Synthesis and asymmetric catalytic activities of chiral organogallium and indium complexes with ephedrine derivatives as ligands. The crystal structure of [(1 R, 2S)-(Me2Ga-μ-OCH (C6H5)CH(CH3)-μ- NHCH3)]2

Article abstract of DOI:10.1016/S0022-328X(03)00710-1

Reactions of trimethylgallium or trimethylindium with (1R, 2S)-(-)-ephedrine derivatives afford compounds [(1R, 2S)-(Me₂E-μ-OCH(C₆H₅) CH(CH₃)-μ-NRCH₃)]₂ [E=Ga, R=H (1), CH₃ (2), CH₂Ph (3); E=In, R=H (4), CH₃ (5), CH₂Ph (6)] in high yields. The resulting complexes 1-6 have been characterized by ¹H-NMR spectroscopy and elemental analysis. Structure of the compound 1 determined by single-crystal X-ray analysis shows a dimeric feature containing a standard parallelogram Ga₂O₂ core bridging through the oxygen atom of ephedrine group. The catalytic asymmetric isocyanosilylation of meso cyclohexene oxide with trimethylsilyl cyanide has been realized with complexes 1-6 as catalysts.

Full text of DOI:10.1016/S0022-328X(03)00710-1

Journal of Organometallic Chemistry 682 (2003) 102Á107
/
www.elsevier.com/locate/jorganchem
Synthesis and asymmetric catalytic activities of chiral organogallium
and indium complexes with ephedrine derivatives as ligands. The
crystal structure of [(1R, 2S)-(Me2Ga-m-OCH(C6H5)CH(CH3)-m-
NHCH3)]2
Fang Yuan a, Chengjian Zhu a,b,*, Jiangtao Sun a, Yongjiang Liu a, Yi Pan a,*
a School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
Received 22 January 2003; received in revised form 1 July 2003; accepted 3 July 2003
Abstract
Reactions of trimethylgallium or trimethylindium with (1R, 2S)-(ꢀ
OCH(C6H5)CH(CH3)-m-NRCH3)]2 [EꢁGa, RꢁH (1), CH3 (2), CH2Ph (3); Eꢁ
The resulting complexes 1Á
6 have been characterized by 1H-NMR spectroscopy and elemental analysis. Structure of the compound
/
)-ephedrine derivatives afford compounds [(1R, 2S)-(Me2E-m-
/
/
/
In, RꢁH (4), CH3 (5), CH2Ph (6)] in high yields.
/
/
1 determined by single-crystal X-ray analysis shows a dimeric feature containing a standard parallelogram Ga2O2 core bridging
through the oxygen atom of ephedrine group. The catalytic asymmetric isocyanosilylation of meso cyclohexene oxide with
trimethylsilyl cyanide has been realized with complexes 1Á
/
6 as catalysts.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Organogallium; Organoindium; (ꢀ
/
)-Ephedrine derivatives; Crystal structure; Asymmetric catalysis
1. Introduction
plexes and apply them as catalysts in asymmetric
reactions.
The chemistry of organogallium and indium, which
contain either Group 15 or 16 elements, has been mainly
aimed at the possible application as organometallic
The desymmetrization of meso epoxides via the
enantioselective addition of nucleophiles is an efficient
strategy for asymmetric synthesis since it simultaneously
establishes two contiguous stereogenic centers. This type
of reaction has been successfully accomplished with
carbon nucleophiles, thiols, phenols, carboxylic acids,
aromatic amines, azides, and halide ions as nucleophiles
precursors for CVD of semiconductor film [1Á
their aluminum analogues, which have been widely used
as Lewis acids in catalytic reactions [5Á7], organogal-
/4]. Unlike
/
lium or indium complexes have been lacking in applica-
tion as catalysts in organic synthesis, especially as chiral
catalysts [8]. Because of the difference of Lewis acidity
and ion radii amongst the Group 13 elements, we believe
that the reaction pattern and reactivity of organogallium
and organoindium compounds would be different from
those of the organoaluminum ones. It would be valuable
to synthesize chiral organogallium and indium com-
[9Á15]. The reaction of epoxide with trimethylsilyl
/
cyanide (TMSCN) leads to formation of either b-
trimethylsilyloxy nitrile (C nucleophilic attack) or b-
trimethylsiloxy isocyanide (N nucleophilic attack) de-
pending on the nature of catalyst, due to the ambident
nucleophilic character of TMSCN (Scheme 1) [16]. The
enantioselective addition of TMSCN to meso epoxides
catalyzed by hard Lewis acid (chiral Ti catalyst) has
been reported by Hoveyda, which gave b-trimethylsily-
loxy nitriles with moderate to high enantiomeric excess
[17,18]. We have recently communicated the first
example of enantioselective isocyanosilylation of meso
* Corresponding authors. Tel.: ꢂ
7761.
