close

Вход

Забыли?

вход по аккаунту

?

Conformations of trans-1 2-Dicyclopropylethylene and Vinylcyclopropane.

код для вставкиСкачать
The excess of ?lkylaluminum compound may be replaced by
anhydrous AICl3. A solution of the anhydride and A1CI3 in
methylene chloride is allowed to react with the alkylaluminum
compound, e.g. trialkylaluminum.
Maleic anhydride (as a suspension in methylene chloride)
gives the corresponding a,$unsaturated y-keto acids, e.g.
with (C2H&A12C13 (mole ratio 1 : 1) at -10°C it gives 40x0-2-hexenoic acid in 47 % yield.
Lactones are by-products in all the reactions of cyclic anhydrides. Diketones and dicarboxylic acids are formed in
addition to keto acids from acyclic anhydrides because of the
statistical attack on the CO-0-CO group.
+
Anhydride
alkylating agent
Succinic anhydride i(CzHdiA12Ch
AICh (CzHdiAI
CsH1iAlCl2
AlCli CsHi7AICIz
AICIi CizHz5AIC12
+
+
+
Molar
ratio
Keto acid
1:l
4-Oxohexanoic
4-Oxohexanoic
4-Oxodecanoic
4-Oxododecanoic
4-Oxohexadecanoic
60
69
49
56
38
5-Oxoheptanoic
44
4-0x0-2-hexenoic
4-0x0-2-dodecenoic
47
10-Oxododecanoic
42
o-Propionylbenzoic
95
1 : 1 :0.4
1:1.7
1:1:1
1: 1 :1.3
Decanedioic anhydride
(CzH5)sAhC13
17
+
]:I2
+
Phthalic anhydride
AICIi ( C Z H ~ ) ~ A I ~ C I I 1 : 1 :0.5
+
Yield
[%I
Vinylcyclopropane itself is not a suitable case for study of
this problem by vibration spectroscopy since the conceivable
conformers of this molecule (s-trans, s-cis, and gauche forms)
do not differ sufficiently in symmetry and thus in the relevant
selection rules (point groups: C,, C,, and C1, respectively).
We have therefore measured the infrared spectrum of trans1,2-dicyclopropylethylene(2) in the liquid and in the crystalline state; this compound may be considered to represent a
vinylcyclopropane system with a potential symmetry center.
The most important result was the appearance of a C = C
stretching vibration band at 1660 cm-1 and two intense bands
at 952 and 960 cm-1 (C-H out-of-plane deformation of trans1,2-substitutrd ethylenes 121) in the spectrum of the liquid,
whereas the bands at 1660 and 952 cm-1 d o not occur in the
spectrum of the crystals.
According both to experimental findings [31 and theoretical
calculations 141 cyclopropanecarbaldehyde has a two-fold torsional potential, with minima at 'p = 0 " and cp = 180' (cp =
torsion angle). It is thus to be assumed that only the s-transand the s-cis-conformation (cp = 180 and 0 O , respectively) of
the isoelectronic vinylcyclopropane are stable, because only
in these is the additional nonbonded interaction between
hydrogen atoms minimal [51. This fundamental difference
from bicyclopropyl [ I ] follows from the differing geometry of
the molecule.
On such considerations crystalline trans-1,2-dicyclopropylethylene consists exclusively of one of the two centrosymmetric conformers, s-trans-s-trans (2a) or s-cis-s-cis- (Zc),
whereas the s-cis-s-trans-conformer (26) also occurs in the
equilibrium mixture in the liquid state.
8
a) Saturated keto acids: 89 g (0.36 mole) of ( C ~ H S ) ~ A Iis~ C I ~
dropped, with stirring, into a solution of 35.6 g (0.36 mole)
of succinic anhydride in 250ml of CH2C12 at 20°C. The
mixture is boiled for 2 hours and then hydrolysed with 15 %
HzS04. Fractional distillation of the organic phase gives 28 g
(60 %) of pure 4-oxohexanoic acid, b.p. 98-100 "Cj0.l mm,
m.p. 34-36 "C.
We have been able to prove, by N M R spectroscopy, that the
b) Unsaturated keto acids: Reactions with maleic anhydride
s-trans-conformation of vinylcyclopropane is energetically
