Double 1,4-addition of malonate to 1,2-diaza-1,3-butadienes: A useful route to previously unknown symmetric and unsymmetric 1,6-dioxo-2,7-diazaspiro [4.4] nona-3,8-dienes

Article abstract of DOI:10.1039/b009189h

In the presence of sodium methoxide in tetrahydrofuran, 1,2-diaza-1,3-butadienes react with dimethyl malonate in a 2:1 molar ratio to give symmetric or unsymmetric bishydrazones that in turn produce new 1,6-dioxo-2,7-diazaspiro [4.4] nona-3,8-dienes, as a consequence of a double ring closure, on treatment with sodium methoxide in methanol.

Full text of DOI:10.1039/b009189h

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Double 1,4-addition of malonate to 1,2-diaza-1,3-butadienes: a useful
route to previously unknown symmetric and unsymmetric
1,6-dioxo-2,7-diazaspiro[4.4]nona-3,8-dienes¤
Orazio A. Attanasi,* Lucia De Crescentini, Paolino Filippone and Fabio Mantellini
L e t t e r
Istituto di Chimica Organica, Universita di Urbino, Piazza della Repubblica 13, I-61029 Urbino,
Italy. E-mail: attanasi=uniurb.it; Fax: ]39 0722 2907
Received (in Freiburg, Germany) 17th October 2000, Accepted 13th February 2001
In the presence of sodium methoxide in tetrahydrofuran, 1,2-
diaza-1,3-butadienes react with dimethyl malonate in a 2 : 1
molar ratio to give symmetric or unsymmetric bishydrazones
that in turn produce new 1,6-dioxo-2,7-diazaspiro[4.4]nona-
3,8-dienes, as a consequence of a double ring closure, on treat-
ment with sodium methoxide in methanol.
were converted into symmetric 1,6-dioxo-2,7-diazaspiro[4.4]
nona-3,8-dienes (4aÈd, Table 2) by means of a double Ðve-
membered ring closure (Scheme 1) that occurs with loss of two
alcohol molecules, as already demonstrated in our previous
works.7
The 1H-NMR spectrum of compound 4b shows two signals
for the methyl (2.32 and 2.36 ppm), ethyl ester (multiplets at
1.06È1.23 and 3.91È4.14 ppm) and NH (9.06 and 9.09 ppm)
groups. This behaviour is probably due to a hindered rota-
tion, as proved by the same spectrum recorded at 60 ¡C
(triplet at 1.14 ppm, singlet at 2.35 ppm, quartet at 4.05 ppm
and broad singlet at 8.84 ppm).
In order to obtain unsymmetric 1,6-dioxo-2,7-
diazaspiro[4.4]nona-3,8-dienes, 1,2-diaza-1,3-butadienes (1eÈ
g) and dimethyl malonate were used in an equimolar ratio. In
the presence of a catalytic amount of sodium methoxide in
tetrahydrofuran at room temperature, these reagents gave
monohydrazone adducts (2aÈc, Table 3). Again in the presence
1,2-Diaza-1,3-butadienes have been demonstrated to be
powerful building blocks in organic synthesis.1h5 Since an
extensive bibliographic search showed that 1,6-dioxo-2,7-
diazaspiro[4,4]nona-3,8-dienes are unknown molecules,6 we
decided to consider a possible synthetic route starting from
1,2-diaza-1,3-butadienes in view of the potential interest of the
aforementioned derivatives as organic, medicinal, and agricul-
tural products. Based on our experience of this chemistry3,4
and retrosynthetic analysis, we hypothesised a facile two-step
protocol to reach smoothly this new class of spiro compounds
by unprecedented double 1,4-addition of malonates to two
identical or two di†erent 1,2-diaza-1,3-butadienes and double
ring closure.
In the presence of a catalytic amount of sodium methoxide
in tetrahydrofuran, 1,2-diaza-1,3-butadienes (1aÈd) reacted at
room temperature with dimethyl malonate in a molar ratio of
2 : 1 to give the symmetric bishydrazone adducts (3aÈd) as
shown in Table 1. With a stoichiometric amount of sodium
methoxide in methanol at room temperature, these adducts
Table 1 Yield, melting point and reaction time required for bis-
hydrazones 3aÈd
1
R1
R2
3
Yielda(%)
mpb/¡C
Time/h
a
b
c
Me
Et
Bz
NHPh
a
b
c
61
74
68
78
204È206c
142È147
157È162
167È171c
1.0
3.0
9.0
3.0
NH
NH
2
2
d
Me
OBut
d
¤ Electronic supplementary information (ESI) available: full charac-
terisation of 2b, c, 3a, c, d, fÈh, 4a, c, d, fÈh. See http://www.rsc.org/
suppdata/nj/b0/b009189h/
a Yield of pure isolated products. b Melting points are uncorrected.
c Melting occurs with decomposition.
