Preparative methodology and pyrolytic behavior of anthrylmonocarbenes: Synthesis and chemistry of 1H-cyclobuta[de]anthracene

Article abstract of DOI:10.1021/jo981105b

This study involves (1) the behavior of organolithium reagents (1-6), (2) development of efficient methods for preparing 9(7)- and 1(8)- [methoxy(trimethylsilyl)methyl]anthracenes and their analogues, (3) the intramolecular chemistry of the 9(9)- and 1(10)-anthrylcarbenes generated by pyrolyses of 7 and 8, respectively, and (4) investigation of thermal behavior and bromination of the 1H-cyclobuta[de]anthracene (11) obtained from 9 or 10. α-Methoxy-9-anthrylmethyllithium (1), prepared from 9- (methoxymethyl)anthracene (14) and t-BuLi in TMEDA/Et₂O/pentane, reacts at C-10 with D₂O, chlorotrimethylsilane, dimethyl sulfate, benzoyl chloride, acetaldehyde, benzaldehyde, and acetone to give, after neutralization, 9,10- dihydro-9-(methoxymethylene)-10-substituted-anthracenes 15 and 21a-f. However, lithiation of 9-(thiomethoxymethyl)anthracene (25) with t- BuLi/TMEDA/Et₂O/pentane occurs by an apparent radical-anion displacement process to give 9-anthrylmethyllithium (3), which then reacts with chlorotrimethylsilane to yield 9-(trimethylsilylmethyl)anthracene (28). Similarly, 28 is formed from 25 and from 9- (trimethylsilyloxymethyl)anthracene (29) with lithium and then chlorotrimethylsilane. The electrophiles D₂O, dimethyl sulfate, and benzaldehyde react with 3 at its methyl and its C-10 positions. [Methoxy(trimethylsilyl)methyl]arenes 40-42 and 7 are obtained by reactions of their aryllithium and arylmagnesium bromide precursors with bromo(methoxy)methyltrimethylsilane (39). 1-(Methoxymethyl)anthracene (45) is converted conveniently by t-BuLi and chlorotrimethylsilane to 8. Flash- vacuum pyrolyses of 7 and 8 yield 11 preparatively; 11 then thermolyzes to 2H-cyclopenta[jk]fluorene (46). Decomposition of 9-deuterio-10- [methoxy(trimethylsilyl)methyl]anthracene (55) at 650 °C/10^-3 mm results in 10(56)- and 1(57)-deuteriocyclobutanthracenes, thus revealing that the 10- deuterio-9-anthrylcarbene inserts to give 56 and also isomerizes extensively before yielding 57. Of note is that 56 isomerizes thermally by C₁₀-D movement to form 2-deuteriocyclopentafluorene 58, 57 rearranges by C₁₀-H movement to yield deuteriocyclopentafluorene 59, and 58 and 59 equilibrate 1,5-sigmatropically. Possible mechanisms for the isomerizations of 56 and 57 are outlined. Further, bromine adds rapidly to 11 to form 9,10-dibromo-9,10- dihydro-1H-cyclobuta[de]anthracene (94), which eliminates HBr on warming to yield 10-bromo-1H-cyclobuta[de]anthracene (95).

Full text of DOI:10.1021/jo981105b

J . Org. Chem. 1999, 64, 4255-4266
4255
P r ep a r a tive Meth od ology a n d P yr olytic Beh a vior of
An th r ylm on oca r ben es: Syn th esis a n d Ch em istr y of
1H-Cyclobu ta [d e]a n th r a cen e
J . Kirby Kendall,† Thomas A. Engler,‡ and Harold Shechter*
Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
Received J une 9, 1998
This study involves (1) the behavior of organolithium reagents (1-6), (2) development of efficient
methods for preparing 9(7)- and 1(8)-[methoxy(trimethylsilyl)methyl]anthracenes and their
analogues, (3) the intramolecular chemistry of the 9(9)- and 1(10)-anthrylcarbenes generated by
pyrolyses of 7 and 8, respectively, and (4) investigation of thermal behavior and bromination of
the 1H-cyclobuta[de]anthracene (11) obtained from 9 or 10. R-Methoxy-9-anthrylmethyllithium (1),
prepared from 9-(methoxymethyl)anthracene (14) and t-BuLi in TMEDA/Et2O/pentane, reacts at
C-10 with D2O, chlorotrimethylsilane, dimethyl sulfate, benzoyl chloride, acetaldehyde, benzalde-
hyde, and acetone to give, after neutralization, 9,10-dihydro-9-(methoxymethylene)-10-substituted-
anthracenes 15 and 21a -f. However, lithiation of 9-(thiomethoxymethyl)anthracene (25) with
t-BuLi/TMEDA/Et2O/pentane occurs by an apparent radical-anion displacement process to give
9-anthrylmethyllithium (3), which then reacts with chlorotrimethylsilane to yield 9-(trimethylsi-
lylmethyl)anthracene (28). Similarly, 28 is formed from 25 and from 9-(trimethylsilyloxymethyl)-
anthracene (29) with lithium and then chlorotrimethylsilane. The electrophiles D2O, dimethyl
sulfate, and benzaldehyde react with 3 at its methyl and its C-10 positions. [Methoxy(trimethylsilyl)-
methyl]arenes 40-42 and 7 are obtained by reactions of their aryllithium and arylmagnesium
bromide precursors with bromo(methoxy)methyltrimethylsilane (39). 1-(Methoxymethyl)anthracene
(45) is converted conveniently by t-BuLi and chlorotrimethylsilane to 8. Flash-vacuum pyrolyses
of 7 and 8 yield 11 preparatively; 11 then thermolyzes to 2H-cyclopenta[jk]fluorene (46).
Decomposition of 9-deuterio-10-[methoxy(trimethylsilyl)methyl]anthracene (55) at 650 °C/10-3 mm
results in 10(56)- and 1(57)-deuteriocyclobutanthracenes, thus revealing that the 10-deuterio-9-
anthrylcarbene inserts to give 56 and also isomerizes extensively before yielding 57. Of note is
that 56 isomerizes thermally by C10-D movement to form 2-deuteriocyclopentafluorene 58, 57
rearranges by C10-H movement to yield deuteriocyclopentafluorene 59, and 58 and 59 equilibrate
1,5-sigmatropically. Possible mechanisms for the isomerizations of 56 and 57 are outlined. Further,
bromine adds rapidly to 11 to form 9,10-dibromo-9,10-dihydro-1H-cyclobuta[de]anthracene (94),
which eliminates HBr on warming to yield 10-bromo-1H-cyclobuta[de]anthracene (95).
The present investigation involves (1) the behavior of
organolithium reagents 1-6 and development of methods
for synthesis of 9(7)- and 1(8)-[methoxy(trimethylsilyl)-
methyl]anthracenes (Scheme 1), (2) pyrolyses of 7 and 8
to their respective anthrylcarbenes 9 and 10 (Scheme 1),
which insert into their peri-C-H bonds to give 1H-
cyclobuta[de]anthracene (11) and isomeric products
thereof, and (3) addition and aromatic substitution reac-
tions of 11. The initial results for preparation of cyclobu-
tarene 11 from 8 have been communicated.1 9-Anthryltet-
razole (12) has also been reported to thermolyze (11%)
† Present address: Albemarle Corporation, Magnolia, Arkansas.
‡ Present address: Eli Lilly and Company, Lilly Corporate Center,
Indianapolis, Indiana 46205.
(1) The initial observation of conversion of 8 to 11 was communicated
by Engler, T. A.; Shechter, H. Tetrahedron Lett. 1982, 23, 2715.
(2) (a) Wentrup, C.; Mayor, C.; Becker, J .; Lindner, H. J . Tetrahedron
1985, 41, 1601. (b) Tetrazole 12 is presumed to be in equilibrium with
its tautomer with the hydrogen on N-2. The structure represented as
12 is that in which the extended conjugation between the tetrazole
and the 9-anthryl moieties is maximized.
(3) Present efforts in this laboratory to prepare 11 by vacuum
pyrolysis of 9-anthryldiazomethane as generated in situ by decomposi-
tion of sodium 9-anthraldehyde p-tosylhydrazonate at 500-520 °C/
0.33 mm have failed. The reaction products are 9-methylanthracene
(20%), sodium p-tolylsulfinate, and intractables. Further, vacuum
thermolysis of sodium 9-anthraldehyde p-tosylhydrazonate at 650 °C
as above yields 9-methylanthracene (7%) and intractable products.
Neither 11 nor 46 is obtained in the above experiments.
to 9 (Scheme 2) which converts to 11.2,3 The principal
pyrolysis reaction of 12 (Scheme 2) however is conversion
to 9-cyanoanthracene (13, 85%) and hydrogen azide.2 As
10.1021/jo981105b CCC: $18.00 © 1999 American Chemical Society
Published on Web 05/26/1999

4256 J . Org. Chem., Vol. 64, No. 12, 1999
Kendall et al.
Sch em e 1
Sch em e 3
Sch em e 4
Sch em e 2
from combination of the tert-butyl radical and the 9-an-
thrylmethyl radical (19).