E-mail
yipan@nju.edu.cn (Y. Pan).
/
86-25-359-4886; fax: ꢂ
/
86-25-331-
Zhu),
addresses:
cjzhu@netra.nju.edu.cn (C.
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00710-1

F. Yuan et al. / Journal of Organometallic Chemistry 682 (2003) 102Á
/107
103
and moisture. Exposure in air, the benzene solution of 1
became cloudy over night and the others would decom-
pose in several minutes. These compounds are very
soluble in polar solvent such as diethyl ether and
tetrahydrofuran. Complexes 2 and 3 can even be
dissolved in hexane, while the complex 1 is soluble in
aromatic hydrocarbon solvents. The solubility of the
organoindium compounds in hydrocarbon solvents is
better than that of the organogallium ones.
Scheme 1. Ambident nucleophilic attack of TMSCN to epoxide
catalyzed by different kinds of catalysts.
Reflecting the electropositive character of the metal
center, 1H-NMR spectra of the compounds consistently
epoxides with TMSCN catalyzed by chiral organogal-
lium and indium complexes with binaphthol monoether
derivatives as ligand [19].
exhibited the dimethylgallium hydrogens (d ꢀ
/
0.31 to ꢀ
/
0.81 ppm) at significantly upfield of TMS. Exemplified
by gallium complexes, there were remarkable differences
Here we wish to report the preparation and char-
acterization of several novel chiral dimethylgallium and
indium complexes, [(1R, 2S)-(Me2E-m-OCH(C6H5)-
1
between H-NMR spectra of the complexes and that of
dimethylgallium hydroxide and the free ligands. The 1H-
NMR resonances of the methyl groups in ꢀ
complexes 2 and 3 (d ꢀ0.81 ppm) appeared at upper
fields than in the dimethylgallium hydroxide (d ꢀ0.48
ppm), whereas those of complexes 1 (d ꢀ0.31 ppm)
/GaMe2 of
CH(CH3)-m-NRCH3)]2 (Eꢁ
/
Ga, In; RꢁH, CH3,
/
/
CH2Ph), with ephedrine derivatives as chiral ligands,
and the X-ray molecular structure of [(1R, 2S)-(Me2Ga-
m-OCH(C6H5)CH(CH3)-m-NHCH3)]2. In addition,
the enantioselective isocyanosilylation of meso cyclo-
hexene oxide with TMSCN was examined using
those chiral organogallium and indium complexes as
catalysts.
/
/
appeared at lower field. The reason might be that
tertiary amino group has stronger basicity, and thus
increases the electron density around the metal. Being
compared with those of free ligands, the ꢀ
/
NCH3 signals
of complexes 1, 2 and 3 (d 2.04Á2.05 ppm) shifted to
/
upper fields. This demonstrated that intramolecular
coordination bonds between the nitrogen atom and the
central metal were formed [23,24]. Organoindium com-
plexes 4, 5 and 6 exhibited similar spectra features with
those of gallium complexes.