Table 2 Yield, melting point and reaction time required for 1,6-dioxo-2,7-diazaspiro[4.4]nona-3,8-dienes 4aÈh
3
R1
R2
R3
R4
4
Yielda(%)
mpb/¡C
Time/h
a
b
c
d
e
f
Me
Et
Bz
Me
Et
Me
Me
Et
NHPh
a
b
c
d
e
f
62
94
86
92
74
65
63
86
196È198c
236È238
238È240c
201È203
169È172c
193È195
171È175
188È190
4.0
2.0
2.5
1.0
1.5
4.5
3.0
3.0
NH
2
NH
2
OBut
NH(3-FPh)
NHPh
NHPh
Me
Et
Et
NH
OBut
2
g
h
NH
NH
2
g
h
2
OBut
Et
a Yield of pure isolated products. b Melting points are uncorrected. c Melting occurs with decomposition.
534
New J. Chem., 2001, 25, 534È537
DOI: 10.1039/b009189h
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2001

View Article Online
Scheme 1
of a catalytic amount of sodium methoxide in tetrahydrofuran
at room temperature, these adducts readily reacted with
another equivalent of a di†erent 1,2-diaza-1,3-butadiene (1b, g,
h) to a†ord unsymmetric bishydrazones (3eÈh, Table 4). With
a stoichiometric amount of sodium methoxide in methanol at
room temperature, these latter adducts were converted into
the corresponding asymmetric 1,6-dioxo-2,7-diazaspiro[4.4]
nona-3,8-dienes (4eÈh, Table 2).
Bishydrazones 3aÈe were obtained as isomer mixtures and
used as such for the subsequent cyclisation.
In conclusion, this method o†ers simple and high yield
access under mild reaction conditions to previously unknown
1,6-dioxo-2,7-diazaspiro[4.4]nona-3,8-dienes, the chemical,
physico-chemical and biological properties of which
undoubtedly merit further investigation.
Table 3 Yield, melting point and reaction time required for hydra-
zones 2aÈc
1
R1
R2
2
Yielda(%)
mpb/¡C
Time/h
e
f
g
Et
Me
Et
NH(3-FPh)
NHPh
OBut
a
b
c
75
91
89
153È155
145È147
90È93
0.1
0.1
0.1
Experimental
Melting points were determined in open capillary tubes and
are uncorrected. IR-FT spectra were obtained from Nujol
a Yield of pure isolated products. b Melting points are uncorrected.
Table 4 Yield, melting point and reaction time required for bishydrazones 3eÈh
2
R1
R2
1
R3
R4
3
Yielda(%)
mpb/¡C
Time/h
a
b
b
c
Et
NH(3-FPh)
NHPh
NHPh
h
g
b
b
Me
Et
Et
NH
OBut
NH
NH
2
e
f
60
91
58
61
123È125c
143È148c
150È154
145È151c
8.5
8.0
3.0
5.0
2
Me
Me
Et
g
h
2
OBut
Et
a Yield of pure isolated products. b Melting points are uncorrected. c Melting occurs with decomposition.
New J. Chem., 2001, 25, 534È537
535

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mulls. 1H-NMR spectra at 25 and 60 ¡C were recorded at 200
MHz and 13C-NMR spectra at 50.32 MHz. All coupling con-
(q), 52.9 (q), 55.7 (d), 56.4 (d), 60.3 (s), 60.7 (s), 61.7 (t), 61.8 (t),
144.5 (s), 145.1 (s), 158.2 (s), 169.1 (s), 169.4 (s), 170.1 (s), 170.5
(s); MS m/z (rel. intensity): 502 (M`, 1), 428 (29), 368 (57), 354
stants (J) are given in Hz. Chemical shifts (d ) are reported
C
relative to DMSO-d or CDCl as external standards in a
(100). Anal. calc. for C
16.73; found: C, 45.31; H, 6.21; N, 16.59%.
H
N O : C, 45.42; H, 6.02; N,
6
3
19 30
6
10
broad band decoupled mode. The multiplicities were obtained
by using 135 and 90¡ DEPT experiments to aid in assignment
(q \ methyl, t \ methylene, d \ methyne, s \ quaternary).
