New entry to the synthesis of α-iminonitriles by Lewis acid mediated isomerization of cyano-substituted iminoisobenzofurans prepared by palladium-catalyzed three-component coupling of arynes, isocyanides, and cyanoformates

Article abstract of DOI:10.1021/om500408h

A variety of α-iminonitriles were formed as the minor products of three-component coupling reactions of arynes, isocyanides, and cyanoformates in the presence of the cationic palladium complex [Pd(NCPh)₂(dppf)] (BF₄)₂ as the catalyst, along with cyano-substituted iminoisobenzofurans as the major products. α-Iminonitriles obtained from this process are hardly accessible by conventional methods. In addition, when the isolated iminoisobenzofurans were treated with diisobutylaluminum hydride (DIBAL-H) or AlMe₃, the transformation of cyano-substituted iminoisobenzofurans into α-iminonitriles was observed.

Full text of DOI:10.1021/om500408h

Article
pubs.acs.org/Organometallics
New Entry to the Synthesis of α‑Iminonitriles by Lewis Acid Mediated
Isomerization of Cyano-Substituted Iminoisobenzofurans Prepared
by Palladium-Catalyzed Three-Component Coupling of Arynes,
Isocyanides, and Cyanoformates
Jing Li,† Shintaro Noyori,† Kiyohiko Nakajima,‡ and Yasushi Nishihara*,†,§
†Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University, 3-1-1
Tsushimanaka, Kita-ku, Okayama 700-8530, Japan
‡Department of Chemistry, Faculty of Education, Aichi University of Education, 1 Hirosawa, Igaya, Kariya, Aichi 448-8542, Japan
§ACT-C, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
S
* Supporting Information
ABSTRACT: A variety of α-iminonitriles were formed as the minor products of three-component coupling reactions of arynes,
isocyanides, and cyanoformates in the presence of the cationic palladium complex [Pd(NCPh)2(dppf)](BF4)2 as the catalyst,
along with cyano-substituted iminoisobenzofurans as the major products. α-Iminonitriles obtained from this process are hardly
accessible by conventional methods. In addition, when the isolated iminoisobenzofurans were treated with diisobutylaluminum
hydride (DIBAL-H) or AlMe3, the transformation of cyano-substituted iminoisobenzofurans into α-iminonitriles was observed.
Scheme 1. (a) Metal-Free Synthesis of Iminoisobenzofurans
via Three-Component Couplings and (b) Palladium-Assisted
Synthesis of Cyano-Substituted Iminoisobenzofurans and α-
Iminonitriles
INTRODUCTION
■
α-Iminonitriles, known as imidoyl cyanides, are important
compounds for the synthesis of α-keto acids,1 ketene imines,2
amides,3 α-amino acids,4 imidoylnitriles,5 β-nitroenamines,
amidines, glyoxalic acids,6 and nitrogen-containing heterocyclic
compounds.7 Although there have been a large number of
synthetic methods of α-iminonitriles,8 the reported procedures
are not preparatively satisfactory, owing to the need for a
tedious multistep synthesis. No examples to date include an
ester group.
On the other hand, arynes have been recognized as highly
reactive chemical species, which have played a significant role in
synthetic organic chemistry.9 2-(Trimethylsilyl)phenyl triflate
has been utilized as a common benzyne precursor, which has
enabled various carbon−carbon bond-forming processes via
addition of nucleophiles to arynes to produce zwitterionic
species, followed by trapping with electrophiles.10 Recently, this
feature has been successfully explored by the research groups of
Yoshida11 and Stoltz12 in three-component coupling reactions
of arynes with isocyanides, aldehydes, ketones, sulfonyl imines,
or phenyl esters for the direct synthesis of benzoannulated
iminofurans under metal-free conditions (Scheme 1a). We felt
that added opportunities might accrue from the introduction of
transition metals to these reactions with cyanoformates, and
indeed this proved the case (Scheme 1b).13 Despite the large
number of related processes now known, our work constitutes
the first report of palladium-catalyzed three-component
coupling reactions based on activation of electrophiles,
insertion of the resulting organo-palladium species into
zwitterions, and intramolecular cyclization to afford benzoan-
nulated heterocyclic compounds.
A vast number of functional groups can be installed via
coupling of nucleophiles with arynes. The versatility of this
transformation can be enhanced, however, by use of novel
coupling partners such as cyanoformates.14 Here we describe
the palladium-catalyzed three-component assembly of various
arynes, isocyanides, and cyanoformates, which gives access to
Received: April 17, 2014
© XXXX American Chemical Society
A
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structurally diverse cyano-substituted iminoisobenzofurans, as
well as unexpected α-iminonitriles (Scheme 1b).15 The latter
species are formed via an interesting skeletal rearrangement,
involving ring opening of the five-membered iminoisobenzofur-
ans following isolation and treatment of DIBAL-H or AlMe3.
This novel reaction, in which α-iminonitriles are formed from
three components, formally involves three C−C bond
formations and one C−C bond cleavage, accompanied by
migration of a cyano group.
C−O bond cleavage but also a CN group migration via C−C
bond cleavage in the five-membered heterocyclic ring.
Yields suffer when the reaction temperature is decreased
from 50 °C to room temperature (Table 1, entry 2). Screening
of the palladium catalysts Pd2(dba)3·CHCl3, PdCl2(PPh3)2,
PdCl2(bipy), and PdCl2/2Py likewise gave poorer results
(Table 1, entries 3−6). In contrast, use of the cationic complex
17
[Pd(NCPh)2(dppf)](BF4)2 afforded 4a in 68% yield,
accompanied by 26% of 5a (Table 1, entry 7). However,
employment of boron-containing Lewis acids (BF3·Et2O and
B(C6F5)3) as the additive had minimal impact on the yields and
ratios of 4a and 5a (Table 1, entries 8 and 9). As shown in
Table 1, entries 10−12, the cationic complexes [Pd(η-
C3H5)(cod)]BF4, [Rh(cod)2]BF4, and [Cp*Rh(NCMe)3]-
(PF6)2 afforded 4a and 5a in moderate combined yields,
suggesting that the cationic character of the catalyst gave better
results. Interestingly, this reaction failed in the absence of the
catalyst (Table 1, entry 13), in sharp contrast with the
transition-metal-free three-component coupling reactions re-
ported by Yoshida and Stoltz, in which iminoisobenzofuran
derivatives were obtained.11,12 We also investigated the use of
other solvents: lower yields of the products were obtained in di-
n-butyl ether and benzonitrile. The reaction did not proceed at
all in 1,4-dioxane.
