Asymmetric base-free michael addition at room temperature with nickel-based bifunctional amido-functionalized N-heterocyclic carbene catalysts

Article abstract of DOI:10.1002/ejic.201403224

A series of nickel-based chiral bifunctional catalysts (1d-3d) with N-heterocyclic carbene (NHC) ligands derived from (1R)-(-)-menthol, (1S)-(-)pinene, and (1R)-(+)-camphor have been successfully designed for asymmetric Michael addition reactions under base-free conditions. The NHC complexes, namely, [1-R-3-{N-(phenylacetamido)}imidazol-2-ylidene]₂Ni [R = (1S)-menthyl (1d), (1S)-pinane (2d), and (1R)-isobornyl (3d)], bearing chiral ancillaries on the amido-functionalized side arms of the NHC ligands, performed the bifunctional catalysis of the asymmetric base-free Michael addition reaction of the α-methyl cyano ester substrates ethyl 2-cyanopropanoate (4), isopropyl 2-cyanopropanoate (5), and tert-butyl 2-cyanopropanoate (6) with the activated olefinic substrates methyl vinyl ketone (7) and acrylonitrile (8) in 63-98 % yields with enantiomeric excess (ee) values of 2-75 % at room temperature in 8 h. More interestingly, only the longest of the three catalysts, the menthol derivative 1d, showed significant chiral induction of up to 75 % ee; this has been attributed to the reduction of the steric influence owing to the relatively distant dispositions of the chiral ancillaries from the catalytically active metal center that arise as a consequence of the cis geometries of 1d-3d. A series of nickel-based chiral bifunctional catalysts with N-heterocyclic carbene ligands derived from readily available and inexpensive (1R)-(-)-menthol, (1S)-(-)pinene, and (1R)-(+)-camphor synthons successfully catalyze asymmetric base-free Michael addition reactions under ambient conditions.

Full text of DOI:10.1002/ejic.201403224

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DOI:10.1002/ejic.201403224
Asymmetric Base-Free Michael Addition at Room
Temperature with Nickel-Based Bifunctional Amido-
Functionalized N-Heterocyclic Carbene Catalysts
Mitta Nageswar Rao,[a] Meera Haridas,[a] Manoj Kumar Gangwar,[a]
Palanisamy Rajakannu,[a] Alok Ch. Kalita,[a] and Prasenjit Ghosh*[a]
Keywords: Asymmetric catalysis / Michael addition / Bifunctional catalysts / Carbene ligands / Nickel
A series of nickel-based chiral bifunctional catalysts (1d–3d)
with N-heterocyclic carbene (NHC) ligands derived from
(1R)-(–)-menthol, (1S)-(–)pinene, and (1R)-(+)-camphor have
been successfully designed for asymmetric Michael addition
reactions under base-free conditions. The NHC complexes,
namely, [1-R-3-{N-(phenylacetamido)}imidazol-2-ylidene]2-
Ni [R = (1S)-menthyl (1d), (1S)-pinane (2d), and (1R)-iso-
bornyl (3d)], bearing chiral ancillaries on the amido-function-
alized side arms of the NHC ligands, performed the bifunc-
tional catalysis of the asymmetric base-free Michael addition
reaction of the α-methyl cyano ester substrates ethyl 2-cyano-
propanoate (4), isopropyl 2-cyanopropanoate (5), and tert-
butyl 2-cyanopropanoate (6) with the activated olefinic sub-
strates methyl vinyl ketone (7) and acrylonitrile (8) in 63–
98% yields with enantiomeric excess (ee) values of 2–75%
at room temperature in 8 h. More interestingly, only the long-
est of the three catalysts, the menthol derivative 1d, showed
significant chiral induction of up to 75%ee; this has been
attributed to the reduction of the steric influence owing to
the relatively distant dispositions of the chiral ancillaries from
the catalytically active metal center that arise as a conse-
quence of the cis geometries of 1d–3d.
NCN pincer palladium complexes in asymmetric Michael
addition reactions between alkyl vinyl ketones and α-methyl
cyano esters.[7] However, another type of chiral PdII pincer
complex displayed lower enantioselectivities of up to
34%ee for the same reaction.[8] Chiral platinum complexes
bearing phosphino-oxazoline derived ligands also exhibited
low enantioselectivities of up to 25%ee.[9] Lastly, cationic
NCN-type chiral nickel pincer complexes produced
Michael adducts with excellent yields even at –78 °C but
without any enantioselectivity.[10] Hence, against this back-
drop, an early report of the asymmetric Michael addition
of α-methyl cyano esters to various vinyl ketones with very
good enantioselectivities of up to 89%ee with an in situ
generated bifunctional catalyst in the form of a chiral RhI
complex supported over a trans-chelating diphosphine li-
gand assumes significance.[11]
Of the several approaches described above, the concept
of bifunctional catalysis is appealing to us, and we contrib-
uted by developing a class of N-heterocyclic carbene (NHC)
based bifunctional nickel catalysts for the Michael addition
reaction under base-free conditions.[12,13] The rationale be-
hind this approach stems from our observation that al-
though NHC ligands have been phenomenally successful in
homogeneous catalysis, their development as metal-based
bifunctional catalysts has lagged behind.[12a,13] We further
rationalized that the contentious issue of the requirement
of an external base, which is often used stoichiometrically
or even in a large excess under classical Michael conditions,
may be avoided owing to the simultaneous presence of basic
Introduction
The base-free Michael addition, and more so its asym-
metric version, marks an important improvement to the
parent reaction,[1] which, over a century since its first dis-
covery in 1887,[2] continues to fall among the most popular
methods for C–C bond construction in organic synthesis.
However, the reaction remains plagued by many unwanted
side reactions, which arise from the required presence of a
base under the classical reaction conditions. In this context,
bifunctional organocatalysts[3] with chiral organic frame-
works based on thiourea,[4] proline,[5] and cinchona alka-
loids[6] have become popular in asymmetric Michael ad-
ditions, but examples of the bifunctional catalysis with
metal complexes have remained largely overlooked.
Of the handful of examples of metal-mediated asymmet-
ric Michael addition reactions, most involve the use of chi-
ral metal complexes in the presence of an external base such
as iPr2NEt, and examples of base-free bifunctional metal-
mediated catalysis are rare. For example, good enantio-
selectivity of up to 83%ee was observed for neutral chiral
[a] Department of Chemistry, Indian Institute of Technology Bom-
bay,
Powai, Mumbai 400076, India
E-mail: pghosh@chem.iitb.ac.in
http://www.chem.iitb.ac.in/~pghosh/
http://www.chem.iitb.ac.in/people/Faculty/prof/pg.html
http://www.iitb.ac.in
http://www.chem.iitb.ac.in
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201403224.
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and acid sites on a bifunctional catalyst. Developing the (2d), and (1R)-isobornyl (3d); Figure 1]. A key aspect of our
theme even further, we intended to achieve the asymmetric strategy has been the attainment of the bifunctional catalyst
Michael addition under base-free conditions through the complexes 1d–3d in optically pure forms from inexpensive
use of chiral NHC-based bifunctional catalysts. Notably, in and readily available menthol-, pinene-, and camphor-based
the field of chiral N-heterocyclic carbene chemistry, the synthons to avoid any of the cumbersome protocols often
asymmetric version of the base-free Michael addition has associated with optical resolution. To incorporate the chiral
not been explored; hence, we decided to look into the pos- ancillaries into the amido-functionalized side-arm substitu-
sible utility of bifunctional catalysis with chiral nickel-based ents of the N-heterocyclic carbene ligands, chiral imid-
N-heterocyclic carbene complexes for the asymmetric azoles, namely, 1-(1S)-menthylimidazole (1b), 1-[(1S)-pi-
Michael addition.
nan-3-yl]imidazole (2b), and 1-(1R)-isobornylimidazole
In this contribution, we report the asymmetric Michael (3b), were synthesized in 24–29% yields (Scheme 1). The
addition under base-free conditions of α-methyl cyano es- alkylation of imidazoles 1b–3b with 2-chloro-N-phenylacet-
ters to activated olefins with chiral nickel-based bifunc- amide side arms yielded the corresponding imidazolium
tional catalysts of chelating amido-functionalized N-hetero- chloride salts [1-R-3-{N-(phenylacetamido)}imidazolium]
cyclic carbene ligands, namely, [1-R-3-{N-(phenylacet- chloride [R = (1S)-menthyl (1c), (1S)-pinane (2c), and (1R)-
amido)}imidazol-2-ylidene]2Ni [R = (1S)-menthyl (1d), isobornyl (3c)] in 84–92% yields; these salts were heated to
(1S)-pinane (2d), and (1R)-isobornyl (3d)].
reflux in CH3CN with NiCl2·6H2O in the presence of
K2CO3 as a base to yield the nickel complexes 1d–3d in 26–
36% yield. NMR spectroscopy studies of 1d–3d indicated
their diamagnetic nature, which suggests that these com-
plexes have square-planar geometries. The conspicuous ab-
Results and Discussion
A series of chiral amido-functionalized N-heterocyclic
carbene ligands were employed to develop the nickel-based
1
sence of the amido NH resonance in the H NMR spectra
of 1d–3d indicated the deprotonation of this group and sub-
sequent chelation to the metal center. The characteristic
Ni–Ccarbene resonances appeared at δ = 166.2–170.3 ppm in
the 13C{1H} NMR spectra.
bifunctional
catalysts
[1-R-3-{N-(phenylacetamido)}-
imidazol-2-ylidene]2Ni [R = (1S)-menthyl (1d), (1S)-pinane
The molecular structures of 1d–3d revealed square-
planar geometries at the metal centers, as is consistent with
their earlier mentioned diamagnetic nature (Figures 2, 3,
and 4; Table 1). The Ni–Ccarbene distances of 1.888(4) and
1.876(4) Å in 1d, 1.843(5) and 1.862(5) Å in 2d, and
1.863(2) and 1.866(2) Å in 3d are slightly shorter than the
sum of the individual covalent radii of the Ni and C atoms
(Ni–C 1.926 Å),[14] whereas the Ni–Namido distances of
1.971(3) and 1.967(3) Å in 1d, 1.968(4) and 1.955(4) Å in
2d, and 1.9619(19) and 1.934(2) Å in 3d are marginally
larger than the sum of the individual covalent radii of the
Ni and N atoms (Ni–N 1.854 Å).
One interesting aspect of the structures of 1d–3d is their
cis geometries, in which the two amido-functionalized N-
heterocyclic carbene ligands are chelated to the metal center
through their amido N and carbene C atoms in a cis dispo-
Figure 1. Ni complexes 1d–3d.
Scheme 1.
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Figure 4. ORTEP drawing of 3d with thermal ellipsoids drawn at
the 50% probability level. Selected bond lengths [Å] and angles [°]:
Ni1–C13 1.863(2), Ni1–C34 1.866(2), Ni1–N5 1.9619(19), Ni1–N6
1.934(2), C13–Ni1–C34 93.63(10), C34–Ni1–N6 86.46(9), C34–
Ni1–N5 176.37(10), C13–Ni1–N6 177.47(10), C13–Ni1–N5
86.51(10), N6–Ni1–N5 93.57(9).
