Imidate as the Intact Directing Group for the Cobalt-Catalyzed C-H Allylation

Article abstract of DOI:10.1021/acs.joc.9b01972

Cobalt-catalyzed C-H allylation reactions of NH-free benzimidates using vinylcyclopropanes or allyl carbonate are reported. The reactive and relatively unstable imidate groups remain intact during the C-H allylations to afford functionalized imidates with

Full text of DOI:10.1021/acs.joc.9b01972

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Imidate as the Intact Directing Group for the Cobalt-Catalyzed C–H Allylation
Ryo Tanaka, Iku Tanimoto, Masahiro Kojima, Tatsuhiko Yoshino, and Shigeki Matsunaga
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b01972 • Publication Date (Web): 26 Aug 2019
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Imidate as the Intact Directing Group for the Cobalt-Catalyzed C–H Allylation
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Ryo Tanaka, Iku Tanimoto, Masahiro Kojima, Tatsuhiko Yoshino,* and Shigeki
Matsunaga*
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
e-mail: tyoshino@pharm.hokudai.ac.jp; smatsuna@pharm.hokudai.ac.jp
KEYWORDS: imidate, C–H functionalization, cobalt, allylation
ABSTRACT. Cobalt-catalyzed C–H allylation reactions of NH-free benzimidates using
vinylcyclopropanes or allyl carbonate are reported. The reactive and relatively unstable
imidate groups remain intact during the C–H allylations to afford functionalized imidates
without dealcoholizations. The thus obtained allylated imidate was subsequently
converted into other heterocyclic structures through a following C–H functionalization
reaction, demonstrating the synthetic utility of this method.
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Directing-group-assisted C–H activation/functionalization reactions using transition-
metal catalysts have developed into a powerful tool in modern organic synthesis.1
Although such reactions enable atom-2 and step-economical3 transformations and
straightforward access to complex molecules, the requirement of a directing group, which
facilitates inert C–H bond cleavage under mild conditions, can frequently compromise the
synthetic utility. This obstacle can be circumvented by using directing groups that work
as useful footholds for further transformations or by using reactive directing groups that
are involved in the C–H functionalization process to provide attractive structural motifs
such as heterocycles.1g
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In this context, NH-free imidates have recently emerged as reactive directing groups
that afford various N-containing heterocycles or carbocycles through directed C–H
functionalization reactions (Scheme 1a).4-8 On the other hand, a few reports9-11 have
revealed that the NH-free imidate groups can provide ortho-functionalized products
without cyclization (Scheme 1b and 1c): Wang and co-workers have reported
manganese-catalyzed C–H alkenylation reactions that involve alkynes,9a while Li and co-
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workers have developed cobalt-catalyzed C–H fluoroalkenylation reactions.9b These
transformations leave a functionality for subsequent manipulations, which is
commensurate with a considerable potential for successive derivatization after the C–H
functionalization reaction, rapidly increasing the complexity of the products. However,
under the reaction conditions applied in the above-mentioned cases, the imidate group
undergoes dealcoholization to give ortho-functionalized nitriles, which is due to the
intrinsic instability of the NH-free imidate moiety (Scheme 1b). More recently, Yang and
co-workers have reported rhodium-catalyzed oxidative C–H arylation reactions of
benzimidates, in which the directing imidate group survives under carefully controlled
reaction conditions, although the scope of applicable substrates has not been examined
(Scheme 1c).10
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Herein, we report that NH-free benzimidates undergo C–H allylations under retention
of an intact directing group using a cobalt catalyst12 and vinylcyclopropanes13 or allyl
carbonate14,15 as allylating agents (Scheme 1d). To demonstrate the synthetic utility of
this protocol, the allylated product, which still contains the reactive imidate group, was
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subsequently subjected to further C–H functionalization/cyclization reactions to afford
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functionalized N-heterocycles.
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Scheme 1. Directed C–H Functionalization of NH-free Benzimidates.
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OR1
N
(a) C–H functionalization/cyclization
(c) Oxidative C–H arylation with or without dealcoholization
NH
NH
OR
OR1
N
N
R2
NH
Rh, Co, Ir
OR
N
OR1
R2
CN
Ar
Rh cat.
Rh cat.
TFE, rt
Ru, Mn
OR1
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H
various
reagents
DME 120 °C
+
Ar
only
H
N
ArBPin
R2
2 examples
and etc.
R3
(d) This work: C–H allylation without dealcoholization
NH NH
(b) C–H functionalization/dealcoholization
CN
H
Wang et al.
NH
R1
Co cat.
further
R2
R1
Mn cat. +
OEt
OEt
X
X
R2
derivatization
OEt
CO2Me
CO2Me
H
Li et al.
H
CN
R1
R
F
F
Co cat. +
or
OCO2Et
R1
F
We speculated that cobalt(III)-catalyzed C–H allylation reactions could proceed
without dealcoholization, given that they often proceed under very mild conditions.15 Initial
trial experiments using benzimidate 1a, vinylcyclopropane 2a, Cp*CoI2(CO)/AgSbF6 (Cp*
= 1,2,3,4,5-pentamethylcyclopentadienyl), and KOAc in 1,2-dichloroethane afforded as
expected the desired allylation product (3aa) as the major product with moderate Z
selectivity together with a small amount of the corresponding nitrile (Table 1, entry 1). The
Z selectivity under Cp*CoIII-catalyzed conditions has previously been observed by
Ackermann and co-workers, and it would be controlled by some steric factors.13b
Significant solvent effects were not noticed for this reaction (entries 1–5), and we
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therefore selected 1,4-dioxane, which exhibited a slightly higher selectivity than the other
solvents examined (entry 3). The Z/E selectivity ratio improved significantly to 8/1 by using
the sterically more hindered cobalt catalyst Cp*iPrCoI2(CO), (Cp*iPr = 1-isopropyl-2,3,4,5-
tetramethylcyclopentadienyl, entry 6), albeit that the reactivity decreased slightly. When
we used CpMe4CoI2(CO) (CpMe4 = 1,2,3,4-tetramethylcyclopentadienyl) as the catalyst,
the selectivity was lower than Cp*CoI2(CO) (entry 7), indicating that the Z/E selectivity
would depend on the steric hindrance of the catalyst. The addition of AcOH instead of
KOAc improved the reactivity but decreased the Z selectivity (entry 8), while both
reactivity and selectivity improved when using PivOH (entry 9). The selectivity further
increased when the amount of AgSbF6 was increased (entry 10). Finally, after the
optimization of the reaction temperature and concentration (entries 11 and 12), 3aa was
isolated in 72% yield with a Z/E ratio of 18/1 (entry 12).
