Unusual substituent migration in 4-allyloxy-3-(2-benzylbenzoyl)- 2-methylquinolines

Full text of DOI:10.1007/s10593-009-0375-7

Chemistry of Heterocyclic Compounds, Vol. 45, No. 8, 2009
UNUSUAL SUBSTITUENT MIGRATION
IN 4-ALLYLOXY-3-(2-BENZYLBENZOYL)-
2-METHYLQUINOLINES
N. A. Larina1,2, V. Lokshin1, O. A. Fedorova2, and V. Khodorkovsky1*
Keywords: photochromes, quinolines, Claisen rearrangement, Cope rearrangement.
Photoreversible photochromic systems have received considerable attention in light of their potential as
components in optoelectronic devices [1]. In previous work [2], we showed that colorless 3-(2-benzylbenzoyl)-
1,2-dimethyl-4(1H)quinolone (1) undergoes a reversible photoinduced cyclization to give a red fluorescent
product. We have subsequently studied such quinolones with substituents at C-2, which are capable of
undergoing polymerization.
Ph
Ph
Ph
O
O
O
N
O
O
N
O
N
Me
Me
Me
Me
2
1
3
Ph
Ph
O
O
O
O
N
N
H
Me
5
4
_______
* To whom correspondence should be addressed, e-mail: khodor@cinam.univ-mrs.fr.
1CINaM-CNRS UPR 3118 Interdisciplinary Nanoscience Center of Marseille, Campus de Luminy, Case 913,
13288 Marseille Cedex 9, France.
2D. I. Mendeleev Russian Chemical Engineering University, Moscow 125047, Russia; e-mail: fedorova@ineos.ac.ru.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1266-1269, August, 2009.
Original article submitted July 17, 2009.
0009-3122/09/4508-1011©2009 Springer Science+Business Media, Inc.
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Ketone 2, which was obtained in 60% yield from the corresponding N-unsubstituted quinolone and allyl
bromide in DMF/K2CO3, appeared to be a promising precursor for such purposes. We might have expected that
ketone 2 would undergo a series of Claisen and Cope rearrangements already described for 3-methyl- [3] and
3-ethoxycarbonyl-substituted [4] 4-allyloxyquinolones to give the desired 2-(4-butenyl)quinolone 5. However,
heating ketone 2 in o-dichlorobenzene at reflux unexpectedly gave (3-allyl-2-methyl-4-quinolinyl)-2-benzyl
benzoate 4 in 48% yield as the major product. It would be logical to assume that benzoate 4 would be formed
from Claisen rearrangement intermediate 3. Indeed, a similar benzoyl group migration was recently postulated to
explain the composition of the reaction products upon vacuum flash thermolysis at 650°C [5]. In our case, the
1,3-shift of the 2-benzylbenzoyl group from carbon to oxygen occurs at relatively low temperature and competes
efficiently with the Cope rearrangement step. The direction of the reaction can probably be attributed to steric
hindrance by the bulky 2-benzylbenzoyl group. Indeed, substituent exchange at C-2 and C-3 is not observed for
the 3-benzoyl analog and the expected 3-benzoyl-2-butenylquinolone was obtained under the same conditions as
the only product.
In light of the special importance of 4-quinolones as biologically active compounds [6], the systematic
study of this unexpected sequence of rearrangements may open new synthetic approaches to previously
unknown 3-substituted 4-quinolone derivatives that have been difficult to obtain.
The 1H and 13C NMR spectra were taken on a Bruker 250 spectrometer at 250 and 65 MHz, respectively,
in DMSO-d6 (compound 4) and CDCl3 (for compound 5) with TMS as the internal standard.
Preparation of (2-Methyl-3-prop-2-en-1-ylquinolin-4-yl)-2-benzylbenzoate (4) and 3-[(2-Benzyl-
phenyl)-carbonyl]-2-but-3-en-1-ylquinolin-4(1H)-one (5). A solution of ketone 2 (690 mg) in o-dichloro-
benzene (10 ml) was heated at reflux for 1 h. Separation on a silica gel column using ethyl acetate–cyclohexane
as the eluent gave 210 mg (30%) quinolone 5 as a colorless powder, mp 186-187°C and 330 mg (48%)
benzoate 4 as colorless crystals, mp 125-126°C (heptane).