Figure 2. ORTEP drawing of 1d with thermal ellipsoids drawn at
the 50% probability level. Selected bond lengths [Å] and angles
[°]: Ni1–C1 1.888(4), Ni1–C22 1.876(4), Ni1–N4 1.967(3), Ni1–N1
1.971(3), C22–Ni1–C1 90.82(18), C22–Ni1–N4 87.56(17), C1–Ni1–
N4 174.18(16), C22–Ni1–N1 172.02(16), C1–Ni1–N1 88.92(16),
N4–Ni1–N1 93.46(14).
Table 1. X-ray crystallographic data for the 1d–3d.
1d
2d
3d
Lattice
orthorhombic
C42H56N6NiO5
783.64
P212121
10.8969(3)
19.5291(5)
19.6755(6)
90.00
orthorhombic orthorhombic
C43H56N6NiO3 C42H50N6NiO2
Formula
Formula weight
Space group
a [Å]
b [Å]
c [Å]
763.65
P212121
16.257(5)
22.353(6)
24.076(7)
90.00
729.59
P212121
12.242(5)
17.430(5)
17.448(5)
90.00
α [°]
β [°]
90.00
90.00
90.00
γ [°]
90.00
4187.1(2)
4
90.00
8749(4)
8
90.00
3723(2)
4
V [Å3]
Z
Temperature [K]
Radiation λ [Å]
ρcalcd. [gcm–3]
μ(Mo-Kα) [mm–1]
θmax [°]
150(2)
0.71073
1.243
0.513
25.00
100(2)
0.71075
1.160
0.486
25.00
150(2)
0.71073
1.302
0.566
24.99
Number of data
Number of param- 493
eters
7345
15367
959
6571
460
R1
wR2
GOF
0.0488
0.1239
0.961
0.0667
0.1401
1.060
0.0295
0.0791
1.151
Figure 3. ORTEP drawing of 2d with thermal ellipsoids drawn at
the 50% probability level. Selected bond lengths [Å] and angles
[°]: Ni1–C11 1.843(5), Ni1–C32 1.862(5), Ni1–N4 1.955(4), Ni1–N1
1.968(4), C11–Ni1–C32 91.66(19), C11–Ni1–N4 177.26(18), C32–
Ni1–N4 87.50(18), C11–Ni1–N1 86.86(17), C32–Ni1–N1
174.57(19), N4–Ni1–N1 94.21(16).
sition to each other. An unanticipated consequence of the
cis geometries of 1d–3d is the distant location of the chiral
auxiliaries from the metal center; this significantly under-
mines the asymmetric induction, as was observed during
the catalysis studies. A scrutiny of the catalytic cycle that
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Scheme 2.
we proposed previously further elucidates this point calculations were undertaken to determine the stability or-
(Scheme 2).[15]
der of these cis and the trans isomers in the solution phase
Thus, to get an insight into the relative stabilities of the with CH3CN as the medium. This particular solvent was
respective cis and trans isomers of 1d–3d, density functional chosen primarily because 1d–3d were prepared in the same
theory studies were undertaken. The geometry optimiza- medium. The PCM calculation results also favored the cis
tions were done at the B3LYP/LANL2DZ, 6-31G(d) level structures for all of three complexes in CH3CN, and even
of theory for both of the conformational isomers of 1d–3d. higher stabilizations of 9.33 kcalmol–1 for the menthol de-
The atomic coordinates of the cis isomers of 1d–3d were rivative 1d, 11.0 kcalmol–1 for the pinene derivative 2d, and
obtained from the X-ray analysis data, whereas those of the 11.5 kcalmol–1 for the camphor derivative 3d were ob-
trans isomers of 1d–3d were obtained by applying suitable tained. The higher stabilities of the cis isomers of 1d–3d in
modifications to the X-ray data with the Chemcraft soft- the solvent phase (CH3CN) relative to those in the isolated
ware.[16] Subsequently, single-point calculations along with gas phase is an outcome of the greater stabilization of the
post-wave-function analysis by the natural bond order cis isomers, which have higher dipole moments (μ) of 15.4
(NBO) method were performed on the geometry-optimized (1d), 15.7 (2d), and 16.14 D (3d) than those of their trans
structures at the same level of theory for a detailed under- counterparts [1.1 (1d), 0.6 (2d), and 1.1 D (3d)] in polar
standing of the electronic properties of these complexes.
CH3CN. In this regard, in contrast to our observation that
A comparison of the respective free energies of the cis the cis isomers of 1d–3d are stable in both the isolated gas
and trans isomers of 1d–3d showed that the cis structure is phase and in the polar solvent phase (CH3CN), it is worth
favored for all three complexes in the isolated gas phase noting that a recent theoretical study[17] found that the cis
(Figure 5). In particular, the cis isomer is more stable by isomers of the nonchelated [(NHC)2PdX2] (X = Cl, Br) type
1.62 kcalmol–1 for the menthol derivative (1d), of complexes were favored in polar media such as CH2Cl2
3.65 kcalmol–1 for the pinene derivative 2d, and and tetrahydrofuran (THF), whereas the trans isomers were
5.21 kcalmol–1 for the camphor derivative (3d); these results favored in the gas phase. Thus, the difference in the relative
are consistent with our isolation of the cis isomers of 1d– stabilities of the cis and trans isomers is highly ligand-de-
3d in the solid state, as observed in the single-crystal X- pendent. In our case, 1d–3d are supported by chelating an-
ray diffraction studies. Polarizable continuum model (PCM) ionic amido-functionalized NHC ligands, and the cis iso-
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Figure 5. The relative free energies ΔG [kcal/mol] of the cis and trans isomers of 1d–3d in the isolated gas phase (blue) and in CH3CN (red).
Table 2. The base-free 1,4-Michael-type activated C–H addition of
mers were favored in both the isolated gas phase and in the
the representative substrate (4) across a representative α,β-unsatu-
solvent phase (CH3CN), as opposed to the nonchelating
rated substrate, methyl vinyl ketone (7), as catalyzed by 1d–3d.
Conditions: Michael donor (1.00 mmol), Michael acceptor
NHC ligands used in the earlier study,[17] for which the cis
isomers were favored only in the solvent phase. Further, in-
stances of the solvent-dependent interconversions between
the cis and trans isomers of related nickel complexes have
been observed.[18] Thus, having established that the cis iso-
mers of 1d–3d are stable in the isolated gas phase and the
polar solvent phase (CH3CN), catalysis studies were sub-
sequently undertaken.
(1.5 mmol), and catalyst (2 mol-%) in solvent (5 mL) at room tem-
perature for 8 h.
Each of 1d–3d performed the desired bifunctional cataly-
sis of the base-free Michael addition of a representative α-
methyl cyano ester substrate, ethyl 2-cyanopropanoate (4),
to a representative activated olefinic substrate, methyl vinyl
ketone (7), under ambient conditions; see Table 2 and
Equation (1).
However, though good-to-excellent conversions (68–
98%) to the respective products were observed for all of the
catalyst complexes, only the menthol derivative 1d exhibited
significant chiral induction (up to 75%ee), whereas the pi-
[a] Isolated yields unless otherwise noted. [b] Enantiomeric excesses
were determined by GC with a CP-Chirasil-Dex CB chiral column.
nene (2d) and camphor (3d) derivatives remained ineffec- [c] GC yield.
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tive. Such an observation is attributed to the cis geometries Table 3. Selected results for the base-free 1,4-Michael-type acti-
vated C–H addition of substrates 4–6 across the representative α,β-
of 1d–3d, which result in the distant disposition of the chiral
unsaturated substrates 7 and 8 catalyzed by 1d. Conditions:
auxiliaries from the metal center, the site of asymmetric ca-
Michael donor (1.00 mmol), Michael acceptor (1.5 mmol), and cat-
alyst 1d (2 mol-%) in CHCl3 (5 mL) at room temperature for 8 h.
talysis. As a consequence, the chiral induction is consider-
ably reduced to such an extent that no inductions were seen
for the pinene (2d) and camphor (3d) complexes. In this
regard, it is worth noting that the menthol moiety has a
larger lateral cross-section than the pinene and camphor
moieties, and this is significant enough to exercise chiral
induction for this particular catalyst.
The effectiveness of the menthol derivative 1d in the bi-
functional catalysis was evident from a time-dependent
study that showed up to 96% of product conversion and up
to 68%ee within the first 3 h of the reaction, after which
the values reached a plateau for the base-free Michael ad-
ditions of the representative substrate isopropyl 2-cyano-
propanoate (5) to methyl vinyl ketone (7) (Figure 6). The
solvent-dependence study identified chloroform to be the
most-suitable solvent for the base-free Michael addition re-
action (Table 2).
[a] Isolated yields. [b] Enantiomeric excesses were determined by
GC with a CP-Chirasil-Dex CB chiral column.
ethyl 2-cyanopropanoate (4), isopropyl 2-cyanopropanoate
(5), and tert-butyl 2-cyanopropanoate (6) with the activated
olefinic substrates methyl vinyl ketone (7) and acrylonitrile
(8). Lastly, the homogeneous nature of the bifunctional ca-
talysis was corroborated by Hg drop experiments,[19] which
Figure 6. Time profile of the base-free 1,4-Michael-type activated
C–H addition of a representative substrate (5) across a representa-
showed comparable reaction yields (63–95%) and ee values
tive α,β-unsaturated substrate, methyl vinyl ketone (7), as catalyzed
(3–75%) for the menthol derivative (1d) to those without
by 1d.
Hg (Table S1).
A substrate variation study for the Michael addition to
methyl vinyl ketone (7) revealed that both the reaction yield
and the ee decreased as the steric bulk increased from ethyl
Conclusions
2-cyanopropanoate (4) to isopropyl 2-cyanopropanoate (5)
A series of menthol-, pinene-, and camphor-derived chi-
and tert-butyl 2-cyanopropanoate (6) owing to the decrease ral amido-functionalized N-heterocyclic carbene nickel
in reaction rate on account of the increase in substrate bulk complexes 1d–3d were effectively designed for the bifunc-
(Table 3, Entries 1–3). However, for the Michael addition tional catalysis of the Michael addition reaction under
to acrylonitrile (8), a similar decrease in reaction yield was base-free conditions. Though all of the complexes success-
observed as the steric bulk increased, but an opposing trend fully catalyzed the base-free Michael addition reaction of a
was observed for the ee (Table 3, Entries 4–6).
representative ethyl 2-cyanopropanoate (4) substrate to the
The influence of the N-heterocyclic carbene ligands in activated olefinic substrate methyl vinyl ketone (7) under
the bifunctional catalysis can be gauged from control and ambient conditions at room temperature, only the menthol
blank experiments, which showed significant enhancements derivative 1d exhibited chiral induction. The distant loca-
of the reaction yields of up to 95% and the ee values of up tion of the chiral auxiliaries from the metal center as a re-
to 75% for the menthol derivative (1d) for the reactions of sult of the cis geometries of 1d–3d has been suggested as
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(m), 792 (m), 667 (s), 577 (m), 567 (m), 557 (m) cm–1. [α]2D5 = –63.9
(c = 1.00, CHCl3); ref.[20a] [α]2D0 = –72.8 (c = 6.04, CHCl3); ref.[20b]
[α]D = –66.6 (c = 0.08, CH2Cl2).
the possible cause for the observation of moderate-to-good
ee values (2–75%) for the menthol derivative 1d and no chi-
ral induction for the pinene (2d) and camphor (3d) com-
plexes.
