Rh-Catalyzed Regioselective ortho-C-H Carbenoid Insertion of Diarylazines

Article abstract of DOI:10.1021/acs.joc.7b01472

The Rh-catalyzed ortho-C-H carbenoid insertion reaction of diarylazines with diazo compounds has been developed. A wide range of ortho-substituted diarylazines have been obtained in moderate to high yields with high regioselectivity at room temperature. The hydrolysis of the products could release ketones or aldehydes, giving access to aromatic 1,5-keto-diesters as valuable synthons for further chemical transformations.

Full text of DOI:10.1021/acs.joc.7b01472

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Article
Rh-catalyzed Regioselective ortho-C-H Carbenoid Insertion of Diarylazines
Yunliang Yu, Changsheng Kuai, Remi Chauvin, Nian Tian, Shuangshuang Ma, and Xiuling Cui
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b01472 • Publication Date (Web): 19 Jul 2017
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Rh-catalyzed Regioselective ortho-C-H Carbenoid
Insertion of Diarylazines
Yunliang Yu, Changsheng Kuai, Remi Chauvin,*,† Nian Tian, Shuangshuang Ma and
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Xiuling Cui*
Engineering Research Center of Molecular Medicine of Ministry of Education, Key
Laboratory of Fujian Molecular Medicine, Key Laboratory of Xiamen Marine and
Gene Drugs, School of Biomedical Sciences, Huaqiao University, Xiamen 361021, P.
R. China
■ ABSTRACT
Rhꢀcatalyzed orthoꢀCꢀH carbenoid insertion reaction of diarylazines with diazo
compounds has been developed. A wide range of orthoꢀsubstituted diarylazines have
been obtained in moderate to high yields with high regioselectivity at room
temperature. Hydrolysis of the products could release ketones or aldehydes, giving
access to aromatic 1,5ꢀketoꢀdiesters as valuable synthons for further chemical
transformations.
■ INTRODUCTION
Transitionꢀmetalꢀcatalyzed functionalization of CꢀH bonds has seen a
tremendous development over the last decades.1 In particular, great progress has been
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made in siteꢀselective chemical transformations of less active CꢀH bonds.2 Usage of
directing groups is an efficient way to improve reactivity and selective control.3
Nitrogenꢀcontaining functional groups, such as pyridine,4 pyrimidine,5 imines,6
oximes,7 and hydrazone,8 have been widely explored as directing groups because of
their coordination ability with transition metal atoms. Azines (Ar(R)C=NꢀN=C(R)Ar),
which possess valuable intrinsic physical, biological properties9 and are useful
organic synthetic intermediates,10 have recently proved to be a viable directing group
by Huang11 and Zhu (Scheme 1a).12 Nevertheless, formation of diꢀfunctionalized
products of these nitrogenꢀcontaining substructures is difficult to avoid.13 Herein, the
azine function (Ar(R)C=NꢀN=C(R)Ar) is envisaged as a directing group for the
Rhꢀcatalyzed orthoꢀCꢀH carbenoid insertion reaction of diarylazines (Scheme 1b). In
this protocol, the azine acts as a directing group and a bridging unit between two
potentially reacting aromatic rings (Ar). Hereafter two equivalent αꢀketoaryl
malonates could be obtained with diazomalonate in one step with a superior
orthoꢀCꢀH site selectivity. The reaction could proceed smoothly at room temperature
with broad functional group compatibility.
