Reaction of 1-Methyl-3,4-dihydroisoquinolines with alkyl 4-aryl-2,4-dioxobutanoates

Full text of DOI:10.1134/S107042800906030X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 6, pp. 953–954. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © V.V. Khalturina, Yu.V. Shklyaev, A.N. Maslivets, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 6,
pp. 965–966.
SHORT
COMMUNICATIONS
Reaction of 1-Methyl-3,4-dihydroisoquinolines
with Alkyl 4-Aryl-2,4-dioxobutanoates
V. V. Khalturinaa, Yu. V. Shklyaeva, and A. N. Maslivetsb
a Institute of Technical Chemistry, Ural Division, Russian Academy of Sciences, Perm, Russia
b Perm State University, ul. Bukireva 15, Perm, 614990 Russia
e-mail: koh2@psu.ru
Received July 4, 2008
DOI: 10.1134/S107042800906030X
We previously reported on the acylation of enamino
tautomers of substituted 1-methyl-3,4-dihydroisoquin-
olines at the exocyclic methylene group with 5-aryl-
2,3-dihydrofuran-2,3-diones and obtained the corre-
sponding (2Z,5Z)-1-aryl-3-hydroxy-5-[3,3-dimethyl-
3,4-dihydroisoquinolin-1(2H)-ylidene]pent-2-ene-1,4-
diones [1, 2]. In the present communication we de-
scribe the reaction of aroylpyruvic acid alkyl esters I
with substituted 1-methyl-3,4-dihydroisoquinolines II.
Our interest in this reaction originates from the fact
that esters I (alcoholysis products of 5-aryl-2,3-di-
hydrofuran-2,3-diones [3]) usually differ in chemical
behavior from parent furandiones [4]. It should also be
noted that esters I may be prepared by the Claisen
condensation of acetophenones with dialkyl oxalates
[5] and that they are more accessible compounds than
5-aryl-2,3-dihydrofuran-2,3-diones.
By heating alkyl (Z)-4-aryl-2-hydroxy-4-oxobut-2-
enoates (alkyl aroylpyruvates) Ia and Ib with isoquin-
olines IIa and IIb (molar ratio 1:1) in boiling anhy-
drous chloroform for 5–7 h we obtained the corre-
sponding (2Z,5Z)-1-aryl-3-hydroxy-5-[3,3-dimethyl-
3,4-dihydroisoquinolin-1(2H)-ylidene]pent-2-ene-1,4-
diones IIIa and IIIb which were identified by com-
paring with authentic samples whose structure was
confirmed by X-ray analysis.
The spectral parameters of compounds IIIa and
IIIb in DMSO-d6 solution indicated that they exist as
mixtures of enol and ketone tautomers A and B at
a ratio of ~9:1.
Presumably, the described transformation involves
acylation of the exocyclic methylene group in enamino
tautomer C of isoquinolines II with the ester group of
H
·
·
·
Me
Me
Me
O
O
R
R
R
R
Me
OAlk
+
Ar
N
NH
O
Me
IIa, IIb
CH2
Ia, Ib
C
R
R
H
O
R
R
·
·
·
O
H
O
O
H
Ar
Ar
O
N
O
N
·
·
·
·
·
·
H
H
Me
Me
Me
Me
A
IIIa, IIIb
B
I, Alk = Me, Ar = Ph (a); Alk = Et, Ar = C6H4NO2-p (b); II, R = H (a), OMe (b); III, R = H, Ar = Ph (a);
R = OMe, Ar = C6H4NO2-p (b).
953

KHALTURINA et al.
954
compounds I. This process is not typical of esters I;
they usually react with nucleophiles via replacement at
the most electrophilic α-carbon atom [4, 6].
(2H, 4′-H), 3.85 s (3H, OMe), 3.86 s (3H, OMe),
4.55 s (2H, 2-H), 6.22 s (1H, 5-H), 6.96 s (1H, Harom),
7.26 s (1H, Harom), 7.06–8.23 m (4H, C6H4), 11.56 s
(1H, NH). Found, %: C 63.59; H 5.41; N 6.03.
C24H24N2O7. Calculated, %: C 63.71; H 5.35; N 6.19.
(2Z,5Z)-5-[3,3-Dimethyl-3,4-dihydroisoquinolin-
1(2H)-ylidene]-3-hydroxy-1-phenylpent-2-ene-1,4-
dione (IIIa). A solution of 5.0 mmol of ester Ia and
5.0 mmol of isoquinoline IIa in 20 ml of anhydrous
chloroform was heated for 5 h under reflux (the prog-
ress of the reaction was monitored by TLC). The mix-
ture was cooled, and the precipitate was filtered off.
Yield 1.06 g (89%), mp 146–148°C (decomp.; from
ethyl acetate–ethanol, 2:1). IR spectrum, ν, cm–1:
3150 br (NH, OH, assoc.), 1593 br (C=O, assoc.).
1H NMR spectrum, δ, ppm: A: 1.32 s (6H, Me), 2.99 s
(2H, 4′-H), 6.51 s (1H, 5-H), 7.16 s (1H, 2-H), 7.36–
8.07 m (9H, Harom), 12.06 s (1H, NH), 15.95 br.s (1H,
OH); B: 1.28 s (6H, Me), 2.95 s (2H, 4′-H), 4.51 s
(2H, 2-H), 6.30 s (1H, 5-H), 7.34–8.07 m (9H, Harom),
11.57 s (1H, NH). 13C NMR spectrum, δC, ppm: 27.38
(Me), 50.05 (C4′), 85.09 (C3′), 93.58 (C5), 112.05
(C2), 119.78–135.86 (Carom), 159.37 (C3), 180.00 (C1′),
180.82 (C4), 188.17 (C1). Found, %: C 75.99; H 6.11;
N 3.88. C22H21NO3. Calculated, %: C 76.06; H 6.09;
N 4.03.
The IR spectra were recorded on an FMS-1201
spectrometer from samples dispersed in mineral oil.
1
The H NMR spectra were obtained on a Bruker WP-
400 spectrometer using DMSO-d6 as solvent and TMS
as internal reference. The purity of the products was
checked by TLC on Silufol plates; eluent ethyl
acetate–benzene, 1:5; development with iodine vapor.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
nos. 08-03-01032, 07-03-96036, 07-03-00001).
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droisoquinolin-1(2H)-ylidene]-3-hydroxy-1-(4-ni-
trophenyl)pent-2-ene-1,4-dione (IIIb) was synthe-
sized in a similar way. Yield 86%, mp 148–150°C
(decomp.; from ethanol). IR spectrum, ν, cm–1: 3190 br
1
(NH, OH, assoc.), 1603 br (C=O, assoc.). H NMR
spectrum, δ, ppm: A: 1.32 s (6H, Me), 2.91 s (2H,
4′-H), 3.86 s (3H, OMe), 3.87 s (3H, OMe), 6.44 s
(1H, 5-H), 6.98 s (1H, Harom), 7.22 s (1H, 2-H), 7.31 s
(1H, Harom), 7.08– 8.38 m (4H, C6H4), 12.07 s (1H,
NH), 16.20 br.s (1H, OH); B: 1.27 s (6H, Me), 2.87 s
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