FIRST EXAMPLE OF GENERATION OF UNSYMMETRICAL BIS(IMIDOYL)KETENE
943
solvent (Dowtherm A) at 185–187°C over a period of
C34
C15
C10
C36
N4
C35
C37
1 h resulted in generation of unsymmetrical bis-
(imidoyl)ketene III which underwent unusual intra-
molecular cyclization with formation of 2-methyl-6-[4-
methylphenyl(2,4,6-trimethylphenylimino)methyl]-
benzo[a]phenazin-5-ol (IV) whose structure was
proved by X-ray analysis. Presumably, bis(imidoyl)-
ketene III generated by thermal decarbonylation of
pyrroledione II is stabilized via intramolecular
C-acylation by the ketene fragment at the ortho
position of the p-tolyl substituent in the quinoxaline
fragment. The described reaction may be regarded as
the first example of generation of ketene containing
two different imidoyl fragments directly conjugated to
the ketene moiety by thermal decarbonylation of
substituted 1H-pyrrole-2,3-dione, as well as the first
example of a novel intramolecular cyclization of imid-
oylketenes in which the imidoyl fragment is a part of
heterocyclic system.
C33
C32
O1
C9
C30
C11
C8
C7
C12
C31
C38
C22
C6
C13
C5
C28
C14
N3
C23
C24
N2
C16
C27
C26
C21
C20
C17
C18
C25
C19
C29
Structure of the molecule of 2-methyl-6-[4-methylphenyl-
(2,4,6-trimethylphenylimino)methyl]benzo[a]phenazin-5-ol
(IV) according to the X-ray diffraction data.
ane. Triclinic crystals, C34H29N3O, with the following
unit cell parameters: a = 8.165(2), b = 12.691(3),
c = 13.211(3) Å; α = 96.63(3), β = 98.35(3), γ =
5-(4-Methylphenyl)-4-[3-(4-methylphenyl)quin-
oxalin-2-yl]-1-(2,4,6-trimethylphenyl)-2,3-dihydro-
1H-pyrrole-2,3-dione (II). A solution of 1 mmol of
2,4,6-trimethylaniline in 5 ml of anhydrous chloroform
was added dropwise to a solution of 1 mmol of furan-
dione I [5] in 5 ml of anhydrous chloroform, the
solvent was evaporated by half, and the precipitate was
filtered off. Yield 0.29 g (56%), mp 222–224°C (from
cyclohexane). IR spectrum, ν, cm–1: 1754 (C2=O),
100.88(3)°; V = 1315.6(5) Å3; M 495.6; dcalc
=
1.251 g/cm3; Z = 2; space group P-1. The unit cell
parameters and experimental reflection intensities were
measured on a KM-4 (Kuma Diffraction) automatic
four-circle diffractometer with χ-geometry (monochro-
matized CuKα irradiation; ω–2θ scanning in the range
3.42 < 2θ < 80.22°). Total of 5446 independent reflec-
tions were measured. No correction for absorption was
introduced (μ = 0.593 mm–1). The structure was solved
by the direct statistical method, followed by a series of
calculations of electron density maps. The positions of
hydrogen atoms were set on the basis of geometry
considerations after refinement to R = 0.0995 by the
least-squares procedure in anisotropic approximation.
The final divergence factor was R1 = 0.0569. All cal-
culations were performed using SHELX97 software
package [6]. The tetracyclic benzophenazine fragment
in molecule IV is planar, and the bond lengths therein
indicate the presence of common conjugation system.
Molecule IV is stabilized by intramolecular hydrogen
bond between the 5-OH group and nitrogen atom in
the mesitylimino group (2.48 Å); parameters of the
O–H···N hydrogen bond: O–H 0.82, H···N 1.74 Å,
∠OHN 148.3°.
1
1712 (C3=O). H NMR spectrum, δ, ppm: 2.05 s (3H,
Me), 2.13 s (3H, Me), 2.25 s (3H, Me), 2.35 s (3H,
Me), 2.45 s (3H, Me), 6.50–8.15 m (14H, Harom).
Found, %: C 80.44; H 5.61; N 8.08. C35H29N3O2. Cal-
culated, %: C 80.28; H 5.58; N 8.02.
2-Methyl-6-[4-methylphenyl(2,4,6-trimethyl-
phenylimino)methyl]benzo[a]phenazin-5-ol (IV).
A solution of 1 mmol of pyrroledione II in 5 ml of
anhydrous Dowtherm A was kept for 1 h at 185–
187°C, the solvent was removed, and the residue was
subjected to chromatography on a column (1×30 cm)
charged with silica gel (100–150 μm) using benzene as
eluent; the first yellow fraction was collected. The sol-
vent was removed, and the product was recrystallized
from cyclohexane. Yield 61%, mp 275–276°C (from
cyclohexane). IR spectrum: ν 3400 cm–1, br (OH).
1H NMR spectrum, δ, ppm: 2.15 s (3H, Me), 2.25 s
(3H, Me), 2.27 s (3H, Me), 2.28 s (3H, Me), 2.30 s
(3H, Me), 6.85–8.20 m (13H, Harom), 10.22 s (1H,
OH). Found, %: C 82.58; H 5.86; N 8.45. C34H29N3O.
Calculated, %: C 82.40; H 5.90; N 8.48.
The IR spectra were measured on a UR-20 spec-
trometer from samples dispersed in mineral oil. The
1H NMR spectra were recorded on a Bruker AM-
300 spectrometer at 300.13 MHz from solutions in
DMSO-d6 using HMDS as internal reference. The
purity of the isolated compounds was checked by TLC
on Silufol plates; eluent benzene–ethyl acetate (5:1).
X-Ray diffraction data for compound (IV) (see
figure). Single crystals of IV suitable for X-ray anal-
ysis were obtained by crystallization from cyclohex-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 6 2010
Lisovenko
