Synthesis, crystal structures, and reactions of 2- oxomalonylbis(arylimidoyl) chlorides and hydroxymethane tris(arylimidoyl) chlorides

Article abstract of DOI:10.1071/CH04263

The 2-oxomalonylbis(arylimidoyl) chlorides [C₆H ₃(R₂-2,6)N=CC1]₂CO (R = Me, 3a; Prⁱ, 3b; H, 3c) were synthesized from C₆H₃(R ₂-2,6)NHCHO and an excess of (COCl₂

Full text of DOI:10.1071/CH04263

Full Paper
CSIRO PUBLISHING
Aust. J. Chem. 2005, 58, 522–530
www.publish.csiro.au/journals/ajc
Synthesis, Crystal Structures, and Reactions of 2-Oxomalonyl-
bis(arylimidoyl) Chlorides and Hydroxymethane
Tris(arylimidoyl) Chlorides
Richard J. Bowen,A,B Judy Caddy,A,B Mabel E. Coyanis,A Manuel A. Fernandes,A
Marcus Layh,A,C Linda Z. Linganiso,A Winny K. Maboya,A and Bernard OmondiA
A Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag 3,
Wits Johannesburg 2050, South Africa.
B Project AuTEK, Mintek, Private Bag X 3015, Randburg 2125, South Africa.
C Corresponding author. Email: marcus@aurum.wits.ac.za
The 2-oxomalonylbis(arylimidoyl) chlorides [C6H3(R2-2,6)N CCl]2CO (R = Me, 3a; Pri, 3b; H, 3c) were syn-
thesized from C6H3(R2-2,6)NHCHO and an excess of (COCl2)3 and their reaction with various nucleophiles was
studied. Successive hydrolysis of 3a led to the formation of [C6H3(Me2-2,6)N CCl]3COH 4a and [C6H3(Me2-
2,6)NHCO]3COH 5a, while treatment of 3a with HAuCl4(H2O)x gave {[C6H3(Me2-2,6)N(H) CCl][C6H3(Me2-2,
6)NHCO]2COH}AuCl4 6a. All compounds were fully characterized by microanalysis, NMR spectroscopy, mass
spectrometry, and, in the case of 3a, 4a, 5a, and 6a, by X-ray crystallography.
Manuscript received: 6 November 2004.
Final version: 25 March 2005.
Introduction
used in the synthesis of nitrogen-containing heterocycles,[10]
in palladium-mediated cross-coupling reactions,[11] as
masked acyllithium intermediates,[12] and as precursors for
imidoyl radicals.[13]
The use of formamides to affect a variety of transformations
has been investigated over a broad spectrum. Formamides
have been used for the introduction of a carbamoyl group
by the use of the radicals H2NC•O or Me2NC•O generated
from formamide or dimethylformamide and H2SO4, H2O2,
and FeSO4 or other oxidants.[1] Condensation reactions of
aldehydes and ketones with formamides, the Knoevenagel
reaction, have been carried out to prepare a variety of
unsaturated systems.[2] The use of formamides in conver-
sions has been widely explored, varying from the conver-
sion of organometallic compounds into amides,[3] amines,
and aldehydes in the Bouveault reaction,[4] to the reduc-
tive alkylation of ammonia and amines in the Leuckart
reaction.[5] In addition to their use in promoting conver-
sions, they in turn can be converted into isocyanides by
the elimination of water from N-alkyl/aryl formamides
with phosgene and a tertiary amine.[6] The application of
formamides in formylation reactions include the formyla-
tion of olefins[7] and aromatic rings.[8] The reaction with
disubstituted formamides and phosphorus oxytrichloride or
phosgene, the Vilsmeier–Haack reaction, is the most com-
mon method for the formylation of aromatic rings.[9] As
a new application, this paper describes the synthesis of 2-
oxomalonylbis(arylimidoyl) chlorides from arylformamides
and an excess of phosgene and their consecutive conver-
sion into hydroxymethane tris(arylimidoyl) chlorides and
tris(arylformamides). Imidoylchlorideshavepreviouslybeen
Results and Discussion
Synthesis
The phosgene method[6b] for the synthesis of arylisocyanides
from aryl formamides and phosgene (or a phosgene equiva-
lent) has previously been shown to be one of the most versatile
and high yielding methods for this class of compounds. The
accidental use of a large excess of three molar equivalents of
phosgene while attempting to synthesize C6H3(Me2-2,6)NC
2a from C6H3(Me2-2,6)NHCHO 1a led unexpectedly to the
formation of the 2-oxomalonylbis(imidoyl) chloride deriva-
tive 3a in high yield [(i) in Scheme 1].
The phenyl analogue 3c had been previously synthesized
from the reaction of PhNC 2b and phosgene [(ii) in Scheme 1]
and characterized by microanalysis.[14] No further reports on
3c or related compounds were, however, discovered in the
literature. It was, therefore, decided to study the viability
of reaction (i) for a range of substituted aryl formamides.
