Regioselective synthesis of 5-ylidenepyrrol-2(5H)-ones by reaction of transition metal-coordinated bis(imidoyl) chlorides with carbon nucleophiles

Article abstract of DOI:10.1021/jo9805910

A regioselective transition metal mediated domino reaction of carbon nucleophiles with oxalic acid-bis(imidoyl)chlorides is reported. This reaction provides a convenient access to E-configured 5-ylidenepyrrol-2(5H)- ones. Without the presence of cobalt(II) or nickel(II) salts, open-chained products were obtained. The regioselective cyclization is controlled by the coordination of the nitrogen atoms of the 1,4-diazadiene system to the transition metal.

Full text of DOI:10.1021/jo9805910

J . Org. Chem. 1999, 64, 365-372
365
Regioselective Syn th esis of 5-Ylid en ep yr r ol-2(5H)-on es by
Rea ction of Tr a n sition Meta l-Coor d in a ted Bis(im id oyl) Ch lor id es
w ith Ca r bon Nu cleop h iles
J o¨rg Wuckelt,† Manfred Do¨ring,*,† Peter Langer,*,‡ Rainer Beckert,§ and Helmar Go¨rls†
Institut fu¨r Anorganische und Analytische Chemie der Universita¨t J ena, August-Bebel-Strasse 2,
07743 J ena, Germany, Institut fu¨r Organische Chemie der Georg-August-Universita¨t Go¨ttingen,
Tammannstrasse 2, 37077 Go¨ttingen, Germany, and Institut fu¨r Organische und Makromolekulare
Chemie der Universita¨t J ena, Humboldtstrasse 10, 07743 J ena, Germany
Received March 31, 1998
A regioselective transition metal mediated domino reaction of carbon nucleophiles with oxalic acid-
bis(imidoyl)chlorides is reported. This reaction provides a convenient access to E-configured
5-ylidenepyrrol-2(5H)-ones. Without the presence of cobalt(II) or nickel(II) salts, open-chained
products were obtained. The regioselective cyclization is controlled by the coordination of the nitrogen
atoms of the 1,4-diazadiene system to the transition metal.
The 1,2-dione unit represents an important structural
feature of compounds of pharmaceutical interest1a and
of materials such as NIR dyes.1b 1,2-Diones can be
obtained by reaction of oxalyl chloride with carbon
nucleophiles. For example, oxalyldimalonic acid deriva-
tives 1a 2a and 1b2b have been recently prepared from
oxalyl chloride as pharmaceutically relevant analogues
of natural pulvinic acid 1c.3 Saalfrank and co-workers
have reported a self-assembly process of transition and
main group metals using deprotonated 1a as a tetraden-
tate ligand.2a
be fine-tuned by varying the substituents at the nitrogens
and at the internal carbon atoms of the diazabutadiene
backbone.
En route to the development of new syntheses of
functionalized 1,4-diazabutadienes and of azaanalogues
of heterocycles 1b,c, we are interested in the reaction of
oxalic acid-bis(imidoyl)chlorides C2Cl2(NAr)2 2 with car-
bon nucleophiles.6 Recently, we have reported the forma-
tion of pyrrolo[3,2-b]pyrrole-2,5-diones 3, azaanalogous
derivatives of pulvinic acid, by reaction of 2 with carb-
anions of alkyl- and aryl-substituted acetic esters via bis-
enamine intermediates A-4 (Scheme 1).7 These reactions
involve attack of the nitrogen atoms on the ester carbonyl
groups. Cyclization can, in principle, occur not only by
attack of a nitrogen atom but also by attack of a carbon
atom on the ester group. Herein, we report full details
of a new C-regioselective cobalt(II)-mediated cyclization
which provides a convenient access to 5-ylidenepyrrol-
2(5H)-ones 5.8 In addition, experiments related to ques-
tions of the mechanism and the preparation of azaana-
logues of oxalyldimalonic acid derivatives 1a are reported.
The development of diimine-ligated transition metal
complexes 2-MX2 as components of efficient catalyst
systems for olefin polymerization by Brookhart et al.4 has
given rise to a renewed interest in the chemistry of 1,2-
dione-derived 1,4-diazabuta-1,3-dienes. The steric and
the electronic properties of these versatile ligands5 can
Sch em e 1
† Institut fu¨r Anorganische und Analytische Chemie der Universita¨t
J ena.
‡ Institut fu¨r Organische Chemie der Georg-August-Universita¨t
Go¨ttingen.
2
Na[N(SiMe3)2]
§ Institut fu¨r Organische und Makromolekulare Chemie der Uni-
versita¨t J ena.
(1) (a) Chiu, C. C.; J ordan, F. J . Org. Chem. 1994, 59, 5763-5766.
(b) Fabian, J .; Nakazumi, H.; Matsuoka, M. Chem. Rev. 1992, 92, 1197.
(2) (a) Saalfrank, R. W.; Stark, A.; Bremer, M.; Hummel, H.-U.
Angew. Chem. 1990, 102, 292; Angew. Chem., Int. Ed. Engl. 1990, 29,
311. (b) Stachel, H.-D.; Schorp, M.; Maier, L.; Dandl, K. Liebigs Ann.
Chem. 1994, 1121.
(3) (a) Rao, Y. S. Chem. Rev. 1976, 76, 625. (b) Pattenden, G.
Fortschr. Chem. Org. Naturst. 1978, 35, 133.
(4) (a) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem.
Soc. 1995, 117, 6414. (b) J ohnson, L. K.; Mecking, S.; Brookhart, M.
J . Am. Chem. Soc. 1996, 118, 267. (c) Killian, C. M.; Tempel, D. J .;
J ohnson, L. K.; Brookhart, M. J . Am. Chem. Soc. 1996, 118, 11664.
(d) Killian, C. M.; J ohnson, L. K.; Brookhart, M. Organometallics 1997,
16, 2005. (e) Abu-Surrah, A. S.; Rieger, B. Angew. Chem. 1996, 108,
2627; Angew. Chem., Int. Ed. Engl. 1996, 35, 2475.
Resu lts a n d Discu ssion
Reaction of bis(imidoyl)chlorides 2a -b,d (1.0 equiv)
with sodium diethyl malonate (2.0 equiv) (generated by
means of 2.0 equiv of Na[N(SiMe3)2]) in the presence of
10.1021/jo9805910 CCC: $18.00 © 1999 American Chemical Society
Published on Web 01/05/1999

366 J . Org. Chem., Vol. 64, No. 2, 1999
Wuckelt et al.
percenta
Ta ble 1
c
entry
2
5
R
Ar
additive (equiv)b
λ1
λ2
λ3
1
2
3
4
5
6
7
8
9
a
b
d
a
a
a
a
a
b
c
e
a
b
c
d
d
d
d
d
e
f
CO2Et
CO2Et
CO2Et
CN
CN
CN
CN
CN
CN
CN
Tol
Ph
CoCl2 (1)
CoBr2 (1)
CoBr2 (1)
CoBr2 (1)
CoBr2 (2)
CoBr2 (cat.)
