Enantioselective C-H carbene insertions with homogeneous ... · Enantioselective C-H carbene...
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SUPPORTING INFORMATION
Enantioselective C-H carbene insertions with homogeneous and immobilized copper complexes.
José M. Fraile,* Pilar López-Ram-de-Viu, José A. Mayoral, Marta Roldán, and Jorge Santafé-Valero.
Departamento de Química Orgánica, Instituto de Ciencia de Materiales de Aragón and Instituto Universitario de
Catálisis Homogénea, Facultad de Ciencias, Universidad de Zaragoza-C.S.I.C., E-50009 Zaragoza, Spain
Content Page
General ....................................................................................................................... 2
Catalytic tests ............................................................................................................. 3
Analysis of the insertion reactions
THF ................................................................................................................ 4
THP ................................................................................................................ 10
1,4-Dioxane ................................................................................................... 15
1,3-Dioxolane ................................................................................................. 20
Diisopropylether ............................................................................................. 22
Semi-preparative HPLC .............................................................................................. 24
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General
Laponite was obtained from Laporte Adsorbents. Bis(oxazoline) ligand 1a was prepared
by condensation of (S)-phenylglycinol with dimethylmalononitrile.1,2 Azabis(oxazoline) ligand 2a
was prepared from (S)-2-amino-4-phenyl-4,5-dihydro-1,3-oxazole and (S)-2-ethoxy-4-phenyl-
4,5-dihydro-1,3-oxazole.3 Azabis(oxazoline) ligands 2b and 2c were prepared from (S)-2-amino-
4-tert-butyl-4,5-dihydro-1,3-oxazole and (S)-2-amino-4-isopropyl-4,5-dihydro-1,3-oxazole
respectively.2,4 Methyl phenyldiazoacetate was prepared by reaction of methyl phenylacetate
with p-acetamidobenzenesulfonylazide.5
Products were identified by NMR spectroscopy (Bruker Avance 400), mass
spectrometry (ESI, Bruker MicroToF-Q), and polarimetry (Jasco J-810 polarimeter). Analysis
were carried out by GC (Hewlett-Packard 5890 Series II, FID) or HPLC (Waters Allience 2690
with PDA 2996 detector).
Preparation of laponite-immobilized catalysts:6 Laponite (1 g) was dried under vacuum
for 24 h prior to use. The chiral ligand (0.37 mmol) and Cu(OTf)2 (115.7 mg, 0.32 mmol) were
dissolved in the minimum required amount of anhydrous dichloromethane under argon
atmosphere, the solution was stirred for 15 min and filtered through a PTFE microfilter. The
solvent was eliminated under vacuum, the complex was re-dissolved in methanol (5.5 mL),
laponite was added and the suspension was stirred for 24 h at room temperature. The solid was
filtered off, washed with methanol (14 ml) and dichloromethane (20 ml), and finally dried under
vacuum for 24 h. Catalysts were characterized by copper analysis (plasma emission
spectroscopy on a Perkin-Elmer Plasma 40 emission spectrometer), elemental analysis (Perkin-
Elmer 2400 elemental analyzer), X ray diffraction of oriented (D-max Rigaku system with
rotating anode), and transmission FTIR (self-supported wafers evacuated at < 10–4 Torr and
50°C in a Nicolet Avatar 360 spectrometer).
1 A. Cornejo, J. M. Fraile, J. I. García, M. J. Gil, V. Martínez-Merino, J. A. Mayoral, E. Pires, I. Villalba, Synlett 2005, 2321. 2 J. M. Fraile, J. I. García, J. A. Mayoral, M. Roldán, Org. Lett. 2007, 9, 731 (supplementary material). 3 J. M. Fraile, J. I. García, C. I. Herrerías, J. A. Mayoral, O. Reiser, A. Socuéllamos, H. Werner, Chem. Eur. J. 2004, 10, 2997. 4 M. Glos, O. Reiser, Org. Lett. 2000, 2, 2045. 5 W. A. J.; Starmans, L. Thijs, B. Zwanenburg, Tetrahedron, 1998, 54, 629. 6 Modification of the method described in ref. 3.
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Catalytic tests
Homogeneous insertion reaction
The catalyst was prepared with the corresponding ligand (0.025 mmol) and Cu(OTf)2
(0.02 mmol) in anhydrous CH2Cl2 (0.5 mL) under an inert atmosphere. The mixture was stirred
for 30 min, the solution was microfiltered and the solvent removed under an inert gas stream.
