New reaction of benzylidene chloride with trialkyl orthoformates

Full text of DOI:10.1023/A:1012928708045

Doklady Chemistry, Vol. 381, Nos. 1–3, 2001, pp. 321–323. Translated from Doklady Akademii Nauk, Vol. 381, No. 2, 2001, pp. 207–209.
Original Russian Text Copyright © 2001 by M. Gazizov, K. Gazizov, Pudovik, Mukhamadiev, Karimova, Sadykova, Sinyashin.
CHEMISTRY
New Reaction of Benzylidene Chloride with Trialkyl
Orthoformates
M. B. Gazizov, K. M. Gazizov, M. A. Pudovik, A. A. Mukhamadiev, R. F. Karimova,
A. I. Sadykova, and Corresponding Member of the RAS O. G. Sinyashin
Received July 25, 2001
Alkali-metal alcoholates [1] and methyl esters of
phosphorus(IV) acids [2, 3] are known to be used for
dehaloalkoxylation of organic gem-polyhalides. The
final products of these reactions are carbonyl-contain-
ing compounds and their derivatives, which play an
important role in organic synthesis. Highly reactive
inorganic gem-polyhalides, for example, P(III) and
Si(IV) halides, readily undergo dehaloalkoxylation
with orthoesters [4]. However, there is no data in the lit-
erature on the use of the latter in reactions with much
less reactive organic gem-polyhalides.
In this paper, we describe a new reaction between
benzylidene chloride (I) and trialkyl orthoformates (II)
to form, depending on reagent ratio (1 : 2.2 or 1 : 1) and
temperature conditions (225 or 237°C), benzaldehyde
or its acetals, which have been isolated in their individ-
ual states in good yields. The reactions of acetal V with
compound I, as well as α-chloroether III with trialkyl
orthoformates, have been carried out experimentally
for the first time. A general scheme for the reaction of
benzylidene chloride with trialkyl orthoformates has
been suggested.
V + I
PhCHO + VII,
VIII)
2III,
III
(
II. R = Me (‡), Et (b).
The formation of a marked amount of alkyl benzoate
IX) also attracted our attention.
(
To reveal optimal reaction conditions, we used
1
dynamic H NMR spectroscopy. The spectra were
recorded every 6 h, with volatile compounds VI and
VII being removed from the reaction mixture after
sampling and before the ampule was sealed. Alteration
in the integrated intensities of the following resonance
signals of initial reactants and reaction products was
monitored (δ, ppm): PhCHCl , 6.7 (s, CHCl );
2
2
HC(OMe) , 4.8 (s, CH), 3.13 (s, Me); PhCH(OMe) ,
.3 (s, CHO ), 3.2 (s, Me); PhCHO, 9.95 (s, CHO);
3
2
5
2
HCOOMe, 7.95 (s, CH), 3.6 (s, Me); MeCl, 2.88 s;
PhCOOMe, 3.8 (s, Me). The reaction between com-
pounds Ia and IIa was found to proceed slowly at
1
80°C, but its rate increased noticeably above 220°C.
A mixture of compounds I and II in 1 : 1 or 1 : 2.2
The table presents reaction conditions and the yields of
products I, II, V, VIII, and IX. The heating of a mixture
of reagents I and IIa for 28 h at 225°C (in the ratio of
ratios was heated in a sealed ampule. The structure of
1
reaction products was established by H NMR spectros-
copy, while the reaction mixture composition was
determined by gas chromatography. The major prod-
ucts of the reaction were found to be dialkyl acetal (V),
alkyl formate (VI), alkyl halide (VII), and benzalde-
hyde (VIII):
1
: 2.2) leads mainly to acetal Va. When heating time
was increased to 39 h, compounds I and IIa were com-
pletely consumed and only a negligible amount of ben-
zaldehydeVIII was detected in the reaction mixture. Its
content in the mixture increases considerably if the
reaction is carried out at 237°C.
PhCHCl + HC(OR)3
PhCH(OR)Cl + HC(OR) Cl,
2
2
Upon heating a mixture composed of compounds I
and IIa in a 1 : 1 ratio at 225°C for 28 h, the orthofor-
mate reacts completely, and the ratio of resultant acetal
Va and initial benzylidene chloride is 0.95 : 1.0. When
the resulting reaction mixture was heated at 237°C for
(
I)
(II‡, IIb)
III + II
(III)
(IV)
PhCH(OR) + IV,
2
(
V)
HCOOR + RCl,
VI) (VII)
1
IV
14 h, H NMR spectrum shows no signals at δ 5.3 and
3
.2 ppm from acetal Va. Benzaldehyde becomes the
(
main component of the reaction mixture, although the
products I, VIa–VIIa, and IXa are also present in dif-
ferent amounts. Benzaldehyde is the main reaction
Kazan State Technological University, ul. Lenina 18, Kazan, product if a 1 : 1 mixture of compounds I and IIa is
4
20008 Tatarstan, Russia
Arbuzov Institute of Organic and Physical Chemistry,
ul. Lenina 18, Kazan 8, 420008 Tatarstan, Russia
directly heated at 237°C for 24 h, but negligible quan-
tities of benzylidene chloride and acetal Va also remain
unspent.
0
012-5008/01/0011-0321$25.00 © 2001 åÄIä “Nauka /Interperiodica”