NiBr2 (1)
BF3‚OEt2 (1)
CoBr2 (1)
CoCl2 (1)
CoBr2 (1)
273 (4.01)
270 (3.96)
324 (4.26)
266 (3.82)
340 (3.94)
341 (3.91)
368 (4.28)
365 (4.09)
54
61
56
71
68
0d
73
0
p-(NO2)C6H4
Tol
Tol
Tol
Tol
Tol
Ph
417 (4.16)
260 (3.82)
269 (3.86)
362 (4.12)
340 (3.99)
408 (4.19)
413 (4.12)
74
66
0
10
11
p-(MeO)C6H4
Tosyl
g
CN
a
b
d
Isolated yield. Equivalents related to 2 equiv of 2. c UV/vis [nm] (acetonitrile). Formation of an open-chained product.
cobalt(II) or nickel(II) salts and an excess of Na[N-
(SiMe3)2] (1.5 equiv) resulted in regioselective C-cycliza-
tion to give 5-ylidenepyrrol-2(5H)-ones 5a -c in generally
good yields (54-61%). Reaction of 2a -c with sodium
ethyl cyanoacetate proceeded equally well to give E-
configured 5-ylidenepyrrol-2(5H)-ones 5d -f (66-74%). To
prepare the N-deprotected heterocyclic core structure,
sodium ethyl cyanoacetate was reacted with tosyl-
substituted bis(imidoyl)chloride 2e. Unfortunately, this
reaction resulted in formation of a complex product
mixture (Table 1, entry 11). Similarly, the use of benzyl
derivatives of 2 was not successful. In case of the yellow
colored triesters 5a -c the π f π* transitions (λ2) are
observed at ca. 340 nm. Auxochromic effects are observed
for λ2 when two of the three ester functions are replaced
by cyano groups and additional π f π* transitions (λ3)
are detected (Table 1).
Sch em e 2a
It is noteworthy, that employment of BF3‚OEt2 rather
than CoBr2 resulted in decomposition rather than in
cyclization (Table 1, entry 8). No cyclization but formation
of open-chained products was observed in the reaction
of ethyl cyanoacetate with 2a when only catalytic amounts
of cobalt(II) bromide were used (entry 6). In contrast,
cyclization was observed when 2 equiv of CoBr2 rather
than only 1 was employed (entry 5). The reaction
proceeded equally well with NiBr2 instead of CoBr2 (entry
7).
Formation of 5-ylidenepyrrol-2(5H)-ones 5 can be
rationalized by the following mechanism (Scheme 2): A
cobalt(II)-1,4-diazadiene complex (2-CoBr 2) is initially
formed by complexation of CoBr2 with bis(imidoyl) chlo-
rides 2. Attack of the carbanion on 2-CoBr 2 affords the
3-amino-1-azadiene complex 79 which undergoes a ring
closure reaction to give intermediate 8 (being an unstable
tetracarbonylmethane derivative). Rearrangement of the
latter to 9, subsequent Dimroth rearrangement (before
or after decomplexation), and aqueous work up finally
afford 5-ylidenepyrrol-2(5H)-ones 5a -f. A related com-
pound has been previously prepared in a multistep
procedure in low overall yield (ca. 10%).2b
i
aReagents and conditions: i 1. KOH/H2O (1 mol/L), 30 min, 50
°C; 2. HCl (2 mol/L). Yields: 6a , 72%; 6b, 70%.
Experiments to explore the reactivity of heterocycles
5 were first carried out. Treatment of 5a with potassium
hydroxide gave the bicyclic anhydride 6a (72%) contain-
ing a new heterocyclic core structure. It is noteworthy
that only two of the three ester groups are selectively
hydrolyzed under the reaction conditions employed.
Treatment of the monoester 5d with potassium hydroxide
resulted in saponification of the ester group to give the
acid 6b (70%).
(5) (a) van Koten, G.; Vrieze, K. Adv. Organomet. Chem. 1982, 21,
151. (b) Vrieze, K: J . Organomet. Chem. 1986, 300, 307. (c) tom Dieck,
H.; Dietrich, J . Chem. Ber. 1984, 117, 694.
(6) For the reaction of delocalized dianions with bis(imidoyl) chlo-
rides, see: (a) Langer, P.; Do¨ring, M.; Go¨rls, H.; Beckert, R. Liebigs
Ann./ Receuil 1997, 2553. (b) Langer, P.; Do¨ring, M. Synlett 1998, 396.
(c) Langer, P.; Do¨ring, M. Synlett 1998, 396. (d) Langer, P.; Wuckelt,
J .; Do¨ring, M.; Beckert, R. Eur. J . Org. Chem. 1998, 1467.
(7) Wuckelt, J .; Do¨ring, M.; Langer, P.; Beckert, R.; Go¨rls, H.
Tetrahedron Lett. 1997, 5269.
(8) Wuckelt, J .; Do¨ring, M.; Langer, P.; Go¨rls, H.; Beckert, R.
Tetrahedron Lett. 1998, 1135.
(9) The coordination of 3-amino-1-azadienes to transition metals is
known to proceed readily: Villacorta, G. M.; Lippard, S. J . Pure Appl.
Chem. 1986, 58, 1477.
The structures of both 5a and 5d 8 were independently
confirmed by X-ray analyses. The aryl groups of 5a and
5d are twisted out of plane. The bond lengths C1-N1,
C2-N2, and N1-C4 are decreased relative to C-N single
bonds due to the resonance within the amide and the
vinylogous amide functions. Bond length alternation is

Synthesis of 5-Ylidenepyrrol-2(5H)-ones
J . Org. Chem., Vol. 64, No. 2, 1999 367
F igu r e 1. ORTEP plot of 5a with the atom numbering scheme
referred to in the text. The thermal ellipsoids of 50% prob-
ability are shown for the non-hydrogen atoms. Selected bond
lengths [Å] and angles [deg]: O1-C2 1.209(2), N1-C1 1.339-
(3), N2-C3 1.417(2), C1-C4 1.369(3), C5-C6 1.381(3), N1-
C5 1.425(2), N2-C2 1.374(3), C1-C2 1.498(3), C3-C4 1.461-
(3); C1-N1-C5 127.6(2), C2-N2-C3 110.4(2), N1-C1-C2
115.6(2), O1-C2-N2 126.9(2), N2-C2-C1 106.4(2), C1-C4-
C3 108.4(2), C5-C6-C7 119.4(2), N1-C1-C4 136.4(2), C4-
C1-C2 107.9(2), O1-C2-C1 126.7(2), N2-C3-C4 106.8(2),
C6-N5-N1 118.9(2)
F igu r e 2. ORTEP plot of 4c with the atom numbering
scheme. The thermal ellipsoids of 50% probability are shown
for the non-hydrogen atoms. Selected bond lengths [Å] and
angles [deg]: O1-C5 1.216(2), O2-C6 1.457(2), N1-C1 1.329-
(2), N1-C8 1.437(2), C1-C3 1.383(2), C3-C5 1.461(2), O2-
C5 1.333(2), N4-C4 1.147 (2), C1-C2 1.505(2), C3-C4 1.428
(2); C5-O2-C6 116.4(1), C1-N1-C8 123.9(1), N1-C1-C3
125.5(1), C1-C3-C4 119.2(1), O1-C5-O2 124.8(1)
Sch em e 3
piperidine and -morpholine afforded bis-enamines 4e and
4f (56% and 36%, respectively). Tosyl-derivative 4g was
isolated in the reaction of bis(imidoyl)chloride 2e with
ethyl cyanoacetate.
According to the 1H and 13C NMR spectra of 4,
symmetrical structures are adopted in solution. As
indicated by the low-field shifts (1H NMR) of the respec-
tive N-H hydrogens that isomers containing intramo-
lecular hydrogen bonds (N-H‚‚‚O) are present. It is
noteworthy the configuration of these isomers is different
from that of intermediates A-4 (Scheme 1). The resonance
of the intramolecular hydrogen bond (N-H‚‚‚O) of the
amide 4e is shifted upfield relative to the resonances of
the esters 4c,d . The N-H resonances of the esters are
shifted upfield relative to the respective resonance of the
ketone 4b.
X-ray diffraction of 4c exhibits cis geometry of the
double bonds in the solid state, and thus two intramo-
lecular hydrogen bonds are observed (H‚‚‚O distances,
2.085 and 1.895 Å) (Figure 2). The diene system is twisted
out of plane (torsion angle N1-C1-C2-N2, 79.8°), and
a π-stacking interaction is observed for the aryl groups
(distance C20/21/24/25 to C8-13, 3.533 Å). The bond
length C1-C3 is increased with respect to olefinic double
bonds and C3-C5 is shortened relative to alkyl-substi-
tuted C-C single bonds due to the amide resonance
within the vinylogous amide function.
