Effective C-O bond cleavage of lignin β-O-4 model compounds：A New RuHCl(CO)(PPh3)3/KOH catalytic
system
Wei Huoa, Wenzhi Lia,*, Minjian Zhanga, Wei Fanb, Hou-min Changc, Hasan Jameelc,
a
Key Laboratory for Biomass Clean Energy of Anhui Province, University of Science and Technology of China, Hefei,
230026, People’s Republic of China.
b
Chemical Engineering, University of Massachusetts, 159 Goessmann Lab, 686 North Pleasant Street, Amherst, MA
01103-3110 (USA)
c
Department of Forest biomaterials, North Carolina State University, Raleigh, NC 27695-8005, USA.
Supporting Information
Table of contents
1. GENERAL EXPERIMENTAL
2. SUBSTRATE PREPARATION
3. REACTION OPTIMIZATION
4. DEGRADATION OF LIGNIN MODEL COMPOUND
1. General Experimental
All experiments with metal complexes were carried out under an atmosphere of purified argon using standard Schlenk
techniques. All deuterated and non-deuterated solvents were reagent grade or better. All reagents were used as received
from commercial suppliers unless otherwise noted. Special attention should be paid on weighing the potassium hydroxide
pellet to ensure the procedure be quickly finished in order to reduce interference from air. Gas chromatography (GC) was
performed on KeXiao GC-1690 gas chromatograph. 1H NMR and 13C NMR spectra were recorded at 400MHz, using a
Bruker AVANCE AV-400 NMR spectrometer. Chemical shifts are reported in ppm downfield from tetramethylsilane. FTIR
spectra were recorded on KBr thin film. Gas chromatography/mass spectrometry (GC-MS) was performed on Agilent
7890A/5975C. RuHCl(CO)(PPh3)3 was prepared according to a literature procedure (S1), the infrared spectrum shows
band at 2013cm-1 (m). 1929 cm-1 (s) and 1910 cm-1 (sh), attributed to ν (CO) and ν (RuH).
2. Substrate Preparation
All reactions were carried out in ovendried glassware. 2-aryloxy-1-phenylethanols 1-5 were prepared in a two-step sequence from the corresponding phenol and 2-bromoacetophenone according to an optimized method of Jason M. Nichols
and co-workers (S2). Compounds 6 was synthesized using modified literature procedures by Adam Wu and co-workers
(S3). Compounds 7 were synthesized using method reported by Julien Buendia and co-workers (S4).
2-phenoxy-1-phenethanol (1)
OH
H NMR (400 MHz, CDCl3) δ 7.50 – 6.89 (m, 10H), 5.13 (dd, J = 8.8, 3.1 Hz, 1H), 4.12 (dd,
J = 9.6, 3.2 Hz, 1H), 4.02 (dd, J = 9.5, 8.9 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 158.47,
139.79, 129.60, 128.60, 128.20, 126.34, 121.36, 114.74, 73.38, 72.63; IR (KBr): 3297 br,
3057 w, 3024 w, 2933 w, 2876 w, 1596 s, 1582 m, 1497 s, 1451 m, 1388 w, 1347 w, 1303 m,
1291 m, 1244 s, 1196 m, 1172 m, 1152 w, 1098 m, 1078 m, 1067 m, 1028 w, 995 w, 918 m, 885 w, 864 m, 792 w, 754 s,
700 s, 691 s, 637 w, 614 w, 592 m, 542 m, 512 m; HRMS (ESI) Exact mass calcd for C14H14O2Na (M+Na)+: 237.08860,
found 237.08826 m/z.
1
O
OH
OMe
O
2-(2-methoxyphenyl)oxy-1-phenethanol (2)
H NMR (400 MHz, CDCl3) δ 7.47 – 7.26 (m, 5H), 7.04 – 6.85 (m, 4H), 5.10 (dd, J = 9.4,
2.8 Hz, 1H), 4.19 (dd, J = 10.1, 2.9 Hz, 1H), 3.98 (t, J = 9.8 Hz, 1H), 3.89 (d, J = 1.0 Hz,
3H), 3.44 (s, 1H); 13C NMR (101 MHz, CDCl3) δ 150.22, 148.08, 139.65, 128.49, 128.00,
1
S1
126.34, 122.55, 121.14, 116.11, 112.16, 76.31, 72.38, 55.90; IR (KBr): 3527 s, 3476 m, 3079 w, 3059 w, 3023 w, 3002 w,
2958 w, 2893 w, 2835 w, 1591 m, 1523 w, 1505 s, 1464 m, 1449 m, 1437 m, 1417 w, 1400 w, 1383 w, 1330 m, 1290 m,
1251 s, 1223 s, 1194 w, 1178 m, 1163 w, 1155 w, 1124 s, 1105 m, 1075 m, 1055 m, 1021 s, 1001 w, 973 w, 955 w, 930 m,
905 w, 861 m, 835 w, 763 s, 739 s, 701 s, 633 m, 598 m, 583 w, 543 m, 525 m; HRMS (ESI) Exact mass calcd for
C15H16O3Na (M+Na)+: 267.09917, found 267.09906 m/z.