1-(1S)-Menthylimidazole (1b): To a solution of imidazole (13.2 g,
194 mmol) in dry N,N-dimethylformamide (DMF, ca. 120 mL), so-
dium hydride (5.41 g, 225 mmol) was added portionwise at 0 °C
under a nitrogen atmosphere. The mixture was stirred for 15 min
at the same temperature, and then (1R,2S,5R)-2-isopropyl-5-meth-
ylcyclohexyl-p-toluenesulfonate (1a) (20.0 g, 64.4 mmol) was added
in one portion to the reaction mixture under an inert atmosphere.
The reaction mixture was warmed to room temperature and then
heated to reflux for 24 h, after which it was poured into cold water
(ca. 300 mL). The crude product was extracted with ethyl acetate
(ca. 3ϫ 200 mL). The organic layers were collected and repeatedly
washed with water (ca. 5ϫ 50 mL) followed by a saturated sodium
chloride solution (ca. 50 mL). The organic extract was finally dried
with anhydrous MgSO4 and filtered, and the volatiles were removed
in vacuo. The crude product was purified by column chromatog-
raphy (silica, petroleum ether/EtOAc 95:5–20:80) to give the prod-
uct (1b) as a white solid (3.83 g, 29%). 1H NMR (CDCl3,
400 MHz, 25 °C): δ = 7.69 (s, 1 H, NCHN), 7.08 (s, 1 H,
Experimental Section
General Procedures: All manipulations were performed by standard
Schlenk techniques. NiCl2·6H2O was purchased from SD Fine
Chemicals, India and used without any further purification. (1R)-
(–)-Menthol, (1R)-(+)-camphor, ethyl 2-cyanoacetate, isopropyl 2-
cyanoacetate, and tert-butyl 2-cyanoacetate were purchased from
Sigma–Aldrich. (1S)-(–)Pinene was purchased from TCI chemicals,
Japan. Methyl vinyl ketone was purchased from Avra Synthesis,
India. (1R,2S,5R)-2-Isopropyl-5-methylcyclohexyl p-toluenesulfon-
ate (1a),[20] 2,6,6-trimethylbicyclo[3.1.1]heptan-3-amine (2a),[21] and
exo-(–)-bornylamine (3a)[22] were synthesized by modified literature
procedures. 1H and 13C{1H} NMR spectra were recorded with a
1
Bruker 400 MHz NMR spectrometer. H NMR peaks are labeled
as singlet (s), doublet (d), triplet (t), quartet (q), septet (sept), doub-
let of triplets (dt), triplet of doublets (td), doublet of doublets (dd),
and broad (br). Infrared spectra were recorded with a Perkin–El-
mer Spectrum One FTIR spectrometer. Mass spectrometry mea-
surements were performed with a Bruker maxis impact spectrome-
ter. Elemental analysis was performed with a Thermo Quest
FLASH 1112 SERIES (CHNS) elemental analyzer. Specific optical
rotations were measured with a JASCO P-2000 polarimeter. The
enantiomeric excesses were determined by GC with a CP-Chirasil-
Dex CB chiral column (30 m, 0.25 mm) from Agilent Technologies.
The X-ray diffraction data were refined by full-matrix least-square
procedures on F2 with SHELXTL.[23]
NCHCHN), 7.06 (s,
CH3C7H10(CH3)2], 1.97–1.86 [m, 3 H, CH3C7H10(CH3)2], 1.79–
1.67 [m, H, CH3C7H10(CH3)2], 1.49–1.28 [m, H,
1 H, NCHCHN), 4.55 [br, 1 H,
1
3
CH3C7H10(CH3)2], 1.25–1.15 [m, 1 H, CH3C7H10(CH3)2], 1.09–
3
1.01 [m, 1 H, CH3C7H10(CH3)2], 0.88 (d, JH,H = 7 Hz, 3 H, CH3),
3
3
0.84 (d, JH,H = 7 Hz, 3 H, CH3), 0.78 (d, JH,H = 7 Hz, 3 H,
CH3) ppm. 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ = 138.0
(NCHN), 128.5 (NCHCHN), 120.3 (NCHCHN), 55.7
[CH3C7H10(CH3)2], 46.5 [CH3C7H10(CH3)2], 41.8 [CH3C7H10-
(CH3)2], 34.4 [CH3C7H10(CH3)2], 29.2 [CH3C7H10(CH3)2], 26.8
[CH3C7H10(CH3)2], 25.5 [CH3C7H10(CH3)2], 22.5 (CH3), 21.4
(CH ), 20.5 (CH ) ppm. IR (KBr pellet): ν = 3104 (w), 2949 (s),
CCDC-840498 (for 1d), -983559 (for 2d), and -978971 (for 3d) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
˜
3
3
2915 (s), 2868 (s), 2840 (s), 1682 (w), 1658 (w), 1585 (w), 1509 (m),
1492 (m), 1475 (m), 1453 (s), 1429 (m), 1388 (m), 1368 (m), 1292
(m), 1282 (m), 1255 (m), 1226 (s), 1214 (m), 1192 (m), 1112 (m),
1082 (s), 1066 (m), 1035 (m), 905 (m), 830 (s), 732 (s), 671 (s) cm–1.
HRMS (ES): calcd. for C13H23N2 [M + H]+ 207.1856; found
207.1837. C13H22N2 (206.33): calcd. C 75.68, H 10.75, N 13.58;
found C 74.76, H 10.05, N 12.86. [α]2D5 = +42.1 (c = 1.00, CHCl3).
(1R,2S,5R)-2-Isopropyl-5-methylcyclohexyl p-Toluenesulfonate (1a):
To a stirred solution of (1R,2S,5R)-2-isopropyl-5-methylcyclohexa-
nol (1.56 g, 10.0 mmol) in pyridine (ca. 10 mL), p-toluenesulfonyl
chloride (2.86 g, 15.0 mmol) was added in one portion at 0 °C, and
the mixture was stirred at the same temperature for 1 h, after which
it was further stirred at room temperature overnight. Upon the ad-
dition of cold water (ca. 50 mL), a white solid precipitated; the
solid was collected by filtration and dried in vacuo. The crude prod-
uct was purified by column chromatography (silica, petroleum
1-(1S)-Menthyl-3-[N-(phenylacetamido)]imidazolium Chloride (1c):
To a stirred solution of 1b (2.50 g, 12.1 mmol) in CH3CN (ca.
30 mL), 2-chloro-N-phenylacetamide (2.26 g, 13.3 mmol) was
added in one portion, and the reaction mixture was heated to reflux
for 24 h. The white crystalline solid that was observed during the
course of reaction was isolated by filtration. The crude product was
ether/EtOAc 98:2–95:5) to give the product (1a) as a white crystal-
1
line solid (2.85 g, 92%). H NMR (CDCl3, 400 MHz, 25 °C): δ = washed with cold CH3CN (ca. 3ϫ 10 mL) and dried in vacuo to
3
3
7.79 [d, 2 H, JH,H = 8 Hz, C6H4(CH3)], 7.32 [d, 2 H, JH,H
=
give the pure product (1c) as a white crystalline solid (3.83 g, 84%).
3
3
8 Hz, C6H4(CH3)], 4.39 [td, 1 H, JH,H = 11 Hz, JH,H = 5 Hz,
1H NMR (CDCl3, 400 MHz, 25 °C): δ = 11.46 (s, 1 H, NCHN),
3
CH3C7H10(CH3)2], 2.44 [s, 3 H, C6H4(CH3)], 2.16–2.11 [m, 1 H, 10.10 (s, 1 H, NH), 7.75 (d, JH,H = 8 Hz, 2 H, C6H5), 7.58 (s, 1
CH3C7H10(CH3)2], 1.94–1.83 [m, 1 H, CH3C7H10(CH3)2], 1.68– H, NCHCHN), 7.28–7.22 (m, 3 H, C6H5 and NCHCHN), 7.05 (t,
2
1.63 [m, 2 H, CH3C7H10(CH3)2], 1.46–0.77 [m, 5 H, CH3C7H10- 3JH,H = 7 Hz, 1 H, C6H5), 5.68 (d, AB system, JH,H = 16 Hz, 1
3
3
2
(CH3)2], 0.88 (d, 3 H, JH,H = 7 Hz, CH3), 0.83 (d, 3 H, JH,H
=
H, NCH2), 5.63 (d, AB system, JH,H = 16 Hz, 1 H, NCH2), 4.81
7 Hz, CH3), 0.51 (d, 3 H, JH,H = 7 Hz, CH3). 13C{1H}NMR [br, 1 H, CH3C7H10(CH3)2], 2.02–1.95 [m, 3 H, CH3C7H10(CH3)2],
(CDCl3, 100 MHz, 25 °C): 144.5 [C6H4(CH3)], 134.9 1.71–1.66 [m, H, CH3C7H10(CH3)2], 1.56–1.39 [m, H,
[C6H4(CH3)], 129.8 [2ϫC6H4(CH3)], 127.8 [2ϫC6H4(CH3)], 83.8 CH3C7H10(CH3)2], 1.24–1.16 [m, 1 H, CH3C7H10(CH3)2], 1.08–
3
δ
=
1
3
3
[CH3C7H10(CH3)2],
[CH3C7H10(CH3)2],
[CH3C7H10(CH3)2],
47.7
33.9
25.6
[CH3C7H10(CH3)2],
[CH3C7H10C(CH3)2],
[CH3C7H10(CH3)2],
42.1 0.98 [m, 1 H, CH3C7H10(CH3)2], 0.91 (d, JH,H = 6 Hz, 3 H, CH3),
31.8 0.87 (d, 3JH,H = 7 Hz, 3 H, CH3), 0.82 (d, 3JH,H = 7 Hz, 3 H, CH3)
23.1 ppm. 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ = 163.1 (NCO),
[CH3C7H10(CH3)2], 22.0 (CH3), 21.8 (CH3), 21.0 (CH3), 15.4 138.1 (NCHN), 137.9 (C6H5), 128.6 (C6H5), 124.2 (C6H5), 123.1
(CH ). IR (KBr pellet): ν = 2965 (m), 2937 (m), 2869 (m), 2856 (NCHCHN), 122.2 (NCHCHN), 120.1 (C6H5), 59.9
[CH3C7H10(CH3)2], 52.3 (NCH2), 45.7 [CH3C7H10(CH3)2], 40.3
1178 (s), 1099 (m), 943 (m), 913 (s), 885 (m), 873 (m), 830 (m), 815 [CH3C7H10(CH3)2], 33.6 [CH3C7H10(CH3)2], 28.9 [CH3C7H10-
˜
3
(m), 1599 (m), 1496 (w), 1454 (m), 1357 (s), 1292 (w), 1189 (m),
Eur. J. Inorg. Chem. 2015, 1604–1615
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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FULL PAPER
(CH3)2], 26.0 [CH3C7H10(CH3)2], 24.6 [CH3C7H10(CH3)2], 22.0 washed with CHCl3, dried under vacuum, and basified with NaOH
(CH ), 21.2 (CH ), 20.4 (CH ) ppm. IR (KBr pellet): ν = 3227 (w), solution until the pH was above 12. The pure product was extracted
˜
3
3
3
3184 (m), 3122 (m), 3064 (s), 2959 (s), 2872 (m), 1694 (s), 1602 (m), with diethyl ether (ca. 3ϫ50 mL), and the combined organic layers
1556 (s), 1498 (m), 1446 (m), 1362 (m), 1317 (m), 1269 (m), 1176 were washed with brine (ca. 2ϫ20 mL), dried with anhydrous
(m), 1155 (m), 1139 (m), 1030 (w), 976 (w), 906 (w), 869 (w), 759 Na2SO4, filtered, and concentrated in vacuo to afford the product
(m), 693 (m), 675 (w), 632 (w) cm–1. HRMS (ES): calcd. for
(2a) as a colorless liquid (3.54 g, 23%). 1H NMR (CDCl3,
C21H30N3O [M – Cl]+ 340.2383; found 340.2382. C21H30ClN3O 400 MHz, 25 °C): δ = 3.13–3.07 [m, 1 H, CH3C6H8C(CH3)2], 2.47–
(375.94): calcd. C 67.09, H 8.04, N 11.18; found C 67.10, H 7.75,
2.40 [m,
1
H, CH3C6H8C(CH3)2], 2.38–2.32 [m,
1
H,
N 10.60. [α]2D5 = +12.5 (c = 1.00, CHCl3).