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Scheme 1. Azine directing group-assisted ortho-C-H functionalization
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■ RESULTS AND DISCUSSION
Acetophenazine 1a and dimethyl diazomalonate 2a were firstly selected as
model reactants to optimize the reaction conditions (Table 1). The expected CꢀH
insertion product 3aa was obtained in 89% isolated yield in the presence of
[Cp*RhCl2]2 (2.5 mol %), AgSbF6 (10 mol %) and PhCO2H (25 mol %) in methanol
at 25 oC in 12 hours (entry 1). The structure of 3aa was confirmed by a single crystal
Xꢀray diffraction analysis (see the Supporting Information, Figure S1). No product
was observed in the absence of the Rh(III) catalyst (entry 2). The absence of Ag salt
resulted in a lower yield of 69% (entry 3). Only 26% yield of the desired product was
obtained in the absence of acid (entry 4). Next, the use of alternative solvents, such as
water, 1,4ꢀdioxane or 2,2,2ꢀtrifluoroethanol (TFE), were shown to provide inferior
results (entries 5ꢀ7). Other Ag(I) salts were then investigated. Slightly lower yields
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were obtained with AgNO3 or AgBF4. A yield of 88% was restored with AgOAc
(Table 1, entries 8ꢀ10 vs 1). The cheaper AgOAc salt was chosen as an additive
instead of AgSbF6. No reaction was observed in the presence of strong acids, such as
HCl or trifluoroacetic acid (TFA) (entries 11 and 12), but addition of AcOH led to
81% yield (entry 13). Next, we examined the effect of benzoic acid derivatives and
found that combination of AgOAc and 2,4,6ꢀtrimethylbenzoic acid as additives
increased the yield to 97% (entries 14 and 15).
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Table 1. Screening of various parameters for the reaction of acetophenazine with
dimethyl diazomalonatea
entry
1
2c
Ag(I)
acid
PhCOOH
solvent
MeOH
MeOH
MeOH
MeOH
H2O
yieldb (%)
89
AgSbF6
AgSbF6
none
PhCOOH
no
3
PhCOOH
69
4
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgNO3
AgBF4
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
none
26
5
PhCOOH
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6
PhCOOH
1,4ꢀdioxane
TFE
trace
no
7
PhCOOH
8
PhCOOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
74
9
PhCOOH
81
10
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13
14
15
PhCOOH
88
HCl
no
TFA
no
AcOH
81
pꢀnitrobenzoic acid
2,4,6ꢀ trimethylbenzoic acid
87
97
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a
Reaction conditions: 1a (0.2 mmol), 2a (0.45 mmol), [Cp*RhCl2]2 (2.5 mol %), Ag(I) (10
5
6
7
b
c
mol %), acid (25 mol %), solvent (1.5 mL), 12 h, under air, r.t. Isolated yields. Without
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[Cp*RhCl2]2. TFE: 2,2,2ꢀtrifluoroethanol, TFA: trifluoroacetic acid.
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With optimized conditions in hand, the scope of arylketazine substrates was
investigated with the dimethyl diazomalonate 2a (Scheme 2). Aryl rings substituted
with electronꢀdonating groups were found to favor for carbenoid insertion of
orthoꢀCꢀH bond, providing the diꢀmalonyl products in high yields (3aa-3ga).
paraꢀSubstituted acetophenazine afforded the anticipated products (3aa-3ea) in
substantial yields (74ꢀ93%). The metaꢀmethyl acetophenazine 1f gave the
Cꢀ6ꢀsubstituted product 3fa at the less hindered position in 94% yield. However,
when a methoxy group or fluoro was placed at the meta position in 1g or 1h, the
major products were the hindered Cꢀ2ꢀsubstituted products, isolated with 63% (3ga)
and 68% yields (3ga), respectively, revealing an orthoꢀdirecting effect of the methoxy
group and F atom. The reaction was found less efficient for ketazines substituted by
electronꢀwithdrawing groups (e.g. ꢀCF3, ꢀCN, ꢀNO2) or halogen (Cl, Br, I). The
ketazines with ꢀCF3, ꢀCN, ꢀNO2 did not afford the anticipated products and
paraꢀsubstitution by halogen atoms (Cl, Br) led to the monoꢀsubstituted product in
low yields (< 30 %). When R2 was ethyl, the targeted product (3ia) could be obtained
in 85% yield. The other arylꢀketazine substrates, such as αꢀtetralone azine (3j) and
naphthyl methyl ketazine (3k), could give the corresponding products 3ja and 3ka
o
o
both in 74% yield, albeit at 60 C. Heating to 60 C is also required for aldazines,
conceivably because of their lower coordinating ability as compared to ketazines.
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oꢀMethyl benzaldazine 1l provided the diꢀmalonyl product 3la in 95% yield.
mꢀMethyl benzaldazine 1m led mainly to 3ma, the diꢀmalonylated product at the less
hindered ortho position, in 75% yield (Scheme 2).