2. Results and discussion
2.1. Synthesis and spectral analysis
Reactions of trimethylgallium or trimethylindium
with equivalent ephedrine or N-substitute derivatives,
2.2. Crystal structure of 1
[(1R, 2S)-PhCH(OH)CH(CH3)NRCH3, RꢁH, CH3,
/
CH2Ph] [20,21], proceeded smoothly in ether or benzene
at ambient temperature with the evolution of methane
Recrystalization of complex 1 in diethyl ether at low
temperature provided X-ray diffraction qualified single
crystals. The molecular structure of 1, which is shown in
Fig. 1, has been determined by X-ray analysis. The
crystallographic data is given in Table 1. Selected bond
lengths and bond angles are listed in Table 2.
The structure of 1 shows a dimeric feature containing
a standard parallelogram Ga2O2 core bridging through
the oxygen atom of ephedrine group. The bridging
gas, giving complexes 1Á
nearly quantitative yields. It is worth to notice that when
the reaction of (ꢀ)-ephedrine and trimethylgallium was
carried out at 2:1 ratio, the identical product of 1 was
obtained. Thus, the GaMe2 unit appears to be
/6, as shown in Scheme 2, in
/
ꢀ
/
remarkably stable in comparison with aluminum analo-
gue [22].
Complexes 1Á
6 is pasty oil. All of these complexes are sensitive to air
/
5 are white solids, whereas the complex
oxygen atom bond distances are slightly different to the
˚
O(1) distance of 1.922 A
two Ga centers with a Ga(1)ꢀ
/
Scheme 2. Synthesis of chiral organogallium and indium complexes with ephedrine derivatives as ligands.

104
F. Yuan et al. / Journal of Organometallic Chemistry 682 (2003) 102Á107
/
Table 2
˚
Selected bond lengths (A) and angles (8) for crystal of complex 1
Bond lengths
Ga(1)ꢀ
Ga(1)ꢀ
Ga(1)ꢀ
/
O(1)
1.922(3)
1.971(6)
2.088(3)
2.346(4)
1.968(5)
Ga(1)ꢀ
Ga(1)ꢀ
Ga(1a)ꢀ
Ga(1a)ꢀ
Ga(1a)ꢀ
/
N(1)
2.346(4)
1.968(5)
2.088(3)
1.971(6)
1.922(3)
/C(11)
/C(12)
/O(1a)
/O(1)
Ga(1a)ꢀ
/N(1a)
/C(11a)
Ga(1a)ꢀ
/C(12a)
/O(1a)
Bond angles
O(1)ꢀGa(1)ꢀ
C(11)ꢀGa(1)ꢀ
C(11)ꢀGa(1)ꢀ
O(1)ꢀGa(1)ꢀ
C(12)ꢀGa(1)ꢀ
C(7)ꢀO(1)ꢀGa(1)
Ga(1)ꢀO(1)ꢀ
C(10)ꢀN(1)ꢀ
/
/
C(11)
113.9(2)
126.1(3)
O(1)ꢀ
O(1)ꢀ
/
Ga(1)ꢀ
Ga(1)ꢀ
Ga(1)ꢀ
Ga(1)ꢀ
Ga(1)ꢀ
O(1)ꢀGa(1)
N(1)ꢀC(8)
N(1)ꢀGa(1)
/
C(12) 119.8(2)
/
/C(12)
/
/O(1a) 73.70(14)
/
/O(1)
99.18(18) C(12)ꢀ
75.94(13) C(11)ꢀ
91.0(2)
124.0(3)
/
/O(1)
99.1(2)
98.21(18)
149.09(13)
129.4(3)
114.3(4)
101.6(3)
/
/N(1)
/
/N(1)
/
/N(1)
O(1)ꢀ
/
/N(1)
/
/
C(7)ꢀ
/
/
/
/
Ga(1a) 106.18(14) C(10)ꢀ
/
/
/
/Ga(1) 116.4(3)
C(8)ꢀ
/
/
Fig. 1. Molecular structure of bis[dimethyl((ꢀ
/
)-ephedrinato)gallium]
(1). Hydrogen atoms are omitted for clarity.