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Table 1. Optimization of the Reaction Conditions for Cobalt-catalyzed C–H Allylation of
Benzimidate 1a with Vinylcyclopropane 2a.a
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NH
NH
Me
catalyst (10 mol %)
AgSbF6 (X mol %)
additive (20 mol %)
Me
OEt
1a
OEt
+
MeO2C
3aa
solvent, 60 °C, 14 h
CO2Me
CO2Me
CO2Me
2a
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X
yieldb
(%)
entry catalyst
additive solvent
Z/Ec
(mol %)
1
2
3
4
5
6
7
8
9
10
Cp*CoI2(CO)
20
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
DCE
51 3/1
54 2/1
Cp*CoI2(CO)
Cp*CoI2(CO)
Cp*CoI2(CO)
Cp*CoI2(CO)
Cp*iPrCoI2(CO)
CpMe4CoI2(CO)
Cp*iPrCoI2(CO)
Cp*iPrCoI2(CO)
Cp*iPrCoI2(CO)
20
toluene
20
1,4-dioxane 53 4/1
20
THF
26 3/1
41 2/1
20
HFIP
20
1,4-dioxane 39 8/1
1,4-dioxane 27 2/1
20
20
AcOH 1,4-dioxane 59 3/1
PivOH 1,4-dioxane 56 9/1
PivOH 1,4-dioxane 62 12/1
PivOH 1,4-dioxane 65 12/1
PivOH 1,4-dioxane 72 18/1
20
40
11d Cp*iPrCoI2(CO)
12d,e Cp*iPrCoI2(CO)
40
40
aReaction conditions (unless otherwise noted): 1a (0.30 mmol), 2a (0.60 mmol), catalyst (0.03 mmol),
AgSbF6 (0.06–0.12 mmol), additive (0.06 mmol), solvent (3 mL, 0.1 M), 60 °C, 14 h. bIsolated yield of
the Z/E mixture. cDetermined by 1H NMR analysis of the isolated product. d65 °C. eSolvent (6 mL, 0.05
M); Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; Cp*iPr = 1-isopropyl-2,3,4,5-tetramethylcyclopentadienyl;
CpMe4 = 1,2,3,4-tetramethylcyclopentadienyl; DCE = 1,2-dichloroethane; HFIP = 1,1,1,3,3,3-hexafluoro-2-
propanol.
With the optimized conditions in hand, we examined the substrate scope of the Z-
selective allylation of benzimidates 1 using vinylcyclopropanes 2 (Scheme 2). A variety
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of benzimidates with an electron-donating or -withdrawing group underwent the C–H
allylation in 40%–72% yield with high Z selectivity. A disubstituted benzimidate (1g) and
2-naphthimidate (1h) smoothly provided the corresponding products (3ga and 3ha). In
addition to 2a, vinylcyclopropanes bearing ethoxycarbonyl (2b) or dibenzyloxycarbonyl
groups (2c) furnished the corresponding products with different ester groups in moderate
yield (3ab, 3ac). Although the yields were relatively moderate, the observed high levels
of Z selectivities (11/1–>20/1) are noteworthy even when compared to those observed in
the previous report.13b In most cases, unreacted imidate 1 was recovered together with a
small amount of the corresponding nitrile. Our attempts to achieve higher conversion were
unsuccessful because harsh reaction conditions led to the dealcoholization of 3.
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Scheme 2. Substrate Scope of the Cobalt-catalyzed C–H Allylation of Benzimidates 1
with Vinylcyclopropanes 2.a
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NH
NH
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OEt
Cp*iPrCoI2(CO) (10 mol %)
AgSbF6 (40 mol %)
OEt
X
X
1
PivOH (20 mol %)
+
RO2C
CO2R
CO2R
1,4-dioxane, 65 °C, 14 h
3
CO2R
2
NH
NH
OEt
X
Me
F
OEt
MeO2C
MeO2C
3ga
, 57% (>20/1)
CO2Me
CO2Me
NH
3aa
3ba
3ca
3da
3ea
, X = Me, 72% (18/1)
, X = H, 40% (>20/1)
, X = Cl, 48% (>20/1)
, X = Br, 51% (>20/1)
, X = Ac, 52% (11/1)
, X = CH2OPh 51% (>20/1)
OEt
MeO2C
3fa
b
3ha
, 43% (20/1)
CO2Me
NH
Me
OEt
3ab
3ac
, R = Et, 54% (>20/1)
, R = Bn, 53% (12/1)
RO2C
CO2R
aReactions conditions (unless otherwise noted): 1 (0.30 mmol), 2 (0.60 mmol), Cp*iPrCoI2(CO) (0.03
mmol), AgSbF6 (0.12 mmol), PivOH (0.06 mmol), 1,4-dioxane (6 mL, 0.05 M), 65 °C, 14 h. Isolated
yields are shown with the Z/E ratio in parentheses. b55 °C.
A simple allyl unit was successfully introduced using allyl carbonate 4 as the allylating
agent in the presence of [Cp*Co(CH3CN)3](SbF6)2 and KOAc (Scheme 3).14c Several
types of benzimidates 1 afforded the corresponding allyl arenes in moderate to good yield,
and only small amounts of nitriles were detected in all cases. When we used allyl alcohol
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as the allylating agent, the allylation reaction proceeded in moderate conversion, but the
isolation of the product was difficult due to the formation of several byproducts.
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Scheme 3. C–H Allylation Reactions with Allyl Carbonate 4.
6
NH
7
8
9
[Cp*Co(CH3CN)3](SbF6)2
OEt
NH
OEt
X
(10 mol %)
1
KOAc (20 mol %)
X
+
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OCO2Et
4
DCE, 60 °C, 14 h
5
NH
O
NH
OEt
NH
OEt
Cl
OEt Me
5c
5e
5h
, 59%
, 58%
, 63%
aReaction conditions: 1 (0.30 mmol), 4 (0.60 mmol), [Cp*Co(CH3CN)3](SbF6)2 (0.03 mmol), KOAc
(0.06 mmol), DCE (6 mL, 0.05 M), 60 °C, 14 h. Isolated yields are shown.