CH3C6H8C(CH3)2], 1.95–1.90 [m, 1 H, CH3C6H8C(CH3)2], 1.82–
1.67 [m, 4 H, CH3C6H8C(CH3)2 and NH2], 1.54–1.48 [m, 1 H,
CH3C6H8C(CH3)2], 1.20 [s, 3 H, CH3C6H8C(CH3)2], 1.09 [d, 3JH,H
= 7 Hz, 3 H, CH3C6H8C(CH3)2], 0.96 [s, 3 H, CH3C6H8C(CH3)2],
{1-(1S)-Menthyl-3-[N-(phenylacetamido)]imidazol-2-ylidene}2Ni
(1d): A mixture of 1c (0.500 g, 1.33 mmol), NiCl2·6H2O (0.158 g,
0.665 mmol), and K2CO3 (0.367 g, 2.66 mmol) in CH3CN (ca.
30 mL) was heated under reflux for 36 h. The reaction mixture was
filtered, and the volatiles were reduced in vacuo to a minimum
volume (ca. 8 mL). Upon standing in air for 10 h, the pure product
crystallized from the mother liquor as yellow crystals. The crystals
were isolated by filtration and vacuum dried to yield the product
(1d) as a yellow crystalline solid (0.176 g, 36%). Single crystals suit-
able for X-ray diffraction studies were grown from CH3CN by slow
evaporation. 1H NMR (CDCl3, 400 MHz, 25 °C): δ = 7.29 (d,
3
0.90 [d, JH,H = 10 Hz, 1 H, CH3C6H8C(CH3)2] ppm. 13C{1H}
NMR (CDCl3, 100 MHz, 25 °C): δ = 50.8 [CH3C7H8(CH3)2], 48.8
[CH3C7H8(CH3)2], 48.2 [CH3C7H8(CH3)2], 42.1 [CH3C7H8(CH3)2],
39.7
[CH3C7H8(CH3)2],
38.4
[CH3C7H8(CH3)2],
35.1
[CH3C7H(CH3)2], 28.1 (CH3), 23.4 (CH3), 21.0 (CH3) ppm. HRMS
(ES): calcd. for C10H20N [M + H]+ 154.1590; found 154.1595.
[α]2D5 = +32.1 (c = 1.00, CHCl3).
1-[(1S)-Pinan-3-yl]imidazole (2b): To a mixture of 2a (2.00 g,
13.0 mmol) in H2O (ca. 5 mL), H3PO4 (85%) was added until the
pH was ca. 2. Paraformaldehyde (0.390 g, 13.0 mmol), glyoxal
(0.757 g, 13.0 mmol), and H2O (ca. 5 mL) were added, and the re-
action mixture was heated to 80 °C. Then, a saturated solution of
3
3JH,H = 8 Hz, 4 H, 2ϫC6H5), 7.11 (d, JH,H = 1 Hz, 2 H,
2ϫNCHCHN), 7.02 (d, 3JH,H = 1 Hz, 2 H, 2ϫ NCHCHN), 6.94–
6.91 (m, 4 H, 2ϫC6H5), 6.78 (t, 3JH,H = 7 Hz, 2 H, 2ϫC6H5), 5.91
2
(d, AX system, JH,H = 15 Hz, 2 H, 2ϫNCH2), 4.60 (d, AX sys-
2
tem, JH,H
= 15 Hz, 2 H, 2ϫNCH2), 4.10 [br, 2 H, 2ϫ NH4Cl (0.696 g, 13.0 mmol) in H2O (ca. 5 mL) was added dropwise
CH3C7H10(CH3)2], 2.17 [br, 2 H, 2ϫ CH3C7H10(CH3)2], 1.94–1.50
[m, 10 H, 2ϫ CH3C7H10(CH3)2], 1.32–1.05 [m, H, 2ϫ
over 10 min. The reaction mixture was then heated at 100 °C for
6 h, after which it was cooled to 0 °C, and a solution of NaOH in
H2O was added until the pH was above 12. The product was ex-
tracted with CHCl3 (ca. 3ϫ30 mL), and the combined organic lay-
ers were washed with brine (ca. 2ϫ20 mL), dried with anhydrous
6
3
CH3C7H10(CH3)2], 0.86 (d, JH,H = 6 Hz, 6 H, 2ϫCH3), 0.77 (d,
3
3JH,H = 6 Hz, 6 H, 2ϫCH3), 0.54 (d, JH,H = 6 Hz, 6 H, 2ϫCH3)
ppm. 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ = 167.1 (CO),
166.2 (NCN), 146.4 (C6H5), 126.2 (C6H5), 126.0 (C6H5), 122.0 Na2SO4, filtered, and concentrated in vacuo. The product was puri-
(NCHCHN), 121.6 (NCHCHN), 120.7 (C6H5), 58.7 (NCH2), 58.0 fied by column chromatography (silica, petroleum ether/EtOAc
[CH3C7H10(CH3)2], 47.0 [CH3C7H10(CH3)2], 36.6 [CH3C7H10- 100:0–20:80) to give the product 2b as a thick light yellow liquid
1
(CH3)2], 31.3 [CH3C7H10(CH3)2], 28.3 [CH3C7H10(CH3)2], 26.8 (0.650 g, 24%). H NMR (CDCl3, 400 MHz, 25 °C): δ = 7.72 (br,
[CH3C7H10(CH3)2], 23.1 [CH3C7H10(CH3)2], 22.7 (CH3), 21.4 1 H, NCHN), 7.12 (s, 1 H, NCHCHN), 7.05 (s, 1 H, NCHCHN),
(CH ), 19.3 (CH ) ppm. IR (KBr pellet): ν = 3170 (w), 3131 (w), 4.45–4.39 [m,
3082 (w), 2956 (s), 2923 (s), 2868 (s), 1604 (s), 1580 (s), 1563 (s),
1
H, CH3C6H8C(CH3)2], 2.66–2.53 [m,
CH3C6H8C(CH3)2], 2.25–2.18 [m, 1 H, CH3C6H8C(CH3)2], 2.09–
1486 (s), 1445 (m), 1415 (m), 1363 (s), 1297 (m), 1234 (m), 1168 2.00 [m, H, CH3C6H8C(CH3)2], 1.95–1.92 [m, H,
2 H,
˜
3
3
2
1
(m), 1108 (w), 1072 (w), 971 (w), 869 (w), 798 (w), 751 (s), 688 (s), CH3C6H8C(CH3)2], 1.29 [s, 3 H, CH3C6H8C(CH3)2], 1.13 [d, 3JH,H
532 (m) cm–1. HRMS (ES): calcd. for C42H56N6NiO2 [M]+
=
10 Hz,
1
H, CH3C6H8C(CH3)2], 1.09–1.07 [m,
6
H,
734.3813; found 734.3808. C42H56N6NiO2·4H2O (807.7): calcd. C
CH3C6H8C(CH3)2 and CH3C6H8C(CH3)2] ppm. 13C{1H} NMR
(CDCl3, 100 MHz, 25 °C): δ = 137.0 (NCHN), 130.0 (NCHCHN),
117.1 (NCHCHN), 57.2 [CH3C7H8(CH3)2], 47.5 [CH3C7H8-
(CH3)2], 45.8 [CH3C7H8(CH3)2], 41.5 [CH3C7H8(CH3)2], 38.9
[CH3C7H8(CH3)2], 37.2 [CH3C7H8(CH3)2], 35.1 [CH3C7H8(CH3)2],
28.0 (CH3), 23.5 (CH3), 20.5 (CH3) ppm. HRMS (ES): calcd. for
C13H21N2 [M + H]+ 205.1699; found 205.1703. [α]2D5 = +11.9 (c =
1.00, CHCl3).
62.46, H 7.99, N 10.41; found C 62.47, H 7.45, N 10.98. [α]2D5
–260 (c = 1.00, CHCl3).
=
2,6,6-Trimethylbicyclo[3.1.1]heptan-3-amine (2a): To a stirred solu-
tion of (S)-(–)pinene (13.6 g, 100 mmol) in dry THF (ca. 50 mL),
BH3·SMe2 complex (5.16 mL) was added at 0 °C under a nitrogen
atmosphere. The resulting solution was allowed to stand for 24 h
at the same temperature for crystallization, after which the super-
natant liquid was removed with a cannula. The white crystalline
solid was broken up with a needle, washed with precooled dry di-
ethyl ether (ca. 3ϫ10 mL), and then dried in vacuo. The reaction
flask was cooled to 0 °C, the apparatus was flushed with nitrogen,
and a suspension of (aminooxy)sulfonic acid (11.3 g, 100 mmol)
in bis(2-methoxyethyl) ether (ca. 40 mL) was added at the same
temperature. The reaction mixture was stirred at room temperature
for 1 h and then heated at 100 °C for 3 h, after which it was cooled
to 0 °C and acidified with concentrated HCl (ca. 100 mL). The vol-
atiles were removed in vacuo to afford a thick crude mixture, which
was basified with NaOH solution until the pH was above 12. The
crude product was extracted with diethyl ether (ca. 3ϫ50 mL), and
the combined organic layers were collected and concentrated in
vacuo. The crude product was further acidified with H3PO4 (85%)
to afford a white solid, which was collected by vacuum filtration,
1-[(1S)-Pinan-3-yl]-3-[N-(phenylacetamido)]imidazolium
Chloride
(2c): 2-chloro-N-phenylacetamide (0.745 g, 4.39 mmol) was added
to a stirred solution of 2b (0.897 g, 4.39 mmol) in CH3CN (ca.
