 1.75 mmol) in dichloro-
methane (5 mL) were stirred 0 °C for 10 min and then added drop-
wise to dry diethyl ether (200 mL) to form a yellow precipitate.
Reprecipitation (acetone/diethyl ether) afforded 7b as an unstable
yellow solid (125 mg, 0.193 mmol, 11 %). H NMR (270 MHz,
(؎)-Tricarbonyl[(1,2,3,4-η)-2,5β-dimethoxy-5α-(2Ј-trimethylsilyl-
ethoxymethoxy-methyl-4Ј,5Ј-dimethoxyphenyl)-1,3-cyclohexadiene]-
iron(0) (13b): Following general procedure C (Variation 1), the aryl-
lithium reagent formed from 2-bromo-4,5-dimethoxybenzyl 2-(tri-
methylsilyl)ethoxymethoxymethyl ether (1.2 equiv., 2.714 g,
7.2 mmol) and n-butyllithium (2.5 m in hexanes) (1.2 equiv.,
2.9 mL, 7.2 mmol) in diethyl ether (30 mL), was treated with tricar-
bonyl[(1,2,3,4,5-η)-1,4-dimethoxycyclohexadienyl]iron hexafluoro-
phosphate (4) (1 equiv., 2.2 g, 6.0 mmol) in dichloromethane
(20 mL) for 1 h at –100 °C. Column chromatography (20% diethyl
ether/80 % petroleum ether) afforded 13b as a pale brown gum
3
CD3COCD3): δ = 7.39 (dd, JH,H = 6.4, 2.3 Hz, 1 H, 3-H), 7.28–
3
7.19 (m, 2 H, 5Ј-H, 6Ј-H), 7.02 (dd, JH,H = 7.3, 2.0 Hz, 1 H, 4Ј-
3
3
1
H), 6.67 (d, JH,H = 6.4 Hz, 1 H, 2-H), 5.31 (d, JH,H = 8.3 Hz, 1
(1.605 g, 2.79 mmol, 46%). H NMR (270 MHz, CDCl3): δ = 7.03
3
3
3
H, OCH2O), 5.29 (d, JH,H = 8.3 Hz, 1 H, OCH2O), 4.42 (d, JH,H
(s, 2 H, 3Ј-H, 6Ј-H), 5.26 (dd, JH,H = 6.9, 2.6 Hz, 1 H, 3-H), 4.73
= 6.3 Hz, 1 H, 5-H), 4.05 (s, 3 H, 4-OMe), 3.92 (s, 3 H, ArOMe),
(m, 2 H, ArOCH2), 4.67 (s, 2 H, OCH2O), 3.90 (s, 3 H, Ar-OMe),
3.85 (s, 3 H, Ar-OMe), 3.65 (m, 2 H, OCH2), 3.61 (s, 3 H, 2-OMe),
3
3.69 (m, 3 H, OCH2, 6β-H), 2.97 (d, JH,H = 16.2 Hz, 1 H, 6α-H),
3
3
0.91 (dd, JH,H = 9.7, 7.1 Hz, 2 H, CH2Si), –0.01 (s, 9 H, SiMe3)
3.27 (m, 1 H, 1-H), 2.97 (d, JH,H = 6.9 Hz, 1 H, 4-H), 2.89 (s, 3
ppm. IR (CH C1 ): ν
= 2106, 2049 (CO) cm–1. MS (FAB): m/z
˜
max
3
2
2
H, 5-OMe), 2.31 (dd, JH,H = 14.5, 3.6 Hz, 1 H, 6β-H), 2.14 (dd,
(%) = 501 (100) [M – PF6]+, 417 (34) [M – PF6 – 3CO]+, 387 (8),
370 (5), 357 (20), 302 (7), 285 (29), 226 (13). HRMS (FAB): m/z:
calcd. for C23H29O754Fe28Si: 501.1032; found 501.1032 [M – PF6]+.