described as a distorted trigonal bipyramid, in which the
axial positions are occupied with coordinate nitrogen
N(1) and bridging O(1a), while the apices of the
equatorial triangle are O(1) and both gallium methyl
Table 1
Crystal data, collection parameters, and refinements
Identification code
Empirical formula
Formula weight
1
carbon atoms. The coordinate bond distance of Ga(1)ꢀ
/
C
528.02
24H40Ga2N2O2
˚
N(1) has a value of 2.346 A, which agrees well with the
Ga1
N(sp3) bond lengths in such as Cl2Ga[N(CH2CH2-
NEt2)2] (2.287 A) [2], and is obviously longer than those
˚
Wavelength (A)
0.71073
Orthorhombic
C222(1)
/
Crystal system
Space group
Unit cell dimensions
˚
of Ga1
/
N(sp2) bond lengths in the compounds such as
˚
salen(tBu)H(GaEt2) (2.030 A) [25], salomphen(t-
˚
a (A)
11.784(4)
12.933(4)
34.980(11)
90
˚
Bu)GaMe (2.064 A) [26], and dimethyl[N-salicyli-
˚
dene2-aminopyridine]gallium (2.095 A) [27]. Arising
upon coordination to the metal, both nitrogen atoms
become stereogenic. It is worth to notice that the
nitrogen-bonded hydrogen atom remains in the product,
although the H atom should be fairly active towards
gallium-bonded methyls.
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
90
90
T (K)
3
V (A )
293(2)
5331(3)
8
˚
Z
F(0 0 0)
Dcalc (Mg mꢀ3
2208
1.316
2.042
)
2.3. Enantioselective ring opening of cyclohexene oxide
Absorption coefficient (mmꢀ1
Crystal size (mm3)
)
with TMSCN catalyzed by complexes 1Á6
/
0.50ꢃ
2.33Á25.00
135h 514, ꢀ
415l 527
13 712
4693 [Rint
/
0.25ꢃ
/
0.25
u Range for data collection
Index ranges
/
/
/
/155
/
k 5
/
14, ꢀ
/
The reactions of TMSCN with cyclohexene oxide
catalyzed by complex 1Á6 were examined. With the
addition of MS 4A, these reactions were started at ꢀ
/
/
/
Reflections collected
Independent reflections
Completeness to u
/
ꢁ/0.0433]
78 8C and then risen to room temperature and stirred
for 10 h, followed by treatment with methanol solution
25.00 (99.8%)
Absorption correction
Max and min transmission
Refinement method
SADABS
0.670776 and 0.907701
Full-matrix least-squares on F2
of potassium fluoride to remove ꢀ
/
SiMe3 group, we
found that, as envisioned, all the reactions gave the
product of b-isocyanocyclohexanol, which was identi-
fied by IR and 1H-NMR analysis, with the absolute
configuration 1R, 2R (Scheme 3). As summarized in
Table 3, the expected b-isocyanocyclohexanol has been
obtained in yields varying from 55 to 78%, with the
enantioselectivity varying from 15 to 48% depending on
the nature of the catalyst used. It should be note that the
reaction showed much less reactivity and selectivity
without MS 4A (Entry 2). The intrinsic role of the MS
4A needs to be further exploited. The isocyanosilylation
of cyclohexene oxide catalyzed by catalyst 3 gave the
Data/restraints/parameters
Goodness-of-fit on F2
4693/0/271
1.029
Final R indices [I ꢀ
R indices (all data)
Absolute structure parameter
Largest difference peak and hole 0.610 and ꢀ
/
2s(I)]
R1ꢁ
R1ꢁ
0.028(16)
/0.0447, wR2ꢁ
/
0.0904
/0.0580, wR2ꢁ
/0.0930
/0.262
ꢀ3
˚
(e A
)
˚
O(1) distance of 2.088 A. There are three
and Ga(1a)ꢀ
/
fused-rings in the compound in the dorm of [3.3.0.0].
