Rhodium(II) Acetate-Catalyzed Reaction of 2-Amino-4,5-dihydro-3-furancarbonitriles with Dialkyl Diazomalonates

Article abstract of DOI:10.1002/(sici)1521-3897(199908)341:6<562::aid-prac562>3.0.co;2-4

2-Amino-4,5-dihydro-3-furancarbonitriles 3 react with dialkyl diazomalonates in the presence of rhodium(II) acetate to yield dialkyl (5-amino-4-cyano-2,3-dihydro-3-furanyl)propanedioates 4. Dehydrogenation of 4 with DDQ provided dialkyl (5-amino-4-cyano-3

Full text of DOI:10.1002/(sici)1521-3897(199908)341:6<562::aid-prac562>3.0.co;2-4

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Rhodium(II) Acetate-Catalyzed Reaction of
2-Amino-4,5-dihydro-3-furancarbonitriles with Dialkyl Diazomalonates
Kenji Yamagata, Fumi Okabe, and Motoyoshi Yamazaki*
Fukuoka/Japan, Faculty of Pharmaceutical Sciences, Fukuoka University
Received June 23th, 1999
Keywords: Diazo compounds, Rhodium, Insertions, Dialkyl propanedioates, Furancarbonitriles
Abstract. 2-Amino-4,5-dihydro-3-furancarbonitriles 3 re-
act with dialkyl diazomalonates in the presence of rho-
dium(II) acetate to yield dialkyl (5-amino-4-cyano-2,3-di-
hydro-3-furanyl)propanedioates 4. Dehydrogenation of 4 with
DDQ provided dialkyl (5-amino-4-cyano-3-furanyl)pro-
panedioates 5.
In the preceding paper, we showed that 2-amino-4,5-
dihydro-3-furancarbonitriles react with α-diazo-β-keto
esters such as ethyl diazoacetoacetate and ethyl diazo-
benzoylacetate in the presence of rhodium(II) acetate
to form ethyl 2H-pyran-2-carboxylate [1]. In continua-
tion of this study, we examined the reactions of 2-ami-
no-4,5-dihydro-3-furancarbonitriles (1 and 3) with dime-
thyl diazomalonate [2] and diethyl diazomalonate [3].
When a mixture of 2-amino-4,5-dihydro-3-furancar-
bonitrile 1 [4], dimethyl diazomalonate, and a catalytic
amount of rhodium(II) acetate in 1,2-dichloroethane was
refluxed for 1 h, an N–H insertion product, dimethyl
[(3-cyano-4,5-dihydro-2-furanyl)amino]propanedioate
(2) was obtained in 75% yield, and the expected dime-
thyl 2H-pyran-2,2-dicarboxylate could not be isolated.
In order to confirm the structure of 2, hydrolysis of 2
with hydrochloric acid led to tetrahydro-2-oxo-3-fur-
ancarbonitrile which was identical with an authentic
Subsequently, to prevent the N–H insertion reaction,
we investigated the reaction of 4,5-dihydro-2-pyrrolid-
ino-, as well as of 2-piperidino- and 2-morpholino-3-
furancarbonitriles 3a–h [6, 7] with dialkyl diazoma-
lonates, and found an unexpected reaction.
When a mixture of 2-pyrrolidino-3-furancarbonitrile
3a, dimethyl diazomalonate, and rhodium(II) acetate in
fluorobenzene was heated at 70 °C under nitrogen, an
R2OOC
NN=C=(CC(COOOORR)2)2 R2OOC
CN
N
CN
N
CH
R1
2
2
2
2
R
R
R
R
R1
O
O
Rh2(OAc)4
4a-k
3a-h
DDQ
1
sample [5]. The H NMR spectrum of 2 in deuterio-
R2OOC
R2OOC
R2OOC
R2OOC
chloroform indicates that 2 consists of approximately a
3:2 tautomeric mixture of the enamine A and the imine
B forms (Scheme 1).