It is noteworthy that 2:1 products were also formed
when the starting materials were mixed in a 1:1 stoichi-
ometry. On the other hand, reflux of 4c and 4d in toluene
resulted in formation of complex reaction mixtures from
which C-cyclization products 5d and 5e were isolated in
low yields (26 and 22%, respectively). This cyclization is
not possible from the configuration present in educts
4c,d . Thus, an at least small amount of other isomers
appears to be present under the reaction conditions
employed. This is supported by AM1 calculations11 of the
energies of possible tautomers of 4c (Supporting Infor-
mation). Due to the presence of an ester group in
Ta ble 2
b
2
4
R1
R2
Ara
Ar1
δ(N-H)
percentc
f
a
b
c
d
e
f
CO2Et
CN
CN
CN
CN
OEt
Ph
OEt
OEt
20
14
72
48
56
36
40
a
a
b
a
a
e
Tol
Tol
Ph
13.35
11.29
11.38
8.36
N(CH2)5
N(CH2)4O
OEt
Tol
Tol
Tosyl
CN
CN
8.73
g
Ar1 ) m-ClC6H4; Tol ) p-MeC6H4; N(CH2)5 ) piperidinyl;
a
N(CH2)4O ) morpholinyl. b 1H NMR (200 MHz, CD2Cl2). 4f:
DMSO-d6. c Isolated yield.
observed for the heterocyclic five-membered ring. Inter-
estingly, investigation of the crystal lattice showed that
for 5a , which was crystallized from toluene, a dimeric
structure was formed. Two hydrogen bonds are located
between the atoms N1 and O1 of two molecules of 5a . A
monomeric structure was observed for 5d . In this case,
the hydrogen bond was located between the heterocyclic
nitrogen atom and the oxygen atom of the solvent (DMF).
For comparison, reactions of bis(imidoyl) chlorides with
carbon nucleophiles without addition of metal salts were
carried out (Scheme 3, Table 2). In these reactions open-
chained rather than C- or N-cyclization products were
obtained. Treatment of sodium diethyl malonate Na[CH-
(CO2Et)2] with bis(m-chlorophenylimidoyl)chloride 2f
gave bis-enamine 4a in low yield.10 Reaction of bis-
(imidoyl)chlorides 2a ,b with sodium benzoyl acetonitrile
and sodium ethyl cyanoacetate at 0 °C afforded bis-
enamines 4b-d (48-72%). Reaction of N-(cyanoacetyl)-
(10) Price, C. C.; Velzen, B. J . Org. Chem. 1946, 11, 6

368 J . Org. Chem., Vol. 64, No. 2, 1999
Wuckelt et al.
Sch em e 4
F igu r e 3. ORTEP plot of 2a -NiBr 2 with the atom numbering
scheme. The thermal ellipsoids of 50% probability are shown
for the non-hydrogen atoms. Selected bond lengths [Å] and
angles [deg]: Ni1-Br1 2.535(3), Ni1-Br2 2.517(3), Ni1-O1
2.127(13), Ni1-O2 2.095(12), C1-N1 1.225(22), C2-N2 1.280-
(22), Ni1-N1 2.088(14), Ni1-N2 2.111(14), C1-Cl1 1.788(18),
C2-Cl2 1.751(19), N1-C10 1.471(22), N2-C20 1.469, C1-C2
1.516(25); Br1-Ni-N1 88.3(4), Br1-Ni-N2 87.0(4), Br1-Ni-
O1 92.2(4), Br1-Ni-O2 94.1(3), O2-Ni-N1 174.0(5), O1-Ni-
N2 97.7(5), C1-C2-Cl2 121.5(13), C1-N1-C10 120.8(15),
Br1-Ni-Br2 173.8(1), O1-Ni-O2 89.2(5), Br2-Ni-N1 86.4-
(4), Br2-Ni-O1 91.7(4), N1-C1-Cl1 126.1(14), N1-C1-Cl1
126.1(14), Ni-N(1)-C10 122.8(10)
trans relationship to the amino group in case of bis-
enamine 4a , condensation via 2-fold attack of the nitro-
gen atoms on the ester groups took place by boiling of
4a in diphenyl ether.10 No cyclization was induced when
diketodiene 4c was treated with Na[N(SiMe3)2].
To elucidate the mechanism of the transition metal
mediated synthesis of 5-ylidenepyrrol-2(5H)-ones 5, the
complexation of transition metals with bis(imidoyl)-
dichlorides 2 was studied (Scheme 4). Treatment of an
ether solution of C2Cl2(NTol)2 (2a ) with cobalt(II) bromide
afforded the novel red cobalt(II) complex 2a -CoBr 2 (90%).
Likewise, reaction of 2a with nickel(II) bromide in THF
gave the red nickel(II) complex 2a -NiBr 2 (77%). Treat-
ment of 2a -CoBr 2 (1 equiv) with sodium ethyl cyanoac-
etate (4 equiv) and Na[N(SiMe3)2] (3 equiv) and sub-
sequent aqueous workup afforded 5-ylidenepyrrol-2(5H)-
one 5d in high yield (85%).
The cobalt atom of complex 2a -CoBr 2 is coordinated
by two bis(imidoyl)chloride molecules, whereas the nickel
atom of complex 2a -NiBr 2 is coordinated by only one bis-
(imidoyl)chloride unit and by two THF molecules. As
shown by the crystal structure of 2a -NiBr 2 (Figure 3),
the coordinated dielectrophile exhibits s-cis configuration
due to chelation of the 1,4-diazadiene system to the
metal. In contrast, the free ligand C2Cl2(NAr)2 has s-trans
geometry.12 The nickel atom exhibits an octahedral
coordination sphere. The bromine atoms are located trans
to each other, and the THF molecules are located cis to
each other. The C1-C2 distance (1.516 Å) and the C-N
distance (1.225 Å) of the imino groups in 2a -NiBr 2 are
similar to those of noncoordinated C2Cl2(NAr)2 2g (Ar )
2,6-bis-isopropylphenyl) (1.495 and 1.239 Å, respectively).
The bond lengths Ni-N of 2a -NiBr 2 (2.088, 2.111 Å) are
increased with respect to those of the known dimeric
complex [(tDAB)NiBr2]2 (2.039, 2.042 Å) and of the
monomeric complex [(tDAB)NiBr2] (1.996, 2.002 Å) (tDAB
) N,N-di-tert-butyldiazabutadiene).13 This effect can be
Sch em e 5a
Reagents and conditions: (i) H+, H2O, 41%. (ii) 1. cat.
a
Na[N(SiMe3)2], THF, -78 °C; 2. H+, H2O, 89%. (iii) 1. 3 equiv of
Na[N(SiMe3)2], THF, -78 °C; 2. H+, H2O, 87%.
explained by the decreasing coordination number of
nickel(II) in this series (from 6 over 5 to 4). The coordina-
tion of C2Cl2(NTol)2 to the metal is only weak and the
ligand is readily replaced by pyridine or TMEDA in
ligand exchange reactions.
Bis-enamine 4c was deprotonated using Na[N(SiMe3)2]
and was reacted with CoBr2‚2THF to form cobalt(II)
complex 7 in 84% yield (Scheme 5). Two molecules each
of 4c and of THF are coordinated to the metal. Hydrolysis
of 7 provided 5-ylidenepyrrol-2(5H)-one 5d in 41% yield.
The yield was increased when catalytic or stoichiometric
amounts of Na[N(SiMe3)2] were added to a THF solution
of 7 at -78 °C before hydrolytic workup, and 5d was
isolated in 89 and 87% yield, respectively.