RESULTS AND DISCUSSION
■
We initially optimized the catalyst system used to effect the
three-component transformations. Benzyne was prepared in
situ from 2-(trimethylsilyl)phenyl triflate (1a) and a naked
fluoride ion (KF/18-crown-6)16 and treated with 1,1,3,3-
tetramethylbutyl isocyanide (2a: CNCMe2CH2CMe3) and
ethyl cyanoformate (3a) at 50 °C for 18 h. The results are
summarized in Table 1. When PdCl2(NCPh)2 was employed as
Table 1. Optimization of Three-Component Coupling of the
Benzyne Precursor 1a, 1,1,3,3-Tetramethylbutyl Isocyanide
a
(2a), and Ethyl Cyanoformate (3a)
The generality of the three-component coupling reactions
was shown first by employing a variety of isocyanides 2 and
cyanoformates 3 under the optimized reaction conditions. As
shown in Table 2, the three-component coupling reactions
b
yield/%
Table 2. Scope of Pd-Catalyzed Three-Component Coupling
of 1a, Isocyanides 2, and Cyanoformates 3
entry
1
catalyst
PdCl2(NCPh)2
4a
5a
a
56
26
41
23
26
33
16
26
14
12
d
2
PdCl2(NCPh)2
3
4
5
6
7
Pd2(dba)3·CHCl3
PdCl2(PPh3)2
PdCl2(bipy)
PdCl2/2 Py
14
c
9
c
b
yield/%
[Pd(NCPh)2(dppf)](BF4)2
[Pd(NCPh)2(dppf)](BF4)2
[Pd(NCPh)2(dppf)](BF4)2
[Pd(η-C3H5)(cod)]BF4
[Rh(cod)2]BF4
68 (44)
26 (25)
e
entry
R2; isocyanide 2
R3; cyanoformate 3 products 4a
5a
8
f
59
26
9
52
52
45
47
0
28
16
26
24
0
1
2d
3
4
5
6
7
8
CMe2CH2CMe3; 2a
OEt; 3a
OMe; 3b
OnPr; 3c
OiPr; 3d
OnBu; 3e
OBn; 3f
OPh; 3g
3a
4a/5a
4b/5b
4c/5c
4d/5d
4e/5e
4f/5f
44
47
44
46
40
51
0
25
25
20
25
19
21
0
10
11
12
13
2a
2a
[Cp*Rh(NCMe)3](PF6)2
none
2a
2a
a
2a
The reaction was carried out using 1a (0.15 mmol), 2a (0.15 mmol),
3a (0.075 mmol), KF (0.3 mmol), 18-crown-6 (0.3 mmol), and a
catalyst (10 mol %) in a solvent (0.5 mL) at 50 °C for 18 h. Tf =
trifluoromethanesulfonyl, TMS = trimethylsilyl. Yields were deter-
mined by GC using tetradecane as an internal standard, based on
cyanoformate 3a. Isolated yields are shown in parentheses. The
reaction was carried out at room temperature. The reaction was
carried out using BF3·Et2O (20 mol %) as the additive. The reaction
2a
tBu; 2b
4g/5g
4h/5h
42
15
b
a
The reactions were carried out using 1a (1 mmol), 2 (1 mmol), 3
(0.5 mmol), KF (2 mmol), 18-crown-6 (2 mmol), and Pd catalyst (10
c
d
b
mol %) in THF (3.3 mL) at 50 °C for 18 h. Isolated yields, based on
e
cyanoformates 3.
f
was carried out using B(C6F5)3 (20 mol %) as the additive.
proceeded smoothly to form the corresponding cyano-
substituted iminoisobenzofurans 4a−h and α-iminonitrile 5a−
h. A series of aliphatic cyanoformates 3b−f bearing Me, nPr, iPr,
nBu, and Bn substituents reacted efficiently to afford the
corresponding products 4b−f and 5b−f in moderate to good
yields (Table 2, entries 2−6). The structure of 4a was
unambiguously confirmed through careful NMR spectroscopy
as well as X-ray diffraction analysis. As shown in Figure S1
(Supporting Information), the imine moiety in 4a was
determined to have the Z configuration. Unfortunately, neither
4g nor 5g was generated from aromatic cyanoformate 3g
the catalyst, a set of three-component coupled products were
obtained (Table 1, entry 1). In our earlier communication,15 we
reported that cyano-substituted iminoisobenzofuran 4a was
formed in 56% yield, but we were unable to characterize a
coproduct that was invariably present, formed in up to 33%
yield. We are now able to unambiguously assign this species.
On the basis of spectroscopic data and single crystal X-ray
diffraction (vide infra), we identify this species as α-iminonitrile
5a, thought to be generated through not only ring opening via
B
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Article
because diphenyl carbonate as the byproduct was detected
(Table 2, entry 7).14c In addition to 2a, other aliphatic
substituted isocyanides such as tert-butyl isocyanide (2b) could
participate in the three-component coupling reaction to afford
4h in 42% yield and 5h in 15% yield , respectively (Table 2,
entry 8).
To understand the effect of substituents on the benzyne
moiety in the present reaction, we next employed substituted
benzyne precursors 1b−d as the coupling partners (Scheme 2).
aryne derived from 1 and fluoride ion. Meanwhile, a cationic
palladium(II) complex activates cyanoformate 3 to generate
active species B. Zwitterion A then adds to B to afford C,
following which intramolecular cyclization furnishes iminoiso-
benzofurans 4 (path a). Alternatively, C can eliminate a cyano
group as the leaving group to form D, leading to the formation
of 5 (path b). We suspect that the cationic palladium catalyst
may interact with cyanoformates 3 to enhance the electro-
philicity of the latter.
When the reaction was quenched with water, amides were
detected in some cases. For example, when the 4,5-dimethyl
aryne precursor 1b was used as the substrate of the reaction of
2b, amide 6 was isolated in 31% yield (Scheme 3). From this
result, we infer that the reaction of A with B may be the rate-
determining step in Scheme 4.
Scheme 2. Three-Component Coupling with Various
Substituted Arynes
Scheme 3. Capture of Intermediate A Generated from 1b
and 2b
Scheme 4. Plausible Mechanism of the Palladium-Catalyzed
Three-Component Coupling Reactions
4,5-Dimethyl aryne 1b reacted smoothly with 2b and 3a to give
the three-component coupled products 4i and 5i in 35% and
18% yields, respectively. Furthermore, the three-component
coupling of unsymmetrical aryne was carried out in order to
clarify the regioselectivities. 1-(Trimethylsilyl)naphth-2-yl tri-
flate (1c) could also be applied to the reaction, leading to the
isolation of 4j in 35% (major) and 13% (minor) yields,
respectively, and a isomeric mixture of α-iminonitrile 5j in 23%
combined yield with a 83:17 isomeric ratio. In a similar manner,
the reaction of another 1,2-naphthalyne precursor, 2-
(trimethylsilyl)naphth-1-yl triflate (1d), also took place to
give two regioisomers 4j in 34% and 7% isolated yields,
respectively, and an 81:19 ratio of isomers 5j in 27% combined
yield, which indicates that both reactions proceeded through
the same 1,2-naphthalyne intermediate. The structure of one of
the isomers 5j was unambiguously confirmed by X-ray
diffraction analysis, as depicted in Figure 1.