OH
2-(2,6-dimethoxyphenyl)oxy-1-phenethanol (3)
OMe
H NMR (400 MHz, CDCl3) δ 7.43 – 7.22 (m, 5H), 7.04 (t, J = 8.4 Hz, 1H), 6.61 (d, J = 8.4
Hz, 2H), 4.96 (dd, J = 9.9, 2.2 Hz, 1H), 4.52 (d, J = 1.3 Hz, 1H), 4.42 (dd, J = 10.9, 2.7 Hz,
1H), 3.89 (s, 6H), 3.72 (dd, J = 10.9, 10.0 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 153.30,
MeO
139.51, 136.87, 128.31, 127.67, 126.31, 124.08, 105.25, 80.03, 72.44, 56.12; IR (KBr): 3501
br, 3098 w, 3056 w, 3022 w, 3005 w, 2972 w, 2936 m, 2881 w, 2844 w, 2835 w, 1597 s, 1498 s, 1477 s, 1464 m, 1446 m,
1435 m, 1412 w, 1363 w, 1329 m, 1296 s, 1254 s, 1273 m, 1209 m, 1173 m, 1151 w, 1113 s, 1092 m, 1081 m, 1062 m, 1030
m, 994 m, 957 w, 915 w, 895 m, 842 w, 775 m, 748 m, 735 m, 699 m, 628 w, 574 w, 538 m, 521 m; HRMS (ESI) Exact
mass calcd for C16H18O4Na (M+Na)+: 297.10973, found 297.10950 m/z.
1
O
2-phenoxy-1-(4-methoxyphenyl)-ethanol (4)
OH
H NMR (400 MHz, CDCl3) δ 7.37 (d, J = 8.7 Hz, 2H), 7.33 – 7.24 (m, 3H), 7.01 – 6.88 (m,
4H), 5.07 (dd, J = 8.8, 3.3 Hz, 1H), 4.11 – 3.95 (m, 2H), 3.81 (s, 3H); 13C NMR (101 MHz,
CDCl3) δ 159.57, 158.54, 132.06, 129.59, 127.62, 121.30, 114.77, 114.04, 73.38, 72.21,55.34;
MeO
IR (KBr): 3330 br, 3073 w, 3039 w, 3013 w, 2998 w, 2958 w, 2934 w, 2837 m, 1612 m, 1598
m, 1584 m, 1515 s, 1450m, 1489 m, 1456 s, 1417 w, 1392 w, 1344 m, 1303 m, 1293 m, 1245 s, 1199 m, 1177 s, 1148 w,
1113 w, 1089 s, 1062 w, 1042 s, 1031 s, 994 w, 966 w, 938 w, 917 m, 885 w, 869 m, 831 m, 808 w, 760 s, 696 s, 638 w, 594
m, 574 w, 546 m, 514 m; HRMS (ESI) Exact mass calcd for C15H16O3Na (M+Na)+: 267.09917, found 267.09921 m/z.
1
O
OH
OMe
2-(2-methoxyphenyl)oxy-1-(3,4-dimethoxyphenyl)-ethanol (5)
H NMR (400 MHz, CDCl3) δ 7.05 – 6.82 (m, 7H), 5.05 (dd, J = 9.3, 2.9 Hz, 1H), 4.17 (dd,
J = 10.1, 3.0 Hz, 1H), 4.02 – 3.85 (m, 10H), 3.40 (s, 1H); 13C NMR (101 MHz, CDCl3) δ
150.16, 149.14, 148.80, 148.10, 132.39, 122.49, 121.11, 118.64, 115.98, 112.10, 111.15,
109.56, 76.28, 72.13, 55.96, 55.89, 55.85; IR (KBr): 3526 s, 3450 m, 3468 m, 3085 w, 3063
MeO
w, 3020 w, 3001 w, 2954 m, 2930 m, 2837 m, 1595 m, 1510 s, 1458 m, 1416 m, 1379 w,
OMe
1347 m, 1335 m, 1313 w, 1297 m, 1267 m, 1253 s, 1229 s, 1183 m, 1153 m, 1128 s, 1088 m,
1059 w, 1040 w, 1023 s, 916 m, 903 m, 861 m, 838 m, 805 m, 784 m, 766 m, 745 s, 647 m, 625 w, 602 w, 576 w, 526 w,
491 w, 440 w, 415 m; HRMS (ESI) Exact mass calcd for C17H20O5Na (M+Na)+: 327.12029, found 327.11990 m/z.