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Scheme 2. Scope of the azinesa
CO2Me
MeO2C
OMe
N2
R2
[Cp*RhCl2]2 (2.5 mol %)
AgOAc (10 mol %)
R2
R1
+
R1
O
O
N
N
2
N
N
R1
R1
R2
2,4,6-trimethylbenzoic acid (25 mol %)
MeOH, air, r.t, 12 h
R2
CO2Me
OMe
2a
MeO2C
1
3
CO2Me
CO2Me
MeO2C
MeO2C
R1
R1= H
3aa, 97%
N
N
N
= CH3 3ba, 93%
= OMe 3ca, 92%
= iBu 3da, 74%
3ea,
N
R1
CO2Me
CO2Me
= tBu
75%
MeO2C
MeO2C
3fa, 94%
CO2Me
CO2Me
CO2Me
MeO2C
R1
MeO2C
MeO2C
N
N
R1
CO2Me
N
N
N
N
MeO2C
CO2Me
CO2Me
R1= OMe 3ga, 63%
MeO2C
MeO2C
= F
3ha, 68%
3ja, 74%b
3ia
, 85%
CO2Me
CO2Me
CO2Me
MeO2C
MeO2C
MeO2C
N
N
N
N
N
N
CO2Me
CO2Me
CO2Me
CO2Me
3ma, 75%b
CO2Me
3la, 95%b
MeO2C
3ka, 74%b
a Reaction conditions: 1 (0.2 mmol), 2a (0.45 mmol), [Cp*RhCl2]2 (2.5 mol %), AgOAc (10
mol %), 2,4,6ꢀtrimethylbenzoic acid (25 mol %), MeOH (1.5 mL), 12 h, under air, r.t.; Isolated
yields. b 60 oC.
The scope of the diazo was also examined (Scheme 3). Acetophenazine could
react smoothly with various diazomalonates to afford the corresponding
symmetrically substituted products in 86ꢀ94% yields. Either symmetrical or
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asymmetrical diazomalonates could be used as reactants, giving the symmetrical
products 3ab-3ac and asymmetrical products 3ad in 86ꢀ94% yield. The aldazine 1l-m
were also found to give the anticipated products 3lb (81%), 3mb (60%), 3me (53%).
Scheme 3. Scope of the diazomalonatesa
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a
Reaction conditions: 1 (0.2 mmol), 2 (0.45 mmol), [Cp*RhCl2]2 (2.5 mol %), AgOAc (10
mol %), 2,4,6ꢀtrimethylbenzoic acid (25 mol %), MeOH (1.5 mL), 12 h, under air, r.t.; Isolated
yields. b 60 oC.
Aldehyde and ketone carbonyl groups could be recovered by treatment of the
azine products 3 with concentrated aqueous HCl. This was illustrated for the
oꢀmalonylꢀacetophenazine primary product 3aa, which gave the corresponding
tricarbonyl product 5aa in 75% yield (Scheme 4). αꢀArylmalonates are useful
intermediates in organic synthesis. As a possible synthetic application, intramolecular
Claisen/Dieckmann condensation of 5aa or analogues could lead to functional
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naphthalene derivatives with biological or pharmaceutical properties, such as selective
inhibition of human leukocyte elastase.7b, 14
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Scheme 4. Example of synthetic application of the Rh-catalyzed C-C coupling of
azines with dimethyl diazomalonate to access o-malonyl-acetophenones
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■ CONCLUSION
In conclusion, we developed an efficient procedure for regioselective
Rhꢀcatalyzed orthoꢀCꢀH carbenoid insertion of αꢀdiazomalonates with arylꢀketazine
or ꢀaldazine substrates. A wide range of orthoꢀsubstituted diarylazines were obtained
in moderate to high yields at room temperature. The products could be regarded as
versatile intermediates to build valuable molecular targets.
■ EXPERIMENTAL SECTION
General Methods. All reactions were conducted with a tube under air
atmosphere. Unless otherwise stated, all commercial materials and solvents were used
directly without further purification. H and 13C NMR spectra were measured on a
1
400 MHz Bruker spectrometer (1H 400MHz, 13C 100MHz), using CDCl3 as the
solvent and tetramethylsilane (TMS) as the internal standard at room temperature.
