On the synthesis of 2-substituted (η6-indan-1,3-dione)tricarbonylchromium complexes

Article abstract of DOI:10.1135/cccc19970479

Classical methods for the synthesis of indan-1,3-dione derivatives failed when applied to their tricarbonylchromium complexes. The desired 2-substituted (n⁶-indan- 1,3-dione)tricarbonylchromium complexes were prepared starting from protected in

Full text of DOI:10.1135/cccc19970479

2-Substituted (Indandione)tricarbonylchromium Complexes
479
ON THE SYNTHESIS OF 2-SUBSTITUTED
(η6-INDAN-1,3-DIONE)TRICARBONYLCHROMIUM COMPLEXES
Peter HRNCIAR, Pavel HRNCIAR, Vladimir GAJDA, Eva SVANYGOVA
1
and Stefan TOMA
Department of Organic Chemistry, Comenius University, 842 15 Bratislava,
Slovak Republic; e-mail: 1 toma@fns.uniba.sk
Received June 28, 1996
Accepted November 8, 1996
Dedicated to the memory of the late Dr Zdenek Arnold.
Classical methods for the synthesis of indan-1,3-dione derivatives failed when applied to their tri-
carbonylchromium complexes. The desired 2-substituted (η6-indan-1,3-dione)tricarbonylchromium
complexes were prepared starting from protected indan-1,3-dione derivatives such as bis(dioxolanes)
and enol ethers. Tricarbonylchromium complexes of indan-1,3-dione having at least one hydrogen at
C-2 are unstable. Nevertheless, ethylation of 2-methyl(η6-indan-1,3-dione)tricarbonylchromium and
methylation of 2-ethyl(η6-indan-1,3-dione)tricarbonylchromium were possible and proceeded with
high stereoselectivity.
Key words: Indan-1,3-dione; Tricarbonylchromium complexes.
2-Substituted (η6-indan-1,3-dione)tricarbonylchromium derivatives have been studied1–3
for their anticoagulant properties. Some derivatives, such as 2-phenylindan-1,3-dione
(Atrambone) or 2-(diphenylacetyl)indan-1,3-dione (Diphacinone), have been used in
human medicine. Some indan-1,3-dione derivatives have also rodenticide properties4.
Anions derived from 2-substituted indan-1,3-diones are interesting ambident nucleo-
philes, and their alkylation has been thoroughly studied5–7
.
The aim of the present study has been to find methods for the synthesis of tricarbo-
nylchromium complexes of 2-substituted indan-1,3-diones and to investigate their an-
ions as ambident nucleophiles.
Five possible synthetic methods (A–E, Scheme 1) were chosen for the preparation of
2-substituted (η6-indan-1,3-dione)tricarbonylchromium complexes. The routes B and C
are most frequently used for the synthesis of 2-substituted indan-1,3-diones whereas
methods D and E are not used in the classical synthesis of these compounds.
Direct complexation of indan-1,3-dione derivatives by our method8, which consists
in refluxing the starting material with hexacarbonylchromium in decalin, failed in most
cases. The only exception was 2-ethyl-2-methylindan-1,3-dione (1) that gave a reason-
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

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Hrnciar P., Hrnciar P., Gajda, Svanygova, Toma:
O
O
O
O
O
OR
OR
OR
OR
O
O
Cr(CO)
Cr(CO)
C
R
R
3
3
O
A
H
H
B
O
O
O
O
R
R
Cr(CO)
3
D
E
OR
O
O
O
R’
R
O
Cr(CO)
3
O
Cr(CO)
3
OR’
R
O
O
O
R
O
O
O
O
R
SCHEME 1
able yield (62%) of the desired product 2 as a 1.4 : 1 mixture of stereoisomers (Scheme 2).
The isomers were separated by careful chromatography on silica gel using isohexane–
ethyl acetate (4 : 1) mixture as eluent. In the main isomer the ethyl group is trans to the
O
O
O
a
Et
Me
Et
Me
Et
+
Me
Cr(CO)
Cr(CO)
3
3
O
O
O
1
2a
2b
a) Cr(CO) , decalin, ∆
6
SCHEME 2
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

2-Substituted (Indandione)tricarbonylchromium Complexes
481
Cr(CO)3 group as concluded from the results of alkylation of monosubstituted deriva-
tives (vide infra). In other cases, the reaction mixture turned green when refluxed for a
short time in decalin, which was an unambiguous sign of complex decomposition.
2-Substituted indan-1,3-diones are frequently prepared by Claisen condensation of
dimethyl or diethyl phthalate with alkyl esters of the appropriate alkanoic acids9,10. Our
unsuccessful attempts to synthesize the tricarbonylchromium complexes are sum-
marized in Scheme 3. Complexation of dimethyl or diethyl phthalate caused no prob-
lem, leading to compounds 4a and 4b in high yields. Subsequent reaction with ethyl
acetate using t-BuOK as the catalyst failed. Only the η6-tricarbonylchromium complex
COOR
COOR
COOR
COOR
COOX
COOX
a
b
Cr(CO)
Cr(CO)
3
3
R
R
X
3
4
Me
Et
Me
Et
K
H
a
b
a
b
5
6
a) Cr(CO) , decalin, ∆; b) 1.CH COOEt, t-BuOK, THF, refl.; 2. aq. HCl
6
3
SCHEME 3
of potassium phthalate 5 was formed which was converted to the acid 6. We assume an
SN2 reaction at the carbon atom of the alkoxy group, facilitated by the electron with-
drawing effect of the tricarbonylchromium moiety. Under similar conditions, Claisen
condensation of ethyl tricarbonylchromium(η6-benzoate) produced ethyl (η6-ben-
zoyl)acetate tricarbonylchromium but we were not able to isolate the product in the
pure state because of its decomposition. Similar experiments with methyl (η6-ben-
zoate)tricarbonylchromium produced only (η6-benzoic acid)tricarbonylchromium. One
could speculate whether these results are due to instability of the desired complexes
caused by the presence of acidic hydrogen on C-2 of the indan-1,3-dione skeleton, or
due to the internal strain in this condensed system. (The C–C bonds in benzenetricarbo-
nylchromium complexes are 0.1 pm longer than in benzene.) The latter explanation is
indirectly supported by similar behaviour of dimethyl thiophene-2, 3-dicarboxylate11.
