NEW FLUOROARYL-CONTAINING
,
-DIOXOESTERS
1461
at 20 C. The ether layer was separated, the water
layer was extracted with ether (2 15 ml). The
combined ether extracts were dried with magnesium
sulfate, filtered, and ether was distilled off at reduced
pressure. Yield 16.55 g.
separated tarry precipitate was recrystallized from
hexane. Yield 0.6 g (18%).
2-Methyl-5,6,7,8-tetrafluoro-3-ethoxycarbonyl-
4H-1,4-dihydrobenzopyran-4-one (Vb). (a) , -Di-
oxoester (IIIb) (6.48 g, 0.02 mol) was heated to 100
110 C for 1 h. The solid precipitate was recrystalliz-
ed from a mixture CCl4 hexane, 1: 2. We obtained
5.6 g (92%) of chromone Vb as yellow powder, mp
91 92 C [1]. Physical constants are consistent with
published in [1].
Ethyl 2-pentafluorobenzoyl-3-oxobutanoate
(IIIb). Through a solution of chelate IVb (0.3 g,
0.845 mmol) in anhydrous ethyl ether (50 ml) was
passed a flow of dry hydrogen chloride till the reac-
tion mixture turned brown. The separated precipitate
was filtered off. The ether was distilled off at
3 mm Hg on a water bath at 5 C. Yield 0.27 g.
(b) A solution of chelate IVb (0.5 g, 1.41 mmol)
in DMSO (12 ml) was heated for 3 h to 80 C and
kept for 24 h at 20 C. Then was added a mixture of
HCl concn. (12 ml) and water (12 ml). The reaction
mixture was extracted with ether, the extract was
washed with water and dried. The solution was
evaporated, the residue was recrystallized from a
mixture CCl4 hexane, 1: 2. We obtained 0.2 g (47%)
of chromone Vb, mp 91 92 C [1].
Bis[ethyl 2-(2-methoxy-3,4,5,6-tetrafluoro-
benzoyl)-3-hydroxy-2-butanoato]copper(II) (IVa).
(a) To a solution of compound IIIa (0.27 g,
0.8 mmol) in methanol (5 ml was added a solution of
copper acetate (0.3 g, 1.6 mmol) in water (10 ml).
The separated bright blue precipitate was filtered off
and dried at 100 C. Yield 0.23 g.
(b) To a solution of Mg(OEt)2 freshly prepared
from magnesium turnings (3.65 g, 0.15 mol) was
added dropwise ethyl acetoacetate (16.9 g, 0.18 mol).
The mixture was stirred for 1 h at 50 C, then was
added a solution of acyl chloride IIa (25 g, 0.1 mol)
in benzene (45 ml). The mixture was stirred for 1 h at
20 C and 15 min at 50 C. On cooling to the reaction
mixture was added a solution of copper acetate
(12.95 g) and acetic acid (5.9 g) in water (40 ml).
The organic layer was separated, the water layer was
extracted with ether (3 30 ml). The ether extracts
were combined with the organic layer and dried with
magnesium sulfate. The solution was evaporated at
20 C. The residue was reprecipitated from methanol
with water, and dried. Yield 33.5 g.
6,8-Difluoro-2-methyl-5-methoxy-7-morpholino-
3-ethoxycarbonyl-4H-1,4-dihydrobenzopyran-4-
one (VI). A mixture of chromone Va (0.3 g,
0.95 mmol) and morpholine (0.33 g, 3.79 mmol) in
DMSO (3 ml) was kept for 24 h at 20 C. To the
reaction mixture was added concn. HCl (5 ml) and
water (5 ml). The precipitated tarry substance was
separated, washed with boiling hexane (10 ml), and
dried. We obtained 0.25 g of chromone VI as yellow
powder.
3-Acetimidoyl-4-hydroxy-5-methoxy-6,7,8-tri-
fluo-2H-1,2-dihydrobenzopyran-2-one (VII). A mix-
ture of chromone Va (0.3 g, 0.95 mmol) and 25%
aqueous ammonia (6 ml) was heated at stirring for
15 min. The separated precipitate was filtered off,
washed with water (10 ml), and dried at 80 C. Yield
0.225 g.
Bis(ethyl 2-pentafluorobenzoyl-3-hydroxy-2-
butanoato)copper(II) (IVb) was obtained along
procedure b from pentaflyorobenzoyl chloride (IIb)
(18.4 g, 0.08 mol) and ethyl acetoacetate (11.7 g,
0.09 mol). Yield of the dark-green chelate IVb 8.3 g.
3-Acetyl-4-hydroxy-5-methoxy-6,7,8-trifluoro-
2H-1,2-dihydrobenzopyran-2-one (VIII). A mixture
of chromone VII (0.4 g, 1.39 mmol), H2SO4 (2 ml),
and water (2 ml) was heated to 80 C for 2 h. The
separated precipitate was filtered off, dissolved in
boiling benzene (20 ml), filtered from insoluble
impurities, and the solution was evaporated. Yield of
colorless powder 0.19 g.
2-Methyl-5-methoxy-6,7,8-trifluoro-3-ethoxy-
carbonyl-4H-1,4-dihydrobenzopyran-4-one (Va).
(a)
, -Dioxoester IIIa (16.5 g, 49 mmol) was
distilled at 225 226 C and 8 mm Hg. The com-
pound distilled crystallized on cooling (mp 50
60 C) and was recrystallized from hexane. We
obtained 6 g of chromone Va as colorless powder.
5-Hydroxy-2-methyl-6,7,8-trifluoro-4H-1,4-di-
hydrobenzopyran-4-one (IX).
A
mixture of
(b) A solution of chelate IVa (4.1 g, 11.1 mmol)
in DMSO (15 ml) was heated to 80 C for 3 h. After
cooling to the reaction mixture was added a mix-
ture of concn. HCl (15 ml) and water (30 ml). The
chromone VIII (0.3 g, ).95 mmol), concn. HCl
(0.4 ml), and glacial acetic acid (1.5 ml) was boiled
for 48 h, and then poured into water (10 ml). The
separated precipitate was filtered off, washed with
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 10 2001
Kisil'