3JH,H = 14.5, 2.6 Hz, 1 H, 6α-H) 0.95 (m, 2 H, CH2Si), –0.03 (s, 9
H, SiMe3) ppm. 13C NMR (67.8 MHz, CDCl3): δ = 210.3 (Fe-CO),
147.6 (4Ј-C or 5Ј-C), 146.2 (4Ј-C or 5Ј-C), 139.9 (2-C), 134.4 (1Ј-C
or 2Ј-C), 130.3 (1Ј-C or 2Ј-C), 112.3 (6Ј-C), 111.8 (3Ј-C), 94.2
(OCH2O), 82.1 (5-C), 66.5 (ArCH2O), 65.0 (OCH2), 64.8 (3-C),
55.9 (5Ј-OMe), 55.5 (4Ј-OMe), 54.6 (4-C), 54.3 (2-OMe), 51.3 (1-
C), 49.2 (5-OMe), 42.8 (6-C), 17.8 (Si-C), –1.7 (SiMe3) ppm. IR
(؎)-Tricarbonyl[(1,2,3,4,5-)-4-methoxy-1-(2Ј-methoxymethoxyphen-
yl)-2,4-cyclohexadienyl]iron(1+) Tetrafluoroborate(1–) (7c): Follow-
ing general procedure D (Variation 2), triphenylcarbenium tetra-
fluoroborate (1 equiv., 203 mg, 0.615 mmol), tricarbonyl[(1,2,3,4-
η)-2,5β-dimethoxy-5α-(2Ј-methoxymethoxyphenyl)-5β-methoxycy-
clohexadiene]iron(0) (6c) (1 equiv., 256 mg, 0.615 mmol) and potas-
sium carbonate (0.2 equiv., 100 mg, 1.25 mmol) in dichloromethane
(7 mL) were stirred 0 °C for 10 min and then added added dropwise
to dry diethyl ether (200 mL) to form a yellow precipitate. Repre-
cipitation (acetone/diethyl ether) afforded 7c as a yellow solid
(neat): νmax = 2053, 2048, 1983 (C=O), 1490, 1266, 1106, 838 cm–1.
˜
MS (EI): m/z (%) = (%)576 (1) [M]+, 520 (3) [M – 2CO]+, 492 (5)
[M – 3CO]+, 460 (43) [M – MeOH – 3CO]+, 404 (50) [M – MeOH –
Fe – 3CO]+, 314 (41), 258 (48), 257 (63), 226 (67), 211 (22), 73
(100); and tricarbonyl[(2,3,4,5-η)-4-methoxy-2,4-cyclohexadien-1-
one]iron(0)[49,50] (0.430 g, 1.63 mmol, 27 %)
1
(؎)-Tricarbonyl[(1,2,3,4-η)-2,5β-dimethoxy-5α-[4Ј,5Ј-dimethoxy-2Ј-
(triisopropylsilanyloxymethyl)phenyl]-1,3-cyclohexadiene]iron(0)
(13c): Following general procedure C (Variation 2), the aryllithium
reagent formed from [(2-bromo-4,5-dimethoxybenzyl)oxy]triiso-
propylsilane (2.67 g, 6.63 mmol, 2.0 equiv.) and n-butyllithium
(2.0 m in hexanes) (2.0 equiv., 3.31 mL, 6.63 mmol) in diethyl ether
(213 mg, 0.451 mmol, 73%). H NMR (270 MHz, CD3COCD3): δ
3
= 7.52 (t, JH,H = 7.3 Hz, 1 H, 5Ј-H), 7.43 (m, 1 H, 3-H), 7.32 (m,
2 H, 3Ј-H, 6Ј-H), 7.13 (t, 3JH,H = 7.3 Hz, 1 H, 4Ј-H), 6.46 (d, 3JH,H
= 5.9 Hz, 1 H, 2-H), 5.37 (s, 2 H, OCH2), 4.36 (m, 1 H, 5-H), 4.06
3
(s, 3 H, 4-OMe), 3.71 (dd, JH,H = 15.5, 6.6 Hz, 1 H, 6β-H β) 3.48
(s, 3 H, OMe), 3.00 (d, 3JH,H = 15.5 Hz, 1 H, 6α-H) ppm. IR (ace-
1676
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Eur. J. Org. Chem. 2011, 1664–1681