The coordination number of the central metal is five,
and the geometry around the gallium center can be

F. Yuan et al. / Journal of Organometallic Chemistry 682 (2003) 102Á
/107
105
Scheme 3. The reaction of cyclohexene oxide with TMSCN catalyzed by chiral organogallium and indium complexes.
activating epoxide and also controlling the orientation
of epoxide due to coordination of an axial lone pair,
Table 3
Enantioselective ring opening of cyclohexene epoxide with trimethyl-
allowing for the cleavage of Cꢀ
/
O bond by backside
siyl cyanide catalyzed by 1Á6
/
attack. Based on the structure of complex 1 and the
absolute configuration of the product (1R, 2R) obtained
by this catalyst, enantiomeric induction in the present
system can be understood by assuming the transition
state A. 13C-NMR measurement of a mixture of
complex 1 and TMSCN exhibited no resonance of
Entry
Catalyst
Yield a(%)
ee b(%) (config.) c
1
no
1
0
40
55
61
67
65
69
78
0
2 d
3
14 (1R, 2R)
26 (1R, 2R)
41 (1R, 2R)
48 (1R, 2R)
15 (1R, 2R)
23 (1R, 2R)
35 (1R, 2R)
1
4
2
5
3
Gaꢀ
/
CN species. This strongly supported Gaꢀ
/CN
6
4
species, which most probably led to formation of
cyanosilylation product, was not involved in this reac-
tion [16].
7
5
8
6
a
Isolated yield based on cyclohexene oxide.
Enantioselectivity excess values were determined by HPLC
b
analysis using a DAICEL CHIRAL OD-H column.
c
3. Experimental
The absolute configuration was determined by converting b-
isocyanocyclohexanol to b-aminocyclohexanol [28] and then compar-
ing the optical rotations with literature values [29].
3.1. General procedures
d
Without MS 4A.
All reactions were performed in a glove box under
nitrogen. The solvents were refluxed with sodium
benzophenone and distilled under nitrogen prior to
best selectivity up to 48% ee with the yield of 67% (Entry
5). We found that gallium complexes (1Á
better result in enantioselectivity but lower yields than
indium complexes (4Á6). It is particular worthy to note
/3) showed
use. (1R, 2S)-(ꢀ
zation of commercial available (1R, 2S)-(ꢀ
hydrochloride. Derivatives of (1R, 2S)-(ꢀ
/
)-Ephedrine was obtained by neutrali-
)-Ephedrine
)-ephedrine
/
/
that the substituents in the amino group of catalysts had
a significant effect on the enantioselectivity of the
asymmetry ring opening reaction. This is exemplified
by a comparison of catalysts 1, 2 and 3. Better
enantioselectivities and yields were achieved by using
/
were prepared according to the literatures [20,21].
Trimethylgallium and trimethylindium were provided
by the National 863 Program Advanced Material MO
Precursors R&D Center of China.
1H-NMR data were collected on a Bruker ARX-300
spectrometer, with chemical shifts referenced to SiMe4
as internal standard. Infrared spectra were obtained as
KBr pellets with a 5DX-FT-2 spectrometer. Elemental
steric
ligands.
ꢀ
/
NMe and
ꢀ
/
NBn ephedrine derivatives as
A proposal mechanism for the catalytic asymmetric
epoxide opening is shown in Scheme 4. A gallium (or
indium) metal appears to function as a soft Lewis acid,
analyses were performed on a PerkinÁElmer 240 C
/
elemental analyzer.
3.2. Determination of enantiomeric purity
Enantiomeric excesses (ee’s) were determined by
HPLC analysis performed on JASCO HPLC systems
consisting of the following: pump, Shimadzu LC-10AD;
detector, Shimadzu SPD-6A UV Spectrophotometric
Detector, measured at 220 nm; column DAICEL
CHIRALPAK OD-H; mobile phase, hexane/2-propa-
nol; flow rate, 0.5 ml minꢀ1
.
3.3. Bis[dimethyl((ꢀ)-ephedrinato)gallium] (1)
/
Me3Ga (4.2 mmol) in 14 ml of Et2O was added
dropwise to a stirred solution of (ꢀ)-ephedrine (0.5 g,
Scheme 4. Working model for the ring opening of cyclohexene oxide
with Me3SiCN catalyzed by chiral Ga-complexes.
/

106
F. Yuan et al. / Journal of Organometallic Chemistry 682 (2003) 102Á107
/
3.0 mmol) in Et2O (4 ml) at room temperature (r.t.) (ca.
