P-Terphenyl as unexpected by-product in the synthesis of 2,5-diphenylpyrrole from acetophenone oxime and phenylacetylene

Full text of DOI:10.1134/S1070428010030279

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 3, pp. 452–454. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © O.V. Petrova, A.I. Mikhaleva, L.N. Sobenina, B.A. Trofimov, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46,
No. 3, pp. 456–458.
SHORT
COMMUNICATIONS
p-Terphenyl as Unexpected By-Product
in the Synthesis of 2,5-Diphenylpyrrole from Acetophenone
Oxime and Phenylacetylene
O. V. Petrova, A. I. Mikhaleva, L. N. Sobenina, and B. A. Trofimov
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: boris_trofimov@irioch.irk.ru
Received June 1, 2009
DOI: 10.1134/S1070428010030279
The synthesis of 2,5-diphenyl-1H-pyrrole (I) from
acetophenone oxime and phenylacetylene in super-
basic systems MOH–DMSO (where M is an alkali
metal) [1–4] is attractive due to its simplicity (one-step
process) and accessibility of initial compounds, despite
poor yield of the target product (14–18%); further-
more, alternative methods [5–7] include many steps,
and the overall yields of pyrrole (I), calculated for all
steps, are comparable with the that obtained in the
reaction of acetophenone oxime and phenylacetylene
(Scheme 1).
pected product, p-terphenyl (II) with a yield of 1.5%
(Scheme 1). Special experiments showed that p-ter-
phenyl (II) is not formed from acetophenone oxime or
phenylacetylene taken separately under analogous con-
ditions. On the other hand, we obtained 1.7% of p-ter-
phenyl in the reaction of acetophenone with NaOH in
DMSO (140°C, 4 h; Scheme 2).
Scheme 2.
MOH–DMSO
140°C, 4 h
Ph
O
Ph
Me
Ph
Scheme 1.
II
NaOH–DMSO
NOH
140°C, 4 h
M = Na (yield 1.7%), K (14.6%).
+
Ph
CH
Ph
Ph
N
H
Ph
Me
Presumably, acetophenone in the system NaOH–
DMSO undergoes hydroxymethylation [8–14] to pro-
duce substituted allyl alcohol III, and prototropic iso-
merization of III gives aldehyde IV. Dimerization of
aldehyde IV (like aldolization–crotonization) leads to
p-terphenyl (II) (Scheme 3). The adduct of DMSO
with acetophenone, compound VI, was isolated previ-
ously and characterized as hydroxy derivative (after
neutralization of the reaction mixture) [15]. The pro-
posed mechanism is also consistent with the fact that
no p-terphenyl (II) was detected among products
formed in the synthesis of pyrrole I according to
Scheme 1 in less basic LiOH–DMSO system; presum-
ably, this system cannot ensure generation of dimsyl
anions in a sufficient concentration. However, the
other steps in Scheme 3, especially dimerization of
aldehyde IV, require additional proofs, including isola-
I, 14%
Ph
O
+
+
Ph
Me
Ph
40%
II, 1.5%
The main factor responsible for the low yield of
pyrrole I is formation of an appreciable amount of
acetophenone (up to 40%); however, the latter can be
subjected to oximation and brought again into the syn-
thesis of pyrrole I. Therefore, the real yield of I, cal-
culated on acetophenone as primary initial compound,
is considerably higher. Further optimization of this
reaction implies study on other side processes. While
performing studies in this line we isolated from the
reaction mixture (NaOH–DMSO, 140°C, 4 h) an unex-
452