are carried out at - 10 "C (suspension in CHzCI2); hydrolysis
more favored than the s-cis-conformation. For this purpose
is effected at -10 to -15 "C. 32.7 g (0.33 mole) of maleic anwe measured the temperature-dependence of the vicinal H,H
hydride and 83 g (0.33 mole) of ( C ~ H ~ ) ~ A I afford
Z C I ~ 20 g
coupling constant Jab in hexadeuteriovinylcyclopropane(3).
(47 %) of 4-0x0-2-hexenoic acid, m.p. 110 "C, on evaporation
of the solvent and recrystallization of the residue from light
D
petroleum.
Received: February 9th, 1966
[Z l58/990 IEI
German version: Angew. Chem. 78, 491 (1966)
[l] Communication VII on Reactions with Aluminum Alkyls. Communication VI: H . Reinheckel and D. Jahnke, Chem. Ber.,
in press.
[2] For a summary see M . S . Kharasch and 0. Reinmuth:
Grignard Reactions of Non-metallic Substances, Prentice-Hall.
New York 1954.
Conformations of trans-l,2-DicycIopropylethylene
and Vinylcyclopropane
By Prof. Dr. W. Liittke and Dip1.-Chem. A. de Meijere
Organisch-Chemisches Institut
der Universitat Gottingen (Germany)
In the course of our systematic studies[" of the rotational
isomerism of 1,3-butadiene and the lower bicycloalkyls ( I )
we were interested in the conformational behavior of vinylcyclopropane, which is intermediate between 1,3-butadiene
[ ( I ) , n = 11 and bicyclopropyl [ ( I ) , n = 21.
n
n
(H&&CH-CUCHdn
512
Interconversion of the s-trans- (3.) and the s-cis-form (36)
is very fast in the temperature range studied. Thus a mean
coupling constant (see table, second column) is observed, the
following equation being valid (xtrans and xcis = mole
fractions of the s-trans- and the s-cis-form, respectively) :
Jfi6ans
IS
'
certainly larger than J2:[61. I t therefore follows
from the fact that J$ increases with decreasing temperature
that the concentration of the trans-conformer increases. The
s-trans-conformation is thus energy-poorer.
I .obs
-30
-10
( I ) . n = 1, 2.. . 5
+ 60
9.13
9.05
I
I
0.69
0.68
0.31
0.32
- t 80
Angew. Chem. internat. Edit.
1 Vol. 5 (1966) / No. 5
If we assume that Jt,6ans lies between 11 and 12 cps [71 and
Jf; between 4.5 and 6 cps[81, we can obtain the equilibrium
concentrations xtranS and xcis from Equation (a). (In the
table, columns 3 and 4 give the values of Xtrans and Xcis that
= 11.0 cps and .
l
:
: = 5.0 cps.
result from the values ?:J
522+ 60
120% 10
(24
(2b)
(2c)
2 0 0 i 20
(2d)
11.6-1-1
-0.57
-0.30
0.01
-0.50
Fromthe temperature-dependence of theequilibrium constants
K = xtrandxcis
the energy difference between the trans- and the cis-conformer
has been estimated graphically to be 1.1 & 0.2 kcal/mole.
Received: February 10th. 1966
[Z 171/3 IE]
German version: Angew. Chem. 78, 544 (1966)
[I] W. Liittke, A. de Meoere, H. Wolff, H. Ludwig, and H . W .
Schrotter, Angew. Chem. 78, 141 (1966); Angew. Chem. internat.
Edit. 5, 123 (1966).
[2] L . J. Bellamy: The IR-Spectra of Complex Molecules. Methuen, London 1960, p. 45.
[3] L . S . Bartell and J . P. Guillory, J. chem. Physics 43, 647
(1965).
[4] R . Hoflmann, Tetrahedron Letters 1965, 3819.
[5] In a recent publication [Angew. Chem. 78, 266 (1966); Angew. Chem. internat. Edit. 5,251 (1966)] H. Giinther and D . Wendisch support the view that for vinylcyclopropane derivatives a
trans (cp = 180 ") and two gauche forms (cp = 40 ") are the stable
conformers. - Consideration of a molecular model of cyclopropane, like calculation of the sum of all the H...H interactions
as a function of the torsion angle 9 [potential according to L . S.