30 min). During the addition of Me3Ga, a vigorous
evolution of gas was observed. The resulting solution
continued to stir over night and a white precipitate
formed. The solution was decanted leaving a white solid
that was washed with Et2O and dried in vacuo. Yield:
0.78 g (98%). Found: C, 54.88; H, 7.57; N: 5.33. Anal.
Calc. for C24H40Ga2N2O2: C, 54.57; H, 7.64; N, 5.30%.
1H-NMR (CDCl3, ppm): d 7.31 (m, 5H), 5.04 (s, 1H),
(d, Jꢁ
Jꢁ6.45 Hz, 3H), 0.87 (d, Jꢁ
6H).
/
3.6 Hz, 1H), 2.71 (m, 1H), 2.51 (s, 1H), 2.30 (d,
/
/
6.6 Hz, 3H), ꢀ0.48 (s,
/
3.7. Bis[dimethyl((ꢀ
/
)-N-methylephedrinato)indium]
(5)
Me3In (1.326 mmol) in C6H6 (6 ml) was added
dropwise to the solution of (ꢀ)-N-methylephedrine
/
3.05 (s, 1H), 2.05 (s, 3H), 2.42 (s, 1H), 0.88 (d, Jꢁ
/6.54
(0.2 g, 1.12 mmol) in 2 ml of C6H6 at r.t. (ca. 30 min).
During the addition of Me3In, a vigorous evolution of
gas was observed. The resulting solution continued to
stir over night followed by refluxing for 0.5 h. Volatiles
were removed in vacuo and the residue was crystallized
from hexane to give a white crystal. Yield: 0.35 g (97%).
Found: C, 48.28; H, 6.69; N, 4.46. Anal. Calc. for
Hz, 3H), ꢀ0.31 (s, 6H).
/
3.4. Bis[dimethyl((ꢀ
/
)-N-methylephedrinato)gallium]
(2)
To a solution of (ꢀ)-N-methylephedrine (0.18 g, 1
/
1
mmol) in C6H6 (2 ml), Me3Ga (2 mmol) in 2 ml of C6H6
was added with stirring at r.t. A vigorous evolution of
gas was observed. The resulting solution continued to
stir over night followed by refluxing for 0.5 h. Volatiles
were removed in vacuo to give a white solid. Yield: 0.26
g (96%). Found: C, 56.38; H, 7.57; N, 5.27. Anal. Calc.
C26H44In2N2O2: C, 48.30; H, 6.81; N, 4.33%. H-NMR
3
(CDCl3, ppm): d 7.21 (m, 5H), 4.96 (d, Jꢁ
1H), 2.28 (s, 1H), 2.17 (S, 6H), 0.76 (d, Jꢁ
/
3.09 Hz,
6.84 Hz,
3
/
3H), ꢀ0.52 (S, 6H).
/
1
3.8. Bis[dimethyl((ꢀ
/
)-N-benzylephedrinato)indium]
for C26H44Ga2N2O2: C, 56.12; H, 7.91; N, 5.04%. H-
(6)
