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Dimethyl 3 8-Heptalenedicarboxylate.

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been provided by %Z-NMR spectroscopy for heptalenei2I,
there can be no doubt that the simplicity of the 'H-NMR
spectrum of (10) is likewise due toa dynamic process of this kind
~
The UV spectrum
and not to delocalization of the 1 2 system.
of (10) [Lmsx (cyclohexane)=250 ( ~ = 2 3 4 0 0sh), 266 (26350),
356nm (7200)] shows a slight red shift compared to that of the
parent compound, as would beexpected from the influence ofthe
bromine substituents.-Detailed
studies on (10) and other
heptalenes derivable therefrom are in progress.
Received: July 22, 1974 [Z 81 b IE]
German version: Angew. Chem. 86. 778 (1974)
CAS Registry Numbers:
( 3 a ) , 52781-70-1; ( 4 ) , 493-04-9:
( 6 a ) , 52842-93-0: ( 6 h ) , 52882-38-9;
(81, 52781-73-4: (91, 52842-95-2,
( 5 ) . 52781-71-2;
(7),
( JO),
52781-72-3;
52781-74-5
[ I ] H . J . Dauben, J r . and D. J . Berrdli. J Amer. Chem. SOC. X3, 4657,
4659 ( 196 I).
[2] E. Vogel. H . Konigshofen. J . Wassm, K. Miillen, and J . F M . Orh,
Angew. Chem 86, 777 (1974):Angew. Chem. internat. Edit. 13, 732 (1974).
[3] E. Vogel. H . Kdnryshofrn, K . M u l l m , and J . F. M . 0 t h . Angew. Chem.
86, 229 (1974):Angew. Chem. internat. Edit. 13, 281 (1974).
[4] E. Rigel el a[.. to be published.
[ S ] M . Mpkoszu and M . Wanrzynies.rcz, Tetrahedron Lett. 1969,4659.
[6] The configuration of ( 6 0 ) follows from the assumption that the two
three-membered rings in the bisadduct of dibromocarbene to 4a,Sa-epoxy1,4,4a,5,8,Xa-hexahydronaphthaleneare rrans to the epoxide ring, ( 6 a ) can
be transformed cia ( 3 u ) into the epoxy compound.
[7] The bisadduct (66) gives ( 3 h ) as sole product on dehydration with
anhydrous formic acid.
[8] H. J . Dauben. Jr., L. R . Honnrn, and K. M . Harmon, J. Org. Chem.
25. 1442 (1960).
Dimethyl 3,8-Heptalenedicarboxylate
By Emanuel Vogel and Frank Hogrefe"]
The synthesis of 3,8-dibromoheptalene['] suggests that bisouter adducts of carbenes to isotetralin ( l ) , i.e. tetracycl0[5.5.0.0~.~.0~~
'Idodec-I (7)-enes, might be generally applicable as starting compounds for preparing heptalenes. While
use of dihalocarbenes as carbene components necessitates
blocking of the electron-rich central double bond of ( I ) ,
such a measure is not required on use ofthe alkoxycarbonylcarbenes which are more reactive and therefore preferentially
From these considerattack the outer double bonds of ( I ) [ ' .
ations results a relatively simple entry to dimethyl 3,8-heptalenedicarbox ylate.
The reaction of isotetralin ( I ) (0.75mol) with ethyl diazoacetate (2 mol) in the presence of copper powder ( 5 g), performed
by slow dropwise addition (96h) of the diazo compound to
the isotetralin/copper mixture at lOO"C, afforded a complex
product from which a fairly pure 2: 1 adduct crystallized
after 24 hours' standing; recrystallization from ethanol led
to a sterically uniform diethyl tetracycl0[5.5.0.0~~~.0~.~
']dodec-1(7)-ene-4,10-dicarboxylate having m. p. 196--197°C
(yield 18 %)I"]. The diethyl ester is readily transformed into
the dimethyl ester (2) [m.p. 171-172°C (from methanol);
yield 84 "/0] by alkaline hydrolysis and subsequent esterification of the crude acid with diazomethane. The stereochemistry
of (2) has not yet been elucidated with regard to the arrangement of the three-membered rings ;however, several analogous
c a s e ~ [ ~strongly
1
indicate both methoxycarbonyl groups to
be in the exo position.