1
O
OH
OMe
1-(4-Hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)ethanol (6)
H NMR (400 MHz, CDCl3) δ 7.05 – 6.86 (m, 7H), 5.60 (s, 1H), 5.03 (dd, J = 9.4, 2.9 Hz,
1H), 4.16 (dd, J = 10.1, 3.0 Hz, 1H), 4.00 – 3.87 (m, 7H), 3.39 (s, 1H); 13C NMR (101 MHz,
CDCl3) δ 150.10, 148.09, 146.72, 145.43, 131.68, 122.44, 121.13, 119.36, 115.85, 114.33,
112.09, 108.93, 76.25, 72.18, 55.93, 55.86; IR (KBr): 3350 br, 3194 br, 3005 w, 2967 w,
HO
2942 w, 2885 w, 2833 w, 1605 m, 1589 m, 1524 m, 1508 s, 1454 m, 1425 w, 1365 w, 1327
OMe
w, 1288 m, 1253 s, 1225 m, 1206 m, 1176 m, 1154 m, 1124 s, 1094 m, 1057 w, 1027 s, 926
w, 913 w, 860 w, 837 w, 821 m, 805 w, 773 w, 752 m, 735 w, 643 w, 610 w, 581 w; HRMS (ESI) Exact mass calcd for
C16H18O5Na (M+Na)+: 313.10464, found 313.10443 m/z.
1
O
OH
OMe
1-(3,4-Dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol (7)
H NMR (400 MHz, CDCl3) δ 7.14 – 7.01 (m, 1H), 7.01 – 6.80 (m, 6H), 4.98 (d, J = 4.4 Hz,
1H), 4.17 (td, J = 5.4, 3.5 Hz, 1H), 4.04 – 3.84 (m, 10H), 3.63 (dd, J = 31.9, 15.2 Hz, 2H),
2.86 (s, 1H); 13C NMR (101 MHz, CDCl3) δ 151.17, 148.91, 148.40, 147.10, 133.18, 123.61,
121.47, 120.00, 118.70, 112.23, 111.07, 109.70, 86.47, 72.80, 60.89, 55.87, 55.83,55.79; IR
HO
MeO
(KBr): 3485 br, 3064 w, 3001 m, 2934 m, 2836 m, 1606 w, 1591 m, 1516 s, 1501 s, 1462 m,
OMe
1440 m, 1418 m, 1326 m, 1256 s, 1236 m, 1177 m, 1157 m, 1140 m, 1124 m, 1081 m, 1025
s, 922 w, 856 w, 811 m, 750 m, 697 w, 651 w, 615 w; HRMS (ESI) Exact mass calcd for C18H22O6Na (M+Na)+: 357.13086,
found 357.13046 m/z.
1
O
S2
3. Reaction Optimization
General Procedure.
The reaction media for Tables S1-S4 were prepared as stock solutions of 2 (976 mg, 4.00 mmol) and 1,2,4,5tetramethylbenzene (268 mg, 2.00 mmol) prepared in a volumetric flask (10.00 mL) using toluene as the diluent. Once
prepared, each individual reaction mixture were taken in a Schlenk flask under an atmosphere of purified argon. The flask
was equipped with a condenser and the solution was refluxed with stirring in an open system under argon for the specified time and allowed to cool to ambient temperature. All samples were analyzed for acetophenone (A) and guaiacol (B)
by GC and quantitated against the internal standard.
Table S1. Variation of ruthenium source.
The reactions were prepared by diluting the ruthenium source (0.02 mmol) and KOH (22.4mg, 0.4 mmol) in Stock solution (2 mL).