Chemical shifts were reported in ppm referenced to the center of a triplet at 77.0 ppm
of chloroformꢀd. Highꢀresolution mass spectra (HRMS) were recorded using Agilent
6450 spectrometer. Highꢀresolution mass spectra (HRMS) were equipped with an ESI
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source and a TOF detector. Column chromatography was performed on silica gel
(70ꢀ230 mesh ASTM) using the reported eluents. Thinꢀlayer chromatography (TLC)
was carried out on 4×15 cm plates with a layer thickness of 0.2 mm (silica gel 60
F254).
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General procedure for the synthesis of aromatic ketazines 1 according to the
previously reported method:15 Hydrazine hydrate (1.0 g, 16.6 mmol, 80%) was
added to a solution of acetophenone (2.0 g, 16.6 mmol) and AcOH (119.0 mg, 1.7
o
mmol) in EtOH (15 mL), then the mixture was heated to 100 C with stirring and
refluxed for 10 hours. After cooling to room temperature, filtering and washing with
EtOH (40 mL × 4) and dried under vaccum. The corresponding bright yellow
(1E,2E)ꢀ1,2ꢀbis (1ꢀphenylethylidene) hydrazine (1a) was obtained in 90% yield.
General procedure for the synthesis of diazo compounds 2 according to the
previously reported method:16 To a solution of dimethyl malonate (10 mmol) and
pꢀacetamidobenzenesulfonyl azide (pꢀABSA) (12 mmol) in anhydrous CH3CN (20
o
mL) at 0 C, 1,8ꢀDiazabicyclo[5.4.0]undecꢀ7ꢀene (DBU) (14 mmol) was added
dropwise for 30min. After stirring at room temperature overnight, the reaction mixture
was concentrated under vacuum. Water (20 mL) was added. The resulting mixture
was extracted with dichloromethane (2 × 20 mL). The combined organic layer was
washed with brine (20 mL) and dried over MgSO4. The solvent was removed under
reduced pressure, and the residue was purified by a silica gel column chromatography
with petroleum ether/ethyl acetate as the eluent to give the entitled diazo compounds.
Preparation of Products 3. Under air atmosphere, a reaction tube (5 mL)
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equipped with a magnetic stirrer bar was charged with arylazine 1 (0.2 mmol),
diazomalonate 2 (0.45 mmol), [Cp*RhCl2]2 (2.5 mol %), AgOAc (0.02 mmol, 10
mol %), 2,4,6ꢀtrimethylbenzoic acid (0.05 mmol, 25 mol %) and MeOH (1.5 mL).
The reaction mixture was stirred at room temperature for 12 h. The solvents were
removed under reduced pressure, and the residue was purified by chromatography on
silica gel (eluent: petroleum ether/ethyl acetate = 4:1) to give the desired product.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(2,1-phenylene))dimalonate (3aa). Eluent: petroleum ether/ethyl acetate (4:1).
White solid, 97% yield (96 mg), mp: 181ꢀ183 oC. 1H NMR (400 MHz, CDCl3) δ 7.53
– 7.41 (m, 8H), 5.54 (s, 2H), 3.76 (s, 12H), 2.25 (s, 6H). 13C NMR (100 MHz, CDCl3)
δ 169.3, 161.2 , 138.8 , 130.7, 129.8, 129.1, 128.4, 128.1, 54.6, 52.7, 18.3. HRMS
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+
(ESI) m/z calcd. for C26H29N2O8 (M+H+), 497.1918, found: 497.1926.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(3-methyl-6,1-phenylene))dimalonate (3ba). Eluent: petroleum ether/ethyl
o
acetate (4:1). Yellow solid, 94% yield (99 mg), mp: 180ꢀ181 C. 1H NMR (400 MHz,
CDCl3) δ 7.37 (d, J = 7.6 Hz, 2H), 7.29 (s, 2H), 7.22 (d, J = 8.0 Hz, 2H), 5.58 (s, 2H),
3.76 (s, 12H), 2.40 (s, 6H), 2.23 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 169.4, 161.0,
139.2, 136.0, 130.6, 130.3, 128.9, 128.4, 54.6, 52.7, 21.4, 18.2. HRMS (ESI) m/z
+
calcd. for C28H33N2O8 (M+H+), 525.2231, found: 525.2235.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(3-methoxy-6,1-phenylene))dimalonate (3ca). Eluent: petroleum ether/ethyl
acetate (4:1). White solid, 92% yield (102 mg), mp: 177ꢀ178 oC. 1H NMR (400 MHz,
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CDCl3) δ 7.44 (d, J = 8.4 Hz, 2H), 7.04 (d, J = 2.4 Hz, 2H), 6.93 (dd, J = 8.6, 2.5 Hz,
2H), 5.68 (s, 2H), 3.84 (s, 6H), 3.76 (s, 12H), 2.23 (s, 6H). 13C NMR (100 MHz,
CDCl3) δ 169.2, 160.8, 159.8, 132.5, 131.5, 130.0, 115.6, 113.3, 55.4, 54.7, 52.6, 18.1.
