Reactions of tautomeric quaternary phosphonium salts based on triphenylphosphine and 3-phenylpropargyl bromide with nitrogen nucleophiles

Article abstract of DOI:10.1023/A:1015034402464

Triphenyl(3-phenylprop-1-ynyl)phosphonium bromide (3) was isolated. This compound is a third isomer for the tautomeric system triphenyl(3-phenylpropadienyl)phosphonium bromide (1) ->/<- triphenyl(3-phenylprop-2-ynyl)phosphonium bromide (2). Salts 1 and 2 smoothly react with secondary amines to give adducts with an α,β-double bond, while salt 3 changes to an allene ylide. Addition of phenylhydrazine and triphenyl(phenylethynyl)phos-phonium bromide to salts 1 and 2 and addition of dimethylformamide to salt 2 were performed.

Full text of DOI:10.1023/A:1015034402464

148
Russian Chemical Bulletin, International Edition, Vol. 51, No. 1, pp. 148—150, January, 2002
Reactions of tautomeric quaternary phosphonium salts
based on triphenylphosphine and 3ꢀphenylpropargyl bromide
with nitrogen nucleophiles
†

R. A. Khachatrian, S. A. Zalinian, G. B. Bagdasarian, E. A. Sarkisova, and M. G. Indzhikian
Institute of Organic Chemistry, National Academy of Sciences of the Republic of Armenia,
167a ul. Zakhariya Kanakertsi, 375091 Yerevan, Republic of Armenia.
Fax: +7 (374 1) 28 3511. Eꢀmail: MVM@lЅ2.yerphi.am
Triphenyl(3ꢀphenylpropꢀ1ꢀynyl)phosphonium bromide (3) was isolated. This compound
is a third isomer for the tautomeric system triphenyl(3ꢀphenylpropadienyl)phosphonium broꢀ
mide (1)
triphenyl(3ꢀphenylpropꢀ2ꢀynyl)phosphonium bromide (2). Salts 1 and 2
smoothly react with secondary amines to give adducts with an α,βꢀdouble bond, while salt 3
changes to an allene ylide. Addition of phenylhydrazine and triphenyl(phenylethynyl)phosꢀ
phonium bromide to salts 1 and 2 and addition of dimethylformamide to salt 2 were performed.
Key words: triphenyl(3ꢀphenylpropꢀ2ꢀynyl)phosphonium bromide, triphenyl(3ꢀphenylꢀ
propadienyl)phosphonium bromide, triphenyl(3ꢀphenylpropꢀ1ꢀynyl)phosphonium bromide,
isomerization, amines, ylide, phenylhydrazine.
Earlier,1,2 we have found that 3ꢀphenylpropꢀ2ꢀynyl
diethylamine) to give similar adducts 4a—c involving the
α,βꢀunsaturated bond, the reaction of αꢀacetylene salt 3
with piperidine affords alleneꢀtype ylide 5. Salt 3 is recovꢀ
ered when ylide 5 is treated with aqueous HBr. The reacꢀ
tions of salt 2 with amines seem to include prototropic
isomerization into salt 1 (Scheme 1).
bromide reacts with triphenylphosphine to give, dependꢀ
ing on the solvent, either individual salts containing an
αꢀallene (1) or a βꢀacetylene group (2) or their mixture. It
was also shown that the βꢀacetylene salt 2 completely
changes to allene 1 on storage in acetonitrile, ether, ethaꢀ
nol, and dimethylformamide. The reverse reaction occurs
in aqueous HBr, in trichloroacetic acid at a melting point,
and, surprisingly, in CHCl3.
Scheme 1
The goal of the present work was to perform a detailed
study of mutual transformations in a system containing
salts with αꢀallene and βꢀacetylene groups.
Results and Discussion
It was shown that the heating of salt 1 in DMF at
∼100 °C yields triphenyl(3ꢀphenylpropꢀ1ꢀynyl)phosꢀ
phonium bromide (3) with an αꢀtriple bond, which is a
third isomer for the tautomeric system triphenyl(3ꢀpheꢀ
nylpropadienyl)phosphonium bromide (1)
tripheꢀ
nyl(3ꢀphenylpropꢀ2ꢀynyl)phosphonium bromide (2).
The structure of salt 3 was determined from 1H NMR
and Raman spectroscopy data.
While αꢀallene and βꢀacetylene salts 1 and 2 smoothly
react with secondary amines (piperidine, morpholine, and
It should be noted that the intermediate formation of
isomeric allenylphosphonium salts was suggested earlier
for the reactions of propꢀ2ꢀynylphosphonium salts with
† Deceased.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 139—141, January, 2002.
1066ꢀ5285/02/5101ꢀ148 $27.00 © 2002 Plenum Publishing Corporation

