An unusual synthesis of arylazo substituted azaphospha [5, 1-A] quinolines by reaction of N-alkylarylazo quinolinium salts with phosphorus trichloride

Article abstract of DOI:10.1080/10426500307935

1,2-Dialkyl-3-arylazo quinolinium chloride 1 having N-methylene group activated by the insertion of arylazo site react with phosphorus trichloride to give N-(dichloro phosphinomethylene) quinolinium ylide 2. The site of the reaction is determined by the r

Full text of DOI:10.1080/10426500307935

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An Unusual Synthesis of Arylazo Substituted
Azaphospha [5, 1-A] Quinolines by Reaction of N-
Alkylarylazo Quinolinium Salts with Phosphorus
Trichloride
Pratibha Sharma a , Ashok Kumar a & Priti Pandey a
a Devi Ahilya University , Indore, India
Published online: 27 Oct 2010.
To cite this article: Pratibha Sharma , Ashok Kumar & Priti Pandey (2003) An Unusual Synthesis of Arylazo Substituted
Azaphospha [5, 1-A] Quinolines by Reaction of N-Alkylarylazo Quinolinium Salts with Phosphorus Trichloride, Phosphorus,
Sulfur, and Silicon and the Related Elements, 178:3, 583-594
To link to this article: http://dx.doi.org/10.1080/10426500307935
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Phosphorus, Sulfur and Silicon, 2003, Vol. 178:583–594
C
Copyright 2003 Taylor & Francis
1042-6507/03 $12.00 + .00
DOI: 10.1080/10426500390170732
AN UNUSUAL SYNTHESIS OF ARYLAZO
SUBSTITUTED AZAPHOSPHA [5, 1-A] QUINOLINES
BY REACTION OF N-ALKYLARYLAZO QUINOLINIUM
SALTS WITH PHOSPHORUS TRICHLORIDE
Pratibha Sharma, Ashok Kumar, and Priti Pandey
Devi Ahilya University, Indore, India
(Received May 10, 2002; accepted August 12, 2002)
1,2-Dialkyl-3-arylazo quinolinium chloride 1 having N-methylene
group activated by the insertion of arylazo site react with phospho-
rus trichloride to give N-(dichloro phosphinomethylene) quinolinium
ylide 2. The site of the reaction is determined by the relative activation
of 1- and 2-methylene groups, in the absence of sufficient activation of
N-methylene group, reactions occur at the 2-methylene group to give
dichloro phosphinylated anhydrobases 5 and 11.
Keywords: 1-Alkyl-2-(dichlorophosphinomethylene) quinolinium an-
hydrobases; 2,4,6-trialkyl-3-arylazo quinolines; N-alkyl quinolinium
halides; N-(dichloro phosphino methylene) quinolinium ylides
Anullated heterophospholes1 6 constitute a special class of heterocyclic
compound in which a phosphole ring is fused with an aromatic nu-
cleus to generate a 4n+2 electron system. The synthesis of anullated
heterophosphole manifests the mechanism for investigating the reac-
tion of various substituted N-alkyl quinolinium salt with PCl3 in pres-
ence of triethylamine to investigate the role of sufficiently activated
N-methylene group, which undergoes cyclization and results in the for-
mation of 1,3-azaphospholoquinolines. The literature7 has shown that
such attempts on N-alkyl quinoline could not be successful in reveal-
ing the desired product, however similar reaction sequence on N-alkyl
isoquinolinium salts have been found to be fruitful and resulted in the
formation of azaphospholo isoquinolines.
Our sincere thanks are due to Prof. R. K. Bansal, University of Rajasthan, Jaipur for
many helpful suggestions.
Address correspondence to Pratibha Sharma, School of Chemical Science, Devi Ahilya
University, Indore 452-017, India. E-mail: drprathibhasharma@yahoo.com
583