Preparation of unsymmetric bishydrazone 3e. To a magneti-
cally stirred solution of 1,2-diaza-1,3-butadiene 1h (2.0 mmol,
342.3 mg) and sodium methoxide (0.1 mmol, 5.4 mg) in THF
(4 ml), was added a solution of monohydrazone 2a (1.0 mmol,
411.4 mg) in THF (4 ml). The reaction mixture was allowed to
stand at room temperature until the total disappearance of 2a
(8.5 h, monitored by TLC) had occurred. Product 3e was puri-
Ðed by chromatography on a silica gel column (cyclohexaneÈ
ethyl acetate mixture) and then crystallised from diethyl etherÈ
petroleum ether (bp 40È60 ¡C). 3-Ethyl-4,4,5-trimethyl-2(3-
Ñuoroanilinocarbonyl)hydrazono - 6 - aminocarbonyl - hydra-
zonoheptane-3,4,4,5-tetracarboxylate (3e): white powder; IR
(Nujol): 3420, 3380, 3225, 3128, 1738, 1721, 1708, 1599 cm~1;
1H-NMR (DMSO-d ): d 1.24 (t, 3 H, J \ 7.1, OCH CH ),
Syntheses
The full characterisation of all products not listed below is
given in the electronic supplementary information.
Preparation of 1,2-diaza-1,3-butadienes 1a–g. These com-
pounds were prepared according to methods given in previous
papers.8 1e: red powder; mp 71È74 ¡C; IR (Nujol): 3467,
3203, 1720, 1618 cm~1; 1H-NMR (DMSO-d ): d 1.29 (t, 3 H,
6
J \ 7.1, OCH CH ), 2.25 (s, 3 H, CH ), 4.27 (q, 2 H, J \ 7.1,
2
3
3
OCH CH ), 6.99È7.05 (m, 1 H ), 7.37È7.66 (m, 4 H, 3 H and
2
3
ar
ar
CH), 11.07 (s, 1 H, NH, D O exch.); 13C-NMR (DMSO-d ):
2
6
6
2
3
d 10.8 (q), 14.0 (q), 60.8 (t), 106.0 (d, 2J \ 26.0), 111.0 (d,
1.93 and 1.99 (2 s, 6 H, 2 CH ), 3.73, 3.79 and 3.84 (3 s, 9 H, 3
CF
3
2J \ 20.0), 115.4 (d), 130.7 (d, 3J \ 9.4), 131.5 (d), 139.4 (s,
OCH ), 4.05È4.35 (m, 4 H, OCH CH and 2 CH), 5.99 (br s,
NH , D O exch.), 6.66È6.74 (m, 1 H ), 7.16È7.57 (m, 3 H ),
8.04 and 8.14 (2 s, 1 H, NH, D O exch.), 9.07 and 9.14 (2 s, 1
CF
CF
CF
CF
3
2
3
ar
3J \ 11.0), 152.3 (s), 162.3 (s, 1J \ 251.0), 165.2 (s); MS
2
2
ar
m/z (rel. intensity): 279 (M`, 11), 234 (7), 149 (51), 138 (100).
2
Anal. calc. for C
found: C, 56.01; H, 5.23; N, 15.11%.
H
N O F: C, 55.91; H, 5.05; N, 15.05;
H, NH, D O exch.), 9.76 (s, 1 H, NH, D O exch.); 13C-NMR
13 14
3
3
2
6
2
(DMSO-d ): d 14.5 (q), 14.9 (q), 17.5 (q), 17.7 (q), 17.9 (q), 18.1
(q), 52.0 (q), 52.2 (q), 52.4 (q), 52.8 (q), 55.1 (d), 55.5 (d), 56.2 (d),
Preparation of monohydrazone 2a. To a magnetically stirred
solution of 1,2-diaza-1,3-butadiene 1e (1.0 mmol, 279.3 mg)
and dimethyl malonate (1.0 mmol, 132.1 mg) in THF (8 ml), a
catalytic amount of sodium methoxide (0.1 mmol, 5.4 mg) was
added. The disappearance of the reagents occurred rapidly
(0.1 h, monitored by TLC). Product 2a was puriÐed by chro-
matography on a silica gel column (cyclohexaneÈethyl acetate
mixture) and then crystallised from ethyl acetateÈpetroleum
ether (bp 40È60 ¡C). Methyl 2-methoxycarbonyl-3-ethoxycar-
bonyl-4-(3-Ñuoroanilinocarbonylhydrazono)pentanoate (2a):
white powder; IR (Nujol): 3359, 3201, 3102, 1731, 1705, 1613,
60.3 (t), 61.8 (s), 106.2 (d, 2J \ 26.7), 109.5 (d, 2J \ 21.4),
CF
CF
114.3 (d), 129.8 (d, 3J \ 9.3), 140.1 (s, 3J \ 11.3), 144.7 (s),
CF
CF
145.1 (s), 145.8 (s), 154.2 (s), 154.3 (s), 158.0 (s), 158.2 (s), 162.9
(s, 1J \ 243.0), 168.7 (s), 168.8 (s), 169.3 (s), 169.6 (s), 170.3 (s),
CF
171.8 (s); MS m/z (rel. intensity): 582 (M`, 1), 537 (40), 524
(50), 508 (100). Anal. calc. for C
5.36; N, 14.43; found: C, 49.42; H, 5.24; N, 14.51%.