HRMS (ESI) m/z calcd. for C28H33N2O10+ (M+H+), 557.2130, found: 557.2136.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(3-isobutyl-6,1-phenylene))dimalonate (3da). Eluent: petroleum ether/ethyl
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o
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acetate (4:1). White solid, 74% yield (90 mg), mp: 140ꢀ141 C. H NMR (400 MHz,
CDCl3) δ 7.40 (d, J = 7.6 Hz, 2H), 7.25 (d, J = 1.2 Hz, 2H), 7.19 (dd, J = 8.0, 1.3 Hz,
2H), 5.59 (s, 2H), 3.75 (s, 12H), 2.52 (d, J = 6.8 Hz, 4H), 2.25 (s, 6H), 1.87 (m, 2H),
0.92 (d, J = 6.8 Hz, 12H). 13C NMR (100 MHz, CDCl3) δ 169.4, 161.1, 142.7, 136.2,
130.7, 130.4, 128.8, 128.2, 54.6, 52.6, 45.0, 30.1, 22.2, 18.2. HRMS (ESI) m/z calcd.
+
for C34H45N2O8 (M+H+), 609.3170, found: 609.3178.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(3-(tert-butyl)-6,1-phenylene))dimalonate (3ea). Eluent: petroleum ether/ethyl
o
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acetate (4:1). White solid, 75% yield (91 mg), mp: 148ꢀ150 C. H NMR (400 MHz,
CDCl3) δ 7.51 (s, 2H), 7.42 (s, 4H), 5.61 (s, 2H), 3.76 (s, 12H), 2.24 (s, 6H), 1.34 (s,
18H). 13C NMR (100 MHz, CDCl3) δ 169.4, 161.0, 152.1, 136.0, 130.4, 128.2, 127.0,
+
125.0, 54.8, 52.6, 34.7, 31.1, 18.2. HRMS (ESI) m/z calcd. for C34H45N2O8 (M+H+),
609.3170, found: 609.3179.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(4-methyl-2,1-phenylene))dimalonate (3fa). Eluent: petroleum ether/ethyl acetate
(4:1). Yellow solid, 94% yield (99 mg), mp: 189ꢀ191 oC. 1H NMR (400 MHz, CDCl3)
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δ 7.40 (d, J = 7.6 Hz, 2H), 7.26 (s, 2H), 7.23 (d, J = 8.0 Hz, 2H), 5.47 (s, 2H), 3.75 (s,
12H), 2.39 (s, 6H), 2.24 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 169.3, 161.2, 138.8,
137.9, 129.8, 129.6, 129.0, 127.7, 54.3, 52.6, 21.1, 18.3. HRMS (ESI) m/z calcd.