The phthalide–indandione rearrangement (route C) is the most frequently used ap-
proach to 2-arylindan-1,3-diones, but it was also used for the synthesis of 2-alkylindan-
1,3-dione derivatives12–14. As we reported earlier15, it is difficult to prepare a phthalide
complex which has a Cr(CO)3 group on the phthalide moiety. For this reason we also
examined phthalides containing Cr(CO)3 (Scheme 4).
The 3-benzylidenephthalide to indan-1,3-dione rearrangement proceeded without
problems when the tricarbonylchromium group was bonded to the phenyl ring and
2-(η6-substituted phenyltricarbonylchromium)indan-1,3-diones (8a–8c) were obtained
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

482
Hrnciar P., Hrnciar P., Gajda, Svanygova, Toma:
in high yields as deep-blue to black powders. Attempted purification by column chro-
matography on SiO2 led to decomposition. Phthalide complexes 9a and 9b reacted with
methoxide anion, but the intermediate keto ester was hydrolyzed to the free acids 10a
and 10b under the work-up conditions.
O
O
R
a
O
R
O
Cr(CO)
3
H
Cr(CO)
3
7
8
R
H
7, 8
a) MeONa, MeOH
a
b
c
4-OMe
3-F
O
O
COOH
a
COCH R
2
Cr(CO)
Cr(CO)
3
3
R
H
R
9
10
9, 10
CH
3
a
b
a) 1. MeONa, MeOH; 2. aq. HCl
3,5-F C H
6 3
2
SCHEME 4
After these unsuccessful experiments we turned our attention to derivatives with pro-
tected groups: enol ethers and bis(dioxolanes) (routes D and E). Already at the very
beginning of route D (Scheme 5) we encountered some problems. Under standard con-
ditions used for cyclohexane-1,3-dione enol ether synthesis16 (short reflux with a mix-
ture of alcohol and hydrochloric acid) we obtained a complex mixture of products.
3-Methoxy-2-inden-1-ones could be prepared by the reaction of indan-1,3-dione deriva-
tives with diazomethane17. By analogy with the published18 procedure, we treated
2-substituted indan-1,3-diones with the appropriate alcohol at reflux in the presence of
toluenesulfonic acid as catalyst, using the corresponding trialkyl orthoformate as the
water scavenger. This method gave good yields of the desired enols 12a–12c. The syn-
thesis of 2-substituted 3-methoxy-2-inden-1-ones was not a selective reaction under
these conditions either. In the preparation of 3-methoxy-2-methyl-2-inden-1-one we
isolated 3,3′-dimethoxy-2-methyl-1-indanone (13a) as by-product and 3,3′-dimethoxy-
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2-Substituted (Indandione)tricarbonylchromium Complexes
483
2-ethyl-1-indanone (13b) was even the main product of the reaction with 2-ethylindan-
1,3-dione.
Complexation of the enol ethers with Cr(CO)6 by our method8 gave reasonable yields
of complexes 14a–14d. In the case of complexation of 3-ethoxy- as well as 3-methoxy-
2-phenyl-2-inden-1-one, both the possible complexes (14d, 14e and 15d, 15e) were
isolated in comparable yields. Small amounts (up to 2%) of bis(tricarbonylchromium)
O
OR’
MeO
OMe
R
a
+
R
R
O
O
O
R
R’
R
R
11
12
13
Me
Et
Me Me
Me
Et
a
b
c
a
b
c
d
e
a
b
Et
Et
Me
Et
Ph
Ph Me
Ph Et
a) R’OH, TsOH, HC(OMe) , refl.
3
OR’
OR’
O
OR’
O
a
+
+
R
12
O
Cr(CO)
Cr(CO)
Cr(CO)
Cr(CO)
3
3
3
3
R
R’
R’
R’
14
15
16
Me Me
Me
Et
Me
Et
a
b
c
d
e
d
e
d
e
Et
Et
Me
Et
Ph Me
Ph Et
a) Cr(CO) , decalin, ∆
6
SCHEME 5
complexes 16d and 16e were also isolated. Attempted preparation of the complex from
3,3-dimethoxy-1-indanone failed. A mixture of approximately nine products was de-
tected by TLC and about 50% of the starting material was destroyed by polymerization.
Compound 14a was smoothly hydrolyzed with a mixture of 6 M HCl and acetone, in
analogy to the described procedure19, and the desired 17a was obtained in 75% yield
upon flash chromatography. Alkylation with ethyl iodide gave a mixture of 2-ethyl-2-
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484
Hrnciar P., Hrnciar P., Gajda, Svanygova, Toma:
methyl(η6-indan-1,3-dione)tricarbonylchromium (2b) as the single stereoisomer (ac-
1
cording to H NMR spectrum), together with the O-alkylation product 18. The ratio of
the C- to O-alkylation products was 5 : 1. Compound 15d was hydrolyzed to give the
same product (8a) as was isolated from the phthalide–indandione rearrangement
(Scheme 6).
O
a
R
14a, 14d
Cr(CO)
O
R
3
a) aq. HCl, Me CO, refl.
2
17
Me
Ph
a
d
OEt
O
a
17a
2a + 2b +
Me
Cr(CO)
3
18
a) EtI, K CO , Me CO, r.t.
2
3
2
SCHEME 6
A synthesis of bis(dioxolane) from indan-1,3-dione has been described20, but with a
rather low yield. We therefore used a method analogous to that used for the synthesis
of enol ethers and reasonable yields (20–50%) of the desired bis(dioxolanes) 19a–19c
were thus obtained (Scheme 7). Interestingly, in the preparation of bis(dioxolane) from
2-ethylindan-1,3-dione the main product was the mono(dioxolane).
Complexation of dioxolanes 19a–19c caused no problems. Compounds 19a and 19b
gave mixtures of both possible stereoisomers in the ratio 2.1 : 1 and 8 : 1, respectively.