CN
C
CN
N
CH
R1
R
R
O
R1
O
N
R
R
D
5a-k, C
CN
CN
N2=C(COOMe)2
Rh2(OAc)4
NH2
O
NHCH(COOMe)2
O
R
R
R
2, A
1
4,5 R1
R1 R2
N
R2
N
R
3-5
Ph
Et
Et
Et
N
N
N
N
N
N
N
N
N
a
i
H
Me
Ph
Ph
j
N
H
Me
Me
Me
b
c
d
e
f
O
O
N
O
k
H
Me
Me
Me
Me
Ph
CN
O
CN
conc. HCl
Ph Me
Me
g
O
N-CH(COOMe)2
O
MeO
MeOH
O
Ph
h
H
B
Scheme 1
Scheme 2
562 © WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999 1436-9966/99/3410X-562 $ 17.50 + .50/0
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Rhodium(II) Acetate-Catalyzed Reaction of 2-Amino-4,5-dihydro-3-furancarbonitriles
___________________________________________________________________________ FULL PAPER
allylic C–H insertion product, dimethyl (4-cyano-2,3-
dihydro-5-pyrrolidino-furan-3-yl)propanedioate 4a was
obtained in 41% yield (Scheme 2).
the other hand, in the IR spectra of 5e–k, the two bands
of the non-conjugated ester carbonyl groups (1 725–
1 735 and 1 740– 1 760 cm–1) shift to higher frequen-
cies from 20 to 30 cm–1 than those of 5a –d. The
1H NMR spectra of 5e– k reveal the signal of the
malonate methine proton as a singlet at δ = 4.48–
4.83 ppm, and no the signal of a methine proton (2-H)
of the furan ring observed around δ = 5.50–6.50 ppm.
These spectral data suggest that 5a–d are the 3(2H)-
furanylidene structure C, whereas those of 5e–k are
the furan-3-yl structure D.
Compound 4a has the molecular composition
C14H18N2O5, and its IR, 1H NMR, and 13C NMR spec-
tra are consistent with the proposed structure 4a. The
analogous allylic C–H insertion was also observed by
Wulfman et al. in their study dealing with the reactions
of cyclohexenes and dimethoxycarbonylcarbenoid [8].
Compounds 3b–h reacted with dimethyl diazomalonate
under the same conditions to give the corresponding
dimethyl furan-3-ylpropanedioates 4b–h in fair yields.
Similarly, the reaction of 3f–h with diethyl diazoma-
lonate afforded the corresponding diethyl 3-furanylpro-
panedioates 4i–k. Also their structures were supported
by analytical and spectral data.
In order to confirm the structure of 4a, dehydrogena-
tion of 4a with DDQ led to dimethyl 3-furanylpropane-
dioate 5a, which was identical with an authentic sam-
ple prepared by the following method: Chloroacetyla-
tion of 1-(cyanoacetyl)pyrrolidine [9] with chloroacetyl
chloride in the presence of magnesium chloride and tri-
ethylamine gave 4-chloro-3-oxo-2-(pyrrolidinocarbon-
yl)butanenitrile 6 in 54% yield, and subsequent treat-
ment with sodium hydride provided 4,5-dihydro-4-oxo-
2-pyrrolidino-3-furancarbonitrile (7) in 66% yield. Fi-
nally, the desired 5a was prepared by the reaction of 7
with dimethyl malonate in the presence of titanium(IV)
chloride/triethylamine utilising a modification of a pro-
cedure described in the literature [10] (Scheme 3).
Experimental
All melting points are uncorrected. IR spectra were recorded
with a Jasco A-302 instrument. 1H and 13C NMR spectra were
measured on a Hitachi R22 (90 MHz), Jeol JNM-GX-400
(400 MHz), and Jeol JNM-A500 (500 MHz) in CDCl3, with
TMS as internal standard, δ scale; coupling constants in Hz.
Mass spectra were recorded with a Jeol JMS-D300, 70eV.
Dimethyl (3-Cyano-4,5-dihydro-2-furanyl)aminopropane-
dioate 2
A mixture of 1 [4] (1.10 g, 10 mmol), dimethyl diazoma-
lonate [2] (1.74 g, 11 mmol), and Rh2(OAc)4 (0.05 g) in 1,2-
dichloroethane (20 ml) was refluxed for 1 h. The solvent was
removed in vacuo, and the residue was chromatographed on
silica gel with CH2Cl2/acetone (4:1) as eluent, to afford 2.
Colorless prisms; m.p. 88–90 °C (CH2Cl2/petroleum ether).