OH
O
OMe Ru-source(2.5mol%)
KOH(50mol%)
Entrya
OH
+
toluene(2ml)
125℃
2. 0.8mmol
OMe
O
B
A
Cons.(%)b
Ru-source
Yield(%)b
(2.5mol%)
Time
A
B
(hours)
1
RuHCl(CO)(PPh3)3
95
71
65
48
2
Ru(H)2(CO)(PPh3)3
97
63
16
48
3
RuCl2(PPh3)3
79
57
34
48
4
RuCl2(COD)
82
62
24
48
5
Ru(methallyl)2(COD)
79
56
26
48
6
RuClCp(PPh3)3
54
24
16
48
7
RuH2(PPh3)4
56
22
11
48
8
Ru3(CO12)
56
34
24
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
Table S2. Variation of base.
All individual samples were prepared by diluting RuHCl(CO)(PPh3)3 (19 mg, 0.020 mmol) using Stock solution (2 mL) as
the diluent. The reactions reported in Table S2 were prepared by adding base (0.8 mmol, 100 mol%) to individual sample.
OH
OMe
O
RuHCl(CO)(PPh3)3
(2.5mol%)
Base(100mol%)
toluene(2ml)
125℃
2. 0.8mmol
OMe
O
OH
+
B
A
Entrya
base
Cons.(%)b
Yield(%)b
A
B
(Hours)
1
KOH
97
61
57
36
2
NaOH
92
24
8
36
3
KOtBu
92
41
20
36
4
K2CO3
46
31
27
36
5
NEt3
16
1
1
36
a.Reactions
Time
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
S3
Table S3. Variation of catalyst loading.
The entries in Table S3 were prepared by diluting RuHCl(CO)(PPh3)3 and KOH (22.4 mg, 0.4 mmol) in stock solution
(2.00 mL)as follows: Entry 2 - RuHCl(CO)(PPh3)3 (3.9 mg,4 μmol), Entry 3 - RuHCl(CO)(PPh3)3 (19 mg, 0.02 mmol), Entry
4 - RuHCl(CO)(PPh3)3 (39 mg, 0.04 mmol); Entry 1 - RuHCl(CO)(PPh3)3 (3.9 mg, 4 μmol) in stock solution (4.00 mL).
OH
O
OMe RuHCl(CO)(PPh3)3
(Xmol%)
2. 0.8mmol
Entrya
KOH
toluene(2ml)
125℃
Cat. Loading (mol%)
OMe
O
OH
+
B
A
Cons.(%)b
Yield(%)b
Time
A
B
(Hours)
1
X=0.25
43
31
25
24
2
X=0.5
35
29
18
24
3
X=2.5
74
62
39
24
4
X=5
88
77
47
24
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
Table S4. Variation of KOH loading.
All individual samples were prepared by diluting RuHCl(CO)(PPh3)3 (19mg, 0.020 mmol) using Stock solution (2 mL) as
the diluent. The reactions reported in Table S4 were prepared by adding KOH to individual sample as follows: Entry 1KOH (4.48 mg, 0.08mmol), Entry 2-KOH (13.44 mg, 0.24mmol), Entry 3-KOH (22.4 mg, 0.4mmol), Entry 4-KOH (31.36
mg, 0.56 mmol).
OH
OMe
O
2. 0.8mmol
Entrya
RuHCl(CO)(PPh3)3
(2.5mol%)
KOH(Xmol%)
toluene(2ml)
125℃
KOH
OMe
O
OH
+
B
A
Cons.(%)b
Yield(%)b
Loading (mol%)
Time
A
B
(Hours)
1
X=10
69
29
33
48
2
X=30
94
78
43
48
3
X=50
95
72
26
48
4
X=70
97
61
25
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
4. Degradation of lignin model compound
According to the data received from optimization, we set the reaction condition for research on degradation of lignin
model compounds as RuHCl(CO)(PPh3)3-2.5 mol%, KOH-50 mol%, temperature-125 ℃. In this condition, the reaction
could be conducted in a relatively steady and moderate rate to reduce the interference from possible side reactions in the
late stage, which is beneficial to analyzing the catalytic procedure.
General Procedure.
The reaction media for Tables S5-S10 were prepared as stock solutions of 1-6 (4.00 mmol) and 1,2,4,5tetramethylbenzene (268 mg, 2.00 mmol) prepared in a volumetric flask (10.00 mL) using toluene as the diluent. The reaction media for Table S11 were prepared as stock solutions of 7 (2.00 mmol) and 1,2,4,5-tetramethylbenzene (268 mg,
2.00 mmol) prepared in a volumetric flask (10.00 mL) using toluene as the diluent. Once prepared, each individual reaction mixture were taken in a Schlenk flask with KOH (22.4 mg, 0.4 mmol) under an atmosphere of purified Argon. The
flask was equipped with a condenser and the solution was refluxed with stirring in an open system under argon for the
S4
specified time and allowed to cool to ambient temperature. All samples were analyzed for ketone (A) and phenol (B) by
GC and quantitated against the internal standard.
