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Isomers of Perhydro-9b-boraphenalene.

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Table 2. Reaction rate constants (at 130 “C in dioxan) and Arrhenius
parameters in t he Diels-Alder addition of maleic anhydride to
anthracene derivatives
Anthracene
derivative
I. 9,IO-Dimethyl-
2.
3.
4.
5.
6.
7.
8.
9.
9,lO-Diethyl9-Methyl9-Ethyl9-MethoxyAnthracene
9-Chloro9,10-Dimethoxy
9-Bromo10. 9-Phenyl11. 9,lO-Dichloro12. 9-Nitro13. 9-Cyano14. 2-Dimethylamino15. 2-Methyl-
105x kz
(liters/molex sec)
EA
(kcal/mole)
log A
141000
24 200
11200
4420
1630
646
192
191
152
49.0
ca. 28
5.89
ca. 4.2
10.9
11.9
13.3
13.1
14.8
16.3
16.8
14.8
6.04
5.84
6.24
5.76
6.25
6.67
6.4 I
5.29
16.7
5.74
18.8
5.99
-
-
14.9
15.6
6.32
6.26
1680
664
-
-
-
-
additions involving maleic anhydride (Table 2, Nos. 14, 15).3. Differences in reactivity of the dienes are primarily caused
by changes in EA ; the extremely low log A value is remarkably
constant. In combination with the rate phenomena observed
with cis-trans isomeric dienophiles [3] and the low solvent
effect, we consider our results as an additional argument in
favor of a concerted mechanism for the Diels-Alder addition.
Received, March 27th. 1962
[Z 253/85 IE]
[l] See also D. Craig, J. J. Shipman, and R . B. Fowler, J. Amer.
chem. SOC.83,2885 (1961).
121L . J. Andrews and R. M . Keefer, I.Amer. chem. SOC.77,6284
(1955).
[3] J. Sauer, H . Wiest, and A . Mielert, Z . Naturforsch., in the
press; J. Sauer, D. Lang, and H. Wiest, ibid., in the press.
ponent and the dienophile as the component with excess
electrons.
From the data in Table 1 the following conclusions are
obtained :
1. Simple olefins (Nos. 7, 6, 3) surpass maleic anhydride in
their rate of addition to hexachloropentadiene; however,
maleic anhydride adds to 9,lO-dimethylanthracene about
200,000 times faster than cyclopentene. While tetracyanoethylene, the most active dienophile, reacts with the anthracene derivative almost immeasurably fast - even at
20°C [2] - it has not yet been possible to add it to hexachlorocyclopentadiene. - 2. Conjugation of the olefinic
double bond with electron donating ligands (Nos. 7, 5, 1 and
3, 2) promotes the addition to hexachlorocyclopentadiene,
but retards the addition to 9,lO-dimethylanthracene (Nos.
3, 2). - 3. The low degree of dependence of the rate of
addition [3] on substituents, also observed in other diene
additions, the extremely low log A values, and the significant
influence of steric factors (Nos, 3, 9, 11) suggest that diene
additions with “inverse” electron demand also proceed by
a concerted mechanism.
A search for further examples of diene additions with “inverse” electron demand involving other electron deficient
dienes and electron rich dienophiles is being conducted at
present.
Received, March 27th. 1962
[Z 2-54/87 IE]
111 Cf. R. Riemschneider and B. E. Grabitz, Mh. Chemie 91, 22
(1960).
121 Unpublished experiments in collaboration with R. Wiemer,
Munich.
131 E g . , E. J. De Witt, C. T. Lester, and G. A. Ropp, J. Amer.
chem. SOC.78, 2101 (1956); I. Benghiat and E. I. Becker, J. org.
Chem. 23, 885 (1958).
Isomers of Perhydro-9b-boraphenalene
Diels-Alder Additions with “Inverse” Electron
Demand
By DipLChem. G. Rotermund and Dr. R. Koster
Max-Planck-Institut fur Kohlenforschung,
Mulheim/Ruhr (Germany)
By Dr. J. Sauer and H. Wiest
Institut fur Organische Chemie der Universitat Miinrben
The rate of reaction of normal Diels-Alder additions is
increased by electron attracting ligands in the dienophile and
decreased by electron donating ligands. In the formal sense
the dienophile reacts as the electron deficient component, the
diene as the electron rich component.