Action of nucleophiles on phosphonium salts
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
149
nucleophiles3—11 and unambiguously proved by studying
the reaction of triphenylpropꢀ2ꢀynylphosphonium broꢀ
mide with methanol.4 We found that salt 3 reacts with
aqueous HBr to give a hydration product, namely,
triphenylphosphonium salt 6 with a phenylacetonyl group.
the reaction of salt 2 with DMF was carried out; apparꢀ
ently, 2 → 1 isomerization takes place to give adduct 10 at
the α,βꢀdouble bond (Scheme 3).
However, it is surprising that the reaction of prelimiꢀ
narily prepared salt 1 with DMF under the same condiꢀ
tions affords, as noted above, exclusively salt 3.
Experimental
1
H NMR spectra were recorded on a Mercuryꢀ300 Varian
The reactions of salts 1 and 2 with phenylhydrꢀ
azine yielded triphenyl(3ꢀphenylꢀ2ꢀphenylhydrazonoproꢀ
pyl)phosphonium bromide (7) (Scheme 2).
instrument (300 MHz) with Me4Si as the internal standard.
IR spectra were recorded on a Specord Mꢀ80 instrument. Raman
spectra were recorded on a DFSꢀ24 instrument (λexc = 441 nm).
Salts 1, 2, and 8 were prepared according to the known proceꢀ
dures.1—3 Their purity was checked by TLC and 1H and 31P NMR
spectroscopy.
Scheme 2
Triphenyl(3ꢀphenylpropꢀ1ꢀynyl)phosphonium bromide (3).
Triphenyl(3ꢀphenylpropadienyl)phosphonium bromide (1)
(10 g, 0.022 mol) was heated in 70 mL of DMF in a water bath
for 12 h. The solvent was removed in vacuo, and the precipitate
that formed was washed with boiling anhydrous acetone and, on
cooling, with anhydrous ether, and dried in vacuo. The yield of
salt 3 was 6.8 g (68%), m.p. 234—235 °C. Found (%): C, 70.55;
H, 4.45; Br, 17.36. C27H22BrP. Calculated (%): C, 70.89;
H, 4.81; Br, 17.50. IR (CH2Cl2), ν/cm–1: 2250 (C≡C). 1H NMR
(CD3OD), δ: 4.0 (s, 2 H, CH2Ph); 7.2—7.7 (m, 20 H, 4 Ph).
Raman spectrum, ν/cm–1: 2250 (P+C≡C).
Reaction of triphenyl(3ꢀphenylpropꢀ1ꢀynyl)phosphonium broꢀ
mide (3) with piperidine. A mixture of salt 3 (1 g, 0.0022 mol) and
piperidine (0.2 g, 0.0023 mol) in 8 mL of benzene was refluxed
for 7 h. The solvent was decanted, and the residue was washed