The behavior of 1 was then investigated with various
electrophiles. Reaction of D2O with the mixture resulting
from 14/t-BuLi/TMEDA/Et2O/pentane at -78 °C yields
10-deuterio-9,10-dihydro-9-(methoxymethylene)anthra-
cene (21a , >17%), 9-anthraldehyde (22, 39%) containing
64% D at C-10, and 17. Dimethyl sulfate and 14 as above
give 10-methyl derivative 21b (75%) along with 17 (20%).
Benzoyl chloride, acetaldehyde, benzaldehyde, and ace-
tone as described in detail in the Supporting Information
react with 14 at -78 °C to yield 21c-f (39-55%),
respectively, along with 17 (23-36%). Thus, kinetically
will be described, cyclobutarene 11 undergoes compli-
cated rearrangement reactions that are major concerns
of this research.
Resu lts a n d Discu ssion
1. Th e Beh a vior of 1-6; Syn th esis of 7 a n d 8. In
the present program, synthesis of 7 was first attempted
from 9-(methoxymethyl)anthracene (14) in Et2O and
tetramethylethylenediamine (TMEDA) by addition of
t-BuLi in pentane and then chlorotrimethylsilane at -78
°C and warming the reactants to ∼25 °C. R-Methoxy-9-
anthrylmethyllithium (1, Scheme 3), a green-black soluble
material, is formed but reacts with chlorotrimethylsilane
to give, after chromatography, (methoxymethylene)tri-
methylsilylanthracene 15 (>40%),4 9-anthraldehyde (16,
27%), and 9-neopentylanthracene (17, 16%). Silane 15
results from silylation of the ambident lithium reagent
1 at C-10 (Scheme 3). Anthraldehyde 16 arises from
hydrolysis, desilylation, and air oxidation of 15 during
workup and chromatography. Formation of 17 in com-
petition with 15 can be rationalized by electron transfer
from t-BuLi to 14 and the radical-anion process in
Scheme 4. Less likely, coupling product 17 might result
controlled reactions of
1 with electrophiles yield
9,10-dih ydr o-9-m et h oxym et h ylen e-10-su bst it u t ed-
anthracenes (15, 21a -f) regardless of the reactant.4
(4) (a) The behavior of 1 with electrophiles to give 15 and 21a -f is
similar to that reported for protonation and alkylation of (9-anthryl)-
arylmethyl anions4b and suggested for reactions of 9-anthrylmethyl
anions.4c (b) Takagi, M.; Nojima, M.; Kusabayashi, S. J . Am. Chem.
Soc. 1983, 105, 4676. (c) Becker, H.-D.; Andersson, K.; Sandros, K. J .
Org. Chem. 1980, 45, 4549 and references therein. For similar reactions
of 9-(diphenyl)anthrylmethyl anions4d and 2-(3-methyl)naphthylmethyl
anions,4e see (d) Takagi, M.; Nojima, M.; Kusabayashi, S. J . Chem.
Soc., Perkin Trans. 1, 1979, 2948, and (e) Mitchell, R. H.; Dingle, T.
W.; Williams, R. V. J . Org. Chem. 1983, 48, 903.
The fact that 1 does not react with electrophiles (E) to
give anthracenes 23 implies that the transition states for
attack at the methoxycarbanionic center at C-9 in 1 are
sterically hindered by interactions of the electrophilic (E)
and the methoxy (OCH3) groups with the peri-hydrogens

Synthesis and Chemistry of 1H-Cyclobuta[de]anthracene
J . Org. Chem., Vol. 64, No. 12, 1999 4257
Sch em e 5
at C-1 and C-8 and that the electron density at C-10 is
substantial.5 Indeed, X-ray and1H NMR studies of various
10-alkyl-9,10-dihydro-9-methyleneanthracenes (24; Y )
H, E ) alkyl) reveal that the central rings of the arene
derivatives are in boat or butterfly conformations in
which the C-10 alkyl groups prefer pseudoaxial positions
to avoid confrontations with the peri-hydrogens.6 Conver-
sions of 1 to 15 and 21a -f are thus facilitated as in 24
(Y ) OCH3) by entrance of the electrophiles (E) from
pseudoaxial directions. That there are structural effects
as presumed in 24 (Y ) OCH3) is revealed by the 1H NMR
spectrum of 15 in which there is downfield absorption
(7.8-8.0 ppm) of its H-1 proton; thus, there is consider-
able deshielding by the oxygen atom in the nearby
methoxy group.
Sch em e 6
Synthesis of 9-[thiomethoxy(trimethylsilyl)methyl]-
anthracene (26) for possible conversion to anthrylcarbene
9 as in Scheme 5 was then investigated. The reactions
of 9-(thiomethoxymethyl)anthracene (25) with t-BuLi (1.1
equiv)/TMEDA/Et2O/pentane and then addition of chlo-
rotrimethylsilane (1.1 equiv) at -78 °C are different
however than those proposed in Scheme 57,8 in that
9-(trimethylsilylmethyl)anthracene (28, 91%) is produced,
apparently from 3 as formed by the radical-anion mech-
anism in Scheme 6 and/or by a mechanism analogous to
that in Scheme 4. That 28 is formed by a radical-anion
displacement mechanism is supported by present find-
ings (Scheme 7) that 25 and 9-(trimethylsilyloxymethyl)-
anthracene (29) are converted by lithium (2 equiv)9 to 3,
which undergoes displacement of chlorotrimethylsilane
to give 28 in 84% and 63% yields, respectively.
Sch em e 7
Sch em e 8
Reactions of 9-anthrylmethyllithium (3), as prepared
from 25 and t-BuLi, were then examined with other
electrophiles. Treatment of 3 with D2O yields 9-methyl-
anthracene (30, Scheme 8, 88%), in which the methyl
1
group is ∼90% monodeuterated; by H NMR there is no
deuterium at C-10. Dimethyl sulfate reacts with 3
(Scheme 8) however at its C-10 and its 9-anthrylmethyl
positions, respectively, to give 9,10-dihydro-10-methyl-
9-methyleneanthracene (31) and 9-ethylanthracene (32)
(5) (a) Simple Hucke¨l calculations indicate that the C-10 ring
position in the R-methoxy-9-anthrylmethyl carbanion in 1 is the site
of highest electron density (1.317 vs 1.149 at the exo-cis position).5b
(b) Engler, T. A.; Shechter, H. Tetrahedron Lett. 1984, 24, 4645.
(6) (a) Carruthers, W.; Hall, G. E. J . Chem. Soc. B. 1966, 861. (b)
Brinkman, A. W.; Gordon, M.; Harvey, R. G.; Rabideau, P. W.; Stothers,
J . B.; Ternay, A. L., J r. J . Am. Chem. Soc. 1970, 92, 5912. (c) Zieger,
H.; Gelbaum, L. T. J . Org. Chem. 1972, 37, 1012. (d) Harvey, R. G.;
Cho, H. J . Am. Chem. Soc. 1974, 96, 2434. (e) Cho, H.; Harvey, R. G.;
Rabideau, P. W. J . Am. Chem. Soc. 1975, 97, 1140. (f) Fu, P. P.; Harvey,
R. G.; Paschal, J . W.; Rabideau, P. W. J . Am. Chem. Soc. 1975, 97,
1145. (g) Leung, P.-T.; Curtin, D. Y. J . Am. Chem. Soc. 1975, 97, 6790.
(7) Deprotonations of 25 with lithium diisopropylamide, lithium
2,2,6,6-tetramethylpiperidide, MeLi, or n-BuLi in TMEDA, Et2O, or
THF at various temperatures followed by reactions with chlorotri-
methylsilane to give 26 were unsuccessful.
in a 1:1 ratio. Further, reaction of benzaldehyde with 3
at -78 °C and then addition of aqueous NH4Cl at ∼25
°C (Scheme 8) give 9,10-dihydro-10-methylene-R-phenyl-
9-anthracenemethanol (33) and 2-(9-anthryl)-1-phenyl-
ethanol (34) in a 1:3 ratio in 82% overall yield. The
sensitivities of 9-anthrylmethyllithium reagents to steric
and electronic effects are thus impressively demonstrated
in reactions of electrophiles with 1 to give C-10 deriva-
tives 15 and 21a -f, whereas depending on the electro-
phile, 3 reacts at its 9-anthrylmethyl and/or its C-10
positions (Scheme 8).
(8) Reaction of n-BuLi (1.2 equiv) at 0 °C with 25 (1 equiv) in Et2O
containing TMEDA (1.2 equiv) and addition of chlorotrimethylsilane
(1.6 equiv) yield 9-n-pentylanthracene. No 26 is obtained.
(9) Biron, C.; Dunoques, J .; Calas, R.; Tskhovrebachvili, T. Synthesis
1981, 220.

4258 J . Org. Chem., Vol. 64, No. 12, 1999
Kendall et al.
Sch em e 10
The behavior of (trimethylsilylmethyl)anthracene 28
with strong bases followed by electrophiles was then
studied in efforts to prepare potential precursors to
carbene 9. R-Trimethylsilyl-9-(anthrylmethyl)lithium (4,
Scheme 9) is produced upon addition of n-BuLi/pentane
Sch em e 9
Sch em e 11
to Et2O/TMEDA or THF/TMEDA solutions of 28 at 0 °C.