We assume, that in the main isomer the R group is trans to Cr(CO)3. Complexation of
19c (R = phenyl) resulted in two products, 20c and 21, in the ratio 8 : 1, the main
isomer having the Cr(CO)3 moiety on the 2-phenyl group.
The dioxolane complexes 20a and 20b were hydrolyzed with 6 M HCl–acetone mix-
ture at 50 °C. The course of the hydrolysis was monitored by TLC and the colour of the
reaction mixture changed from yellow to red. Since in the usual work-up of the reaction
mixture decomplexation started immediately after contact with aqueous potassium car-
bonate, we omitted washing with potassium carbonate solution and dilute acid. This,
together with rapid work-up, gave the desired products 17a and 17b in reasonable to
good yields. The reaction afforded only a single isomer, most probably with the R
group trans to Cr(CO)3.
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2-Substituted (Indandione)tricarbonylchromium Complexes
485
Another set of complexes which we isolated were 2-alkyl-3-hydroxyethoxy(η6-2-
inden-1-one)tricarbonylchromiums 22a and 22b. Their formation pointed also to the
fact that there is some internal strain in the desired complexes 17a and 17b.
O
O
O
O
O
O
a
b
R
R
11a-11c
Cr(CO)
O
O
3
19
20
R
19, 20
Me
Et
a
b
c
Ph
a) (CH OH) , TsOH, CH(OMe) , CHCl , refl.; b) Cr(CO) , decalin, ∆
2
2
3
3
6
OH
O
a
17a, 17b +
R
20a, 20b
Cr(CO)
O
3
R
22
Me
Et
a
b
o
a) aq. HCl, acetone, 50
C
O
O
a
8a
O
O
Cr(CO)
3
21
o
a) aq. HCl, acetone, 50
C
SCHEME 7
Alkylation of 2-methyl(η6-indan-1,3-dione)tricarbonylchromium with ethyl iodide
resulted in formation of both the C- and O-alkylation product 2a and 18 in the ratio 5 : 1.
In the alkylation of 2-ethyl(η6-indan-1,3-dione)tricarbonylchromium with methyl
iodide only the C-alkylation product was formed. These results suggest that the alkyla-
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486
Hrnciar P., Hrnciar P., Gajda, Svanygova, Toma:
tion is stereoselective, similarly to the addition of Grignard reagent to (η6-indan-2-
one)tricarbonylchromium19.
EXPERIMENTAL
Melting points were measured on a Kofler hot stage and are uncorrected. 1H NMR spectra (δ, ppm;
J, Hz) were recorded on a 80 MHz Tesla 487 A instrument with CDCl3 as solvent and tetramethylsi-
lane as internal standard.
3-[η6-(p-Methoxybenzylidene)]tricarbonylchromium phthalide (7b), (η6-3-ethylindenephthalide)tri-
carbonylchromium (9a), [3-(3,5-difluorobenzylidene)(η6-phthalide)]tricarbonylchromium (9b) as well
as 3-(η6-benzylidene)tricarbonylchromium phthalide (7a) were prepared according to ref.15. 2-Methyl-,
2-ethyl- and 2-phenylindandione (11a–11c) were prepared as described12,14. All experiments were
carried out under dry argon atmosphere.
Complexation of the ligands was performed using the described8 method and afforded complexes
2a, 2b, 4a, 4b, 13a, 14a–14e, 15d, 15e, 16a, 16d, 20a–20c, and 21.
2-Ethyl-2-methylindan-1,3-dione (1)
Sodium metal in small pieces (2.3 g, 0.1 mol) was dissolved in absolute ethanol (100 ml). 2-Methyl-
indan-1,3-dione (11.3 g, 0.07 mol) was added and the rection mixture was refluxed. Ethyl iodide
(15.6 g, 0.09 mol) was slowly added and the mixture was refluxed for another 6 h. The solution was
filtered and concentrated to a half and water (10 ml) was added. The product, 2-ethyl-2-methylindan-
1,3-dione (1), was isolated as white crystals (6.58 g, 50%), m.p. 45–47 °C. For C12H12O2 (188.2)
calculated: 76.57% C, 6.42% H; found: 76.72% C, 6.39% H. 1H NMR spectrum: 0.74 t, 3 H (CH3);
1.27 s, 3 H (CH3); 1.87 q, 2 H (CH2); 7.85–8.0 m, 4 H (C6H4).
Attempted Preparation of (η6-Indan-1,3-dione)tricarbonylchromium from 1,2-Bis(methoxycarbonyl-
η6-benzene)tricarbonylchromium (4)
Complex 4 (0.5 g, 2.5 mmol) and ethyl acetate (0.22 g, 2.5 mmol) were dissolved in dry THF (20 ml).
Potassium tert-butoxide (0.4 g, 3.6 mmol) was added and the reaction mixture was refluxed for 5 h.
Potassium (η6-benzene)tricarbonylchromium-1,2-dicarboxylate (5) (0.9 g, 95%), which deposited as a
yellow solid, was collected on filter and washed with diethyl ether. It was dissolved in water (20 ml)
and the solution was acidified with hydrochloric acid. The precipitated (η6-benzene)tricarbonylchro-
mium-1,2-dicarboxylic acid (6) was filtered and dried at 40 °C/133.3 Pa. Yellow solid, m.p. 160 °C
(0.65 g, 80%). For C11H6CrO7 (302.2) calculated: 43.73% C, 2.00% H; found: 43.87% C, 1.95% H.
1H NMR spectrum: 5.73–6.05 m, 4 H (C6H4Cr(CO)3); 8.69 s, 2 H (COOH).
