250
SHCHEPIN et al.
rise to 6-(arylphenylhydrazonomethyl)-3,3,5,5- tetra-
methyl-2,3,5,6-tetrahydropyran-2,4-diones (VIa e).
group in the regions 1720, 1745 1750, 3330 3360
respectively.
EXPERIMENTAL
1H NMR spectra of compounds Vc e, h j, VIb e
were registered in CDCl3 solutions on spectrometer
RYa-2310 (60 MHz), of compounds Va, b, f, g, VIa
in DMSO-d6 solutions on spectrometer Bruker DRX-
500 (500 MHz). TMS was used as internal reference.
IR spectra were measured on spectrophotometer
UR-20 from individual compounds.
VI, Ar = Ph (a), 4-EtC6H4 (b), 4-FC6H4 (c),
4-ClC6H4 (d), 4-BrC6H4 (e).
For interpretation of the results obtained we used
simulation of phenylhydrazine nucleophilic attack on
the carbons of keto groups in Va molecule by semi-
empirical procedure SCF MO LCAO in AM1 approx-
imation [2] applying the method of reaction co-
ordinate. As the latter were chosen the interatomic
distances l(C N). We calculated the formation
enthalpy Hf of a supermolecule (Va) phenylhydr-
azine by scanning the interatomic distance l(C N)
from 3.00 to 1.55 with a step of 0.01 . It turned
out that the Hf value increased monotonically from
The quantum-chemical calculations were carried
out on PC Pentium 200 MMX using a software
package MOPAC 7.0 [3] with complete optimization
of all geometrical parameters.
6-Aroyl-3,3,5,5-tetramethyl-2,3,5,6-tetrahydro-
pyran-2,4-diones (Va j). To 4 g of fine zinc turnings
in a mixture of 15 ml of anhydrous ethyl ether and
5 ml of anhydrous ethyl acetate was added 0.04 mol
of methyl 4-bromo-3-oxo-2,2,4-trimethylpentanoate.
On completion of the reaction the mixture was heated
for 30 min. The reaction mixture was then cooled,
0.033 mol of arylglyoxal solution in 10 ml of
anhydrous benzene was added, the mixture was boiled
for 20 min, cooled, hydrolyzed with 5% hydrochloric
acid, and the reaction products were extracted into
ether. The organic layer was dried with anhydrous
sodium sulfate, the solvents were distilled off, and
compounds Va j were recrystallized from methanol
(Table 1).
1
348.6 to 195.7 kJ mol at the attack on benzoyl
1
carbonyl, and from 333.3 to 148.8 kJmol at the
attack of the C4= O carbonyl. Since the second curve
is located higher than the first as regards the Hf
axis, the energy consumption at the attack on C4
should be considerably greater apparently due to the
steric hindrances from the methyl groups attached to
C3 and C5. This is the reason why among the reaction
products we did not find phenylhydrazones alternative
to the above mentioned.
6-(Arylphenylhydrazonomethyl)-3,3,5,5-tetra-
methyl-2,3,5,6-tetrahydropyran-2,4-diones(VIa e).
To 0.004 mol of compound Va, c, e g dissolved in
10 15 ml of glacial acetic acid was added 0.006 mol
of phenylhydrazine. The mixture was stored at room
temperature for 4 10 days, then the separated preci-
pitate of phenylhydrazone was filtered off and twice
recrystallized from methanol (Table 2).
The calculations also show that the phenyl-
hydrasone with syn-orientation of the phenyl sub-
stituent and NH Ph group with respect to C=N bond
1
is by 30.09 kJ mol more stable that the correspond-
ing anti-isomer.
The yields of phenylhydrazones VIa e are
45 65% (Table 2).
Their composition and structure were confirmed
REFERENCES
1
by elemental analyses, H NMR and IR spectra. In
1
the H NMR spectra (CDCl3, , ppm) appear char-
1. Shchepin, V.V. and Gladkova, G.E., Zh. Org. Khim.,
1995, vol. 31, no. 7, p. 1094.
2. Dewar, M.J.S., Zoebisch, E.G., Healy E.F., and
Stewart, J.J.P., J. Am. Chem. Soc., 1985, vol. 107,
no. 13, pp. 3902 3909.
acteristic signals at 7.50 7.67, 4.83 4.93, 1.13 1.45
from a proton of NH group, methine proton from
CHO group, and from four methyl groups (CMe2,
1
CMe2) respectively. In the IR spectra ( , cm ) are
present the absorption bands of the keto and lactone
groups in the heterocycle, and also those of the NH
3. Stewart, J.J.P., MOPAC. Version 7.0, Frank J. Seiler
Research Laboratory, US Air Force Academy QOMP.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 2 2002
Shchepin