Upon quenching 4 with CH3OD, R-deuteriosilane 35
(∼100%) is obtained, which is 70% monodeuterated at
1
its anthrylmethyl position on the basis of H NMR and
MS analyses. Since no deuterium is at C-10 in the
product, initial formation of 10-deuterio-9,10-dihydro-9-
(trimethylsilylmethylene)anthracene followed by protio-
tropic rearrangement does not occur.10
Silyl(anthrylmethyl)lithium 4 is of further interest
because of its contrasting behavior with other electro-
philes.10a As has been noted, 26 is not obtained as in
Scheme 5. Reaction of 4 with dimethyl disulfide (36, eq
1) however does give 9-(thiomethoxymethyl)anthracene
production of 11 in these experiments. Apparently the
silicon-sulfur bonding in transition state 37 (Scheme 10)
is insufficient for (thiomethoxy)trimethylsilane [(CH3)3-
Si-SCH3] to be effectively eliminated from 26 by ther-
molysis.
26 (97%) and lithium thiomethoxide. The silyl sulfide
obtained is of proper mass and is assigned as 26 from its
1H and 13C NMR spectra and UV absorptions (see
Experimental Section). A noteworthy feature in the 13C
NMR spectrum of 26 is the appearance of 14 aromatic
signals due to restricted rotation of the anthryl-CH-
(SCH3)Si(CH3)3 single bond. Such restricted rotation has
been observed in substituted 9-anthrylcarbinols.11 The
mechanism by which 36 converts 4 to 26 (eq 1) has not
been established.12a,b
The thermal behavior of 26 was then investigated in
efforts to generate 9 for production of cyclobutanthracene
11. Piptopyrolyses of 26 at 650 °C/0.05-0.10 mm at
various contact times result primarily however in forma-
tion of intractable products. There is no evidence for
Because the above studies did not result in synthesis
of 7, investigation was then initiated toward methods for
introduction of a methoxy(trimethylsilyl)methyl group
[CH3O-CH-Si(CH3)3] directly into the C-9 position in
anthracene. Bromination of (methoxymethyl)trimethyl-
silane 38 in CCl4 is known to give [bromo(methoxy)-
methyl]trimethylsilane (39, Scheme 11) in 55% yield.13,14
Phenyllithium and phenylmagnesium bromide are now
found to react with 39 in THF to form [methoxy-
(trimethylsilyl)methyl]benzene 4015 in 46% and 51%
yields, respectively. Further, 1-naphthylmagnesium bro-
mide and 5-acenaphthylmagnesium bromide are con-
verted simply by 39 to 1-[methoxy(trimethylsilyl)methyl]-
naphthalene (41, 61%)16 and 5-[methoxy(trimethylsilyl)-
methyl]acenaphthene (42, 71%), respectively. Of particu-
(10) (a) Treatment of 4 with Cp2ZrCl2 also gives the product of
reaction at C-9.10b (b) Leppert, M. F.; Raston, C. L.; Engelhardt, L.
M.; White, A. H. J . Chem. Soc., Chem. Commun. 1985, 521. (c) Reaction
of 4, however, with chlorotrimethylsilane results in trimethylsilylation
at C-10 to give 9,10-dihydro-10-[(trimethylsilylmethylene)-9-anthryl]-
trimethylsilane in 55% yield.5b
(11) (a) de Riggi, I.; Virgili, A.; de Moragas, M.; J aime, C. J . Org.
Chem. 1995, 60, 27. (b) J aime, C.; Virgili, A.; Claramunt, R. M.; Lo´pez,
C.; Elguero, J . J . Org. Chem. 1991, 56, 6521. (c) The 13C NMR spectrum
of 7 shows again a fourteen line pattern for the anthryl group.
(12) (a) Among the attractive reaction mechanisms are (1) displace-
ment of dimethyl disulfide by 4, (2) electron transfer of 4 to dimethyl
sulfide and then coupling of R-trimethylsilyl-9-anthrylmethyl and
methanethio radicals, and (3) displacement of dimethyl disulfide at
C-10 of 4 to give trimethyl[(10-methylthio)-9(10H)-anthrylidene]-
methylsilane which is then conjugatively displaced at C-9 by meth-
anethiolate ion. Displacements as in mechanism 3 have been observed
previously for other 10-substituted-9-benzylidene-9,10-dihydroan-
thracenes.10b,12b (b) Takagi, M.; Nojima, M.; Kusabayashi, S. J . Chem.
Soc., Perkin Trans. 1 1981, 2637 and references therein.
(13) (a) Christiansen, M. L.; Benneche, T.; Undheim, K. Acta Chem.
Scand. 1987, B41, 536. (b) Similarly, chlorination of 38 gives chloro-
(methoxy)trimethylsilylmethane.13d (c) Shimizo, S.; Ogata, M. Tetra-
hedron 1989, 45, 637. (d) Both halosilanes, 38 and chloro(methoxy)-
trimethylsilylmethane, undergo nucleophilic displacements of halogen
with enolates and with 1,2,4-triazole.13a,c
(14) We thank J ohn E. Strode for bringing attention to ref 13a,c
and for suggesting study of reactions of various aryl organometallic
reagents with 39.
(15) (a) Silyl derivative 40 was first prepared by (1) deprotonation
of benzyloxytrimethylsilane [(CH3)3SiOCH2Ph] with t-BuLi and (2)
Wittig rearrangement of R-(trimethylsiloxy)benzyllithium [(CH3)3-
SiOCH(Ph)Li] to lithium R-(phenyl)trimethylsilylmethoxide [(CH3)3-
SiCH(Ph)OLi], followed by methylation with dimethyl sulfate.15b (b)
Wright, A.; West, R. J . Am. Chem. Soc. 1974, 96, 3214. (c) Silane 40
has also been obtained15d by reaction of benzaldehyde with tris-
(trimethylsilyl)aluminum and methylation with dimethyl phosphite
[HOP(OCH3)2]. (d) Tsuge, O.; Kanemasa, S.; Nagahama, H.; Tanaka,
J . Chem. Lett. 1984, 1803.

Synthesis and Chemistry of 1H-Cyclobuta[de]anthracene
J . Org. Chem., Vol. 64, No. 12, 1999 4259
Sch em e 12
Sch em e 14
Sch em e 13
amount of the quartz chips in the pyrolysis tube by 66%
has little effect on the ratio of 46 to 11 obtained.
Cyclobutanthracene 11 may be presumed to be formed
from 7 (Scheme 14) upon generation of 9 and then peri-
cyclization as in 47.19 It will be seen shortly however that
the processes leading to the final insertion act to give 11
are far more complicated than summarized in Scheme
14. Also, upon isolation, 11 decomposes when warmed
and turns brown-red rapidly when exposed to air. The
structure of 11 is assigned from its exact mass and its
1H and 13C NMR spectra and by elemental analysis of
its stable 1:1 solid complex (48) with 2,4,7-trinitrofluo-
renone. The chemistry of 11 will be described later.
lar importance is that 7 (59%)11c is now obtained satis-
factorily from 9-bromoanthracene (43) and n-BuLi (1
equiv) and subsequent reaction of 9-anthryllithium (44)
with 39 (Scheme 12). The new methodology for preparing
methoxy(trimethylsilyl)methyl derivatives is simple and
convenient.
In contrast to 7, 1-[methoxy(trimethylsilyl)methyl]-
anthracene (8) has been found to be preparable by
traditional methodology.16b 1-(Methoxymethyl)anthracene
(45, Scheme 13) is converted simply by t-BuLi/TMEDA/
Et2O/pentane to 1-lithio derivative 6 at approximately
-110 °C; addition of chlorotrimethylsilane and warming
to ∼ 25 °C then give 8 in 68% yield. The radical-anion
reactions that plagued lithiation of 14 are avoided with
45 at approximately -110 °C. At temperatures of -78
°C however 45 is converted by t-BuLi/TMEDA/Et2O/
pentane and then chlorotrimethylsilane to 8 in only 23-
33% yields.
Cyclopentafluorene 46 is assigned (1) upon reduction
with lithium aluminum hydride to 2,9b-dihydro-1H-
cyclopenta[jk]fluorene (49) and agreement of its MS and
1H NMR spectra with literature values18 and (2) by direct
comparison of its melting point, mixed melting point, and
spectral properties (GC-IR-MS) with an authentic
sample prepared by pyrolysis of spiro[indazol-3,1′-indene]
(50) as synthesized by addition of 1-diazoindene to
benzyne.18 Probable mechanisms for formation of 46 will
be discussed later.
2. F la sh -Va cu u m P yr olyses of 7 a n d 8 to Cyclobu -
ta n th r a cen e 11 a n d P r od u cts Th er eof. Carbenic
decompositions of methoxy(trimethylsilylmethyl)anthra-
cenes 7 and 8 have now been studied in detail. Flash-
vacuum pyrolysis of 7 at 550 °C/10-3 mm in quartz-
packed equipment and column chromatography of the
pyrolysate are now found (eq 2) to yield 11 (43%, Table
Because 46 is formed along with 11 in decomposition
of 7, pyrolysis of tetrazole 12 was reinvestigated. As in
the previous report2 thermolysis of 12 gives 11 in low
yield, nitrile 13 (85%, Scheme 2), and hydrogen azide.