The data in Table 1 show for the first time the existence of
Diels-Alder additions with “inverse” electron demand and
simultaneouslyeliminate uncertainties existing in the literature
[I]. In these cases, the diene acts as the electron deficient comTable 1. Rate constants and Arrhenius parameters for Diels-Alder
additions of hexachlorocyclopentadiene and 9.10-dimethylanthracene
at 130 “C in dioxan
Hexachlorocyclopentadiene
Dienophile
106xk2
[literslrnolex sec]
1. Cyclopentadiene
2.
3.
4.
5.
6.
7.
8.
9.
10.
p-Methoxystyrene
Styrene
p-Nitrostyrene
2,3-Dihydrofuran
Norbornene
Cyclopentene
Maleic anhydride
a-Metbylstyrene
Cyclohexene
11. &Methylstyrene
..
.
..........
....
.
......
.....
.
..
.....
..
15200
1580
750
538
333
70.8
59.0
29.1
8.2
3.0
ca. 2.8
log A
14.0
5.77
-
-
15.2
5.14
-
-
-
16.2
19.1
4.54
5.80
-
-
-
Angew. Chem. internat. Edit. / Vol. I (1962)I Nr. 5
Compound (I) is obtained either by hydroboration of all-transcyclododeca-l,5,9-trienewith N-triethylamineborane [l] or
ethyldiborane [2] or by pyrolysis of tricyclododecylboran [3].
Compound (11) is formed quantitatively on thermal isomerization of I in the presence of trialkylamines (e.g. triethylamine) and hydrogen, using pressure and temperatures above
200 “C (hydrogenation/dehydrogenation equilibria). Small
amounts of I1 are also formed on pyrolysis of polymeric byproducts formed during hydroboration of cyclododecatrienes
(dehydroboration/hydroborationequilibria).
9,lO-Dimethylanthracene
EA
[kcal/mole]
-
We have prepared three pure isomers of perhydro-9bboraphenalene [l], of formula C12H21B. The compounds can
be separated by distillation and differ in their physical (see
table) and also in some of their chemical properties.
106 x k2
[literslmolex secl
EA
[kcal/mole]
50.0
70.1
602
-
36.2
7.80
1410000
-
269
’-
all-cis-perhydro-9
cis,cis,frans-perhydro1 3-boratricyclo[6,4,
boraphenalene (centro- 9 b-boraphenalene(centro- 1,W13ltridecane
boron I)
boron II)
les) can be C-acylated with N-acylimidazoles(I mole) in benzene or benzeneltetrahydrofuran. Good yields are obtained
at room temperature. The second mole of alkylene (I) serves
as a proton acceptor [I] in the “transylidation” (2),and forms
the corresponding phosphonium bromide if the reaction
is carried out, as is usual, in the presence of LiBr (imidazolelithium is formed at the same time; this can be shown by
reaction with ethyl bromide leading to N-ethylimidazole).
(centroboron 111)
Compounds (I) and (11) have characteristically different
infrared spectra and undergo auto-oxidation. However,
(11) is more stable toward various reagents than (I). Thus,
(II), remains virtually unattacked by ethylene at 150-200 “C
(displacement reaction) [4] and is attacked only slowly by
hydrogen under pressure (hydrogenation of the B-C bonds)
[5],whereas I reacts in essentially the same manner as trialkylboranes BR3.
About 30-40 % (111) is formed along side (I) from trans,
trans,cis-cyclododeca-1,5,9-triene and triethylamineborane
[1,6].At about 2OO0C, 111 isomerizes in to (I). On partial
acetolysis [7]and subsequent oxidation with alkaline H202,
three cyclododecanediols are obtained from (111) ; these were
separated as their diacetates by gas chromatography.