It was found that the 2-oxomalonylbis(imidoyl) chlorides 3
were obtained in high yields for R = Me (3a), Pri (3b), and
H (3c), while the target product was identified (but not iso-
lated) by NMR spectroscopy as one of the major components
in the case of C6H2(Me3-2,4,5)NHCHO. For C6H3(Cl2-
2,6)NHCHO, only an unidentifiable mixture of products was
© CSIRO 2005
10.1071/CH04263
0004-9425/05/070522

Studies of 2-Oxomalonylbis(arylimidoyl) Chlorides
523
obtained. It was further discovered (for R = Me) that the one-
pot synthesis from the formamide 1a [(i) in Scheme 1] gave
3a in higher purity and yield than using the isocyanide 2a
as a starting material [(ii) in Scheme 1]. Attempts to replace
the chlorine atoms in 3a with a variety of nucleophiles such
as S2−, CH3O−, H2NC(S)NH2, LiN(SiMe3)2, PhNH2, or
PhNHNH2 were not successful and led to decomposition of
the starting material.
Treatment of 3c with an excess of water in the absence
of a solvent and recrystallization of the crude product from
ethanol gave the previously described (PhNHCO)2C(OH)
OEt[14] [(iii)inScheme1]in67%yield, while3a decomposed
quantitativelyto1a [(iv)inScheme1]underthesamereaction
conditions. When the addition of water was, however, carried
out slowly by regularly exposing a solution of 3a in benzene
to moist air over two weeks, the 2-oxomalonylbis(imidoyl)
chloride was converted in high yield, as shown in Scheme 2,
into the hydroxymethane derivative 4a [(v) in Scheme 1].
Further hydrolysis of 4a with wet DMSO (dimethyl sulfox-
ide) led to the formation of compound 5a [(vi) in Scheme 1],
while treatment of 4a with an excess of water gave 5a and,
as a side product, considerable quantities of the formamide
1a [(vii) in Scheme 1]. The reaction mechanism for the for-
mation of 4a is not fully understood but it is likely to involve
the addition of isocyanide 2a, generated by hydrolysis of 3a,
into the electron-deficient carbonyl group of compound 3a.
Attempts to use 3a or 4a as bidentate or tridentate electron
donor ligands for the coordination of transition metal ions
(3a + NiCl2, 4a + PdCl2, 4a + CuI), were not successful and
led to therecoveryof thestartingmaterials, therebyindicating
the low basic character of 3a and 4a. The reaction of the
strong Brønsted acid HAuCl4(H2O)x with 4a in CH2Cl2 led,
OH
O
C
Ar
N
C
2 Ar
N
C
C ꢀ CO2
ꢀ H2O
3
Cl
3a
3
Cl
2
4a
Ar ꢁ C6H3(Me2-2,6)
Scheme 2.
R
1a, R ꢁ Me
1b, R ꢁ Pri
NHCHO
1c, R ꢁ H
1/3 (COCl2)3
R
R
NC
(iv) H2O, R ꢁ Me (i) 0.83 (COCl2)3
2a, R ꢁ Me
2b, R ꢁ H (ref. 10)
(ii)
R
R
R
R
R
O
C
1/6 (COCl2)3
N
C
C
N
Cl
Cl
1) H2O, R ꢁ H
2) EtOH
(iii)
3a, R ꢁ Me, 76% (X-ray)
3b, R ꢁ Pri, 86%
R
R
H
N
OH
C
3c, R ꢁ H, 67% (ref. 10)
C
O
OEt
C6H6/moisture
(v)
R ꢁ Me, Pri
2
67% (ref. 10)
R
OH
(vii) H2O
N
C
C
5a ꢀ1a
Cl
R
3
HAuCl4(H2O)x
R ꢁ Me
4a, R ꢁ Me, 80% (X-ray)
4b, R ꢁ Pri
(viii)
DMSO, H2O
(vi)
Me
Me
Me
R ꢁ Me
H
H
Nꢀ
OH
C
C
N
C
Me
O
Cl
H
N
OH
Me
2
AuCl4ꢂ
C
O
C
Me
6a, 96% (X-ray)
3
5a, 95% (X-ray)
Scheme 1.

524
R. J. Bowen et al.
in contrast, to the organic salt 6a [(viii) in Scheme 1], by
partial hydrolysis of the imidoyl chloride groups in 4a.
Compounds 3 are yellow, hydrocarbon-soluble, air- and
moisture-sensitive solids (3a, 3b) or liquids (3c), although
a rapid aqueous workup was found not to reduce the yield
in the case of 3a and 3b. A powdered sample of 3a was
found to slowly decompose in moist air into a mixture of
4a and two unidentified products. Solutions of 3a in closed
NMR tubes in C6D6 or CDCl3 led to the formation of 4a (see
Scheme 1) or a mixture of 4a, 1a, and one additional product,
respectively. Similarly, a solution of 3b in C6D6 in an NMR
tube led to the formation of 4b and smaller quantities of
unidentified products.
Solid-State Structures of Complexes 3a, 4a, 5a, and 6a
The molecular structure of compound 3a with an atom-
labelling scheme is shown in Fig. 1, and selected bond
distances are in Table 1. The molecule lies on a C2-axis
that passes through the atoms Cl and O1 and it is twisted
in such a way as to minimize steric interactions [torsion
angles Cl1 C2 C2ꢀ C1ꢀ 99.7◦; Cl1 C2 N1 C11 0.4(4)◦,
angle between idealized planes of aromatic rings 75.11 (9)◦].