This complex was dissolved in anhydrous substrate (THF, THP, 1,4-dioxane, 1,3-dioxolane, or
diisopropylether, 10 mL), n-decane (100 mg) was added as an internal standard and the
solution heated under reflux. A solution of methyl phenyldiazoacetate (1 mmol) in anhydrous
substrate (10 mL) was slowly added during 2 h with a syringe pump. Once the addition had
finished, the reaction mixture was stirred and heated under reflux for 30 min. The yield and
diastereoselectivity were determined by GC.
Heterogeneous insertion reactions
A suspension of dried heterogeneous catalyst (100 mg) in anhydrous substrate (10 mL)
with n-decane (100 mg) as internal standard was heated under reflux under an inert
atmosphere. A solution of methyl phenyldiazoacetate (1 mmol) in anhydrous substrate (10 mL)
was slowly added during 2 h with a syringe pump.
Once the addition had finished, the reaction mixture was stirred and heated under reflux
for 30 min. The catalyst was filtered off and washed with substrate (5 mL). The yield and
diastereoselectivity were determined by GC. The catalyst was dried under vacuum and reused
under the same conditions.
Alternatively, the catalyst was suspended in a mixture of THF (2 mmol) and n-decane
(10 mg) in anhydrous hexane (10 mL). The suspension was heated under reflux under an inert
atmosphere and a solution of methyl phenyldiazoacetate (1 mmol) in anhydrous hexane (10
mL) was slowly added during 2 h with a syringe pump. The reaction was then treated and
analyzed as described above.
Isotopic effect
The catalyst was added to a solution of THF (2 mmol) and d8-THF (2 mmol) in
anhydrous hexane (10 mL). The mixture was heated under reflux under an inert atmosphere
and a solution of methyl phenyldiazoacetate (1 mmol) in anhydrous hexane (10 mL) was slowly
added during 2 h with a syringe pump. The deuterated/non-deuterated products ratio was
determined by GC: HP-Innowax 30 m column; pressure 20 psi (He as carrier gas); oven
temperature program: 60 ºC (3 min) – 1 ºC/min – 200 ºC (20 min); retention times: unlike d8-
products 110.7 min, unlike products 111.2 min, like d8-products 111.5 min, like products 111.9
min. The final non-deuterated/deuterated products ratio was confirmed by NMR.
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Analysis of the insertion reactions
THF
GC: 30 m phenylsilicone column; pressure 20 psi (He as carrier gas); oven temperature
program: 120 ºC (3 min) – 3 ºC/min – 200 ºC (5 min); retention times: n-decane 2.4 min, methyl
phenyldiazoacetate 7.7 min, unlike products (3) 16.9 min, like products (4) 17.1 min.
Enantioselectivities were determined by HPLC. Column: Chiralcel OD-H; 0.46 cm × 25 cm.
Eluent: hexane/isopropanol (99.4/0.6), 0.8 mL/min. Retention times: 3S (2R,S) 16.7 min, 3R
(2S,R) 20.0 min, like product (enantiomer 1) 24.6 min, like product (enantiomer 2) 26.9 min.
Methyl (2R*,S*)--(oxolan-2-yl)phenylacetate (unlike isomers, 3): 1H NMR (400 MHz, CDCl3):
7.29-7.39 (m, 5H), 4.46 (dt, 1H, J = 7.1, J = 8.3 Hz, H2), 3.81 (dt, 1H, J = 6.8, J = 8.2 Hz, H5),
3.71 (dt, 1H, J = 6.9, J = 8.1 Hz, H5’), 3.67 (s, 3H), 3.63 (d, 1H, J = 8.6 Hz, H), 2.12 (m, 1H,
H3), 1.87 (m, 2H, H4), 1.67 (m, 1H, H3’); 13C NMR (100 MHz, CDCl3): 172.6, 136.6, 128.6,
128.5, 127.5, 80.0 (C2), 68.4 (C5), 56.9 (C), 52.0 (OCH3), 30.2 (C3), 25.7 (C4). HRMS (ESI),
found: 243.0980 (MNa+); calcd for C13H16O3Na: 243.0992; Anal. calc. for C13H16O3: C,70.91; H,
7.27. Found: C, 70.88; H, 7.30. 5S (2R,S) −88.1° (c 0.159, CHCl3).7 3R (2S,R)
+78.1º (c 0.167, CHCl3).
7 Value reported in the literature: −74º (c 0.2, CHCl3). Davies, H. M. L.; Hansen, T.; Churchill, M. R. J. Am. Chem. Soc. 2000, 122, 3063–3070.
