Dehydrogenation of 1-(diphenylphosphinoyl)-2-(N′-phenylhydrazino) ethane and N-butyl-N′-phenylhydrazine

Article abstract of DOI:10.1134/S1070363206110144

Dehydrogenation of 1-(diphenylphosphinoyl)-2-hydrazino-substituted ethanes and N-butyl-N′-phenylhydrazine to the corresponding hydrazone derivatives is performed. Both reactions were established to involve predominantly, if not exclusively, an azo interme

Full text of DOI:10.1134/S1070363206110144

ISSN 1070-3632, Russian Journal of General Chemistry, 2006, Vol. 76, No. 11, pp. 1757 1759.
Original Russian Text M.Zh. Ovakimyan, S.K. Barsegyan, A.S. Pogosyan, N.M. Kikoyan, M.G. Indzhikyan, 2006, published in Zhurnal Obshchei
Khimii, 2006, Vol. 76, No. 11, pp. 1839 1841.
Pleiades Publishing, Inc., 2006.
Dehydrogenation
of 1-(Diphenylphosphinoyl)-2-(N -phenylhydrazino)ethane
and N-Butyl-N -phenylhydrazine
M. Zh. Ovakimyan, S. K. Barsegyan, A. S. Pogosyan,
N. M. Kikoyan, and M. G. Indzhikyan
Institute of Organic Chemistry, National Academy of Sciences of Armenia,
ul. Kankaretsi 3, Erevan, 375091 Armenia
Received May 30, 2006
Abstract Dehydrogenation of 1-(diphenylphosphinoyl)-2-hydrazino-substituted ethanes and N-butyl-N -
phenylhydrazine to the corresponding hydrazone derivatives is performed. Both reactions were established to
involve predominantly, if not exclusively, an azo intermediate.
DOI: 10.1134/S1070363206110144
Recently we found [1, 2] that triphenyl- and tri-
butylhydrazinoethylphosphonium salts, even under
moderate heating in alcohol or acetonitrile, are de-
hydrogenated to afford the corresponding hydrazone
derivatives or their further isomerization products, viz.
, -unsaturated phosphonium salts.
2-(N -phenylhydrazino)ethane (II) by the reaction of
diphenyl(vinyl)phosphine oxide (I) with phenylhyd-
razine.
It was found that even when a mixture of phos-
phine oxide I with a double molar excess of phenyl-
hydrazine was kept at room temperature, compound
II was formed together with its dehydrogenation
products 1-(diphenylphosphinoyl)-2-(phenylazo)-
ethane (III) and (diphenylphosphinoyl)acetaldehyde
phenylhydrazone (IV). Unchanged compound I was
recovered by 36.4%.
To extend the field of application of this reaction
and elucidate the feasibility of similar dehydrogena-
tion of related tertiary hydrazino-substituted phos-
phine oxides and N-alkyl-N -phenylhydrazines, we first
of all performed synthesis of 1-(diphenylphosphinoyl)-
Ph2PCH=CH2 + PhNHNH2
Ph2PCH2CH2NHNHPh
O
O
I
II
Ph2PCH2CH2N=NPh + Ph2PCH2CH=NNHPh
O
O
III
IV
The resulting mixture was refluxed in anhydrous
benzene for 4 h, which resulted in complete isomeriza-
tion of the azo derivative to phenylhydrazone.
The products were isolated by fractional crystalliza-
1
tion and identified by H and 31P NMR spectroscopy.
The reaction of oxide I with N,N-dimethylhydra-
zine occurs much easier than with phenylhydrazine
and results in quantitative formation of adduct V.
However, unlike compound II, phosphine oxide V
even under longer heating at a higher temperature
gives only little dehydrogenation product (diphenyl-
phosphinoyl)acetaldehyde dimethylhydrazone (VI).
Similar results were obtained when the reaction
was performed under heating, except that less di-
phenyl(vinyl)phosphine oxide was recovered.
It is interesting to note that the reaction of oxide I
with a large excess of phenylhydrazine under the same
conditions gave an isomeric product formed by alkyla-
tion by thesubstituted nitrogen atom ofphenylhydrazine.
Comparison of the results of dehydrogenation of
1757