We thus propose the reaction mechanism depicted in
Scheme 4. First, zwitterionic species A is generated by
nucleophilic attack of the carbon atom of isocyanide 2 on the
DIBAL-H is a unique and versatile organometallic hydride,
widely used as a reducing agent for the reduction of nitriles to
the corresponding aldehydes (in conjunction with aqueous
workup) or completely to the amines. According to the
literature reports,18 treating 4a with 1 equiv of DIBAL-H is
expected to yield the corresponding aldehyde. To our surprise,
however, ring opening via C−O bond cleavage occurred,
accompanied by migration of the CN group via C−C bond
cleavage, resulting in the transformation of 4a to 5a in 18%
NMR yield (Scheme 5). When the amount of DIBAL-H was
increased to 2.5 equiv, the yield of 5a increased to 31%; on use
of 10 equiv of DIBAL-H and prolonging the reaction time to 24
Figure 1. Thermal ellipsoid plot (30% probability) giving the structure
of 5j-minor determined by X-ray crystallography. Hydrogen atoms are
omitted for simplicity.
C
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Article
a
Scheme 5. Transformation of 4a to 5a with DIBAL-H
Table 4. Transformation of 4a to 5a with Lewis Acids
b
yield/%
entry
Lewis acid (LA)
5a
9
h, 5a was isolated in 83% yield. However, other metal hydrides
such as LiH, NaH, NaBH4, LiAlH4, and Cp2Zr(H)Cl did not
produce 5a at all. Although numerous examples of the reductive
cleavage of acetals,19 aminals,20 and ethers21 by DIBAL-H have
been reported, to the best of our knowledge, no applications of
DIBAL-H for the cleavage of the C−O bond of iminoiso-
benzofurans have been reported.
With the optimized reaction conditions in hand, we
employed a variety of aryne precursors 1, isocyanides 2, and
cyanoformates 3 (and benzoyl cyanide 7) to establish the scope
of this transformation. As shown in Table 3, the three-
component coupling reactions proceeded smoothly to form
mixtures of 4 and 5. After workup, but without further
purification, treatment of the crude mixture with 10 equiv of
DIBAL-H in hexane from 0 °C to room temperature for 24 h
gave the desired products 5a−j in moderate to good yields
(Table 3, entries 1−9). However, the transformation to the
corresponding 8 was not observed for 7 as the substrate (Table
3, entry 10). This transformation provides a novel route to
selective synthesis of α-iminonitriles 5.
To clarify the role of DIBAL-H in this transformation, we
explored the use of various alternative Lewis acids. The results
are shown in Table 4. Of note, use of the Lewis acids InCl3 and
Hf(OTf)4 resulted in lower yields of α-iminonitrile 5a, due to
the formation of amide 9 (Table 4, entries 1 and 2). Reaction in
the presence of 20 mol % of Sc(OTf)3 furnished 5a in 36%
yield (Table 4, entry 3). A series of aluminum-based Lewis
acids were also tested. Exclusive formation of 5a was observed
on use of equimolar amounts of AlMe3, AliBu3, or AlEt2Cl
(Table 4, entries 4−6), while no reaction occurred when AlCl3
was employed (Table 4, entry 7).
1
2
3
InCl3
4
<1
36
94
63
65
0
38
42
<1
0
Hf(OTf)4
Sc(OTf)3
AlMe3
c
4
c
5
c
AliBu3
0
6
AlEt2Cl
AlCl3
0
7
0
a
Reactions were carried out using 4a (0.1 mmol) and Lewis acid (20
b
mol %) in THF (0.5 mL) at 70 °C for 8 h. Determined by 1H NMR
c
spectra using CH2Br2 as an internal standard. An equimolar amount
of Al reagent was used, and the reactions were carried out at room
temperature..
Several additional experiments were carried out to gain
insight into the reaction mechanism of this transformation.
Treatment of 4a with 0.1 equiv of DIBAL-H and an equimolar
amount of KCN afforded the product 5a in 41% yield.
Additionally, when N-benzylidene-tert-butylamine was treated
with KCN, no reaction was observed, and the substrate
remained unreacted. On the basis of these results, it is
reasonable to hypothesize that DIBAL-H functions as a Lewis
acid. We propose that reaction of 4 with DIBAL-H occurs via
the mechanism presented in Scheme 6. Thus, DIBAL-H acts as
a Lewis acid to promote the cleavage of the C−O bond and
release of cyanide ion, which then attacks the iminyl carbon to
produce 5.
CONCLUSION
In summary, we have developed a useful method for the
synthesis of α-iminonitriles via a three-component coupling
■
Table 3. Three-Component Couplings of Aryl Triflates 1, Isocyanides 2, and Cyanoformates 3, Followed by Treatment of
a
DIBAL-H: Exclusive Synthesis of α-Iminonitriles 5
b
entry
aryne precursors
R2; isocyanide 2
R3; cyanoformate 3
products
yield/%
1
2
1a
1a
1a
1a
1a
1a
1a
1b
1c
1a
CMe2CH2CMe3; 2a
OEt; 3a
OMe; 3b
OnPr; 3c
OiPr; 3d
OnBu; 3e
OBn; 3f
3a
5a
5b
5c
5d
5e
5f
62
67
53
58
54
57
50
41
54
0
2a
3
2a
4
2a
5
2a
6
2a
tBu; 2b
7
5h
5i
8
2b
3a
9
2a
3a
5j
10
2a
Ph; 7
8
a
The reactions were carried out using 1 (0.5 mmol), 2 (0.5 mmol), 3 (0.25 mmol), KF (1 mmol), 18-crown-6 (1 mmol), and Pd catalyst (10 mol %)
in THF (1.6 mL) at 50 °C for 18 h. After workup, the crude products were treated with 10 equiv of DIBAL-H in hexane from 0 °C to room
b
temperature for 24 h. Isolated yields, based on cyanoformates 3.