To demonstrate the synthetic utility of the allylated products, which contain a reactive
NH-free imidate group, we investigated subsequent transformations by further C–H
functionalization reactions (Scheme 4). A rhodium-catalyzed C–H amidation/cyclization
process using 3ba and dioxazolone 6 efficiently proceeded at the remaining C–H bond
ortho to the imidate, providing quinazoline 7 in 55% yield (Scheme 4a),4d and a C–H
alkylation/cyclization reaction using diazomalonate 8 afforded isoquinoline 9 in 62%
yield.4f The imidate group of 3ba, which remained intact during the preceding C–H
allylation reaction, clearly enabled these derivatizations. It is also noteworthy that the
formation of imidates from ortho-functionalized nitriles under the standard conditions are
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often difficult,10 indicating that C–H functionalizations without dealcoholization would be
important for the rapid access to these structural motifs.
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Scheme 4. Further Transformations of the Allylated Benzimidate Products.
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9
Ph
[Cp*RhCl2]2
(5 mol %)
AgBF4 (20 mol %)
NH
N
N
OEt
N O
OEt
6
10
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Ph
O
O
MeO2C
(a)
MeO2C
DCE, 50 °C, 13 h
55%
3ba
CO2Me
7
CO2Me
[Cp*RhCl2]2
(5 mol %)
AgSbF6 (20 mol %)
KOAc (20 mol %)
CO2Me
OH
NH
MeO2C
N
OEt
OEt
N2
8
MeO2C
CO2Me
MeO2C
(b)
CO2Me
3ba
CO2Me
DCE, 50 °C, 13 h
62%
9
In summary, we have found that NH-free benzimidates 1 undergo highly Z selective
C–H allylation reactions using vinylcyclopropanes 2 or C–H allylation reactions using allyl
carbonate 4 under cobalt-catalyzed conditions. As both reactions proceed under mild
conditions, the reactive imidate group can be preserved during the C–H functionalization
step. The imidate group can be used for further derivatization via a second C–H
functionalization reaction, leading to heterocyclic structures. The presented method might
thus provide facile access to multiply functionalized molecules with complex architectures
that might find a variety of applications.
Experimental Section
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General Methods. Reported melting points were uncorrected. Infrared (IR) spectra were recorded
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on a JASCO FT/IR-5300 spectrophotometer and absorbance bands are reported in wave numbers (cm-1).
NMR spectra were recorded on JEOL JNM-ECS400 spectrometers operating at 391.78 MHz for 1H NMR
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and 98.52 MHz for C{1H} NMR, JOEL JNM-ECX400 spectrometers, operating at 395.88 MHz for H
NMR and 99.55 MHz for 13C{1H} NMR, and JEOL JNM-ECP400 spectrometers operating at 399.78 MHz
for 1H NMR and 100.53 MHz for 13C{1H} NMR. Chemical shifts were reported in the scale relative to TMS
(0.00 ppm for 1H NMR), CHCl3 (7.26 ppm for 1H NMR), C6H6 (7.16 ppm for 1H NMR), CDCl3 (77.0 ppm
for 13C{1H} NMR) as an internal reference, respectively. ESI mass spectra were measured on JEOL JMS-
T100LCP spectrometer. Silica gel column chromatography was performed with Kanto Silica gel 60 N (40-
50 mesh). 1,1,1,3,3,3-Hexafluoropropan-2-ol were distilled from CaH2, purged with argon for over
30 min, and stored over activated molecular sieves 4A under argon atmosphere before use.
Commercially available THF, toluene, 1,4-dioxane (Wako Ltd., deoxydeized grade), and 1,2-
dichloroethane (Kanto Ltd., super dehyderated grade) were used without further manipulation unless
otherwise stated. Imidates were synthesized according to the literature.4f Vinylcyclopropanes 2a,16a 2b,16b
and 2c16a were synthesized according to the literature. All other reagents were commercially available and
used as received.
Preparation of Cp*iPrCoI2(CO). Cp*iPrCoI2(CO) was synthesized according to the litrature.17 To a well-
dried 2-necked 500-mL flask were successively added Co2(CO)8 (1.0 g, 3.0 mmol), degassed CH2Cl2 (8.5
mL), 1,3-cyclohexadiene (358 mg, 4.47 mmol, 1.5 equiv.) and 5-isopropyl-1,2,3,4-tetramethylcyclopenta-
1,3-diene (1.3 g, 6.9 mmol, 2.3 equiv.). The mixture was refluxed by heating in an oil bath under argon
stream for 6 h and then cooled to room temperature. The solvent was removed in vacuo. The residue was
dissolved in degassed Et2O (13 mL) and then iodine (1.5 g, 6.0 mmol, 2.0 equiv.) in degassed Et2O (10 mL)
was added dropwise at room temperature with stirring. After the mixture was stirred at room temperature
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for 1 h, the solvent was evaporated. The resulting precipitates were collected by filtration and washed with
Et2O to afford Cp*iPrCoI2(CO) as a black solid (1.1 g, 2.2 mmol, 37%). IR (KBr)  2959, 2029, 1469, 1378,
1011 cm-1; 1H NMR (400 MHz, CDCl3) 1.38 (d, J = 6.8 Hz, 6H), 2.26 (s, 6H), 2.32 (s, 6H), 2.90 (sep, J =
6.8 Hz, 1H); 13C{1H} NMR (100 MHz, CDCl3)  11.6, 12.2, 22.0, 25.9, 101.6, 101.9, 105.3; The CO signal
was not observed in the 13C NMR, but the strong IR absorption at 2029 cm-1 indicated the presence of the
CO ligand.
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CpMe4CoI2(CO) was prepared according to the literature.18
Procedure for the Preparation of Imidates 1. To a round bottom flask were added an aryl nitrile (1.0
equiv.) and ethanol (12 equiv.). The mixture was cooled with ice/water bath and AcCl (8.0 equiv.) was
added dropwise. The reaction mixture was stirred at room temperature for 12 h, and the solvent was
removed under reduced pressure. To the residue was added saturated aq. NaHCO3 solution, and the mixture
was extracted with EtOAc. The combined organic layers were successively washed with H2O and brine,
and dried over Na2SO4. After filtration and evaporation, the obtained crude mixture was purified by silica
gel column chromatography to give the corresponding imidate 1.
