Reaction of 10-methyl(phenyl)-5,10-dihydrophenarsazine 10-oxides with hydriodic acid

Article abstract of DOI:10.1023/B:COHC.0000048297.35826.d3

We have studied the reaction of 10-methyl(phenyl)-5,10-dihydrophenarsazine 10-oxides with hydriodic acid and we have established the structure of the products by high-resolution mass spectrometry. We have shown that when the methyl group is replaced by a phenyl group in 5,10-dihydrophenarsazine 10-oxides, cleavage of the endocyclic arsenic-carbon bonds occurs. 2004 Springer Science+Business Media, Inc.

Full text of DOI:10.1023/B:COHC.0000048297.35826.d3

Chemistry of Heterocyclic Compounds, Vol. 40, No. 9, 2004
REACTION OF 10-METHYL(PHENYL)-
5,10-DIHYDROPHENARSAZINE 10-OXIDES
WITH HYDRIODIC ACID
V. I. Gavrilov1, A. A. Karavanov1, R. R. Musin1, F. R. Garieva1, and R. Z. Musin2
We have studied the reaction of 10-methyl(phenyl)-5,10-dihydrophenarsazine 10-oxides with hydriodic
acid and we have established the structure of the products by high-resolution mass spectrometry. We
have shown that when the methyl group is replaced by a phenyl group in 5,10-dihydrophenarsazine
10-oxides, cleavage of the endocyclic arsenic–carbon bonds occurs.
Keywords: hydriodic acid, 10-methyl-5,10-dihydrophenarsazine 10-oxide, 10-phenyl-5,10-dihydro-
phenarsazine 10-oxide, mass spectra.
When 10-alkyl-5,10-dihydrophenarsazine 10-oxides 1 and 10-aryl-5,10-dihydrophenarsazine 10-oxides
2 react with hydrochloric, hydrobromic, trichloroacetic acids, and pentachlorophenol, only protonation at the
oxygen atom occurs with formation of addition products in salt form ≡AsO···HX [1].
In the case of hydriodic acid, we have observed [2] rather facile cleavage of the arsenic–carbon bond.
Thus upon heating in an alcohol–water medium, as the major product of reaction between As oxides 1 and HI
we identified 10-iodo-5,10-dihydrophenarsazine (3), while in the case of As oxides 2 we identified
diphenylamine (4) (see reactions (1) and (2)).
Alk
As
I
(1)
As
HN
HN
HI
+
O
3
1
Ar
(2)
As
HN
HN
HI
+
O
4
2
__________________________________________________________________________________________
1
2
Kazan State Technical University, Kazan 420015, Russia; e-mail: toons@kstu.ru. A. E. Arbuzov
Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, Kazan
420088; e-mail: musin@iopc.kcn.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1396-
1399, September, 2004. Original article submitted January 7, 2002; revision submitted January 22, 2003.
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0009-3122/04/4009-1212©2004 Springer Science+Business Media, Inc.