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forC28H33N2O8 (M+H+), 525.2231, found: 525.2238.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(6-methoxy-2,1-phenylene))dimalonate (3ga). Eluent: petroleum ether/ethyl
acetate (4:1). Yellow solid, 63% yield (70 mg), mp: 173ꢀ175 C. 1H NMR (400 MHz,
o
CDCl3) δ 7.38 (t, J = 8.0 Hz, 2H), 7.11 – 7.05 (m, 2H), 7.01 (d, J = 8.4 Hz, 2H), 5.32
(s, 2H), 3.84 (s, 6H), 3.73 (s, 12H), 2.21 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 169.1,
161.8, 158.4, 140.3, 128.9, 121.4, 120.7, 112.6, 56.3, 52.3, 51.5, 18.3. HRMS (ESI)
m/z calcd. for C28H33N2O10+ (M+H+), 557.2130, found: 557.2138.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(6-fluoro-2,1-phenylene))dimalonate (3ha). Eluent: petroleum ether/ethyl acetate
(4:1). Yellow solid, 68% yield (72 mg), mp: 126ꢀ128 oC. 1H NMR (400 MHz, CDCl3)
δ 7.41 (m, 2H), 7.27 (d, J = 7.2 Hz, 2H), 7.20 – 7.14 (m, 2H), 5.43 (s, 2H), 3.77 (s,
12H), 2.24 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 168.3, 161.9 (d, J = 248.9 Hz),
161.1 (d, J = 2.5 Hz), 140.6 (d, J = 3.7 Hz), 129.5 (d, J = 9.5 Hz), 124.0 (d, J = 2.9
Hz), 120.2 (d, J = 15.1 Hz), 116.6 (d, J = 23.2 Hz), 52.7, 51.1, 18.2.19F NMR (376
MHz, CDCl3) δ ꢀ110.4. HRMS (ESI) m/z calcd. for C26H27F2N2O8 (M+H+), 533.1730,
+
found: 533.1734.
Tetramethyl
2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(propan-1-yl-1-
ylidene))bis(2,1-phenylene))dimalonate (3ia). Eluent: petroleum ether/ethyl acetate
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(4:1). Yellow solid, 85% yield (89 mg), mp: 153ꢀ154 oC. 1H NMR (400 MHz, CDCl3)
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δ 7.57 (d, J = 7.2 Hz, 2H), 7.46 – 7.39 (m, 6H), 5.43 (s, 2H), 3.75 (s, 12H), 2.74 (d, J
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9
13
= 7.6 Hz, 4H), 0.99 (t, J = 7.5 Hz, 6H). C NMR (100 MHz, CDCl3) δ 169.1, 165.7,
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138.0, 131.2, 129.9, 128.8, 127.9, 127.9, 54.2, 52.6, 24.9, 10.6. HRMS (ESI) m/z
calcd. for C28H33N2O8 (M+H+), 525.2231, found: 525.2238.
+
Tetramethyl
2,2'-((8E,8'E)-hydrazine-1,2-diylidene
bis(5,6,7,8-
tetrahydronaphthalene-1-yl-8-ylidene))dimalonate (3ja). Eluent: petroleum
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ether/ethyl acetate (4:1). Yellow solid, 74% yield (81 mg), mp: 200ꢀ202 C. H NMR
(400 MHz, CDCl3) δ 7.29 (m, 4H), 7.19 (d, J = 7.2 Hz, 2H), 6.01 (s, 2H), 3.75 (s,
12H), 2.79 – 2.74 (m, 4H), 2.58 (t, J = 6.6 Hz, 4H), 1.86 – 1.78 (m, 4H). 13C NMR
(101 MHz, CDCl3) δ 169.7, 156.9, 142.6, 131.9, 131.4, 128.9, 128.5, 128.3, 56.1,
+
52.5, 31.1, 28.8, 21.4. HRMS (ESI) m/z calcd. for C30H33N2O8 (M+H+), 549.2231,
found: 549.2238.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(naphthalene-3,2-diyl))dimalonate (3ka). Eluent: petroleum ether/ethyl acetate
(4:1). Yellow solid, 74% yield (88 mg), mp: 229ꢀ230 oC. 1H NMR (400 MHz, CDCl3)
δ 7.99 (s, 2H), 7.95 (s, 2H), 7.90 – 7.85 (m, 4H), 7.56 – 7.52 (m, 4H), 5.77 (s, 2H),
3.81 (s, 12H), 2.37 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 169.5, 160.5, 136.2, 133.0,
132.3, 129.4, 128.7, 128.5, 128.0, 127.8, 127.2, 127.0, 55.1, 52.8, 18.2. HRMS (ESI)
+
m/z calcd. for C34H33N2O8 (M+H+), 597.2231, found: 597.2236.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(methanylylidene))bis
(3-methyl-2,1-phenylene))dimalonate (3la). Eluent: petroleum ether/ethyl acetate
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(4:1). Yellow solid, 95% yield (94 mg), mp: 230ꢀ232 oC. 1H NMR (400 MHz, CDCl3)
δ 8.97 (s, 2H), 7.36 (t, J = 7.6 Hz, 2H), 7.25 (d, J = 6.8 Hz, 4H), 5.71 (s, 2H), 3.78 (s,
12H), 2.50 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 169.3, 161.7, 139.5, 132.6, 130.9,
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+
130.7, 130.5, 127.7, 56.1, 52.7, 20.3. HRMS (ESI) m/z calcd. for C26H29N2O8
(M+H+), 497.1918, found: 497.1926.
Tetramethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(methanylylidene))bis
(4-methyl-2,1-phenylene))dimalonate (3ma). Eluent: petroleum ether/ethyl acetate
(4:1). Yellow solid, 75% yield (74 mg), mp: 175ꢀ177 oC. 1H NMR (400 MHz, CDCl3)
δ 8.73 (s, 2H), 7.56 (s, 2H), 7.34 (d, J = 8.0 Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H), 5.80 (s,
2H), 3.78 (s, 12H), 2.40 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 169.0, 162.7, 138.3,
132.3, 131.9, 131.8, 129.9, 129.8, 54.6, 52.8, 20.9. HRMS (ESI) m/z calcd. for
+
C26H29N2O8 (M+H+), 497.1918, found: 497.1925.
Tetraethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(2,1-phenylene))dimalonate (3ab). Eluent: petroleum ether/ethyl acetate (4:1).
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Yellow solid, 94% yield (104 mg), mp: 100ꢀ101 C H NMR (400 MHz, CDCl3) δ
7.55 (dd, J = 6.9, 1.8 Hz, 2H), 7.48 – 7.37 (m, 6H), 5.48 (s, 2H), 4.29 – 4.17 (m, 8H),
2.26 (s, 6H), 1.26 (t, J = 7.1 Hz, 12H). 13C NMR (100 MHz, CDCl3) δ 168.7, 160.9,
139.0, 130.9, 129.8, 128.9, 128.2, 127.9, 61.5, 54.8, 18.5, 14.0. HRMS (ESI) m/z
+
calcd. for C30H37N2O8 (M+H+), 553.2544, found: 553.2553.
Tetrabenzyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))
bis(2,1-phenylene))dimalonate (3ac). Eluent: petroleum ether/ethyl acetate (4:1).
Yellow oil, 87% yield (139 mg). 1H NMR (400 MHz, CDCl3) δ 7.47 (dd, J = 5.2, 2.4
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Hz, 2H), 7.34 (d, J = 2.0 Hz, 6H), 7.23 (s, 20H), 5.65 (s, 2H), 5.14 (d, J = 2.4 Hz, 8H),
2.07 (s, 6H). 13C NMR (100 MHz, CDCl3) δ 168.4, 160.9, 138.8, 135.3, 129.9, 128.9,
128.5, 128.4, 128.3, 128.2, 128.1, 128.0, 127.9, 127.8, 67.2, 54.8, 18.4. HRMS (ESI)
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+
m/z calcd. for C50H45N2O8 (M+H+), 801.3170, found: 801.3175.
1-Benzyl-3-methyl-2-(2-((E)-1-(((E)-1-(2-(1-(benzyloxy)-3-methoxy-1,3-dioxo
propan-2-yl)phenyl)ethylidene)hydrazono)ethyl)phenyl)malonate (3ad). Eluent:
1
petroleum ether/ethyl acetate (4:1). Yellow oil, 86% yield (111 mg). H NMR (400
MHz, CDCl3) δ 7.48 (d, J = 2.8 Hz, 2H), 7.43 – 7.36 (m, 6H), 7.28 (s, 10H), 5.59 (d, J
= 2.0 Hz, 2H), 5.19 (d, J = 5.2 Hz, 4H), 3.70 (d, J = 5.2 Hz, 6H), 2.16 (s, 6H). 13C
NMR (100 MHz, CDCl3) δ 169.1, 168.5, 161.0, 138.8, 135.4, 130.6, 129.9, 129.0,
128.4, 128.3, 128.2, 128.0, 128.0, 67.2, 54.7, 52.6, 18.4. HRMS (ESI) m/z calcd. for
C38H37N2O8 (M+H+), 649.2544, found: 649.2549.