H
N O F: C, 49.48; H,
24 31
6
10
Preparation
of
symmetric
1,6-dioxo-2,7-diazaspiro-
[4.4]nona-3,8-diene 4b and unsymmetric 1,6-dioxo-2,7-diaza-
spiro[4.4]nona-3,8-diene 4e. To a magnetically stirred solution
of bishydrazones 3b (1.0 mmol, 502.5 mg) and 3e (1.0 mmol,
582.5 mg) in methanol (6 ml), was added sodium methoxide (1
mmol, 54.0 mg). The reaction mixture was allowed to stand at
room temperature until the disappearance of 3 (1.5È2.0 h,
monitored by TLC) was complete. Products 4b and 4e were
1598 cm~1; 1H-NMR (DMSO-d ): d 1.18 (t, 3 H, J \ 7.1,
6
OCH CH ), 1.95 (s, 3 H, CH ), 3.57 (s, 3 H, OCH ), 3.66 (s, 3
2
3
3
3
H, OCH ), 4.02 (d, 1 H, J \ 10.0, CH), 4.13 (q, 2 H, J \ 7.1,
3
OCH CH ), 4.52 (d, 1 H, J \ 10.0, CH), 6.82È6.84 (m, 1 H ),
2
3
ar
7.31È7.37 (m, 2 H ), 7.57È7.63 (m, 1 H ), 8.66 (s, 1 H, NH,
ar
ar
D O exch.), 9.96 (s, 1 H, NH,D O exch.); 13C-NMR (DMSO-
puriÐed by chromatography on
a
silica gel column
2
2
d ): d 13.8 (q), 16.0 (q), 51.1 (d), 52.6 (q and d), 61.2 (t), 105.8
(cyclohexaneÈethyl acetate mixture) and then crystallised from
ethyl acetateÈpetroleum ether (bp 40È60 ¡C). N-(7-Amino-
carbonylamino-3,8-dimethyl-4,9-diethoxycarbonyl-1,6-dioxo-
6
(d, 2J \ 26.3), 108.7 (d, 2J \ 21.0), 114.6 (d), 130.1 (d,
CF
CF
3J \ 14.4), 140.7 (s, 3J \ 11.4), 144.4 (s), 153.0 (s), 162.3 (s,
CF
CF
CF
1J \ 250.0), 186.0 (s), 189.0 (s); MS m/z (rel. intensity): 411
2,7-diazaspiro[4.4]nona-3,8-dien-2-yl)-N@-phenylurea
(4b):
(M`, 29), 301 (59), 223 (51), 196 (81), 169 (100). Anal. calc. for
white powder; IR (Nujol): 3482, 3459, 3345, 1755, 1744, 1699,
C
H
N O F: C, 52.55; H, 5.39; N, 10.21; found: C, 52.41;
1693, 1646 cm~1; 1H-NMR (DMSO-d ) d 1.06È1.23 (m, 6 H,
18 22
3
7
6
H, 5.44; N, 10.35%.
2 OCH CH ), 2.32 and 2.36 (2 s, 6 H, 2 CH ), 3.91È4.14 (m, 4
2
3
3
H, 2 OCH CH ), 6.23 (br s, 4 H, 2 NH , D O exch.), 8.97 and
2
3
2
2
Preparation of symmetric bishydrazone 3b. To a magneti-
cally stirred solution of 1,2-diaza-1,3-butadiene 1b (3.0 mmol,
555.6 mg) and sodium methoxide (0.1 mmol, 5.4 mg) in THF
(4 ml), was added a solution of dimethyl malonate (1.0 mmol,
132.1 mg) in THF (4 ml). The reaction mixture was allowed to
stand at room temperature until complete disappearance of
dimethyl malonate (2.0 h, monitored by TLC) had occurred.