The aqueous workup of the domino reaction was
replaced by filtration of the reaction mixture through a
layer of Celite (Scheme 6). Crystalization afforded nickel-
(II) complexes 9a ,b. The elemental analyses and mass
spectra of these compounds suggested that structures I
or II are adopted. Deprotonation of 5d using Na[N-
(SiMe3)2] and subsequent treatment with CoBr2‚2THF or
NiBr2‚DME gave stable metal complexes of type II
(Supporting Information). Although the definite structure
of 9a ,b could not be unambigiously determined, the
isolation of these intermediates showed that an excess
of Na[N(SiMe3)2] (as present in this experiment) is
mandatory for the transformation of 7 into 9 in high
(11) The configurations of the isomers of 4c were generated and the
energies were subsequently minimized using the MM+ force field
which is implemented in release 3.0 of HyperChem. MM+ supplements
the standard MM2 parameters (Allinger, N. L. J . Am. Chem. Soc. 1977,
99, 8127). All input geometries were taken from the molecule editor
and optimized using the Polak-Ribiere algorithm. The minima obtained
from the search were further optimized using the AM1 wave function
(Dewar, M. J . S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J . J . P. J . Am.
Chem. Soc. 1985, 107, 3902) and the RHF approximation.
(12) Lindauer, D.; Beckert, R.; Do¨ring, M.; Fehling, P.; Go¨rls, H. J .
Prakt. Chem., 1995, 337, 143.
(13) J ameson, B.; Oswald, H. R.; Beer, H. R. J . Am. Chem. Soc. 1984,
106, 1669.

Synthesis of 5-Ylidenepyrrol-2(5H)-ones
J . Org. Chem., Vol. 64, No. 2, 1999 369
Sch em e 6
structures and â-amino acids. Bis(imidoyl)chlorides 2, bis-
enamines 4, and 5-ylidenepyrrol-2(5H)-ones 5 are readily
coordinated by transition metals, an interesting feature
in view of the development of new ligands for olefin
polymerization catalysis.
Exp er im en ta l Section
Gen er a l. All solvents were dried by standard methods, and
all reactions were carried out under an inert atmosphere.
Petroleum ether (bp 40-70 °C) and ether were distilled prior
to use. The oxalic acid-bis(imidoyl) dichlorides 2 were prepared
by literature procedures.12 NMR spectra were recorded at 200
and 50 MHz (for 1H and13C, respectively), if not quoted
otherwise. For 1H NMR, CDCl3 and CD2Cl2 (TMS as internal
standard), DMSO-d6 (δ ) 2.49), THF-d8 (δ ) 1.73, 3.58), DMF-
d7 (δ ) 2.90, 8.02), and acetone-d6 (δ ) 2.04) were used as
solvents. For 13C NMR, CDCl3 and CD2Cl2 (TMS as internal
standard), DMSO-d6 (δ ) 39.5), THF-d8 (δ ) 25.5, 67.7), DMF-
d7 (δ ) 29.7, 34.8), and acetone-d6 (δ ) 29.8, 206.3) were used
as solvents. The multiplicity of the C atoms was determined
by the DEPT 135 technique and quoted as CH3, CH2, CH, and
C for primary, secondary, tertiary, and quaternary carbon
atoms, respectively. Mass spectra were recorded using the
electron ionization (70 eV) or the chemical ionization method
(CI with water). For preparative scale chromatography, silica
gel (60-200 mesh) was used. Melting points are uncorrected
and elemental analyses were performed at the microanalytical
laboratory of the University of J ena.
X-r a y Diffr a ction Da ta . The intensity data were collected
using graphite-monochromated Mo KR radiation. The crystals
were mounted in a cold nitrogen stream at -90 °C. Data were
corrected for Lorentz and polarization effects, but not for
absorption.17 The structures were solved by direct methods
(SHELXS)18 and refined by full-matrix least-squares tech-
niques against F2 (SHELXL-93).19 The hydrogen atoms were
included at calculated positions with fixed thermal parameters
for 2a -NiBr 2 while the hydrogen atoms of 4c and 5a were
located from the difference Fourier synthesis and refined
isotropically. All non-hydrogen atoms were refined anisotro-
pically. Crystallographic details are listed in Table 3.
Gen er a l P r oced u r e for t h e P r ep a r a t ion of Bis-
en a m in es (4b-f). To a THF solution (20 mL) of the respective
cyanoacetic derivatives or benzoylacetonitrile (10 mmol) was
added 10 mL of NaN(SiMe3)2 (1 M solution in THF) in 25 mL
of THF. After 10 min of stirring at 0 °C, the suspension was
transferred to a THF solution (25 mL) of the respective oxalic
acid-bis(imidoyl) dichloride (2a , 1.5 g; 2b, 1.2 g; 5 mmol) at
-20 °C. The cooling bath was removed, and the reaction
mixture was stirred at 50 °C for 24 h. After cooling to room
temperature, the reaction mixture was poured into an aequous
solution of 300 mL of NH4Cl which was extracted with ether/
THF (1:1). The combined organic layers were dried (Na2SO4)
and filtered and the solvent was removed in vacuo. To the
residue was added 2 mL of methanol. The precipitated product
was washed twice with methanol and was dried in vacuo.
(Z,Z)-1,4-Dicya n o-2,3-d i(p -t olyl)a m in ob u t a d ien e-1,4-
bis(p h en yl k eton e) (4b). Starting with benzoyl acetonitrile
(0.5 g, 3.4 mmol) and 2a (0.5 g, 1.7 mmol), 125 mg of 4b (14%)
was isolated as yellow crystals (mp 308-310 °C). IR (Nujol):
νj 2199 (s) cm-1, 1612 (s), 1591 (s), 1570 (s), 1514 (s), 1494 (m).
1H NMR (CD2Cl2): δ 2.38 (s, 6 H, Tol-CH3), 6.98 (d, J ) 8.4
Hz, 4 H, Ar), 7.20 (d, J ) 8.3 Hz, 4 H, Ar), 7.56 (m, 6 H, Ar),
7.85 (d, J ) 8.0 Hz, 4 H, Ar), 13.35 (s, 2 H, NH). 13C NMR
(CD2Cl2): δC 21.2 (Tol-CH3), 85.6 (C, CCN), 118.8 (C, CN),
123.5, 128.7, 130.6, 132.8, 133.9, 138.5, 139.1 (CH, C, Ar), 159.4
(C, CNHTol), 193.3 (CO). MS (CI, H2O) m/z (%): 523 (22) [M+
+ 1], 416 (26), 261 (4) [M+/2]. Anal. Calcd for C34H26N4O2
(522.6): C, 78.14; H, 5.01; N, 10.72. Found: C, 77.71; H, 5.03;
N, 10.52.
yield. Since no excess of base was present during the
reaction of deprotonated 4c with CoBr2 (Scheme 5)
complex 7 could be isolated. Upon treatment with base
and subsequent hydrolysis this compound could be
converted into 5-ylidenepyrrol-2(5H)-one 5d .
In summary, we have found a transition metal medi-
ated domino reaction which regio- and stereoselectively
afforded 5-ylidenepyrrol-2(5H)-ones 5. The variation of
the amount and the type of the metal salts, the isolation
of intermediates 2-MBr 2, 7, and 9, and their conversion
into 5d suggest that six steps (C-C coupling, complex-
ation, Dieckmann condensation, rearrangement, Dimroth
rearrangement, decomplexation) are involved in the
domino reaction. The regioselectivity is presumably
controlled by the conformational lock of the 3-amino-1-
azadiene ligand by complexation of the nitrogen atoms
which are, thus, not available for intramolecular attack
on the ester groups. A base-catalyzed mechanism or the
simple action of the transition metal salts as a Lewis acid
are less likely. For an effective cyclization, stoichiometric
amounts of the metal and, at least, a catalytic excess of
base are required.