Bartell, J. chem. Physics, 32, 827 (1960)], shows a narrow minimum at the cis-position ((p = 0 ") and a broad minimum region
for the trans-position (cp = 180 & 100 "). The two maxima of the
torsional potential curve lie at cp = 40 and 320 '.
[6] H . Suhr: Anwendungen der kernmagnetischen Resonanz in
der organischen Chemie. Springer, Berlin 1965, p. 53.
171 A. A. Bothner-By, C . Naar-Colin, and H. Giinther, J. Amer.
chem. SOC.84, 2748 (1962).
[S] J. B. Lambert, L . J . Durham, P . Lepoutere, and J . D. Roberts,
J. Amer. chem. S O C . 87, 3896 (1965).
Proton Activity in the 1,2-Dithiolium System
By Prof. Dr. H. Prinzbach, Dr. E. Futterer,
and Prof. Dr. A. Luttringhaus
Chemisches Laboratorium der Universitat Freiburg
(Germany)
As with analogous 1,3-dihetero cations, the acidity of the H
atom at position 2 of 1,3-dithiolium salts ( I ) is considerable [I]. In concordance with the results of quantum-mechanical studies [21 and with the weak electronic shielding shown
by low .c-values [31, the H atoms at positions 3 and 5 of the
1,2-dithiolium system (2), Rl=RZ=H (the C atoms to which
they are attached have only one S atom as neighbor) undergo
readily measurable H / D exchange even in 10% (v/v)
F3CCOOD/DzO (74 2 "C; 0.5 mole, 1). By NMR-spectroscopic measurements we have determined the effective exchange half-lives t1/2 listed in the Table.
In contrast to 1,3-dithiolium salts (I), the 1,2-dithiolium
salts (in acetonitrile) d o not give the dimers (5) when treated
with N-ethyldiisopropylamine,but instead give the dithiole3-thione (6) (yield cn. 50 %). In view of the easy scission of the
disulfide linkage by carbenes [41, attack of the carbene (3) on
the disulfide bridge in (2) or (3) is not excluded. The yields of
(6) can be increased substantially (up to 97 %) by addition
of elemental sulfur 151.
Received: February 14th, 1966
[Z 163/995 IEI
German version: Angew. Chem. 78, 492 (1966)
[I] H . Prinzbach, H. Berger, and A . Liittringhaus, Angew. Chem.
77, 453 (1965); Angew. Chem. internat. Edit. 4, 435 (1965).
[2] R . Zahradnik and J . Koutecky, COIL czechoslov. chem. Commun. 28, 1117 (1963); G . Bergson, Arkiv Kemi 19, 181 (1962).
[3] H. Prinzbach and E. Futterer, Adv. heterocyclic Chem. 7,
in press (1966).
[4] A. Schonberg, 0. Schiitz, and J . Peter, Ber. dtsch. chem. Ges.
62, 440 (1929); J . H . Hartenstein, Diploma Thesis, Universitat
Freiburg, 1961; U.Schmidtand Ch. Osterroht, Angew. Chem. 77,
455 (1965); Angew. Chem. internat. Edit. 4, 437 (1965).
[5] E. Klingsberg, J. org. Chemistry 28, 529 (1963).
Preparation and Rearrangement of Allylalanes
By Dr. H. Hoberg
Max-Planck-Institut fur Kohlenforschung,
Mulheim/Ruhr (Germany)
Diazomethane reacts with organic derivatives of aluminum
hydrides in toluene at -78 "C, giving, by way of Al ylides (I),
products (2) in which a residue attached to the A1 atom has
been lengthened by a CH2 g r o u p W The CH2 group is
X = Halogen, H, or organic group
R = C2Hs
inserted preferentially between Al and the most electronegative ligand. Thus alkenyldialkylalanes (3) (prepared
from triethylalane and acetylene 121) reacts with equimolar
amounts of diazomethane in toluene/anisole (4 :1 v/v) at
-78 OC predominantly at the Al-C(alk,n,gbond, for hydrolysis of the product gives pentene as well as ethane. However,
)A~-CH=CH-C H ~ - C ~ H ~
CZH5
(5)
Angew. Chem. internat. Edit.
Vol. 5 (1966) / No. 5
513
Документ
Категория
Без категории
Просмотров
0
Размер файла
215 Кб
Теги
conformational, dicyclopropylethylene, transp, vinylcyclopropanes
1/--страниц
Пожаловаться на содержимое документа