Reaction of (2) with a 4.5-fold molar amount of N-bromosuccinimide (NBS) with addition of azobutyronitrile in boiling
carbon tetrachloride (reaction duration 45 min) furnishes a
bromination product consisting mainly of the tetrabromide
(3) (presumably a mixture of stereoisomers), yield ca. 55
Compound ( 3 ) ,which was not isolated pure, can be smoothly
dehalogenated to ( 4 ) by refluxing with activated zinc dust
in tetrahydrofuran. Work-up of ( 4 ) was by chromatography
on a short alumina column (dichloromethane) and recrystallization from n-hexane [m.p. 13&-132"C
(dec.); yield 60%;
UV (cyclohexane): A,,,=230 (~=36700),235 (38600), 296nm
(6100)l. After an initial unsuccessful attempt to dehydrogenate
( 4 ) to ( 5 ) cia the tropylium ion[','', reaction with 2Jdichloro-5,6-dicyano-p-benzoquinone
(DDQ) in benzene at 160°C
(ampoule; 15min)['' led to the desired result. The product
( 5 ) could be readily isolated by chromatography (silica gel;
dichloromethane) and precipitated as brownish red needles
on recrystallization from ether; m. p. 142-143 "C (yield 29%).
Remarkably, ( 5 ) is stable to air at room temperature.
The spectral properties of ( 5 ) largely resemble those of 3,8dibromoheptalene [60MHz 'H-NMR spectrum (CDCI,): AB
system at T = 3.30 and 4.82 with J = 10.5 Hz (vinylic protons),
singlet at ~ = 6 . 2 5(-COOCH, protons) (intensity ratio 4 : 3);
UV spectrum (cyclohexane) h,,,=262 (E= 248OO), 398 (9700),
547 nm (270, sh)].
'x.
Received: July 22, 1974 [Z 81c IE]
German version: Angew. Chem. 86, 779 (1974)
CAS Registry Numbers'
( I ), 493-04-9: (Z), 52781-66-5; 1 3 ) , 52920-68-0;
(41, 52781-67-6; (51, 52781-68-7;
diethyl tetracyclo[5.5.0.0 '.'.O'.'
69-8
'Idodec- I (7)-ene-4.I0-dicarboxylate,
5278 1-
[ I ] E. R)ge/ and J . Ippen, Angew. Chem. X6, 778 (1974): Angew. Chem.
internat. Edit. 13. 734 (1974).
121 Unpublished experiments in collaboration with H . Lepper: see also G .
L Thompsori, W E. Hryd, and L. A. Puyuerre, J. Amer. Chem SOC. 96,
3177 (1974).
[3] W K i r m s e ' Carbene Chemistry. 2nd Edit. Academic Press, New York
1971,p. 288.
141 The steric homogeneity and high symmetry or the adduct
primarily by its extremely simple "C-NMR spectrum.
is
indicated
[S] See, e.g., H . Musso and 0. Bic,rhan. Chem. Ber. Y7, 2282 (1964).
t . N,CHCO,C?H,
2 KOH
Br B r
(41
(5)
[6] H. J Dauben, J r . and D. J . Brrrrlli. J. Amer. Chem. SOC. 83, 4657
I'[
Prof. Dr. E. Vogel and F. Hogrefe
lnstitut fur Organische Chemie der Universitat
5 Koln I . Ziilpicher Strasse 47 (Germany)
Angew. Chem. inrernat. Edit.
Vol. 13 (1974) 1 No. / I
( I96 I).
[7] E. Voyid, H . Koniyshofen, K . Miillen, and J . F . M. Orh, Angew. Chem.
86, 229 (1974);Angew. Chem. internat Edit. I3, 281 (1974)
735
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dimethyl, heptalenedicarboxylate
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