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Methylenecyclopropane from Methallyl Chloride.

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ethanol/H2O. and T H F , a n d moderately t o only slightly in
acetone, acetonitrile, dioxane, CS2, a n d halogenated hydrocarbons.
Received: December 19, 1968
[Z 928b IE]
German version: Angew. Chem 81, 183 (1968)
(3)
[ * ] Dr. J . Ellermann[**] and Dipl.-Chem. F. Poersch
Institut fur Anorganische Chemie der Universitlt
Erlangen-Nurnberg
852 Erlangen, Fahrstr. 17 (Germany)
Dr. R. Kunstmann
Institut fur Organische Chemie der Universitat
Erlangen-Nurnberg
852 Erlangen, Henkestr. 42 (Germany)
Dr. R. Kramolowsky
Institut fur Anorganische Chemie der Universitat
2 Hamburg 13, Papendamm 6 (Germany)
[**I Author to whom correspondence should be addressed.
[l J Part 22 of Spiroheterocyclic and Heterobicyclic Compounds;
part was included in lectures by J . Ellerrnorm on November 22,
1968 in Erlangen and on December 2 1968 at Gottingen. Part 21 : J . Ellermann and D . Scliirmacher, Chem. Ber. 102, 297
(1969).
121 J . Ellermann and F. Poersch, Angew. Chem. 79, 380 (1967);
Angew. Chem. internat. Edit. 6, 355 (1967).
131 R . Kramolowsky, Angew. Chem. 81, 182 (1969); Angew.
Chem. internat. Edit. 8,202 (1969); R . Krumolowsky, unpublished
work.
141 J . Ellermann and D . Schirmacher, Chem. Ber. 100, 2220
(1967); Angew. Chem. 80, 755 (1968); Angew. Chem. internat.
Edit. 7, 738 (1968).
[ 5 ] J. Ellermann and K . Dorn, Chem. Ber. 101, 643 (1968).
[6] J . Ellermann and W . H . Gruber, Chem. Ber. 101, 3234 (1968);
102, 1 (1969); where further references are given.
171 H . Siebert: Anwendungen der Schwingungsspektroskopie in
der anorganischen Chemie, Springer-Verlag, Berlin-HeidelbergNew York 1966.
181 J . Chart, Science (Washington) 160, 723 (1968).
trans-2-Methylcyclopropanol from
1-Methylcyclopropene
H o d
(4a)
of ( 3 ) : 7 = 6.70 (M), 9.09 (D, J = 2.5 Hz), 9.33 (M), 9.79
p p m (M) in t h e intensity ratio 1:3:2.1.
In a reaction analogous t o (b), tricyclopropylborane 141 can
also b e oxidized lo tricyclopropyloxyborane. Owing t o t h e
sensitivity of cyclopropanols 151, n o useful results a r e obtained
o n treatment with aqueous hydrogen peroxide.
Transesterification of ( 3 ) with methanol leads t o a 75 % yield
of sterically uniform trans-2-methylcyclopropanol ( 4 7 ) .
which contains a t most ca. 5 % o f I-methylcyclopropanoI
(4bi a s a reaction product of (26). T h e structure of (4a) follows f r o m cis-hydroboration [21 and from the agreement of its
I H - N M R spectrum with a computer-simulated spectrum
(LAOCOON I) 161. ' H - N M R spectrum of (40) (undiluted):
:=4.50(S),6.96(M),9.0(D,J= 2 . 5 H z ) , 9 . 1 5 ( M ) , a n d 9 . 7 6
p p m (M) in the intensity ratio 1:1:3:2:1.
Tris(trans-2-1nethylcyc1opropyloxy)borane( 3 )
Compound (2) (4.8 g, 27.2 mmole) [prepared from ( I ) a n d
diborane in pentane] is diluted with anhydrous toluene (50
ml), a n d anhydrous trimethylamine N-oxide (6.25 g, 83.5
mmole) is added portion-wise t o the solution a t 8OOC. On
boiling for 30 min, 4.8 g (99:/,) of N(CH3)3 is evolved. T h e
excess of N-oxide is filtered off a n d t h e filtrate distilled under
vacuum t o yield compound ( 3 ) (4.2 g, 70%) having b.p.
74-75 OC'2 torr, n: = 1.4288.
trans-2-Methylcyclopropanol (4a)
By R . Koster, S . Arora, a n d P. BingerI*]
Reaction of 1-methylcyclopropene [ I ] ( l ) and diborane in
pentane according t o (a) proceeds via cis BH addition 121 t o
give a yield of more t h a n 80 % of tris(trans-2-methylcyclopropy1)borane (Za) [b.p. 37-40 "C!O.OOl torr, molecular
weight (mass spectrometric) 176 (B1)J containing only a few
(% 7 %) I-methylcyclopropyl groups a s (26) (gas chromatography). With tetraethyldiborane, compound ( l ) forms almost
pure diethyl(rrans-2-methylcyc1opropyl)borane.