584
P. Sharma et al.
We sought to control the difficulty associated with quinoline nucleus
and rectified the problem by inserting an arylazo grouping in the
3-position and thereby activating the nuclei to undergo anullation
under optimal conditions. The developed methodology delineates the
[4 + 1] cyclocondensation of 2-substituted cycloiminium salts with
phosphorous trichloride in the presence of triethylamine.8 It has
been realized that if the N-methtylene group was not sufficiently
activated, either the reaction stopped at the intermediate stage or
only 1-dichlorophosphino substituted-2-phospholoquinolines could be
generated. For example 1-benzyl-2-methyl quinoline bromide formed
an intermediate which did not cyclize to give the corresponding
azaphospholoquinolines under the given reaction conditions,
whereas 2-methyl-1-(4-methoxy benzyl) quinolinium bromide
under these conditions gave a very poor yield ( 10%) of 1-
unsubstituted 2-phosphaquinolines, though the corresponding
1-dichloro phosphino-2-phosphaquinolines could be generated quanti-
tatively. It was inferred that 1-dichlorophosphino-2-phosphaquinoline
was formed from the substitution of the initially formed 2-
phosphaquinolines. Characterization of the isolated reaction in-
termediate as 1-(dichlorophosphinomethylene) quinolinium ylide gave
the impression that the reaction always initiated at the N-methylene
group.
Buoyed from these encouraging results and keeping in view the anal-
ogy of Kro¨hnke’s synthesis of indolizines9 with our 2-phosphaquinolines
an inspiration has been aroused to investigate the reaction of differ-
ently substituted N-quinolinium salts with phosphorus trichloride. It
has been realized that cyclization to 2-phosphaquinolines occurs only
if the N-methylene group is quite activated; the reaction may be initi-
ated at either of the two terminal methylene groups depending on their
relative activation.
RESULTS AND DISCUSSION
Reaction of 2-Nonalkyl Substituted 1,4-Dialkyl
Quinolinium Bromides
Reaction of 2-hydroxy 1,4-dialkyl quinolinium bromide (1)
(R0 = COOCH3, COOC2H5, COC6H5) with phosphorus trichloride
in the presence of triethylamine at room temperature gives 1-(dichloro
phosphino methylene) quinolinium ylides (2) (Scheme 1).
1-Benzyl and 1-(4-methoxy benzyl) quinolinium bromides do not
show any reactivity under these conditions. This indicates that in the

Unusual Synthesis of Arylazo Substituted Azaphospha [5, 1-A] Quinolines
585
SCHEME 1
above reaction the quinolinium salt with an activated N-methylene
group undergoes deprotonation in the presence of trioethylamine
to generate the N-quinolinium ylide which reacts with phosphorus
trichloride to form 2. This analogy has been derived from the alkylation
of N-pyridinium ylides.10 Compounds 2a,b are isolated in a pure state
as orange crystalline solids. The 2c, however could not be separated
from the ammonium salt due to its insolubility in diethyl ether.
1
The structure of 2 has been ascertained on the basis of 31P and H
NMR spectroscopic data (Table I). The 31P-NMR chemical shift at 152
agrees well with those reported for dichloro phosphino derivatives.11
The ylidic nature of 2 is supported by the absence of any 1H-NMR signal
in the range 6–7 characteristics for the proton on the ylidic carbon of
N-quinolinium ylides.12 Similar evidences have been obtained
upon identical treatment on 1-alkyl-2-4-diethoxy-3-arylazoquinolinium
halide (1 d–f) which gives (1-dichloro phosphinomethylene)-2,4-
diethoxy derivative under similar reaction conditions 2d–f (Scheme 2).
Reaction of 1,2,4–Trialkyl Quinolinium Halide
1-Alkyl-2, 4-dimethyl quinolinium halides (3) (R1 H, C6H5, C6H4
OCH3 p) react with phosphorus trichloride (2 equv.) in presence of tri-
ethylamine (3 equn.) in benzene at room temperature to give 1-alkyl-2,-
[bis(dichlorophosphino)methylene] 4-methyl-1,2-dihydro quinoline (5)
(Scheme 3).
Compounds 5a,b are orange amorphous solids, highly sensi-
tive to moisture, and are soluble in common organic solvents. Its