The 5-ylidenepyrrol-2(5H)-one structural unit 5 is
found in a range of biologically important natural prod-
ucts including holomycin,14a pukeleimide A,14b isoampul-
licin,14c and the bile pigment bilirubin.14d Although
synthetic routes to the corresponding 5-ylidenefuran-
2(5H)-ones and 4-ylidenetetronic acids are well docu-
mented,15 only few synthetic studies toward 5-ylidenepyr-
rol-2(5H)-ones 5 have been published.16 The convenient
preparation of 2,3-diamino-1,3-butadienes 4 (which rep-
resent azaanalogues of oxalyldimalonic acid derivatives
1a ) points the way to a novel entry into bis-heterocyclic
(14) (a) Celmer, W. D.; Salomon, J . A. J . Am. Chem. Soc. 1955, 77,
2861. (b) Simmons, C. J .; Marner, F.-J .; Cardellina, J . H., II; Moore,
R. E.; Seff, K. Tetrahedron Lett. 1979, 2003. (c) Abdullaev, N. D.;
Samikov, K.; Antsupova, T. P.; Yagudaev, M. R.; Yunusov, S. Khim.
Prir. Soedin 1987, 5, 692 [Chem. Nat. Compd. (Engl. Transl.) 1987,
23, 576]. (d) Falk, H.; Grubmayr, K.; Herzig, U.; Hofer, O. Tetrahedron
Lett. 1975, 559.
(15) (a) Knight, D. W.; Pattenden, G. J . Chem. Soc., Perkin Trans.
1 1979, 62. (b) Pattenden, G. Fortschr. Chem. Org. Naturst. 1978, 35,
133.
(16) (a) Gill, G. B.; J ames, G. D.; Oates, K. V.; Pattenden, G. J .
Chem. Soc., Perkin Trans. 1 1993, 2567 and the following paper. (b)
Murakami, M.; Hayashi, M.; Ito, Y. J . Org. Chem. 1994, 59, 7910. (c)
Abell, A. D.; Oldham, M. D.; Taylor, J . M. J . Chem. Soc., Perkin Trans.
1 1995, 953.
(17) MOLEN, An Interactive Structure Solution Procedure, Enraf-
Nonius, Delft, The Netherlands, 1990.
(18) Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467-473.
(19) Sheldrick, G. M., University of Go¨ttingen, Germany, 1993.

370 J . Org. Chem., Vol. 64, No. 2, 1999
Wuckelt et al.
5a
Ta ble 3
compd
4c
2a-NiBr2
empirical formula
fw
C
458.5
0.40 × 0.40 × 0.38
yellow prism
triclinic
26H26N4O4
C24H30Br2Cl2N2NiO2
667.9
0.50 × 0.40 × 0.40
red columns
orthorhombic
Pbca
C28H30N2O7
506.5
0.40 × 0.38 × 0.20
yellow prism
monoclinic
P21/c
cryst size [mm3]
cryst color and habit
cryst syst
space group
P1
unit cell dimens [Å, deg]
a ) 10.716(2)
b ) 11.423(2)
c ) 11.799(2)
R ) 89.68(3)
â ) 72.59(3)
γ ) 62.43(3)
1206.4(4)
2
a ) 10.004(2)
b ) 16.443(4)
c ) 33.812(11)
R ) 90
a ) 8.841(1)
b ) 19.805(2)
c ) 14.815(2)
R ) 90
â ) 90
â ) 101.89(1)
γ ) 90
γ ) 90
5562(3)
8
1.595
0.38
2688
vol [Å3]
Z
2538.4(5)
4
1.32
0.96
1072
density (calcd) [g cm-3
]
1.26
0.87
484
µ (Mo KR) [cm-1
F(000)
]
2Θ range for data collection [deg]
reflns collect
2.28, 29.97
7101
1.5, 27
8401
2.35, 29.84
7637
in (h, (k, +l
indep reflns
6800
6108
6898
reflns with Fo > 4σ(Fo)
4983
1881
4672
final R indices
R ) 0.046
wR2 ) 0.118
1.13
R ) 0.0598
wR2 ) 0.076
7.74
R ) 0.047
wR2 ) 0.106
1.22
GOF
largest diff peak [eÅ-3
]
0.49
1.16
0.34
(Z,Z)-1,4-Dicya n o-2,3-d i(p -t olyl)a m in ob u t a d ien e-1,4-
d ica r boxylic Acid Dieth yl Ester (4c). Starting with ethyl
cyanoacetate (1.1 mL, 10 mmol) and 2a (1.5 g, 5 mmol), 3.3 g
of 4c (72%) was isolated as yellow crystals (mp 196-199 °C).
IR (Nujol): νj 3322 (m) cm-1, 2213 (s), 1670 (s), 1595 (s). 1H
NMR (CD2Cl2): δ 1.35 (t, J ) 7.2 Hz, 6 H, CH2CH3), 2.34 (s, 6
H, Tol-CH3), 4.27 (m, J ) 7.2 Hz, 4 H, CH2CH3), 6.87, 7.13 (d,
J ) 8.5 Hz, 8 H, Tol), 11.29 (s, 2 H, NH). 13C NMR (CD2Cl2):
δC 14.4 (CH2CH3), 21.1 (Tol-CH3), 62.3 (CH2CH3), 77.4 (C,
CCN), 116.0 (C, CN), 123.2, 130.4 (CH, Tol), 134.0 (C, Tol-C
to C), 138.4 (C, Tol-C to N), 157.9 (C, CNHTol), 167.2 (CO).
MS (EI) m/z (%): 458 (19) [M+], 385 (57), 339 (100), 229 [M+/
2]. Anal. Calcd for C26H26N4O4 (458.5): C, 68.11; H, 5.72; N,
12.22. Found: C, 68.52; H, 5.79; N, 11.97.
(Z,Z)-1,4-Dicya n o-2,3-d i(p h en yl)a m in ob u t a d ien e-1,4-
d ica r boxylic Acid Dieth yl Ester (4d ). Starting with ethyl
cyanoacetate (1.1 mL, 10 mmol) and 2b (1.35 g, 5 mmol), 2.1
g of 4d (48%) was isolated as yellow crystals (mp 207 °C). IR
(Nujol): νj 3292 (w) cm-1, 3183 (m), 2213 (s), 1670 (s), 1593
(s), 1580 (s), 1497 (m). 1H NMR (CD2Cl2): δ 1.32 (t, J ) 6.9
Hz, 6 H, CH2CH3), 4.27 (m, J ) 6.9 Hz, 4 H, CH2CH3), 6.97
(m, 4 H, Ph), 7.32 (m, 6 H, Ph), 11.38 (s, 2 H, NH). 13C NMR
(CD2Cl2): δC 14.2 (CH2CH3), 62.3 (CH2CH3), 77.8 (C, CCN),
115.8 (C, CN), 123.1, 127.9, 129.8 (CH, Ph), 136.2 (C, Ph), 157.4
(C, CNHPh), 167.5 (CO). MS (CI, H2O) m/z (%): 431 (100) [M+
+ 1], 385 (10), 357 (16). Anal. Calcd for C24H22N4O4 (430.46):
C, 66.97; H, 5.15; N, 13.02. Found: C, 67.17; H, 5.08; N, 13.07.
(Z,Z)-1,4-Dicya n o-2,3-d i(p -t olyl)a m in ob u t a d ien e-1,4-
d ica r b oxylic Acid P ip er id id e (4e). Starting with (cy-
anoacetyl)piperidine (0.76 g, 5 mmol) and 2a (0.76 g, 2.5
mmol), 1.5 g of 4e (56%) was isolated as a slightly yellow solid
(mp 285-287 °C). IR (Nujol): νj 3297 (s) cm-1, 1678 (m). 1H
NMR (CD2Cl2): δ 1.28 (m, 12 H, CH2), 2.39 (s, 6 H, Tol-CH3),
2.70, 3.31, 3.74 (m, 20 H, NCH2), 7.24 (m, 8 H, Tol), 8.36 (s, 2
H, NH). 13C NMR (CD2Cl2): δC 21.2 (Tol-CH3), 24.6, 25.5, 26.5,
42.8, 48.2 (CH2), 96.5 (C, CCN), 126.5, 129.7 (CH, Tol), 137.9
(C, Tol-C to C), 145.2 (C, Tol-C to N), 161.7 (C, CNHTol), 165.8
(CO). MS (CI, H2O) m/z (%): 537 (3) [M+ + 1], 452 (8), 268 (3)
[M+/2], 147 (100). Anal. Calcd for C32H36N6O2 (536.68): C,
71.62; H, 6.76; N, 15.66. Found: C, 71.29; H, 6.88; N, 15.41.
