ReactiVity of (2-Alkenyl-3-pentene-1,5-diyl)iron Complexes
210.6, 210.9. FAB-HRMS m/z 486.0508 (calcd for C21H20NO9Fe
(M + H+) m/z 486.0487).
FAB-HRMS m/z 500.0723 (calcd for C22H19N3O7FeLi (M + Li+)
m/z 500.0732).
Cycloaddition of 2i with p-Benzoquinone and Oxidation (14).
A solution of 2i (0.96 g, 3.0 mmol) and p-benzoquinone (648 mg,
6.00 mmol) in CH2Cl2 (5 mL) was heated at reflux, under N2, for
4 h. The reaction mixture evaporated and the residue was purified
by column chromatography (SiO2, hexane-ethyl acetate ) 3:1).
The unstable product was dissolved in dioxane (30 mL) and
activated manganese dioxide (4.0 g, 46 mmol) was added. The
mixture was stirred under nitrogen for 3 h. The reaction mixture
was filtered, the filtrate was evaporated, and the residue was purified
by flash chromatography (SiO2, hexane-ethyl acetate ) 5:1) to
afford 14 as a yellow solid (0.84 g, 66%). 14: mp 125-129 °C; IR
Tricarbonyl[4,5-dihydro-3-methyl-2-[(1,3,4,5-η)-3-pentene-1,5-
diyl]isoxazole]iron (13). To a solution of 2a (292 mg, 1.00 mmol),
nitroethane (143 µL, 1.99 mmol), and phenylisocyanate (218 µL)
in benzene (2 mL) at room temperature was added triethylamine
(278 µL, 2.00 mmol). The reaction mixture was stirred for 48 h,
diluted with water, and extracted several times with ether. The
combined extracts were washed with water, followed by brine, dried
(MgSO4), and concentrated. The residue was purified by column
chromatography (SiO2, hexanes-ethyl acetate ) 3:1) to afford 13
as a yellow oil (224 mg, 64%). This was determined to be a mixture
of two diastereomers (2.4:1) by integration of the signals at δ 0.08
and 0.34 ppm. 13: 1H NMR (CDCl3) δ 0.08 (d, J ) 9.0 Hz, 0.7H),
0.34 (d, J ) 9.3 Hz, 0.3H), 1.87 (s, 0.9H), 1.94 (s, 2.1 H),
2.30-2.42 (m, 1H), 2.59-2.81 (m, 2H), 3.23 (q, J ) 8.4 Hz) and
3.23-3.30 (m, 1H total), 3.60-3.70 (m and s, 4H total), 3.87 (ddd,
J ) 6.8, 8.7, 10.0 Hz, 0.7 H), 4.06-4.16 (m, 0.3H), 4.35 (br t, J
) 7.2 Hz, 0.3H), 4.51 (br t, J ) 7.2 Hz, 0.7 H), 4.59-4.70 (m,
1H); 13C NMR (CDCl3) δ 8.6 [8.7], 13.3 [13.2], 40.5 [40.8], 43.4
[43.9], 51.7, 55.3 [55.9], 63.0 [62.5], 84.6 [83.0], 99.0 [99.6], 180.6,
203.7, 210.2, 210.5 (diastereomeric signals in square brackets).
Tricarbonyl[2-(1′-methylene-2-propenyl)-3-pentene-1,5-
diyl]iron (2i). In a round-bottomed flask, under N2, was added
magnesium turnings (1.15 g, 47.3 mmol), 1,2-dibromoethane (0.4
mL), and THF (0.7 mL), followed by a solution of ZnCl2 (0.21 g
1.5 mmol) in THF (17 mL). To this mixture was added dropwise,
over a 40 min period, a solution of 2-chloro-1,3-butadiene (5.68 g,
50% in toluene, 32.1 mmol) and 1,2-dibromoethane (0.7 mL) in
THF (10 mL), during which time the reaction temperature was kept
between 25 and 35 °C. After the addition, the reaction mixture was
heated at reflux for 1 h and then cooled to room temperature. To
a solution of 1 (6.56 g, 16.0 mmol) in anhydrous CH2Cl2, at -70
°C under N2, was added the above prepared solution of 2-(1,3-
butadienyl)magnesium chloride in THF. The reaction mixture was
stirred for 1 h, and then quenched with saturated aqueous NH4Cl
(240 mL) and warmed to room temperature. The layers were
separated and the aqueous layer extracted several times with
CH2Cl2. The combined organic phases were dried (MgSO4), filtered
through a short bed of SiO2, and concentrated. Immediate column
chromatography (SiO2, hexane-ethyl acetate ) 35:1) afforded 2i
as an orange oil that crystallizes upon cooling (3.20 g, 63%). 2i:
mp 51-53 °C; 1H NMR (CDCl3) δ 0.28 (d, J ) 8.7 Hz, 1H), 2.34
(dd, J ) 1.9, 12.3 Hz, 1H), 3.50 (br d, J ) 6.9 Hz, 1H), 3.72 (s,
3H), 4.03 (br t, J ) 8.1 Hz, 1H), 4.50 (t, J ) 7.2 Hz, 1H), 4.78
(ddd, J ) 6.9, 7.8, 11.7 Hz, 1H), 4.89 (s, 1H), 4.98 (s, 1H), 5.02
(d, J ) 11.2 Hz, 1H), 5.29 (d, J ) 17.9 Hz, 1H), 6.09 (dd, J )
11.2, 17.9 Hz, 1H); 13C NMR (CDCl3) δ 13.1, 40.5, 51.6, 54.1,
63.3, 98.1, 114.4, 115.3, 136.1, 148.7, 181.0, 204.2, 210.3, 210.9.