D
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55.3, 58.4, 63.6, 98.8, 114.8, 122.5 (×2), 123.9, 131.7, 132.1, 139.2,
147.6. MS (EI, m/z (relative intensity)): 314 (M+, 2), 299 (71), 253
(28), 243 (86), 197 (54), 159 (31), 158 (100), 157 (67), 148 (31),
130 (71), 102 (43). Anal. Calcd for C19H26N2O2: C, 72.58; H, 8.33; N,
8.91. Found: C, 72.22; H, 8.42; N, 8.75.
Scheme 6. Proposed Mechanism for Transformation of 4 to
5
N-[3-Cyano-3-methoxy-1(3H)-isobenzofuranylidene]-2,4,4-tri-
methyl-2-pentanamine (4b). Isolated in 47% yield (71 mg, 0.24
mmol) as a pale yellow oil. IR (KBr, cm−1): 2239 (w, CN), 1724 (s,
1
CN). H NMR (300 MHz, CDCl3, room temperature): δ 1.02 (s,
9H), 1.45 (s, 3H), 1.46 (s, 3H), 1.76 (m, 2H), 3.68 (s, 3H), 7.58−7.61
(m, 3H), 7.74−7.77 (m, 1H). 13C NMR (75 MHz, CDCl3, room
temperature): δ 30.4, 30.5, 31.7 (×3), 32.0, 54.3, 55.4, 58.4, 99.2,
114.4, 122.5 (×2), 123.9, 131.8, 132.1, 138.8, 147.4. MS (EI, m/z
(relative intensity)): 300 (M+, 2), 285 (59), 253 (15), 230 (15), 229
(100), 202 (16), 197 (38), 173 (17), 162 (16), 158 (34), 157 (47),
130 (92), 102 (40). Anal. Calcd for C18H24N2O2: C, 71.97; H, 8.05; N,
9.33. Found: C, 71.79; H, 8.43; N, 9.06.
reaction of arynes, isocyanides, and cyanoformates. A cationic
palladium catalyst was found to play a crucial role in promoting
this transformation. Isomerization of cyano-substituted iminoi-
sobenzofurans to α-iminonitriles was effectively triggered by
treatment with aluminum-based Lewis acids. Studies aimed at
elucidating further transformations of the resulting iminoiso-
benzofurans and α-iminonitriles are in progress in our
laboratory and will be reported in due course.
N-[3-Cyano-3-propoxy-1(3H)-isobenzofuranylidene]-2,4,4-tri-
methyl-2-pentanamine (4c). Isolated in 44% yield (72 mg, 0.22
mmol) as a pale yellow oil. IR (KBr, cm−1): 2239 (w, CN), 1721 (s,
EXPERIMENTAL SECTION
■
1
CN). H NMR (300 MHz, CDCl3, room temperature): δ 0.97 (t,
General Considerations. All reactions were carried out under an
argon atmosphere using standard Schlenk techniques. Glassware was
dried in an oven (130 °C) and heated under reduced pressure before
use. NMR spectra (1H, 13C{1H}) were recorded on Mercury-300 (300
MHz) and Varian INOVA-600 (600 MHz) spectrometers. All 1H
NMR chemical shifts are reported in ppm relative to the proton
resonance in CDCl3 at δ 7.26. All 13C{1H} NMR chemical shifts are
reported in ppm relative to the carbon resonance in CDCl3 at δ 77.0.
Preparatory HPLC was carried out using a Model LC-9204R/U
recycling preparative HPLC using UV and RI as detectors with
chloroform as the eluent. Infrared spectra were recorded on a
Shimadzu IRPrestige-21 spectrophotometer. Elemental analyses were
carried out with a Perkin-Elmer 2400 CHN elemental analyzer at
Okayama University. High-resolution mass spectra (HRMS) were
obtained by fast atom bombardment (FAB) using a double-focusing
magnetic sector mass spectrometer.
3JHH = 7.5 Hz, 3H), 1.01 (s, 9H), 1.45 (s, 6H), 1.70 (m, 2H), 1.75 (d, J
= 4.2 Hz, 2H), 3.88 (m, 2H), 7.55−7.61 (m, 3H), 7.75−7.77 (m, 1H).
13C NMR (75 MHz, CDCl3, room temperature): δ 10.4, 22.5, 30.45,
30.53, 31.7 (×3), 32.0, 55.3, 58.4, 69.4, 98.9, 114.8, 122.5 (×2), 123.9,
131.7, 132.0, 139.2, 147.7. MS (EI, m/z (relative intensity)): 328 (M+,
2), 313 (80), 257 (53), 253 (23), 229 (21), 215 (24), 197 (23), 188
(22), 158 (100), 148 (47), 130 (97), 102 (48). Anal. Calcd for
C20H28N2O2: C, 73.14; H, 8.59; N, 8.53. Found: C, 73.29; H, 8.76; N,
8.36.
N-[3-Cyano-3-(1-methyethoxy)-1(3H)-isobenzofuranylidene]-
2,4,4-trimethyl-2-pentanamine (4d). Isolated in 46% yield (75 mg,
0.23 mmol) as a yellow solid. IR (KBr, cm−1): 2237 (w, CN), 1715
1
(s, CN). H NMR (300 MHz, CDCl3, room temperature): δ 1.02
(s, 9H), 1.33 (d, 3JHH = 6.3 Hz, 3H), 1.40 (d, J = 6.3 Hz, 3H), 1.45 (s,
3H), 1.46 (s, 3H), 1.74 (m, 2H), 4.49 (sep, J = 6.3 Hz, 1H), 7.54−7.60
(m, 3H), 7.74−7.77 (m, 1H). 13C NMR (75 MHz, CDCl3, room
temperature): δ 23.1, 23.7, 30.6, 31.8 (×3), 32.0, 55.5, 58.2, 72.9, 98.9,
115.2, 122.5, 123.9, 131.6, 132.0, 139.5, 147.7. MS (EI, m/z (relative
intensity)): 328 (M+, 1), 313 (50), 285 (20), 215 (51), 188 (31), 159
(27), 158 (100), 157 (22), 130 (60), 102 (31). Anal. Calcd for
C20H28N2O2: C, 73.14; H, 8.59; N, 8.53. Found: C, 72.97; H, 8.58; N,
8.30.
