761
NITROGEN-CONTAINING HETEROCYCLES
Table 2. Yields of pyrazoles XLVIII–LI in the reactions of
chelates IV and XLV–XLVII with phenylhydrazine
(reaction time 60 min)
extracted with chloroform (3×5 ml). The extract was
dried over magnesium sulfate and evaporated under
reduced pressure, and the residue was recrystallized
from a minimal amount of alcohol. According to the
GC–MS data, all isolated compounds contained only
one volatile component whose mass spectrum matched
pyrazole XXIV–XXXVI with a probability of 80–95%
(NIST05 library). Their IR spectra matched pyrazoles
XXIV–XXXVI with a probability of 70–95% (Aldrich
Condensed Phase library). The yields and melting
points of the isolated compounds are given in Table 1 [4].
Chelate
R1
R2
R3
H
Pyrazole Yield, %
Me
Me
72
IV
XLVIII
Me
Me
Me
Me
Me
Me
Me
Ph
73
69
75
XLV
XLIX
L
XLVI
XLVII
SPh
LI
Reactions of diketonates IV, XLV, XLVI, XLVII,
Al(acacBr)3, and Al(acacNO2)3 with phenylhyd-
razine hydrochloride, urea, and thiourea (general
procedure). A mixture of 1 mmol of aluminum
complex and 3 mmol of the corresponding nitrogen-
containing nucleophile in ethanol was heated until it
became homogeneous, 0.3 ml of concentrated
hydrochloric acid was added, and the mixture was
heated for 3 h more. The solution was filtered while
hot and was left to stand in the cold for crystallization.
The precipitate was filtered off, dried, and dissolved in
5 ml of water, 1 ml of 25% aqueous ammonia was
added, and the mixture was extracted with chloroform.
The extract was evaporated, and the residue was
analyzed by LC–MS (HP 1100 LC). The yields of
pyrazoles formed in the reactions with phenylhyd-
razine and reaction times are given in Table 2.
Thin-layer chromatography was performed on
Sorbfil PTSKh-P-V plates using benzene or benzene–
acetone (10:1) as eluent. The analytical data for the
isolated compounds are collected in Table 1.
Acetylacetonates I–V and VII–XV were syn-
thesized by standard procedures in aqueous alcohol in
the presence of sodium acetate and were purified by
recrystallization from appropriate solvent (alcohol or
benzene–petroleum ether). 2,4-Dioxopentane-3-carb-
aldehyde (VI) was synthesized according to the
procedure described in [7], complexes XVII–XXII
were prepared as reported in [8], and compound XXIII
was obtained as described in [9].
Tris(3-selenocyanatopentane-2,4-dionato)chro-
mium(III) [Cr(acac)x(acacSeCN)3–x]. Triselenium di-
cyanide was prepared according to the procedure
described in [10]. Selenium dioxide, 6.75 mmol, was
added to a solution of 4.5 mmol of malononitrile in 1
ml of DMF. After 2 min, the mixture turned turbid and
gradually warmed up, and gas evolution was observed.
After cooling, a solution of 2 mmol of tris(acetyl-
acetonato)chromium(III) in 2 ml of DMF was added in
small portions. The mixture was stirred until the
reaction was complete (TLC) and diluted with a
saturated aqueous solution of sodium chloride, the
precipitate was filtered off, dried under reduced
pressure over phosphoric anhydride, and dissolved in
chloroform, the solution was filtered, and the product
was precipitated with hexane and purified by
recrystallization from benzene–hexane.
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Reaction of metal diketonates I–XXIII with
hydrazine hydrate (general procedure). A mixture of
0.5 g of complex I–XXIII, 10 ml of alcohol, and 1 ml
of hydrazine hydrate was heated under reflux until it
became colorless and hydroxo metal salt separated (for
reaction time, see Table 1). After cooling, the mixture
was diluted with a tenfold volume of water and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 4 2011