The goal of this work was to study the mechanism of the process, using as an example the reaction of
10-methyl-5,10-dihydrophenarsazine 10-oxide (1a) and 10-phenyl-5,10-dihydrophenarsazine 10-oxide (2a) with
HI. The synthesis was carried out according to the procedure described in [2]. We used high-resolution mass
spectrometry to study the starting compounds, the reaction mixtures, and the isolated products (Table 1).
Based on the mass spectrometric data obtained, we can hypothesize that reaction of compounds 1a and
2a with HI occurs according to the scheme presented below.
In the first step of the reaction, protonation of the oxygen atom on the tetracoordinated arsenic atom
occurs, with formation of arsonium cations 5, which then are reduced to form the tertiary arsines 6 and 7.
Oxidation of the latter by iodine in an alcohol–water medium has been well studied [3], and is a reversible
process. In reaction of 10-methyl-5,10-dihydrophenarsazine 10-oxide (1), the arsonium cation 5 (R = Me)
formed in the first step as a result of attack by the iodide anion according to an SN2 mechanism can be converted
to 10-hydroxy-5,10-dihydrophenarsazine (8), which when treated with HI gives compound 3; reaction (1) does
not occur for compound 2.
Dihydrophenarsazine 6 or 7 formed in the first step then is protonated at the benzene ring of the
5,10-dihydrophenarsazine system, where the endocyclic arsenic–carbon bonds are broken to form diphenylamine
(4) and methyldiiodoarsine (9) or diphenylamine and phenyldiiodoarsine (10).
+ HI
I
C
3
As OH
HN
As
HN
–H2O
–MeI
OH
8
_
+I
_
R
O
R
+
+ 2HI
+
As
I
HI
As
HN
As
R
+
H2O + I2
HN
HN
+
OH
1a,2a
6, 7
5
+
H
+
H
_
_
+
R
R
I
+H
+ I
+ I
RAsI2
4
As
R
+
HN
As
HN
As
+
HN
I
9,10
H
1a, 5, 6, 9 R = Me, 2a, 7, 10 R = Ph
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TABLE 1. Components of Filtrates for Reactions (1) and (2) (From Mass
Spectrometry Data)
Molecular ion*
Reaction
empirical formula
m/zfound
m/zcalc
(1)
HI
127.9107
368.8990
141.9270
253.8094
169.0928
343.7624
257.0174
127.9123
368.8996
141.9280
253.8090
169.0892
343.7541
257.0186
C12H9AsIN (3)
CH3I
I2
C12H11N (4)
CH3AsI2 (9)
C13H12AsN (6)
(2)
C18H14AsNO (2a)
HI
335.0263
127.9129
253.8043
169.0804
405.7643
319. 0387
335.0291
127.9123
253.8090
169.0892
405.7697
319.0342
I2
C12H11N (4)
C6H5AsI2 (10)
C18H14AsN (7)
_______
* Ion peaks containing the most abundant isotopes are indicated.
EXPERIMENTAL
The mass spectra were obtained on an MX 1310 spectrometer with ionizing electron energy of 70 eV,
electron collector current of 30 µA. The substance was injected directly into the ion source by the SVP-5 direct
injection system at 120°C. The exact values of the masses were determined automatically from the reference
peaks of perfluorokerosene with 15000 resolution.
The Reaction of 10-Methyl-5,10-dihydrophenarsazine 10-Oxide with Hydriodic Acid was carried
out according to the procedure in [2]. 50% Hydriodic acid (d = 1.56 g/cm3) (4.5 ml, 27.4 mmol), purified by
distillation over mercury to remove traces of iodine, was added to solution of 10-methyl-5,10-
dihydrophenarsazine 10-oxide (1a) (2.01 g, 7.5 mmol) in ethanol (40 ml). The mixture was boiled for 4 h and
then the solvent was distilled off to 1/5 of the initial volume. The precipitate formed upon cooling was filtered
off and, after recrystallization from 1-propanol, was dried at 20-30 mm Hg above P2O5. Yield of compound 3
was 1.65 g (61%); mp 218-219°C (219-221°C [4]). The mass spectrum corresponded to 10-iodo-5,10-
dihydrophenarsine (3) [5]. Mass spectrum, m/z (Irel, %), composition of [M+·] ion: 369 (2.7), 242 (100.0), 214
(0.5), 167 (20.5), 166 (8.0), 151 (1.2), 139 (3.6), 125 (0.8), 113 (0.7), 77 (1.5). The filtrate was studied by mass
spectrometry (Table 1).
Reaction of 10-Phenyl-5,10-dihydrophenarsazine 10-Oxide with Hydriodic Acid. Hydriodic acid
(50%, 2.3 ml, 14.0 mmol) was added to solution of 10-phenyl-5,10-dihydrophenarsazine 10-oxide (2a) (1.00 g,
3.1 mmol) in ethanol (60 ml). The mixture was boiled for 4 h and then the solvent (3/4 of volume) was distilled
off. The residue was dissolved in acetone (30 ml) and treated with a mixture of solution of potassium hydroxide
(1.57 g) in water (100 ml) and benzene (100 ml) and then filtered; the benzene layer was removed and dried with
anhydrous calcium chloride. The residue after distilling off the solvent, recrystallized from aqueous ethanol
(1:1), has mp 53°C (compare with literature data in [6]). Yield 0.20 g (39%). The mass spectrum corresponds to
diphenylamine. Mass spectrum, m/z (Irel, %), composition of the ion: 170 (12.2), 169 (100.0) [M+·], 168 (47.3),
167 (28.1), 166 (6.1), 77 (11.2), 66 (9.5), 65 (7.1), 51 (13.8), 39 (7.3). The filtrate was studied by mass
spectrometry (Table 1).
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2.
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4.
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V. Shpanskii, Zh. Obshch. Khim., 4, 658 (1934).
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V. P. Nikol'skii (editor), The Chemist's Handbook [in Russian], Khimiya, Moscow (1971), Vol. 2,
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