– IR (KBr): ν/cm–1 = 2190 (C≡N), 1750 (C=O). – 1H NMR
(500 MHz): δ/ppm = 2.50–2.70 (m, 0.8H, 4-H), 2.91 (t,
J =10, 1.2H, 4-H), 3.78 (s, 1.3H, CH3), 3.81 (s, 1.3H, CH3),
3.84 (s, 3.4H, CH3), 3.92 (t, J = 7.5, 0.4H, 3-H), 4.35–4.52
(m, 0. 8H, 5-H), 4.44 (t, J = 10, 1.2H, 5-H), 5.02 (d, J = 8.5,
0.6H, NHCH), 5.04 (s, 0.4H, =N–CH), 5.54 (d, J = 8.5, 0.6H,
NHCH).
ClCH2COCl
MgCl2/Et3N
CN
CO
CN
CO
CH2
ClCH2COCH
N
N
6
C10H12N2O5 Calcd.: C 50.00 H 5.04 N 11.66
(240.2)
Found: C 50.26 H 5.01 N 11.80.
NaH
Reactions of 2-Amino-4,5-dihydro-3-furancarbonitriles
3 with Dialkyl Diazomalonates (General Procedure)
DME
Procedure A: A mixture of 3 (10 mmol), dimethyl diazoma-
lonate (1.74 g, 11 mmol), and Rh2(OAc)4 (0.05 g) in C6H5F
(20 ml) was heated at 70 °C with stirring for 4 h under nitro-
gen. After removal of the solvent in vacuo, the residue was
purified by column chromatography on alumina with CH2Cl2
as eluent. Yield 4a (1.20 g, 41%), 4b (1.08 g, 35%), 4c
(1.30 g, 42%), 4d (1.19 g, 39%), 4e (1.16 g, 36%), 4f (1.51 g,
41%),4g (1.42 g, 37%), and 4h (1.17 g, 30%).
O
O
CN
N
CH2(COOMe)2
TiCl4/Et3N
4a
O
7
Scheme 3
Procedure B: From 3 (10 mmol) and diethyl diazomalonate
[3] (2.79 g, 15 mmol) as described for Procedure A. Yield 4i
(0.93 g, 23%), 4j (0.90 g, 22%), and 4k (1.19 g, 29%).
Subsequently, aromatization of 4b–k with DDQ
yielded the corresponding dialkyl (furan-3-yl)propane-
dioates 5b–k. The IR spectra of 5a–d display the two
bands of the conjugated ester carbonyl groups at 1 680–
1 690 and 1 720–1 730 cm–1. The 1H NMR spectra of
5a–d show a singlet at δ = 5.50–5.20 ppm (5a–c) or a
quartet at δ = 6.05 ppm (5d) corresponding to the two
protons or one proton of the 2-H of the furan ring. On
Dimethyl (4-Cyano-2,3-dihydro-5-pyrrolidino-furan-3-
yl)propanedioate 4a
From 4,5-dihydro-2-pyrrolidino-3-furancarbonitrile [6]
(1.64 g, 10 mmol). Colorless prisms; m.p. 125–126 °C (di-
ethyl ether). – 13C NMR (125 MHz): 25.2, 42.9, 47.7, 49.9,
J. Prakt. Chem. 1999, 341, No. 6
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K. Yamagata et al.
FULL PAPER __________________________________________________________________________
52.5, 52.7, 55.4, 73.6, 120.0, 165.0,168.0, 168.3. – MS (FAB)
ether/petroleum ether). – 13C NMR (100 MHz ): 13.9, 14.0,
25.3, 47.8, 49.5, 50.8, 55.6, 61.5, 61.7, 85.3, 120.3, 125.5,
128.4, 128.6, 140.1, 164.4, 167.6, 167.8.
m/z (%): 295 (54) [M+ + H].
Dimethyl (4-Cyano-2,3-dihydro-5-piperidino-furan-3-yl)pro-
panedioate 4b
Diethyl (4-Cyano-2,3-dihydro-2-phenyl-5-piperidino-furan-
3-yl)propanedioate 4j
From 4,5-dihydro-2-piperidino-3-furancarbonitrile [7]
(1.78 g, 10 mmol). Colorless prisms; m.p. 99–100 °C (di-
ethyl ether). – 13C NMR (100 MHz): 24.0, 25.4, 43.1, 47.3,
50.5, 52.5, 52.7, 55.0, 72.5, 120.1, 166.0, 168.0, 168.2. – MS
(FAB) m/z (%): 309 (53) [M+ + H].