Anal. Calcd for C14H14FeO5 ·2/3H2O: C, 51.89; H, 4.56 Found: C,
51.96; H, 4.45.
1
(KBr) 2925, 2069, 2005, 1994, 1686, 1668, 1596, 1163 cm-1; H
NMR (400 MHz, CDCl3) δ 0.50 (d, J ) 8.8 Hz, 1H), 2.23 (br d,
J ) 11.6 Hz, 1H), 3.60 (br d, J ) 7.6 Hz, 1H), 3.79 (s, 3H), 4.61
(t, J ) 7.6 Hz, 1H), 4.75 (t, J ) 7.0 Hz, 1H), 4.90-4.98 (m, 1H),
6.95 (s, 2H), 7.40 (br d, J ) 7.6 Hz, 1H), 7.78 (br s, 1H), 7.95 (d,
J ) 8.0 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 14.7, 43.2, 52.0,
55.0, 62.3, 99.1, 123.1, 127.1, 130.2, 131.3, 132.0, 138.7, 138.9,
152.2, 180.5, 184.9, 185.2, 203.6, 210.0, 210.3. Anal. Calcd for
C20H14O7Fe: C, 56.90; H, 3.31. Found: C, 57.00; H, 3.53.
Cycloaddition of 2i with DMAD and Oxidation (15). A solution
of 2i (322 mg, 1.01 mmol) in dimethyl acetylenedicarboxylate (142
mg, 1.0 mmol) was stirred at room temperature for 24 h. After
evaporation of the DMAD, the residue was purified by column
chromatography (SiO2, hexane-ethyl acetate ) 5:1) to give a
yellow solid. The solid (345 mg, 0.75 mmol) thus obtained was
dissolved in dioxane (20 mL) and activated manganese dioxide (1.30
g, 14.9 mmol) was added. The mixture was stirred at room
temperature for 3 h and filtered, tehn the filtrate was evaporated.
The residue was purified by flash chromatography (SiO2, hexane-
ethyl acetate ) 3:1) to give 15 as a light yellow solid (120 mg,
26%). 15: mp 102-104 °C; IR (KBr) 2925, 2068, 2005, 1988, 1738,
1722, 1686, 1436, 1289, 1165 cm-1; 1H NMR (400 MHz, CDCl3)
δ 0.46 (d, J ) 9.2 Hz, 1H), 2.24 (dd, J ) 2.0, 12.4 Hz, 1H), 3.58
(ddd, J ) 1.4, 2.6, 8.6 Hz, 1H), 3.76, 3.88 and 3.90 (3 × s, 9H
total), 4.53 (t, J ) 8.0 Hz, 1H), 4.70 (t, J ) 7.2 Hz, 1H), 4.88
(ddd, J ) 6.8, 8.4, 12.0 Hz, 1H), 7.19 (d, J ) 1.2, 7.6 Hz, 1H),
7.32 (d, J ) 1.2 Hz, 1H), 7.64 (d, J ) 7.6 Hz, 1H); 13C NMR
(CDCl3) δ 14.8, 42.9, 51.9, 52.8, 52.9, 55.0, 62.5, 99.0, 125.7, 128.1,
129.1, 129.6, 133.0, 149.5, 167.6, 168.7, 180.6, 203.7, 210.1, 210.4.