2-(η6-Phenyltricarbonylchromium)indan-1,3-dione (8a)
3-(η6-Benzylidenetricarbonylchromium)phthalide (0.5 g, 1.4 mmol) was added to a solution of so-
dium methoxide prepared from Na (0.1 g) and dry methanol (20 ml). After reflux for 2 h, the reac-
tion mixture was cooled to room temperature and neutralized with 5 M HCl. The product was
extracted into diethyl ether, the ethereal solution was washed with water, dried over anhydrous
Na2SO4, filtered and concentrated till 2-(η6-phenyltricarbonylchromium)indan-1,3-dione started to
separate. Deep-red crystals (0.45 g, 90%), m.p. 180 °C. For C18H10CrO5 (358.3) calculated: 60.34% C,
2.80% H; found: 60.14% C, 2.95% H. 1H NMR spectrum: 4.01 s, 1 H (CHPh); 5.32 m, 3 H
(ArCr(CO)3); 5.62 m, 2 H (ArCr(CO)3); 8.00 m, 4 H (C6H4 – a doublet at 7.98, J = 6 can be distin-
guished).
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2-Substituted (Indandione)tricarbonylchromium Complexes
487
2-(η6-4-Methoxyphenyltricarbonylchromium)indan-1,3-dione (8b)
The title compound was prepared in a 54% yield from 3-(η6-4-methoxybenzylidenetricarbonylchro-
mium)phthalide by the same procedure as described above. Black crystals, m.p. >300 °C. For
1
C19H12CrO5 (388.3) calculated: 58.77% C, 3.11% H; found: 58.34% C, 3.58% H. H NMR spectrum:
3.70 s, 3 H (OCH3); 3.92 s, 1 H (CHAr); 5.05 d, 2 H, J = 7 (ArCr(CO)3); 5.84 d, 2 H, J = 7
(ArCr(CO)3); 7.97 m, 4 H (C6H4 – a doublet at 7.97, J = 6 can be distinguished).
2-(η6-3-Fluorophenyltricarbonylchromium)indan-1,3-dione (8c)
The title compound was prepared in a 62% yield from 3-(η6-3-flurobenzylidenetricarbonylchro-
mium)phthalide by the same procedure as described above. Deep-red crystals, m.p. >360 °C. For
C18H9CrFO5 (367.2) calculated: 58.87% C, 2.47% H; found: 59.11% C, 2.64% H. 1H NMR spectrum:
3.80 bs, 1 H (ArCr(CO)3); 4.27 bs, 3 H (ArCr(CO)3); 8.80 m, 4 H (C6H4, doublet at 7.99, J = 6 can
be distinguished).
η6-(2-Propionylbenzene)tricarbonylchromiumcarboxylic Acid (10a)
The rearrangement of η6-(2-ethylidenephthalide)tricarbonylchromium was performed by the same
procedure as described above. After acidification of the reaction mixture, the methanol was evapo-
rated and the product extracted into chloroform. Evaporation of the chloroform gave red crystals
(23%) of η6-(2-propionylbenzene)tricarbonylchromiumcarboxylic acid (10a), m.p. 170 °C. For
1
C13H10CrO6 (314.2) calculated: 49.69% C, 3.22% H; found: 49.34% C, 3.19% H. H NMR spectrum:
1.20 bt, 3 H (CH3); 2.12 bs, 1 H (COOH); 2.80 bq, 2 H (CH2); 5.37 m, 2 H (ArCr(CO)3); 5.90 m,
2 H (ArCr(CO)3).
2-(3,5-Difluorophenylacetyl)(η6-benzene)tricarbonylchromiumcarboxylic Acid (10b)
The title compound was prepared in 63% yield from 3-(3,5-difluorobenzylidene)(η6-phthalide)tricar-
bonylchromium (9b) by the same procedure as described above. Black solid, m.p. >360 °C. For
C18H8F2CrO5 (394.3) calculated: 54.84% C, 2.05 % H; found: 55.32% C, 2.15% H. 1H NMR spec-
trum: 3.70 bs, 1 H (COOH); 4.22 s, 2 H (COCH2); 5.70 m, 2 H (ArCr(CO)3); 5.97 m, 2 H
(ArCr(CO)3); 6.37 m, 1 H (C6H3F2); 6.82 m, 2 H (C6H3F2).
3-Methoxy-2-methyl-2-inden-1-one (12a)
2-Methylindan-1,3-dione (11a) (1.5 g, 0.01 mol) and trimethyl orthoformate (3.2 g, 0.03 mol) were
dissolved in methanol (20 ml). p-Toluenesulfonic acid (100 mg) was added and the reaction mixture
was refluxed for 3 h. The mixture was then poured into crushed ice, the organic material was ex-
tracted into diethyl ether, and the ethereal solution was washed with cold NaHCO3 solution and dried
over anhydrous Na2SO4. The solvent was evaporated, and the oily residue (1.8 g, 95%) was crystal-
lized from diethyl ether–isohexane (nearly pure isohexane). The yellow crystalline 12a, m.p. 79–81 °C,
was isolated in 75% yield. For C11H11O2 (174.2) calculated: 75.84% C, 5.80% H; found: 76.05% C,
5.89% H. 1H NMR spectrum: 2.01 s, 3 H (CH3); 4.24 s, 3 H (OCH3); 7.05–7.44 m, 4 H (C6H4). As
the second product we isolated 3,3-dimethoxy-2-methylindan-1-one (13a), m.p. 69–74 °C (20%). For
C12H14O3 (206.25) calculated: 69.88% C, 6.84% H; found: 69.82% C, 7.03% H. 1H NMR spectrum:
1.35 d, 3 H, J = 8 (CH3); 2.93 q, 1 H (CH); 3.33 s, 3 H (OCH3); 3.42 s, 3 H (OCH3); 7.50–7.84 m,
4 H (C6H4).
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Hrnciar P., Hrnciar P., Gajda, Svanygova, Toma:
2-Ethyl-3-methoxy-2-inden-1-one (12b)
The reaction was carried out as described above, starting from 2-ethylindan-1,3-dione (11b) (2 g,
0.01 mol) and trimethyl orthoformate (3.2 g, 0.03 mol). The yellow oily product (1.6 g; 70%) was
purified by column chromatography to give oily 2-ethyl-3-methoxy-2-inden-1-one (12b) (20%). For
C12H13O2 (188.2) calculated: 76.61% C, 6.38% H; found: 76.45% C, 6.22% H. 1H NMR spectrum:
1.11 t, 3 H (CH3); 2.45 q, 2 H (CH2); 4.22 s, 3 H (OCH3); 7.07–7.25 m, 4 H (C6H4). As the second
product we isolated 2-ethyl-3,3-dimethoxyindan-1-one (13b) (oil, 50%). For C13H16O3 (220.3) calcu-
1
lated: 70.09% C, 7.38% H; found: 70.82% C, 6.94% H. H NMR spectrum: 1.11 t, 3 H (CH3); 1.75 m,