Ethyl 3-(phenoxymethyl)benzimidate (1f). Title compound was obtained from ethanol (1.1 g, 24 mmol, 12
equiv.), the corresponding nitrile (419 mg, 2.0 mmol, 1.0 equiv.), and AcCl (1.3 g, 16 mmol, 8.0 equiv.)
after silica gel column chromatography (hexane/AcOEt = 4/1). Yield: 78% (401 mg); colorless oil; IR (neat)
 2979, 1634, 1599, 1496, 1373, 1329, 1240, 1078, 754 cm-1; 1H NMR (400 MHz, CDCl3)  1.39 (t, J =
7.1 Hz, 3H), 4.30 (q, J = 7.1 Hz, 2H), 5.01 (s, 2H), 6.90-6.98 (m, 3H), 7.22-7.29 (m, 2H), 7.36 (dd, J = 7.7,
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7.7 Hz, 1H), 7.48 (d, J = 7.7 Hz, 1H), 7.66 (d, J = 7.7 Hz, 1H), 7.79 (s, 1H); C{1H} NMR (100 MHz,
CDCl3)  13.7, 61.2, 68.9, 114.3, 120.6, 125.2, 125.7, 128.1, 129.0, 129.2, 132.8, 137.0, 158.0, 166.8;
HRMS (ESI-Orbitrap): m/z calculated for C16H18O2N [M+H+]: 256.1332, found: 256.1333.
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Ethyl 4-fluoro-3-methylbenzimidate (1g). Title compound was obtained from ethanol (2.8 g, 60 mmol, 12
equiv.), the corresponding nitrile (678 mg, 5.0 mmol, 1.0 equiv.), and AcCl (3.1 g, 40 mmol, 8.0 equiv.)
after silica gel column chromatography (hexane/AcOEt = 4/1). Yield: 85% (768 mg); colorless oil; IR (neat)
 2981, 1637, 1504, 1371, 1329, 1246, 1204, 1075, 825 cm-1; 1H NMR (400 MHz, CDCl3)  1.42 (t, J =
7.0 Hz, 3H), 2.31 (d, J = 1.9 Hz, 3H), 4.30 (q, J = 7.0 Hz, 2H), 7.02 (dd, J = 8.9, 8.9 Hz, 1H), 7.48-7.68
(m, 3H); 13C{1H} NMR (100 MHz, CDCl3)  13.8, 14.0, 61.3, 114.5 (2JCF = 23.0 Hz), 124.5 (2JCF = 17.7
Hz), 125.8 (3JCF = 8.6 Hz), 128.5 (4JCF = 2.1 Hz), 129.8 (3JCF = 5.2 Hz), 162.5 (1JCF = 250.8 Hz), 166.2;
HRMS (ESI-Orbitrap): m/z calculated for C10H13ONF [M+H+]: 182.0976, found: 182.0978.
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The other imidates 1 were previously reported.4f,4j,19
General Procedure for the Cobalt-Catalyzed C–H Allylation of Imidates with Vinylcyclopropanes.
To a dried screw-capped test tube were added Cp*iPrCoI2(CO) (15.1 mg, 0.03 mmol, 10 mol %), AgSbF6
(41.2 mg, 0.12 mmol, 40 mol %), PivOH (6.1 mg, 0.06 mmol, 20 mol %), imidate 1 (0.3 mmol),
vinylcyclopropane 2 (0.6 mmol, 2.0 equiv.), and 1,4-dioxane (6.0 mL, 0.05 M) under Ar atmosphere in a
glovebox. The test tube was capped and heated at 65 ºC for 14 h in an oil bath with stirring. After the
mixture was cooled to room temperature, saturated aq. EDTA•2Na solution was added. After dilution with
CH2Cl2, the organic layer was separated, and the aqueous layer was extracted with CH2Cl2 three times. The
combined organic layers were dried over Na2SO4. After filtration and evaporation, the obtained crude
mixture was purified by silica gel column chromatography to give corresponding product 3. Yields were
determined at this stage as a combined yield of the Z/E isomers. The Z/E ratio was determined by the 1H
NMR analysis of the isolated product. The separation of the Z/E isomers was difficult, and only HPLC
using DASICEL CHIRALPAK ID (hexane/IPA = 19/1) on a small scale was successful. Therefore, only
the aliquot of 3aa was separated for characterization, and other products (Z isomer) were characterized
without separation.
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Dimethyl (Z)-2-(4-(2-(ethoxy(imino)methyl)-4-methylphenyl)but-2-en-1-yl)malonate (3aa). 3aa was
purified by silica gel column chromatography (CH2Cl2/AcOEt = 20/1 to 5/1). The pure isomer for
characterization was obtained by further purification by HPLC using DASICEL CHIRALPAK ID
(hexane/IPA = 19/1). Yield: 72% (75.0 mg, Z/E = 18/1); yellow oil; IR (neat)  2953, 2360, 1738, 1639,
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1437, 1330, 1231, 1155, 1069 cm-1; 1H NMR (400 MHz, CDCl3)  1.39 (t, J = 7.1 Hz, 3H), 2.32 (s, 3H),
2.75 (dd, J = 7.6, 7.5 Hz, 2H), 3.41-3.48 (m, 3H), 3.74 (s, 6H), 4.32 (q, J = 7.1 Hz, 2H), 5.41 (dtt, J = 10.8,
7.5, 1.6 Hz, 1H), 5.61 (dtt, J = 10.8, 7.2, 1.5 Hz, 1H), 7.06-7.17 (m, 3H); 13C NMR{1H} (100 MHz, CDCl3)
 14.2, 20.8, 26.8, 30.8, 51.5, 52.5, 61.9, 125.4, 128.2, 129.6, 130.4, 131.4, 134.4, 135.5, 135.9, 169.3,
170.7; HRMS (ESI-Orbitrap): m/z calculated for C19H26O5N [M+H+]: 348.1806, found: 348.1806.