with anhydrous ether and dried in vacuo. The yield of piperidine
hydrobromide was 0.34 g (93.9%), m.p. 222—223 °C. A mixture
of this product with an authentic sample did not depress the
melting point. Found (%): C, 35.80; H, 7.55; Br, 48.40.
C5H12BrN. Calculated (%): C, 36.14; H, 7.22; Br, 48.19. The
solvent was removed from the benzene layer to give triphenylꢀ
phosphonium (3ꢀphenylpropadienꢀ1ꢀyl) ylide (5), yield 0.74 g
(90%). Found (%): C, 86.44; H, 5.50. C27H21P. Calculated (%):
C, 86.17; H, 5.58. IR (CH2Cl2), ν/cm–1: 1590 (benzene ring);
Analogously, triphenyl(2ꢀphenylꢀ2ꢀphenylhydrazonoꢀ
ethyl)phosphonium bromide (9) was obtained from triꢀ
phenyl(phenylethynyl)phosphonium bromide (8) and
phenylhydrazine.
Previously, we found that the allene group neighborꢀ
ing to the positive phosphonium center in salt 1 makes the
multiple bonds strongly deficient in electrons so that
weak nucleophiles such as acetone, acetophenone,12 and
phenylacetylene13 can add to the salt. In the present work,
1
1940 (allene). H NMR (CD3OD), δ: 7.0—7.6 (m, 20 H, Ph,
1 H, =CHPh).
A 40% aqueous solution of HBr (0.0011 mol) was added to a
solution of ylide 5 (0.4 g, 0.0011 mol) in 1 mL of CH2Cl2. After
∼15 h, the precipitate that formed was separated by decantꢀ
ing, washed with ether, and dried in vacuo. The yield of triꢀ
phenyl(3ꢀphenylpropꢀ1ꢀynyl)phosphonium bromide (3) was
0.24 g (50%), m.p. 234—235 °C. A mixture of this product with
an authentic sample did not depress the melting point. 1H NMR
(DMSOꢀd6), δ: 4.0 (s, 2 H, CH2P); 7.0—7.8 (m, 20 H, 4 Ph).
Reaction of triphenyl(3ꢀphenylpropadienyl)phosphonium broꢀ
mide (1) with phenylhydrazine. A mixture of phosphonium salt 1
(1.3 g, 0.003 mol) and phenylhydrazine (0.3 g, 0.003 mol) was
refluxed in 10 mL of MeCN. The solvent was removed, and the
residue was washed with anhydrous ether and dried in vacuo.
The yield of salt 7 was 1.5 g (96.2%), m.p. 200—202 °C.
Found (%): C, 70.25; H, 5.15; Br, 14.49. C33H30BrN2P. Calcuꢀ
lated (%): C, 70.0; H, 5.30; Br, 14.15. IR, ν/cm–1: 1580 (benꢀ
zene ring); 1680 (β,γꢀC=C). 1H NMR (CDCl3), δ: 4.2 (s,
Scheme 3