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OCOOMe
Ph2
3
34
5
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OCOOMe
Ph2
3
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Methyl (2R*,R*)--(oxolan-2-yl)phenylacetate (like isomers, 4): 1H NMR (400 MHz, CDCl3):
7.34-7.26 (m, 5H), 4.52 (dt, 1H, J = 7.0, J = 10.0 Hz, H2), 3.92 (dt, 1H, J = 7.0, J = 8.3 Hz, H5),
3.85 (dt, 1H, J = 6.2, J = 8.2 Hz, H5’), 3.70 (s, 3H), 3.53 (d, 1H, J = 10.0 Hz, H), 1.86 (m, 2H,
H4), 1.69 (m, 1H, H3), 1.44 (m, 1H, H3’); 13C NMR (100 MHz, CDCl3): 173.1, 136.0, 128.8,
128.5, 127.8, 80.7 (C2), 68.6 (C5), 57.7 (C), 52.2 (OCH3), 29.7 (C3), 25.6 (C4). HRMS (ESI),
found: 243.0974 (MNa+); calcd for C13H16O3Na: 243.0992. Enantiomer 1 −19.3° (c 0.7,
CHCl3). Enantiomer 2 +18.6º (c 0.7, CHCl3).
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OCOOMe
Ph2
4
34
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OCOOMe
Ph2
4
34
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OCOOMe
Ph2
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THP
GC: 30 m phenylsilicone column; pressure 20 psi (He as carrier gas); oven temperature
program: 120 ºC (3 min) – 3 ºC/min – 200 ºC (5 min); retention times: n-decane 2.4 min, methyl
phenyldiazoacetate 7.7 min, unlike products (5) 18.9 min, like products (6) 19.1 min.
Enantioselectivities were determined by GC. Column: Cyclodex-, 30 m. pressure 20 psi (He as
carrier gas); oven temperature program: 125 ºC (180 min). Retention times: 5S (2R,S) 162.7
min, 5R (2S,R) 165.2 min, 6 (enantiomer 1) 169.0 min, 6 (enantiomer 2) 172.9 min.
Methyl (2R*,S*)--(oxan-2-yl)phenylacetate (unlike isomers, 5): 1H NMR (400 MHz, CDCl3):
7.25-7.39 (m, 5H), 3.87-3.92 (m, 2H, H2+H6), 3.65 (s, 3H), 3.64 (d, 1H, J = 9.1 Hz, H), 3.34
(dt, 1H, J = 2.7, J = 11.4 Hz, H6’), 1.84 (m, 1H), 1.71 (m, 1H), 1.43-1.58 (m, 3H), 1.30-1.42 (m,
1H); 13C NMR (100 MHz, CDCl3): 172.6, 135.2, 128.9, 128.5, 127.5, 78.6 (C2), 69.0 (C6), 57.7
(C), 52.0 (OCH3), 29.8, 25.8, 23.3. HRMS (ESI), found: 257.1125 (MNa+); calcd for
C14H18O3Na: 257.1154. 7S (2R,S) −76.4° (c 0.55, CCl4). 5R (2S,R) +78.2º (c 0.75,
CCl4).
2
5COOMe
Ph
O
34
5
6
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2
5COOMe
Ph
O
34
5
6
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Methyl (2S*,S*)--(oxan-2-yl)phenylacetate (like isomers, 6, not fully purified): 1H NMR (400
MHz, CDCl3): 7.25-7.38 (m, 5H), 4.01 (m, 1H, H6), 3.91 (dt, 1H, J = 2.1, J = 10.7 Hz, H2), 3.68
(s, 3H), 3.54 (d, 1H, J = 10.1 Hz, H), 3.49 (dt, 1H, J = 2.7, J = 11.7 Hz, H6’), 1.8-2.0 (m, 6H); 13C NMR (100 MHz, CDCl3): 172.5, 135.4, 128.8, 128.5, 127.9, 79.5 (C2), 68.9 (C6), 58.4 (C),
52.2 (OCH3), 29.2, 25.9, 23.3.
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COOMe
Ph2
6
O
34
5
6
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COOMe
Ph2
6
O
34
5
6
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1,4-Dioxane
GC: 30 m phenylsilicone column; pressure 20 psi (He as carrier gas); oven temperature
program: 120 ºC (3 min) – 3 ºC/min – 200 ºC (5 min); retention times: n-decane 2.4 min, methyl
phenyldiazoacetate 7.7 min, like products (7) 19.7 min, unlike products (8) 19.8 min.