From 4,5-dihydro-5-phenyl-2-piperidino-3-furancarbonitrile
[7] (2.54 g, 10 mmol). Colorless prisms; m.p. 77–78 °C (di-
ethyl ether/petroleum ether). – 13C NMR (100 MHz): 13.9,
14.0, 24.0, 25.6, 47.4, 50.1, 51.0, 55.3, 61.5, 61.7, 84.2, 120.0,
125.4, 128.4, 128.6, 140.1, 165.3, 167.6, 167.8.
Dimethyl (4-Cyano-2,3-dihydro-5-morpholino-furan-3-
yl)propanedioate 4c
Diethyl (4-Cyano-2,3-dihydro-5-morpholino-2-phenyl-furan-
3-yl)propanedioate 4k
From 4,5-dihydro-2-morpholino-3-furancarbonitrile [6]
(1.80 g, 10 mmol). Colorless prisms; m.p. 110–111 °C (di-
ethyl ether). – 13C NMR (100 MHz): 42.9, 46.1, 52.1,52.6,
54.9, 66.1, 72.9, 119.3, 166.0, 167.9, 168.1. – MS(EI) m/z
(%): 310(7)[M+].
From 4,5-dihydro-2-morpholino-5-phenyl-3-furancarbonitrile
[6] (2.56 g, 10 mmol). Colorless prisms; m.p. 92–93 °C (di-
ethyl ether/petroleum ether). – 13C NMR (100 MHz): 13.9,
14.0, 46.2, 50.8, 51.8, 55.1, 61.6, 61.8, 66.1, 84.7, 119.2, 125.5,
128.6, 139.7, 165.3, 167.4, 167.6.
Dimethyl (4-Cyano-2,3-dihydro-2-methyl-5-pyrrolidino-
furan-3-yl)propanedioate 4d
Reactions of 4 with DDQ (General Procedure)
From 4,5-dihydro-5-methyl-2-pyrrolidino-3-furancarbonitrile
[6] (1.78 g, 10 mmol). Colorless columns; m.p. 99 –
100 °C (diethyl ether). – 13C NMR (100 MHz): 21.2, 25.2,
47.6, 48.8, 49.6, 52.4, 52.6, 55.6, 82.3, 120.8, 164.0, 168.0,
168.3.
Procedure A: A mixture of 4a–d, f–k (3 mmol) and DDQ
(0. 89 g, 3.9 mmol) in benzene (20 ml) was refluxed for 1 h.
After the solvent had been removed under reduced pressure,
CH2Cl2 (20 ml) was added to the residue. The mixture was
filtered to remove the insoluble material, and the filtrate was
concentrated in vacuo. The residue was purified by column
chromatography on alumina with CH2Cl2 as eluent. Yield 5a
(0.52 g, 59%), 5b (0.52 g, 57%), 5c (0.34 g, 37%), 5d (0.20 g,
22%), 5f (0.54 g, 49%), 5g (0.55 g, 48%), 5h (0.54 g, 47%),
5i (0.62 g, 52%), 5j (0.56 g, 46%), and 5k (0.69 g, 56%).
Dimethyl (4-Cyano-2,3-dihydro-2-methyl-5-morpholino-
furan-3-yl)propanedioate 4e
From 4,5-dihydro-5-methyl-2-morpholino-3-furancarbonitrile
[6] (1.94 g, 10 mmol). Colorless prisms; m.p. 117–118 °C
(diethyl ether). – 13C NMR (100 MHz): 21.0, 46. 1, 49.5,
51.1, 52.5, 52.7, 55.1, 66.1, 81.6, 119.6, 165.0, 167.8, 168.1.
– MS(EI) m/z (%): 324 (30) [M+].
Procedure B: From 4e (0.97 g, 3 mmol) and DDQ (0.82 g,
3.6 mmol) as described for Procedure A. Yield 5e (0. 17 g,
18%).