In diethyl ether t h e formation of polymeric organoboranes
of unknown structure causes t h e yield o f (2) [**I formed in
(a) t o fall t o 65-70%. 1 H - N M R spectrum of (2) (undiluted):
T = 9.0 (D, J < 2 Hz), 9.2 (M), 9.6 (M), 10.9 p p m (M) in t h e
intensity ratio 3:2:1:1.
C o m p o u n d (2) reacts with trimethylamine N-oxide 131 in
boiling toluene according t o (b) giving tris(trons-2-methylcyclopropyloxy)borane ( 3 ) in 70 % yield. I H - N M R spectrum
Ang-ew. Chem. internat. Edit. J Vol. 8 (1969)
3
/ No. 3
Removal of the azeotropic mixture (CH,O)3B/HOCH,
(b.p. 54°C) and of methanol from a solution o f ( 3 ) (4.8 g,
21.4 mmole) in absolute methanol (30 ml) by distillation
over a 25-cm packed column (ca. 3 theoretical plates) affords
the compound (47) [4 g, b.p. 34-36 OCj12 torr, molecular
weight (mass spectrometric) 721; gas chromatogram: 87.5 %
of ( 4 a ) , 5.7 % of methylcyclopropanol(4b), 1 %ofisobutanol,
0.1 % o f butyraldehyde, 4.6% o f CH3OH.
Received: January 2, 1969
[Z 929a IE]
German version: Angew. Chem. 81, 185 (1969)
[*I Dr. R. Koster, S . Arora, and Dr. P. Binger
Max-Planck-Institut fur Kohlenforschung
433 Mulheim/Ruhr, Kaiser-Wilhelm-Platz 1 (Germany)
[ l ] F. Fisher and D. E. Applequist, J. org. Chemistry 30, 2089
(1965).
[2] Cf. H. C. Brown: Hydroboration. W. A. Benjamin, New
York 1962, p. 14.
[**J Compound (2) in the text refers to the mixture of (2a) and
(26) obtained according to equation (a).
[3] R. Koster and Y . Morita, Liebigs Ann. Chem. 704,70 (1967).
[4] P. Binger and R . Koster, Angew. Chem. 74, 652 (1962);
Angew. Chem. internat. Edit. I , 508 (1962).
IS] C . H . D e Puy, Accounts chem. Res. I , 33 (1968).
161 E. G. Hofinann and G. Schroth, personal communication.
Methylenecyclopropane from Methallyl Chloride
By R . Koster. S . Arora, a n d P . Binger[*l
In continuation of previous experiments o n cyclopropylborane"] we have carried o u t the hydroboration[2] of 1methylcyclopropene ( I ) . C o m p o u n d ( I ) is now readily ac-
205
cessible by treatment of methallyl chloride with sodium
amide in boiling tetrahydrofuran 131. Surprisingly, however,
reaction with potassium amide under otherwise identical
conditions proceeds via route (a) to give a 36% yield of
methylenecyclopropaiie I Z ) , as the only C4Hh hydrocarbon,
instead of ( l ) .
'"b +
t NaNII,
NH3
+
NaCl
NH3
+
KC1
/
CH2-3
+
(a)
2)
After removal of oligomers, e.g. C8H12 and C12H18, compound (2) is obtained in 97 % purity (IR [41, 1H-NMR 151, and
mass spectral5J). Thus the preparation of (2) by equation (a)
is superior to all previously known methods 14-61. Compound
(2) is also formed quantitatively when ( I ) is passed through
a suspension of KNHz in boiling THF, so that ( I ) cannot be
ruled o u t as an intermediate in reaction (a).
Compound (2) and tetraethyldiborane react together according to equation (b) at -10 to 0 "C to give diethyl(cyc1opropylmethy1)borane (3), which rapidly isomerizes at room
temperature to diethyl-3-butenylborane ( 4 ) [IR spectrum:
1637 (vc=c). 990 (-{=cH). 910 cm-1 (Y-CHJ] in a manner
analogous to cyclopropylmethyllithium171 and cyclopropylmethyimagnesium 181. However, in the presence of pyridine
the cyclopropylmethyl group of ( 3 ) remains intact.
Reaction of (2) with diborane at room temperature proceeds
according to equation (b), yielding mainly tris(3-butenyl).
borane (51, since the cyclopropylmethyl groups of tris(cycl0propy1methyl)borane rearrange rapidly at temperatures
above 0°C. IH-NMR spectrum of ( 5 ) (undiluted): r = 4.16
(M), 5.11 (M), 5.16 (M), 7.79 (M), 8.66 ppm (T, J = 8 Hz) in
the intensity ratio 1 :1:1:2:2.