The related thiadiazin-4-one S[NC(Cl)]2CO was, in con-
trast, found to be planar. Bond distances and angles are
within the expected range,[15] although it is worth noting
that C2 Cl1 (1.749(3) Å) is slightly longer than a typical
C Cl single bond (1.729 Å)[16] while C2 N1 represents,
with 1.233 (4) Å, a comparatively short CN double bond
(1.279 Å).[16] Weak Cl· · · Cl interactions (3.492 Å) between
adjacent molecules of compound 3a lead to the formation of
infinite chains in the crystal (Fig. 2).The influence of Cl· · · Cl
contacts in the range of 3.5–4.0 Åon the solid-state structures
of organic chlorides has been discussed previously.[17]
The gold compound 6a is sensitive to air, moisture, and
light, and is soluble only in polar solvents in which it slowly
decomposes. Compounds 4a and 5a are colourless solids that
are insoluble in hydrocarbons but soluble in polar solvents
(CH2Cl2, CHCl3, C6H6, DMSO).
O1
The molecular structure of compound 4a with an atomic
labelling scheme is shown in Fig. 3, selected bond dis-
tances are in Table 1. The central carbon (C1) of
compound 4a shows a tetrahedral geometry with the
three imidoylchloride substituents arranged in a pro-
peller like fashion [torsion angles C11 N1 C2 Cl1
Cl1ꢃ
Cl1
C1
C2ꢃ
C2
N1
C18
N1ꢃ
C16
C1l
C11
Cl1
Cl1ꢃ
C15
C17
C12
C14
C13
Fig. 1. Molecular structure of compound 3a. Thermal ellipsoids are
drawn at the 50% probability level. H atoms have been omitted for
clarity.
Fig. 2. Cl· · · Cl interactions in compound 3a.
Table 1. Selected bond distances (Å) for 3a, 4a, 5a, and the cation of 6a
Xa = Cl1 (3a, 4a), O2 (5a, 6a); Xb = Cl2 (4a), O3 (5a, 6a); Xc = Cl3 (4a), Cl1 (6a), O4 (5a)
A
A
Bond
3a
4a
5a·0.5CHCl3
5a·0.36CH2Cl2
6a
C1–O1
1.194(6)
1.404(2)
1.403(5)
1.407(5)
1.543(7)
1.546(7)
1.537(6)
1.539(7)
1.543(7)
1.528(7)
1.225(5)
1.230(5)
1.330(6)
1.350(6)
1.213(5)
1.226(5)
1.332(6)
1.334(6)
1.221(5)
1.208(6)
1.313(6)
1.313(6)
1.394(6)
1.422(6)
1.543(7)
1.543(7)
1.560(7)
1.536(7)
1.567(8)
1.540(7)
1.228(6)
1.230(6)
1.313(7)
1.341(6)
1.219(6)
1.231(6)
1.330(6)
1.336(6)
1.229(6)
1.199(6)
1.314(7)
1.309(6)
1.406(6)
C1–C2
C1–C3
C1–C4
C2–Xa
C2–N1
C3–Xb
C3–N2
C4–Xc
C4–N3
1.519(4)
1.541(2)
1.529(2)
1.531(3)
1.740(2)
1.240(2)
1.750(2)
1.244(2)
1.753(2)
1.236(2)
1.567(8)
1.568(8)
1.526(8)
1.218(7)
1.334(7)
1.221(7)
1.338(8)
1.676(6)
1.284(7)
1.749(3)
1.233(4)
A
Both solvates of 5a crystallize with two independent molecules in the asymmetric unit.

Studies of 2-Oxomalonylbis(arylimidoyl) Chlorides
525
C24
C22
C25
H1a
C25
C24
C23
C23
C26
H2
C28
C21
C26
C27
C22
C28
N2
C21
C27
O1
N2
C3
C3
C17
C18
H1
C38
O3
Cl2
C36
N1
C15
O4
Cl1
C2
C35
C1
C16
C11
C38
C4
H3
C13
N1
C11
C16
C12
C34
C33
C32
N3
N3
C2
H1
C31
C36
C4
C1
C14
O2
C14
C37
C13
C35
C34
C31
Cl3
C12
O1
C17
C15
C18
C32
Fig. 3. Molecular structure of compound 4a. Thermal ellipsoids are
drawn at the 50% probability level. H atoms (except H1) have been
omitted for clarity.
C37
C33
Fig. 5. Molecular structure of compound 5a·0.5(CHCl3) (only one
independent molecule is shown). Thermal ellipsoids are drawn at the
50% probability level. H atoms (except H1A, H1, H2, and H3) have
been omitted for clarity.
crystallization. Since both structures are isomorphous, only
the structure solution yielding the better result is discussed
in more detail.
Cl3ꢃ
Cl3
The molecular structure of one of the independent
molecules of 5a·0.5(CHCl3) with an atomic labelling scheme
is shown in Fig. 5, selected bond distances are in Table 1.
The tetrahedral carbon atom C1 [C1ꢀ; atom labels of the
second independent molecules are indicated by a prime (ꢀ)]
at the centre of the molecule [angles range from
106.7(4)◦ (O1 C1 C4) to 112.2(4)◦ (C2 C1 C4) and from
104.9(4)◦ (C3ꢀ C1ꢀ C2ꢀ) to 111.2(4)◦ (C4ꢀ C1ꢀ C3ꢀ)] is
surrounded by three amide substituents [torsion angles
O1 C1 C4 O4 −10.6(7)◦, O1 C1 C2 O2 −168.2(4)◦,
O1 C1 C3 O3 −180.0(4)◦, O1ꢀ C1ꢀ C4ꢀ O4ꢀ −0.1(7)◦,
Fig. 4. Cl· · · Cl interactions in compound 4a (for symmetry codes see
Table 3).