25 mL). The reaction mixture was heated under reflux for 24 h,
after which the volatiles were removed in vacuo. The crude product
was purified by column chromatography (silica, CHCl3/CH3OH
100:0–85:15) to give the product 2c as a light brown solid (1.39 g,
85%). 1H NMR (CDCl3, 400 MHz, 25 °C): δ = 11.46 (s, 1 H,
3
NCHN), 10.15 (s, 1 H, NH), 7.76 (d, JH,H = 8 Hz, 2 H, C6H5),
7.66 (s, 1 H, NCHCHN), 7.28–7.22 (m, 3 H, NCHCHN and
C6H5), 7.05 (t, 3JH,H = 7 Hz, 1 H, C6H5), 5.69 (d, AB system, 2JH,H
2
= 16 Hz, 1 H, NCH2), 5.64 (d, AB system, JH,H = 16 Hz, 1 H,
NCH2), 4.84–4.77 [m, 1 H, CH3C6H8C(CH3)2], 2.78–2.71 [m, 1 H,
CH3C6H8C(CH3)2], 2.62–2.57 [m, 1 H, CH3C6H8C(CH3)2], 2.24–
2.21 [m,
1
H, CH3C6H8C(CH3)2], 2.11–1.94 [m,
3
H,
Eur. J. Inorg. Chem. 2015, 1604–1615
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FULL PAPER
3
CH3C6H8C(CH3)2], 1.29 [s, 3 H, CH3C6H8C(CH3)2], 1.14 [d, 3JH,H 12 Hz, JH,H = 4 Hz, 1 H, CH3C6H7C(CH3)2], 1.49–1.43 [m, 1 H,
3
= 7 Hz, 3 H, CH3C6H8C(CH3)2], 1.11 [d, JH,H = 10 Hz, 1 H, CH3C6H7C(CH3)2], 1.27–1.21 [m, 1 H, CH3C6H7C(CH3)2], 1.02 (s,
CH3C6H8C(CH3)2], 1.07 [s, 3 H, 2ϫ CH3C6H8C(CH3)2] ppm. 3 H, CH3), 0.92 (s, 3 H, CH3), 0.80 (s, 3 H, CH3) ppm.
13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ = 163.2 (NCO), 138.1 13C{1H}NMR (CDCl3, 100 MHz, 25 °C): δ = 170.1 (CNOH), 52.0
(NCHN), 137.3 (C6H5), 128.6 (C6H5), 124.5 (C6H5), 124.2 [CH3C7H7(CH3)2], 48.5 [CH3C7H7C(CH3)2], 43.9 [CH3C7H7-
(NCHCHN), 120.1 (C6H5), 119.2 (NCHCHN), 60.4 (NCH2), 52.3 (CH3)2], 33.3 [CH3C7H7(CH3)2], 32.8 [CH3C7H7(CH3)2], 27.4
[CH3C7H8(CH3)2], 47.1 [CH3C7H8(CH3)2], 45.2 [CH3C7H8(CH3)2], [CH3C7H7(CH3)2], 19.6 (CH3), 18.7 (CH3), 11.3 (CH3) ppm. [α]2D5
41.1 [CH3C7H8(CH3)2], 38.7 [CH3C7H8(CH3)2], 36.4 [CH3C7H8- = –37.3 (c = 1.00, EtOH); ref.[22] [α]2D5 = –37.5 (c = 1.00, EtOH).
(CH3)2], 35.0 [CH3C7H8(CH3)2], 27.7 (CH3), 23.4 (CH3), 20.2
exo-(–)-Bornylamine (3a): NaBH4 (2.27 g, 60.0 mmol) was added
portionwise to solution of (1R)-camphor oxime (3.34 g,
(CH ) ppm. IR (KBr pellet): ν = 3190 (w), 3130 (w), 3060 (m),
˜
3
a
2922 (m), 2874 (m), 1698 (s), 1602 (m), 1553 (s), 1499 (m), 1446
(m), 1368 (w), 1313 (m), 1257 (m), 1165 (m), 1030 (w), 952 (w),
905 (w), 851 (w), 756 (s), 693 (m), 653 (w), 627 (w) cm–1. HRMS
(ES): calcd. for C21H28N3O [M – Cl]+ 338.2227; found 338.2227.
C21H28ClN3O (373.92): calcd. C 67.45, H 7.55, N 11.24; found C
67.21, H 6.66, N 10.97. [α]2D5 = +2.52 (c = 1.00, CHCl3).
20.0 mmol) and NiCl2 (5.18 g, 40.0 mmol) in anhydrous MeOH
(ca. 60 mL) at –60 °C over a period of 2 h. After completion of the
addition, the resulting black slurry was warmed to –30 °C and
stirred at this temperature for another 4 h. The reaction mixture
was then warmed to room temperature, and 25% ammonia solu-
tion (ca. 10 mL) in H2O (ca. 30 mL) was added with vigorous stir-
ring. The resulting slurry was extracted with Et2O (ca. 3ϫ100 mL),
and the combined organic layers were washed with brine (ca.
2ϫ20 mL), dried with anhydrous Na2SO4, filtered, and concen-
trated in vacuo. The crude product was purified by column
chromatography (silica, CH2Cl2/CH3OH 100:0–90:10) to afford
exo-(–)-bornylamine (3a) as a foamy white solid (0.682 g, 33%
{1-[(1S)-Pinan-3-yl]-3-[N-(phenylacetamido)]imidazol-2-ylidene}2Ni
(2d): A mixture of 2c (1.23 g, 3.29 mmol), NiCl2·6H2O (0.469 g,
1.97 mmol), and K2CO3 (1.36 g, 9.84 mmol) in CH3CN (ca. 30 mL)
was heated under reflux for 36 h. The reaction mixture was filtered,
and the volatiles were removed in vacuo. The crude product was
purified by column chromatography (basic alumina, CHCl3/
CH3OH 100:0–98:2) to give the product (2d) as a yellow solid
(0.410 g, 34%). Single crystals suitable for X-ray diffraction studies
were grown from a mixture of CH3CN and CH3OH by slow evapo-
1
3
yield). H NMR (CDCl3, 400 MHz, 25 °C): δ = 2.70 [dd, JH,H
=
3
9 Hz, JH,H = 5 Hz, 1 H, CH3C6H8C(CH3)2], 1.77–1.63 [m, 3 H,
CH3C6H8C(CH3)2], 1.57–1.47 [m, 2 H, CH3C6H8C(CH3)2], 1.36
(br, 2 H, NH2), 1.11–0.98 [m, 2 H, CH3C6H8C(CH3)2], 0.97 (s, 3
H, CH3), 0.87 (s, 3 H, CH3), 0.81 (s, 3 H, CH3) ppm. 13C{1H}
NMR (CDCl3, 100 MHz, 25 °C): δ = 60.1 [CH3C7H8(CH3)2], 47.7
[CH3C7H8(CH3)2], 46.3 [CH3C7H8(CH3)2], 44.7 [CH3C7H8(CH3)2],
1
3
ration. H NMR (CDCl3, 400 MHz, 25 °C): δ = 7.24 (d, JH,H
=
3
7 Hz, 4 H, 2ϫC6H5), 7.14 (br, 2 H, 2ϫ NCHCHN), 6.92 (t, JH,H
= 8 Hz, 4 H, 2ϫC6H5), 6.91 (br, 2 H, 2ϫ NCHCHN), 6.79 (t,
3JH,H = 7 Hz, 2 H, 2ϫC6H5), 5.90 (d, AX system, JH,H = 16 Hz,
2
2 H, 2ϫNCH2), 4.62–4.56 [m, 2 H, 2ϫ CH3C6H8C(CH3)2], 4.51
(d, AX system, 2JH,H = 16 Hz, 2 H, 2ϫNCH2), 2.55–2.50 [m, 2 H,
2CH3C6H8C(CH3)2], 2.06–1.92 [m, 6 H, 2CH3C6H8C(CH3)2], 1.68–
40.3
[CH3C7H8(CH3)2],
36.1
[CH3C7H8(CH3)2],
27.0
[CH3C7H8(CH3)2], 20.6 (CH3), 20.0 (CH3), 11.6 (CH3) ppm.
HRMS (ESI): calcd. for C10H20N [M + H]+ 154.1590; found
154.1592. [α]2D5 = –49.0 (c = 1.80 in EtOH); ref.[22] [α]2D5 = –48.5 (c
= 1.80, EtOH).
3
1.63 [m, 2 H, 2ϫ CH3C6H8C(CH3)2], 1.53 [d, JH,H = 7 Hz, 6 H,
2ϫ CH3C6H8C(CH3)2], 1.46–1.40 [m, 2 H, 2ϫ CH3C6H8C-
(CH3)2], 1.30 [s, 6 H, 2ϫ CH3C6H8C(CH3)2], 1.05 [s, 6 H, 2ϫ
3
CH3C6H8C(CH3)2], 0.95 [d, JH,H
=
10 Hz,
2
H, 2ϫ
1-(1R)-Isobornylimidazole (3b): To
a mixture of exo-(–)-bor-
CH3C6H8C(CH3)2] ppm. 13C{1H} NMR (CDCl3, 100 MHz,
25 °C): δ = 167.6 (CO), 167.2 (NCN), 146.3 (C6H5), 126.5 (C6H5),
126.2 (C6H5), 123.7 (C6H5), 122.0 (NCHCHN), 117.9
(NCHCHN), 60.5 (CH2), 57.7 [CH3C7H8(CH3)2], 47.5
[CH3C7H8(CH3)2], 46.0 [CH3C7H8(CH3)2], 41.2 [CH3C7H8(CH3)2],
nylamine (3a) (0.750 g, 4.89 mmol) in H2O (ca. 5 mL), H3PO4
(85%) was added until the pH was ca. 2. Paraformaldehyde
(0.147 g, 4.89 mmol), glyoxal (0.284 g, 4.89 mmol), and H2O (ca.
5 mL) were added, and the reaction mixture was heated to 80 °C.
A saturated solution of NH4Cl (0.262 g, 4.89 mmol) in H2O (ca.
2 mL) was then added dropwise over 10 min. The reaction mixture
was then heated at 100 °C for 6 h, after which it was cooled to 0 °C,
and a solution of NaOH in H2O was added until the pH was above
12. The product was extracted with CHCl3 (ca. 3ϫ30 mL), and
the combined organic layers were washed with brine (ca.