586
P. Sharma et al.
SCHEME 2
characterization as the bis dichlorophosphino derivative is supported
by elemental analysis and NMR spectroscopy (Table I). The 31p-NMR
signal at
146 does not split under the proton coupled mode show-
ing the absence of any proton on 2-methylene carbon. In the 13C-NMR
spectrum (Table II) of 5b, the signal of 2-methylene carbon appears
as a triplet at 86.5 (1Jpc = 75.6 Hz) indicating the presence of two
dichlorophosphino moities on this carbon. The C-2 also gives a triplet
at 161.4 (2Jpc = 15.1 Hz).
SCHEME 3

Unusual Synthesis of Arylazo Substituted Azaphospha [5, 1-A] Quinolines
587
TABLE I Physical and Spectra Characteristics of Some Reaction Products
Yield
%
Molecular
formula
Compound
R1
m.p. C
1H-NMR1 ppm (J, Hz)
2a
(R H)
COOCH3 151–152 65 C21H22N3O4PCl2 3.50 (s, 3H, OCH3)
1.1 (t, 6H, CH3 2)
4.1 (q, 4H, CH2 2)
6.65 (t, 3JHH = 7.5,
2H; 30-1H, 5-H) 7.1 (t,
3JHH = 8.0, 1H, 4-H)
7.30 (d, 3JHH = 7.4,
2H; 21-H, 61-H)
7.50–8.10 (m, 4HH, Ar-H)
COOC2H5 126–127 62 C22H24N3O4PCl2 0.95 (t, 6H, CH3 2),
3.95 (q, 4H, OCH2 2),
2b
(R H)
6.95 (d, 3JHH = 7.5, 2H;
5H, 8H) 6.75 (t, 3JHH = 8.1,
2H, 6H, 7H), 7.40
(t, 3JHH = 7.8, 2H, 31H,
5H) 7.55 (t, 3JHH = 8.0,
1H, 41-H). 7.85 (d, 3JHH
7.5, 2H; 20H, 6H).
=
2c
COC6H5 115–116 55 C27H24N3O3PCl2 1.0 (dt, 6H, CH3 2) 4.5 (q,
(R H)
4H, CH2 2) 7.0–7.2
(t, 3JHH = 7.5, 3H1,
30-H, 40-H, 50-H), 7.5–7.7
(d, 3JHH = 7.8, 2H,
21-H, 60-H) 7.9–8.2 (m,
9H; Ar’-H).
5a
R2
H
140–141 60
C16H15N3P2Cl4 3.4 (s, 6H; CH3 2), 7.8
(d, 3 JHH = 6.6, 20-H, 60-H),
6.95–7.2 (t, 3JHH = 7.1,
3H, 30-H, 40=H, 50-H)
H
7.32–7.40 (t, 3JHH=7.8.
2H, 6-H, 7-H) 7.50–7.65
(d, 3JHH = 8.0, 2H; 5-H,
8-H)
5b
(R2 H)
C6H5
161–162 62
135–136 60
C22H19N3P2Cl4 2.4 (s, 3H, CH3), 4.5 (s,
2H, CH2) 7.30–7.95 (m,
14H; Ar-H)
C16H20N3PCl2 2.4 (s, 6H, CH3 2),
7.4–8.1 (m, 14H; Ar-H)
11a
H
14a
C6H5
110–111 55 C24H25N3O2P2Cl4 1.1 (t, 6H; CH3 2) 4.4
(q, 4H, CH2 2) 3.8 (S,
2H, CH2 ) 6.75–7.15
(t, 3JHH–7.0, 3H, 30-H,
40-H, 50-H), 7.30 (s, 5H,
Ar-H), 7.85 (s, aromatic
CH) 7.50–7.70 (d, 3JHH
7.6, 2H; 7-H, 8-H)
=