O1ꢀ C1ꢀ C2ꢀ O2ꢀ
−162.1(4)◦,
O1ꢀ C1ꢀ C3ꢀ O3ꢀ
−0.1(3)◦, C21 N2 C3 Cl2 1.4(3)◦, C31 N3 C4 Cl3
−2.5(3)◦; angles between idealized planes of aromatic
rings C11 C16/C21 C26 68.77◦, C21 C26/C31 C36
81.62(6)◦, C31 C36/C11 C16 71.38(7)◦], which may
be compared to the similar arrangement found in
(C5H5N)3COH,[18] [(C5H5N)2(C5H5NH)COH]ClO4,[19] or
[(Me)NaC(Ph) C(Ph)N Cb]3COH[Na Cb].[20] Two Cl
atoms (Cl2, Cl3) lie on the same side as the OH group,
while Cl3 points in the opposite direction. There is an intra-
molecular hydrogen bond between the alcohol function and
N1 (cf. Table 3) while an additional interaction between
the chlorine atoms of two adjacent molecules (Cl3· · · Cl3ꢀ
3.427 Å) leads to the formation of a weakly bound centrosym-
metric dimer (Fig. 4).
Bond distances and angles (Table 1) as well as the arrange-
ment of the Cl atoms with respect to the aromatic rings are
similar to those in compound 3a.
Crystals of 5a suitable for single-crystal X-ray analysis
were grown from CHCl3 and CH2Cl2, respectively. Com-
pound 5a·0.5(CHCl3) and 5a·0.36(CH2Cl2) both crystallize
with two independent molecules of 5a in the asymmetric
unit and incorporate the respective solvent that was used for
179.8(5)◦; angles between idealized planes of aro-
matic rings C11 C16/C21 C26 24.3(2)◦, C21 C26/
C31 C36 36.2(2)◦, C31 C36/C11 C16 26.0(1)◦; C11ꢀ
C16ꢀ/C21ꢀ C26ꢀ 24.4(2)◦, C21ꢀ C26ꢀ/C31ꢀ C36ꢀ 48.2(1)◦,
C31ꢀ C36ꢀ/C11ꢀ C16ꢀ 37.9(2)◦] in such a way as to maxi-
mize intramolecular hydrogen bonding. The hydroxy groups
in each of the independent molecules form three intramolec-
ular hydrogen bonds (Fig. 6, Table 3) to the amide groups
[O1· · · O4 2.535(5) Å; N1· · · O1 2.590(6) Å; N2· · · O1
2.606(6) Å; O1ꢀ· · · O4ꢀ 2.519(5) Å; N1ꢀ· · · O1ꢀ 2.651(6) Å;
N2ꢀ· · · O1ꢀ 2.607(5) Å] which are hydrogen bonded to
each other by two additional hydrogen bonds [N3· · · O2
2.804(5) Å; N3· · · O3 3.002(5) Å; N3ꢀ· · · O2ꢀ 2.860(6) Å;
N3ꢀ· · · O3ꢀ 2.918(5) Å]. The two molecules are connected by
two intermolecular hydrogen bonds [N1ꢀ· · · O3 3.143(5) Å;
N2ꢀ· · · O2 2.849(5) Å] and the hydrogen-bond network is fur-
ther extended to an infinite chain by two hydrogen bonds
to a third, symmetry related, molecule of 5a [N2· · · O3ꢀa
3
1
a
2.960(6) Å; N2· · · O2ꢀa 3.295(6) Å; x, − y + 2 , z + 2 ]. A
short CH· · · O [C41· · · O4b 3.080 Å, 148◦; b −1 + x, y, z][21]
contact between the solvent molecule CHCl3 and the chain of

526
R. J. Bowen et al.
Table 2. Selected bond distances (Å) and
angles (◦) of the anion of 6a
Bond distance [Å]
N3
N2
O4
Au–Cl2
Au–Cl4
Au–C13
Au–C15
2.265(2)
2.272(2)
2.292(2)
2.269(2)
O2
N2ꢃ
O3ꢃ
N1
O3
O1
Bond angle [◦]
ꢃa
O1ꢃ
O3
O4ꢃ
C12–Au–C13
C12–Au–C14
C12–Au–C15
C13–Au–C14
C13–Au–C15
C14–Au–C15
90.80(8)
179.03(9)
90.28(8)
89.19(7)
178.84(8)
98.74(7)
ꢃa
O2
N3ꢃ
N1´
O2ꢃ
5a molecules completes the hydrogen-bonding pattern. The
discussed hydrogen bonds may be compared with an aver-
age N· · · O distance of 2.93 Å found in amides[22] or 2.74 Å
in alcohols.[22]
Fig. 6. Hydrogen bonding in compound 5a (for symmetry codes see
Table 3). The methyl groups on the aromatic rings have been omitted
for clarity.