Dimethyl (E)-2-(4-(2-(ethoxy(imino)methyl)-4-methylphenyl)but-2-en-1-yl)malonate (3aa). yellow oil; IR
(neat)  2953, 1738, 1640, 1437, 1330, 1230, 1155, 1070 cm-1; 1H NMR (400 MHz, CDCl3)  : 1.39 (t, J =
7.2 Hz, 3H), 2.32 (s, 3H), 2.60 (dd, J = 7.2, 7.1 Hz, 2H), 3.34 (d, J = 6.5 Hz, 2H), 3.41 (t, J = 7.2 Hz, 1H),
3.70 (s, 6H), 4.30 (q, J = 7.2 Hz, 2H), 5.39 (dt, J = 15.3, 7.1 Hz, 1H), 5.67 (dt, J = 15.3, 6.5 Hz, 1H), 7.06
(d, J = 8.0 Hz, 1H), 7.11-7.18 (m, 2H); 13C{1H} NMR (100 MHz, CDCl3) 14.2, 20.8, 31.8, 36.1, 51.7, 52.4,
61.8, 126.8, 128.2, 129.9, 130.4, 132.6, 134.0, 135.4, 136.0, 169.3, 170.4; HRMS (ESI-Orbitrap): m/z
calculated for C19H26O5N [M+H+]: 348.1806, found: 348.1806.
Dimethyl (Z)-2-(4-(2-(ethoxy(imino)methyl)phenyl)but-2-en-1-yl)malonate (3ba). 3ba was purified by
silica gel column chromatography (hexane/Et2O = 2/1 to 1/4). Yield: 40% (40.0 mg, Z/E = >20/1); colorless
oil; IR (neat)  2953, 1738, 1636, 1437, 1373, 1331, 1235, 1160, 1070 cm-1; 1H NMR (400 MHz, CDCl3)
 1.39 (t, J = 7.1 Hz, 3H), 2.73-2.79 (m, 2H), 3.45 (t, J = 7.6 Hz, 1H), 3.50 (d, J = 7.3 Hz, 2H), 3.74 (s,
6H), 4.33 (q, J = 7.1 Hz, 2H), 5.43 (dtt, J = 10.8, 7.4, 1.7 Hz, 1H), 5.63 (dtt, J = 10.8, 7.3, 1.6 Hz, 1H),
7.18-7.25 (m, 2H), 7.30-7.37 (m, 2H); 13C{1H} NMR (100 MHz, CDCl3)  14.1, 26.8, 31.1, 51.4, 52.5,
61.9, 125.7, 126.2, 127.6, 129.6, 129.7, 131.1, 135.6, 137.4, 169.3, 170.6; HRMS (ESI-Orbitrap): m/z
calculated for C18H24O5N [M+H+]: 334.1649, found: 334.1649.
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Dimethyl (Z)-2-(4-(4-chloro-2-(ethoxy(imino)methyl)phenyl)but-2-en-1-yl)malonate (3ca). 3ca was
purified by silica gel column chromatography (hexane/Et2O = 2/1 to 1/3). Yield: 48% (53.5 mg, Z/E =
>20/1); colorless oil; IR (neat)  2953, 1737, 1641, 1437, 1328, 1068 cm-1; 1H NMR (400 MHz, CDCl3) 
1.39 (t, J = 7.1 Hz, 3H), 2.74 (dd, J = 7.6, 7.2 Hz, 2H), 3.41-3.50 (m, 3H), 3.74 (s, 6H), 4.32 (q, J = 7.1 Hz,
2H), 5.39-5.50 (m, 1H), 5.58 (dt, J = 10.6, 7.2 Hz, 1H), 7.15 (d, J = 8.3 Hz, 1H), 7.26-7.43 (m, 3H); 13C{1H}
NMR (100 MHz, CDCl3)  14.1, 26.8, 30.6, 51.4, 52.5, 62.1, 126.2, 127.6, 129.7, 130.5, 131.0, 131.9,
136.0, 137.0, 168.9, 169.2; HRMS (ESI-Orbitrap): m/z calculated for C18H23O5NCl [M+H+]: 368.1259,
found: 368.1259.
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Dimethyl (Z)-2-(4-(4-bromo-2-(ethoxy(imino)methyl)phenyl)but-2-en-1-yl)malonate (3da). 3da was
purified by silica gel column chromatography (hexane/Et2O = 2/1 to 1/2). Yield: 51% (62.9 mg, Z/E =
>20/1); colorless oil; IR (neat)  2953, 1737, 1640, 1437, 1327, 1235, 1162, 1068, 875 cm-1; 1H NMR (400
MHz, CDCl3)  1.39 (t, J = 7.1 Hz, 3H), 2.74 (dd, J = 7.5, 7.4 Hz, 2H), 3.41-3.47 (m, 3H), 3.74 (s, 6H),
4.31 (q, J = 7.1 Hz, 2H), 5.44 (dt, J = 10.7, 7.4 Hz, 1H), 5.57 (dt, J = 10.7, 7.2 Hz, 1H), 7.09 (d, J = 8.3 Hz,
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1H), 7.35 (brs, 1H), 7.42-7.51 (m, 2H); C{1H} NMR (100 MHz, CDCl3)  14.1, 26.8, 30.7, 51.4, 52.5,
62.1, 119.8, 126.2, 130.4, 131.3, 132.6, 136.5, 137.3, 168.8, 169.2; one of the aromatic signal was missing
probably due to overlapping; HRMS (ESI-Orbitrap): m/z calculated for C18H23O5NBr [M+H+]: 412.0754,
found: 412.0757.