At 660 °C/10-3 mm however in the present experiments,
decomposition of 12 also yields 46 (eq 3). Cyclobutan-
1)17 along with 2H-cyclopenta[jk]fluorene (46, 35%).18 The
effects of reaction temperature and contact time on the
yields of 11 and 46 are summarized in Table 1. As the
Ta ble 1. Yield s of 11 a n d 46 fr om 7 a t Va r iou s
Tem p er a tu r es
temp, °C
11, %
46, %
temp, °C
11, %
46, %
450
500
550
8
19
43
550a
660
750
32
20
17
51
70
5
35
thracene 11 presumably forms from 9 as shown in
Scheme 1 and detailed in 47. Production of 46 during
decomposition of 12 is similar to that from 7.
a
The contact time was ∼5% that of the other pyrolyses.
(18) Cyclopentafluorenes 46 and 49 have been prepared previously
by Luger, P.; Tuchscherer, C.; Grosse, M.; Rewicki, D. Chem. Ber. 1976,
109, 2596.
temperature and contact time for decomposition of 7
increase, the ratios of 46 to 11 increase. Reducing the
(19) Such peri-cyclobutacyclizations have been reported by (a)
Bailey, R. J .; Shechter, H. J . Am. Chem. Soc. 1974, 96, 8116. (b) Becker,
J .; Wentrup, C. J . Chem. Soc., Chem. Commun. 1980, 190. (c)
References 1, 2, and 16b. (d) Bailey, R. J .; Card, P. J .; Shechter, H. J .
Am. Chem. Soc. 1983, 105, 6096. (e) J aworek, W.; Vo¨gtle, F. Chem.
Ber. 1991, 124, 347.
(16) (a) Obtained previously by reaction of chlorotrimethylsilane
with R-methoxy-1-naphthylmethyllithium, as generated from 1-(meth-
oxymethyl)naphthalene and t-BuLi in Et2O containing TMEDA.16b (b)
Engler, T. A.; Shechter, H. See the preceding paper in this issue.
(17) References 1 and 2 report previous preparations of 11.

4260 J . Org. Chem., Vol. 64, No. 12, 1999
Kendall et al.
Sch em e 15
The thermal behavior of [methoxy(trimethylsilyl)-
methyl]anthracene 8 has been compared to that of 7.
Flash-vacuum decomposition of 8 (eq 4) in a quartz-
packed tube at 550 °C/10-3 mm results in elimination of
methoxytrimethylsilane and formation of 11 (41%) and
46 (22%).
At 660 °C/10-3 mm, the yield of 46 is increased to 57%
and that of 11 is reduced to 15%. The conversion of 8 to
11 presumably involves generation of anthrylcarbene 10
(Scheme 1) and then peri-cyclization as in 51.19 The
Sch em e 16
present overall results of pyrolysis of 7 (eq 2), 12 (eq 3),
and 8 (eq 4) are similar in that both 11 and 46 are found.
Among the questions of interest then is if 46 is formed
from 11, directly from 9 and/or 10, or otherwise.
Pure cyclobutanthracene 11 was then pyrolyzed under
conditions similar to those used previously for flash-
vacuum decompositions of 7, 8, and 12. At temperatures
ranging from 525 to 725 °C, 46 (eq 5) is formed. At 550
Sch em e 17
°C/10-3 mm, 11 is 50% converted to 46. Clearly 46 is
produced by thermal isomerization of 11 (eq 5).
Because of the interesting rearrangement of 11 to 46,
investigation of the reaction mechanism was initiated by
study of thermolysis of 9-deuterio-10-[methoxy(trimeth-
ylsilyl)methyl]anthracene (55, 94% monodeuterated at
C-10) prepared from 9,10-dibromoanthracene (52)20 as
summarized in Scheme 15.
Pyrolysis of 55 at 650 °C/10-3 mm and separation of
the products by MPLC yield first a fraction consisting of
10(56)- and 1(57)-deutero-1H-cyclobutanthracenes (Scheme
16) and a second composed of 1(58)- and 2(59)-deuterio-
1
cyclopenta[jk]fluorenes (Scheme 16). H NMR spectral
analysis reveals that the cyclobutanthracene product
contains 0.38 deuterium at its peri-position (56) and 0.40
deuterium at its C-10 position. No deuterium is apparent
at any other positions of the ring system. These results
correspond to 56 and 57 being collected in essentially
equal amounts with loss of 0.16 deuterium to the pyroly-
sis apparatus. The cyclopentafluorene product is 58 and
59 in a ratio of 1:2 with overall loss of 0.05 deuterium.
Decomposition of 55 at 600 °C/10-3 mm gives 56 and 57
in a 2:1 ratio (with loss of 0.07 deuterium), thus demon-
strating that there is less carbene travel around the
anthryl ring system when the pyrolysis temperature is
lowered (see subsequent discussion). Isomers 58 and 59
are again produced in a ratio of 1:2. Production of 56-
59 in the above experiments leads to questions of reaction
mechanism that are now of concern.
In the decompositions of 55, deuteriocyclobutan-
thracene 56 is apparently formed by (1) peri-insertion of
10-deuterio-9-anthrylcarbene (60, Scheme 17)19 and/or by
(2) multistep isomerization of 60 to 10-deuterio-1-an-
thrylcarbene (66)21,22 followed by peri-insertion (Scheme
17).19 Deuteriocyclobutanthracene 57 is also a significant
product (Scheme 16) and presumably results (in part)
from extended rearrangement of 60 to 67,21,22 which then
(20) (a) Heilbron, I. M.; Heaton, J . S. Org. Synth. Coll. Vol 1, 1941,
207. (b) Bachmann, W. E.; Kloetzel, M. C. J . Org. Chem. 1938, 3, 55.

Synthesis and Chemistry of 1H-Cyclobuta[de]anthracene
J . Org. Chem., Vol. 64, No. 12, 1999 4261
Sch em e 18
Sch em e 19
inserts at C-9 (Scheme 18). A further possibility is
multistep rearrangement of 67 to 6821,22 and then peri-
insertion to yield 57 (Scheme 18). Whatever be the details
of the mechanisms for conversion of 60 to 57, it is
impressive that the many step processes resulting in
formation of 57 (Scheme 18) compete so well with direct
peri C1-H insertion of 60 to give 56 (Scheme 17).
Of interest also are the paths by which 56 and 57 are
converted to 58 and 59. It is significant that in rear-
rangements of 56 there are no products produced by
dyotropic mechanisms23 involving migration of deuterium
from C-10 or any subsequent aromatic center to give
cyclopentafluorenes (69 or 70) with deuterium at any of
C10-D to give 58, which then undergoes deuterium-
hydrogen rearrangment to yield 59. A similar overall
process (Scheme 16) involving movement of C10-H in 57
to form 59 and then 58 by hydrogen-deuterium sigma-
tropic rearrangement would then be expected.
As has been noted, 11 begins to decompose on warming
to 70-80 °C.1 At higher temperatures, the simpler peri-
bridged arene, 1H-cyclobuta[de]naphthalene (76a ), ring-
opens in hydrogen-donor environments to give 1-meth-
ylnaphthalene (79) presumably by reduction of 77a or/
and 78a . Further, 1-methyl-1H-cyclobuta[de]naphthalene
their benzenoid positions. Thus a dyotropic process as
in Scheme 19 is not operative. There are many other
thermal dyotropic mechanisms starting from 56 that
have been considered which involve migration of deute-
rium from an aromatic ring to give deuteriocyclopen-
tafluorenes, but none account for the conversions of 56
and 57 to 58 and 59. Mechanisms of a completely
different type must occur to produce 58 and 59 from 56
and 57.
Important then is that decompositions of 56 and 57
yield 58 and 59 in a 1:2 ratio. This ratio is exactly that
expected for equilibration of 58 and 59 by 1,5-sigmatropic
rearrangements.24 That 69 and 70 are not formed sug-
gests that 56 isomerizes (Scheme 16) by movement of
(76b) thermolyzes to 1-vinylnaphthalene (80) by hydro-
gen transfer from the methyl group in 77b or/and 78b.25
As will be illustrated, analogues of 77a ,b and 78a ,b along
with other intermediates may be involved in the deep-
seated rearrangements (Scheme 16) of 56 and 57.
Scheme 20 illustrates a mechanism by which isomer-
ization of 56 to 58 occurs initially by cleavage of the
(21) Carbon-carbon rearrangements of arylcarbenes were initially
reported by (a) Vander Stouw, G. G. Ph.D. Dissertation, The Ohio State
University, Columbus, Ohio, 1964; Dissertation Abstracts Ann Arbor,
Michigan, 1965, 25, 6974. (b) J oines, R. C.; Turna, A. B.; J ones, W. J .
Am. Chem. Soc. 1969, 91, 7754. (c) Crow, W. D.; Wentrup, C. Chem.
Commun. 1969, 1387. (d) Schissel, P.; Kent, M. E.; McAdoo, D. J .;
Hedeya, E. J . Am. Chem. Soc. 1970, 92, 2147. (e) Baron, W. J .; J ones,
M., J r.; Gaspar, P. P. J . Am. Chem. Soc. 1970, 92, 4739. (f) For
summaries and detailed discussion of arylcarbene rearrangements, see
Gaspar, P. P.; Hsu, J .-P.; Chari, S.; J ones, M., J r. Tetrahedron 1985,
41, 1479, refs 2 and 22, and references therein.