2 H (CH2); 2.93 t, 2 H (CH); 3.32 s, 3 H (OCH3); 3.65 s, 3 H (OCH3); 7.26–7.70 m, 4 H (C6H4).
3-Ethoxy-3-ethyl-2-inden-1-one (12c)
2-Ethylindan-1,3-dione (11b; 4.5 g, 26 mmol) was dissolved in absolute ethanol (50 ml). The solu-
tion was saturated with gaseous HCl and left to stand at room temperature for 60 h. Hydrogen
chloride was then neutralized with NaOH (5 pellets) and ethanol was evaporated under reduced
pressure. The residue was dissolved in diethyl ether and the solution was washed with 30% NaOH.
The ethereal solution was dried over anhydrous Na2SO4, filtered and the solvent evaporated. The re-
maining yellow oil was flash-chromatographed on an SiO2 column in isohexane–ether (1 : 2). The
obtained yellow oil was crystallized from ether–isohexane to give the product (2 g; 46%), m.p. 46–49 °C.
For C13H14O2 (202.2) calculated: 77.20% C, 6.93% H; found: 77.32% C, 6.72% H. 1H NMR spec-
trum: 1.15 t, 3 H (CH3); 1.48 t, 3 H (CH3); 2.40 q, 2 H (CH2); 4.52 q, 2 H (OCH2); 7.25 m, 4 H
(C6H4).
3-Methoxy-2-phenyl-2-inden-1-one (12d)
The reaction of 2-phenylindan-1,3-dione (11c; 1.3 g, 6 mmol) and trimethyl orthoformate (3.2 g,
30 mmol) gave 1.5 g (90%) of yellow crystalline product, m.p. 78–81 °C (ether–isohexane). For
C
16H12O2 (236.2) calculated: 81.36% C, 5.08% H; found: 81.48% C, 5.20% H. 1H NMR spectrum:
3.87 s, 3 H (OCH3); 7.20–7.54 m, 9 H (C6H4 + C6H5).
3-Ethoxy-2-phenyl-2-inden-1-one (12e)
The reaction was carried out as described above. Starting from 2-phenylindan-1,3-dione (11c; 1.10 g,
5 mmol) and triethyl orthoformate (3.5 g, 30 mmol), yellow crystalline material (0.7 g; 56.5%) was
isolated; m.p. 69–70 °C. For C17H14O2 (250.2) calculated: 81.61% C, 5.64% H; found: 81.49% C,
5.71% H. 1H NMR spectrum: 1.28 t, 3 H (CH3); 4.13 q, 2 H (CH2); 7.52 m, 9 H (C6H4 + C6H5).
1,3-Bis(ethylenedioxy)-2-methylindan (19a)
A solution of 2-methylindan-1,3-dione (11a; 1.5 g, 10 mmol), ethylene glycol (4.8 ml), trimethyl or-
thoformate (3.2 g, 30 mmol) and p-toluenesulfonic acid (300 mg) in chloroform (20 ml) was refluxed
for 24 h. After cooling to room temperature, chloroform (100 ml) was added, the solution was ex-
tracted with 20% NaOH (5 × 50 ml), dried over Na2SO4, filtered and the solvent was evaporated.
Crystallization from diethylether–isohexane gave white crystals (1.5 g; 50%), m.p. 97–98.5 °C. For
C14H16O4 (248.2) calculated: 67.73% C, 6.49% H; found: 67.92% C, 6.32% H. 1H NMR spectrum:
1.10 d, 3 H, J = 7 (CH3); 2.72 q, 1 H (CH); 4.17 m, 8 H (OCH2); 7.35 s, 4 H (C6H4).
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489
1,3-Bis(ethylenedioxy)-2-ethylindan (19b)
The compound was prepared from 2-ethylindan-1,3-dione (11b; 1.5 g, 8 mmol), ethylene glycol (2 ml),
TsOH (250 mg) and trimethyl orthoformate (3.2 g, 30 mmol) as described for 19a. Yield 0.4 g (20%)
of white crystals, m.p. 90–92 °C (diethyl ether). For C15H18O4 (262.3) calculated: 68.68% C, 6.92% H;
1
found: 68.43% C, 6.87% H. H NMR spectrum: 1.05 t, 3 H (CH3); 1.68 q, 2 H (CH2); 2.61 t, 1 H (CH);
4.16 m, 8 H (OCH2); 7.33 bs, 4 H (C6H4).
1,3-Bis(ethylenedioxy)-2-phenylindan (19c)
The experiment was carried out as described above. Reaction of 2-phenylindan-1,3-dione (11c; 2.1 g,
0.01 mol), ethylene glycol (4.8 ml) and trimethyl orthoformate (2.4 g, 20 mmol) afforded 2.1 g
(72%) of 1,3-bis(ethylenedioxy)-2-phenylindan (19c) as white crystals, m.p. 152–154 °C. For
C19H18O4 (310.3) calculated: 73.63% C, 5.82% H; found: 73.81% C, 5.62% H. 1H NMR spectrum:
3.52 s, 1 H (CH); 3.67 m, 4 H (OCH2); 4.05 m, 4 H (OCH2); 7.32 m, 5 H (C6H5).
Complexation of Compounds 1, 3, 12, and 19
Direct complexation was carried out by heating indandione 1, alkyl phthalates 3, indenones 12 and
dioxolanes 19 with hexacarbonylchromium in decalin for 0.5–3.5 h according to ref.8.