2ϫ20 mL), dried with anhydrous Na2SO4, filtered, and concen-
trated in vacuo. The product was purified by column chromatog-
raphy (silica, CH2Cl2/CH3OH 100:0–95:5) to give the product (3b)
as a thick light yellow liquid (0.245 g, 25%). 1H NMR (CDCl3,
39.0
[CH3C7H8(CH3)2],
36.4
[CH3C7H8(CH3)2],
35.3
[CH3C7H8(CH3)2], 28.0 (CH3), 22.9 (CH3), 21.6 (CH3) ppm. IR
(KBr pellet): ν = 2956 (m), 2919 (m), 1603 (s), 1583 (s), 1568 (s),
˜
1486 (m), 1448 (m), 1423 (m), 1366 (m), 1300 (w), 1269 (w), 1235
(w), 1219 (m), 1171 (w), 1104 (w), 1028 (w), 968 (w), 805 (w), 781
(w), 755 (m), 734 (m), 692 (m), 535 (m) cm–1. C42H52N6NiO2·H2O
(749.6): calcd. C 67.29, H 7.26, N 11.21; found C 66.80, H 6.63, N
11.15. HRMS (ES): calcd. for C42H53N6NiO2 [M + H]+ 731.3578;
found 731.3578. [α]2D5 = –170 (c = 1.00, CHCl3).
(1R)-Camphor Oxime: A mixture of (R)-(+)-camphor (20.0 g, 400 MHz, 25 °C): δ = 7.53 (s, 1 H, NCHN), 6.97 (s, 1 H,
3
131 mmol), hydroxylamine hydrochloride (14.6 g, 210 mmol), and
water (ca. 70 mL) was heated to 80 °C, and MeOH (ca. 70 mL)
was added to dissolve the camphor. A solution of NaOAc (26.9 g,
328 mmol) in water (ca. 50 mL) was added, and the reaction mix-
ture was heated under reflux at 100 °C for 12 h. Upon removal of
the methanol in vacuo, the white solid that precipitated was col-
NCHCHN), 6.95 (s, 1 H, NCHCHN), 4.04 [q, JH,H = 7 Hz, 1 H,
CH3C6H8C(CH3)2], 2.36–2.29 [m, 1 H, CH3C6H8C(CH3)2], 1.96–
1.87 [m,
2
H, CH3C6H8C(CH3)2], 1.84–1.77 [m,
1
H,
CH3C6H8C(CH3)2], 1.69–1.61 [m, 1 H, CH3C6H8C(CH3)2], 1.25–
1.17 [m, 2 H, CH3C6H8C(CH3)2], 0.89 (s, 3 H, CH3), 0.85 (s, 3 H,
CH3), 0.78 (s, 3 H, CH3) ppm. 13C{1H} NMR (CDCl3, 100 MHz,
lected by vacuum filtration, washed with water (ca. 3ϫ100 mL), 25 °C): δ = 137.0 (NCHN), 128.0 (NCHCHN), 119.1 (NCHCHN),
and dried in vacuo to afford the pure product (20.4 g, 93%). 1H
65.3
[CH3C7H8(CH3)2],
49.9
[CH3C7H8(CH3)2],
46.8
NMR (CDCl3, 400 MHz, 25 °C): δ = 2.57 [dt, 2JH,H = 18 Hz, 3JH,H
[CH3C7H8(CH3)2], 44.6 [CH3C7H8(CH3)2], 37.1 [CH3C7H8(CH3)2],
2
= 4 Hz, 1 H, CH3C6H7C(CH3)2], 2.07 [d, JH,H = 18 Hz, 1 H, 35.4 [CH3C7H8(CH3)2], 26.5 [CH3C7H8(CH3)2], 20.9 (CH3), 19.7
3
CH3C6H7C(CH3)2], 1.93 [t, JH,H = 4 Hz, 1 H, CH3C6H7C-
(CH3), 12.5 (CH3) ppm. HRMS (ESI): calcd. for C13H21N2 [M +
2
(CH3)2], 1.89–1.80 [m, 1 H, CH3C6H7C(CH3)2], 1.71 [td, JH,H
=
H]+ 205.1699; found 205.1702. [α]2D5 = –85.7 (c = 1.00, CHCl3).
Eur. J. Inorg. Chem. 2015, 1604–1615
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FULL PAPER
1-(1R)-Isobornyl-3-[N-(phenylacetamido)]imidazolium Chloride (3c): cyanoacetate (50 mmol) in CH3CN (ca. 100 mL), and the reaction
2-chloro-N-phenylacetamide (0.523 g, 3.08 mmol) was added to a
stirred solution of 3b (0.572 g, 2.80 mmol) in CH3CN (ca. 25 mL).
The reaction mixture was heated under reflux for 24 h, after which
the volatiles were removed in vacuo. The product was purified by
column chromatography (silica, CHCl3/CH3OH 100:0–85:15) to
give the product (3c) as a light brown solid (0.960 g, 92%). 1H
NMR (CDCl3, 400 MHz, 25 °C): δ = 11.38 (s, 1 H, NCHN), 10.14
mixture was stirred at room temperature for 15 min. CH3I (5.32 g,
37.5 mmol) was added dropwise to the reaction mixture, which was
stirred for 6 h at room temperature. The reaction mixture was fil-
tered, and the volatiles were removed in vacuo. The crude product
was then purified by column chromatography (silica, petroleum
ether/ethyl acetate 100:0–85:15) to give the corresponding methyl-
ated product.
3
(s, 1 H, NH), 7.73 (d, JH,H = 8 Hz, 2 H, C6H5), 7.56 (s, 1 H,
Ethyl 2-Cyanopropanoate (4): Colorless liquid (1.72 g, 41%). 1H
NCHCHN), 7.26–7.20 (m, 3 H, NCHCHN and C6H5), 7.06 (t,
3
NMR (CDCl3, 400 MHz, 25 °C): δ = 4.27 (q, JH,H = 7 Hz, 2 H,
2
3JH,H = 7 Hz, 1 H, C6H5), 5.67 (d, AB system, JH,H = 16 Hz, 1
3
3
CH2CH3), 3.54 (q, JH,H = 7 Hz, 1 H, CNCHCH3), 1.59 (d, JH,H
2
H, NCH2), 5.60 (d, AB system, JH,H = 16 Hz, 1 H, NCH2), 4.28–
3
= 7 Hz, 3 H, CNCHCH3), 1.33 (t, JH,H = 7 Hz, 3 H, CH2CH3)
4.24 [m,
CH3C6H8C(CH3)2], 2.10–2.00 [m, 2 H, CH3C6H8C(CH3)2], 1.88–
1.68 [m, H, CH3C6H8C(CH3)2], 1.37–1.23 [m, H,
1
H, CH3C6H8C(CH3)2], 2.50–2.43 [m,
1
H,
ppm. 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ = 166.7 (CO2),
117.5 (CN), 63.1 (CH3CH2), 31.7 (CNCHCH3), 15.4 (CH3), 14.1
(CH3) ppm.
2
2
CH3C6H8C(CH3)2], 0.93 (s, 3 H, CH3), 0.89 (s, 3 H, CH3), 0.87 (s,
3 H, CH3) ppm. 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ =
163.2 (NCO), 138.2 (NCHN and C6H5), 128.9 (C6H5), 124.5
(C6H5), 123.0 (NCHCHN), 121.4 (NCHCHN), 120.3 (C6H5), 69.2
(NCH2), 52.8 [CH3C7H8(CH3)2], 50.9 [CH3C7H8(CH3)2], 47.8
[CH3C7H8(CH3)2], 45.0 [CH3C7H8(CH3)2], 37.1 [CH3C7H8(CH3)2],
35.5 [CH3C7H8(CH3)2], 26.7 [CH3C7H8(CH3)2], 21.1 (CH3), 20.1
Isopropyl 2-Cyanopropanoate (5): Colorless liquid (1.54 g, 32%). 1H
3
NMR (CDCl3, 400 MHz, 25 °C): δ = 5.08 [sept, JH,H = 6 Hz, 1
3
H, CH(CH3)2], 3.50 (q, JH,H = 7 Hz, 1 H, CNCHCH3), 1.58 (d,
3
3JH,H = 7 Hz, 3 H, CNCHCH3), 1.30 [d, JH,H = 6 Hz, 3 H,
3
CH(CH3)2], 1.29 [d, JH,H = 6 Hz, 3 H, CH(CH3)2] ppm. 13C{1H}
NMR (CDCl3, 100 MHz, 25 °C): δ = 166.2 (CO2), 117.6 (CN), 71.1
[CH(CH3)2], 31.9 (CNCHCH3), 21.7 [CH(CH3)2], 21.6 [CH-
(CH3)2], 15.4 (CH3) ppm.
(CH ), 13.1 (CH ) ppm. IR (KBr pellet): ν = 3231 (w), 3185 (w),
˜
3
3
3066 (s), 3008 (w), 2965 (s), 2885 (m), 1702 (s), 1619 (m), 1601 (s),
1558 (s), 1500 (m), 1490 (m), 1446 (m), 1366 (w), 1308 (s), 1256 (s),
1178 (m), 1165 (m), 950 (w), 757 (s), 697 (w) cm–1. HRMS (ES):
calcd. for C21H28N3O [M – Cl]+ 338.2227; found 338.2225.
C21H28ClN3O (373.92): calcd. C 67.45, H 7.55, N 11.24; found C
67.32, H 7.52, N 10.94. [α]2D5 = –46.2 (c = 1.00, CHCl3).
tert-Butyl 2-Cyanopropanoate (6): Colorless liquid (1.66 g, 31%).
3
1H NMR (CDCl3, 400 MHz, 25 °C): δ = 3.44 (q, JH,H = 7 Hz, 1
3
H, CNCHCH3), 1.54 (d, JH,H = 7 Hz, 3 H, CNCHCH3), 1.50 [s,
9 H, C(CH3)2] ppm. 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ
= 165.7 (CO2), 117.9 (CN), 84.1 [C(CH3)2], 32.7 (CNCHCH3), 27.9
[C(CH3)2], 15.4 (CH3) ppm.
{1-(1R)-Isobornyl-3-[N-(phenylacetamido)]imidazol-2-ylidene}2Ni
(3d): A mixture of 3c (0.260 g, 0.695 mmol), NiCl2·6H2O (0.099 g,
0.417 mmol), and K2CO3 (0.288 g, 2.09 mmol) in CH3CN (ca.