Enantioselectivities were determined by GC. Column: Cyclodex-, 30 m. pressure 20 psi (He as
carrier gas); oven temperature program: 110 ºC (240 min). Retention times: 7 (enantiomer 1)
213.1 min, 7 (enantiomer 2) 219.1 min, 8 (enantiomer 1) 224.1 min, 8 (enantiomer 2) 228.0 min.
Methyl (2S*,S*)--(1,4-dioxan-2-yl)phenylacetate (like isomers, 7): 1H NMR (400 MHz, CDCl3):
7.28-7.35 (m, 5H), 4.18 (dt, 1H, J = 7.1, J = 9.2 Hz, H2), 3.87 (dd, 1H, J = 2.4, J = 11.4 Hz, H3),
3.69-3.75 (m, 2H), 3.68 (d, 1H, J = 9.0 Hz, H), 3.66 (s, 3H), 3.57-3.65 (m, 2H), 3.44 (dd, 1H, J
= 9.4, J = 11.3 Hz, H3’); 13C NMR (100 MHz, CDCl3): 171.7, 135.3, 128.9, 128.7, 127.8, 75.8
(C2), 69.7 (C3), 67.0, 66.5, 53.7 (C), 52.4 (OCH3). HRMS (ESI), found: 259.0916 (MNa+);
calcd for C13H16O4Na: 259.0946.
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4550556065707580859095100105110115120125130135140145150155160165170175f1 (ppm)
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
52.3
753
.73
66.5
267
.05
69.6
975
.83
76.8
477
.16
77.4
8
127.
8512
8.73
128.
87
135.
30
171.
73
Methyl (2R*,S*)--(1,4-dioxan-2-yl)phenylacetate (unlike isomers, 8): 1H NMR (400 MHz,
CDCl3): 7.27-7.34 (m, 5H), 4.23 (dt, 1H, J = 2.6, J = 10.0 Hz, H2), 3.75-3.85 (m, 2H), 3.70 (s,
3H), 3.60 (d, 1H, J = 10.4 Hz, H), 3.55-3.67 (m, 2H), 3.34 (dd, 1H, J = 2.6, J = 11.6 Hz, H3),
3.19 (dd, 1H, J = 9.8, J = 11.6 Hz, H3’); 13C NMR (100 MHz, CDCl3): 172.5, 133.9, 129.1, 128.5,
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128.3, 76.4 (C2), 69.3 (C3), 67.0, 66.5, 54.6 (C), 52.4 (OCH3). HRMS (ESI), found: 259.0930
(MNa+); calcd for C13H16O4Na: 259.0946.
2
8
COOMe
PhO
O
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6
2
8
COOMe
PhO
O
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6
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2
8
COOMe
PhO
O
35
6
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1,3-Dioxolane
O
O
+
Ph COOMe
N2
O
OCOOMe
PhO
OCOOMe
PhRS
9S 9R
GC: 30 m phenylsilicone column; pressure 20 psi (He as carrier gas); oven temperature
program: 120 ºC (3 min) – 3 ºC/min – 200 ºC (5 min); retention times: n-decane 2.4 min, methyl
phenyldiazoacetate 7.7 min, products 9 16.7 min.
Enantioselectivities were determined by GC. Column: Cyclodex-, 30 m. pressure 20 psi (He as
carrier gas); oven temperature program: 150 ºC (30 min). Retention times: 9 (enantiomer 1)
21.0 min, 9 (enantiomer 2) 21.9 min.
Methyl -(1,3-dioxolan-2-yl)phenylacetate (9): 1H NMR (400 MHz, CDCl3): 7.29-7.39 (m, 5H),
5.48 (d, 1H, J = 7.1 Hz, H2), 3.90-3.97 (m, 3H), 3.82-3.88 (m, 1H), 3.75 (d, 1H, J = 7.1 Hz, H),
3.72 (s, 3H); 13C NMR (100 MHz, CDCl3): 171.3, 134.2, 128.9, 128.8, 128.1, 104.6 (C2), 65.4
(C3+C4), 56.6 (C), 52.4 (OCH3). HRMS (ESI), found: 245.0782 (MNa+); calcd for C12H14O4Na:
245.0790.
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O
OCOOMe
Ph
9
2
4
5
O
OCOOMe
Ph
9
2
4
5
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1.95
0.57
1.00
0.27
3.71
3.86
4.74
4.89
OO O
n
+
O
O4.89 ppm
3.86 ppm
4.74 ppm
3.71 ppm
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Diisopropylether
GC: 30 m phenylsilicone column; pressure 20 psi (He as carrier gas); oven temperature
program: 120 ºC (3 min) – 3 ºC/min – 200 ºC (5 min); retention times: n-decane 2.4 min, methyl
phenyldiazoacetate 7.7 min, products 10 8.8 min.