2-Ethyl-2-methyl(η6-indan-1,3-dione)tricarbonylchromium (2a, 2b)
Complexation of indandione 1 afforded a mixture of 2a and 2b as yellow-orange crystals in 62%
yield. For C15H12CrO5 (324.2) calculated: 55.56% C, 3.72% H; found: 56.19% C, 3.74% H. Careful
chromatography afforded:
1
2a (threo), m.p. 78–79 °C. H NMR spectrum: 0.83 t, 3 H (CH3); 1.39 s, 3 H (CH3); 1.87 q, 2 H
(CH2); 5.62 d, J = 8 and 5.62 d, J = 3, 2 H (Ar(Cr(CO)3); 5.92 d, J = 8 and 5.92 d, J = 3, 2 H
(ArCr(CO)3).
1
2b (erythro), m.p. 121–123 °C. H NMR spectrum: 0.96 t, 3 H (CH3); 1.30 s, 3 H (CH3); 1.87 q,
2 H (CH2); 5.62 d, J = 8 and 5.62 d, J = 3, 2 H (ArCr(CO)3); 5.92 d, J = 8 and 5.92 d, J = 3, 2 H
(ArCr(CO)3).
Dimethyl (η6-Benzene)tricarbonylchromium-1,2-dicarboxylate (4a)
Complexation of 3a afforded 4a in 73% yield as deep-red crystals, m.p. 58.5–59.5 °C. For
1
C
13H10CrO7 (330.2) calculated: 47.28% C, 3.05% H; found: 47.10% C, 3.01% H. H NMR spectrum:
3.90 s, 6 H (OCH3); 5.35 m, 2 H (ArCr(CO)3); 5.65 m, 2 H (ArCr(CO)3. Besancon21 obtained this
compound in 55% yield.
Diethyl (η6-Benzene)tricarbonylchromium-1,2-dicarboxylate (4b)
Complexation of 3b afforded 4b (82%) as deep-red crystals, m.p. 51–52 °C. For C15H14CrO7 (358.3)
calculated: 52.28% C, 3.94% H; found: 54.49% C, 3.97% H. 1H NMR spectrum: 1.36 t, 6 H (CH3);
4.34 q, 4 H (OCH2); 5.40 bs, 2 H (ArCr(CO)3); 5.67 bs, 2 H (ArCr(CO)3).
3-Methoxy-2-methyl[η6-(2-inden-1-one)]tricarbonylchromium (14a)
Complexation of 12a afforded 14a (25%) as violet crystals, m.p. 142–146 °C. For C14H10CrO5
1
(310.2) calculated: 54.20% C, 3.24% H; found: 54.37% C, 3.26% H. H NMR spectrum: 2.03 s, 3 H
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490
Hrnciar P., Hrnciar P., Gajda, Svanygova, Toma:
(CH3); 4.21 s, 3 H (OCH3); 5.30 m, 1 H (ArCr(CO)3); 5.54 d, 2 H, J = 4 (ArCr(CO)3); 6.02 d, 1 H,
J = 6 (ArCr(CO)3).
2-Ethyl-3-methoxy[η6-(2-inden-1-one)]tricarbonylchromium (14b)
Complexation of 12b afforded 14b (22%) as violet crystals, m.p. 132–135 °C. For C15H12CrO5
1
(324.0) calculated: 55.56% C, 3.72% H; found: 55.94% C, 3.80% H. H NMR spectrum: 1.12 t, 3 H
(CH3); 2.46 q, 2 H (OCH2); 4.18 s, 3 H (OCH3); 5.25 m, 1 H (ArCr(CO)3); 5.50 m, 2 H
(ArCr(CO)3); 6.00 d, 1 H, J = 6 (ArCr(CO)3).
2-Ethyl-3-ethoxy(η6-2-inden-1-one)tricarbonylchromium (14c)
Complexation of 12c afforded 14c (18%) as violet crystals, m.p. 125–127 °C. For C16H14CrO5
1
(338.1) calculated: 56.80% C, 4.14% H; found: 56.53% C, 4.13% H. H NMR spectrum: 1.10 t, 3 H
(CH3); 1.46 t, 3 H (CH3); 2.41 q, 2 H (CH2); 4.46 q, 2 H (OCH2); 5.30 m, 1 H (ArCr(CO)3); 5.52 m,
2 H (ArCr(CO)3); 5.61 d, 1 H, J = 6 (ArCr(CO)3).
Complexation of compound 12d afforded a mixture of 14d (39%), 15d (39%), and 16d (2%).
3-Methoxy-2-phenyl[η6-(2-inden-1-one)]tricarbonylchromium (14d), brown crystals, m.p. 165 °C
(dec.). For C19H12CrO5 (372.3) calculated: 61.29% C, 2.97% H; found: 60.73% C, 3.20% H. 1H
NMR spectrum: 3.79 s, 3 H (OCH3); 5.41 t, 1 H (ArCr(CO)3); 5.62 t, 1 H (ArCr(CO)3); 5.61 d, 1 H,
J = 6 (ArCr(CO)3); 6.10 d, 1 H, J = 6 (ArCr(CO)3); 7.35 bs, 5 H (C6H5).
3-Methoxy-2-(η6-phenyltricarbonylchromium)-2-inden-1-one (15d), violet crystals, m.p. 153.4–
154.5 °C. For C19H12CrO5 (372.3) calculated: 61.29% C, 2.97% H; found: 61.08% C, 3.28% H. 1H
NMR spectrum: 4.45 s, 3 H (OCH3); 5.36 m, 3 H (ArCr(CO)3); 6.12 m, 2 H (ArCr(CO)3); 7.46 m,
4 H (C6H4).
3-Methoxy-2-(η6-phenyltricarbonylchromium)[η6-(2-inden-1-one)]tricarbonylchromium (16d), black-violet
crystals, m.p. 137–142 °C (dec.). For C22H12Cr2O8 (508.3) calculated: 51.98% C, 2.38% H; found:
1
51.54% C, 2.41% H. H NMR spectrum: 4.25 s, 3 H (COCH3); 5.37 m, 3 H (ArCr(CO)3); 5.55 m, 2 H
(ArCr(CO)3); 5.95 m, 4 H (ArCr(CO)3).
Complexation of compound 12e afforded a mixture of 14e (21%), 15e (12%), and 16e (2%).