Example: or-Benzoylmethylene-triphenylphosphine(11, R = H: R =
GH5): N-Benzoylimidazole (0.52 9.; 3 mmoles) dissolved in benzene
(50 ml.) is added dropwise, and at room temperature, to a solution of (I)
prepared from triphenylphosphoniumbromide (2.14 8.; 6 mmoles) in
benzene (150 ml.) and 6 mmoles standardized (ca. 1 N) phenyllithium
inether. The usual working-up procedure gives (11) in 99 % yield
(1.13 g.), m.p. 181-185°C (Lit.: 181 C); after recrystallization from
acetone m.p. 186-187 “C.
Received, March 30th. 1962
three isomers
[Z 247/70 IE]
[l]See H. J. Bestmann, Chem. Ber. 95,58 (1962).
We suspect that 111 is the all-cis form of the four possible
cis-trans isomers.
cc-Forrnylalkylenetriphenylphosphinesand
a-Imidazolylcarbonylalbylenetriphenyl
phosphhes
Table I . C12H218 Isomers
Centroboron
comoound
I
11
111
[ b.p. 1OC/mm.Hgl
1 I
I
115/10
113.5/10
113/10
-
+ 31
-
By Prof. Dr. H. A. Staab and DipLChem. N. Sommer
I
0.93771
0.9220
0.92196
1.5100
1.5027
1.5058
[I]R. KSster, Angew. Chem. 69,684 (1957).
[2]R. Koster and G. Griaznov, Angew. Chem. 73, 171 (1961).
[3] R. Koster and G. Rotermund, Angew. Chem. internat. Edit.
2, 217 (1962).
[4]R. KSster, Liebigs Ann. Chem. 628,31 (1958).
[5]R. KSster, G. Bruno, and P. Binger, Liebigs Ann. Chem. 644,
1 (1961).
[6]N. N. Greenwood and J. H. Morris (J. chem. SOC.(London)
1960,2922; Proc. chem. SOC.(London) 1960,25) therefore did
not have a pure centroboron compound for their investigations;
cf. Angew. Chem. 72, 328,792 (1960).
[7]P . Heimbach, Ph. D. Thesis, Technische Hochschule, Aachen
1960.
C-Acylation of Alkylenephosphines
By Dr. H. J. Bestmann
Organisch-chemisches Institut der Technischen Hochschule
Miinchen (Germany)
Dip1.-Chem. N. Sommer and Prof. Dr. H. A. Staab,
Organisch-chemisches Institut der Universitat Heidelberg
(Germany)
Independent studies in Munich and Heidelberg have shown
that alkylenetriphenylphosphines (I; R = H or alkyl; 2 mo-
270
Organisch-chemischesInstitut der Universitat Heidelberg
(Germany)
Analogously to the C - acylation of alkylenephosphines
described above [I], the a-formyl derivatives (I) can be
prepared by use of N-formylimidazole [2], e.g. a-formylmethylene triphenylphosphine(1; R = H) is obtained in 81 %
yield. The a-formyl derivatives yield a,@-unsaturated aldehydes [3]in thewitti$ reaction and thealdehydesR-CH2-CHO
are formed on hydrolysis.
a - Imidazolylcarbonylalkylenetriphenylphosphines (11;
R = H, m.p. 184-186’C, 81% yield; R = CH3; m.p.
172-175 “C, 60 % yield) result from reaction with N,N‘carbonyldiimidazole at room temperature 141.When the imidazolyl compounds (11) are hydrolysed, the corresponding
carboxylic acids R-CH2-COOH are obtained in good yields.
Despite more vigorous reaction conditions, the Wittig reaction with compounds 01) leads to a,@-unsaturatedcarboxylic
acids (via a,@-unsaturated imidazolides only in moderate
yields.
Received, March 30th. 1962
[Z 248/71 IE]
[ 11 H. J. Bestmann, N . Sommer, and H . A . Staab, Angew. Chem.
internat. Edit. 1, 270 (1962).
[2]H.A . Staab and B. Polenski, Liebigs Ann. Chem., in the press.
[3] See S.Trippett and M . Walker, J. chem. SOC.(London) 1266
(1961).
[4]H . A . Staab, Liebigs Ann. Chem. 609,75 (1957).
Angew. Chem. internat. Edit.
Vol. I (1962) f No.5
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