The bond distances (see Table 1) for C O and C N in
the backbone of 5a are unexceptional and may be compared
to those found in simple amides [CH3CONH2 1.2456(9),
1.3284(9) Å;[23] CH3CONHPh 1.234, 1.355,[24a] 1.222(2),
1.348(2)[24b] Å] or the α-hydroxyamides HOC(CH2CN)
(CONHCy)2 [CO 1.238(7), 1.227(7), CN 1.308(7),
1.342(7) Å],[25] HOCa(Et)CONHCONHCbO(Ca–Cb) [CO
1.208(2), 1.211(2), CN 1.380(2), 1.369(2) Å].[26]
C33
C37
C34
C35
C27
C22
C32
C23
C24
C25
C31
O3
C36
N3
Cl1
C21
C26
C4
C1
N2
C38
The molecular structure of compound 6a with an atomic-
labelling scheme is shown in Fig. 7, selected bond distances
and angles are in Tables 1 and 2. The organic cation has
resemblance with the structure of 4a, but the arrangement
of the amide/imidoylchloride substituents around the cen-
tral tetrahedral carbon atom is quite different [torsion
angles C11 N1 C2 O2 −5(1)◦, C21 N2 C3 O3 5(1)◦,
C31 N3 C4 Cl1 −5.5(9)◦; angles between idealized
planes of aromatic rings C11 C16/C21 C26 54.2(2)◦,
C3
O2
C2
O1
C28
N1
C17
C12
C13
C16
C11
Cl4
Cl6
C18
Cl7
Cl5
C14
C15
C40
Au
C21 C26/C31 C36
30.5(3)◦,
C31 C36/C11 C16
Cl3
30.0(3)◦]. The Cl atom of the imidoylchloride substituent is
on the same side as the alcohol functionality with a torsion
angle for O1 Cl C4 C11 of 13.5(7)◦, while the two amide
substituents are pointing in opposite directions in such a way
as to allow intramolecular hydrogen bonding between N3 H
and O2 and O3 [N3· · · O2 3.068(7) Å; N3· · · O3 2.567(7) Å],
respectively (Fig. 8, Table 3). Additional intermolecular
hydrogen bonding between N3 H3 and O2 [N3· · · O2d
2.887(6) Å, d −x + 1, −y, −z + 2] leads to the formation of a
centrosymmetric dimer. The intermolecular hydrogen-bond
pattern is completed by hydrogen bonding between O1–
H1A and Cl3 and Cl4 [O1· · · Cl3c 3.276(4) Å; O1· · · Cl4c
Cl2
Fig. 7. Molecular structure of compound 6a. Thermal ellipsoids are
drawn at the 50% probability level. H atoms (except H1A, H1, H2, and
H3) have been omitted for clarity.
N1d
Cl3c
N2d
O1d
N3
O2d
Auc
O3d
c
Cl4
Au
3.225(4) Å, −x, −y + 1, −z + 1], thereby connecting the
Cl4c
O3
dimeric cation with two AuCl−4 anions.
O2
O1
N2
N3d
The bond distances in the cation are similar to those of
the related compounds 4a and 5a with the exception of the
distances C4 N3 [1.287(7) Å] and C4 Cl1 [1.676(6) Å] that
are considerably longer or shorter, respectively, than the cor-
responding bond lengths in 4a but comparable to those in
[H2N C(Cl)CH3]+.[27] This may be a consequence of the
protonation of N3.
N1
Cl3
Fig. 8. Hydrogen bonding and intermolecular contacts in compound
6a (for symmetry codes see Table 3).

Studies of 2-Oxomalonylbis(arylimidoyl) Chlorides
527
Table 3. Hydrogen bonding [Å] in compounds 4a, 5a·0.5(CHCl3), and 6a
1
2
x, −y + 32 , z +
;
−x, −y + 1, −z + 1; −x + 1, −y, −z + 2
a
c
d
Compound
D–H · · · A
D–H
H · · · A
D · · · A
D–H · · · A
4a
O1–H · · · N1
0.99
0.82
0.86
0.86
0.86
0.86
0.86
0.86
0.82
0.86
0.86
0.86
0.86
0.86
0.86
0.84
0.84
0.88
0.88
0.88
0.88
0.88
1.95
2.01
2.27
2.34
2.17
2.11
2.44
2.38
2.01
2.16
2.17
2.59
2.32
2.23
2.61
2.71
2.47
2.17
2.65
2.07
2.25
2.11
2.602(2)
2.519(5)
2.651(6)
3.143(5)
2.607(5)
2.849(5)
2.860(6)
2.918(5)
2.535(5)
2.590(6)
2.606(6)
3.295(6)
2.960(6)
2.804(5)
3.002(5)
3.225(4)
3.276(4)
2.887(6)
3.068(7)
2.657(7)
2.691(7)
2.555(6)
121
119
107
156
111
143
111
121
121
110
111
139
132
124
109
121
162
139
110
123
111
111
5a·0.5(CHCl3)
O1ꢀ–HA1ꢀ· · · O4ꢀ
N1ꢀ–H1ꢀ· · · O1ꢀ
N1ꢀ–H1ꢀ· · · O3
N2ꢀ–H2ꢀ· · · O1ꢀ
N2ꢀ–H2ꢀ· · · O2
N3ꢀ–H3ꢀ· · · O2ꢀ
N3ꢀ–H3ꢀ· · · O3ꢀ
O1–H1A–O4
N1–H1· · · O1
N2–H2· · · O1
N2–H2· · · O2ꢀ
N2–H2· · · O3ꢀa
N3–H3· · · O2
N3–H3· · · O3
O1–H1A· · · Cl4c
O1–H1A· · · Cl3c
N3–H3· · · O2d
N3–H3· · · O2
N3–H3· · · O3
N2–H2· · · O1
N1–H1· · · O1
6a
Bond distances and angles (Table 2) in the square pla-
nar AuCl−4 anion are unexceptional and may be compared
with those in [C5H5NH][AuCl4],[28] [(Me2NCOCH3)2H]
[AuCl4],[29] [C(NH2)3][AuCl4],[30] or [EtC(OEt)NH2]
[AuCl4].[31]
crystals of 3a (2.45 g, 68%). A second crop of crystals was isolated
from the mother liquor (0.30 g, 8%), mp 60◦C (Found: C 62.9, H 5.0, N
7.7. C19H18Cl2N2O requires C 63.2, H 5.0, N 7.8%). νmax (Nujol)/cm−1
1737s(CO), 1679s(CN). δH (C6D6)1.98(s, Me), 6.86(s, Ph). δC (C6D6)
17.8 (Me), 125.9 ( p-C), 126.0 (ipso-C), 126.9 (m-C), 140.1 (ipso-C),
144.2 (C=N), 175.5 (C=O). m/z 360 (2%, M+), 325 (5, [M − Cl]+), 229
(30, [M −ArNC]+), 194 (7, [ArNC(Cl)CO]+), 166 (65, [ArNCCl]+),
131 (60, [ArNC]+).