3-Ethoxy-2-phenyl[η6-(2-inden-1-one)]tricarbonylchromium (14e), brown crystals, m.p. 115–117 °C.
1
For C20H14CrO5 (384.4) calculated: 62.17% C, 3.65% H; found: 62.90% C, 3.52% H. H NMR spec-
trum: 1.25 t, 3 H (CH3); 4.04 q, 2 H (OCH3); 5.30 dt, 1 H (ArCr(CO)3); 5.57 m, 2 H (ArCr(CO)3);
6.10 d, 1 H, J = 5 (ArCr(CO)3); 7.35 bs, 5 H (C6H5).
3-Ethoxy-2-(η6-phenyltricarbonylchromium)-2-inden-1-one (15e), violet crystals, m.p. 152–154 °C.
1
For C20H14CrO5 (384.4) calculated: 62.17% C, 3.65% H; found: 61.88% C, 3.44% H. H NMR spec-
trum: 1.62 t, 3 H (CH3); 4.79 q, 2 H (OCH3); 5.37 m, 3 H (ArCr(CO)3); 6.14 dd, 2 H, J = 7
(ArCr(CO)3); 7.40 bs, 4 H (C6H4).
3-Ethoxy-2-(η6-phenyltricarbonylchromium)[η6-(2-inden-1-one)]tricarbonylchromium (16e), black-
violet crystals, m.p. 137–140 °C. For C23H14Cr2O8 (520.4) calculated: 53.08% C, 2.51% H; found:
1
53.39% C, 2.78% H. H NMR spectrum: 1.59 t, 3 H (CH3); 4.50 q, 2 H (OCH2); 5.25–6.21 m, 9 H
(ArCr(CO)3).
1,3-Bis(ethylenedioxy)-2-methyl(η6-indan)tricarbonylchromium (20a)
Complexation of 19a afforded 20a (71%) as yellow crystals, m.p. >169 °C (dec.). For C17H15CrO5
1
(384.3) calculated: 53.15% C, 4.19% H; found: 52.75% C, 4.15% H. H NMR spectrum: 1.07 m (two
overlapped t), 3 H (CH3); 2.38 q, 0.33 H (CHR); 2.90 q, 0.66 H (CHR); 4.16 bs, 8 H (OCH2); 5.30 bs,
2 H (ArCr(CO)3); 5.43 bs, 2 H (ArCr(CO)3).
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1,3-Bis(ethylenedioxy)-2-ethyl(η6-indan)tricarbonylchromium (20b)
Complexation of 19b afforded 20b (82%) as yellow crystals, m.p. 184–186 °C. For C18H17CrO5
1
(398.3) calculated: 54.27% C, 4.55% H; found: 54.64% C, 4.61% H. H NMR spectrum: 1.02 t, 3 H
(CH3); 1.62 m, 2 H (CH2); 2.13 t, 0.05 H (CHR); 2.75 t, 0.95 H (CHR); 4.18 bs, 8 H (OCH2); 5.27 bs,
2 H (ArCr(CO)3); 5.34 bs, 2 H (ArCr(CO)3). Crystallization from isohexane gave single major
isomer (2.75 t, 1 H (CHR)).
Complexation of 19c afforded a mixture of 20c (24%) and 21 (6%).
1,3-Bis(ethylenedioxy)-2-phenyl(η6-indan)tricarbonylchromium (20c), yellow crystals, m.p. >150 °C
1
(dec.). For C22H18CrO7 (446.4) calculated: 59.19% C, 4.06% H; found: 59.01% C, 4.12% H. H NMR
spectrum: 3.50 m, 4 H (OCH2); 3.80 s, 1 H (CH); 4.07 m, 4 H (OCH2); 5.25 m, 2 H (ArCr(CO)3);
5.42 m, 2 H (ArCr(CO)3); 7.35 m, 3 H (C6H5); 7.57 m, 2 H (C6H5).
1,3-Bis(ethylenedioxy)-2-(η6-phenyltricarbonylchromium)indan (21), yellow crystals, m.p. 188 °C
1
(dec.). For C22H18CrO7 (446.4) calculated: 59.19% C, 4.06% H; found: 58.92% C, 4.23% H. H NMR
spectrum: 4.15–4.30 m, 9 (OCH2 + CHPh; app. triplet at 4.28); 5.17 t, 2 H (ArCr(CO)3); 5.43 d, 1 H,
J = 6 (ArCr(CO)3); 5.73 d, 2 H, J = 6 (ArCr(CO)3); 7.39 s, 4 H (C6H4).
Hydrolysis of Enol Ethers and Bis(dioxolanes) Derived from 2-Substituted (η6-Indan-1,3-dione)tri-
carbonylchromium. General Procedure
The appropriate starting compound (1 mmol) was dissolved in a 2 : 1 mixture of acetone–6 M HCl (5 ml)
and the reaction mixture was stirred at 40–50 °C. The course of the reaction was followed by TLC.
After the reaction was over (10 min–2 h), the mixture was poured into ice-water and the product was
extracted into diethyl ether. The ethereal solution was washed with water. The pH of the aqueous
washings should be about 4.5, as the product was soluble in water at pH ≈ 7 and would decompose.
The ethereal solution was dried over magnesium sulfate, the solvent was evaporated and the residue
was flash-chromatographed on an SiO2 column in isohexane–ethyl acetate.
2-Methyl(η6-indan-1,3-dione)tricarbonylchromium (17a).
Method A. Prepared by hydrolysis of (2-methyl-3-methoxy-η6-2-inden-1-one)tricarbonylchromium
(14a) (time of hydrolysis 10 min) in 75% yield as red crystals, m.p. 145 °C (dec.). For C13H8CrO5
1
(296.2) calculated: 52.71% C, 2.72% H; found: 52.46% C, 2.70% H. H NMR spectrum: 1.45 d, 3 H
(CH3); 2.95 q, 1 H (CH); 5.66 bs, 2 H (C6H4Cr(CO)3); 5.91 bs, 2 H (C6H4Cr(CO)3).
