The catalytic activity of Zn(II) and Mn(II) organometallic complexes

Article abstract of DOI:10.1007/s11164-012-0792-6

Zn(II) and Mn(II) organometallic complexes I and II were first used to catalyze the cyanosilylation reaction, and good catalytic results (24-99 %) were achieved. The catalytic activity of the complexes was determined by ¹H NMR.

Full text of DOI:10.1007/s11164-012-0792-6

Res Chem Intermed (2013) 39:2715–2721
DOI 10.1007/s11164-012-0792-6
The catalytic activity of Zn(II) and Mn(II)
organometallic complexes
•
Luo Mei Li Xiao Yan Chen Wei Zhang Jia Hai
•
•
Received: 26 June 2012 / Accepted: 25 August 2012 / Published online: 22 September 2012
Ó Springer Science+Business Media B.V. 2012
Abstract Zn(II) and Mn(II) organometallic complexes I and II were first used to
catalyze the cyanosilylation reaction, and good catalytic results (24–99 %) were
1
achieved. The catalytic activity of the complexes was determined by H NMR.
Keywords Zn(II) and Mn(II) organometallic complexes Á Catalyze Á
The cyanosilylation reaction Á Catalytic activity
Introduction
Organometallic complexes such as Zn(II) and Mn(II) complexes have been widely
used in catalyzing organic and polymer synthesis [1–7]. For example, generation of
geminal dimetallic species of zinc for the Wittig-type olefination, Mn(III) salen
catalysts and their application in asymmetric epoxidation, Mn(III)-salphen complex
for catalytic epoxidation, etc., and they have all shown good catalytic activity
(46–99 % ee) and the yield (60–99 %). Cyanosilylation reactions have attracted
chemists’ interests, because the products, cyanohydrins, are intermediates for the
synthesis of pharmaceuticals. The Shibasaki group, the Corey, Deng, Jacobsen group
and the Feng group [8–18]have devised many excellent catalystsfor this reaction, with
catalytic activity up to 99 % ee and 99 % yield. Encouraged by this pioneer work, our
group has also attempted the Lewis acidic catalysts involving the ethylenediamine
zinc acetate complex and DMFÁMnCl2 complexes in the cyanosilylation reaction.
L. Mei (&) Á L. X. Yan Á C. Wei
Department of Chemical Engineering, Hefei University of Technology, Hefei 230009, China
e-mail: lmhh5523385@yahoo.cn
Z. J. Hai
University of Science and Technology of China, Hefei 230009, China
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L. Mei et al.
Experimental
Materials and instruments
All cyanosilylation reactions were performed using chloroform as solvent, and
reactions were monitored by thin layer chromatography using 0.25 mm Merck silica
gel-coated glass plates (60F-254) and UV light to visualize the course of reaction.
Flash column chromatography was performed using Merck silica gel (60, particle
1
1
size 0.02–0.03 mm). Yield % was obtained by H NMR, while H spectra was
obtained using a Bruker AM-300 spectrometer. The following abbreviations were
used to designate chemical shiftmutiplicities: s = singlet, d = doublet, t = triplet,
m = multiplet. Infrared spectra were recorded on a Mattson Galaxy Series FTIR
3000 Spectrometer. 1,2-ethylenediamine, o-phenylendiamine, Zn(OAc)2Á2H2O,
MnCl2Á4H2O, TMSCN, aldehydes were purchased from Aldrich.
Preparation of 1,2-ethylenediamine zinc complexes I
Amounts of 0.66 mL (0.01 mmol) of 1,2-ethylenediamine, and 2.19 g (0.01 mmol)
of Zn(OAc)2Á2H2O were added under anhydrous and oxygen-free conditions to a
dry 100-mL Schlenk flask. They were dissolved in 15 mL of dry alcohol, and the
reaction mixture was refluxed for 14 h. The solvent was filtrated to give the white
crystals (0.38 g, yield 15 %). m.p.: 78–80 °C, 1H NMR (300 MHz, CDCl3, 27 °C) d
(ppm) = 2.85(s, 4H), 2.43 (s, 6H), 1.96 (s, 4H). IR (KBr): 3,494, 3,103, 2,319,
1,651, 1,647, 1,565, 1,470, 1,428, 1,418, 1,405, 1,377, 1,338, 1,179, 1,025, 978,
932, 727, 684, 616, 600, 509. Elemental analysis: Anal. Calcd. For Zn[C6H14N2O4]:
C, 29.63 %; H, 5.76 %, N, 11.52 %; found, % C: 29.24 %; H: 6.06 %; N: 11.89 %.
