Synthesis of benzvalene

Full text of DOI:10.1021/jo990883g

J . Org. Chem. 1999, 64, 7663-7664
7663
Syn th esis of Ben zva len e†
13-16 are illustrative.8,9 The source of the benzvalene
Thomas J . Katz,* Ronald J . Roth, Nancy Acton, and
Eileen J ang Carnahan
Department of Chemistry, Columbia University,
New York, New York 10027
Received J une 1, 1999
for all the studies described above was an unpublished
procedure available until recently from Organic Synthe-
ses, Inc. Because it is no longer available, we are
publishing it here. The synthesis was developed after it
had been discovered that the combination of lithium
Benzvalene (1, tricyclo[3.1.0.02,6]hex-3-ene) was first
prepared in 1966 by photoirradiating benzene, but the
amount that could be made in this way was tiny. Since
971, the combination of cyclopentadiene, methylene
1
10
11
2
1
chloride, and methyllithium (eq 1) has made benzvalene
cyclononatetraenide, methylene chloride, and n-butyl-
lithium gives isobullvalene (13),1
2,8a,b
a structure related
to [10]annulene as benzvalene is to benzene. It has been
used by Professor Manfred Christl to prepare, during a
period of a number of years, more than 5 kg of benz-
valene.4
-6,13
3
available easily and in quantity and has allowed it to
be used as the starting material for the synthesis of a
variety of its derivatives4 and of the parents and
derivatives of a number of other skeletons, including
Discu ssion
,5
The choice of solvent for the synthesis is important
because carbenoid reactions of lithium halomethides
occur best in those that solvate lithium cations poorly.
-12.4,6 The mechanism of the transformation has been
2
1
4
However, diethyl ether, the solvent commonly used for
carbenoid reactions, gives only a low yield of benzvalene,
probably because it dissolves only a small amount of
lithium cyclopentadienide. Dimethyl ether, in contrast,
gives a good yield, and although it also offers the
advantage that distillation separates it easily from
benzvalene,15 the preparation of large samples of pure
benzvalene by distillation has not been studied because
7
analyzed, and the method used to prepare 1 has been
3
of benzvalene’s explosiveness. Instead, the synthesis is
applied to synthesize a number of ring systems, of which
performed in mixtures of dimethyl and diethyl ethers,
so that when the product is distilled, the benzvalene is
diluted by an inert solvent. Pure benzvalene, when
subjected to shock, explodes. However, its solutions have
never been reported to do so although they have been
used for innumerable experiments during the past 28
years.
†
Dedicated to Prof. Manfred Christl (University of W u¨ rzburg) with
appreciation for the many structures he has synthesized from benz-
valene.
1) Wilzbach, K. E.; Ritscher, J . S.; Kaplan, L. J . Am. Chem. Soc.
967, 89, 1031.
2) Light also destroys it: Kaplan, L.; Wilzbach, K. E. J . Am. Chem.
Soc. 1968, 90, 3291.
3) Katz, T. J .; Wang, E. J .; Acton, N. J . Am. Chem. Soc. 1971, 93,
782.
(
1
(
(
3
(
(
4) Review: Christl, M. Angew. Chem., Int. Ed. Engl. 1981, 20, 529.
5) (a) Schl u¨ ter, A.-D.; Belzner, J .; Heywang, U.; Szeimies, G.
(8) 13: (a) Katz, T. J .; Cheung, J . J .; Acton, N. J . Am. Chem. Soc.
1970, 92, 6643. (b) Hojo, K.; Seidner, R. T.; Masamune, S. J . Am. Chem.
Soc. 1970, 92, 6641. 14: ref 3. 15: (c) Murata, I.; Nakasuji, K.
Tetrahedron Lett. 1973, 47. (d) Pagni, R. M.; Watson, C. R. Tetrahedron
Lett. 1973, 59. 16: Murata, I.; Tatsuoka, T.; Sugihara, Y. Tetrahedron
Lett. 1974, 199.
Tetrahedron Lett. 1983, 24, 891. (b) Christl, M.; Freund, S. Chem. Ber.