Each single crystal of 4a (CCDC-886033) and 5j (CCDC-968718)
was glued to the top of a glass fiber with epoxy resin, and X-ray
diffraction data were obtained at ambient temperature using a Rigaku
SCXmini CCD diffractometer with graphite-monochromated Mo Kα
radiation (λ = 0.71073 Å). The data were collected and processed
using the CrystalClear software package22 for both complexes, and
numerical absorption corrections were applied.23 The structures were
solved by direct methods (SHELXS9724) and refined by a full-matrix
least-squares method on F2 using the SHELXL97 software package.24
All non-hydrogen atoms were refined anisotropically, and hydrogen
atoms were placed at idealized positions by using riding models. All
calculations were performed with the CrystalStructure crystallographic
software package.25
N-[3-Buthoxy-3-cyano-1(3H)-isobenzofuranylidene]-2,4,4-tri-
methyl-2-pentanamine (4e). Isolated in 40% yield (68 mg, 0.20
mmol) as a yellow oil. IR (KBr, cm−1): 2237 (w, CN), 1719 (s, C
N). 1H NMR (300 MHz, CDCl3, room temperature): δ 0.93 (t, 3JHH
=
7.2 Hz, 3H), 1.01 (s, 9H), 1.42 (m, 2H), 1.45 (s, 3H), 1.46 (s, 3H),
1.67 (m, 2H), 1.75 (m, 2H), 3.92 (m, 2H), 7.56−7.60 (m, 3H), 7.75−
7.69 (m, 1H). 13C NMR (75 MHz, CDCl3, room temperature): δ 13.7,
19.1, 30.4, 30.5, 31.2 (×3), 31.7, 32.0, 55.3, 58.3, 67.6, 98.9, 114.8,
122.5, 123.9, 131.7, 132.0, 139.2, 147.6. MS (EI, m/z (relative
intensity)): 342 (M+, 4), 327 (100), 271 (41), 215 (25), 188 (23), 159
(23), 158 (81), 157 (37), 148 (48), 130 (94), 102 (38). Anal. Calcd
for C21H30N2O2: C, 73.65; H, 8.83; N, 8.18. Found: C, 73.37; H, 9.13;
N, 7.93.
General Procedure for the Synthesis of N-[3-Cyano-3-
ethoxy-1(3H)-isobenzofuranylidene]-2,4,4-trimethyl-2-pentan-
amine (4a). A flame-dried 25 mL Schlenk flask with a magnetic stir
bar was charged with KF (116 mg, 2.0 mmol), 18-crown-6 (529 mg,
2.0 mmol), and [Pd(PhCN)2(dppf)](BF4)2 (52 mg, 0.05 mmol, 10
mol %) in THF (3.3 mL) under argon. To this solution were added 2-
(trimethylsilyl)phenyl triflate (1a; 233 μL, 1.0 mmol), 1,1,3,3-
tetramethylbutyl isocyanide (2a; 175 μL, 1.0 mmol), and ethyl
cyanoformate (3a; 51 μL, 0.5 mmol) sequentially via syringe. The
reaction mixture was heated to 50 °C for 18 h and then cooled to
ambient temperature, quenched with water, and extracted with diethyl
ether (20 mL × 3). The combined extracts were washed with brine
and dried over anhydrous sodium sulfate. The volatiles were removed
under reduced pressure to give crude products, which were purified by
silica gel column chromatography (eluent hexane/ethyl acetate, 19/1).
Further purification with HPLC (eluent chloroform) gave 4a (69 mg,
0.22 mmol, 44%) as a yellow solid. IR (KBr, cm−1): 2239 (w, CN),
N-[3-Cyano-3-(phenylmethoxy)-1(3H)-isobenzofuranylidene]-
2,4,4-trimethyl-2-pentanamine (4f). Isolated in 51% yield (96 mg,
0.26 mmol) as a pale yellow oil. IR (KBr, cm−1): 2239 (w, CN),
1
1722 (s, CN). H NMR (300 MHz, CDCl3, room temperature): δ
1.02 (s, 9H), 1.45 (s, 3H), 1.46 (s, 3H), 1.76 (m, 2H), 4.88 (d, 3JHH
=
3
10.5 Hz, 1H), 5.02 (d, JHH = 10.5 Hz, 1H), 7.32−7.37 (m, 5H),
7.56−7.64 (m, 3H), 7.75−7.76 (m, 1H). 13C NMR (75 MHz, CDCl3,
room temperature): δ 30.46, 30.51, 31.8 (×3), 32.0, 55.4, 58.4, 69.7,
98.7, 114.7, 122.7, 123.9, 128.3 (×2), 128.5, 128.6 (×2), 131.85, 132.1,
135.3, 138.9, 147.3. MS (EI, m/z (relative intensity)): 376 (M+, 0.24),
361 (16), 285 (47), 188 (31), 148 (13), 130 (13), 111 (12), 92 (8), 91
(100), 65 (9). Anal. Calcd for C24H28N2O2: C, 76.56; H, 7.50; N, 7.44.
Found: C, 76.36; H, 7.86; N, 7.30.
1
1715 (s, CN). H NMR (300 MHz, CDCl3, room temperature): δ
1.01 (s, 9H), 1.34 (t, 3JHH = 7.2 Hz, 3H), 1.46 (s, 6H), 1.76 (m, 2H),
4.01 (m, 2H), 7.55−7.62 (m, 3H), 7.76−7.79 (m, 1H). 13C NMR (75
MHz, CDCl3, room temperature): δ 14.9, 30.4, 30.5, 31.7 (×3), 32.0,
E
dx.doi.org/10.1021/om500408h | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
N-[3-Cyano-3-ethoxy-1(3H)-isobenzofuranylidene]-2-methyl-2-
δ 25.2, 27.8, 28.0, 48.4, 51.8, 59.0, 108.6, 125.3, 125.8, 126.3, 126.4,
128.4, 132.2, 134.2, 163.0. MS (EI, m/z (relative intensity)): 300 (M+,
3), 286 (20), 285 (100), 229 (64), 197 (30), 162 (16), 158 (17), 157
(51), 130 (88), 102 (31). Anal. Calcd for C18H24N2O2: C, 71.97; H,
8.05; N, 9.33. Found: C, 71.72; H, 8.31; N, 9.01.
propanamine (4h). Isolated in 42% yield (54 mg, 0.21 mmol) as a
1
yellow oil. IR (KBr, cm−1): 2239 (w, CN), 1721 (s, CN). H
NMR (300 MHz, CDCl3, room temperature): δ 1.33 (t, 3JHH = 7.2 Hz,
3H), 1.42 (s, 9H), 3.98 (m, 2H), 7.56−7.62 (m, 3H), 7.79−7.81 (m,
1H). 13C NMR (75 MHz, CDCl3, room temperature): δ 14.9, 28.0,
30.1 (×3), 54.8, 63.6, 98.8, 114.7, 122.5, 123.9, 131.7, 132.2, 139.2,
149.3. MS (EI, m/z (relative intensity)): 258 (M+, 1), 243 (100), 197
(44), 158 (68), 157 (31), 130 (55), 102 (49). Anal. Calcd for
C15H18N2O2: C, 69.74; H, 7.02; N, 10.84. Found: C, 69.99; H, 7.07;
N, 10.53.