Sch em e 20
(22) For recent summaries and discussion of the mechanistic aspects
of isomerization of arylcarbenes, see (a) Xie, Y.; Schreiner, P. R.;
Schleyer, P. v. R.; Schaefer, H. F., J r. J . Am. Chem. Soc. 1997, 119,
1370. (b) Matzinger, S.: Bally, T., Patterson, E. V.; McMahon, R. J . J .
Am. Chem. Soc. 1996, 118, 1996. (c) Wong, M. W.; Wentrup, C. J . Org.
Chem. 1996, 51, 7022. (d) Schreiner, P. R.; Karney, W. L.; Schleyer,
P. v. R.; Borden, W. T.; Hamilton, T. P.; Schaeffer, H. F. J . Org. Chem.
1996, 61, 7030 and references therein. (e) Albrecht, S. W.; McMahon,
R. J . J . Am. Chem. Soc. 1993, 115, 855.
(23) (a) Scott, L. T. Acc. Chem. Res. 1982, 15, 52. (b) Scott, L. T.;
Roelofs, N. H.; Tsang, T. H. J . Am. Chem. Soc. 1987, 109, 5456. (c)
Scott, L. T.; Hashemi, M. M.; Schultz, T. H.; Wallace, M. B. J . Am.
Chem. Soc. 1991, 113, 9692.
(24) For discussion of 1,5-sigmatropic rearrangements, see Wood-
ward, R. B.; Hoffmann, R. The Conservation of Symmetry; Academic
Press: New York, 1970; p 114.
(25) Card, P. J .; Friedli, F. E.; Shechter, H. J . Am. Chem. Soc. 1983,
105, 6104.

4262 J . Org. Chem., Vol. 64, No. 12, 1999
Kendall et al.
Sch em e 21
Sch em e 23
anthracene (94, 62%) of unknown stereochemistry. Elimi-
nation of hydrogen bromide from 94 occurs readily upon
recrystallization from warm benzene to give 10-bromo-
1H-cyclobuta[de]anthracene (95), a thermally sensitive
product.
Investigation is now to be made of the synthesis and
thermal, photochemical, catalyzed, and cycloadditive
behaviors of varied 10-substituted-1H-cyclobuta[de]an-
thracenes. Of particular importance will be determination
of the details of the mechanism(s) of isomerization of 11
to 46.
Exp er im en ta l Section
Sch em e 22
Gen er a l Meth od s. Methods by which melting points,
spectra, and analyses were obtained are described in ref 16b.
Unless otherwise specified, 1H NMR spectra were recorded at
90 MHz. In most of the present experiments, reactions were
conducted under argon and with solvents that were dried with
either Na, LAH, CaH2, or P2O5.
[9,10-Dih ydr o-10-(m eth oxym eth ylen e)-9-tr im eth ylsilyl]-
a n th r a cen e (15). t-BuLi (2.2 M) in pentane (2.6 mL, 5.7
mmol) was added dropwise to a stirred yellow suspension of
9-(methoxymethyl)anthracene (14, 1.1 g, 5.0 mmol) in Et2O
(120 mL) containing TMEDA (0.80 mL, 5.3 mmol) at -78 °C.
After stirring 30 min at -78 °C, the dark green-black solution
of 1 was treated with chlorotrimethylsilane (0.69 mL, 5.7
mmol) and allowed to warm to room temperature. The solution
became colorless and contained a white precipitate after 3 h.
The mixture was washed with H2O and saturated aqueous
NaHCO3, dried (MgSO4), and concentrated. Flash chromatog-
raphy of the yellow residue on silica gel using hexane as eluent
gave (1) 9-neopentylanthracene (17, 0.20 g, 16%), mp 108-
cyclobuta bridge to give diradical 81, followed by the
indicated rearrangements. It is emphasized that rear-
rangement of 56 to 58 formalized as stepwise in Scheme
20 may be modified as in Scheme 21 to involve Dewar
anthracene 85, dibenzoprismane 86, and anthravalene
87 routes26 in which initial cleavage of the methanoan-
thracene bridge does not occur. In all of the proposals
for isomerization of 56 in Schemes 20 and 21, C-10
transfers with its deuterium across the face of the ring
system to become C-10 of 58 (as labeled in Scheme 16).
The mechanisms of Schemes 20 and 21 also all account
for isomerization of 57 to 58. Of additional interest is that
vacuum pyrolysis of (1-naphthyl)diazomethane (90,
Scheme 22) to give cyclopenta[cd]indene (91)2a can be
explained by formation of 76a , which then isomerizes by
sequences similar to those in Schemes 20 and 21.
3. Ad d ition a n d Su bstitu tion Rea ction s of 11.
Study has been initiated of chemical reactions of cyclobu-
tane 11. It has been previously established that 76a
undergoes electrophilic substitution at C-4 at 0 °C upon
reaction with bromine as catalyzed by ferric bromide to
give 4-bromo-1H-cyclobuta[de]naphthalene (92, 94%).27
Irradiation (100-W light bulb) of 76a and bromine in CCl4
results however in addition to give 1aR,2â,3â,4R-tetra-
bromo-1a,2,3,4-tetrahydronaphthalene (93) as a single
product.27 Bromine has now been found to be much more
1
110 °C, lit.28 mp 104-105 °C; H NMR (CDCl3) 0.96 (s, 9H),
3.64 (s, 2H); exact mass calcd 248.1565, obsd 248.1569 and
(2) 15 (>0.59 g, >40%), mp 110-112 °C (hexane); IR (KBr,
cm-1) 1635 (CdCHOCH3); 1H NMR (CDCl3, CH2Cl2 as internal
standard) -0.55 (s, 9H), 3.55 (s, 1H), 3.83 (s, 3H), 6.55 (s, 1H),
7.0-7.5 (m, 7H), 7.8-8.0 (m, 1H); 13C NMR (CDCl3, 20 MHz)
-2.3, 43.2, 60.7, 116.3, 122.8, 124.5, 125.2, 125.5, 126.0, 126.6,
126.9, 128.2, 131.5, 133.8, 137.4, 138.0, 144.9; UV (λ, ꢀ, hexane)
311 (4 800), 272 (12 600), 242 (shoulder, 12 250), 223 (29 000),
208 nm (39 800); exact mass calcd 294.1440, obsd 294.1447.
Anal. Calcd for C19H22OSi: C, 77.49; H, 7.53. Found: C, 77.47;
H, 7.18.
Hyd r olysis a n d Oxid a tion of 15 to 9-An th r a ld eh yd e
(16). A hexane solution (4 mL) of 15 was stirred open to the
air for 20 h over silica gel. After filtration, the silica gel was
washed with benzene and Et2O, and the filtrate was concen-
trated to a yellow solid. 1H NMR analysis of the solid
containing CH2Cl2 as an internal standard showed the mixture
to be initial 15 (43%) and 16 (47% yield based on 15 that
reacted).
9,10-Dih yd r o-9-(m eth oxym eth ylen e)-10 D-a n th r a cen e
(21a ) a n d 10 D-9-An th r a ld eh yd e (22). D2O (2 mL) was
added at -78 °C to 1 (1.4 mmol, prepared as for synthesis of
15). Workup and column chromatography with 20% benzene/
(26) For important examples, discussion, and references concerning
such structures, see (a) Meador, M. A.; Hart, H. J . Org. Chem. 1989,
54, 2336. (b) Gleiter, R.; Treptow, B.; Irngartinger, H.: Oeser, T. J .
Org. Chem. 1994, 59, 2787 and (c) references therein.
(27) (a) Friedli, F. E.; Shechter, H. Tetrahedron Lett. 1985, 26, 1157.
(b) Friedli, F. E.; Shechter, H. J . Org. Chem. 1985, 50, 5710.
(28) Bullpitt, M.; Kitching, W. Synthesis 1977, 316.
reactive with 11 than with 76a . Addition of bromine to
11 (Scheme 23) in CCl4 at 20-25 °C occurs rapidly (<5
min) to yield 9,10-dibromo-9,10-dihydro-1H-cyclobuta[de]-

Synthesis and Chemistry of 1H-Cyclobuta[de]anthracene
J . Org. Chem., Vol. 64, No. 12, 1999 4263
hexane as eluent yielded (1) 17 (0.059 g, 18%), a white solid,
mp 108-110 °C, identical with an authentic sample; (2) 21a
(0.05 g, 17%), a yellow oil; 1H NMR (CDCl3) 3.52 (s, 1H), 3.83
(s, 3H), 6.70 (s, 1H), 7.0-7.4 (m, 7H), 7.8-8.0 (m, 1H); mass
spectrum m/e 223 (M+); 95% D incorporation by 1H HMR
(satisfactory analysis for 21a could not be obtained because
of its instability); and (3) 22 (0.109 g, 39%), a yellow solid
washed with saturated aqueous NaHCO3, dried (MgSO4), and
concentrated. Chromatography of the residue on silica gel with
hexane as eluent yielded 28 (89 mg, 58%). Elution with 10%
ethyl acetate/hexane gave initial 25 (44 mg, 32%). The yield
of 28 based on recovered 25 is 84%.