(Z,Z)-1,4-Dicya n o-2,3-d i(p -t olyl)a m in ob u t a d ien e-1,4-
d ica r boxylic Acid Mor p h olid e (4f). Starting with (cy-
anoacetyl)morpholine (1.00 g, 6.48 mmol) and 2a (0.99 g, 3.24
mmol), 1.26 g of 4f (36%) was isolated as a slightly yellow solid
(mp 307-308 °C). IR (Nujol): νj 3475 (m) cm-1, 3445 (s), 3276
(s), 1676 (w), 1635 (s), 1590 (s), 1579 (s), 1515 (m). 1H NMR
(DMSO-d6): δ 2.34 (s, 6 H, Tol-CH3), 3.28, 3.32 (m, 16 H, CH2),
7.24 (m, 8 H, Tol), 8.73 (s, 2 H, NH). MS (CI, H2O) m/z (%):
541 (12) [M+ + 1], 454 (2), 88 (100). Anal. Calcd for C30H32N6O4
(540.62): C, 66.65; H, 5.97; N, 15.55. Found: C, 66.41. H, 6.05;
N, 15.71.
Con ver sion of 4c a n d 4d in to 5d a n d 5e, Resp ectively.
A toluene solution (30 mL) of diketodienes 4c or 4d (0.5 g)
was refluxed for 12 h. The solution became red after 6-8 h,
and a red solid precipitated which was filtered, washed two
times with hot toluene, and dried. The product was recrystal-
lized from acetone to give 0.12 g (26%) of 5d or 0.10 g (22%) of
5e.
Gen er a l P r oced u r e for th e P r ep a r a tion of 5-Ylid en ep yr -
r ol-2(5H)-on es (5a -f). To a THF solution (20 mL) of diethyl
malonate (0.88 mL, 8 mmol) or ethyl cyanoacetate (8 mmol)
was added 14 mL of NaN(SiMe3)2 (1 M solution in THF) in 25
mL of THF. After 10 min of stirring at 0 °C, the suspension
formed was transferred to a (green) THF solution (30 mL) of
CoBr2‚2THF (0.72 g, 2 mmol) and the respective oxalic acid
bis(imidoyl) dichloride (4 mmol) at -78 °C. After 12 h of
stirring at 20 °C, the deep red solution was added to 250 mL
of saturated aqueous solution of NH4Cl. The organic layer was
separated and dried (Na2SO4), and the solution was concen-
trated with a rotary evaporator. Purification was effected as
indicated.
(E)-[1-(p-Tolyl)-3-[(p-tolyl)am in o]-4-car boxyeth yl-2-oxo-
p yr r ol-5-ylid en e]d ica r b oxylic Acid Diet h yl E st er (5a ).
Starting with diethyl malonate (8 mmol) and 2a (1.22 g, 4
mmol), 556 mg of 5a (54%) was isolated by column chroma-
tography (silica gel, toluene/acetone ) 10:1) as slightly yellow
crystals (mp 128-130 °C). IR (Nujol): νj 3264 (s) cm-1, 1738
1
(s), 1711 (s), 1705 (s), 1635 (s). H NMR (acetone-d6): δ 0.97,
1.02, 1.19 (t, J ) 7.2 Hz, 9 H, CH2CH3), 2.29, 2.32 (s, 6 H,
Tol-CH3), 3.38, 3.84, 4.08 (m, 6 H, CH2CH3), 7.05-7.25 (m, 8
H, Tol), 8.86 (s, 1 H, NH). 13C NMR (acetone-d6): δC 13.8, 13.9,
14.2 (CH2CH3), 20.9, 21.4 (Tol-CH3), 61.4, 61.5, 61.6 (CH2CH3),
103.1 (C, C-6), 107.3 (C, C-4), 124.3, 126.0, 128.9, 129.1, 129.6,
129.9 (C, CH, Tol), 133.4 (C, C-3), 136.2, 138.9 (C, Tol-C to
N), 149.4 (C, C-5), 164.4, 164.5, 165.3, 166.0 (C, C-2, CO). MS
(EI) m/z (%): 506 (15) [M+], 387 (67), 341 (100). Anal. Calcd
for C28H30N2O7 (506.5): C, 66.39; H, 5.97; N, 5.53. Found: C,
66.32; H, 6.13; N, 5.67.
(E)-[1-(P h en yl)-3-(p h en yla m in o)-4-(ca r b oxyet h yl)-2-
oxopyr r ol-5-yliden e]dicar boxylic Acid Dieth yl Ester (5b).
Starting with diethyl malonate (8 mmol) and 2b (1.08 g, 4
mmol), 1.17 g of 5b (61%) was isolated by column chromatog-

Synthesis of 5-Ylidenepyrrol-2(5H)-ones
J . Org. Chem., Vol. 64, No. 2, 1999 371
raphy (silica gel, toluene/acetone ) 10:1) as slightly yellow
crystals (mp 139-141 °C). IR (Nujol): νj 3264 (s) cm-1, 1738
(s), 1711 (s), 1705 (s), 1635 (s). 1H NMR (CD2Cl2): δ 1.05, 1.20,
1.33 (t, J ) 7 Hz, 9 H, CH2CH3), 3.68, 4.18 (m, 6 H, CH2CH3),
7.10-7.45 (m, 10 H, Ph), 8.58 (s, 1 H, NH). 13C NMR (CD2-
Cl2): δC 13.9, 14.2, 14.8 (CH2CH3), 56.6, 58.7, 60.1 (CH2CH3),
94.4 (C, C-6), 103.1 (C, C-4), 123.6, 125.5, 127.3, 127.8, 129.0,
129.6 (CH, Ph), 135.3 (C, C-3), 139.3, 139.4 (C, Ph-C to N),
146.3 (C, C-5), 163.9, 164.6, 165.7, 166.2 (C, C-2, CO). MS (EI)
m/z (%): 506 (15) [M+], 387 (67), 341 (100). Anal. Calcd for
Calcd for C24H20N4O3 (412.4): C, 69.89; H, 4.89; N, 13.58.
Found: C, 70.18; H, 5.08; N, 13.44.
Gen er a l P r oced u r e for th e Hyd r olysis of 5a ,d . 5a or
5d was stirred for 10 min at 20 °C in an aqueous solution of
KOH (30 mL, 1 M). The deep red solution was extracted with
an aqueous solution of KOH (1 M) and with water. The
aqueous layer was filtered, and the filtrate was neutralized
by addition of hydrochloric acid (2 M solution). This precipi-
tated the product which was filtered, washed (ether), and dried
in vacuo.
C
28H30N2O7 (506.5): C, 66.39; H, 5.97; N, 5.53. Found: C,
(E)-[1-(p -Tolyl)-3-[(p -t olyl)a m in o]-4-(ca r boxyet h yl)-2-
oxop yr r ol-5-ylid en e]d ica r boxylic Acid An h yd r id e (6a ).
