3
acridine nucleus. The presence of substituents increasing the partial positive charge on the sp -hybrid center aids
the formation of the diazepine ring. The formation of acridones is a consequence of reduction of the charge at the
3
sp -hybrid carbon atom (synthesis of product 6) or the low nucleophilicity of the neighboring nucleophilic center
(
synthesis of products 7a-f).
Under the conditions of an one-pot synthesis using o-phenylenediamine, dimedone, and aldehydes 10a-o
the sole products were hexahydrobenzodiazepinones 4. Compounds 4a-o were synthesized on boiling dimedone
with diamine 2 in 2-propanol for 30-40 min in the presence of catalytic amounts of AcOH and subsequent
addition of aromatic aldehyde 10a-o to the reaction mixture (method B). Diazepines 4g-i, containing electron-
donating groups in R, and also products 4n,o with a substituent ArCO at position 11 (the appropriate glyoxals
were put into the reaction mixture in place of aldehydes) were obtained by the same method. Compounds 4a-o
were obtained in better yield under conditions of the one-pot synthesis (Table 1), and the reaction time was
reduced significantly (see Experimental). The intermediate enamine 11 was not isolated by us under these
conditions but its presence has been confirmed as a fact in [7]. The formation of enamine determines the
direction of the overall process, since in experiments with simultaneous participation of diamine 2, dimedone,
and aromatic aldehyde 10, 2-arylbenzimidazoles were obtained exclusively, i.e. the rate of interaction of diamine
with aldehyde was greater than the rate of enamine formation, which is in good agreement with our data [8]. The
1
composition and structure of compounds 4a-o, 6, 7a-f were confirmed by data of elemental analysis, IR and H
NMR spectra (Tables 1 and 2), and in the case of compound 4a, also by X-ray diffraction analysis (Fig. 1 and
Tables 3-5).
According to the data of X-ray diffraction analysis product 4a is 3,3-dimethyl-11-phenyl-2,3,4,5,10,11-
hexahydrodibenzo[b,e]-1,4-diazepin-1-one. In the independent part of the unit cell of the compound 4a crystal
there are two molecules (I and II) which differ in the conformation of the cyclohexene fragment. The six-
membered ring in molecule I has the form of a distorted chair. The deviations of the C(8) and C(9) atoms from
the mean square plane of the remaining ring atoms are 0.52 and 0.13 Å respectively.
In molecule II the cyclohexene fragment is in the sofa conformation. The deviation of the C(8') atom
from the mean square plane of the remaining ring atoms is 0.65 Å.
The diazepine ring in both molecules has a shape intermediate between a twist-chair and a twist-boat.
The deviations of the N(2) and C(13) atoms from the mean square plane of the remaining ring atoms are 0.84
and 0.22 Å for molecule I and 1.01 and 0.55 Å for molecule II respectively.
The phenyl substituent at C(12) atom (Fig. 1) has an axial orientation [the torsion angle C(6)–C(11)–
C(12)–C(16) is 96.2(2)° in molecule I and 84.1(2)° in molecule II] and is twisted relative to the C(11)–C(12)
bond [the torsion angle C(11)–C(12)–C(16)–C(21) is 44.9(3)° in molecule I and 29.4(3)° in molecule II].
The formation of intermolecular hydrogen bond N(1')–H(1N')···O(1) (1 - x, y - 0.5, 0.5 - z) (H'···O is
2
1
.11Å, N'–H'···O 169°) leads to lengthening of bonds O(1)–C(10) 1.253(2) (I), 1.254(2) (II), C(6)–C(11)
.384(3) (I), 1.394(3) Å in (II) and shortening of bond C(10)–C(11) 1.448(3) Å (I), 1.439(3) Å (II) in
comparison with mean values of 1.210, 1.340, and 1.464 Å respectively. Shortened contacts were detected in the
structure at O(1)···H(12) of 2.36 (I) and 2.33 Å (II), H(15B)···C(10) 2.83 (I) and 2.81 (II), and H(15B')···C(6')
2
.77 Å for total sum of the van der Waals radii of O···H 2.45 and H···C 2.87 Å.
The closeness of the spectral characteristics of compounds 4a and 4b-o (see Tables 1, 2) permits their
assignment to one series of isomers. In their IR spectra there are bands for the stretching vibrations of the
-
1
-1
enamine carbonyl group of low intensity at 1615-1650 cm , and also two bands at 3230-3350 cm assigned to
the stretching vibrations of the secondary amino group.
1
The H NMR spectra of compounds 4 were more informative. The position, shape, and intensity of the
recorded proton signals correspond to the structure of hexahydrodibenzodiazepinones indicated in the scheme
(
Table 2). The singlets in the region of 6.0 and 8.50 ppm, disappearing under deuterium exchange conditions,
were assigned to the imine and enamine protons respectively.
1
552