Meth od C. Syn th esis a n d Red u ctive Silyla tion of
9-(Tr im et h ylsiloxym et h yl)a n t h r a cen e (29). Chlorotri-
methylsilane (1.0 mL, 7.9 mmol) was added to a solution of
9-anthracenemethanol (1.1 g, 5.0 mmol) in triethylamine (1.2
mL, 8.3 mmol) and Et2O. The mixture was refluxed for 8 h,
cooled to room temperature, filtered through Celite, and
concentrated. Chromatography of the resulting solid on a short
column of silica gel with benzene as the eluent yielded 29 (1.3
1
containing 64% deuterium at C-10 as shown by H NMR and
MS.
9,10-Dih yd r o-9-(m e t h oxym e t h yle n e )-10-m e t h yla n -
th r a cen e (21b). A solution of 1 prepared by addition of t-BuLi
(2.0 M) in pentane (1.3 mL, 2.5 mmol) to a yellow suspension
of 14 (0.50 g, 2.3 mmol) in Et2O (60 mL) and TMEDA (0.4 mL,
3.7 mmol) was treated at -78 °C with dimethyl sulfate (0.35
mL, 3.7 mmol) under argon. The stirred mixture was warmed
to room temperature, refluxed for 24 h, and worked up as for
15. Flash chromatography of the products using 5% EtOAc/
hexane as eluent gave (1) 17 (0.11 g, 20%), white crystals, as
identified earlier and (2) 21b (0.40 g, 75%), light yellow
crystals, mp 123-126 °C; IR (KBr, cm-1) 1640 (CdCHOCH3),
1
g, 94%): a yellow solid, mp 74-75 °C; H NMR (CDCl3) 0.16
(s, 9H), 5.58 (s, 2H), 7.3-7.6 (m, 4H), 7.9-8.1 (m, 2H), 8.3-
8.5 (m, 3H); exact mass calcd 280.1283, obsd 280.1291.
Chlorotrimethylsilane (1.5 mL, 12 mmol) and lithium (0.10
g, 14 mmol) were then added to 29 (1.2 g, 4.2 mmol) in
anhydrous THF (50 mL). The initial dark-green solution
became brown-orange upon stirring overnight and was then
poured into Et2O, filtered, washed with H2O, dried (MgSO4),
and concentrated. The yellow oil was chromatographed on
silica gel (hexane as the eluent) to give 28 (0.88 g, 63%): a
yellow solid, mp 64-67 °C, identical with the product prepared
by Method A.
1
1230 (C-O); H NMR (CDCl3, 200 MHz) 1.36 (d, J ) 6.8 Hz,
3H), 3.86 (s, 3H), 4.02 (q, J ) 6.8 Hz, 1H), 6.76 (s, 1H), 7.2-
7.7 (m, 6H), 7.7-7.9 (m, 1H), 7.95-7.99 (m, 1H); 13C NMR
(CDCl3, 20 MHz) 26.0, 42.0, 60.9, 113.8, 122.8, 125.7, 126.1,
126.2, 126.6, 126.7, 127.0, 128.1, 132.2, 134.7, 140.4, 141.1,
145.9; exact mass calcd 236.1201, obsd 236.1195. Anal. Calcd
for C17H16O: C, 86.40; H, 6.83. Found: C, 86.46; H, 6.59.
9-(Th iom eth oxym eth yl)a n th r a cen e (25). Sodium hy-
dride (50% suspension in mineral oil, 1.9 g, 39 mmol) was
washed twice with hexane under argon and suspended in dry
THF (25 mL). Methanethiol (3.0 g, 60 mmol) was then added
by distillation, and the resulting gray-white suspension was
stirred for 15 min. A THF solution of 9-(chloromethyl)-
anthracene (7.5 g, 33 mmol) was added dropwise (45 min). The
mixture was stirred for 3 h, washed with H2O and saturated
NaHCO3, and dried (MgSO4). Removal of solvent left a yellow
solid, which was recrystallized from methanol to give 25 (6.1
g, 77%): yellow needles, mp 112-114 °C, lit.29 mp 110-112
°C.
9-Deu ter iom eth yla n th r a cen e (30). D2O (0.4 mL) was
added to a dark, emerald-green solution of 3 prepared at -78
°C under argon by addition of 1.8 M t-BuLi in pentane (0.28
mL, 0.50 mmol) to 25 (92 mg, 0.39 mmol) in Et2O (20 mL)
containing TMEDA (0.11 mL, 0.73 mmol). The mixture was
allowed to warm to room temperature, diluted with Et2O,
washed with saturated aqueous NH4Cl and saturated aqueous
NaHCO3, dried (MgSO4), and concentrated. Chromatography
of the residue on silica gel with hexane as eluent gave 30 (66
mg, 88%): mp 75-77 °C (hexane), with properties and mp
(79-81 °C) essentially identical to that of an authentic sample.
1H NMR (270 MHz) indicated 90% monodeuteration of the C-9
methyl group.
9,10-Dih ydr o-10-m eth yl-9-m eth ylen an th r acen e (31) an d
9-Eth yla n th r a cen e (32). A solution of 25 (101 mg, 0.42
mmol) in Et2O (30 mL) and TMEDA (0.15 mL, 1.0 mmol) at
-78 °C was treated with 1.9 M t-BuLi in pentane (0.32 mL,
0.61 mmol) at -78 °C. After 15 min, dimethyl sulfate (0.12
mL, 1.26 mmol) was added. The mixture, after warming to
room temperature, was washed with saturated aqueous NaH-
CO3, dried (MgSO4), and concentrated. Chromatography of the
residue with hexane as eluent gave a 1:1 mixture (63 mg, 73%)
of 31,31 1H NMR (270 MHz, CDCl3) 1.37 (d, J ) 7 Hz, 3H),
4.07 (q, J ) 7 Hz, 1H), 5.68 (s, 2H), 7.2-7.4 (m, 6H), 7.7 (m,
2H) and 32, 1H NMR (CDCl3) 1.45 (t, J ) 7.5 Hz, 3H), 3.64 (q,
J ) 7.5 Hz, 2H), 7.4-7.6 (m, 4H), 7.95-8.05 (m, 2H), and 8.2-
8.4 (m, 3H).
9,10-Dih yd r o-10-m eth ylen e-r-p h en yl-9-a n th r a cen em e-
th a n ol (33) a n d 2-(9-An th r yl)-1-p h en yleth a n ol (34). A 2.0
M solution of t-BuLi in pentane (0.30 mL, 0.60 mmol) was
added to 25 (107 mg, 0.45 mmol) and TMEDA (0.11 mL, 0.73
mmol) in Et2O (20 mL) at -78 °C. After 15 min, benzaldehyde
(0.095 mL, 0.93 mmol) was added to the dark emerald-green
solution. Within 1-2 min, the mixture became colorless and
was then allowed to warm to room temperature. The solution
was washed with saturated aqueous NH4Cl and saturated
aqueous NaHCO3, dried (MgSO4), and concentrated. Chroma-
tography of the residue on silica gel with hexane gave 17 (11
mg, 10%). Further elution with 20% ethyl acetate/hexane
yielded a 1:3 mixture (by 1H NMR) of 33 and 34 (110 mg, 82%).
A sample of 33 from the mixture was collected by prepara-
tive HPLC (µ porasil; 7.5% EtOAc/hexanes): 1H NMR (CDCl3,
270 MHz) 2.05 (d, J ) 3 Hz, 1H), 4.18 (d, J ) 7 Hz, 1H), 4.63
(dd, J ) 3 and 7 Hz, 1H), 5.57 (s, 1H), 5.59 (s, 1H), 6.7-6.9
Attem p ted Dep r oton a tion a n d Silyla tion or Deu ter a -
tion of 25. Reactions of LDA or LTMP (1 equiv) at -78 to 25
°C with 25 (1 equiv) in Et2O containing TMEDA (1 equiv) and
then addition of chlorotrimethylsilane (1 equiv) or CH3OD did
not yield 26 or R-deuterio-9-(thiomethoxymethyl)anthracene.
Complex products were obtained.
9-(Tr im eth ylsilylm eth yl)a n th r a cen e (28). Meth od A:
Rea ction of 25 w ith t-Bu Li a n d th en Ch lor otr im eth yl-
sila n e. t-BuLi (2.0 M) in pentane (14 mL, 28 mmol) was added
to 25 (6.1 g, 25 mmol) in Et2O (150 mL) at -78 °C under argon.
The dark blue-green solution that formed was then stirred for
40 min at -78 °C. Chlorotrimethylsilane (3.6 mL, 29 mmol)
was added, and the mixture was stirred for 1 h at -78 °C.
The clear yellow solution that resulted was washed with H2O
and saturated NaHCO3, dried (MgSO4), and concentrated.
Chromatography of the solid on silica gel with hexane as eluent
and recrystallization of the light yellow product (6.0 g, 91%)
from hexane yielded colorless crystals of 28: mp 66-68 °C,
lit.30 mp 59-60 °C; 1H NMR (CDCl3, CH2Cl2 as internal
standard) 0.02 (s, 9H), 3.18 (s, 2H), 7.4-7.6 (m, 4H), 7.9-8.3
(m, 5H); 13C NMR (CDCl3, 20 MHz) -0.4, 18.9, 123.7, 124.5,
124.7, 125.5, 129.1 (2C), 131.8, 134.2; UV (λ, ꢀ, hexane) 397
(8 500), 392 (shoulder, 5 300), 376 (9 000), 356 (5 300), 340
(2 600), 326 (shoulder, 1 200), 260 (177 000), 251 (81 000), 217
(14 400); exact mass calcd 264.1334, obsd 264.1344. Anal.