Anal. Calcd for C20H18O9Fe: C, 52.42; H, 3.96. Found: C, 52.42;
H, 4.02.
(1S*,2R*,3R*,4R*)-5,5-Dichloro-1-methoxycarbonyl-2-vinylbi-
cyclopropane (16). To a solution of 9 (400 mg, 1.07 mmol) in
methanol (13 mL) at room temperature was added portionwise ceric
ammonium nitrate (4.1 g, 7.5 mmol) over a period of 10 min. The
mixture was stirred for an additional 10 min and then poured into
brine and extracted several times with ethyl acetate. The combined
organic extracts were washed with water, followed by saturated
aqueous NaHCO3 and brine, dried (MgSO4), and concentrated under
reduced pressure to give 16 as a colorless syrup (250 mg, 1.06
Cycloaddition of 2i with PTAD (2j). To a solution of 2i (160
mg, 0.503 mmol) dissolved in a minimal amount of ethyl acetate/
hexane (1:1, ca. 0.3 mL) was added dropwise a solution of 4-phenyl-
1,2,4-triazoline-3,5-dione [PTAD] dissolved in a minimal amount
of ethyl acetate/hexane until the red color of the PTAD persisted.
The mixture was stirred for an additional 30 min. Gaseous 1,3-
butadiene was bubbled through the reaction mixture to react with
the excess PTAD. The reaction mixture was evaporated and the
residue was purified by column chromatography (SiO2, hexane-ethyl
acetate ) 1:1) to give 2j as a light yellow solid (210 mg, 85%). 2j:
mp 170-172 °C; IR (KBr) 2925, 2064, 1990, 1772, 1712, 1503,
1
mmol, 99%). 16: H NMR (300 MHz, CDCl3) δ 1.28-1.42 (m,
2H), 1.52 (td, J ) 4.5, 8,1 Hz, 1H), 1.70 (dd, J ) 6.1, 9.4 Hz, 1H),
1.90 (t, J ) 4.8 Hz, 1H), 2.26 (br dt, J ) 4.8, 8.1 Hz, 1H), 3.74 (s,
3H), 5.19 (br d, J ) 10.2 Hz, 1H), 5.29 (br d, J ) 17.1 Hz, 1H),
5.63 (ddd, J ) 8.1, 10.2, 17.1 Hz, 1H); 13C NMR (75 MHz, CDCl3)
δ 27.3, 27.5, 28.3, 29.0, 29.8, 52.2, 60.7, 118.4, 133.6, 173.0. Anal.
Calcd for C10H12O2Cl2 ·0.3H2O: C, 49.94; H, 5.28. Found: C, 49.90;
H, 5.16.
(1S*,2R*,3R*,4S*,6R*)-6-Hydroxymethyl-1-methyloxycarbonyl-
2-vinylbicyclopropane (17). The decomplexation of 11 (690 mg,
2.05 mmol) with CAN (12.8 mmol) in methanol (24 mL) was
carried out in a fashion similar to the decomplexation of 9, to give
17 as a colorless syrup (324 mg, 1.65 mmol, 80%). 17: IR (CH2Cl2)
1
1418, 1169, 766, 611 cm-1; H NMR (300 MHz, CDCl3) δ 0.32
(d, J ) 8.4 Hz, 1H), 2.35 (dd, J ) 2.3, 12.1 Hz, 1H), 3.62 (br d,
J ) 8.1 Hz, 1H), 3.73 (s, 3H), 3.88-3.94 (m, 2H), 4.08-4.13 (m,
3H), 4.43 (t, J ) 7.2 Hz, 1H), 4.83 (ddd, J ) 7.1, 8.1, 12.0 Hz,
1H), 5.52 (br s, 1H), 7.36-7.50 (m, 5H); 13C NMR (75 MHz,
CDCl3) δ 12.1, 42.3, 43.4, 52.0, 54.8, 60.9, 99.2, 114.0, 125.6,
128.4, 129.4, 131.3, 135.9, 152.4, 152.6, 180.3, 203.6, 209.9, 210.2.
1
1726 cm-1; H NMR (300 MHz, CDCl3) δ 0.49-0.62 (m, 3H),
1.03-1.14 (m, 1H), 1.45 (td, J ) 4.8, 9.3 Hz, 1H), 1.58 (br s,
OH), 1.61 (t, J ) 4.5 Hz, 1H), 2.18 (dt, J ) 4.4, 9.0 Hz, 1H), 3.40
J. Org. Chem. Vol. 73, No. 18, 2008 7243