Dimethyl (4-Cyano-2,3-dihydro-2-phenyl-5-pyrrolidino-
furan-3-yl)propanedioate 4f
Dimethyl (4-Cyano-5-pyrrolidino-(2H)-furan-3-ylidene)pro-
From 4,5-dihydro-5-phenyl-2-pyrrolidino-3-furancarbonitrile
[6] (2.40 g, 10 mmol). Colorless prisms; m.p. 178–179 °C
(acetone). – 13C NMR (100 MHz): 25.2, 47.8, 49.4, 50.9, 52.5,
52.6, 55.5, 85.5, 120.2, 125.5, 128.5, 128.6, 139.9, 164.4,
167.8, 168.2.
panedioate 5a
From 4a (0. 88 g, 3 mmol). Colorless prisms; m.p. 181–
182 °C (CH2Cl2/petroleum ether). – MS (FAB) m/z (%): 293
(54) [M+ + H].
Dimethyl (4-Cyano-5-piperidino-(2H)-furan-3-ylidene)pro-
panedioate 5b
Dimethyl (4-Cyano-2,3-dihydro-2-phenyl-5-piperidino-
furan-3-yl)propanedioate 4g
From 4b (0.92 g, 3 mmol). Colorless needles; m.p. 151–
152 °C (CH2Cl2/petroleum ether). – MS (FAB) m/z (%): 307
(55) [M+ + H].
From 4,5-dihydro-5-phenyl-2-piperidino-3-furancarbonitrile
[7] (2.54 g, 10 mmol). Colorless prisms; m.p. 101–102 °C
(diethyl ether). – 13C NMR (100 MHz): 24.0, 25.6, 47.5, 49.9,
51.1, 52.5, 52.6, 55.2, 84.3, 119.9, 125.3, 128.5, 128.6, 140.0,
165.3, 167.8, 168.1.
Dimethyl (4-Cyano-5-morpholino-(2H)-furan-3-ylidene)pro-
panedioate 5c
From 4c (0.93 g, 3 mmol). Colorless prisms; m.p. 172–
173 °C (CH2Cl2/petroleum ether). – MS (FAB) m/z (%): 309
(67)[M+ + H].
Dimethyl (4-Cyano-2,3-dihydro-5-morpholino-2-phenyl-
furan-3-yl)propanedioate 4h
From 4,5-dihydro-2-morpholino-5-phenyl-3-furancarbonitrile
[6] (2.56 g, 10 mmol). Colorless needles; m.p. 124–125 °C
(acetone/petroleum ether). – 13C NMR (125 MHz): 46.3, 50.9,
51.6, 52.6, 52.7, 55.0, 66.2, 84.8, 119.1, 125.4, 128.7, 128.8,
139.5, 165.4, 167.7, 168.0. – MS (EI) m/z (%): 386 (32) [M+].
Dimethyl (4-Cyano-2-methyl-5-pyrrolidino-(2H)-furan-3-
ylidene)propanedioate 5d
From 4d (0.92 g, 3 mmol). Colorless prisms; m.p. 163–
164 °C (CH2Cl2/petroleum ether).
Diethyl (4-Cyano-2,3-dihydro-2-phenyl-5-pyrrolidino-furan-
Dimethyl (4-Cyano-2-methyl-5-morpholino-furan-3-yl)pro-
3-yl)propanedioate 4i
panedioate 5e
From 4,5-dihydro-5-phenyl-2-pyrrolidino-3-furancarbonitrile
From 4e. Colorless needles; m.p. 58–59 °C (diethyl ether/
[6] (2.40 g,10 mmol). Colorless columns; m.p. 90 °C (diethyl
petroleum ether).
564
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Rhodium(II) Acetate-Catalyzed Reaction of 2-Amino-4,5-dihydro-3-furancarbonitriles
___________________________________________________________________________ FULL PAPER
Dimethyl (4-Cyano-2-phenyl-5-pyrrolidino-furan-3-yl)pro-
panedioate 5f
Diethyl (4-Cyano-2-phenyl-5-pyrrolidino-furan-3-yl)propa-
nedioate 5i
From 4f (1.11 g, 3 mmol). Colorless prisms; m.p. 169–
170 °C (CH2Cl2/petroleum ether).
From 4i (1.19 g, 3 mmol ). Colorless prisms; m.p. 118–
119 °C (diethyl ether/petroleum ether).
