Synthesis of bromoalkenes and alkylidene dibromides by reactions of carbonyl compounds with 2,4,4,6-tetrabromo-2,5-cyclohexadienone in the presence of triphenylphosphine

Article abstract of DOI:10.1023/A:1012369232421

Reactions of aliphatic and aromatic aldehydes with the 2,4,4,6-tetrabromo-2,5-cyclohexadienone-triphenylphosphine complex result in formation of the corresponding geminal dibromides. Ketones react with the same complex to give vinyl bromides.

Full text of DOI:10.1023/A:1012369232421

Russian Journal of Organic Chemistry, Vol. 37, No. 1, 2001, pp. 52 55. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 1, 2001,
pp. 63 66.
Original Russian Text Copyright
2001 by Matveeva, Feshin, Zefirov.
Synthesis of Bromoalkenes and Alkylidene Dibromides
by Reactions of Carbonyl Compounds with 2,4,4,6-Tetrabromo-
2,5-cyclohexadienone in the Presence of Triphenylphosphine
E. D. Matveeva, D. B. Feshin, and N. S. Zefirov
Faculty of Chemistry, Moscow State University, Vorob’evy gory, Moscow, 119899 Russia
Received June 2, 2000
Abstract Reactions of aliphatic and aromatic aldehydes with the 2,4,4,6-tetrabromo-2,5-cyclohexadienone
triphenylphosphine complex result in formation of the corresponding geminal dibromides. Ketones react with
the same complex to give vinyl bromides.
We previously showed that 2,4,4,6-tetrabromo-2,5-
cyclohexadienone in the presence of triphenylphos-
phine is an efficient and mild reagent replacing the
hydroxy group by bromine in alcohols [1, 2] and
carboxylic acids [2]. The goal of the present work
was to examine reactions of the system 2,4,4,6-tetra-
bromo-2,5-cyclohexadienone triphenylphosphine (I)
with aliphatic and aromatic carbonyl compounds. As
model reaction we chose that between complex I and
octanal. In order to optimize the reaction conditions
we varied the solvent, the reactant ratio, and the order
of their mixing.
Taking into account that only one bromine atom
in the molecule of 2,4,4,6-tetrabromo-2,5-cyclohexa-
dienone (II) is active, the stoichiometric reactant ratio
carbonyl compound tetrabromide II triphenylphos-
phine (III) should be 1:2:2. Just this ratio was used
in the present study. It should be noted that applica-
tion of excess reagent (ratio 1:3:3) did not increase
the yield of the target products.
affects the product yield. When tetrabromocyclohexa-
dienone II and phosphine III were mixed before
addition of an aldehyde, the yield was lower. The
optimal yield of 1,1-dibromooctane (IV) (83%) was
obtained when reagent II was added to a solution of
triphenylphosphine and octanal in benzene (Table 1).
The procedure is general, and it can also be used to
synthesize other geminal dibromides of the aliphatic
series. We thus converted dodecanal and heptadecanal
into 1,1-dibromododecane and 1,1-dibromohepta-
decane, respectively, in 95 and 78% yield. We also
tried to involve in this process aromatic aldehydes.
By reaction of benzaldehyde with complex I we ob-
tained benzylidene dibromide in 90% yield. The yield
of p-bromobenzylidene dibromide from p-bromo-
benzaldehyde was 62%. p- and m-Nitrobenzaldehydes
reacted with complex I to afford 43 and 35% of
p- and m-nitrobenzylidene bromides, respectively
(Table 2).
Table 1 Reaction of octanal with the complex 2,4,4,6-
tetrabromo-2,5-cyclohexadienone triphenylphosphine
Yield of 1,1-dibromooctane, %
Solvent
method aa
method bb
Acetonitrile
Methylene
chloride
30
30
55
57
The major product of the reaction of I with octanal
was 1,1-dibromooctane (IV); also, 2,4,6-tribromo-
phenol and triphenylphosphine oxide were formed. As
solvents we tried acetonitrile, methylene chloride,
and benzene. The best yields were obtained in boiling
benzene. The order of mixing of the reactants also
Benzene
70
83
a
Preliminary preparation of complex I.