Calcd for C18H20Si: C, 81.75; H, 7.62. Found: C, 82.02; H, 7.57.
Meth od B. Rea ction of 25 w ith Lith iu m a n d Ch lor o-
tr im eth ylsila n e. Lithium metal (12 mg, 1.7 mmol) was added
to 25 (139 mg, 0.58 mmol) and chlorotrimethylsilane (0.30 mL,
2.38 mmol) in THF (4 mL). After the mixture had been stirred
for 20 h, all of the lithium had dissolved. The solution was
(31) (a) Prepared previously by reaction of 10-methyl-9-anthryl-
methyltrimethylammonium chloride with lithium aluminum hydride.
(b) Takagi, M.; Hirabe, T.; Nojima, M.; Kusabayashi, S. J . Chem. Soc.,
Perkin Trans. 1 1983, 1311. (c) J aeger, C. W.; Kornblum, N. J . Am.
Chem. Soc. 1972, 94, 2545.
(29) Kornblum, N.; Scott, A. J . Org. Chem. 1977, 42, 399.
(30) Tamao, K.; Sumitani, K.; Kiso, Y.; Zembayashi, M.; Fujioka,
A.; Kodama, S.-i.; Nakajima, I.; Minato, A.; Kumada, M. Bull. Chem.
Soc. J pn. 1976, 49, 1958.

4264 J . Org. Chem., Vol. 64, No. 12, 1999
Kendall et al.
1H), 7.1-7.4 (m, 5H). The properties of 40 correspond to those
previously reported.15
Meth od E. Rea ction of P h en yllith iu m a n d 39. Phenyl-
lithium (1.6 M in pentane, 3.1 mL, 4.96 mmol) was syringed
slowly into a solution of 39 (1.0 g, 5.08 mmol) in dry THF (10
mL). A slightly exothermic reaction ensued, and the cloudy
yellow mixture was stirred for 10 min. After addition of Et2O,
the mixture was washed with H2O and brine, dried (MgSO4),
concentrated, and chromatographed as in Method D to give
40 (0.44 g, 46%).15 The spectra of the product match those for
40 prepared by Method D.
F igu r e 1. Flash-vacuum pyrolysis apparatus.
(dd, 3H), 7.0-7.4 (m, 8H), 7.6-7.7 (m, 2H). Fractional crystal-
1-[Meth oxy(tr im eth ylsilyl)m eth yl]n a p h th a len e (41).
1-Bromonaphthalene (0.65 mL, 4.68 mmol) was added to
magnesium (0.12 g, 5.0 mmol) in THF (20 mL). The mixture
was refluxed for 15 min and then cooled, and 39 (0.98 g, 4.98
mmol) was added. The solution was stirred for 1 h, Et2O was
added, and the mixture was washed with H2O and brine, dried
(MgSO4), and concentrated. Column chromatography of the
residue on silica with petroleum ether as eluent yielded 41
(0.70 g, 61%): 1H NMR (CDCl3) 0.04 (s, 9H), 3.37 (s, 3H), 4.86
(s, 1H), 7.3-8.1 (m, 7H). The properties of 41 match those
previously reported.1,16b
5-[Meth oxy(tr im eth ylsilyl)m eth yl]a cen a p h th en e (42).
A mixture of magnesium (0.46 g, 20 mmol), 5-bromoacenaph-
thene (3.1 g, 13.3 mmol), and Et2O (25 mL) was refluxed for
20 min. During this period, 1,2-dibromoethane (0.5 mL, 5.8
mmol) in Et2O (10 mL) was added dropwise. The mixture was
refluxed for 10 min and cooled, and then 39 (2.88 g, 14.62
mmol) was added. The resulting mixture was stirred for 3 h,
during which a solid precipitated. Following addition of Et2O,
the solution was worked up as for 41. Column chromatography
on silica with petroleum ether and petroleum ether/toluene
as eluents gave 5-bromoacenaphthene (1.44 g) and then 42
(1.36 g, 38% conversion, 71% yield): light yellow solid, mp 99-
101 °C; 1H NMR (CDCl3) 0.03 (s, 9H), 3.32 (s, 3H), 3.41 (br s,
4H), 4.71 (s, 1H), 7.2-7.5 (m, 4H), 7.75 (d, 1H); 13C NMR
(CDCl3) -3.2, 29.9, 30.6, 59.2, 77.6, 118.9, 119.1, 119.9, 125.0,
127.0, 129.8, 132.9, 139.5, 143.8, 146.4; exact mass calcd
270.1440, obsd 270.1435. Anal. Calcd for C17H22OSi: C, 75.52;
H, 8.21. Found: C, 75.29; H, 8.17.
9-[Meth oxy(tr im eth ylsilyl)m eth yl]a n th r a cen e (7). n-
BuLi (8.6 mL, 1.4 M in pentane, 12 mmol) was slowly added
to a solution of 9-bromoanthracene (2.57 g, 10 mmol) in Et2O
(100 mL) at 0 °C. A yellow precipitate formed. After the
mixture stirred at room temperature for 30 min, 39 (2.6 g, 13
mmol) was added in one portion. The solution was then stirred
for 3 h, washed with H2O and brine, dried (MgSO4), and
absorbed on silica gel. Column chromatography on silica gel
using petroleum ether/toluene (4:1) as eluent yielded crude 7.
Recrystallization from hexane gave pure 7 (1.74 g, 59%): white
crystals, mp 92-94 °C; 1H NMR (CDCl3) 0.04 (s, 9H), 3.28 (s,
3H), 5.71 (s, 1H), 7.4-7.55 (m, 4H), 7.95-8.1 (m, 2H), 8.2-
8.3 (m, 1H), 8.36 (s, 1H), 9.0-9.1 (m, 1H); 13C NMR (CDCl3)
-1.7, 59.3, 77.2, 123.6, 124.4, 124.5, 125.1, 125.3, 126.6, 127.7,
128.8, 129.6, 129.9, 130.0, 131.4, 131.8, 132.7; exact mass calcd
294.1440, obsd 294.1443. Anal. Calcd for C19H22OSi: C, 77.50;
H, 7.53. Found: C, 77.60; H, 7.50.
1-[Meth oxy(tr im eth ylsilyl)m eth yl]a n th r a cen e (8). t-
BuLi (1.75 M) in pentane (9.0 mL, 16 mmol) was added slowly
to 45 (3.4 g, 15 mmol) and TMEDA (2.4 mL, 16 mmol) in Et2O
(200 mL) at -110 °C. Some of the 45 crystallized on the walls
of the reactor vessel but redissolved upon addition of the t-BuLi
solution. The resulting purple-blue mixture was stirred for 15
min at -110 to -105 °C, and then chlorotrimethylsilane (2.1
mL, 17 mmol) was added. After warming to room temperature,
the cloudy yellow solution was washed with H2O and saturated
aqueous NaHCO3 and then dried (MgSO4). Concentration of
the solution left a yellow syrup, which on chromatography on
silica gel with 20% benzene/hexane as eluent afforded 8 (3.0
g, 68%): a yellow syrup which slowly solidified, mp 59-61 °C
(methanol); 1H NMR (CDCl3, CH2Cl2 as internal standard) 0.04
(s, 9H), 3.40 (s, 3H), 4.95 (s, 1H), 7.4-7.6 (m, 4H), 7.9-8.2 (m,
3H), 8.5 (s, 1H), 8.7 (s, 1H); exact mass calcd 294.1440; obsd
294.1447. An analytical sample was prepared by distillation
lization of the reaction product from ethyl acetate/hexane gave
34 as yellow crystals: mp 114-115.5 °C; IR (CHCl3, cm-1
)
3590, 1210; 1H NMR (CDCl3, 270 MHz) 1.8 (d, 1H), 4.05 (d of
AB pattern, J ) 15, 9, and 4 Hz, 1H), 5.21 (ddd, J ) 9 and 4
Hz, 1H), 7.3-7.6 (m, 9H), 8.05 (d, 2H), 8.35 (d, 2H), 8.4 (s,
1H); 13C NMR (CDCl3, 70 MHz) 37.9, 75.6, 124.6, 124.9, 125.6,
125.8, 126.7, 127.6, 128.5, 129.2, 130.3, 130.6, 131.6, 144.3;
exact mass calcd 298.1358, obsd 298.1365.
r-D-9-(Tr im eth ylsilylm eth yl)a n th r a cen e (35). n-BuLi
(1.6 M) in hexane (0.65 mL, 1.0 mmol) was added to 28 (0.23
g, 0.87 mmol) and TMEDA (0.30 mL, 2.0 mmol) in THF (60
mL) at 0 °C under argon. After the dark emerald-green
solution had been stirred for 30 min at 0 °C, CH3OD was
added, and the colorless reaction mixture was washed with
H2O and saturated aqueous NaHCO3 and dried (MgSO4).
Removal of solvent gave 35 in 100% yield containing 70%
1
deuterium at its benzylic position as shown by H NMR and
MS analyses.
9-[Th iom eth oxy(tr im eth ylsilyl)m eth yl]an th r acen e (26).