(Z)-Propyl 2-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-
benzoate (5c). Isolated in 20% yield as(33 mg, 0.10 mmol) as a
pale yellow oil. IR (KBr, cm−1): 2210 (w, CN), 1714 (s, CN),
1
1616 (s, CO). H NMR (300 MHz, CDCl3, room temperature): δ
1.01 (t, 3JHH = 7.5 Hz, 12H), 1.61 (s, 6H), 1.80 (m, 2H), 1.89 (s, 2H),
4.30 (t, J = 6.9 Hz, 2H), 7.50−7.59 (m, 3H), 7.91−7.94 (m, 1H). 13C
NMR (75 MHz, CDCl3, room temperature): δ 10.4, 22.0, 29.1, 31.7
(overlapped), 32.0, 55.8, 63.0, 67.2, 112.6, 129.3, 130.2, 130.3, 132.2,
136.2, 138.3, 166.5. MS (EI, m/z (relative intensity)): 328 (M+, 4),
314 (22), 313 (100), 257 (29), 197 (20), 158 (39), 157 (45), 148
(34), 130 (58), 102 (16). Anal. Calcd for C20H28N2O2: C, 73.14; H,
8.59; N, 8.53. Found: C, 73.34; H, 8.74; N, 8.23.
N-[3-Cyano-3-ethoxy-5,6-dimethyl-1(3H)-isobenzofuranylidene]-
2,4,4-trimethyl-2-pentanamine (4i). Isolated in 33% yield (47 mg,
0.17 mmol) as a yellow oil. IR (KBr, cm−1): 2212 (w, CN), 1715 (s,
1
CN). H NMR (300 MHz, CDCl3, room temperature): δ 1.31 (t,
3JHH = 7.2 Hz, 3H), 1.41 (s, 9H), 2.33 (s, 3H), 2.36 (s, 3H), 3.98 (m,
2H), 7.37 (s, 1H), 7.58 (s, 1H). 13C NMR (75 MHz, CDCl3, room
temperature): δ 14.9, 20.0, 20.4, 30.1, 54.6, 63.3, 98.7, 115.0, 123.0,
124.2, 129.2, 137.1, 141.2, 142.1, 149.8. MS (EI, m/z (relative
intensity)): 286 (M+, 6), 271 (100), 225 (58), 201 (24), 186 (67), 158
(78), 103 (41), 77 (26). Anal. Calcd for C17H22N2O2: C, 71.30; H,
7.74; N, 9.78. Found: C, 71.20; H, 7.81; N, 9.48.
(Z)-Isopropyl 2-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-
benzoate (5d). Isolated in 25% yield (41 mg, 0.13 mmol) as a yellow
solid. IR (KBr, cm−1): 2210 (w, CN), 1716 (s, CN), 1618 (s,
1
CO). H NMR (300 MHz, CDCl3, room temperature): δ 1.02 (s,
9H), 1.39 (d, 3JHH = 6.3 Hz, 6H), 1.62 (s, 6H), 1.90 (s, 2H), 5.28 (seq,
3JHH = 6.3 Hz, 1H), 7.47−7.58 (m, 3H), 7.91−7.94 (m, 1H). 13C
1-Ethoxy-3-(2,4,4-trimethylpentan-2-ylimino)-1,3-
dihydronaphtho[1,2-c]furan-1-carbonitrile (4j-major). Isolated in
35% yield (64 mg, 0.18 mmol) (from 1c) or 34% yield (62 mg, 0.17
mmol) (from 1d) as a yellow oil. IR (KBr, cm−1): 2237 (CN), 1713
NMR (75 MHz, CDCl3, room temperature): δ 21.9, 29.1, 31.8, 32.0,
55.9, 63.0, 69.5, 112.8, 129.4, 130.0, 130.3, 130.4, 132.2, 136.4, 138.6,
165.8. MS (EI, m/z (relative intensity)): 328 (M+, 4), 314 (22), 313
(100), 285 (27), 271 (29), 215 (64), 188 (21), 175 (22), 158 (59),
157 (50), 148 (41), 130 (71), 111 (20), 102 (20). Anal. Calcd for
C20H28N2O2: C, 73.14; H, 8.59; N, 8.53. Found: C, 72.77; H, 8.97; N,
8.14.
1
(s, CN). H NMR (300 MHz, CDCl3, room temperature): δ 1.04
3
(s, 9H), 1.35 (t, JHH = 7.2 Hz, 3H), 1.54 (s, 3H), 1.55 (s, 3H), 1.88
3
(m, 2H), 4.02 (m, 2H), 7.61−7.73 (m, 3H), 7.95 (d, JHH = 7.5 Hz,
3
3
1H), 8.06 (d, JHH = 8.4 Hz, 1H), 9.34 (d, JHH = 8.1 Hz, 1H). 13C
NMR (75 MHz, CDCl3, room temperature): δ 14.9, 30.8, 30.9, 31.9
(×3), 32.1, 55.2, 59.0, 63.5, 98.3, 114.9, 118.3, 125.1, 126.2, 127.9,
128.3, 128.4, 128.6, 133.4, 135.0, 138.7, 148.4. MS (EI, m/z (relative
intensity)): 364 (M+, 26), 349 (44), 293 (26), 247 (34), 225 (26), 223
(20), 210 (20), 208 (40), 207 (34), 197 (23), 180 (100), 179 (39),
153 (35), 152 (66), 127 (23), 126 (28), 97 (19). HRMS (FAB+): m/z
calcd for C23H29N2O2 (M + H)+ 365.2229, found 365.2251.
(Z)-Butyl 2-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-
benzoate (5e). Isolated in 19% yield (32 mg, 0.10 mmol) as a yellow
oil. IR (KBr, cm−1): 2210 (w, CN), 1718 (s, CN), 1620 (s, C
O). 1H NMR (300 MHz, CDCl3, room temperature): δ 0.97 (t, 3JHH
=
7.2 Hz, 3H), 1.01 (s, 9H), 1.45 (m, 2H), 1.61 (s, 6H), 1.75 (m, 2H),
3
1.89 (s, 2H), 4.34 (t, JHH = 6.6 Hz, 2H), 7.49−7.61 (m, 3H), 7.90−
7.93 (m, 1H). 13C NMR (75 MHz, CDCl3, room temperature): δ 13.7,
19.2, 29.1, 30.6, 31.7 (overlapped), 32.0, 55.8, 63.0, 65.5, 112.6, 129.3,
130.2, 130.3, 132.2, 136.2, 138.3, 166.5. MS (EI, m/z (relative
intensity)): 342 (M+, 4), 328 (24), 327 (100), 271 (26), 158 (39), 157
(38), 148 (35), 130 (60), 102 (19). Anal. Calcd for C21H30N2O2: C,
73.65; H, 8.83; N, 8.18. Found: C, 73.25; H, 8.69; N, 7.94.