2,4,4,6-Tetrabromo-2,5-cyclohexadienone was added last.
b
1070-4280/01/3701-0052$25.00 2001 MAIK Nauka/Interperiodica

SYNTHESIS OF BROMOALKENES AND ALKYLIDENE DIBROMIDES
53
The purity of the products was checked by GLC.
Table 2. Reactions of the 2,4,4,6-tetraboromo-2,5-cyclo-
hexadienone triphenylphosphine complex with aldehydes;
temperature 79 C
1
Their structure was confirmed by H and 13C NMR
1
spectra. The H NMR spectra of 1,1-dibromoalkanes
contain a triplet at 5.7 ppm from the terminal CH
proton and a multiplet at 2.4 ppm from the neigh-
boring methylene group. The corresponding carbon
Product
Time, h
Yield, %
signals appear in the 13C NMR spectra at
46.3 and
1,1-Dibromooctane
1,1-Dibromododecane
1,1-Dibromoheptadecane
Benzylidene dibromide
p-Bromobenzylidene
dibromide
p-Nitrobenzylidene
dibromide
m-Nitrobenzylidene
dibromide
72
72
72
18
36
83
95
75
90
62
45.4 ppm, respectively, in keeping with Cpublished
data [3 6].
In the reaction of complex I with cyclohexanone
the only product was 1-bromocyclohexene. Its highest
yield (75%) was obtained in methylene chloride. By
reactions of I with acetophenone and 1,3-cyclohexane-
dione we obtained, respectively, -bromostyrene
(52%) and 3-bromo-2-cyclohexenone (88%) (Table 3).
Benzophenone failed to react with complex I. The
structure of the resulting bromoalkenes was confirmed
36
36
43
35
1
by the H and 13C NMR spectra which were consistent
and poured into a solution of 21 g of NaHCO3 in
180 ml of water. When gaseous products no longer
evolved, the precipitate was filtered off, washed with
hexane, dried in air, and recrystallized from chloro-
form. Yield 31 g (87%), mp 142 C [7].
with published data (see Experimental).
To conclude we can state that we have developed
a procedure for preparation of terminal geminal di-
bromoalkanes from aliphatic and aromatic aldehydes.
Ketones react with complex I to give exclusively
the corresponding bromoalkenes, and an additional
study is to be performed in order to elucidate how
the ketone structure affects the reaction direction.
Benzylidene dibromide. To a solution of 3.24 g
(0.0123 mol) of triphenylphosphine in 15 ml of dry
benzene we added with stirring under argon 0.525 g
(0.00495 mol) of benzaldehyde in 2 ml of benzene.
2,4,4,6-Tetrabromo-2,5-cyclohexadienone, 5.07 g
(0.0123 mol), was then added, and the mixture was
refluxed for 18 h. The mixture was filtered through
a layer of silica gel and evaporated, and the residue
was subjected to column chromatography using a 5%
solution of ether in hexane as eluent. Yield 1.115 g
EXPERIMENTAL
1
The H and 13C NMR spectra were recorded on
1
a VXR-400 instrument (400 MHz for H) using tetra-
methylsilane as internal reference. GLC analysis was
performed on a Chrom-5 chromatograph equipped
with a flame-ionization detector (SE-30 quartz capil-
lary column, 25 m 0.25 mm; carrier gas helium).
The progress of reactions was monitored by TLC on
Silufol plates; the chromatograms were developed first
with iodine vapor and second with aqueous potassium
permanganate. Preparative column chromatography
was performed on silica gel (Merck 60, 70 230 mesh,
and Chemapol, 5/40 and 40/100 m).
Acetonitrile was refluxed over P2O5, distilled, and
stored over calcium hydride. Methylene chloride was
refluxed over P2O5 and distilled. Benzene was re-
fluxed over metallic sodium and distilled. Triphenyl-
phosphine (III) was recrystallized from 2-propanol
and dried in a vacuum.