Starting with 5a (0.5 g, 1 mmol), 0.34 g (72%) of 6a was
isolated as slightly yellow crystals (mp 240 °C). IR (Nujol): νj
3239 (m) cm-1, 1734 (s), 1662 (s), 1636 (s). 1H NMR (DMF-d7):
δ 1.04, 1.15 (t, J ) 7 Hz, 6 H, CH2CH3), 2.30, 2.35 (s, 6 H,
Tol-CH3), 3.38 (q, J ) 7 Hz, 4 H, CH2CH3), 7.10-7.30 (m, 8 H,
Tol), 10.18 (s, 1 H, NH). 13C NMR (DMF-d7): δC 13.9 (CH2CH3),
20.7, 21.0 (Tol-CH3), 65.8 (CH2CH3), 98.8 (C, C-6), 102.1 (C,
C-4), 124.9, 125.0, 129.7, 130.0 (C, CH, Tol), 135.6 (C, C-3),
137.4, 139.5 (C, Tol-C to N), 151.8 (C, C-5), 160.1, 163.6, 165.9,
168.3 (C, C-2, CO). MS (EI) m/z (%): 478 (46) [M+], 386 (100),
315 (14). Anal. Calcd for C26H26N2O7 (478.5): C, 65.26; H, 5.48;
N, 5.85. Found: C, 65.52; H, 5.18; N, 5.71.
66.32; H, 6.13; N, 5.67.
(E)-[1-(p-Nitr oph en yl)-3-[(p-n itr oph en yl)am in o]-4-(car -
boxyeth yl)-2-oxop yr r ol-5-ylid en e]d ica r boxylic Acid Di-
eth yl Ester (5c). Starting with diethyl malonate (8 mmol)
and p-bis[(p-nitrophenyl)imidoyl] chloride (1.47 g, 4 mmol),
1.27 g of 5c (56%) was isolated by column chromatography
(silica gel, toluene/acetone ) 10:1) as slightly yellow crystals
(mp 179-181 °C). IR (Nujol): νj 3264 (s) cm-1, 1738 (s), 1711
1
(s), 1705 (s), 1635 (s). H NMR (CD2Cl2): δ 1.04, 1.21, 1.36 (t,
J ) 7 Hz, 9 H, CH2CH3), 3.70, 4.21 (m, 6 H, CH2CH3), 7.22
(m, 2 H, Ar), 7.70 (m, 2 H, Ar), 8.22 (m, 4 H, Ar), 8.84 (s, 1 H,
NH). 13C NMR (CD2Cl2): δC 13.9, 14.1, 14.3 (CH2CH3), 61.6,
62.0, 62.2 (CH2CH3), 94.7 (C, C-6), 108.4 (C, C-4), 122.6, 124.4,
124.7, 126.7 (CH, Ar), 141.3 (C, C-3), 144.5, 144.8, 144.9, 146.3
(C, Ar-C to N, C-5), 163.4, 164.0, 165.3, 165.9 (C, C-2, CO).
MS (EI) m/z (%): 506 (15) [M+], 387 (67), 341 (100). Anal. Calcd
for C28H30N2O7 (506.5): C, 66.39; H, 5.97; N, 5.53. Found: C,
66.32; H, 6.13; N, 5.67.
(E)-[1-(p-Tolyl)-3-[(p-tolyl)a m in o]-4-cya n o-2-oxop yr r ol-
5-ylid en e]cya n oa cetic Acid (6b). Starting with 5d (0.24 g,
0.58 mmol), 190 mg (70%) of 6b‚2H2O was isolated as slightly
yellow crystals (mp 276-280 °C). IR (Nujol): νj 3304 (m) cm-1
,
1
2230 (m), 2213 (m), 1722 (m), 1671 (s). H NMR (DMF-d7): δ
2.32, 2.33 (s, 6 H, Tol-CH3), 4.12 (br, 4 H, H2O), 7.30 (m, 8 H,
Tol), 9.67 (s, 1 H, NH). 13C NMR (DMF-d7): δC 20.7 (Tol-CH3),
81.3, 81.8 (C, C-6, C-4), 113.9, 114.6 (C, CN), 126.2, 128.6,
129.8, 134.5 (C, CH, Tol), 135.7, 137.1, 139.7 (C, C-3, Tol-C to
N), 156.4 (C, C-5), 160.2, 161.8 (C, C-2, CO). MS (EI) m/z (%):
384 (7) [M+], 340 (88), 44 (100). Anal. Calcd for C22H20N4O5
(420.4): C, 62.85; H, 4.79; N, 13.33. Found: C, 62.85; H, 4.62;
N, 12.56.
(E)-[1-(p-Tolyl)-3-[(p-tolyl)a m in o]-4-cya n o-2-oxop yr r ol-
5-ylid en e]cya n oa cetic Acid Eth yl Ester (5d ). Starting with
ethyl cyanoacetate (0.88 mL, 8 mmol) and 2a (1.22 g, 4 mmol),
1.20 g of 5d (71%) was isolated, by addition of a few drops of
ether to 1 mL of a THF solution of the product, as slightly red
crystals (mp 279 °C (dec)). IR (Nujol): νj 3247 (s) cm-1, 2220
(m), 2204 (m), 1737 (s), 1706 (s), 1641 (s). 1H NMR (DMSO-
d6): δ 1.14 (t, 3 H, CH2CH3), 2.30, 2.33 (s, 6 H, Tol-CH3), 4.15
(q, 2 H, CH2CH3), 7.35 (m, 8 H, Tol), 11.34 (s, 1 H, NH). 13C
NMR (DMSO-d6): δC 13.6 (CH2CH3), 20.9, 21.0 (Tol-CH3), 61.7
(CH2CH3), 75.4 (C, C-6), 79.8 (C, C-4), 112.4, 120.3 (C, CN),
122.8, 124.3, 129.1, 129.6, 130.0, 130.1 (C, CH, Tol), 133.6 (C,
C-3), 133.1, 136.8 (C, Tol-C to N), 146.6 (C, C-5), 158.0, 162.7
(C, C-2, CO). MS (EI) m/z (%): 412 (35) [M+], 385 (17), 339
(100). Anal. Calcd for C24H20N4O3 (412.4): C, 69.89; H, 4.89;
N, 13.58. Found: C, 70.18; H, 5.08; N, 13.44.
P r oced u r e for th e P r ep a r a tion of Coba lt Com p lex 2a -
CoBr 2. CoBr2‚THF (1.29 g, 3.55 mmol) was suspended in 80
mL of diethyl ether, and 2.17 g (7.1 mmol) of C2Cl2(NTol)2 was
added. A red microcrystaline solid immediately precipitated
which was filtered after 1 h of stirring at 0 °C giving 2.6 g of
2a -CoBr 2 (90%). IR (Nujol): νj 1660 cm-1. Anal. Calcd for
C
32H28Br2Cl2N4Co (829.17): Co, 7.1. Found: Co, 7.3.
P r oced u r e for th e P r ep a r a tion of Nick el Com p lex 2a -
(E)-[1-P h en yl-3-(p h en yla m in o)-4-cya n o-2-oxop yr r ol-5-
ylid en e]cya n oa cetic Acid Eth yl Ester (5e). Starting with
ethyl cyanoacetate (0.88 mL, 8 mmol) and 2b (1.08 g, 4 mmol),
1.14 g of 5e (74%) was isolated, by addition of a few drops of
ether to 1 mL of a THF solution of the product, as slightly red
NiBr 2. NiBr2 (8.9 g, 40.7 mmol) was suspended in 100 mL of
THF, and 13.6 g (44.8 mmol) of C2Cl2(NTol)2 was added. The
suspension was stirred for 3 d at 20 °C. The deep red crystals
which precipitated were filtered giving 16.0 g of 2a-CoBr2
(77%). IR (Nujol): νj 1660 cm-1, 1704, 1752. Anal. Calcd for
crystals (mp 269-271 °C (dec)). IR (Nujol): νj 3247 (s) cm-1
,
2220 (m), 2204 (m), 1737 (s), 1706 (s), 1641 (s). 1H NMR
(DMSO-d6): δ 1.18 (br, 3 H, CH2CH3), 4.13 (br, 2 H, CH2CH3),
7.30-7.50 (m, 10 H, Ph), 11.44 (s, 1 H, NH). 13C NMR (DMSO-
d6): δC 13.6 (CH2CH3), 61.7 (CH2CH3), 75.8 (C, C-6), 79.9 (C,
C-4), 111.4, 113.5 (C, CN), 124.5, 127.3, 128.6, 129.1 (CH, Ph),
132.5 (C, C-3), 135.7 (C, Ph-C to N), 146.8 (C, C-5), 161.8, 162.7
(C, C-2, CO). MS (EI) m/z (%): 412 (35) [M+], 385 (17), 339
(100). Anal. Calcd for C24H20N4O3 (412.4): C, 69.89; H, 4.89;
N, 13.58. Found: C, 70.18; H, 5.08; N, 13.44.