3-Ethoxy-1-(2,4,4-trimethylpentan-2-ylimino)-1,3-
dihydronaphtho[2,1-c]furan-3-carbonitrile (4j-minor). Isolated in
13% yield (24 mg, 0.07 mmol) (from 1c) or 7% yield (13 mg, 0.04
mmol) (from 1d) as a yellow oil. IR (KBr, cm−1): 2237 (CN), 1713
1
(s, CN). H NMR (300 MHz, CDCl3, room temperature): δ 1.08
(s, 9H), 1.18 (t, 3JHH = 7.2 Hz, 3H), 1.99 (d, 3JHH = 14.4 Hz, 1H), 2.52
(Z)-Benzyl 2-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-
benzoate (5f). Isolated in 21% yield (39 mg, 0.11 mmol) as a pale
yellow oil. IR (KBr, cm−1): 2212 (w, CN), 1717 (s, CN), 1614
3
(d, JHH = 14.4 Hz, 1H), 3.00 (m, 1H), 3.33 (m, 1H), 7.61−7.73 (m,
3H), 7.95 (d, 3JHH = 7.5 Hz, 1H), 8.13 (d, 3JHH = 8.4 Hz, 1H), 9.14 (d,
3JHH = 8.1 Hz, 1H). 13C NMR (75 MHz, CDCl3, room temperature):
1
(s, CO). H NMR (300 MHz, CDCl3, room temperature): δ 0.99
(s, 9H), 1.53 (s, 6H), 1.86 (s, 2H), 5.37 (s, 2H), 7.36−7.42 (m, 5H),
7.51−7.59 (m, 3H), 7.93−7.95 (m, 1H). 13C NMR (75 MHz, CDCl3,
room temperature): δ 29.0, 31.7, 31.9, 55.8, 63.0, 67.4, 112.6, 128.4,
128.5, 128.6, 129.4, 129.7, 130.2, 130.5, 132.4, 135.3, 136.0, 138.4,
166.3. MS (EI, m/z (relative intensity)): 376 (M+, 0.31), 361 (17),
285 (50), 188 (33), 148 (13), 130 (13), 111 (12), 91 (100), 65 (15).
Anal. Calcd for C24H28N2O2: C, 76.56; H, 7.50; N, 7.44. Found: C,
76.17; H, 7.58; N, 7.30.
δ 14.5, 26.7, 28.9, 31.5 (×3), 31.8, 51.0, 58.9, 61.9, 85.3, 117.0, 118.3,
124.3, 126.1, 128.0, 128.5, 129.0, 134.3, 134.8, 139.2, 168.9. MS (EI,
m/z (relative intensity)): 364 (M+, 9), 349 (71), 293 (20), 247 (35),
225 (29), 223 (25), 208 (46), 207 (42), 180 (100), 153 (29), 152
(73), 126 (21), 97 (20). HRMS (FAB+): m/z calcd for C23H29N2O2
(M + H)+ 365.2229, found 365.2236.
(Z)-Ethyl 2-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-
benzoate (5a). Isolated in 25% yield (39 mg, 0.13 mmol) as a pale
yellow oil. IR (KBr, cm−1): 2210 (w, CN), 1717 (s, CN), 1614
(Z)-Ethyl 2-[(tert-Butylimino)(cyano)methyl]benzoate (5h). Iso-
1
(s, CO). H NMR (300 MHz, CDCl3, room temperature): δ 1.01
lated in 15% yield (19 mg, 0.08 mmol) as a yellow oil. IR (KBr, cm−1):
3
1
(s, 9H), 1.40 (t, JHH = 7.2 Hz, 3H), 1.61 (s, 6H), 1.90 (s, 2H), 4.40
2212 (w, CN), 1717 (s, CN), 1622 (s, CO). H NMR (300
3
(q, JHH = 7.2 Hz, 2H), 7.50−7.59 (m, 3H), 7.91−7.94 (m, 1H). 13C
MHz, CDCl3, room temperature): δ 1.40 (t, 3JHH = 7.2 Hz, 3H), 1.55
3
NMR (75 MHz, CDCl3, room temperature): δ 14.2, 29.1, 31.8, 32.0,
55.8, 61.7, 63.0, 112.6, 129.3, 130.1, 130.2, 130.3, 132.2, 136.2, 138.2,
166.4. MS (EI, m/z (relative intensity)): 314 (M+, 3), 300 (22), 299
(93), 253 (23), 243 (55), 197 (36), 158 (53), 157 (100), 148 (38),
130 (66), 102 (35). Anal. Calcd for C19H26N2O2: C, 72.58; H, 8.33; N,
8.91. Found: C, 72.83; H, 8.12; N, 8.92.
(s, 9H), 4.40 (q, JHH = 7.2 Hz, 2H), 7.51−7.60 (m, 3H), 7.90−7.92
(m, 1H). 13C NMR (75 MHz, CDCl3, room temperature): δ 14.2,
29.1, 59.0, 61.7, 112.2, 129.6, 130.2, 130.3, 130.4, 132.2, 137.7, 137.8,
166.5. MS (EI, m/z (relative intensity)): 258 (M+, 5), 243 (64), 229
(27), 202 (38), 197 (29), 173 (26), 158 (51), 157 (92), 156 (35), 130
(100), 104 (21), 103 (27), 102 (51). Anal. Calcd for C15H18N2O2: C,
69.74; H, 7.02; N, 10.84. Found: C, 69.78; H, 7.03; N, 10.56.
