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Dibenzofurans by Intramolecular Ring Closure Reactions.

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anhydrous ethanol/ether gave colorless crystals decomposing
in the range 110-1 15'C.
Received: March 11. 1974 [Z 25b IE]
German version- Angew. Chem. 86,477 (1974)
- - ..
[I]
G. D. Appleyard and C. J M. S t i r h y , J. Chem. SOC. C 1969, 1904.
[2] J W B u f f v , P. D. How,i.s, and C. J . M. S t i r h y , J C. S. Perkin I 1973,
59
[3] J . W B r i f r ~P.
, D. Houes, and C . J . M. Stirling, J. C. S. Perkin I 1973,
65.
[4] A . Trruda and Y Kiskida, Chem. Pharm. Bull. 17, 974 (1969).
[5] L. Vwiiurd and G . Pourcrlor. C. R. Acad. Sci. C 273, 1190 (1971).
[6] A . Trrudu and Y. Kishido, Chem. Pharm. Bull. 18, 490 (1970).
[ 7 ] W Rird and R. Neidhordr, Liehigs Ann. Chern. 739, 155 (1970).
dium acetate and 2,4-pentanedione (for conditions see Table
1).
Compound ( 1 ) which was isolated by fractional distillation
crystallizes as white leaflets (from ethanol), m. p. 62--64°C
(64"C[31).Elemental analysis, mass spectrum, and 'H-NMR
spectrum are in accord with the structure given. The dimers
(2) were isolated from the oily fraction (b.p. 125 to
15OoC/0.5torr) by chromatography (alumina, hexane/benzene,
1 : 1). The gas chromatogram displays three isomers; a molecular peak is observed in the mass spectrum.
Dibenzofuran is known to be formed as a by-product in
poor yield when diphenyl ether is heated to 700'C in a glass
[X] H .
Bruitti, G. Sfrohl,and H. Corder, Angew. Chem. 86, 477 (1974);
Angew. Chem. internat. Edit. 13. 469 (1974).
[9] J . K . Crundull and S. A. Sojhu, J . Amer. Chem. SOC. 94. 5084 (1972).
and references cited therein.
Table 1 . Products of intramolecular ring-closure reactions and dimers (determined by gas chromatography). Reaction
conditions: starting material, 15.0g; Pd(OAc)2, 0.15 mmol; 2.4-pentanedione 0.15mrnol; N 2 / 0 2 ( I : I ) 50kg/crn2; 5 h
at 150 C (yield based on reacted palladium acetate).
- __
-
Starting material
-
~._____
Cyclized product
Yield [moI-%]
______
~~
Diphenyl ether
Diphenyl ether [a]
Di-p-tolyl ether
Di-p-tolyl ether [h]
m-Tolyl p-tolyl ether
m-Tolyl p-tolyl ether [b]
m-Tolyl p-tolyl ether [a]
o-Tolyl p-tolyl ether [a]
4-Nitrodiphenyl ether [a]
Dibenzofuran
Dibenzofuran
2.8-Dimethyldibenzofuran
2,X- Dimethyldibenzofuran
2,7-Dirnethyldibenzofuran
2,7-Dirnethyldibenzofuran
2.7-Dimethyldihenzofuran
2,6-Dimet hyldibenzofuran
2-Nitrodibenzofuran [d]
Benzophenone [a]
4,4'-Dimethylbenzophenone [a, c]
Fluorenone
3,6-Dimethylfluorenone
[a]
(b]
[c]
[d]
Dirnerized products
yield [mol-%]
8090
10400
X 540
9 360
1530
9220
330
5 230
3710
2 530
I470
1310
330
680
590
I10
traces
650
1120
690
traces
730
With addition of ethylene diacetate ( 5 ml).
With addition of rnesitylene (5ml).
At IXO'C: the reaction gave a very poor yteld a t 150 C.
Yellow needles, m. p. 150--lSl'C (150.5--151.5 'C [7]), molecular ion at m / r 213.
Dibenzofurans by Intramolecular Ring Closure Reactions
By Akinori Shiotuni and Hiroshi Itatuni[']
Palladium compoundsare very important in the homogeneous
catalysis of organic reactions['! The oxidative coupling reactions of aromatic compounds were investigated in the presence
of palladium acetate under oxygen pressure. The dimerized
compounds were obtained in good yield in the absence of
solvent''!
We have now accomplished an intramolecular ring-closure
reaction to give 2&dimethyldibenzofuran ( I ) in the corresponding reaction of di-p-tolyl ether in the presence of palla-
The method developed by us is suitable for the preparation of substituted dibenzofurans (see Table 1) which have
hitherto only been accessible by laborious multistep synthesesI5]. Substituents on the benzene nucleus favor intramolecular ring closure and suppress dimerization owing to the
reduced interaction between the molecules. Solvents have the
same effect['].
The analogous reaction of rn-tolyl p-tolyl ether gave white
needles (m. p. 82-83 "C). Elemental analysis and mass spectrum are in accord with the expected structure of a 2,7- or
2$dimethyldibenzofuran; the 'H-NMR spectrum showed 2,7dimethyldibenzofuran (3) t o be present [(in CCI,): 6 = 2.47
(2 CH3), 7.02 (H8), 7.10 (H3),7.28 (H6), 7.35 (H4), 7.60 (H'),
7.67 (H');
J1.3=1.5Hz,
53.4=7.5Hz,
Jl.4~0.6H2,
56.8=1.2HZ, J8,9=7.5HZ, J6,9=0.5H~].
In the same way, fluorenones are formed from benzophenones,
although in low yields (see Table I). Diphenyl sulfide, diphenyl
sulfone, N,N-diphenylacetamide, and phenyl benzoate could
not be reacted.
Received: April 1 I. 1974 [Z 27 IE]
German version: Angew. Chem. 86,478 (1974)
[ I ] a ) R Hiifrrl,Synthesis 1970,225; b) P . M . Mair1i.s.The OrganicChemistry
of Palladium. Vol. I and 2. Academic Press, New York 1971.
[*I Dr. A. Shiotani and Dr. H. ltatani
Polymer Research Laboratory, UBE Industries Ltd.
8-2. Goi-Minamikaigan, Ichihara-city, Chiba. 290 (Japan)
Angew. Chem. inrrrnnt. Edit.
1 Vol. 13 (1974) / No. 7
[2] H . Itutani and H . Yoshimoro. J. Org. Chem. 38, 76 (1973); Bull. Chern.
Soc. Jap. 46, 2490 (1973).
[3] Y Siryii and H . Shindo, J. Pharm. SOC.Jap. 53, 97 (1933).
[4] R . Nokoi, Bull. Chem. SOC.Jap. 5 , 136 (1930).
471
[ S ] a ) W E. P d i u m and R. W Strusshury, J. Org. Chem. 26. 4749 (1961).
b) D. F . DeTur and 7: E. Whirdey, J. Amer Chem. SOC. 79. 2498 (1957).
[6] The solvent should not undergo dimerization.
2
(3)
t120
- 2 "0
*
Ph-CH-C
I
OH
112-C H2-CH-Ph
I
(4)
OH
[7] M . J . S. Drwur and D. S. C'rch, J. Chem. Sac. 1957, 345
Hydroxylating Dimerization of Styrene at the
Anode['] [**I
By Eberkard Steckkan and Harts Sckafer"]
The dimerization and functionalization of electron-rich olefins
at the graphite anode has hitherto been performed mainly
in methanolic solution. The process yields predominantly 1,4dimethoxylated butane derivatives in good yields['].
We are currently investigating the introduction of other functional groups by variation of the nucleophile. Electrolysis
in aqueous electrolytes should lead to the formation of substituted 1,4-butanediols and tetrahydrofurans.
Ph
P h = C6H5
The potential-controlled preparative electrolysis of styrene ( I )
( E = + I .2 to + 1.6 V relative to Ag/AgCl) at graphite electrodes
affords the products ( 4 ) to (10) in aqueous acetonitrile or
a dichloromethane/water suspension (Table 1). Their formation is readily interpreted as proceeding via the intermediate
dication (3) and its deprotonation or solvolysis.
COCH,
of + 1.6V (relative to Ag/AgCl), and a current density of
25mA/cmZ until consumption of 0.1 F. After extraction of
the electrolyte with ether and dichloromethane and distillation
of the solvent and unreacted styrene there remains 19g of
crude product. The crude product still contains small amounts
of olefin and supporting electrolyte. 2.35 g was separated by
column chromatography over silica gel (270g; eluant :light
Table 1. Results of hydroxylating anodic dimerization of styrene in aqueous electrolytes. The compounds ( 4 ) t o
( 1 0 ) were characterized by C,H analysis and/or their IR, NMR, and mass spectra, as well as comparison with
authentic samples. Conditions: Electrolysis was performed at a potential of + 1.2 to + 1.6V relative to Ag/AgCl
and a current density between 20 and 30 mA/cm2 u p to a conversion of 0.1 F.
Products
CHACNlstyrenelH2O
= 5 : 2 : I (v/v/v),
TEA-pTS [a] (0.6 M)
Electrolyte
CHICN/styrene/H >O
= 5 . 2 : I (v/v/vj,
TBA-HSO, [ d ] (0.4M)
yield % [c]
yield YO[c]
8.5
38
4
14
40
9
-
-
12
12
4
3.5
CH2C12jstyrene/H20[b]
= 5 12 : 1 (v/v/v),
TBAzHSO1 [a] (0.5 M)
yield % [c]
-
[a] TEA-pTS = tetraethylammonium p-toluenesulfonate; TBA-HS04 = tetrabutylammonium hydrogen sulfate.
[b] In CH2C12/styrene/H20= 6 : 2 : 1 (v/v/v) TEA-pTS (0.56M) styrenc telwners and polymers are mainly formed.
The anode is strongly passivated. However, in the electrolytes used here no passivation is observed.
[c] Based on the current consumption.
[d] Plus 14% of dehydrated (6), i.u. I-phenyI-I,2-dihydronaphthalene.
2,s-Diphenyltetrahydrofuran (S)r31
A sample of styrene (40ml) in an electrolyte consisting of
dichloromethane (100 ml), water (20 ml), and tetrabutylammonium hydrogen sulfate (30g) is electrolyzed at graphite
electrodes(P 127,Sigri, Meitingen) at 2 5 T , an anode potential
["I
Dr. E. Steckhan and Prof. Dr. H. J. Schafer
Organisch-Chemisches Institut der Universitiit
44 Munster, OrlCdns-Ring 23 (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie
petroleum/ether 3 :Iv/v).
, Compound ( 5 ) (720mg), b.p. 190 to
as the second fraction.
*930C/12torr*was
Received: April 16, 1974 [Z 28 IE]
German version: Angew. Chem. 86. 480 i1974)
[ I ] Presented in part at the XXlVth IUPAC Congress, Hamburg, September
1973.-Anodic Oxidation of Organic Compounds, Part 12.-Part 11: D.
Kuch and H . Schufer, Angew Chem. 85, 264 (1973): Angew. Chem. internat.
Edit. 12, 245 (1973).
[**I
121 H . Srhafer and E Sreckhun, Angew. Chem. 81, 532 (1969); Angew. Chem.
internat. Edit. 8. 518 (1969); H. Schafer, Chem.-1ng;Tech. 42, 164 (1970);
472
Angrw. Chem. internat. Edit.
1 Val. 13
(1974)
/ No. 7
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