1
(90%). H NMR spectrum (CDCl3), , ppm: 6.65 s
(1H, CHBr2), 7.3 7.4 m (5H, Harom) (cf. [4, 8]); 13C
NMR spectrum (CDCl3), C, ppm: 41.11, 126.44,
128.65, 129.85, 141.86 (cf. [4]).
4-Bromobenzylidene dibromide. Following the
above procedure, from 0.733 g (0.00283 mol) of tri-
phenylphosphine, 0.25 g (0.00135 mol) of p-bromo-
benzaldehyde, and 1.163 g (0.0283 mol) of 2,4,4,6-
tetrabromo-2,5-cyclohexadienone we obtained (after
chromatographic purification using 1 : 4 toluene
hexane as eluent) 275 mg (62%) of 4-bromobenzyli-
1
dene dibromide. H NMR spectrum (CDCl3), , ppm:
6.59 s (1H, CHBr2), 7.4 7.55 m (4H, Harom). 13C
NMR spectrum (CDCl3), C, ppm: 39.61, 123.82,
128.09, 131.79, 140.87.
2,4,4,6-Tetrabromo-2,5-cyclohexadienone (II).
A mixture of 15 g (0.086 mol) of p-bromophenol,
45 ml of ethyl alcohol, and 45 ml of acetic acid was
cooled in an ice bath, and 13 ml (0.255 mol) of
bromine was added from a dropping funnel over
a period of 20 min. The mixture was stirred for 1 h
3-Nitrobenzylidene dibromide was synthesized
in a similar way from 1.82 g (0.00695 mol) of tri-
phenylphosphine, 0.5 g (0.0033 mol) of m-nitrobenz-
aldehyde, and 2.85 g (0.00695 mol) of 2,4,4,6-tetra-
bromo-2,5-cyclohexadiene. Chromatographic purifica-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 1 2001

54
MATVEEVA et al.
Table 3. Reactions of complex I with ketonesa
Initial ketone
Cyclohexanone
Product
Solvent
Temperature, C Time, h Yield, %
1-Bromocyclohexene
Acetonitrile
Methylene chloride
Benzene
81
40
79
24
24
24
30
75
20
1,3-Cyclohexanedione
Acetophenone
3-Bromo-2-cyclohexenone
-Bromostyrene
Methylene chloride
40
24
88
70b
o-Dichlorobenzene
180
72
15
a
Ratio ketone 2,4,4,6-tetrabromo-2,5-cyclohexadienone triphenylphosphine 1:2:2.
Ratio ketone 2,4,4,6-tetrabromo-2,5-cyclohexadienone triphenylphosphine 1:4:4.
b
tion using 1:4 toluene hexane as eluent gave 335 mg
(35%) of 3-nitrobenzylidene dibromide. H NMR
ppm: 0.91 t (3H, CH3), 1.2 1.4 m [16H, (CH2)8CH3],
1.5 1.6 m (2H, CH2CH2CHBr2), 2.39 m (2H,
CH2CHBr2), 5.7 t (1H, CHBr2). 13C NMR spec-
trum (CDCl3), C, ppm: 14.12, 22.69, 28.08, 28.25,
29.33 (2C), 29.45, 29.57 (2C), 31.89, 45.44, 46.18.
1
spectrum (acetone-d6, HMDS), , ppm: 7.29 s (1H,
CHBr2), 7.72 t (1H, Harom), 8.06 8.1 m (1H, Harom),
8.18 8.22 m (1H, Harom), 8.44 t (1H, Harom).
13C NMR spectrum, (acetone-d6), C, ppm: 38.74,
120.05, 123.3, 129.43, 129.98, 131.82, 143.11.
1,1-Dibromoheptadecane was synthesized in
a similar way from 1.29 g (0.00492 mol) of triphenyl-
phosphine, 0.5 g (0.00196 mol) of heptadecanal, and
2.015 g (0.00492 mol) of 2,4,4,6-tetrabromo-2,5-
cyclohexadienone. The product was purified by
chromatography using a 5% solution of ethyl acetate
4-Nitrobenzylidene dibromide was synthesized in
a similar way from 0.91 g (0.0034 mol) of triphenyl-
phosphine, 0.25 g (0.00165 mol) of p-nitrobenzalde-
hyde, and 1.425 g (0.0034 mol) of 2,4,4,6-tetrabromo-
2,5-cyclohexadienone. Chromatographic purification
with 1:4 toluene hexane as eluent gave 220 mg
(43%) of 4-nitrobenzylidene dibromide. 1H NMR
spectrum (CDCl3), , ppm: 6.58 s (1H, CHBr2), 7.73
7.77 d (2H, Harom), 8.23 8.27 d (2H, Harom) (cf. [9]).
13C NMR spectrum (CDCl3), C, ppm: 38.13, 124.03,
127.71, 134.89, 147.82.
1
in hexane. Yield 580 mg (75%). H NMR spectrum
(CDCl3), , ppm: 0.91 t (3H, CH3), 1.22 1.4 m [26H,
(CH2)13CH3], 1.5 1.6 m (2H, CH2CH2CHBr2),
2.39 m (2H, CH2CHBr2), 5.7 t (1H, CHBr2). 13C
NMR spectrum (CDCl3), C, ppm: 14.13, 22.09,
22.71, 28.27, 29.35, 29.38, 29.47, 29.59, 29.65, 29.68
(3C), 29.72 (2C), 31.93, 45.46, 46.29.
1,1-Dibromooctane (IV) was obtained in a similar
way from 2.56 g (0.00976 mol) of triphenylphosphine,
0.5 g (0.0039 mol) of octanal, and 4.0 g (0.00976 mol)
of 2,4,4,6-tetrabromo-2,5-cyclohexadienone, followed
by chromatographic purification with a 5% solution
1-Bromocyclohexene was synthesized in a similar
way from 3.16 g (0.012 mol) of triphenylphosphine,
0.5 g (0.00483 mol) of cyclohexanone, and 4.95 g
(0.012 mol) of 2,4,4,6-tetrabromo-2,5-cyclohexadi-
enone in dry methylne chloride. The product was
purified by chromatography using a 5% solution of
1
of ethyl acetate in hexane. Yield 835 mg (83%). H
1
NMR spectrum (CDCl3), , ppm: 0.91 t (3H, CH3),
1.2 1.4 m [10H, (CH2)5CH3], 1.5 1.6 m (2H,
CH2CH2CHBr2), 2.39 m (2H, CH2CHBr2), 5.7 t
(1H, CHBr2) (cf. [3, 5]). 13C NMR spectrum (CDCl3),
C, ppm: 14.06, 22.59, 28.08, 28.21, 28.99, 31.65,
45.45, 46.31.
ethyl acetate in hexane. Yield 525 mg (75%). H
NMR spectrum (CDCl3), , ppm: 1.5 1.9 m (4H),
2.0 2.2 m (2H), 2.35 2.45 m (2H), 6.0 6.05 m (1H)
(cf. [10]). 13C NMR spectrum (CDCl3), C, ppm:
21.04, 24.43, 27.35, 35.10, 122.25, 128.77.
3-Bromo-2-cyclohexenone was synthesized in
a similar way from 1.23 g (0.0468 mol) of triphenyl-
phosphine, 0.25 g (0.00223 mol) of 1,3-cyclohexane-
dione, and 1.92 g (0.0468 mol) of 2,4,4,6-tetrabromo-
2,5-cyclohexadienone in dry methylene chloride. The
product was purified by chromatography using 1:1
hexane chloroform as eluent. Yield 345 mg (88%).