Product 3b was puriÐed by chromatography on a silica gel
column (cyclohexaneÈethyl acetate mixture) and then crys-
tallised from ethyl acetateÈpetroleum ether (bp 40È60 ¡C). 3,5-
Diethyl - 4,4 - dimethyl - 2,6 - bis(2 - aminocarbonylhydrazono)
heptane-3,4,4,5-tetracarboxylate (3b): white powder; IR
(Nujol): 3483, 3456, 3218, 1746, 1742, 1699 cm~1; 1H-NMR
(CDCl ) d 1.25 (t, 6 H, J \ 7.1, 2 OCH CH ), 1.93 (s, 6 H, 2
8.99 (2 s, 1 H, NH, D O exch.), 9.06 and 9.09 (2 s, 1 H, NH,
2
D O exch.); 13C-NMR (DMSO-d ): d 11.5 (q), 11.7 (q), 13.9
2
6
(q), 59.6 (t), 59.7 (t), 60.2 (s), 103.3 (s), 103.9 (s), 156.7 (s), 158.0
(s), 158.2 (s), 158.8 (s), 161.7 (s), 162.5 (s), 169.4 (s), 169.9 (s); MS
m/z (rel. intensity): 438 (M`, 9), 395 (37), 349 (50), 306 (37),
279 (100). Anal. calc. for C
H
N O : C, 46.58; H, 5.06; N,
17 22
6 8
19.17; found: C, 46.64; H, 5.12; N, 19.04%. N-(7-
Aminocarbonylamino - 3,8 - dimethyl - 4 - ethoxycarbonyl - 9 -
methoxycarbonyl - 1,6 - dioxo - 2,7 - diazaspiro[4.4] - nona - 3,8 -
dien-2-yl)-N@-3-Ñuorophenylurea (4e): white powder; IR
(Nujol): 3418, 3378, 3218, 1743, 1720, 1700 cm~1; 1H-NMR
(DMSO-d ): d 1.26 (t, 3 H, J \ 7.1, OCH CH ), 2.47 (s, 6 H, 2
6
2
3
CH ), 3.80 (s, 3 H, OCH ), 4.17 (q, 2 H, J \ 7.1, OCH CH ),
3
3
2
3
5.73 and 6.36 (2 br s, NH , D O exch.), 6.70È6.77 (m, 1 H ),
ar
7.00È7.46 (m, 3 H ), 7.97 and 8.05 (2 br s, 2 H, 2 NH, D O
ar
3
2
3
2
2
CH ), 3.77 and 3.78 (2 s, 6 H, 2 OCH ), 4.02 and 4.25 (2 s, 2 H,
2 CH), 4.19 (q, 4 H, J \ 7.1, 2 OCH CH ), 5.25 and 5.86 (2 br
s, 4 H, 2 NH , D O exch.), 8.56 and 9.28 (2 s, 2 H, 2 NH, D O
exch.); 13C-NMR (CDCl ): d 14.0 (q), 16.7 (q), 17.3 (q), 52.7
3
3
2
2
6
exch.), 8.44 (s, 1 H, NH, D O exch.); 13C-NMR (DMSO-d ):
3
2
d 12.2 (q), 12.4 (q), 14.1 (q), 52.2 (q), 60.4 (s), 61.4 (t), 104.8 (s),
105.4 (s), 107.2 (d, 2J \ 26.5), 110.2 (d, 2J \ 21.2), 115.1
2
2
2
3
CF
CF
536
New J. Chem., 2001, 25, 534È537

View Article Online
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T etrahedron, 1998, 54, 5315.
(d), 129.8 (d, 3J \ 9.3), 139.2 (s, 3J \ 10.8), 154.1 (s), 157.6
CF
CF
(s), 158.1 (s), 160.5 (s), 162.3 (s), 162.9 (s, 1J \ 242.1), 163.3 (s),
CF
163.8 (s), 169.9 (s), 170.4 (s); MS m/z (rel. intensity): 518 (M`,
5), 475 (24), 443 (14), 381 (41), 338 (100). Anal. calc. for
C
H
N O F: C, 50.97; H, 4.47; N, 16.21; found: C, 50.84;
22 23
6 8
H, 4.53; N, 16.40%.
Acknowledgements
This work was supported by Ðnancial assistance from the
Consiglio Nazionale delle Ricerche (C.N.R.-Roma) and the
Universita degli Studi di Urbino.
5
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