30 mL) was heated under refluxed for 36 h. The reaction mixture
was filtered, and the volatiles were removed in vacuo. The crude
product was purified by column chromatography (basic alumina,
CHCl3/CH3OH 100:0–98:2) to give the product (3d) as yellow solid
(0.065 g, 26%). Single crystals suitable for X-ray diffraction studies
Computational Methods: Density functional theory (DFT) calcula-
tions were performed on 1d–3d with the GAUSSIAN 09[24] set of
programs. The Becke three-parameter exchange functional along
with the Lee–Yang-Par correlational functions (B3LYP)[25] were
used in all of the computations. The Pople split-valence double-
zeta polarized basis set 6-31G(d)[26] was used to describe carbon,
hydrogen, oxygen, and nitrogen atoms, whereas the Los Alamos
National Laboratory effective core potentials with a double-zeta
valence basis set (LANL2DZ)[27] were used for nickel. The natural
vibrational frequencies were also computed for the optimized struc-
tures to ensure that there were no negative eigenvalues in the Hess-
ian. A single negative value is indicative of a transition state,
whereas multiple negative values point towards instabilities in the
computed structure. Single-point energy calculations were per-
formed on the optimized structures in the isolated gas phase as
well as in the presence of CH3CN solvent through polarizable con-
tinuum model (PCM) studies at the same level of theory. The natu-
ral bond order (NBO)[28] analysis was performed with the NBO 3.1
program incorporated in GAUSSIAN 09.
were grown by the slow vapor diffusion of Et2O into a CHCl3 solu-
3
tion. 1H NMR (CDCl3, 400 MHz, 25 °C): δ = 7.31 (d, JH,H
=
7 Hz, 4 H, 2ϫC6H5), 7.13 (br, 2 H, 2ϫ NCHCHN), 7.06–7.02 (m,
3
6 H, 2ϫC6H5 and 2ϫ NCHCHN), 6.88 (t, JH,H = 7 Hz, 2 H,
2
2ϫC6H5), 5.83 (d, AX system, JH,H = 14 Hz, 2 H, 2ϫNCH2),
4.50 (d, AX system, 2JH,H = 14 Hz, 2 H, 2ϫNCH2), 3.80–3.76 [m,
2
H, 2ϫ CH3C6H8C(CH3)2], 1.97–1.77 [m,
8
H, 2ϫ
CH3C6H8C(CH3)2], 1.36–1.31 [m, 2 H, 2ϫ CH3C6H8C(CH3)2],
1.12–1.07 [m, 2 H, 2ϫ CH3C6H8C(CH3)2], 1.01 (s, 6 H, 2ϫ CH3),
0.99–0.90 [m, 2 H, 2ϫ CH3C6H8C(CH3)2], 0.93 (s, 6 H, 2ϫCH3),
0.83 (s, 6 H, 2ϫCH3) ppm. 13C{1H} NMR (CDCl3, 100 MHz,
25 °C): δ = 170.3 (NCN), 166.5 (CO), 146.2 (C6H5), 126.5 (C6H5),
126.4 (C6H5), 122.3 (C6H5), 122.2 (NCHCHN), 119.2
(NCHCHN), 69.1 (CH2), 57.9 [CH3C7H8(CH3)2], 50.4
[CH3C7H8(CH3)2], 46.4 [CH3C7H8(CH3)2], 44.2 [CH3C7H8(CH3)2],
General Procedure for Asymmetric Michael Addition: Compound
1d (0.0147 g, 0.02 mmol, 2 mol-%) and the α-methyl cyano ester
substrate (1.00 mmol) were stirred in chloroform (3 mL) for 5 min
till the dissolution of the catalyst occurred. A solution of the
Michael acceptor 7 or 8 (1.50 mmol) in chloroform (2 mL) was
added, and the resultant solution was stirred for 8 h at room tem-
perature. The volatiles were then removed in vacuo, and the crude
product was purified by column chromatography (silica, petroleum
ether/ethyl acetate 95:5–70:30) to give the Michael adduct. The ee
was determined by GC with a CP-Chirasil-Dex CB chiral column.
GC conditions: injection temperature 250 °C, detector temperature
300 °C, column temperature: initial temperature 60 °C, ramp 3 °C/
39.3
[CH3C7H8(CH3)2],
37.6
[CH3C7H8(CH3)2],
26.3
[CH3C7H8(CH3)2], 21.6 (CH3), 21.3 (CH3), 11.9 (CH3) ppm. IR
(KBr pellet): ν = 2955 (m), 2879 (m), 1603 (s), 1582 (s), 1569 (s),
˜
1487 (m), 1447 (m), 1419 (w), 1368 (m), 1290 (w), 1230 (m), 1169
(w), 1110 (w), 1078 (w), 970 (w), 895 (w), 755 (m), 692 (m), 534
(w) cm–1. HRMS (ES): calcd. for C42H53N6NiO2 [M + H]+
731.3578; found 731.3573. C42H52N6NiO2·H2O (749.6): calcd. C
67.29, H 7.26, N 11.21; found C 67.35, H 6.54, N 10.98. [α]2D5
+221 (c = 1.00, CHCl3).
=
General Procedure for the Methylation of Alkyl 2-Cyanoacetates: min to 120 °C then hold 5 min, 3 °C/min to 130 °C then hold
K2CO3 (5.18 g, 37.5 mmol) was added to a solution of alkyl 2- 20 min.
Eur. J. Inorg. Chem. 2015, 1604–1615
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FULL PAPER
General Procedure for Hg Drop Test: Compound 1d (0.0147 g,
0.02 mmol, 2 mol-%) and the α-methyl cyano ester substrate
(1.00 mmol) were stirred in chloroform (3 mL) for 5 min till the
dissolution of the catalyst occurred. Then, the Hg drop was added,
a solution of the Michael acceptor 7 or 8 (1.50 mmol) in chloro-
form (2 mL) was added, and the resultant solution was stirred for
8 h at room temperature. The volatiles were then removed in vacuo,
and the crude product was purified by column chromatography
(silica, petroleum ether/ethyl acetate 95:5–70:30) to give the
Isopropyl 2,4-Dicyano-2-methylbutanoate (13): Colorless oil
(0.151 g, 78%). [α]2D5 = 0.248 (c = 1.00, CHCl3); ee: 9%. H NMR
1
3
(CDCl3, 400 MHz, 25 °C): δ = 5.11 [sept, JH,H = 6 Hz, 1 H,
CH(CH3)2], 2.65–2.48 (m, 2 H, CNCH2CH2C), 2.44–2.33 (m, 1 H,
CNCH2CH2C), 2.16–2.09 (m, 1 H, CNCH2CH2C), 1.65 (s, 3 H,
3
3
CNCCH3), 1.34 [d, JH,H = 6 Hz, 3 H, CH(CH3)2], 1.33 [d, JH,H
= 6 Hz, 3 H, CH(CH3)2] ppm. 13C{1H} NMR (CDCl3, 100 MHz,
25 °C): δ = 167.5 (CO2), 118.5 (CCN or CH2CN), 117.8 (CCN or
CH2CN), 72.0 (CH3CH2), 43.3 (CNCCH3), 33.3 (CNCH2CH2C),
Michael adduct. The ee was determined by GC with a CP-Chirasil- 23.7 (CNCCH3), 21.7 [CH(CH3)2], 21.6 [CH(CH3)2], 14.0
Dex CB chiral column.
(CNCH2CH2C) ppm.
tert-Butyl 2,4-Dicyano-2-methylbutanoate (14): Colorless oil
(0.135 g, 65%). [α]2D5 = –1.56 (c = 1.00, CHCl3); ee: 39%. 1H NMR
(CDCl3, 400 MHz, 25 °C): δ = 2.64–2.46 (m, 2 H, CNCH2CH2C),
General Procedure for the Blank Experiment: A mixture of α-methyl
cyano ester substrate (1.00 mmol) and Michael acceptor 7 or 8
(1.50 mmol) in chloroform (5 mL) was stirred for 8 h at room tem-
perature. The reaction was monitored by GC analysis.
2.38–2.30 (m,
1
H, CNCH2CH2C), 2.13–2.05 (m,
H, CNCCH3), 1.52 [s,
1
9
H,
H,
CNCH2CH2C), 1.62 (s,
3
General Procedure for the Control Experiment: A mixture of
NiCl2·6H2O (0.0048 g, 0.02 mmol, 2 mol-%), α-methyl cyano ester
substrate (1.00 mmol), and Michael acceptor 7 or 8 (1.50 mmol) in
CHCl3 (5 mL) was stirred for 8 h at room temperature. The reac-
tion was monitored by GC analysis.
C(CH3)3] ppm. 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ =
166.8 (CO2), 118.7 (CCN or CH2CN), 117.9 (CCN or CH2CN),
85.2 [C(CH3)3], 43.9 (CNCCH3), 33.2 (CNCH2CH2C), 27.8
[C(CH3)3], 23.6 (CNCCH3), 13.9 (CNCH2CH2C) ppm.
Ethyl 2-Cyano-2-methyl-5-oxohexanoate (9): Colorless oil (0.185 g,
94%). [α]2D5 = –3.16 (c 1.00, CHCl3); ee: 75%. 1H NMR (CDCl3,
400 MHz, 25 °C): δ = 4.26 (q, JH,H = 7 Hz, 2 H, CH2CH3), 2.74–
Acknowledgments
3
The authors thank the Department of Science and Technology
(DST), New Delhi (grant number SR/S1/IC-15/2011) for the finan-
cial support of this research. For the crystallographic data, we
thank Prof. R. Murugavel for the use of his single-crystal X-ray
diffraction facility established through a DAE-SRC Outstanding
Investigator Award and also gratefully acknowledge the National
Single Crystal X-ray Diffraction Facility at IIT Bombay and the
Single Crystal X-ray Diffraction Facility at the Department of
Chemistry, IIT Bombay, India. N. R. thanks the Council of Scien-
tific and Industrial Research (CSIR), New Delhi for a research fel-
lowship.
2.56 [m, 2 H, C(O)CH2CH2C], 2.28–2.20 [m, 1 H, C(O)CH2CH2C],
2.18 (s, 3 H, CH3CO), 2.08–2.01 [m, 1 H, C(O)CH2CH2C], 1.61 (s,
3 H, CNCCH3), 1.33 (t, JH,H = 7 Hz, 3 H, CH2CH3) ppm.
3
13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ = 206.0 (CH3CO),
169.0 (CO2), 119.7 (CN), 63.1 (CH3CH2), 43.2 (CNCCH3), 39.3
[C(O)CH2CH2C], 31.7 (CH3CO), 30.1 [C(O)CH2CH2C], 23.7
(CNCCH3), 14.1 (CH3CH2) ppm.
Isopropyl 2-Cyano-2-methyl-5-oxohexanoate (10): Colorless oil
(0.193 g, 91%). [α]2D5 = –3.34 (c 1.00, CHCl3); ee: 72%. H NMR
1
3
(CDCl3, 400 MHz, 25 °C): δ = 5.07 [sept, JH,H = 6 Hz, 2 H,
CH(CH3)2], 2.74–2.54 [m, 2 H, C(O)CH2CH2C], 2.25–2.19 [m, 1 H,
C(O)CH2CH2C], 2.18 (s, 3 H, CH3CO), 2.06–2.00 [m, 1 H, C(O)-
[1] a) T. Tokoroyama, Eur. J. Org. Chem. 2010, 2009–2016; b) T.
Poon, B. P. Mundy, T. W. Shattuck, J. Chem. Educ. 2002, 79,
264–267; c) A. B. Costa, J. Chem. Educ. 1971, 48, 243–246.
[2] A. Michael, J. Prakt. Chem. 1887, 35, 349–356.
[3] a) B. Tan, N. R. Candeias, C. F. Barbas III, Nat. Chem. 2011,
3, 473–477; b) C. Grondal, M. Jeanty, D. Enders, Nat. Chem.