p-TERPHENYL AS UNEXPECTED BY-PRODUCT
453
Scheme 3.
O
S
O
S
+
MeOH
+
H2O
[2,3]
Me
Me
Me
CH2 M+
V
O
Me
O
S
CH2
O
S
CH2
V
O
–MOH
HO–
Ph
Me
Ph
Me
Ph
Me
Ph
SMe
MO
VI
CH2
Me
Me
H2O
O
OH
OH
–[HSOMe]
Ph
Ph
Ph
III
IV
Me
O
+
Ph
II
Ph
–2H2O
O
Me
IV
IV
tion of substituted allyl alcohol III; the reaction mech-
anism will be the subject of our further studies.
3034, 1945, 1879, 1595, 1576, 1480, 1415, 1403,
1075, 1002, 838, 747, 688. 1H NMR spectrum, δ, ppm:
7.66 s (4H, C6H4), 7.63 m (4H, o-H), 7.44 m (4H,
m-H), 7.34 m (2H, p-H). 13C NMR spectrum, δC, ppm:
140.8 (Ci), 140.2 (C1, C4), 128.9 (Cm), 127.6 (C2, C3,
C5, C6), 127.4 (Cp), 127.2 (Co). Mass spectrum, m/z
(Irel, %): 231 [M + H]+ (18), 230 [M]+ (100), 215 (4),
202 (6), 152 (6), 115 (25), 101 (12), 88 (5), 76 (5), 51
(4). Found, %: C 93.66; H 6.24. C18H14. Calculated, %:
C 93.87; H 6.13. M 230.11.
The use of a more active system, KOH–DMSO
(140°C, 4 h) allowed us to raise the yield of p-ter-
phenyl (II) to 14.6% (Scheme 2).
To conclude, we have revealed a new reaction, one-
step conversion of acetophenone into p-terphenyl in
superbasic systems MOH–DMSO. This reaction essen-
tially supplements fundamental chemistry of fatty aro-
matic ketones, and its further optimization could make
it valuable as a simple and selective synthesis of
p-terphenyls.
The filtrate was distilled under reduced pressure to
isolate 7.31 g (40%) of acetophenone, 2.97 g of un-
reacted acetophenone oxime (conversion 86%), and
4.73 g (14%) of 2,5-diphenyl-1H-pyrrole.
p-Terphenyl (II). a. A mixture of 20.4 g (0.15 mol)
of acetophenone oxime and 6.0 g (0.15 mol) of sodium
hydroxide in 200 ml of dimethyl sulfoxide was stirred
at 100–105°C until the corresponding oxime sodium
salt was obtained (2 h). The mixture was heated to
140°C, and a solution of 16.85 g (0.165 mol) of phen-
ylacetylene in 25 ml DMSO was added dropwise under
stirring over a period of 3.5 h. The mixture was stirred
for 0.5 h more, cooled to room temperature, diluted
with 600 ml of water, and extracted with diethyl ether
(7×100 ml). The extracts were combined, washed with
water (4×100 ml), and dried over potassium carbonate.
The solvent was distilled off, and the residue, a brown
viscous liquid containing some crystals, was filtered
through a glass filter. The crystals were washed with
cold diethyl ether and dried to obtain 0.52 g (1.5%) of
light brown lustrous crystals with mp 210–212°C
(from hexane); published data: mp 212–213°C (Aldrich
1996–1997, p. 1367). IR spectrum, ν, cm–1: 3060,
b. A mixture of 1.5 g (37.5 mmol) of NaOH and
50 ml of DMSO was heated to 140°C under stirring,
4.50 g (37.5 mmol) of acetophenone was added drop-
wise under stirring over a period of 10 min, and the
mixture was stirred for 4 h at that temperature. The
mixture was cooled to room temperature, 30 ml of
DMSO was distilled off, and the residue was diluted
with 75 ml of water and extracted with diethyl ether
(6×25 ml). The extracts were combined, washed with
water (3×30 ml), and dried over potassium carbonate.
The solvent was removed to obtain 3.80 g of a dark
brown viscous liquid containing some fine crystals.
The crystals were filtered off through a glass filter and
washed with cold diethyl ether to obtain 0.145 g
(1.7%) of p-terphenyl.
c. Following an analogous procedure (method b),
from 4.50 g (37.5 mmol) of acetophenone and 2.44 g
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PETROVA et al.
454
4. Petrova, O.V., Sobenina, L.N., Ushakov, I.A., Mikha-
leva, A.I., and Trofimov, B.A., Arkivoc, 2009, part (iv),
p. 14.
(37.5 mmol) of KOH in 50 ml of DMSO (140°C, 4 h)
we obtained 0.545 g (6.3%) of p-terphenyl. According
to the GC–MS data, the residue (2.40 g) after isolation
of p-terphenyl contained an additional amount of com-
pound II, 0.72 g (30%); overall yield 14.6%.
5. Tedder, J.M. and Webster, B., J. Chem. Soc., 1960,
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1
Khim. Geterotsikl. Soedin., 1984, p. 1077.
1
a Bruker DPX-400 spectrometer (400 MHz for H and
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100.6 MHz for 13C) using CDCl3 as solvent and hexa-
methyldisiloxane as internal reference. The IR spec-
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obtained on a Shimadzu GCMS-QP5050A system
(quadrupole mass analyzer, a.m.u. range 34–650;
SPB–5ms capillary column, 60 m×0.25 mm×0.25 μm;
carrier gas helium, flow rate 0.7 ml/min; injector and
ion source temperature 240°C, gas inlet pressure
300 kPa; oven temperature programming from 60 to
250°C at a rate of 10 deg/min).
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