588
P. Sharma et al.
These results indicate that if the N-methylene group is not acti-
vated, deprotonation of the 2-methylene group is preferred as the re-
sulting anhydrobase is stabilized by resonance.7 The initially formed
monodichlorophosphino derivative 4 could not be isolated even on
using one equivalent of phosphorus trichloride under controlled con-
dition. This shows that the methine proton of 4 is highly activated and
undergoes instantaneous substitution by phosphorus trichloride.
The polarity of the solvent influences the progress of the above reac-
tion. In nonpolar solvents such as benzene, toluene the reaction stops
at stage 5, whereas in polar solvents viz, acetonitrile, ethylacetate the
initially formed bis(dichlorophosphino) methylene derivative 5 under-
goes intra molecular cyclocondensation if R C6H5 or C6H4OCH3-p to
form species (6) and finally 1-dichloro-phosphino-2-phospha (5, 1-a)
quinoline (7) (Scheme 4). The formation of species 6 is revealed by 31P-
NMR spectrum of the reaction mixture in which two doublets ( PA
=
25–40, PB = 140–170) corresponding to a characteristics AB spin sys-
tem are observed.
Furthermore in the case where R C6H5, the initially formed, 7b
undergoes disproportionation to form 9b (Scheme 5) as revealed by
TABLE II 13C-NMR Data of 5b (CDCl3 + DMF d6, J = Hz)
C-2
161.4
15.1
171.4
6.1
C-i
138.4
4.8
130.4
155.6
9.6
2JPC
C-3
2JCH
C
O
3JPC
1JCH
2JCH
C-4
135.5
C
m
135.4
131.3
10.6
1JCH
2JCH
C-5
131.2
169.7
6.5
128.5
165.5
8.6
1JCH
2JCH
C-6
C
P
138.6
148.5
7.9
1JCH
2JCH
1JCH
2JCH
P
P
C-7
126.1
148.6
6.4
155.5
173.4
7.5
2-C
86.5
75.6
<
1JCH
2JCH
C-8
1JPC
1JCH
2JCH
C-9
C
CH3
CH2
15.8
139.1
150.5
C-10
N
60.2
155.5
1JCH

Unusual Synthesis of Arylazo Substituted Azaphospha [5, 1-A] Quinolines
589
SCHEME 4
A2B spin system in the 31P-NMR spectrum. A highly downfield shift of
2
PA in 9b ( 31P = 315, Jpp = 32 Hz) indicates the presence of cationic
charge on the ring system. The ionic nature of 9b is also supported by
its insolubility in diethyl ether to which it could not be separated from
the ammonium salt.
Furthermore, a reinvestigation of the synthesis of 1,3-diphenyl
derivative from the cyclocondensation of 1,2-dibenzyl quinolinium bro-
mide with phosphorus trichloride indicates that in this case the reaction
also is initiated at the 2-methylene group. The reaction of 2-benzyl-1-
methyl salt (10b) with phosphorus trichloride in presence of triethy-
lamine in benzene, gives 11a which does not cyclize on heating on carry-
ing out the reaction in acetonitrile (Scheme 6). The structure of 11a has
been confirmed on the basis of 31P and 1H-NMR spectra (Table I). Like-
wise, 1,2-dibenzyl substituted compound forms 11b in benzene, which
does not cyclize to 2-phosphaquinoline under these conditions. How-
ever, if the reaction is carried out in acctonitrile the initially formed
11b changes into 2-phosphaquinoline (12b) ( 31P = 118.5).
Typically 1-benzyl-3-arylazo-2,4-diethoxy-6-methyl-quinolinnium
bromide (13) reacts with phosphorus trichloride (2 equv.) in presence of
triethylamine (3 equv.) to give 1-benzyl-3-arylazo-2,4diethoxy-6-[bis(di

590
P. Sharma et al.
SCHEME 5

Unusual Synthesis of Arylazo Substituted Azaphospha [5, 1-A] Quinolines
591
SCHEME 6
SCHEME 7
chloro phosphino) methylene] quinoline (14) (Scheme 7) as yellow
crystalline compound.
EXPERIMENTAL
All the reported melting points were determined in an open capillary
and are uncorrected. Solvents and reagents were distilled and dried by
standard procedure before use. NMR Spectra were recorded on a Gemini