Dimethyl (Z)-2-(4-(4-acetyl-2-(ethoxy(imino)methyl)phenyl)but-2-en-1-yl)malonate (3ea). 3ea was
purified by silica gel column chromatography (hexane/Et2O = 1/2 to 1/4). Yield: 52% (59.1 mg, Z/E =
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11/1); yellow oil; IR (neat)  2954, 1736, 1685, 1643, 1436, 1257, 1159, 1066, 839 cm-1; H NMR (400
MHz, C6D6)  1.19 (t, J = 7.1 Hz, 3H), 2.06 (s, 3H), 2.81 (dd, J = 7.5, 7.4 Hz, 2H), 3.32 (s, 6H), 3.39 (t, J
= 7.5 Hz, 1H), 3.49 (d, J = 7.0 Hz, 2H), 4.15-4.50 (m, 2H), 5.40 (dt, J = 10.6, 7.4 Hz, 1H), 5.53 (dt, J =
10.6, 7.0 Hz, 1H), 7.05 (d, J = 8.0 Hz, 1H), 7.47 (brs, 1H), 7.73 (d, J = 8.0 Hz, 1H), 7.91 (s, 1H); 13C{1H}
NMR (100 MHz, CDCl3)  14.1, 26.5, 26.8, 31.2, 51.3, 52.5, 62.1, 126.5, 127.7, 129.3, 129.9, 130.0, 135.2,
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136.0, 142.9, 169.2, 169.4, 196.9; HRMS (ESI-Orbitrap): m/z calculated for C20H26O6N [M+H+]: 376.1755,
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Dimethyl (Z)-2-(4-(2-(ethoxy(imino)methyl)-4-(phenoxymethyl)phenyl)but-2-en-1-yl)malonate (3fa). 3fa
was purified by silica gel column chromatography (hexane/Et2O = 2/1 to 1/2). Yield: 51% (67.2 mg, Z/E =
>20/1); orange oil; IR (neat)  2952, 1737, 1639, 1496, 1330, 1237, 1155, 1069, 755 cm-1; 1H NMR (400
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MHz, CDCl3)  1.39 (t, J = 7.1 Hz, 3H), 2.76 (dd, J = 7.6, 7.5 Hz, 2H), 3.45 (t, J = 7.6 Hz, 1H), 3.50 (d, J
= 7.1 Hz, 2H), 3.74 (s, 6H), 4.33 (q, J = 7.1 Hz, 2H), 5.03 (s, 2H), 5.43 (dtt, J = 10.7, 7.5, 1.6 Hz, 1H), 5.62
(dtt, J =10.7, 7.1, 1.4 Hz, 1H), 6.93-7.00 (m, 3H), 7.23 (d, J = 7.9 Hz, 1H), 7.25-7.33 (m, 2H), 7.37-7.44
(m, 2H); 13C{1H} NMR (100 MHz, CDCl3)  14.1, 26.8, 30.9, 51.4, 52.5, 62.0, 69.2, 114.7, 121.0, 125.8,
126.7, 128.8, 129.5, 129.9, 131.0, 135.2, 135.8, 137.2, 158.6, 169.2, 170.2; HRMS (ESI-Orbitrap): m/z
calculated for C25H30O6N [M+H+]: 440.2068, found: 440.2066.
Dimethyl (Z)-2-(4-(2-(ethoxy(imino)methyl)-5-fluoro-4-methylphenyl)but-2-en-1-yl)malonate (3ga). 3ga
was purified by silica gel column chromatography (hexane/Et2O = 2/1 to 1/2). Yield: 57% (62.5 mg, Z/E =
>20/1); colorless oil; IR (neat)  2954, 1737, 1639, 1437, 1329, 1157, 1092, 867 cm-1; 1H NMR (400 MHz,
CDCl3)  1.39 (t, J = 7.1 Hz, 3H), 2.24 (d, J = 1.2 Hz, 3H), 2.74 (dd, J = 7.5, 7.4 Hz, 2H), 3.41-3.48 (m,
3H), 3.75 (s, 6H), 4.30 (q, J = 7.1 Hz, 2H), 5.45 (dtt, J = 10.7, 7.4, 1.2 Hz, 1H), 5.59 (dtt, J = 10.7, 7.2, 1.4
Hz, 1H), 6.85 (d, J = 10.6 Hz, 1H), 7.18 (d, J = 7.7 Hz, 1H); 13C{1H} NMR (100 MHz, CDCl3)  13.9 (3J
= 3.2 Hz), 14.1, 26.7, 30.7 (4J = 1.5 Hz), 51.4, 52.5, 61.9, 115.9 (2J = 23.0 Hz), 122.7 (2J = 17.9 Hz), 126.2,
130.5, 130.9 (3J = 5.7 Hz), 131.3 (4J = 3.3 Hz), 137.5 (3J = 7.6 Hz), 161.7 (1J = 249.1 Hz), 169.2, 169.7;
HRMS (ESI-Orbitrap): m/z calculated for C19H25O5NF [M+H+]: 366.1711, found: 366.1709.
Dimethyl (Z)-2-(4-(3-(ethoxy(imino)methyl)naphthalen-2-yl)but-2-en-1-yl)malonate (3ha). 3ha was
purified by silica gel column chromatography (hexane/Et2O = 2/1 to 1/4). Yield: 43% (49.5 mg, Z/E =
20/1); IR (neat)  2952, 1737, 1640, 1437, 1338, 1152, 1095, 1055, 753 cm-1; 1H NMR (400 MHz, CDCl3)
 1.43 (t, J = 7.1 Hz, 3H), 2.76-2.84 (m, 2H), 3.47 (t, J = 7.6 Hz, 1H), 3.66 (d, J = 7.4 Hz, 2H), 3.73 (s,
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6H), 4.38 (q, J = 7.1 Hz, 2H), 5.51 (dtt, J = 10.8, 7.2, 1.8 Hz, 1H), 5.73 (dtt, J = 10.8, 7.4, 1.3 Hz, 1H),
7.43-7.53 (m, 3H), 7.65 (s, 1H), 7.78 (d, J = 7.6 Hz, 1H), 7.81 (d, J = 7.6 Hz, 1H), 7.86 (s, 1H); 13C{1H}
NMR (100 MHz, CDCl3)  14.2, 26.8, 31.2, 51.5, 52.5, 62.1, 126.0, 127.0, 127.2, 127.5, 127.8, 128.0,
131.0, 131.4, 133.8, 134.4, 134.6, 169.3, 170.7; one of the aromatic signal was missing probably due to
overlapping; HRMS (ESI-Orbitrap): m/z calculated for C22H26O5N [M+H+]: 384.1806, found: 384.1804.
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Diethyl (Z)-2-(4-(2-(ethoxy(imino)methyl)-4-methylphenyl)but-2-en-1-yl)malonate (3ab). 3ab was purified
by silica gel column chromatography (hexane/Et2O = 2/1 to 1/2). Yield: 54% (61.3 mg, Z/E = >20/1);
orange oil; IR (neat)  2980, 1732, 1639, 1370, 1330, 1229, 1069, 861 cm-1; 1H NMR (400 MHz, CDCl3)
 1.27 (t, J = 7.1 Hz, 6H), 1.39 (t, J = 7.1 Hz, 3H), 2.32 (s, 3H), 2.74 (dd, J = 7.5, 6.8 Hz, 2H), 3.39 (t, J =
7.5 Hz, 1H), 3.45 (d, J = 7.1 Hz, 2H), 4.20 (q, J = 7.1 Hz, 4H), 4.32 (q, J = 7.1 Hz, 2H), 5.42 (dtt, J = 10.8,
6.8, 1.6 Hz, 1H), 5.59 (dtt, J = 10.8, 7.1, 1.4 Hz, 1H), 7.06-7.18 (m, 3H); 13C{1H} NMR (100 MHz, CDCl3)
 14.0, 14.1, 20.7, 26.7, 30.8, 51.8, 61.4, 61.9, 125.6, 128.1, 129.6, 130.4, 131.2, 134.4, 135.5, 135.8, 168.9,
170.7; HRMS (ESI-Orbitrap): m/z calculated for C21H30O5N [M+H+]: 376.2119, found: 376.2117.