Experimental
From Compound 2a and Triphosgene
All reactions were performed in flame-treated glass apparatus using
dry solvents unless otherwise stated. Solvents were distilled from dry-
ing agents and degassed. The NMR spectra were recorded in CDCl3,
C6D6, or (CD3)2SO at ambient probe temperature using Bruker DRX
400 (1H, 400.13 MHz; 13C, 100.6 MHz), Avance 300 (1H, 300.13 MHz;
13C, 75.5 MHz), or AC200 (1H, 200.13 MHz) instruments and refer-
enced internally to residual solvent resonances (chemical shift data in
δ). 13C NMR spectra were all proton decoupled. Elemental analyses
were determined by the Institute for Soil, Climate and Water, Pretoria,
SouthAfrica.Thecompilationoffragmentationandaccuratemassdeter-
minations were recorded on a Finnigan Matt 8200 spectrometer at an
electron impact of 70 eV.
Triphosgene (0.30 g, 1.0 mmol) was added to a solution of 2,6-
dimethylphenylisocyanide 2a (0.70 g, 5.3 mmol) in CH2Cl2 (20 cm3)
and the reaction mixture was stirred overnight to give a yellow solution.
The solvent was removed under vacuum and the residue was extracted
with hexane (30 cm3) and the extract was filtered. The filtrate was con-
centrated and kept at −60◦C to give a mixture (0.57 g) of 3a and 4a
in a ratio of 1 : 0.9 as determined by 1H NMR spectroscopy. Further
separation of the mixture was not attempted.
Synthesis of Compound 3b
Compound 3b (0.99 g, 86%) was synthesized in an analogous manner to
that described for compound 3a from 2,6-diisopropylphenylformamide
1b (1.00 g, 4.87 mmol), triphosgene (1.32 g, 4.45 mmol), and triethy-
lamine (1.6 cm3, 11.5 mmol), mp (Ar, dec.) 85◦C (Found: C 68.1, H
7.3, N 6.0. C27H34Cl2N2O requires C 68.5, H 7.2, N 5.9%). νmax
Synthesis of Compound 3a
From Compound 1a and Triphosgene
2,6-Dimethylphenylformamide 1a (3.00 g, 0.020 mol) was sus-
pended in a mixture of CH2Cl2 (60 cm3) and triethylamine (7 cm3,
0.050 mol) and a solution of triphosgene (5.50 g, 0.019 mol) in CH2Cl2
(30 cm3) was added dropwise at 0◦C. The reaction was exothermic and
thereactionmixtureturnedyellowwhiletheaminehydrochloridestarted
to precipitate. The ice bath was removed after the addition of triphos-
gene was completed and the reaction mixture was stirred overnight. The
reaction mixture was treated with water (40 cm3) that was previously
acidified with a few drops of HCl. The organic phase was separated, the
aqueous phase was extracted with CH2Cl2, and the combined organic
phases were dried with MgSO4. The MgSO4 was filtered off and the
solvent was removed under vacuum to give a yellow solid that was dis-
solved in hexane (50 cm3). The removal of a small amount of colourless
solid, concentration of the filtrate, and cooling to −20◦C gave yellow
(Nujol)/cm−1 1736s (CO), 1686s (CN). δH (C6D6) 1.15 (d, J(1H−1H)
3
3
6.85, Me), 2.99 (sept., J(1H−1H) 6.85, CH), 7.12 (s, m-Ph), 7.19 (s,
p-Ph). δC (C6D6) 22.5 (CH3), 29.1 (CH), 123.8 (m,p-C), 126.9 (m,p-C),
136.6 (ipso-C of Pri), 140.0 (ipso-C), 141.8 (C=N), 175.4 (C=O). m/z
473 (22%, [M + H]+), 437 (48, [M − Cl]+).