Dimethyl (4-Cyano-2-phenyl-5-piperidino-furan-3-yl)pro-
panedioate 5g
Diethyl (4-Cyano-2-phenyl-5-piperidino-furan-3-yl)propane-
diate 5j
From 4g (1.15 g, 3 mmol). Colorless prisms; m.p. 145–
146 °C (CH2Cl2/petroleum ether).
From 4j (1.24 g, 3 mmol). Colorless prisms; m.p. 109–
110 °C (diethyl ether/petroleum ether). – MS (FAB) m/z (%):
411 (56) [M+ + H].
Dimethyl (4-Cyano-2-methyl-5-morpholino-furan-3-yl)pro-
panedioate 5h
Diethyl (4-Cyano-5-morpholino-2-phenyl-furan-3-yl)pro-
panedioate 5k
From 4h (1.16 g, 3 mmol). Colorless columns; m.p. 159–
160 °C (CH2Cl2/petroleum ether).
From 4k (1.24 g, 3 mmol). Colorless prisms; m.p. 116–
117 °C (diethyl ether/petroleum ether).
Table 1 Analytical and IR spectral data of 4a–k, 5a–k
Formula
Analysis Calcd./Found
IR ν (cm–1)
C
H
N
C≡N
C=O
1730
4a
C14H18N2O5
(294.3)
57.13
57.29
58.43
58.46
54.19
54.30
58.43
58.50
55.55
55.69
64.85
64.94
65.61
65.75
62.17
62.30
66.32
66.51
67.02
66.95
63.76
63.90
57.53
57.42
58.82
58.81
54.54
54.59
58.82
58.80
55.90
55.89
65.21
65.30
65.96
65.95
62.49
62.27
66.65
66.69
67.30
67.31
64.07
64.08
6.17
6.20
6.54
6.64
5.85
5.97
6.54
6.53
6.22
6.25
5.99
6.02
6.29
6.43
5.74
5.81
6.58
6.74
6.84
6.67
6.32
6.28
5.52
5.55
5.92
5.87
5.23
5.30
5.92
5.86
5.63
5.68
5.47
5.39
5.80
5.78
5.24
5.23
6.10
6.05
6.38
6.40
5.87
5.85
9.52
9.52
9.09
9.11
9.03
9.05
9.09
9.16
8.64
8.67
7.65
7.62
7.29
7.39
7.25
7.32
7.03
7.16
6.79
6.74
6.76
6.95
9.58
9.39
9.15
9.02
9.09
8.87
9.15
9.08
8.69
8.47
7.60
7.69
7.33
7.30
7.29
7.22
7.07
6.94
6.82
6.79
6.79
6.69
2 170
4b C15H20N2O5
2 170
2 170
2 170
2 170
2 170
2 175
2 180
2 195
2 190
2 180
2 200
2 200
2 200
2 205
2 210
2 190
2 200
2 200
2 200
2 205
2 210
1740
(308.3)
C14H18N2O6
(310.3)
4c
1740
1727 (sh)
1745
1727
1750
1730
1750 (sh)
1735
4d C15H20N2O5
(308.3)
C15H20N2O6
(324.3)
C20H22N2O5
(370.4)
C21H24N2O5
(384.4)
4e
4f
4g
1740
4h C20H22N2O6
1744
1728
1745
1730
1750 (sh)
1735
1750 (sh)
1730
1720
1690
1725
1685
1720
1690
1730
1680
1760
1735
(386.4)
C22H26N2O5
(398.5)
C23H28N2O5
(412.5)
4i
4j
4k C22H26N2O6
(414.5)
C14H16N2O5
(292.3)
5a
5b C15H18N2O5
(306.3)
C14H16N2O6
(308.3)
5c
5d C15H18N2O5
(306.3)
C15H18N2O6
(322.3)
C20H20N2O5
(368.4)
C21H22N2O5
(382.4)
5e
5f
1750 (sh)
1725
1755
1735 (sh)
1750 (sh)
1735
5g
5h C20H20N2O6
(384.4)
C22H24N2O5
(396.4)
C23H26N2O5
(410.5)
5i
5j
1740
1735 (sh)
1745 (sh)
1735
1745 (sh)
1730
5k C22H24N2O6
(412.4)
J. Prakt. Chem. 1999, 341, No. 6
565