Synthesis of complex II
Amounts of 1.4162 g (4.9 mmol) of o-Phenylendiamine and 1.1186 g (10 mmol)
were added to 30 ml THF and 0.9768 g (5 mmol) MnCl2Á4H2O in a dry 100-mL
Schlenk flask. The reaction mixture was refluxed for 24 h. After hot filtration, the
residue was recrystallized from DMF and ether, and colorless crystals were
obtained. m.p.: 110–112 °C; Anal. Calcd. % for C6H14 N2O2MnCl2, C: 26.49; H:
5.19; N: 10.30; found, % C: 26.42; H: 5.493; N: 9.96. IR (KBr, mcm-1): 2,923,
2,810, 1,658, 1,576, 1,496, 1,434, 1,388, 1,250, 1,105, 677.
General procedure of complexes I and II-catalyzed addition of TMSCN
to benzaldehyde
Complexes I and II 0.15 mmol were dissolved in 2 mL toluene, and benzaldehyde
0.1 mL (1 mmol) and TMSCN 0.3 ml (3.3 mmol) were successively added at room
temperature. After 8 h, yield % was obtained by 1H NMR. 1H NMR (300 MHz,
CDCl3) 7.56–7.59 (m, 0.9 Hz, 2H), 7.31–7.34 (m, 3H), 5.43 (s, 1H), 0.16 (s, 9H).
13C NMR (75 MHz, CDCl3) 136.1, 128.8 (92), 126.2 (92), 119.1, 63.5, -0.39
(93).
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The catalytic activity of Zn(II) and Mn(II) organometallic complexes
2717
2-(2-Furyl-phenyl)-2-(trimethylsilyloxy)acetonitrile
OTMS
CN
H
F
Following the procedure described 3, 1H NMR (300 MHz, CDCl3) 7.56–7.57 (m,
0.9 Hz, 1H), 7.29–7.31 (m, 1H), 7.14–7.15 (m, 1H), 6.99–7.03 (m, 1H), 5.69 (s, 1H),
0.16 (s, 9H), yield (%): [99 %, 91 %.
2-(2-Methyloxyphenyl)-2-(trimethylsilyloxy) acetonitrile
OTMS
CN
OCH3
1
Following the procedure described 3, H NMR (300 MHz, CDCl3) 7.52–7.54
(d, J = 7.5 Hz, 1H), 7.20–7.30 (m, 3H), 5.57 (s, 1H), 2.44 (s, 3H), 0.22 (s,9H), yield
(%): [99 %, 85 %.
2-(4-Methylphenyl)-2-(trimethylsilyloxy)acetonitrile
OTMS
CN
H
H3C
Following the procedure described 3,1H NMR (300 MHz, CDCl3) 7.37–7.39 (m,
2H), 7.21–7.24 (m, 2H), 5.48 (s, 1H), 2.38 (s, 3H), 0.24 (s, 9H). 13C NMR (75 MHz,
CDCl3) 139.3, 133.5, 129.6, 126.4, 63.6, 31.6, 22.6, 21.2, 14.1, -0.23 (93), yield
(%): 63 %, 73 %.
2-(4-Methyloxyphenyl)-2-(trimethylsilyloxy)acetonitrile
OTMS
CN
H3CO
Following the procedure described 3, 1H NMR (300 MHz, CDCl3) 7.61–7.63 (m,
1H), 7.37–7.40 (m, 1H), 7.04–7.07 (m, 1H), 6.92–6.94 (m, 1H), 5.82 (s, 1H), 3.91
(s, 3H), 0.25 (s, 9H), yield (%): 84 %, 24 %.
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L. Mei et al.
2-(4-Furylphenyl)-2-(trimethylsilyloxy)acetonitrile
O
H
F
Following the procedure described 3, 1H NMR (300 MHz, CDCl3) 7.40–7.41 (m,
4H), 5.46 (s, 1H), 0.24 (s, 9H), yield (%): 76 %, 49 %.
2-(4-Bromophenyl)-2-(trimethylsilyloxy)acetonitrile
OTMS
CN
Br
Following the procedure described 3, 1H NMR (300 MHz, CDCl3) 7.53–7.55 (m,
2H), 7.33–7.36 (m, 2H), 5.44 (s, 1H), 0.24 (s, 9H), yield (%): 94 %, [99 %.