Dibenzyl (Z)-2-(4-(2-(ethoxy(imino)methyl)-4-methylphenyl)but-2-en-1-yl)malonate (3ac). 3ac was
purified by silica gel column chromatography (CH2Cl2/AcOEt = 20/1 to 5/1). Yield: 53% (79.2 mg, Z/E =
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12/1); brown oil; IR (neat)  2978, 1733, 1637, 1372, 1330, 1152, 1069, 697 cm-1; H NMR (400 MHz,
CDCl3)  1.36 (t, J = 7.1 Hz, 3H), 2.31 (s, 3H), 2.78 (dd, J = 7.6, 7.2 Hz, 2H), 3.40 (d, J = 6.9 Hz, 2H), 3.52
(t, J = 7.6 Hz, 1H), 4.29 (q, J = 7.1 Hz, 2H), 5.14 (s, 4H), 5.35-5.46 (m, 1H), 5.57 (dt, J = 10.8, 6.9 Hz,
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1H), 7.03-7.16 (m, 3H), 7.24-7.35 (m, 10H); C{1H} NMR (100 MHz, CDCl3)  14.1, 20.8, 26.7, 30.8,
51.8, 61.9, 67.1, 125.4, 128.1, 128.3, 128.5, 129.6, 130.4, 131.5, 134.4, 135.3, 135.5, 135.8, 168.6, 170.6;
one of the aromatic signal was missing probably due to overlapping; HRMS (ESI-Orbitrap): m/z calculated
for C31H34O5N [M+H+]: 500.2432, found: 500.2431.
General Procedure for the Cobalt-Catalyzed C–H Allylation of Imidates with Allyl Carbonate. To a
dried screw-capped vial were added [Cp*Co(CH3CN)3](SbF6)2 (23.7 mg, 0.03 mmol, 10 mol %), KOAc
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(5.9 mg, 0.06 mmol, 20 mol %), imidate 1 (0.3 mmol), allyl carbonate 4 (78.1 mg, 0.6 mmol, 2.0 equiv.),
and DCE (3.0 mL, 0.1 M) under Ar atmosphere in a glovebox. The vial was capped and heated at 60 ºC for
14 h on an aluminum heating block with stirring. After the mixture was cooled to room temperature,
saturated aq. EDTA•2Na was added. After dilution with CH2Cl2, the organic layer was separated, and the
aqueous layer was extracted with CH2Cl2 three times. The combined organic layers were dried over Na2SO4.
After filtration and evaporation, the obtained crude mixture was purified by silica gel column
chromatography to give corresponding product 5.
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Ethyl 2-allyl-5-chlorobenzimidate (5c). 5c was purified by silica gel column chromatography (hexane/Et2O
= 4/1 to 2/1). Yield: 58% (39.1 mg); yellow oil; IR (neat)  2979, 1639, 1412, 1369, 1327, 1067, 997, 882
cm-1; 1H NMR (400 MHz, CDCl3)  1.39 (t, J = 7.1 Hz, 3H), 3.42 (d, J = 6.2 Hz, 2H), 4.31 (q, J = 7.1 Hz,
2H), 5.00 (ddt, J = 16.8, 1.6, 1.6 Hz, 1H), 5.10 (dd, J = 10.1, 1.6 Hz, 1H), 5.94 (ddt, J = 16.8, 10.1, 6.2 Hz,
1H), 7.16 (d, J = 8.3 Hz, 1H), 7.31 (dd, J = 8.3, 2.3 Hz, 1H), 7.34-7.52 (m, 2H); 13C{1H} NMR (100 MHz,
CDCl3)  14.1, 37.2, 62.1, 116.5, 127.7, 129.6, 131.6, 132.1, 135.3, 136.7, 136.9, 168.6; HRMS (ESI-
Orbitrap): m/z calculated for C12H15ONCl [M+H+]: 224.0837, found: 224.0839.
Ethyl 5-acetyl-2-allylbenzimidate (5e). 5e was purified by silica gel column chromatography (hexane/Et2O
= 4/1 to 2/1). Yield: 63% (43.4 mg); orange oil; IR (neat)  2979, 1634, 1372, 1318, 1147, 1093, 1056, 913,
750 cm-1; 1H NMR (400 MHz, CDCl3)  1.41 (t, J = 7.1 Hz, 3H), 2.60 (s, 3H), 3.52 (d, J = 6.3 Hz, 2H),
4.34 (q, J = 7.1 Hz, 2H), 5.04 (ddt, J = 16.8, 1.6, 1.6 Hz, 1H), 5.12 (ddt, J = 10.1, 1.6, 1.5 Hz, 1H), 5.96
(ddt, J = 16.8, 10.1, 6.3 Hz, 1H), 7.34 (d, J = 8.0 Hz, 1H), 7.44 (brs, 1H), 7.89-7.99 (m, 2H); 13C{1H} NMR
(100 MHz, CDCl3)  14.1, 26.5, 37.8, 62.1, 116.9, 127.8, 129.2, 130.5, 135.3, 135.9, 136.1, 142.3, 169.2,
197.0; HRMS (ESI-Orbitrap): m/z calculated for C14H18O2N [M+H+]: 232.1332, found: 232.1333.