1
Benzoate 4. H NMR spectrum, δ, ppm (J, Hz) (a) benzoyl, b) benzyl, d) allyl groups): 2.76 (3H, s,
CH3); 3.34-3.46 (2H, m, 1d-CH2), 4.51 (2H, s, CH2Ph); 4.94 (1H, dtd, J = 17.1, J = 1.7, J = 1.5, H-3d trans);
5.04 (1H, dtd, J = 10.2, J = 1.6, J = 1.5, H-3d cis); 5.83 (1H, ddt, J = 17.1, J = 10.2, J = 5.8, H-2d); 7.10-7.20
(2H, m, H-3b and H-5b); 7.20-7.31 (3H, m, H-2b, H-4b, H-6b); 7.32-7.52 (4H, m, H-3a, H-5a, H-4a, H-7);
7.59-7.67 (1H, m, H-6a); 7.65 (1H, ddd, J = 8.5, J = 6.6, J = 1.8, H-6); 8.03 (1H, ddd, J = 8.5, J = 0.8, J = 0.7,
H-5); 8.3 (1H, dd, J = 7.8, J = 1.4, H-8). 13C NMR spectrum, δ, ppm: 23.7 (CH3); 31.1 (CH2); 39.9 (CH2Ph);
116.7 (=CH2); 121.3 (CH); 121.7 (C); 123.3 (C); 126.2 (CH); 126.4 (CH); 127.0 (CH); 127.6 (C); 128.5 (2CH);
128.7 (CH); 129.0 (2CH); 129.4 (CH); 131.8 (CH); 132.6 (CH); 133.6 (CH); 134.0 (CH); 140.7 (C); 144.3 (C);
147.8 (C); 152.6 (C); 160.2 (C(5)–O); 164.5 (O–C=O). Found, %: C 82.47; H 5.90; N 3.49. C27H23NO2.
Calculated, %: C 82.42; H 5.89; N 3.56.
1
Quinolone 5. H NMR spectrum, δ, ppm (J, Hz) (a) benzoyl, b) benzyl, c) butenyl groups): 2.33-2.46
(2H, m, H-2c); 2.61-2.71 (2H, m, H-1c); 4.27 (2H, s, CH2Ph); 4.94-5.05 (2H, m, =CH2); 5.79 (1H, ddt, J = 16.9,
J = 10.4, J = 6.4, H-3c); 7.12-7.29 (7H, m, H-2b-H-6b, H-3a, H-5a); 7.29-7.44 (2H, m, H-6, H-4a); 7.49 (1H,
dd, J = 7.7, J = 1.0, H-6a); 7.61 (1H, dd, J = 8.4, J = 1.0, H-8); 7.70 (1H, ddd, J = 8.4, J = 6.9, J = 1.5, H-7);
8.00 (1H, dd, J = 8.1, J = 1.5, H-5); 11.94 (1H, br. s, NH). 13C NMR δ, ppm: 30.7 (CH2); 32.9 (CH2); 38.0
(CH2Ph); 115.8 (=CH2); 118.2 (CH); 120.7 (C); 123.8 (CH); 124.9 (C); 125.0 (CH); 125.8 (CH); 126.0 (CH);
128.2 (2CH); 129.0 (2CH); 129.8 (CH); 131.0 (CH); 131.2 (CH); 132.4 (CH); 136.8 (CH); 139.44 (C); 139.46
(C); 140.3 (C); 141.2 (C); 153.2 (C); 175.3 (C(4)=O); 198.8 (C=O). Found, %: C 82.51; H 5.82; N 3.55.
C27H23NO2. Calculated, %: C 82.42; H 5.89; N 3.56
The structures of 2 and 4 were additionally confirmed by X-ray diffraction structural analysis. The
corresponding CIF files were deposited at the Cambridge Crystallographic Data Center (CCDC 740002 and
CCDC 740003).
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