2-(4-Chlorophenyl)-2-(trimethylsilyloxy)acetonitrile
OTMS
CN
Cl
Following the procedure described 3, 1H NMR (300 MHz, CDCl3) 7.40–7.41 (m,
4H), 5.46 (s, 1H), 0.23 (s, 9H), yield (%): 82 %, 45 %.
a-(Trimethylsilyoxyl)-1-naphthylacetonitrile
OTMS
CN
1
Following the procedure described 3, H NMR (300 MHz, CDCl3) 8.16–8.18
(m, 1H), 7.88–7.91 (m, 2H), 7.69–7.71 (m, 1H), 7.25–7.61 (m, 4H), yield (%):
88 %, 76 %.
Results and discussion
Following treatment of the ligands 1,2-ethylenediamine with Zn(OAc)2Á2H2O in
ethanol, the corresponding complex was obtained after refluxing for 14 h. The
crystals of complex I were obtained.
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The catalytic activity of Zn(II) and Mn(II) organometallic complexes
2719
NH2
H2N
NH2
.
Zn(OAc)2
H2N
2H2O
+
Zn
OAc
AcO
Scheme I The synthetic route to complex I
OCN(CH3)2
(H3C)2NCO
Cl
OCN(CH3)2
Cl
Cl
Mn
Cl
NH2
Cl
Cl
OCN(CH3)2
Mn
DMF/ether
THF
Mn
Cl
Mn
Mn
(H3C)2NCO
2
4H2O
MnCl2
Cl
NH2
OCN(CH3)2
(H3C)2NCO
(H3C)2NCO
Scheme II The synthetic route to complex II
Table 1 The effect of different solventsa
O
OTMS
H
15mol% catalysts
8h
H
CN
+
TMSCN
Solvents
Yield %b (complex I)
Yield %b (complex II)
THF
28
23
96
94
96
68
67
99
5
CH2Cl2
Toluene
Ether
Hexane
a
91
Reactions were carried out with 1 mL PhCHO and 0.3 mL TMSCN in 2 mL CH3OH using 15 mol %
of catalyst I, II and III at room temperature (30–40 °C) for 120 h
b
Yield % was determined by NMR analysis
The complex II was synthesized from the reaction of o-phenylenediamine with
MnCl2Á4H2O, and, unexpectedly, the colorless crystal structure was obtained by
recrystallization of the residue from DMF and ether (Schemes I, II).
In the catalytic process, under the equal condition, if reaction time for 8 h,
different solvents such as ether, toluene, THF, and dichloromethane were attempted
at room temperature, and the results can be seen in Table 1. Because the catalysts
were easily soluble in toluene, and insoluble in ether, toluene was the solvent of best
choice. Then, the scope of the catalysts to cyanosilylation of prochiral aldehydes
was explored (Table 2).
From the Table 2, we got the conclusion as follows:
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L. Mei et al.
Table 2 Cyanosilylation of different aldehydes
O
OTMS
H
15mol% complex I - II
H
CN
+
TMSCN
8h, toluene
R
R
Entry
1
Substrate
Time (h)
8
Yield %a, b (complex I)
Yield %a, b (complex II)
[99
96
O
H
2
4
8
8
[99
91
O
H
F
85
[99
O
H
OCH3
5
6
8
8
73
84
63
24
OTMS
CN
H
H3C
OTMS
CN
H
CO
3
7
8
76
49
O
H
F
8
8
8
8
82
94
88
45
[99
76
O
O
H
Cl
9
H
Br
10
CHO
a
Reactions were carried out with 1 mL PhCHO and 0.3 mL TMSCN in 2 mL toluene using 15 mol % of
catalyst I and II at room temperature (30–40 °C) for 8 h
b
Yield % was determined by NMR analysis
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The catalytic activity of Zn(II) and Mn(II) organometallic complexes
2721
(i) Aldehydes bearing the electron-donor group and electron-withdrawing group
tended to give the lower yield compared with benzaldehyde (entries 1–10,
except entry 2).
(ii) Aldehydes substituted in the ortho-position afforded higher yields than in the
para position substituted aldehydes (entries 2–10, except entry 9)
All in all, no matter what the kind of substituted group, the stereoscopic effect
occupied an important factor in determining the reactivities.
The mechanism can be proposed that the metal ions (Zn2?, Mn2?) could activate
the C=O, affording products with high activity.
Conclusion
In summary, Zn(II) and Mn(II) organometallic complexes I and II were first used to
catalyze the cyanosilylation reaction, and achieved good catalytic results (24–99 %).
Further efforts towards the other catalytic applications of the complexes such as the
Henry reaction, Baylis–Hillman reaction, Allylation reaction, etc.
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