Ethyl 3-allyl-2-naphthimidate (5h). 5f was purified by silica gel column chromatography (hexane/Et2O =
4/1 to 1/1). Yield: 59% (42.7 mg); yellow oil; IR (neat)  2979, 1686, 1642, 1371, 1330, 1256, 1066, 918,
840 cm-1; 1H NMR (400 MHz, CDCl3)  1.43 (t, J = 7.1 Hz, 3H), 3.63 (d, J = 6.5 Hz, 2H), 4.38 (q, J = 7.1
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Hz, 2H), 5.08 (ddt, J = 16.9, 1.7, 1.6 Hz, 1H), 5.13 (ddt, J = 10.2, 1.6, 1.5 Hz, 1H), 6.06 (ddt, J = 16.9, 10.2,
6.5 Hz, 1H), 7.39-7.60 (m, 3H), 7.67 (s, 1H), 7.78 (d, J = 7.9 Hz, 1H), 7.82 (d, J = 7.8 Hz, 1H), 7.88 (s,
1H); 13C{1H} NMR (100 MHz, CDCl3)  14.2, 37.9, 62.0, 116.4, 126.1, 127.0, 127.2, 127.6, 127.9, 128.7,
131.5, 133.8, 134.1, 134.3, 137.1, 170.4; HRMS (ESI-Orbitrap): m/z calculated for C16H18ON [M+H+]:
240.1383, found: 240.1385.
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Procedure for the Transformation Reaction of 3ba with Dioxazolone 6. To a dried screw-capped vial
were added [Cp*RhCl2]2 (0.9 mg, 0.0015 mmol, 5 mol %), AgBF4 (1.2 mg, 0.006 mmol, 20 mol %), 3ba
(10 mg, 0.03 mmol), dioxazolone 6 (7.3 mg, 0.045 mmol, 1.5 equiv.), and DCE (0.15 mL, 0.2 M) under Ar
atmosphere in a glovebox. The vial was capped and heated at 50 ºC for 13 h on an aluminum heating block
with stirring. After cooling to room temperature, the mixture was filtered through a short pad of silica gel
and evaporated. The crude mixture was purified by silica gel column chromatography (hexane/AcOEt =
10/1 to 5/1) to give corresponding product 7 as a colorless solid (7.2 mg, 0.017 mmol, 55%).
Dimethyl (Z)-2-(4-(4-ethoxy-2-phenylquinazolin-5-yl)but-2-en-1-yl)malonate 7). mp: 92.8–94.5 ºC; IR
1
(KBr)  1747, 1577, 1557, 1499, 1328, 1241, 1203, 1065, 794, 715 cm-1; H NMR (400 MHz, CDCl3) 
1.57 (t, J = 7.1 Hz, 3H), 2.83 (dd, J = 7.6, 7.5 Hz, 2H), 3.47 (t, J = 7.6 Hz, 1H), 3.74 (s, 6H), 4.08 (d, J =
7.1 Hz, 2H), 4.79 (q, J = 7.1 Hz, 2H), 5.45 (dt, J = 10.6, 7.5 Hz, 1H), 5.80 (dt, J =10.6, 7.1 Hz, 1H), 7.32
(d, J = 7.4 Hz, 1H), 7.42-7.56 (m, 3H), 7.68 (dd, J = 8.0, 7.5 Hz, 1H), 7.86 (d, J = 8.0 Hz, 1H), 8.51-8.61
(m, 2H); 13C{1H} NMR (100 MHz, CDCl3)  14.3, 27.0, 33.9, 51.6, 52.6, 63.0, 114.4, 125.2, 126.8, 127.9,
128.3, 128.4, 130.4, 131.9, 132.8, 138.0, 138.8, 153.9, 159.2, 167.2, 169.4; HRMS (ESI-Orbitrap): m/z
calculated for C25H27O5N2 [M+H+]: 435.1915, found: 435.1913.
Procedure for the Transformation Reaction of 3ba with Diazomalonate 8. To a dried screw-capped
vial were added [Cp*RhCl2]2 (0.9 mg, 0.0015 mmol, 5 mol %), AgSbF6 (2.1 mg, 0.006 mmol, 20 mol %),
KOAc (0.6 mg, 0.006 mmol, 20 mol %), 3ba (10 mg, 0.03 mmol), diazomalonate 8 (7.1 mg, 0.045 mmol,
1.5 equiv.), and DCE (0.15 mL, 0.2 M) under Ar atmosphere in a glovebox. The vial was capped and heated
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at 50 ºC for 13 h on an aluminum heating block with stirring. After cooling to room temperature, the mixture
was filtered by a short pad of silica gel and evaporated. The crude mixture was purified by silica gel column
chromatography (hexane/AcOEt = 4/1 to 2/1) to give corresponding product 9 as a colorless amorphous
(8.0 mg, 0.019 mmol, 62%).
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Dimethyl (Z)-2-(4-(1-ethoxy-3-hydroxy-4-(methoxycarbonyl)isoquinolin-8-yl)but-2-en-1-yl)malonate (9).
IR (neat)  1737, 1641, 1577, 1514, 1454, 1321, 1253, 1055, 964, 821 cm-1; 1H NMR (400 MHz, CDCl3)
 1.50 (t, J = 7.1 Hz, 3H), 2.80 (dd, J = 7.7, 7.5 Hz, 2H), 3.45 (t, J = 7.7 Hz, 1H), 3.74 (s, 6H), 4.04 (d, J =
7.1 Hz, 2H), 4.07 (s, 3H), 4.65 (q, J = 7.1 Hz, 2H), 5.41 (ddt, J = 10.7, 7.5, 1.7 Hz, 1H), 5.74 (ddt, J = 10.7,
7.1, 1.5 Hz, 1H), 7.20 (d, J = 7.0 Hz, 1H), 7.54 (dd, J = 8.7, 7.0 Hz, 1H), 8.59 (d, J = 8.7 Hz, 1H), 13.1 (s,
1H); 13C{1H} NMR (100 MHz, CDCl3)  14.2, 27.0, 35.1, 51.6, 52.5, 52.6, 63.9, 92.3, 115.2, 123.1, 124.9,
126.6, 131.8, 132.3, 139.8, 140.3, 165.4, 166.3, 169.4, 172.7; HRMS (ESI-Orbitrap): m/z calculated for
C22H26O8N [M+H+]: 432.1653, found: 432.1654.
ASSOCIATED CONTENT
Supporting Information. The following file is available free of charge.
NMR spectra of the synthesized compounds (PDF).
AUTHOR INFORMATION
Corresponding Author
*E-mail for T.Y.: tyoshino@pharm.hokudai.ac.jp
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*E-mail for S.M.: smatsuna@pharm.hokudai.ac.jp
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Notes
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The authors declare no competing financial interest.
ACKNOWLEDGMENT
This work was supported in part by JSPS KAKENHI Grant Number JP15H05802 in
Precisely Designed Catalysts with Customized Scaffolding, JP18H04637 in Hybrid
Catalysis, and JP19K16306.
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