3
22
GAZIZOV et al.
Table
Reaction
tempera-
ture, °C
Content of products
Initial
reagents
Initial
reagent ratio
Heating
duration, h
I
II
V
VIII
IX
I + IIa
1 : 2.2
225
225
237
237
237
28
39
24
10
14
5.7
0.0
3.4
2.1
1.0
7.9
0.0
0.0
–
71.0
80.5
5.2
0.0
0.3
11.4
14.44
13.1
8.5
1
1
: 2.2
: 1
75.1
88.0
90.1
I + Va
1 : 1
: 1
1.4
1
–
0.0
8.8
The above experimental data indicate that the reac-
Benzaldehyde dimethyl acetal (Va). A. A mixture
tion leads only to acetal V at 225°C and the reagent of 15 mmol of benzylidene chloride and 33 mmol of
ratio of 1 : 2.2, whereas at 237°C and a 1 : 1 reagent orthoformate IIa was heated in a sealed ampule for
ratio, the reaction of resultant compound V with ben- 39 h at 225°C. The reaction mixture was fractionated
zylidene chloride results in benzaldehyde. The sepa- with a distilling column to give 1.75 g (76%) of acetal
rately studied reaction between compounds I and V
also leads to the formation of product VIII.
We believe that a substitution of an alkoxy group for
the chlorine atom in benzylidene chloride takes place at
the first stage of the reaction. The resulting α-chloroet-
her III further undergoes an exchange reaction with tri-
alkyl orthoformate to give acetal V. Chloroacetal IV (12 mmHg), n 1.5005.
decomposes into alkyl formate VI and alkyl chloride
VII [4]. Under more severe temperature conditions,
acetal V behaves as a dechloroalkoxylating agent
toward benzylidene chloride. Under conditions where
there is a shortage or absence of trialkyl orthoformate,
α-chloroether III undergoes thermal decomposition to
20
Va, bp 83–84°C (12 mmHg) and 208–209°C, nD
.5010 (lit.: bp 208°C [7]). B. A mixture of 54 mmol of
1
orthoformate IIa and 49 mmol of compound IIIa was
kept for 24 h at 20°C. Distillation of the reaction mix-
ture afforded 5.39 g (72%) of acetal Va, bp 82–84°C
2
0
D
Benzaldehyde diethyl acetal (Vb). A. A mixture of
5 mmol of compound I and 33 mmol of orthoformate
IIb was heated for 40 h at 225°C. Distillation gave 2.17 g
1
2
0
(80%) of acetal Vb, bp 87–88°C (10 mmHg), n
D
2
0
yield benzaldehyde and alkyl chloride [5]. Compound 1.4842 (lit.: bp 217–221°C, n 1.4843 [7]. B. A mix-
D
IX seems to form upon thermal decomposition of acetal
V [6].
ture of 12.1 mmol of orthoformate IIb and 12 mmol of
compound IIIb was kept for 24 h at 20°C to yield
No data were reported in the literature on the reac- 1.52 g (70%) of acetal Vb, bp 87–88°C (10 mmHg),
2
D
0
tion of α-haloethers with trialkyl orthoformates. We
have established that the reaction of compounds II and
III occurs at room temperature to produce acetal V and
products VI and VII. It becomes understandable why
only acetal V is formed at a 1 : 2.2 ratio of reagents I
and II and why only a trace amount of benzaldehyde is
detected in the reaction mixture.
n
1.4839.
Benzaldehyde (VIII). A. A mixture of 20.75 mmol
of compound I and 20.75 mmol of orthoformate IIa
was heated for 24 h at 237°C. Distillation gave 1.63 g
(
74%) of benzaldehyde VIII, bp 70–71°C (14 mmHg),
2
0
20
n
1.5430 (lit.: bp 62°C (10 mmHg), nD 1.5463 [8].
D
B. The above mixture was heated for 28 h at 225°C and
4 h at 237°C to give 1.58 g (72%) of benzaldehyde, bp
EXPERIMENTAL
1
1H NMR spectra were recorded on Bruker WP-80 70–71.5°C (14 mmHg). C. A mixture of 10.16 mmol of
and Tesla BS-567A spectrometers at 80 and 100 MHz, compound I and 11.17 mmol of acetal Va was heated
respectively. Proton chemical shifts are given relative to for 14 h at 237°C to produce 0.92 g (85%) of benzalde-
TMS. Chromatographic analysis of reaction mixtures hyde, bp 70–71°C (14 mmHg).
was carried out on a Tsvet-500 chromatograph. Chro-
matography conditions: injector temperature 180°C,
column temperature 120°C, detector temperature
REFERENCES
2
00°C, 30 mL/min carrier gas flow rate, flame ioniza-
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. Guben, I., Metody organicheskoi khimii (Methods of
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bowax) as liquid phase. Peak identification was per-
formed by retention time in seconds: PhCHCl 282,
2
PhCOOMe 223, PhCHO 172, PhCH(OMe)2 150,
2. Gazizov, M.B., Kachalova, T.N., Karimova, R.F., and
Sinyashin, O.G., Dokl. Akad. Nauk, 1998, vol. 359,
no. 5, pp. 644–646.
HC(OMe) 38, HCOOMe + MeCl 33. Experiments
3
were carried out under dry nitrogen atmosphere.
DOKLADY CHEMISTRY Vol. 381 Nos. 1–3 2001

NEW REACTION OF BENZYLIDENE CHLORIDE
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DOKLADY CHEMISTRY Vol. 381 Nos. 1–3 2001