C
24H30Br2Cl2N2NiO2 (667.9): Ni, 9.2. Found: Ni, 9.5.
P r oced u r e for th e Con ver sion of 2a -CoBr 2 in to 5d . To
a THF solution (20 mL) of R-cyanoacetic acid ethyl ester (0.88
mL, 8 mmol) was added 14 mL of NaN(SiMe3)2 (1 M solution
in THF) in 25 mL of THF. After 10 min of stirring at 0 °C, the
suspension formed was transferred to a THF solution (30 mL)
of 2a -CoBr 2 (2 mmol) at -78 °C. After 12 h stirring at 20 °C,
the deep red solution was added to 250 mL of saturated
aequous solution of NH4Cl. The organic layer was separated
and dried (Na2SO4), and the solution was concentrated using
a rotary evaporator to give 5d (85%) by addition of a few drops
of ether to 1 mL of a THF solution of the crude product.
P r ep a r a tion of Coba lt(II) Com p lex (7). CoBr2‚2THF (0.6
g, 1.66 mmol) and 1.52 g (3.31 mmol) of 4c were dissolved in
50 mL of THF at 20 °C, and 3.31 mL of NaN(SiMe3)2 (1.0 M
solution in THF) was added. The solution immediately changed
to deep red, and the solution was stirred for 1 h. NaBr was
removed by filtration (Celite), and the filtrate was concentrated
in vacuo. Ether (50 mL) was added slowly which resulted in
precipitation of cobalt(II) complex 7‚2THF as a deep red solid
(1.55 g, 84%, referred to CoBr2‚2THF). IR (Nujol): νj 3250 (m)
cm-1, 2208 (m), 2205 (m), 1738 (s), 1707 (s), 1667 (s), 1642 (s),
1608 (s), 1560 (s), 1538 (s), 1513 (s). MS (negative CI, H2O)
m/z (%): 973 [M+ - 1 - 2THF] (1), 412 (100). Anal. Calcd for
(E)-[1-(p-Meth oxyph en yl)-3-[(p-m eth oxyph en yl)am in o]-
4-cya n o-2-oxop yr r ol-5-ylid en e]cya n oa cetic Acid Eth yl
Ester (5f): Starting with ethyl cyanoacetate (0.88 mL, 8 mmol)
and bis[(p-methoxyphenyl)imidoyl] chloride (1.35 g, 4 mmol),
1.17 g of 5f (66%) was isolated, by addition of a few drops of
ether to 1 mL of a THF solution of the product, as slightly red
crystals (mp 256-258 °C (dec)). IR (Nujol): νj 3247 (s) cm-1
,
2220 (m), 2204 (m), 1737 (s), 1706 (s), 1641 (s). 1H NMR
(DMSO-d6): δ 1.16 (t, 3 H, CH2CH3), 3.77, 3.79 (s, 6 H, OCH3),
4.00 (q, 2 H, CH2CH3), 7.00 (m, 4 H, Ar), 7.28 (m, 4 H, Ar),
11.31 (br, 1 H, NH). 13C NMR (DMSO-d6): δC 13.7 (CH2CH3),
55.3, 55.4 (OCH3), 61.5 (CH2CH3), 74.6 (C, weak, C-6), 111.9
(C, CN), 113.8, 114.3, 125.9, 129.4, 130.2 (CH, C, Ar, C-3),
147.2 (C, C-5), 158.2, 159.9, 162.2, 162.8 (C, Ar-C to O, C-2,
CO). MS (EI) m/z (%): 412 (35) [M+], 385 (17), 339 (100). Anal.

372 J . Org. Chem., Vol. 64, No. 2, 1999
Wuckelt et al.
C60H68N8O10Co (1118.2): C, 64.45; H, 5.95; N, 10.02; Co, 5.27.
Found: C, 63.95; H, 5.32; N, 10.47; Co, 4.99.
(Nujol): νj 2200 (s) cm-1, 1687 (s), 1612 (s), 1592 (s), 1520 (s).
MS (negative CI, H2O) m/z (%): 824 [M+ - 1 - 2THF] (1),
519 (5), 412 (100). Anal. Calcd for C52H46N8O8Ni (969.68): C,
64.41; H, 4.78; N, 11.56; Ni, 6.05. Found: C, 64.12; H, 4.93,
N, 11.27.
Hyd r olysis of Coba lt(II) Com p lex (7). The complex 7
(0.41 g, 0.37 mmol) was dissolved in THF (25 mL), Na[N-
(SiMe3)2] (1.10 mmol) in THF was added at -78 °C, and the
solution was stirred for 1 h at 20 °C. The solution was poured
into an aqueous solution (1.0 M) of NH4Cl which was then
extracted with THF/ether (1:1). The organic layers were
combined, dried (Na2SO4), and filtered, and the solvent was
removed in vacuo. To the residue was added ether (2 mL)
which resulted in precipitation of a solid which was filtered
and washed (ether), to give 0.27 g (87%) of 5d .
P r ep a r a tion of Coba lt(II) Com p lexes (9a ,b). To a THF
solution (20 mL) of ethyl cyanoacetate or diethyl malonate (8
mmol) was added 14 mL of NaN(SiMe3)2 (1 M solution in THF)
in 25 mL of THF. After 10 min stirring at 0 °C, the suspension
formed was transferred to a THF solution (30 mL) of
NiBr2‚DME (2 mmol) and of the respective oxalic acid bis-
(imidoyl) dichloride (4 mmol) at -78 °C. After 12 h of stirring
at 20 °C, the deep red solution was filtered (Celite) and the
filtrate was concentrated in vacuo to ca. 10 mL without
heating. Ether (20-30 mL) was added slowly which resulted
in precipitation of metal complexes 9a ,b as deep red oils which
solidified on standing for 3 d. The solids were filtered, washed
with ether, and dried in vacuo.
Nick el(II) Com p lex (9b). Starting with NiBr2‚DME (0.16
g, 0.52 mmol), 0.24 g of 9b‚2THF (42%) was isolated. IR
(Nujol): νj 2198 (s) cm-1, 1686 (s), 1609 (s), 1516 (s), 1502 (s).
- MS (Negative CI, H2O) m/z (%): 944 [M+ - 1 - 2THF] (2),
519 (4), 444 (100).
Ack n ow led gm en t. P.L. thanks Professor Dr. A. de
Meijere for his support and the Fonds der Chemischen
Industrie e. V. for the award of a Liebig-fellowship.
Su p p or tin g In for m a tion Ava ila ble: Details of the com-
plexation of 5d with transition metals, of the AM1-calculations
of isomers of 4c, and of the structure determination for 4c,
5a , and 2a -NiBr 2 including atomic coordinates, H-atom coor-
dinates, bond distances, and bond angles (23 pages). This
material is contained in libraries on microfiche, immediately
follows this article in the microfilm version of the journal, and
can be ordered from the ACS; see any current masthead page
for ordering information.
Nick el(II) Com p lex (9a ). Starting with NiBr2‚DME (0.42
g, 1.36 mmol), 0.73 g of 9a ‚2THF (55%) was isolated. IR
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