150
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
Khachatrian et al.
1
Table 1. Yields, elemental analysis data, and H NMR data for
adducts of secondary amines with salts 1 and 2
nyl[3ꢀphenylꢀ2ꢀ(N,Nꢀdimethylcarbamoyl)propꢀ1ꢀenyl]phosꢀ
phonium bromide (10) was 6.1 g. The dimethylformamide soluꢀ
tion was slightly concentrated, and an additional amount (0.6 g)
of the salt was precipitated with ether. The total yield of product
10 was 6.7 g (44.5%), m.p. 246 °C. Found (%): C, 67.45; H, 5.81;
Br, 14.93; P, 5.38. C30H29BrNOP. Calculated (%): C, 67.90;
H, 5.47; Br, 15.09; P, 5.85. 1H NMR (CDCl3), δ: 3.1 and
3.2 (s, 6 H, NMe2); 3.8 (s, 2 H, CH2Ph); 4.1 (d, PCH=,
2JPH = 13.8 Hz); 6.6—7.8 (m, 20 H, Ph).
Comꢀ Yield
pound from
Found
Calculated
1H NMR
(CD3OD),
δ (J/Hz)
(%)*
1 (2) (%)
4a
93.0
(68.9)
15.00, 15.19
15.09
1.40—1.65 (m, 6 Н, СН2
piperidine); 3.40—3.60
(m, 4 Н, СН2 piperidine);
3.80 (s, 2 Н, СН2Ph); 4.50
(d, 1 Н, PСН, 2JPН = 20);
7.00—8.00 (m, 20 Н, Ph)
Reactions of triphenyl(3ꢀphenylpropadienyl)phosphonium broꢀ
mide (1) and triphenyl(3ꢀphenylpropꢀ2ꢀynyl)phosphonium bromide
(2) with secondary amines (general procedure). An equimolar
amount of a corresponding amine in MeCN was added to a
solution of a phosphonium salt in MeCN. The mixture was
refluxed in a water bath. The solvent was removed, and the
residue was repeatedly washed with anhydrous ether and dried in
vacuo. The yields, elemental analysis data, and 1H NMR spectra
of compounds 4a—c are given in Table 1.
4b
4c
90.0
(92)
15.05, 14.85
14.75
3.42 (m, 4 Н, СН2О); 3.60
(m, 4 Н, СН2N); 3.75 (s,
2 Н, СН2Ph); 4.80 (d, 1 Н,
PСН, 2JPН = 20);
6.80—7.80 (m, 20 Н, Ph)
86.1
(82.0)
14.55, 14.85
14.68
1.10 (m, 6 Н, NСН2Me);
3.40 (q, 4 Н, NСН2Me,
J = 7.3); 3.60 (s, 2 Н,
СН2Ph); 4.25 (d, 1 Н,
PСН, 2JPН = 12.7);
References
1. R. A. Khachatrian, G. A. Mkrtchian, F. S. Kinoian, and
M. G. Indzhikian, Arm. Khim. Zh., 1987, 40, 696.
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M. G. Indzhikian, Zh. Obshch. Khim., 1986, 56, 231 [J. Gen.
Chem. USSR, 1986, 56 (Engl. Transl.)].
6.80—7.60 (m, 20 Н, Ph)
* For Br.
3. H. Hoffmann and H. Foerster, Tetrahedron Lett., 1964,
17—18, 983.
4. E. E. Schweiser, S. De Voc Goff, and N. P. Murrey, J. Org.
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CH2Ph); 5.1 (d, 2 H, PCH2, 2JPH = 17 Hz); 6.7—8.0 (m, 25 H,
5 Ph); 10.1 (s, NH).
Reaction of triphenyl(3ꢀphenylpropꢀ2ꢀynyl)phosphonium broꢀ
mide (2) with phenylhydrazine. Analogously, phosphonium salt 7
was obtained from salt 2 (1.1 g, 0.0025 mol) in 15 mL of acetoꢀ
nitrile and phenylhydrazine (0.3 g, 0.0027 mol). The yield of 7
was 1.2 g (90%). The characteristics of the product were identiꢀ
cal with those described above.
Reaction of triphenyl(phenylethynyl)phosphonium bromide (8)
with phenylhydrazine. A solution of phenylhydrazine (0.3 g,
0.0027 mol) in 7 mL of MeCN was added to a solution of
phosphonium salt 8 (1 g, 0.0022 mol) in 10 mL of MeCN. The
reaction mixture was refluxed in a water bath for 4 h, concenꢀ
trated, and worked up with anhydrous ether. The yield of salt 9
was 0.7 g (71%), m.p. 212—215 °C. Found (%): C, 69.45;
H, 4.56; P, 5.35; Bг, 14.83. C32H27BrN2P. Calculated (%):
1
C, 69.80; H, 4.91; P, 5.63; Bг, 14.53. H NMR (DMSOꢀd6),
δ: 5.8 (d, 2 H, PCH2, 2JPH = 16 Hz); 7.0—8.0 (m, 25 H, Ph).
Reaction of triphenyl(3ꢀphenylpropꢀ2ꢀynyl)phosphonium broꢀ
mide (2) with DMF. Salt 2 (13 g, 0.0284 mol) was heated in
DMF (90 mL) in a boiling water bath for 12 h. The liquid was
decanted, and the precipitate was refluxed with acetone for 2 h.
Then the acetone was removed, and the product was washed
with anhydrous ether and dried in vacuo. The yield of tripheꢀ
Received April 2, 2001;
in revised form July 24, 2001