2010, 2, 167–178; c) D. W. C. MacMillan, Nature 2008, 455,
304–308
3
CH2CH2C], 1.59 (s, 3 H, CNCCH3), 1.31 [d, JH,H = 6 Hz, 3 H,
3
CH(CH3)2], 1.30 [d, JH,H = 6 Hz, 3 H, CH(CH3)2] ppm. 13C{1H}
NMR (CDCl3, 100 MHz, 25 °C): δ = 205.9 (CH3CO), 168.4 (CO2),
119.7 (CN), 71.1 [CH(CH3)2], 43.3 (CNCCH3), 39.3 [C(O)-
CH2CH2C], 31.5 (CH3CO), 30.1 [C(O)CH2CH2C], 23.5
(CNCCH3), 21.6 [CH(CH3)2], 21.5 [CH(CH3)2] ppm.
[4] a) S.-R. Ban, X.-X. Zhu, Z.-P. Zhang, Q.-S. Li, Bioorg. Med.
Chem. Lett. 2014, 24, 2517–2520; b) W. Yao, M. Chen, X. Liu,
R. Jiang, S. Zhang, W. Chen, Catal. Sci. Technol. 2014, 4,
1726–1729; c) B. Qiao, Y. An, Q. Liu, W. Yang, H. Liu, J. Shen,
L. Yan, Z. Jiang, Org. Lett. 2013, 15, 2358–2361; d) B. Zhou,
Y. Yang, J. Shi, Z. Luo, Y. Li, J. Org. Chem. 2013, 78, 2897–
2907; e) B.-D. Cui, W.-Y. Han, Z.-J. Wu, X.-M. Zhang, W.-C.
Yuan, J. Org. Chem. 2013, 78, 8833–8839; f) J. Y. Kang, R. G.
Carter, Org. Lett. 2012, 14, 3178–3181; g) K. Dudzin´ski, A. M.
Pakulska, P. Kwiatkowski, Org. Lett. 2012, 14, 4222–4225.
[5] a) B.-C. Hong, N. S. Dange, C.-F. Ding, J.-H. Liao, Org. Lett.
2012, 14, 448–451; b) M. R. Monaco, P. Renzi, D. M.
Scarpino Schietroma, M. Bella, Org. Lett. 2011, 13, 4546–4549;
c) H. Xie, L. Zu, H. Li, J. Wang, W. Wang, J. Am. Chem. Soc.
2007, 129, 10886–10894; d) H. Gröger, J. Wilken, Angew. Chem.
Int. Ed. 2001, 40, 529–532; Angew. Chem. 2001, 113, 545.
[6] a) W. Yang, D.-M. Du, Chem. Commun. 2013, 49, 8842–8844;
b) M. B. Cid, J. Lο´pez-Cantarero, S. Duce, J. L. García Ruano,
J. Org. Chem. 2009, 74, 431–434; c) B. Wang, F. Wu, Y. Wang,
X. Liu, L. Deng, J. Am. Chem. Soc. 2007, 129, 768–769; d) M.
Bell, K. Frisch, K. A. Jørgensen, J. Org. Chem. 2006, 71, 5407–
5410; e) H. Li, Y. Wang, L. Tang, L. Deng, J. Am. Chem. Soc.
2004, 126, 9906–9907.
tert-Butyl 2-Cyano-2-methyl-5-oxohexanoate (11): Colorless oil
(0.142 g, 63%). [α]2D5 = –0.67 (c 1.00, CHCl3); ee: 50%. H NMR
1
(CDCl3, 400 MHz, 25 °C):
δ
=
2.74–2.53 [m,
2
H,
C(O)CH2CH2C], 2.23–2.15 [m, 1 H, C(O)CH2CH2C], 2.19 (s, 3 H,
CH3CO), 2.04–1.97 [m, 1 H, C(O)CH2CH2C], 1.56 (s, 3 H,
CNCCH3), 1.50 [s, 9 H, C(CH3)3] ppm. 13C{1H} NMR (CDCl3,
100 MHz, 25 °C): δ = 206.1 (CH3CO), 167.9 (CO2), 120.0 (CN),
84.2 [C(CH3)3], 43.9 (CNCCH3), 39.3 [C(O)CH2CH2C], 31.6
(CH3CO), 30.1 [C(O)CH2CH2C], 27.9 [C(CH3)3], 23.6 (CNCCH3)
ppm.
Ethyl 2,4-Dicyano-2-methylbutanoate (12): Colorless oil (0.165 g,
1
92%). [α]2D5 = 0.348 (c = 1.00, CHCl3); ee: 2%. H NMR (CDCl3,
3
400 MHz, 25 °C): δ = 4.32 (q, JH,H = 7 Hz, 2 H, CH2CH3), 2.66–
2.50 (m, 2 H, CNCH2CH2C), 2.45–2.34 (m, 1 H, CNCH2CH2C),
2.18–2.10 (m, 1 H, CNCH2CH2C), 1.67 (s, 3 H, CNCCH3), 1.36
3
(t, JH,H = 7 Hz, 3 H, CH2CH3) ppm. 13C{1H} NMR (CDCl3,
100 MHz, 25 °C): δ = 167.9 (CO2), 118.5 (CCN or CH2CN), 117.8
(CCN or CH2CN), 63.7 (CH3CH2), 43.1 (CNCCH3), 33.3
(CNCH2CH2C), 23.6 (CNCCH3), 14.0 (CNCH2CH2C), 13.9
(CH3CH2) ppm.
Eur. J. Inorg. Chem. 2015, 1604–1615
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[7]
[22] Y. Zhou, J. Dong, F. Zhang, Y. Gong, J. Org. Chem. 2011, 76,
588–600.
[23] a) G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–
122; b) G. M. Sheldrick, SHELXL-97, University of Got-
tingen, Germany, 1997; c) G. M. Sheldrick, SHELXL-2013,
University of Gottingen, Germany, 2013.
a) K. Takenaka, M. Minakawa, Y. Uozumi, J. Am. Chem. Soc.
2005, 127, 12273–12281; b) . K. Takenaka, Y. Uozumi, Org.
Lett. 2004, 6, 1833–1835.
M. A. Stark, G. Jones, C. J. Richards, Organometallics 2000,
19, 1282–1291.
[8]
[9]
A. J. Blacker, M. L. Clarke, M. S. Loft, M. F. Mahon, J. M. J.
[24] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B.
Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-
nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-
gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M.
Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Starov-
erov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,
J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.
Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Ad-
amo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Mar-
tin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,
J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B.
Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09, re-
vision D.01, Gaussian, Inc., Wallingford, CT, 2009.
[25] a) A. D. Becke, Phys. Rev. A 1998, 38, 3098–3100; b) C. Lee,
W. Yang, R. G. Parr, Phys. Rev. B 1998, 37, 785–789.
[26] a) W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem. Phys. 1972,
56, 2257–2261; b) G. A. Petersson, A. Bennett, T. G. Tensfeldt,
M. A. AI-Laham, W. A. Shirley, J. Chem. Phys. 1988, 89, 2193–
2218; c) G. A. Petersson, M. A. AI-Laham, J. Chem. Phys.
1991, 94, 6081–6090.
[27] a) H. Xie, L. Zhao, L. Yang, Q. Lei, W. Fang, C. Xiong, J. Org.
Chem. 2014, 79, 4517–4527; b) N. D. Harrold, G. L. Hillhouse,
Chem. Sci. 2013, 4, 4011–4015; c) P. Liu, J. Montgomery, K. N.
Houk, J. Am. Chem. Soc. 2011, 133, 6956–6959; d) S. C. Wang,
D. M. Troast, M. Conda-Sheridan, G. Zuo, D. LaGarde, J.
Louie, D. J. Tantillo, J. Org. Chem. 2009, 74, 7822–7833; e)
E. B. Kadossov, K. J. Gaskell, M. A. Langell, J. Comput.
Chem. 2007, 28, 1240–1251; f) Q. Z. Han, Y. H. Zhao, H. Wen,
Data Sci. J. 2007, 6, S837–S846; g) D. C. Graham, K. J. Cavell,
B. F. Yates, Dalton Trans. 2007, 4650–4658.
Williams, Organometallics 1999, 18, 2867–2873.
D.-D. Shao, J.-L. Niu, X.-Q. Hao, J.-F. Gong, M.-P. Song, Dal-
ton Trans. 2011, 40, 9012–9019.
M. Sawamura, H. Hamashima, Y. Ito, J. Am. Chem. Soc. 1992,
114, 8295–8296.
a) A. P. Prakasham, P. Ghosh, Inorg. Chim. Acta 2015, DOI:
10.1016/j.ica.2014.11.005; b) A. Kumar, P. Ghosh, Eur. J. Inorg.
Chem. 2012, 3955–3969; c) P. Ghosh, J. Indian Inst. Sci. 2011,
91, 521–533; d) A. John, P. Ghosh, Dalton Trans. 2010, 39,
7183–7206.
a) S. Kumar, A. Narayanan, M. N. Rao, M. M. Shaikh, P.
Ghosh, J. Organomet. Chem. 2012, 696, 4159–4165; b) M. K.
Samantaray, M. M. Shaikh, P. Ghosh, Organometallics 2009,
28, 2267–2275; c) S. Ray, M. M. Shaikh, P. Ghosh, Eur. J. In-
org. Chem. 2009, 1932–1941.
[10]
[11]
[12]
[13]
[14] L. Pauling, The Nature of the Chemical Bond, 3rd ed., Cornell
University Press, Ithaca, 1960, p. 224–228 and 256–258.
[15] M. Katari, G. Rajaraman, P. Ghosh, J. Organomet. Chem.
2015, 775, 109–116.
[16] G. A.
Zhurko,
ChemCraft,
version
1.6;
http://
www.chemcraftprog.com (accessed on July 28, 2014).
[17] D. Zhang, S. Zhou, Z. Li, Q. Wang, L. Weng, Dalton Trans.
2013, 42, 12020–12030.
[18] C.-Y. Liao, K.-T. Chan, Y.-C. Chang, C.-Y. Chen, C.-Y. Tu, C.-
H. Hu, H. M. Lee, Organometallics 2007, 26, 5826–5833.
[19] a) R. H. Crabtree, Chem. Rev. 2012, 112, 1536–1554; b) J. A.
Widegren, R. G. Finke, J. Mol. Catal. A 2003, 198, 317–341;
c) J. D. Aiken III, R. G. Finke, J. Mol. Catal. A 1999, 145, 1–
44.
´
[20] a) J. Scianowski, Z. Rafin´ski, A. Wojtczak, Eur. J. Org. Chem.
2006, 3216–3225; b) D. C. Braddock, R. H. Pouwer, J. W. Bur-
ton, P. Broadwith, J. Org. Chem. 2009, 74, 6042–6049.
[21] a) H. C. Brown, K.-W. Kim, M. Srebnik, B. Singaram, Tetrahe-
dron 1987, 43, 4071–4078; b) M. W. Rathke, A. A. Millard, Org.
Synth. 1978, 58, 32–35.
[28] A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988, 88,
899–926.
Received: December 22, 2014
Published Online: February 16, 2015
Eur. J. Inorg. Chem. 2015, 1604–1615
1615
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim