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Facile Synthesis of 4-Acyl-5-alkyl-2 3-dioxo-2 3-dihydrofurans and Alkylidenebutenolides.

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[15] R. Schwesinger, K. Piontek, W. Littke, 0. Schweikert, H. Prinzbach, Tetruhpdron Lett. 23 (1982) 2427; R. Schwesmger, K. Piontek, W. Littke, H.
Prinzbach, hid. 26 (1985) 1201; R. Schwesinger, Inorg. Chim. Acla f55
(1989) 145.
[16] Crystal structure data for 4: The structure was solved by direct methods
(SDP MULTAN 82). Space group P2,2,2, (No. 19), u = 4.780(1),
h = 9.407(1), c = 13.640(1)A, V = 613.3 A3, Z = 4, @ = 1.387 gcm-',
NONIUS diffractometer CAD4 with Cu,, radiation, 20 = 4"-150", 782
reflections were measured, 692 were considered as observed (I > 2 4 4 ) .
R = 0.054. Further details of the crystal structure investigation may be
obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur
wissenschaftlich-technische Information mbH, D-7514 EggensteinLeopoldshafen 2 (FRG), on quoting the depository number CSD-54522.
the names of the authors, and the journal citation.
[17] W Littke. U Driick, Angew,. Chem. 86 (1974) 557; Angew. Chem. Int. Ed.
Engl. 13 (1974) 539.
On the other hand, 1,3-diphenyl-l,3-propanedione(1 a) is
known to react smoothly with 2a in diethyl ether to give
4-benzoyl-2,3-dioxo-5-phenyl-2-3-dihydrofurans
4a.['] Under the same conditions, we obtained 5-tert-butyl-2,3-dioxo4-pivaloyl-2,3-dihydrofuran
(4b) from I b and 2a (Table 1).
l a : R = Ph
l b : R = tBu
Facile Synthesis of 4-Acyl-5-alkyl-2,3-dioxo2d-dihydrofurans and Alkylidenebutenolides **
By Rolf W Saalfank* and Thomas Lutz
Dedicated to Professor Hans Jiirgen Bestmann on the occasion of his 65fh birthday
Earlier we obtained the tetranuclear metal chelate complexes 3 by reaction of diethyl malonate with methylmagnesium iodide or the system methyllithium/metal dichloride
and with oxalyl chloride (2 a) at -78 "C in tetrahydrofuran
followed by workup with aqueous ammonium chloride solution."] Our attempts to generalize this concept have failed so
far. Under the conditions employed, CI, y-dicarbonyl compounds with alkyl or aryl substituents do not undergo spontaneous self-assembly to form adarnantanoid chelate complexes of type 3.
4a: R = Ph
4b: R = ~ B u
2a
Apparently, the situation is completely different for a,ydiketones l c - f containing at least one a-hydrogen in R'
and/or R2. Ziegler et a1.'' have reported that they were
unsuccessful in preparing the analogous furan-2,3-diones 4
by reaction of acetylacetone (I c), benzoylacetone (1f), etc,
with 2a. In principle, however, it should be possible for the
reaction of such a,y-diketones and 2a either to give tetranuclear chelate complexes of type 3 via template coupling or to
afford furan-2,3-diones 4 via intramolecular ring-closure.
xhx
2a: X = CI
2b:X=Br
0
L
R
MSCI2
1 c-f
1. MeMgI or
MeLi/MCI2
5
4c-f
3. NH,CI/H2O
BrSiMe3/
HN(SiMe&
OSiMe,
-
H
&- R
0
RJ
6
3
1.4
I
c
d
e
f
Me
Et
CH2CHMe2
Ph
Me
CHMe,
I
3 1
a
b
c
d
R2
[*I
I
Prof Dr. R. W. Saalfrank, DipLChem. T. Lutz
Institut fur Organische Chemie der Universitat Erlangen-Niirnberg
Henkestrasse 42, D-8520 Erlangen (FRG)
[**I 4-Acyl-5-aIkyl-2,3-dioxo-2,3-dihydrofurans,
Part 1. This work was supported by the Deutsche Forschungsgemetnschaft and the Fonds der
Chemischen Industrie.
AnReu,. Chem. In!. Ed. Engl. 29 (1990) No. 9
0 VCH
Verlugsgesellschuft mbH, 0-6940 Weinheim, 1990
0570-08~3/90/0909-1041$3.50+.25/0
1041
Our experience with metal-assisted synthesis of tetranucleride. The new procedure is a considerable extension of the
a r chelate complexes 3 made it reasonable to attempt the
methods previously used for the synthesis of 2,3-dioxo-2,3reaction of a,y-diketones containing an a-hydrogen with 2a
dihydrofurans['. 41 and is strikingly simple to carry out.
in diethyl ether in the presence of magnesium chloride.[31
Under these conditions, we obtained the previously unExperimental Procedure
known compound 4-acetyl-5-methyl-2,3-dioxo-2,3-dihydro4b: A solution of 2 a (6.35 g, 50 mmol) in 20 mL of n-hexane was added
furan (4c) from l c and 2a. According to the 'H NMR
dropwise over 0.5 h to a solution of 1 b (9.2 g, 50 mmol) in 30 mL of diethyl
ether. Yellow crystals of 4b were collected after 3 d.
spectrum, 4c exists exclusively in the keto form in deute4c, Sb,c: Magnesium chlorlde (1.2g) was added to a solution of l c - e
rochloroform at - 55 "C (Table 1). At 27 " C , however, 4c is
(50 mmol) in 50 mL of diethyl ether and the resulting mixture was added over
in equilibrium with approximately 10 % of the correspond0.5 h to a vigorously stirred solution of Za (6.35 g, 50 mmol) in 25 mL of
ing enol 5a.
n-hexane at 0 'C ( - 10 "C for 4c). After a reaction tlme of 3 h at 20 "C (- 10 'C
for 4c), 25 mL of n-hexane was added, the reaction solution was filtered, the
Surprisingly, the magnesium chloride-induced reaction of
filtrate was concentrated to 30 YOusing a rotory evaporator (water bath temperthe unsymmetrically substituted diketones 1 d, e with 2 a proature 20'C for 4c), and the crystals were isolated (in the dark for 4 c).
ceeds both regio- and stereospecifically and affords excluCompound 4 f was obtained analogously (addition of magnesium chloride
sively enols 5 b, c (Table 1). The information provided by an
was not necessary) from 1 f (8.11 g, 50 mmol) and 2b (10.79 g, 50 mmol).
6b, e : Hexamethyldisilazane (1.78 g, 11 mmol) and bromotrimethylsilane
NOE difference spectrum of the silyl enol ether 6 b supports
(1.84 g, 12 mmol), each in 5 mL of diethyl ether, were added in succession to a
the Z configuration proposed for the alkylidenebutenolides
solution of Sb, c (10 mmol) in 30 mL of diethyl ether at -78'C. The resulting
5b, c. Enols 5a-c react readily with bromotrimethylsilane in
reaction mixture was allowed to warm over 20 h to 20°C and filtered. The
the presence of hexamethyldisilazane to give the correspondsolvent was removed with a rotory evaporator and the product distilled.
ing silyl enol ethers 6a-c; compound 6 a is very sensitive,
Received: April 19, 1990 123923 IE]
whereas 6 b and 6c can be easily purified by kugelrohr distilGerman version: Angew. Chem. 102 (1990) 1064
lation (Table l).
Table 1. Data for the compounds 4b,c,f, Sb,c, and 6a-c[a]
4b: 7.7g(65%). m.p. 94°C (from CHCI,). IR: P = 1740, 1670, 1645 (C=O),
1590cm-'(C=C). ' H NMR: 6 = 1.24, 1.32(seach, 9Heach,2(CH3),). ',C
NMR: 6 = 27.32, 27.58 ((CH3)3), 36.64, 44.81 (Cq), 119.66. 152.71 ( = C ) ,
177.49, 189.31, 206.31 (C=O). MS: m/r 238 ( M a )
4 c : 4.8 g (62%). m.p. 68°C (dec.; from ether/hexane (2jl)). IR: D = 1780, 1680
( c = o ) , 1600cm-' (C=C). ' H NMR (-55°C): 6 = 2.55, 2.88 ( S each, 3 H
each, 2CH3).
NMR (-55°C): 6 = 17.77, 30.66 (CH,). 116.56, 152.26
(=C). 175.68, 192.24, 192.59 (C=O). MS. m/z 154 (Ma)
4 f : 7.4 g(68%),m.p. 69"C(dec.;fromether/hexane(2/1)). IR: 8 = 1755, 1685,
1645(C=O), 1590cm-'(C=C). ' H N M R : 6 = 2.08(s,3H,CH3),7.60-8.05
(m, 5 H , C,H,). 13C NMR: 6 = 29.66 (CH,), 92.32, 128.02 ( = C ) , 129.21,
129.85, 134.37, 137.84(phenyl-C), 144.40, 165.14, 189.13 (C=O). MS: m / z 216
(M9
CAS Registry numbers:
l b , 1118-71-4; l c , 123-54-6; I d , 3002-24-2; l e , 3002-23-1; I f , 93-91-4; 2a,
79-37-8; Zb, 15219-34-8; 4b, 128751-99-5; 4c, 128732-08-1; 4f, 128732-09-2;
Sa, 128732-15-0, 5b, 128732-10-5; Sc, 128732-11-6; 6a, 128732-12-7; 6b,
128732-13-8, 6c. 128732-14-9.
[l] R. W. Saalfrank, A. Stark, M. Bremer, H.-U. Hummel, Angew. Chem. I02
(1990) 292; Angen. Chem. Int. Ed. EngL 29 (1990) 311.
[2] E. Ziegler, G. Kollenz, H. Igel, Monutsh. Chem. I02 (1971) 1769.
[3] A general discussion on the increase in acidity due to metal complexation is
found in R. P. Houghton, Metal Complexes in Orgunic Chemistry, Cambridge University Press, Cambridge 1979, pp. 114-116; cf. also M. W.
Rathke, P. J. Cowan, J. Org. Chem. 50 (1985) 2622; M. W. Rathke, M. A.
Nowak, Synlh. Commun. 15 (1985) 1039; J. Skarzewski, Tetrahedron 45
(1989) 4593; S . Shambayati, W. E. Crowe, S. L. Schreiber. Angew. Chem.
102 (1990) 273; Angew. Chem. In!. Ed. Engl. 29 (1990) 256.
141 S. Muria, K. Hasegawa, N Sonoda, Angew. Chem. 87 (1975) 668; Angeu..
Chem. Int. Ed. Engl. 14 (1975) 636, H. Alper. G . Vasapollo, Tetrahedron
Lett. 30 (1989) 2617
5 b . 6.9 g (82%), m.p. 111 "C (dec.; from CHCI,). IR. P = 1765. 1740 (C=O),
1640cm-' (C=C). ' H N M R : 6 = 1.98(d,3H,CH3),2.55(s, 3H,CH3),5.96
(4. 1 H, =CH), 9.95 (s, br, OH). "C N M R : 6 = 11.50, 30.70 (CH,), 110.52,
116.94. 143.20, 149.95 (=C), 164.22, 195.64 (C=O). MS. m/z 168 (Ma)
5 e : 7.6 g (78%). m.p. 73 'C (dec.; from CHCI,). IR: P = 1780, 1740 (C=O).
1640cm-' (C=C). 'H NMR: 6 = 1.18 (d. 6 H , CH,), 2.58 (s, 3H. CH,). 3.06
( m , l H , C H ) , 5 . 6 6 ( d , l H , =CH),9.87(~,br,lH,OH).'~CNMR:6=22.66,
30.81 (CH,), 26.06(CH), 117.82. 122.81, 141.01, 149.13 (=C), 164.46, 195.34
Tetraphenylallylsodium Diethyl Ether: A Contact
(C=O). MS: m/r 196 ( M e )
Ion
Pair with an Intramolecular Na@ Sandwich**
6 a . 1.8 g (78%); because of the low stability, only an 1H NMR spectrum was
recorded. ' H NMR (60 MHz): 6 = 0.37 (s, 9 H . Si(CH,),), 2.46 (s. 3H. CH,),
By Hans Bock,* Klaus Ruppert, Zdenek Havlas, and
5.08, 5.57 (d each, 1 H each, 2 = C H )
Dieter Fenske
6b: 2.1 g(86%), b.p. 87"C/0.04 Torr. IR: P = 1770. 1690 (C=O), 1615cm"
(C=C). 'HNMR:6=0.37(s,9H,Si(CH,),),1.85(d,3H,CH3),2.46(s,3H,
Dedicated to Professor Paul von Ragut Schleyer on the occaCH3),6.03(q,1H, =CH).'~CNMR:d=O.63(Si(CH,),),11.18,31.02(CH3),
sion of his 60th birthday
111.00, 122.46, 143.30,145.56(=C),164.77, 192.98(C=0).MS:m/z240(MD)
6 ~2.4g(91%).
:
b.p.91"C/O.O4Torr. IR: P = 1760, 168O(C=O), 1600cm'l
The successful growth of a single crystal of the paramag(C=C) 'H NMR: 6 = 0.18 (s, 9 H , Si(CH,),), 1.18 (d, 6 H , CH,), 2.45 (s. 3H,
netic contact ion pair [(fluorenone'@){Na@(dme),)],
CH,), 2.85 (m, 1 H, CH), 5.88 (d, 1 H, =CH). "C NMR: 6 = 0.82 (Si(CH3)3),
22.67, 31.72 (CH,), 25.72 (CH), 122.67, 123.36, 141.12, 145.75 (=C), 164.95,
(dme = dimethoxyethane)[21has been our starting point in
193.21 (C=O). MS: m/z 268 ( M a )
the use of MNDO energy hypersurface calculations to dis-
*
[a] IR spectra: IR-5 instrument (Beckman), in KBr, except for 6b. c (neat)
'H/"C NMR spectra: JNM GX-400 instrument (Jeol); solvent, CDCI,. TMS
int., except for 4 f ([D,]acetone). Mass spectra. Varian MAT-CH-4B, direct
inlet, 70 eV.
The reaction of benzoylacetone (1 f) with 2 a in the presence of magnesium chloride is much more complicated and
gives a mixture of substances that is very difficult to separate.
On the other hand, reaction with oxalyl bromide (2b) under
otherwise identical conditions smoothly leads to 4-acetyl2,3-dioxo-5-phenyl-2,3-dihydrofuran
(4f) (Table 1). Moreover, we found that the use of the more reactive 2 b obviates
the necessity of activating 1 f by addition of magnesium chlo1042
0 VCH
Verlugsgesellschuft mhH. 0-6940 Wemheim, 1990
cover other organic salts in which positive or negative
charges bring about similarly amusing perturbations, such
as the twisting of the two molecular halves in ethene di[*] Prof. Dr. H. Bock, DipLChem. K. Ruppert, Dr. 2. Havlas
Institut fur Anorganische Chemie der Universitat
Niederurseler Hang, D-6000 Frankfurt am Main 50 (FRG)
Prof. Dr. D. Fenske
Institut fur Anorganische Chemie der Universitit
Engesserstrasse, D-7500 Karlsruhe (FRG)
[**I Structures of Perturbed ~i Systems, Part 4, and Electron Transfer and ton
Pair Formation, Part 19. This work was supported by the Deutsche
Forschungsgemeinschaft, the Fonds der Chemischen Industrie, the Alexander von Humboldt-Stiftung ( Z . H.), and the State of Hesse. Parts 3 and
18. [ l a ] and [l b].
0S70-0833/90/0909-1042$3.50+.25/0
Angew. Chem. Int. Ed. Engl. 29 (1990) N o 9
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