Enantioselectivities were determined by HPLC. Column: Chiralcel IA; 0.46 cm × 25 cm. Eluent:
hexane/chloroform (95/5), 0.5 mL/min. Retention times: 10 (enantiomer 1) 17.4 min, 10
(enantiomer 2) 19.6 min.
Methyl -(isopropoxy)phenylacetate (10): 1H NMR (400 MHz, CDCl3): 7.45 (m, 2H), 7.34 (m,
3H), 5.00 (s, 1H, H), 3.71 (s, 3H), 3.67 (m, 1H, OCHMe2), 1.25 (d, 3H, J = 6.1 Hz), 1.20 (d, 3H,
J = 6.1 Hz); 13C NMR (100 MHz, CDCl3): 172.1, 137.4, 128.7, 128.6, 127.3, 78.6 (C), 71.1
(OCHMe2), 52.4 (OCH3), 22.3, 22.1.
7.22
3.99
1.00
2.91
1.95
1.19
1.21
1.24
1.26
3.66
3.67
3.69
3.71
5.00
7.33
7.34
7.36
7.45
7.45
7.47
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22.0
922
.30
52.3
6
71.0
676
.84
77.1
677
.48
78.6
1
127.
2612
8.61
128.
69
137.
36
172.
10
Ph COOMe
O 10
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Semi-preparative HPLC
Resolution of steroisomers by semi-preparative HPLC was carried out from racemic
mixtures obtained by reaction of methyl phenyldiazoacetate with THF or THP catalyzed by
Rh2(OAc)4.8
THF
The crude was purified by column chromatography on silica gel using n-hexane/diethyl
ether (7/3) as an eluent, allowing isolation of 3 and a mixture 3+4. Two semi-preparative HPLC
resolutions were carried out using a a 250 × 20 mm ID Chiralpak® IB column and a mixture n-
hexane/2-propanol (99.5/0.5) as mobile phase at a flow rate of 16 mL/min. 130 mg of racemic 3
were dissolved in 1.4 mL of n-hexane/2-propanol (99.5/0.5) and introduced into the column by
successive injections of 0.1 mL (every 30 minutes). Three separate fractions were collected. 3S
(38 mg) and 3R (36 mg) were obtained in enantiopure form in fractions 1 and 3 respectively.
The mixture of stereoisomers 3+4 (400 mg) was dissolved in 2 mL of the same mixture of
solvents and introduced into the column by successive injections of 0.1 mL (every 30 min).
Seven fractions were collected, and both enantiomers of 4 were obtained from the fifth (20 mg)
and seventh (10 mg) fractions.
(2R,S)-3S: −88.1 (c 0.159, CHCl3).
(2S,R)-3R: +78.1 (c 0.167, CHCl3).
First eluted like enantiomer 4: −19.3 (c 0.7, CHCl3).
Second eluted like enantiomer 4: +18.6 (c 0.7, CHCl3).
THP
The crude was purified by column chromatography on silica gel using n-hexane/ethyl
acetate (9/1) as an eluent, allowing isolation of 5 and a mixture 5+6. Two semi-preparative
HPLC resolutions were carried out using a 250 × 20 mm ID Chiralpak® IA column and a mixture
n-hexane/ethanol (99.8/0.2) as mobile phase at a flow rate of 16 mL/min. 90 mg of racemic 5
were dissolved in 0.9 mL of n-hexane/ethanol (1/1) and introduced into the column by
successive injections of 0.1 mL (every 12 minutes). Three separate fractions were collected. 5S
(20 mg) and 5R (30 mg) (tentatively assigned) were obtained in enantiopure form in fractions 1
and 3 respectively. The mixture of stereoisomers 5+6 (70 mg) was dissolved in 1.5 mL of n-
hexane/ethanol (1/1) and introduced into the column by successive injections of 0.1 mL (every
32 minutes). Seven fractions were collected but it was not possible to separate both
enantiomers of 6. Only in the seventh fraction 5 mg of a 5/95 mixture of both enantiomers were
obtained.
(2R,S)-5S: −76.4 (c 0.55, CCl4).
(2S,R)-5R: +78.2 (c 0.75, CCl4).
8 Reaction conditions: 0.086 mmol Rh2(OAc)4, 40 mL THF (or THP) under reflux, slow addition of a solution of methyl phenyldiazoacetate (4 mmol) in 20 mL THF (or THP).
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