592
P. Sharma et al.
TABLE III 31P-NMR Data of Some
Synthesized Quinolines
Compound
PA
PB
2JPP (Hz) Solvent
CDCl3
2a
4a
5a
6b
6c
7b
7c
9b
11a
11b
12b
14
148.2
171.5
145.5
29.5
—
—
—
—
168.6
98.1
135.5
125.0
32.5
DMSO
CH3CN
CDCl3
DMSO-d6
CH3CN
CH3CN
CDCl3
C6H6
165.0
148.0
152.0
165.3
253.0
39.5
138.5
146.1
275.5
172.4
168.6
125.0
156.5
C6H6
C6H6
C6H6
200 MHz (1H and 31P) and Bruker DR X 300 MHz (13C) Spectrometers.
Chemical shift are given with respect to 85% H3PO4(31P) as external
and TMS (1H and 13C) as internal standards.
2,4,6-Trialkyl-3 Arylazoquinoline 4-arylamino-3-arylazo butane-2-
one10,11 (0.032 M) or 3-arylamino-1,3-diethoxy-propanone (0.032 M) was
added in portion to 25.0 ml of concentrated sulphuric acid contained in
a 250 c.c. conical flask. The mixture was occasionally swirled to en-
sure thorough mixing. The reaction mixture was heated on the steam
bath for 30 min, and then cooled to room temperature and slowly added
to 250 ml of ice cold water in a 1 litre beaker. To the solution solid
sodium carbonate was added until it became alkaline. The mixture was
cooled down in an ice water bath until the quinoline solidifies. The prod-
uct was filtered and washed with a little cold water. The purity of the
quinoline thus obtained was ascertained after recrystallization from hot
ethanol.
N-Alkyl Quinolinium Halide (1,3,10,13):
General Procedure
To a solution of ethyl halide (0.1 M) in tetra hydrofuran or di ethyl
ether (50.0 ml) an equimolar amount of pre synthesized quinoline or
alkyl quinoline was added and reaction mixture was stirred for 24–
48 h at room temperature. The precipitate was filtered, washed with di
ethyl ether (25 ml), and dried in vacuum. The salt obtained in 75–80%
yield were used without further purification.
1a (R H) (% Found C 73; H 5.75; N 15.10 Calculated for C17 H16 N3;
C 73.09; H 5.80; N 15.19%).

Unusual Synthesis of Arylazo Substituted Azaphospha [5, 1-A] Quinolines
593
1-(Dichlorophosphino Methylene) Quinolinium Ylide2):
General Procedure
To a well stirred suspension of 1-alkyl quinolinium bromide(1) (0.01 M)
in benzene (30 ml) at room temperature was added triethylamine
(2.02 g, 0.02 M) followed by the addition of a solution of phosphorus
trichloride (1.37 g, 0.01 M) in benzene (10 ml). The reaction was com-
pleted in 5–6 h as revealed by 31P–NMR. The solvent was there after
removed in vacuum and the residue was extracted with di ethyl ether
(2 25 ml) The combined extracts were concentrated to about 25 ml
and left in refrigerator overnight when yellowish to orange red crys-
tals deposited, which were filtered and dried in vacuum. The 2c and 2f,
however, could not be obtained in pure form due to its poor solubility
in diethyl ether. A sample directly obtained from the benzene filtrate
by removal of the solvent was found to contain traces of the ammonium
salt.
2a (R H) (% Found C 52.10; H 4.45; N 8.65; Calc, for C21 H22N3O4,
PCl2; C 52.28; H 4.56; N 8.71%).
2b (R H) (% Found C 2.95; H 4.82; N 8.42; Calc for C22 H24 N3 O4
PCl2 C 53.03; H 4.86; N 8.50%).
1-Alkyl-2-[bis(dichloro phosphino)methylene] Guinoline
[5] and 1-Alkyl–6-[bis-(dichlorophosphino) Methylene]
Quinoline (14)
General Procedure
The above procedure was followed using pertinent alkyl quinolinium
halide (0.01 M), triethylamine (3.03 gm, 0.03 M), and phosphorus tri
chloride (2.74 gm, 0.02 M). The reaction mixture was directly filtered
and on removing the solvent from the filtrate under vacuum an amor-
phous brown solid was obtained.
5a (R H) (% Found: C 56.40; H 4.08; N 11.01 Calculated for C17 H15
N3P2Cl; C 56.8; H 4.17; N 11.6%).
14 (R H) (% Found: C 82.8; H 6.37; N 10.7 Calculated for C27 H25
N3O2P2Cl4; C 82.9; H 6.40; N 10.76%).
1-Alkyl-2-(dichlorophosphino-phenyl Methylene)-
1,2-dihydro Quinoline (11)
General Procedure
The above procedure was followed using 1-alkyl-2-benzyl quinolin-
ium halide (0.01 M), triethylamine (2.02 g, 0.02 M), and phosphorus tri