985, 118, 979. (c) Christl, M.; Mattauch, B.; Irngartinger, H.;
Goldmann, A. Chem. Ber. 1986, 119, 950. (d) Kunz, U.; Krimm, S.;
Fischer, T.; Kottke, T.; Stalke, D.; Christl, M. Eur. J . Org. Chem. 1998,
1
2
171, 1.
6) In addition to those in Christl’s review (ref 4), references include
the following. For 3: (a) Hashmi, A. S. K.; Szeimies, G. Chem. Ber.
994, 127, 1075. (b) Graf, S.; Szeimies, G. Tetrahedron 1993, 49, 3101.
c) Freund, S.; Henneberger, H.; Christl, M. Chem. Ber. 1988, 121,
665. (d) Reference 5c. (e) Christl, M.; Leininger, H.; Kemmer, P. Chem.
(9) A number of related examples are cited in ref 7. Others are in
(a) Pagni, R. M.; Burnett, M.; Hazell, A. C. J . Org. Chem. 1978, 43,
2750. (b) Burger, U.; Thorell, P.-J .; Schaller, J .-P. Tetrahedron Lett.
1990, 31, 3155.
(10) Katz, T. J .; Roth, R. J .; Acton, N.; Carnahan, E. J . Org. Synth.
1973, 53, 157, unpublished procedure. There are 39 citations to this
reference in the Science Citation Index. Organic Syntheses did not
publish the procedure because its execution “demands too high a skill”,
because “the yields obtained by the checker are too low”, because the
“product is too dangerous”, and because “the reaction probably lacks
generality”.
(
1
(
1
Ber. 1984, 117, 2963. (f) Leininger, H.; Kemmer, P.; Beck, K.; Christl,
M. Chem. Ber. 1982, 115, 3213. For 4: (g) Christl, M.; Herzog, C.;
Br u¨ ckner, D.; Lang, R. Chem. Ber. 1986, 119, 141. For 5: (h) Christl,
M.; Herzog, C.; Kemmer, P. Chem. Ber. 1986, 119, 3045, and earlier
work cited therein. For 6: (i) Christl, M.; T u¨ rk, M.; Peters, E.-M.;
Peters, K.; von Schnering, H. G. Angew. Chem., Int. Ed. Engl. 1994,
(11) Organic Syntheses, Inc., has discontinued distributing unpub-
lished procedures.
3
3, 1639. For 7: (j) Christl, M.; Brunn, E.; Lanzend o¨ rfer, F. J . Am.
Chem. Soc. 1984, 106, 373; ref 6e. For 8: (k) Snyder, G. J .; Dougherty,
D. A. J . Am. Chem. Soc. 1989, 111, 3927. (l) Swager, T. M.; Grubbs, R.
H. J . Am. Chem. Soc. 1989, 111, 4413. (m) Leininger, H.; Lanzend o¨ rfer,
F.; Christl, M. Chem. Ber. 1983, 116, 669. (n) Leininger, H.; Christl,
M.; Wendisch, D. Chem. Ber. 1983, 116, 681. For 9: ref 6l. For 10: ref
(12) Katz, T. J .; Cheung, J . J . J . Am. Chem. Soc. 1969, 91, 7772.
(13) Prof. Manfred Christl, University of W u¨ rzburg, private com-
munication.
(14) (a) Closs, G, L.; Closs, L. E. J . Am. Chem. Soc. 1960, 82, 5723.
(b) K o¨ brich, G.; Merkele, H. H. Chem. Ber. 1966, 99, 1782. (c) K o¨ brich.
G.; et al. Angew. Chem., Int. Ed. Engl. 1967, 6, 41. (d) Burger, U.;
Huisgen, R. Tetrahedron Lett. 1970, 3049.
6
e. For 12; (o) Christl, M.; Mattauch, B. Chem. Ber. 1985, 118, 4203.
7) Review: Burger, U.; Thorel, P. J .; Mentha, Y. Chimia 1987, 41,
(
2
6.
(15) Dimethyl ether boils at -25 °C.
