Transformation of 4-nitrobenzyl halides at the action of phosphinates and carboxylic acids orthoesters

Full text of DOI:10.1134/S1070363211070280

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 7, pp. 1564–1565. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © M.B. Gazizov, G.D. Ibragimova, D.B. Bagautdinova, Sh.N. Ibragimov, O.D. Khairullina, 2011, published in Zhurnal Obshchei
Khimii, 2011, Vol. 81, No. 7, pp. 1217–1218.
LETTERS
TO THE EDITOR
Transformation of 4-Nitrobenzyl Halides at the Action
of Phosphinates and Carboxylic Acids Orthoesters
M. B. Gazizov, G. D. Ibragimova, D. B. Bagautdinova,
Sh. N. Ibragimov, and O. D. Khairullina
Kazan State Technological University, ul. K. Marksa 68, Kazan, Tatarstan, 420015 Russia
e-mail: mukattisg@mail.ru
Received February 21, 2011
DOI: 10.1134/S1070363211070280
Previously we studied the reaction of organic gem-
di- and trihalides with methyl esters of P(IV) acids [1]
and trialkyl orthoformates [2]. However, the literature
contains no information on the reaction of the above
reagents with organic monohalides.
respectively, to form 4-nitrobenzyl diethylphosphinate
IV. Apparently, the phosphinate II attacks the me-
thylene carbon of halide I by its more nucleophilic
phosphoryl oxygen. The resulting quasiphosphonium
salt III can be stabilized via the second stage of the
Arbuzov reaction to release methyl halide V and to
form a stable phosphinate IV.
We first discovered that methyl diethylphosphinate
II reacts with halides Ia and Ib at 150 and 180°C,
O
Et
O2N
CH2OP+
O
Me Hlg−
+ Et2POMe
CH2Hlg
O2N
Et
I
II
III
Et
CH2OP
Et
+ MeHlg
O2N
O
V
IV
I, III, V: Hlg = Br (а), Hlg = Cl (b).
4-Nitrobenzyl bromide Ia was found to be sub-
jected to dehaloalkoxylation with triethyl orthoformate
VIa at 220ºC to form 4-(nitrobenzyl) ethyl ether VII.
At the same time its chlorine analog Ib under these
conditions remains inert toward compound VIa. More
nucleophilic triethyl ortoacetate VIb reacts with
bromide Ia under milder conditions (180ºC).
ethyl ether VII and a labile α-bromacetal, which decom-
poses into compound VIII and ethyl bromide IX. It is
assumed that the exchange process begins with an
attack on the electropositive methylene carbon of
compound Ia with the lone electron pair of the oxygen
atom of orthoester VI. The subsequent four-member
cyclic electron transfer leads to the reaction products.
The reaction proceeds through the substitution of
the bromine atom by ethoxy group to form 4-(nitrobenzyl)
A new method for the synthesis of 4-(nitrobenzyl)
ethyl ether VII via the reaction of 4-nitrobenzyl
RC(OEt)
RCOOEt + EtBr
O2N
CH2OEt
+
Iа +
3
VII
VIII
IX
VI
VI, VIII: R = H (а), R = CH3 (b).
1564

TRANSFORMATION OF 4-NITROBENZYL HALIDES AT THE ACTION
1565
bromide Ia with carboxylic acids orthoethers VI has
several advantages over existing methods [3–5]: the
starting materials are commercially accessible, the
reaction proceeds in the absence of any solvent and
catalyst, the treatment is simple, and the reaction
product can be easily isolated.
3.56 g (0.024 mol) of triethyl orthoformate VIа was
kept in a sealed ampule at 220ºС for 18 h and then
distilled. Yield 1.60 g (40%), bp 110ºС (0.2 mm Hg),
1
{bp 134ºС (1.0 mm Hg) [4]}. Н NMR spectrum
3
(acetone-d6, CCl4), δ, ppm: 1.30 t (3H, СН3, JHH
3
7.1 Hz), 3.62 q (2H, CH2, JHH 7.1 Hz), 4.61 s (2H,
CH2), 7.52 d and 8.16 d (4H, C6H4,3JHH = 3JHH = 8.7 Hz).
The reactivity of the compounds I and VI in these
reactions were found to depend on the halogen nature
in compounds Ia and Ib and the structure of the ortho-
esters VIa and VIb. Thus, it was observed that 4-
nitrobenzyl bromide Ia is more active than its chlorine
analogue Ib, and triethyl orthoacetate VIb is more
reactive than triethyl orthoformate VIa towards 4-
nitrobenzyl bromide Ia. The reactions were carried out
in the sealed ampules in a dry nitrogen atmosphere
with heating. The optimal heating temperature was
found by increased internal pressure (due to the alkyl
halide liberation) revealed at the intermittent opening
the ampule to remove the volatile products. The
b. A mixture of 2.16 g (0.010 mol) of 4-nitrobenzyl
bromide Iа and 2.11 g (0.013 mol) of triethyl
orthoacetate VIb was kept in a sealed ampule at 180ºС
for 5 h and distilled. Yield 0.5 g (27%), bp 124ºС
(0.4 mm Hg).
1
The Н NMR spectra were registered on a Tesla
BS-567A spectrometer operating at 100 MHz, internal
referenceTMS. The 31Р NMR spectra were recorded on
a Bruker MSL-400 instrument (162 MHz) relative to
85% Н3РО4.
ACKNOWLEDGMENTS
1
reaction progress was monitored by the H and 31P
NMR spectroscopy.
This work was financially supported by the Federal
Target Program “Research and Scientific-Pedagogical
Personnel of Innovative Russia for 2009–2013” (contract
no. P-1108).
4-Nitrobenzyl diethylphosphinate (IV). а. A mix-
ture of 3.24 g (0.015 mol) of 4-nitrobenzyl bromide Iа
and 4.08 g (0.030 mol) of methyl diethylphosphinate
II was kept in a sealed ampule at 150ºС for 4 h and
then distilled. Yield 1.74 g (45%), bp 133–135ºС
(0.2 mm Hg). 1Н NMR spectrum (acetone-d6, CCl4), δ,
ppm: 0.96–1.38 m (6H, CH3), 2.02–1.48 m (4Н, СН2),
REFERENCES
1. Gazizov, M.B., Kachalova, T.N., Karimova, R.F., and
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3
5.19 d (2H, CH2, JPH 8.1 Hz), 7.69 d and 8.23 d (4H,
3
3
C6H4, JHH = JHH = 8.6 Hz). 31P NMR spectrum: δP
60.4 ppm. Found, %: N 5.10, 4.95; P 12.65, 12.41.
C11H16NO4P. Calculated, %: N 5.45; P 12.04.
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b. A mixture of 2.23 g (0.013 mol) of 4-nitrobenzyl
chloride Ib and 3.54 g (0.026 mol) of methyl diethyl-
phosphinate II was kept in a sealed ampoule at 180ºС
for 5 h and then distilled. Yield 1.58 g (47%), bp 133–
135ºС (0.2 mm Hg).
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4. Wahl, H. and Abdallah, M., Bull. Soc. Chim., 1969,
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4-Nitrobenzyl ethyl ether (VII). а. A mixture of
4.76 g (0.022 mol) of 4-nitrobenzyl bromide Iа and
5. Yang, M.S., Xu, L.I., Qiu, H.Y., Lai, G.Q., and Jiang, J.X.,
Tetrahedron Lett., 2008, vol. 49, no. 2, p. 253.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 7 2011