Method B. Prepared by hydrolysis of 1,3-bis(ethylenedioxy)-2-methyl(η6-indan)tricarbonylchro-
mium (20a) (time of hydrolysis 2.5 h) in 77% yield and was identical with the material from the
previous experiment. The second chromatographic band gave 2-methyl-3-(2-hydroxyethoxy)(η6-2-
inden-1-one)tricarbonylchromium (22a) (4%) as a red oil. For C15H12CrO6 (340.2) calculated:
1
53.11% C, 3.27% H; found: 53.28% C, 3.31% H. H NMR spectrum: 1.99 s, 3 H (CH3); 4.00 t, 2 H
(OCH2); 4.55 t, 2 H (OCH2); 5.30 m, 1 H (C6H4Cr(CO)3); 5.33 d, 2 H, J = 3 (C6H4Cr(CO)3); 6.03 d,
1 H, J = 6 (C6H4Cr(CO)3).
2-Ethyl(η6-indan-1,3-dione)tricarbonylchromium (17b). Prepared by hydrolysis of 1,3-bis(ethyle-
nedioxy)-2-ethyl(η6-indan)tricarbonylchromium (20b) (time of hydrolysis 2 h) in 15% yield as a red
semisolid material. For C14H10CrO5 (310.3) calculated: 54.19% C, 3.25% H; found: 54.62% C,
3.32% H. 1H NMR spectrum: 1.12 t, 3 H (CH3); 2.00 q, 2 H (CH2); 2.95 t, 1 H (CH); 5.62 m, 2 H
(C6H4Cr(CO)3); 5.90 m, 2 H (C6H4Cr(CO)3).
2-Ethyl-3-(2-hydroxyethoxy)(η6-2-inden-1-one)tricarbonylchromium (22b) was isolated from the
second band in 3.5% yield; red crystals, m.p. 103.5–105 °C. For C16H14CrO6 (354.2) calculated:
1
54.40% C, 3.70% H; found: 54.23% C, 4.13% H. H NMR spectrum: 1.17 t, 3 H (CH3); 1.62 bs, 1 H
(OH); 2.47 q, 2 H (CH2); 4.06 t, 2 H (OCH2); 4.52 t, 2 H (OCH2); 5.32 m, 1 H (C6H4Cr(CO)3); 5.62 app d,
2 H (C6H4Cr(CO)3); 6.03 d, 1 H, J = 6 (C6H4Cr(CO)3).
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Hrnciar P., Hrnciar P., Gajda, Svanygova, Toma:
2-Phenyl(η6-indan-1,3-dione)tricarbonylchromium (17d). Prepared in 84% yield by hydrolysis of
3-methoxy-2-phenyl(η6-2-inden-1-one)tricarbonylchromium (14d) (time of hydrolysis 1.45 h); deep-
blue crystals, m.p. 155 °C (dec.). For C18H12CrO5 (358.2) calculated: 60.34% C, 2.81% H; found:
1
60.45% C, 2.93% H. H NMR spectrum: 3.79 s, 1 H (CH); 5.37 bt, 1 H (C6H4Cr(CO)3); 5.70 m, 2 H
(C6H4Cr(CO)3); 6.12 bt, 1 H (C6H4Cr(CO)3); 7.35 bs, 5 H (C6H5).
2-(η6-Phenyltricarbonylchromium)indan-1,3-dione (8a).
Method A. Prepared in 90% yield by hydrolysis of 3-methoxy-2-(η6-phenyltricarbonylchromium)-
2-inden-1-one (15d) (time of hydrolysis 5 min) and was identical with the material obtained by rear-
rangement of 3-(η6-benzylidenetricarbonylchromium)phthalide (7a) (see above).
Method B. Prepared in 90% yield by hydrolysis of 1,3-bis(ethylenedioxy)-2-(η6-phenyltricarbo-
nylchromium)indan (21) (time of hydrolysis 1.45 h); identical with the product prepared from 15d
(vide supra).
Alkylation of 2-Alkyl(η6-indan-1,3-dione)tricarbonylchromium. General Procedure
Potassium carbonate (830 mg, 6 mmol) was added to a solution of the appropriate starting compound
(0.3 mmol) in dry acetone (15 ml). The mixture was set aside at room temperature and the reaction
course was followed by TLC. After no starting material was observed, the mixture was poured into
water and the product was extracted into diethyl ether. The ethereal solution was washed with water
and dried over sodium sulfate. After evaporation of the solvent, the residue was subjected to flash
chromatography on an SiO2 column in isohexane–ethyl acetate.
2-Ethyl-2-methyl(η6-indan-1,3-dione)tricarbonylchromium (2a). Prepared in 40% yield by alkyla-
tion of 2-methyl(η6-indan-1,3-dione)tricarbonylchromium (17a) with ethyl iodide; red crystals, m.p.
78–79 °C, identical with the product of complexation of 2-ethyl-2-methylindan-1,3-dione (1). Analy-
tical and NMR data are given on p. 489. The second product isolated was 3-ethoxy-2-methyl(η6-2-
inden-1-one)tricarbonylchromium (18) (8%); red crystals, m.p. 137 °C. For C15H12CrO5 (324.2)
calculated: 55.60% C, 3.73% H; found: 55.87% C, 3.83% H. 1H NMR spectrum: 1.45 t, 3 H (CH3);
1.99 s, 3 H (CH3); 4.52 q, 2 H (CH2); 5.32 m, 1 H (C6H4Cr(CO)3); 5.55 d, 2 H, J = 3
(C6H4Cr(CO)3); 6.00 d, 1 H, J = 6 (C6H4Cr(CO)3).
2-Ethyl-2-methyl(η6-indan-1,3-dione)tricarbonylchromium (2b). Prepared by alkylation of 2-
ethyl(η6-indan-1,3-dione)tricarbonylchromium (17b) with methyl iodide in 50% yield; red crystals,
m.p. 121–123 °C, identical with the product of complexation of 2-ethyl-2-methylindan-1,3-dione (1).
1
Our thanks are due to Dr E. Solcaniova and Dr E. Greiplova and their staff for H NMR measure-
ments and microanalyses, respectively. We thank also Slovak Ministry of Education (Grant No.
1/1443/94) for the financial support.
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