1
0.1021/jo990883g CCC: $18.00 © 1999 American Chemical Society
Published on Web 09/14/1999

7
664 J . Org. Chem., Vol. 64, No. 20, 1999
Notes
According to Christl’s students13 and Swager and
which was cooled in the dry ice-acetone mixture. The product,
a solution of benzvalene in ether, was distilled at aspirator
vacuum into this flask. The yield was ca. 400 mL of 0.7 M
benzvalene in ether.18 The benzvalene was contaminated with
only 5-10% of benzene. In seven experiments, the yields of
benzvalene ranged from 30 to 59% and averaged 45 ( 5%.
Ca u tion : The distillation residue should be destroyed cau-
tiously, for explosions have occurred when the residue was
simply exposed to air or water. While the flask was being flushed
with nitrogen, the distillation head was replaced by a stopcock
sealed with a serum-bottle cap connected to a Teflon tube
through which diethyl ether (100 mL) was syringed. The mixture
was stirred, and wet ether (20 mL) was added in drops, followed
Grubbs,6 the second batch of methyllithium in eq 1 can
l
be replaced by the cheaper n-butyllithium in hexanes,
and according to Christl’s students, so can the first batch.
In this latter case, because the reaction is more vigorous,
the cyclopentadiene must be added more slowly.13
Exp er im en ta l Section
A flame-dried 2 L round-bottomed flask was fitted with an
airtight mechanical stirrer, dropping funnel, and low-tempera-
ture thermomether and was connected via a branched inlet to a
source both of gases and (through a tube filled with Drierite)
aspirator vacuum (the “gas inlet”) and to a stopcock sealed with
a serum-bottle cap. Methyllithium in diethyl ether (400 mL, 1.6
M, containing 0.4% lithium chloride) was introduced by syringe.
The aspirator was then used to remove the ether. While the flask
was cooled in a bath of dry ice and acetone, dimethyl ether (ca.
1
9
by methanol (100 mL) and, very slowly, water (100 mL).
Pure benzvalene can be isolated by GLPC, but it explodes
when scratched. The GLPC was conducted as recommended by
1
Wilzbach, Ritscher, and Kaplan, using an unheated 5 ft × 1/4
in. aluminum column, packed with 5% isodecyl phthalate and
1
.25% triethanolamine on 45/60 Chromosorb G, and a helium
flow of 100 mL/min. The injector and detector were heated to
75 °C.
1
4
L) was distilled from LiAlH into the flask through the gas
1
6
inlet. The temperature was raised to -35 °C, and cyclopenta-
diene (52 mL, 640 mmol) was added slowly by syringe (at ca. 1
mL/min). After the vigorous evolution of methane had subsided,
methylene chloride (60 mL, 940 mmol) was added to the slurry
Ack n ow led gm en t. We thank the National Science
Foundation for support and Professor Manfred Christl
(
again at ca. 1 mL/min). Methyllithium in ether (440 mL, 1.6
(University of W u¨ rzburg) for advice and unpublished
M, containing 0.4% lithium chloride) was then added in drops
from the dropping funnel. (The slurry was now yellow.) While
the apparatus was flushed with nitrogen, the stopcock with the
serum-bottle cap was replaced by a distillation head, condenser,
and receiver, all of which had been washed with aqueous
ammonia and dried. The dimethyl ether was distilled at atmo-
spheric pressure and ambient temperature into a receiver that
details.
J O990883G
(17) Christl’s students do not collect the Me
2
O, but by sending its
vapors through a rubber or plastic tube to a Bunsen burner in an
adjacent fume hood, burn it.
(18) Approximately 20 mg of nitrobenzene was weighed into a base-
washed NMR tube. A 0.5 mL aliquot of the benzvalene solution was
added, and the yield was analyzed by comparing the intensities of the
1
3
1
7
was cooled in dry ice-acetone. When the pot temperature
reached 20 °C, the receiver was replaced by a 500 mL flask,
1
olefinic and aromatic H NMR absorptions.
(
16) In Christl’s lab, the dimethyl ether was distilled from the tank
(19) Brunn, E. Ph.D. Dissertation, University of W u¨ rzburg, 1983,
destroyed the residue by adding to it 700 mL of petroleum ether (bp
50-70 °C) and then carefully in succession EtOAc, EtOH, and H O.
2
into the flask through two towers (each 6 cm in diameter, 40 cm high),
the first filled with P
1
3
2
O
5
on pumice, the second with KOH pellets.