Compound ( 5 ) is not completely homogeneous since hydroboration of (2) also gives rise to isomeric C4H7 groups
(< lo%), presumably by inverse BH addition, which can be
detected in the IH-NMR spectrum as l-methyl-l-cyclo= 8.62 (S), 9.35 (M), and 9.59 ppm (M)
propyloxy groups
in the intensity ratio 3:2:2] after oxidation of ( 5 ) by trimethylamine N-oxide.
Methylenecyclopropane (2) 191
Methallyl chloride (101 g, 1.12 mole) is added dropwise over
a period of 1 h to KNHz (64.8 g. 1.17 mole) in boiling anhydrous tetrahydrofuran (250 ml). Compound (2) and NH3
are evolved and are carried by a stream of argon through
5 N H2S04 (250 ml, weight increase = 14.4 g (76%) of ammonia) into a cold trap (-80°C). A single recondensation
affords 21.7 g (36%) of product; gas chromatogram: 97% of
(2) and 3 % of isobutene.
Received: January 2. 1969
[ Z 929b 1El
German version: Angew. Chem 01, 186 (1969)
206
['I Dr. R. Koster, S. Arora, and
Dr. P. Binger
Max-Planck-Institut fur Kohlenforschung
433 Miilheim/Ruhr, Kaiser-Wilhelm-Platz 1 (Germany)
[l] P. Binger and R. Kiister, Angew. Chem. 74, 642 (1962);
Angew. Chem. internat. Edit. I , 508 (1962).
[21 R. Koster, S. Arora, and P. Binger, Angew. Chem. 81, 185
(1969); Angew. Chem. internat. Edit. 8, 205 (1969).
[31 F. Fisher and D. E . Applequist, J. org. Chemistry 30, 2089
(1965).
[41 J. T . Gragson, K . W . Greenlee, J. M . Derfer, and C. E. Boord,
J. Amer. chem. SOC.75, 3344 (1953).
[5] B. L. Anderson, J. org. Chemistry 27, 2720 (1962).
161 A. T . Bloomquist and D. J. Connolly, Chem. and End. 1962,
310.
[7I P. T. Lansburg and V. A. Pattison, J . Amer. chem. SOC.85,
1886 (1963); P. T . Lansburg, V. A. Pattison, W . A . Clement, and
J . D. Sidler, ibid. 86, 2247 (1964).
[81 J. D. Roberts and R. H . Mazur, J. Amer. chem. SOC.73,2509
(1951); D . J. Patel, C. L . Hamilton, and J . D. Roberts, ibid. 87,
5144 (1965).
[91 Note added in proof(February 7,1969): In the meantime we
have achieved a yield of up to 65% of C4H6 hydrocarbons (gas
chromatogram: 38"/, of ( I ) , 62"h of ( 2 ) ) with NaNHz in boiling
dioxane.
Preparation and Properties of 1,2-Diethylidenecyclobutane
By P . Heimbach and R. s c h i i n p f ~ * ~
The readily accessible cis-1,2-divinylcyclobutane ( I )111,
which is formed catalytically in 40% yield from butadiene,
undergoes ready isomerization on treatment with potassium
tert-butoxide in dimethyl sulfoxide 121 at 40-60 'C to give
(2a) and (2bi - two of the three conceivable isomers of 1.2diethylidenecyclobutane - as well as 1-ethyl-2-vinylcyclobutene ( 3 ) . trans-l,2-Divinyicyclobutanecan also be isomerized to (2a), (Zb), and ( 3 ) . Compounds (2a) and (26)
were not separated by distillation.
In a competing reaction, ( 1 ) rearranges to cis,cis-l,5-cyclooctadieneW Since both reactions are of first order with
respect to compound ( I ) , thermal rearrangement of ( I ) to
cis,cis-l,5-cyclooctadiene can be strongly suppressed by
working with high concentrations of potassium rert-butoxide.
Moreover, cis,cis-1,5-cyclooctadiene undergoes partial isomerization to cis,cis-l,3-cyclooctadieneunder the reaction
conditions given above.
The equilibrium set up between (Za), (2b). and (3) in the
presence of the basic catalyst can be utilized, inter a h , to
isolate (31, the isomer having the lowest boiling point, in a
yield in excess of 60%, by means of a spinning-band column.
Like 1.2-dimethylenecyclobutanec4-61, (2a) and (26) can
react with maleic anhydride in two steps. Compound ( 3 )
reacts with one mole of maleic anhydride to give (61.
(2a) is considerably more reactive than (2b) ; consequently,
when a mixture of the two isomers is allowed to react under
mild conditions it is only (2a) that actually undergoes reaction. (2b) can subsequently be drawn off and subjected t o
reaction under more drastic conditions. (Pure (2b) can be
obtained in this way.)
The steric uniformity of the products obtained from (2a) or
(2b) and the dienophile I does not depend on the reactivity
of the dienophile (71.
A particular advantage lies in the fact that the four-membered ring of the primary product ( 4 ) opens at 140 ' C to give
Angew. Chem. internnr. Edit.
1 Vol. 8 (1969) No. 3
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