+
Tetraethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(methanylylidene))bis
(3-methyl-2,1-phenylene))dimalonate (3lb). Eluent: petroleum ether/ethyl acetate
(4:1). White solid, 81% yield (89 mg), mp: 108ꢀ110 C. 1H NMR (400 MHz, CDCl3)
o
δ 8.98 (s, 2H), 7.36 (t, J = 7.6 Hz, 2H), 7.29 (d, J = 7.6 Hz, 2H), 7.24 (d, J = 7.6 Hz,
2H), 5.68 (s, 2H), 4.25 (m, 8H), 2.49 (s, 6H), 1.28 (t, J = 7.1 Hz, 12H). 13C NMR (100
MHz, CDCl3) δ 168.9, 161.7, 139.4, 132.9, 131.0, 130.6, 130.3, 127.7, 61.6, 56.2,
20.4, 14.1. HRMS (ESI) m/z calcd. for C30H37N2O8 (M+H+), 553.2544, found:
+
553.2538.
Tetraethyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(methanylylidene))bis
(4-methyl-2,1-phenylene))dimalonate (3mb). Eluent: petroleum ether/ethyl acetate
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(4:1). White solid, 60% yield (66 mg), mp: 145ꢀ146 C. 1H NMR (400 MHz, CDCl3)
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δ 8.77 (s, 2H), 7.58 (s, 2H), 7.37 (d, J = 8.0 Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H), 5.72 (s,
2H), 4.27 – 4.23 (m, 6H), 2.40 (s, 6H), 1.27 (t, J = 7.1 Hz, 12H). 13C NMR (100 MHz,
CDCl3) δ 168.6, 162.5, 138.1, 132.0, 131.7, 130.1, 129.9, 128.6, 61.7, 54.8, 20.9, 14.0.
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HRMS (ESI) m/z calcd. for C30H37N2O8 (M+H+), 553.2544, found: 553.2540.
+
Tetraisopropyl 2,2'-(((1E,1'E)-hydrazine-1,2-diylidenebis(methanylylidene))
bis(4-methyl-2,1-phenylene))dimalonate (3me). Eluent: petroleum ether/ethyl
acetate (4:1). Yellow solid, 53% yield (64 mg), mp: 143ꢀ145 oC. 1H NMR (400 MHz,
CDCl3) δ 8.78 (s, 2H), 7.59 (s, 2H), 7.38 (d, J = 8.0 Hz, 2H), 7.27 (d, J = 9.2 Hz, 2H),
5.62 (s, 2H), 5.10 (m, 4H), 2.40 (s, 6H), 1.28 (d, J = 6.0 Hz, 12H), 1.25 (d, J = 6.4 Hz,
12H). 13C NMR (100 MHz, CDCl3) δ 168.1, 162.3, 137.9, 132.0, 131.6, 130.4, 129.9,
+
128.6, 69.2, 55.0, 21.59, 21.58, 20.9. HRMS (ESI) m/z calcd. for C34H45N2O8
(M+H+), 609.3170, found: 609.3171.
■ ASSOCIATED CONTENT
Supporting Information. Description of the Xꢀray structures and NMR spectra of the
compounds. This material is available free of charge via the Internet at
http://pubs.acs.org.
■ AUTHOR INFORMATION
Corresponding Author
Xiuling Cui* Eꢀmail: cuixl@hqu.edu.cn.
Fax: (+)86ꢀ592ꢀ6162996.
Remi Chauvin* Eꢀmail: remi.chauvin@lccꢀtoulouse.fr
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Present Addresses
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†(a) CNRS, LCC (Laboratoire de Chimie de Coordination),205, route de Narbonne,
BP 44099, Fꢀ31077 Toulouse Cedex 4 France. (b) Université de Toulouse, UPS, INPT,
Fꢀ31077 Toulouse, Cedex 4, France.
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Notes
The authors declare no competing financial interest.
■ ACKNOWLEDGMENT
This research was supported by NSF of China (21572072), Xiamen Southern
Oceanographic Center (15PYY052SF01), Science and Technology Bureau of Xiamen
City (3502Z20150054), and Huaqiao University.
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