NMR (CDCl3, ppm): d 7.21 (m, 5H), 5.0 (d, Jꢁ
1H), 3.15 (s, 1H), 2.50 (s, 3H), 2.05 (s, 3H), 1.04 (d, Jꢁ
6.96 Hz, 3H), ꢀ0.81 (s, 6H).
/5.1 Hz,
/
Me3In (1.326 mmol) in C6H6 (6 ml) was added
dropwise to (ꢀ)-N-benzylephedrine (1 mmol) in C6H6
/
/
(6 ml) at r.t. (ca. 30 min). During the addition of Me3In,
a vigorous evolution of gas was observed. The resulting
solution continued to stir over night followed by
refluxing for 0.5 h. Volatiles were removed and the
residue was dried in vacuo to give an oil. Yield: 0.36 g
(92%). Found: C, 57.23; H, 6.69; N, 3.69. Anal. Calc. for
3.5. Bis[dimethyl((ꢀ
(3)
/
)-N-benzylephedrinato)gallium]
To a solution of (ꢀ)-N-benzylephedrine (1 mmol) in
/
C6H6 (6 ml), Me3Ga (2 mmol) in 2 ml of C6H6 was
added with stirring at r.t. A vigorous evolution of gas
was observed. The resulting solution continued to stir
over night followed by refluxing for 0.5 h. Volatiles were
removed in vacuo and the residue was crystallized from
1
C38H52In2N2O2: C, 57.14; H, 6.51; N, 3.51%. H-NMR
(CDCl3, ppm): d 7.28 (m, 10H), 5.16 (s, 1H), 3.57 (s,
2H), 2.37 (b, 1H), 2.01 (s, 3H), 0.82 (d, Jꢁ/6.39 Hz, 3H),
ꢀ
/
0.521 (s, 6H).
CH2Cl2Áhexane (1:1) to give a white solid. Yield: 0.34 g
/
(96%). Found: C, 64.17; H, 7.45; N, 3.66. Anal. Calc. for
C38H52Ga2N2O2: C, 64.41; H, 7.34; N, 3.95%. 1H-NMR
(CDCl3, ppm): d 7.23 (m, 10H), 5.19 (s, 1H), 3.85 (s,
3.9. General procedure for asymmetric ring opening of
epoxycyclohexane with TMSCN
2H), 3.3 (b, 1H), 2.14 (s, 3H), 1.05 (d, Jꢁ
/
6.09 Hz, 3H),
ꢀ
/
0.81 (s, 6H).
A mixture of catalyst (0.2 mmol) and 0.4 g molecular
sieve (4A) in dichloromethane (15 cm3) was stirred at
3.6. Bis[dimethyl((ꢀ
/
)-ephedrinato)indium] (4)
ꢀ78 8C. After 15 min, cyclohexene oxide (2 mmol) and
/
TMSCN (2.4 mmol) were added and the resulting
mixture was risen to r.t. gradually and stirred for
another 10 h, followed by treatment with methanol
solution of potassium fluoride (0.8 g in 10 cm3
methanol) for 5 h. The reaction mixture was filtered,
concentrated and separated by flash chromatography
(petroleum ether and ethyl acetate as the eluent) to give
Me3In (1.08 mmol) in C6H6 (16 ml) was added
dropwise to the solution of (ꢀ)-ephedrine (0.15 g, 0.9
mmol) in C6H6 (2 ml) at r.t. (ca. 30 min). During the
addition of Me3In, a vigorous evolution of gas was
observed. The resulting solution continued to stir over
night followed by refluxing for 1.5 h. Volatiles were
removed in vacuo and the residue was crystallized from
/
1
the b-isocyanocyclohexanol as a white solid. H-NMR
hot petroleum ether (b.p.: 60Á
/
90 8C) to give a white
(CDCl3, 300 MHz): d 3.84Á
2.18Á
HPLC (DAICEL CHIRALPAK OD-H, n-hexane/i-
PrOHꢁ100:0.5): Rtꢁ10.25 min, 12.25 min.
/
3.31 (m, 2H), 2.66 (s, 1H),
crystal. Yield: 0.26 g (95%). Found: C, 46.69; H, 6.53; N,
4.38. Anal. Calc. for C24H40In2N2O2: C, 46.60; H, 6.47;
N, 4.53%. 1H-NMR (CDCl3, ppm): d 7.30 (m, 5H), 4.82
/
1.18 (m, 8H). IR (KBr): nꢁ
/
3347, 2147 cmꢀ1
.
/
/

F. Yuan et al. / Journal of Organometallic Chemistry 682 (2003) 102Á
/107
107
3.10. X-ray structure determination of crystal 1
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Acknowledgements
We gratefully acknowledge the National Natural
Science Foundation of China (20102002), Science
Foundation of Jiangsu Province (BK2001030) and the
863 High Technology Program for their financial
support. The research funds for Y. Pan from Qin-Lan
Program of Jiangsu Province and Kua-Shi-Ji Program
of Education Ministry of PRC are also acknowledged.
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