1H NMR spectrum (CDCl3), , ppm: 1.9 2.05 m
1,1-Dibromododecane was obtained in a similar
way from 1.78 g (0.00679 mol) of triphenylphosphine,
0.5 g (0.00272 mol) of dodecanal, and 2.784 g
(0.00679 mol) of 2,4,4,6-tetrabromo-2,5-cyclohexadi-
enone. Chromatographic purification using a 5% solu-
tion of ethyl acetate in hexane gave 840 mg (95%) of
1
1,1-dibromododecane. H NMR spectrum (CDCl3), ,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 1 2001

SYNTHESIS OF BROMOALKENES AND ALKYLIDENE DIBROMIDES
55
(2H), 2.2 2.35 m (2H), 2.65 2.8 m (2H), 6.4 t (1H)
(cf. [11]). 13C NMR spectrum (CDCl3), C, ppm:
22.83, 36.13, 36.26, 132.46, 149.91, 196.08 (cf. [12]).
2. Matveeva, E.D., Podrugina, T.A., Sandakova, N.G.,
and Zefirov, N.S., Sbornik trudov konferentsii
Peterburgskie vstrechi-98 (Proc. Conf. St. Peters-
burg Meetings-98 ), St. Petersburg, 1998, p. 175.
-Bromostyrene was synthesized in a similar way
from 1.14 g (0.0024 mol) of triphenylphosphine,
0.25 g (0.002 mol) of acetophenone, and 1.79 g
(0.0042 mol) of 2,4,4,6-tetrabromo-2,5-cyclohexadi-
enone in o-dichlorobenzene. Subsequent chromato-
graphic separation (using petroleum ether as eluent)
gave 450 mg of a mixture of o-dichlorobenzene and
-bromostyrene at a ratio of 7:1 (according to the
1H NMR data). The yield of -bromostyrene was
15%. It was identified by the signals of the methylene
[ , ppm: 5.76 d (1H), 6.10 d (1H)] and aromatic
protons [ , ppm: 7.42 (5H)] (cf. [13]).
Reaction of complex I with benzophenone.
A mixture of 0.863 g (0.00329 mol) of triphenylphos-
phine, 0.2 g (0.0011 mol) of benzophenone, and
1.348 g of 2,4,4,6-tetrabromo-2,5-cyclohexadienone
in dry methylene chloride, anhydrous acetone, or
anhydrous toluene was refluxed for 3 days. Chromato-
graphic separation using 1:1 hexane benzene gave
99% of initial benzophenone (retention time 3.72 min;
oven temperature 220 C, injector temperature 270 C).
3. Villieras, J., Tarhouni, R., Kirscheger, B., and
Rambaund, M., Bull. Soc. Chim. Fr., 1985, no. 5,
p. 825.
4. Hoffmann, R.W. and Bovicelli, P., Synthesis, 1990,
p. 657.
5. Martinez, A.G., Fernandez, A.H., Alvarez, M.R.,
Fraile, A.G., Calderon, J.B., and Barcina, J.O.,
Synthesis, 1986, no. 12, pp. 1076 1078.
6. Kuchin, V.A., Markova, S.A., and Tolstikov, G.A.,
Zh. Obshch. Khim., 1988, vol. 58, no. 4, p. 934.
7. Tsubota, M., Iso, M., and Suzuki, K., Bull. Chem.
Soc. Jpn., 1972, vol. 45, no. 4, p. 1252.
8. The Aldrich Library of NMR Spectra, 1974, vol. IV,
p. 38.
9. Mironov, V.F., Ofitserov, E.N., Sinyashina, T.N.,
and Konovalova, I.V., Zh. Org. Khim., 1990, vol. 26,
no. 12, p. 2570.
10. Newnan, H. and Seebah, D., Chem. Ber., 1978,
vol. 111, no. 8, pp. 2785 2812.
11. Piers, E., Grierson, J.R., Lan, Ch.K., and Nika-
gura, I., Can. J. Chem., vol. 60, no. 2, p. 210.
12. Hofle, G., Tetrahedron, 1976, vol. 32, no. 12,
REFERENCES
p. 1431.
1. Matveeva, E.D., Podrugina, T.A., and Zefirov, N.S.,
13. Soderquist, J.A. and Hassner, A., J. Org. Chem.,
Mendeleev Commun., 1998, no. 1, pp. 21 23.
1983, vol. 48, no. 11, p. 1801.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 1 2001