594
P. Sharma et al.
chloride (1.37 gm, 0.01 M). The sample (11a) obtained from removing
the solvent from benzene filtrate contained traces of the ammonium
salt.
11a (R H) (% Found: C 80.9; H 6.13; N 12.8 Calculated for C22 H20
N3PCl2; C 80.94; H 6.20; N 12.9%).
CONCLUSION
The reaction of differently substituted N-quinolinium salts with phos-
phorus trichloride has been investigated. It has been observed that
cyclization to 2-phosphaquinolines takes place exclusively when N-
methylene group is sufficiently activated. Furthermore, if N-methylene
group is not sufficiently activated, reaction occurs at the 2-methylene
group yielding dichloro phosphinylated an hydrobases 5 and 11.
REFERENCES
[1] A. Schmidpeter and K. Karaghiosbff, Multiple Bonds and Low Co-ordination in
Phosphorus Chemistry, edited by M. Regilz and U. J. Scherer (Thieme, Stuttgart
1990), p. 258.
[2] A. Litvinov, K. Karaghiosoff, A. Schmidpeter, E. Ya. Zabolina, and E. N. Dianova,
Heteroatom. Chem., 2, 369 (1991).
[3] R. K. Bansal, K. Karaghiosoff, and A. Schmidpeter, Tetrahedron, 50, 7675 (1994).
[4] R. K. Bansal and J. Heinicke, Chem. Rev., 101, 3549 (2001).
[5] J. Heinicke, N. Gupta, A. Surana, N. Penleeke, B. Witt, K. Stein Hauser, R. K. Bansal,
and P. G. Jones, Tetrahedron, 57, 9963 (2001).
[6] A. Surana, S. Singh, R. K. Bansal, N. Penleeke, A. Spannenberg, and J. Heinicke,
J. Organ. Chem., 646, 113 (2002).
[7] R. K. Bansal, L. Hemrajan, and N. Gupta, Heteroatom. Chem., 10, 598 (1999).
[8] R. K. Bansal, K. Karaghiosoff, N. Gandhi, and A. Schmidpeter, Synthesis, 361,
(1995).
[9] F. W. Kro¨ck and F. Kro¨hnke, Chem. Ber., 102, 669 (1969).
[10] O. R. Rodig, Quaternary Pyridinium Compounds, series: The Chemistry of Hete-
rocyclic Compound, edited by R. A. Abramovitch (Intersciences, New York, 1974),
vol. 14, part II. p. 309.
[11] A. Schmidpeter and K. Karghlosoff, Handbook of Phosphorus—31 Nuclear Magnetic
Resonance Data, edited by J. C. Tebby (CRC Press, Boca Raton, FL 1991), p. 29.
[12] W. G. Phillips and K. W. Ralts, J. Org. Chem., 35, 3144 (1970).