Table S5. Degradation of 2-phenoxy-1-phenethanol (1)
RuHCl(CO)(PPh3)3
(2.5mol%)
OH
O
KOH(50mol%)
toluene(2ml)
125℃
1. 0.8mmol
Entrya
O
OH
+
A
B
Cons.(%)b
Yield(%)b
Time
A
B
(Hours)
1
99
86
84
12
2
99
77
60
24
3
97
78
60
36
4
98
84
64
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
Table S6. Degradation of 2-(2-methoxyphenyl)oxy-1-phenethanol (2)
OH
RuHCl(CO)(PPh3)3
(2.5mol%)
OMe
O
KOH(50mol%)
toluene(2ml)
125℃
2. 0.8mmol
Entrya
OMe
O
OH
+
B
A
Cons.(%)b
Yield(%)b
Time
A
B
(Hours)
1
50
38
15
12
2
74
62
39
24
3
93
80
75
36
4
95
71
65
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
Table S7. Degradation of 2-(2,6-dimethoxyphenyl)oxy-1-phenethanol (3)
OH
RuHCl(CO)(PPh3)3
(2.5mol%)
OMe
O
KOH(50mol%)
toluene(2ml)
125℃
MeO
3. 0.8mmol
Entrya
OH
O
MeO
OMe
+
B
A
Cons.(%)b
Yield(%)b
Time
A
B
(Hours)
1
39
24
7
12
2
41
30
4
24
3
72
33
7
36
4
72
32
4
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
S5
Table S8. Degradation of 2-phenoxy-1-(4-methoxyphenyl)-ethanol (4)
RuHCl(CO)(PPh3)3
(2.5mol%)
OH
O
4. 0.8mmol
Entrya
+
KOH(50mol%)
toluene(2ml)
125℃
MeO
OH
O
MeO
B
A
Cons.(%)b
Yield(%)b
Time
A
B
(Hours)
1
91
80
77
12
2
91
80
80
24
3
92
80
89
36
4
94
80
85
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
Table S9. Degradation of 2-(2-methoxyphenyl)oxy-1-(3,4-dimethoxyphenyl)-ethanol (5)
OMe
OH
O
KOH(50mol%)
toluene(2ml)
125℃
MeO
OMe
5. 0.8mmol
Entrya
OMe
O
RuHCl(CO)(PPh3)3
(2.5mol%)
OH
+
MeO
OMe
A
Cons.(%)b
B
Yield(%)b
Time
A
B
(Hours)
1
97
40
31
12
2
95
66
45
24
3
99
63
28
36
4
97
61
43
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard.
Table S10. Degradation of 2-(2-methoxyphenyl)oxy-1-(4-hydroxy-3-methoxy) phenethanol (6)
OMe
OH
O
KOH(50mol%)
toluene(2ml)
125℃
HO
OMe
OH
+
HO
OMe
B
A
6. 0.8mmol
Entrya
OMe
O
RuHCl(CO)(PPh3)3
(2.5mol%)
Cons.(%)b
Yield(%)b
Time
A
B
(Hours)
10
12
1
89
NDc
2
89
ND
14
24
3
89
ND
16
36
4
89
ND
19
48
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard. cNot detected.
S6
Table S11. Degradation of 2-(2-methoxyphenoxy)-1-(3,4-dimethoxy)phenyl-1,3-propanediol (7)
OH
O
MeO
O
OMe
HO
OMe
RuHCl(CO)(PPh3)3 (2.5mol%)
KOH(100mol%)
Toluene(2ml)
MeO
125℃
7. 0.4mmol
Entrya
1
2
OMe
+
94
+
O
H
+
MeO
MeO
OMe
OMe
OMe
C
B
A
Cons.(%)b
95
O
OH
Yield(%)b
D
Time
A
B
C
D
(Hours)
4
18
5
Nc
12
7
Nc
24
36
48
6
26
3
89
6
26
8
Nc
4
91
5
53
11
Nc
a.Reactions
were run in a Schlenk flask under an atmosphere of purified argon equipped with condenser. b.Yields and
consumptions were determined by GC relative to an internal standard. c.Minor and not quantitated.
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12555.
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S7