Synthesis of Compound 3c[14]
Compound 3c was obtained in an analogous manner to that described
for compound 3a from a solution of PhNHCHO 1c (0.86 g, 7.1 mmol) in
CH2Cl2 (20 cm3), triethylamine (2.3 cm3), and a solution of triphosgene
(2.00 g, 6.8 mmol) in CH2Cl2 (30 cm3) at 0◦C. Workup and removal of
volatiles gave a yellow oil, which was distilled at 100◦C at 10−2 torr to
give 0.73 g (67%) of 3c. δH (C6D6) 6.90–7.07 (s, Ph). δC (C6D6) 121.7

528
R. J. Bowen et al.
Table 4. Crystal data and refinement for compounds 3a, 4a, 5a, and 6a
Compound
3a
4a
5a·0.5(CHCl3)
5a·0.36(CH2Cl2)
6a
Molecular formula
M
T [K]
C19H18Cl2N2O
361.25
293(2)
C28H28Cl3N3O
528.88
293(2)
C28H31N3O4·0.5(CHCl3) C28H31N3O4·0.36(CH2Cl2) C29H33AuCl7N3O3
533.24
505.41
916.70
173(2)
293(2)
293(2)
Wavelength [Å]
Crystal system
Space group
a [Å]
0.71073
Monoclinic
C2
14.878(6)
7.968(3)
8.252(3)
0.71073
Triclinic
¯
P1
0.71073
Monoclinic
P21/c
13.118(2)
23.721(4)
17.967(3)
0.71073
Monoclinic
P21/c
12.763(3)
23.690(6)
17.952(4)
0.71073
Triclinic
¯
P1
7.8296(10)
13.3908(17)
13.9253(17)
78.045(2)
76.206(2)
86.530(2)
1387.0(3)
2
11.861(2)
12.965(3)
13.307(3)
114.121(4)
107.987(3)
93.534(4)
1734.4(6)
2
b [Å]
c [Å]
α [◦]
β [◦]
91.431(7)
90.870(3)
90.126(4)
γ [◦]
U [Å3]
Z
978.0(6)
2
1.227
0.339
376
5590.0(16)
8
1.267
0.222
2248
5428(2)
8
1.237
0.154
D(calc.) [mg m−3
]
1.266
0.355
552
1.755
4.815
900
µ [mm−1
F(000)
]
2142
Crystal size [mm3]
0.35 × 0.26 ×
0.60 × 0.49 ×
0.40 × 0.09 ×
0.38 × 0.30 ×
0.26 × 0.22 ×
0.24
0.36
0.07
0.15
0.14
θ range [◦]
Index ranges
2.47 to 25.99
−18 ≤ h ≤ 18,
−5 ≤ k ≤ 9,
−10 ≤ l ≤ 10
2859
1.55 to 28.29
−10 ≤ h ≤ 10,
−17 ≤ k ≤ 17,
−12 ≤ l ≤ 18
9605
1.42 to 25.00
−15 ≤ h ≤ 15,
−28 ≤ k ≤ 17,
−21 ≤ l ≤ 21
30405
1.42 to 25.00
−15 ≤ h ≤ 11,
−28 ≤ k ≤ 23,
−21 ≤ l ≤ 21
29277
1.76 to 26.00
−14 ≤ h ≤ 12,
−15 ≤ k ≤ 11,
−16 ≤ l ≤ 16
9982
Reflections
collected
Independent
reflections [R(int)]
Completeness
to θmax
1337 [0.0286]
25.99◦ (99.4%)
6663 [0.0153]
28.29◦ (96.5%)
9853 [0.1830]
9567 [0.0973]
25.00◦ (99.9%)
6714 [0.0610]
26.00◦ (98.5%)
25.00◦ (100.0%)
Abs. correction
‘T’max,min
Data/restraints/
parameters
Semi-empirical
0.9231, 0.8906
1337/1/112
Semi-empirical
0.8827, 0.8150
6663/0/323
None
—
9853/0/680
None
—
9567/23/674
Integration
0.5925, 0.1944
6714/0/394
Goodness-of-fit
on F2
1.034
1.044
0.870
0.983
1.051
Final R indices
[I > 2σ(I)]
R indices (all data)
R1 0.0392,
wR2 0.0911
R1 0.0507,
wR2 0.0965
None
R1 0.0437,
wR2 0.1036
R1 0.0787,
wR2 0.1168
None
R1 0.0622,
wR2 0.1304
R1 0.2597,
wR2 0.1974
0.0032(3)
R1 0.0891,
wR2 0.2511
R1 0.2020,
wR2 0.2869
None
R1 0.0422,
wR2 0.1019
R1 0.0554,
wR2 0.1106
None
Extinction
coefficient
Largest diff. peak
0.208 and −0.219 0.222 and −0.257 0.267 and −0.244
0.030 and −0.013
2.120 and −2.053
& hole [e Å−3
]
(s, o-Ph), 127.8 (s, p-Ph), 129.2 (s, m-Ph), 143.8 (s, ipso-C), 160.3 (s,
7.10 (m, p-Ph), 7.33 (m, m-Ph), 7.75 (m, o-Ph), 9.78 (s, OH). m/z
241 (38%, [(PhNHCO)2 + H]+), 122 (10, [PhNHCHO + H]+), 93 (71,
[PhNH2]+), 75 (8, [HC(OH)OEt]+).
C=N), 176.2 (s, C=O). m/z 304 (78%, M+), 269 (52, [M − Cl]+), 138
(100, [PhN=CCl]+).
Reaction of Compound 3a with Water
Synthesis of Compound 4a
Compound 3a (0.45 g, 1.24 mmol) was treated with water (10 cm3), and
the reaction mixture was stirred at room temperature for 3 days to give a
suspension with a colourless solid. Removal of the water under vacuum
gave 2,6 dimethylphenylformamide 1a as a colourless solid (0.35 g,
94%).
Compound 3a (2.40 g, 6.64 mmol) was dissolved under inert gas condi-
tions in benzene (10 cm3) and stirred at room temperature for two weeks.