1758
OVAKIMYAN et al.
Ph2PCH=CH2 + (CH3)2NNH2
O
Ph2PCH2CH2NHN(CH3)2
Ph2PCH2CH=NN(CH3)2.
O
O
V
VI
hydrazino-substituted phosphonium salts and phos-
phine oxides shows that the most essential difference
is the absence of azo intermediates in the first case.
Previously we proposed an ionic mechanism for the
dehydrogenation of the salts, involving expulsion of
hydride ion from the carbon atom neighboring to the
hydrazino group [2]. The absence of azo derivative in
this case might be explained by its easier isomeriza-
tion into hydrazone derivative. However, this explana-
tion is ruled out by the absence of this possibility with
(C6H5)2P, NC6H5], 22.7% of 1-(diphenylphosphinoyl)-
1
2-(phenylazo)ethane (III), H NMR spectrum, , ppm
2
(J, Hz): 3.20 d.t (2H, PCH2, JPH 13.80, JHH 7.0),
4.40 d.t (2H, CH2N, 3JPH 8.0, JHH 7.0) 6.20 6.80 and
7.40 7.80 m [15H, (C6H5)2P, NC6H5], and 13.6% of a
mixture of cis- and trans-(diphenylphosphinoyl)acet-
1
aldehyde phenylhydrazone (IV) whose H and 31P
NMR data correspond to those in [5].
The resulting mixture was refluxed in anhydrous
benzene for 4 h, after which the percentages of com-
pounds I, II and IV in it became 28.6, 23.8, and
47.6%, respectively.
N ,N -dimethylhydrazino-substituted
phosphonium
salts. On the other hand, two alternative mechanisms
of dehydrogenation can be assumed for different cases.
b. Phenylhydrazine, 2 g, was added to 1 g of oxide
I. The reaction mixture was kept at room temperature
for 5 days, diluted with anhydrous diethyl ether, and
left to stand for 2 days to precipitate 0.25 g (17%) of
N-phenyl-N-[2-(diphenylphosphinoyl)ethyl]hydrazine
We obtained interesting data with N-butyl-N -phe-
nylhydrazine, a phosphorus-free analog of the com-
pounds studied. It is known from the literature that
N-alkyl-N -phenylhydrazines in the presence of
mercury oxide are smoothly dehydrogenated to form
the corresponding azo compounds [3]. We found that
N-butyl-N -phenylhydrazine on 4-h heating at 150 C
both in an inert atmosphere and in air converts to a
mixture of phenylazobutane and butyraldehyde phe-
nylhydrazone, and further 10-h heating leads to com-
plete conversion of the azo isomer to phenylhydrazone.
1
(VII), mp 151 152 C, yellow crystals. H NMR spe-
ctrum, , ppm (J, Hz): 2.70 d.t (2H, PCH2, 2JPH 5.50,
3
JHH 7.60), 3.80 d.t (2H, CH2N, JPH 6.50, JHH 7.60),
4.0 4.20 m (2H, NHNH), 6.80 7.20 m (5H, NC6H5),
7.40 7.80 m [10H, (C6H5)2P]. 31P NMR spectrum:
31.36 ppm. The ether solution was evaporated to
P
isolate a mixture of compounds I, II, III, IV, and VII
in yields of 46.6, 21.6, 8.3, 11.7, and 11.7%, respec-
tively.
Thus, the resulting data allow us to conclude that
the tendency for dehydrogenation is a general property
of hydrazino derivatives, and it can proceed by dif-
ferent schemes, depending on the structures of the
latter.
Reaction of diphenyl(vinyl)phosphine oxide (I)
with N,N-dimethylhydrazine. A mixture of 1 g of
oxide
I
and
1
g
of N,N-dimethylhydrazine
was left at room temperature for 4 days. Excess N,N-
dimethylhydrazine was distilled off to obtain 1.25 g
(98%) of 1-(diphenylphosphinoyl)-2-(N ,N -dimethyl-
EXPERIMENTAL
The H and 31P NMR spectra were registered on a
Varian Mercury-300 spectrometer (300 MHz), in
CDCl3.
1
1
hydrazino)ethane (VI). H NMR spectrum, , ppm (J,
2
Hz): 2.20 s [6H, (CH3)2N], 2.45 d.t (2H, PCH2, JPH
3
9.90, JHH 6.60), 2.60 d.t (2H, NCH2, JPH 11.60, JHH
6.60), 7.40 7.70 m [10H, (C6H5)2P]. 31P NMR spec-
trum: P 31.60 ppm. Compound V, 1 g, was dissolved
in 10 ml of acetonitrile (or benzene), the solution was
heated at 80 C for 24 h, and the solvent was removed
to obtain of 1 g of a mixture of compound VI and
(diphenylphosphinoyl)acetaldehyde dimethylhydra-
Reaction of diphenyl(vinyl)phosphine oxide (I)
with phenylhydrazine. Diphenylvinylphosphine
oxide was prepared according to [4]. a. Phenylhydra-
zine, 0.95 g, was added to 1 g of oxide I in 6 ml of
anhydrous benzene, and the mixture was kept at room
temperature for 4 days. Excess phenylhydrazine was
then filtered off to obtain 1.4 g of a substance which,
1
zone (VII), H NMR spectrum, , ppm (J, Hz): 2.62 s
2
1
[6H, (CH3)2N], 3.38 d.d (2H, PCH2, JPH 17.30, JHH
according to the H NMR spectrum, contained 36.4%
8.0), 6.40 d.t (1H, CH=N), 7.40 7.80 m [10H,
(C6H5)2P], in yields of 92 and 8%, respectively.
of diphenyl(vinyl)phosphine oxide, 27.3% of 1-(diphe-
nylphosphinoyl)-2-(N -phenylhydrazino)ethane (II),
1H NMR spectrum, , ppm (J, Hz): 2.60 d.t (2H,
PCH2, JPH 11.0, JHH 7.0), 2.90 d.t (2H, CH2N, JPH
11.50, JHH 7.0), 6.20 6.80 and 7.40 7.80 m [15H,
Dehydrogenation of N-butyl-N -phenylhydrazine
prepared by hydrogenation of butyraldehyde phenyl-
hydrazone according to [3]. N-Butyl-N -phenylhydra-
2
3
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 11 2006

DEHYDROGENATION OF 1-(DIPHENYLPHOSPHINOYL)-2-(N -PHENYLHYDRAZINO)ETHANE
1759
zine, 0.3 g, was heated in Wood’s alloy at 150 C for
2 h to obtain 0.3 g of a mixture containing, according
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1
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1
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1
hydrazone identified by the H NMR spectrum of an
authentic sample.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 11 2006