(Z)-Ethyl 2-[(tert-Butylimino)(cyano)methyl]-4,5-dimethylben-
zoate (5i). Isolated in 18% yield (26 mg, 0.09 mmol) as a yellow
oil. IR (KBr, cm−1): 2214 (w, CN), 1714 (s, CN), 1607 (s, C
(Z)-Methyl 2-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-
benzoate (5b). Isolated in 25% yield (38 mg, 0.13 mmol) as a pale
yellow oil. IR (KBr, cm−1): 2210 (w, CN), 1728 (s, CN), 1614
1
(s, CO). H NMR (300 MHz, CDCl3, room temperature): δ 1.01
(s, 9H), 1.60 (s, 6H), 1.90 (s, 2H), 3.92 (s, 3H), 7.49−7.62 (m, 3H),
7.89−7.92 (m, 1H). 13C NMR (75 MHz, CDCl3, room temperature):
O). 1H NMR (300 MHz, CDCl3, room temperature): δ 1.39 (t, 3JHH
6.9 Hz, 3H), 1.54 (s, 9H), 2.32 (s, 3H), 2.32 (s, 3H), 4.37 (q, JHH
=
=
3
F
dx.doi.org/10.1021/om500408h | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
3
7.5 Hz, 2H), 7.23 (s, 1H), 7.69 (s, 1H). 13C NMR (75 MHz, CDCl3,
room temperature): δ 14.2, 19.5, 19.7, 29.2, 58.7, 61.4, 112.4, 127.3,
130.7, 131.5, 135.6, 138.2, 139.4, 141.7, 166.6. MS (EI, m/z (relative
intensity)): 286 (M+, 14), 271 (54), 257 (25), 230 (48), 225 (38), 201
(53), 186 (42), 185 (86), 184 (100), 158 (87), 132 (37), 131 (20),
130 (19), 103 (31), 77 (19). Anal. Calcd for C17H22N2O2: C, 71.30; H,
7.74; N, 9.78. Found: C, 71.37; H, 7.81; N, 9.45.
Compound 5j. Isolated in 23% (major:minor = 83:17) combined
yield (42 mg, 0.12 mmol) (from 1c) or 27% (major:minor = 81:19)
combined yield (49 mg, 0.14 mmol) (from 1d) as a yellow solid. IR
(KBr, cm−1): 2210 (w, CN), 1715 (s, CN), 1622 (s, CO).
HRMS (FAB+): m/z calcd for C23H29N2O2 (M + H)+ 365.2229, found
365.2205.
CDCl3, room temperature): δ 1.05 (s, 9H), 1.36 (t, JHH = 7.2 Hz,
3
3H), 1.54 (s, 6H), 1.85 (s, 2H), 4.36 (q, JHH = 7.5 Hz, 2H), 5.69 (s,
1H), 7.40−7.49 (m, 3H), 7.79−7.82 (m, 1H). 13C NMR (75 MHz,
CDCl3, room temperature): δ 14.2, 28.7, 31.5, 31.7, 52.3, 55.9, 61.4,
127.1, 129.2, 129.86, 129.91, 131.5, 139.1, 167.1, 167.8. MS (EI, m/z
(relative intensity)): 305 (M+, 0.26), 248 (6.4), 234 (21), 178 (11),
177 (100), 150 (8), 149 (98), 148 (17), 130 (7), 121 (7), 105 (6), 97
(9), 65 (7). Anal. Calcd for C18H27NO3: C, 70.79; H, 8.91; N, 4.59.
Found: C, 70.82; H, 8.65; N, 4.69.
ASSOCIATED CONTENT
* Supporting Information
■
S
Text, figures, tables, and CIF files giving experimental
procedures as well as characterization data for all of the
compounds prepared and X-ray data for 4a and 5j. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(Z)-Ethyl 2-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-1-
naphthoate (5j-major). 1H NMR (300 MHz, CDCl3, room
3
temperature): δ 0.98 (s, 9H), 1.43 (t, JHH = 7.2 Hz, 3H), 1.77 (s,
3
6H), 1.84 (s, 2H), 4.43 (q, JHH = 7.2 Hz, 2H), 7.60−7.64 (m, 2H),
7.91−8.05 (m, 3H), 8.05−8.08 (m, 1H). 13C NMR (75 MHz, CDCl3,
room temperature): δ 14.3, 28.3, 31.5, 31.9, 56.9, 61.7, 63.6, 112.9,
125.4, 125.6, 127.7, 128.3, 128.4, 129.8, 130.2, 130.5, 134.3, 135.5,
137.1, 166.0. MS (EI, m/z (relative intensity)): 364 (M+, 55), 350
(23), 349 (93), 308 (23), 293 (51), 253 (27), 252 (25), 247 (69), 238
(22), 223 (32), 220 (31), 210 (39), 208 (61), 207 (60), 198 (23), 180
(100), 179 (62), 153 (25), 152 (59), 127 (23), 126 (24), 97 (16).
(Z)-Ethyl 1-[Cyano(2,4,4-trimethylpentan-2-ylimino)methyl]-2-
naphthoate (5j-minor). 1H NMR (300 MHz, CDCl3, room
AUTHOR INFORMATION
Corresponding Author
■
*Y.N.: fax, +81-86-251-7855; e-mail, ynishiha@okayama-u.ac.
jp.
Notes
The authors declare no competing financial interest.
3
temperature): 1.02 (s, 9H), 1.44 (t, JHH = 7.2 Hz, 3H), 1.61 (s,
3
6H), 1.96 (s, 2H), 4.48 (q, JHH = 7.2 Hz, 2H), aromatic signals are
ACKNOWLEDGMENTS
■
overlapped with those of major isomer. 13C NMR (75 MHz, CDCl3,
room temperature): δ 14.1, 29.5, 31.7, 31.9, 55.1, 61.5, 63.2, 112.1,
124.5, 125.8, 126.8, 127.7, 128.1, 130.0, 130.5, 130.9, 134.3, 135.0,
137.1, 168.2. MS (EI, m/z (relative intensity)): 364 (M+, 11), 350
(25), 349 (100), 318 (25), 303 (26), 293 (31), 247 (56), 223 (38),
221 (21), 220 (31), 210 (23), 208 (58), 207 (63), 198 (19), 180 (66),
153 (21), 152 (47), 126 (18).
This work was partially supported by a Grant-in-Aid for
Scientific Research (KAKENHI) (No. 24550119) from JSPS
and the MEXT program for promoting the enhancement of
research universities. The authors gratefully thank Dr. Masayuki
Iwasaki at Okayama University for the HRMS measurements,
Ms. Megumi Kosaka and Mr. Motonari Kobayashi at the
Department of Instrumental Analysis, Advanced Science
Research Center, Okayama University, for measurements of
elemental analyses, and the SC-NMR Laboratory of Okayama
University for the NMR spectral measurements.
N-tert-Butyl-3,4-dimethylbenzamide (6).26 Isolated in 31% yield
(32 mg, 0.16 mmol) as a yellow solid. IR (KBr, cm−1): 1643 (s, C
O). 1H NMR (300 MHz, CDCl3, room temperature): δ 1.46 (s, 9H),
2.29 (s, 3H), 2.30 (s, 3H), 5.91 (brs, 1H, NH), 7.15 (d, 3JHH = 7.8 Hz,
3
1H), 7.42 (d, JHH = 7.8, 1H), 7.51 (s, 1H). 13C NMR (75 MHz,
CDCl3, room temperature): δ 19.72, 19.73, 28.9 (×3), 51.4, 124.0,
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dx.doi.org/10.1021/om500408h | Organometallics XXXX, XXX, XXX−XXX