During this period, the stopper of the reaction flask was removed twice
a day for approx. 2 min to allow moist air to diffuse into the reaction
mixture. After the reaction was complete the solvent was allowed to
evaporate (over approx. 3 days) to give colourless crystals of 4a (1.87 g,
80%) that were isolated by removing the remaining small quantities of
benzene, washing the crystals twice with 2 cm3 of hexane and drying
them under vacuum, mp (dec.) 129◦C (Found: C 64.3, H 5.4, N 8.0.
C28H28Cl3N3O requires C 63.6, H 5.3, N 7.9%). νmax (Nujol)/cm−1
3373s (O–H), 1678m (C=N). δH (C6D6) 2.12 (s, Me), 5.45 (br s, OH),
6.91 (s, Ph). δC (C6D6) 18.3 (Me), 88.6 (COH), 125.5 ( p-C), 126.8
(ipso-C), 128.5 (m-C), 144.6 (ipso-C), 145.9 (C=N). δH [(CD3)2SO]
Synthesis of (PhNHCO)2C(OH)OEt[14]
Compound 3c (0.26 g, 0.85 mmol) was mixed with an excess of H2O
by means of a spatula to initially give a yellow sticky solid that,
after 10 min at room temperature, turned into a colourless, fluffy
material. The water was removed and the solid recrystallized from
ethanol to give 0.09 g (67%) of (PhNHCO)2C(OH)OEt. δH (C6D6)
3
3
1.26 (t, J(H−H) 7.00, CH2CH3), 3.61 (q, J(H−H) 7.00, CH2CH3),

Studies of 2-Oxomalonylbis(arylimidoyl) Chlorides
529
2.07 (s, Me), 6.98 (t, 3J(1H−1H) 6.97, p-Ph), 7.08 (d, 3J(1H−1H) 6.97, m-
Ph), 9.70 (s, NH), OH (not observed). m/z 528 (24% [M + H]+), 492 (4,
[M − Cl]+), 459 (4, [M − 2Cl]+), 236 (44, [ArN=CCl + 2Cl]+), 131
(100, [ArN=C]+).
and ORTEP3.[35] Attempts to obtain a higher quality dataset for com-
pound 5a by growing crystals in different solvents and temperatures or
collecting data at low temperature were unsuccessful.
CCDC numbers 246538–246542 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge from http://www.ccdc.cam.ac.uk/conts/retrieving.html
(or from the Cambridge Crystallographic Database Centre, 12
Union Road, Cambridge, CB2 1EZ, UK; fax: +44-1223-336-033;
email:deposit@ccdc.cam.ac.uk).
Reaction of Compound 4a with Water
Compound 4a (0.20 g, 0.378 mmol) was suspended in water (5 cm3),
and the reaction mixture was stirred for 4 days at room temperature
while repeatedly crushing crystalline starting material with a spatula.
The water was removed to give 0.17 g of 5a contaminated with a small
amount of 1a.
Acknowledgments
The authors thank Mintek (project AuTEK), the Claude Har-
ris Leon foundation (postdoctoral research fellowship for
R.J.B.), and the University of the Witwatersrand for finan-
cial support, Mr Ian Vorster (Rand Afrikaans University) for
carrying out the mass spectrometry analyses, and Professor
D. Reid for helpful discussions.
NMR Data for Compound 4b
δH (C6D6) 1.20 (d, 3J(H−H) 4.80, Me), 3.20 (br s, OH), 7.11 (s, Ph). δC
(C6D6) 24.2 (Me), 28.6 (CH), 89.4 (COH), 123.9 (m-C), 126.3 (p-C),
137.6 (ipso-C), 142.3 (ipso-C), 145.5 (C=N).
Synthesis of Compound 5a
Compound 4a (0.34 g, 0.643 mmol) was dissolved in DMSO (4 cm3),
and the reaction mixture was stirred for 4 days at room temper-
ature. The solvent was removed under vacuum to give a colour-
less solid that was recrystallized from CH2Cl2 to give colourless
crystals of 5a (0.29 g, 95%), mp 203◦C (Found: C 65.9, H 6.5,
N 8.3. C28.36H31.72Cl0.72N3O4 requires C 67.4, H 6.4, N 8.3%). νmax
(Nujol)/cm−1 3377s (NH), 3327s(br) (OH), 1711s (CO), 1665s (CN).
δH (CDCl3) 2.22 (s, Me), 5.97 (br s, OH), 7.19 (m, m-Ph), 8.86 (s,
NH), OH not observed. δC (CDCl3) 18.3 (Me), 79.5 (COH), 127.9
(p-C), 128.3 (m-C), 132.6 (ipso-C), 135.2 (ipso-C, CMe2), 163.3 (CO).
δH [(CD3)2SO] 2.17(s, Me), 6.33 (br s, OH + H2O), 7.10 (m, m-Ph),
9.69 (s, NH). δC [(CD3)2SO] 17.8 (Me), 80.2 (COH), 126.7 (p-C), 127.6
(m-C), 143.1 (ipso-C), 135.1 (ipso-C, CMe2), 164.7 (CO). m/z
474 (38%, [M + H]+), 327 (18, [M + 2H −ArNHCO]+), 148 (100,
[ArNHCO]+).
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atmosphere into a flask and a solution of 4a (0.24 g, 0.45 mmol) in
CH2Cl2 (10 cm3) was added at room temperature. The reaction mixture
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Intensity data were collected on a Bruker SMART 1K CCD area detector
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compound 4a) were located from the difference map and then positioned
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(in compound 4a) was located from the difference map and then allowed
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