TMEDA (0.32 mL, 2.1 mmol) and then 28 (0.5 g, 1.9 mmol)
were dissolved in THF (50 mL) under argon. Addition of
n-BuLi (1.6 M) in hexane (1.3 mL, 2.1 mmol) gave a dark green
solution. After 30 min, dimethyl disulfide (0.21 mL, 2.3 mmol)
was added. The clear yellow mixture was stirred for 1 h,
poured into Et2O, washed with H2O and saturated NaHCO3,
and dried (MgSO4). Removal of solvent left a yellow oil, which
on chromatography on silica gel using hexane as eluent yielded
(1) initial 28 (0.20 g, 40%), identical with an authentic sample,
and (2) 26 (0.34 g, 58%), mp 100-102 °C (hexane): 1H NMR
(CDCl3, CH2Cl2 as internal standard) 0.10 (s, 9H), 1.84 (s, 3H),
4.80 (s, 1H), 7.3-8.9 (m, 9H); 13C NMR (CDCl3, 20 MHz) -0.4,
17.3, 33.6, 123.5, 123.8, 124.5, 125.1, 125.8, 126.3, 127.4, 129.1,
129.7, 129.8, 131.0, 131.5, 132.1, 134.1; UV (λ, ꢀ, hexane) 396
(10 200), 390 (sh, 6 200), 375 (10 200), 356 (6 200), 340 (2 700),
325 (1 200), 259 (140 000), 252 (sh, 69 500), 276 (13 300); exact
mass calcd 310.1211, obsd 310.1220. Anal. Calcd for C19H22
-
SSi: C, 73.49; H, 7.14; S, 10.32. Found: C, 73.58; H, 7.06; S,
10.04. The yield of 26 based on the 28 that reacted was 97%.
P yr olysis of 15. Volatilization of 15 (0.37 g, 1.26 mmol) at
0.05-0.10 mm through a quartz tube (Figure 1) heated to
600-650 °C gave a black pyrolysate that was collected at -78
°C. Preparative TLC of the condensate on silica gel with 10:1
hexane/benzene yielded 14, 16, anthracene, and 38. The
products were identified by 1H NMR and comparison with
authentic samples. Pyrolysis of 15 as above does not yield 11.
P yr olysis of 26. Silane 26 (0.52 g, 1.67 mmol) was dropped
at 0.05-0.10 mm as a neat solid into a vertical quartz tube
packed with quartz chips and heated to 650 °C. Chromatog-
raphy of the pyrolysate on silica gel (hexane as eluent) afforded
a complex mixture of products as revealed by TLC and 1H
NMR. No evidence was found for 11 in the reaction products.
[Meth oxy(tr im eth ylsilyl)m eth yl]ben zen e (40). Meth od
D. Rea ction of P h en ylm a gn esiu m Br om id e a n d [Br om o-
(m eth oxy)m eth yl]tr im eth ylsila n e (39). A suspension of
magnesium (0.13 g, 5.35 mmol) in bromobenzene (0.53 mL,
5.08 mmol)/THF (20 mL) was refluxed for 1 h. After the
mixture had cooled, 3913,14 (1.0 g, 5.08 mmol) was added. The
resulting solution was stirred for 1 h and diluted with Et2O.
The mixture was washed with H2O and brine, dried (MgSO4),
and concentrated. Column chromatography of the concentrate
on silica gel with petroleum ether as the eluent yielded 40 (0.56
g, 57%): 1H NMR (CDCl3) -0.01 (s, 9H), 3.31 (s, 3H), 3.95 (s,

Synthesis and Chemistry of 1H-Cyclobuta[de]anthracene
J . Org. Chem., Vol. 64, No. 12, 1999 4265
at 105-107 °C/0.07 mm. Anal. Calcd for C19H22OSi: C, 77.50;
H, 7.53. Found: C, 77.49; H, 7.50.
Meth od ology for F la sh -Va cu u m P yr olyses of 7, 8, 11,
12, a n d 55. The material to be thermolyzed is placed in the
sample tube of the pyrolysis apparatus (Figure 1). The entire
system is placed under vacuum using initially a mechanical
Th er m a l Isom er iza tion of 11 to 46. Upon sublimation
from a sample tube at 50 °C, pure 11 (0.030 g, 0.16 mmol)
was pyrolyzed at 650 °C/10-3 mm. The condensate was passed
through silica with hexanes as eluent. The major fraction
collected (0.024 g, 80%) was shown by 1H NMR to be a 1:1
mixture of 11 and 46.
pump and then
a
mercury diffusion pump to lower the
9-Br om o-10-d eu ter ioa n th r a cen e (54). n-BuLi (1.4 M in
pentane, 20 mL, 28 mmol) was added to 9,10-dibromoan-
thracene (10 g, 29.76 mmol) suspended in Et2O (100 mL) at 0
°C. The mixture was stirred at room temperature for 30 min,
and an orange solid precipitated. Upon addition of D2O (2 mL,
100 mmol), the reaction mixture boiled gently. The solids were
filtered, and the filtrate was dried (MgSO4) and concentrated.
The crude product was suspended in petroleum ether and
filtered through a plug of silica. Fractional crystallization of
the crude solid from ethanol yielded 54 (6.68 g, 79%); mp 96-
99 °C, lit.20b mp 100-101 °C. Gas chromatography showed that
54 was 91% pure.
pressure. System pressure is measured by a McLeod vacuum
gauge downline from the furnace tube. The vacuum is not
monitored during pyrolysis.
An electric furnace (40 cm) is used to heat the quartz furnace
tube (45 cm × 2.4 cm i.d.) filled with quartz chips (35 cm
length). The temperature of the furnace is measured with a
digital thermometer, external to the quartz tube, in the center
of the furnace. Once the furnace tube has reached the proper
temperature and pressure, a heater is placed around the
sample tube. The heater is then warmed (75-110 °C), and the
sample slowly sublimes and/or distills into the furnace tube.
After pyrolysis is complete, the furnace and trap area are
isolated from the vacuum pumps. The vacuum is broken with
nitrogen, and the trap is removed. The pyrolysate is dissolved
in degassed benzene and purified.
P yr olysis of 7; P r ep a r a tion of 11 a n d 46. Decomposition
of 7 (0.2 g, 0.68 mmol) was effected at 550 °C/10-3 mm as
previously described. The pyrolysate was dissolved in degassed
benzene (5 mL), and silica gel was added. After concentration,
the sample was separated by MPLC using degassed hexanes
as eluents. Two fractions were collected: (1) 11 (0.056 g, 43%),
white crystals; mp 62-69 °C (dec), lit.1,2 mp 60-70 °C; 1H NMR
(CDCl3) 5.05 (s, 2H), 7.10 (d, J ) 5 Hz, 1H), 7.4-7.6 (m, 3H),
7.73 (d, 1H), 7.96 (dm, 1H), 8.12 (dm, 1H), 8.18 (s, 1H); 13C
NMR (CDCl3) 46.3, 114.8, 120.9, 121.1, 123.8, 124.4, 125.3,
126.9, 128.2, 131.1, 131.4, 136.7, 137.3, 141.5, 144.6; UV (λ, ꢀ,
hexane) 384 (5 200), 378 (3 700), 364 (5 300), 360 (5 000), 348
(4 500), 343 (shoulder, 3 900), 333 (3 000), 256 (204 000), 250
(shoulder, 126 000), 222 (15 400); exact mass calcd 190.0782,
obsd 190.0790 and (2) a yellow solid, which upon trituration
with methanol yielded white 46 (0.045 g, 35%); mp 72-74 °C,
lit.18 mp 74-75 °C; 1H NMR (CDCl3) 4.08 (d, J ) 1.8 Hz, 2H),
6.78 (t, J ) 1.8 Hz, 1H), 7.3-7.55 (m, 4H), 7.59 (dd, J ) 1.6
and 6.2 Hz, 1H), 7.83 (m,1H), 7.87 (m, 1H); 13C NMR (CDCl3)
46.0, 118.2, 122.1, 122.4, 124.7, 126.2, 126.5, 127.2, 128.2,
130.2, 134.8, 135.2, 142.6, 147.2, 154.9.
1H-Cyclobu ta [d e]a n th r a cen e: 2,4,7-Tr in itr oflu or en -9-
on e Com p lex (48). Freshly chromatographed (silica gel/
hexane) 11 (0.12 g, 0.60 mmol) in hot ethanol (5 mL) was added
to a boiling ethanol (20 mL)/benzene (1 mL) solution of 2,4,7-
trinitrofluoren-9-one (0.2 g, 0.60 mmol). A dark brown pre-
cipitate formed, which after cooling of the reaction mixture to
room temperature, filtration, and recrystallization from benzene/
ethanol, yielded 48 as dark red needles (0.13 g, 41%), mp 202-
204 °C; Anal. Calcd for C28H15N3O7: C, 66.53; H, 2.99; N, 8.32.
Found: C, 66.72; H, 3.06; N, 8.60.
R ed u ct ion of 46 t o 2,9b-Dih yd r ocyclop en t a flu or en e
(49). A mixture of 46 (0.083 g, 0.44 mmol), lithium aluminum
hydride (0.020 g, 0.53 mmol), and Et2O (15 mL) was refluxed
for 15 min and then cooled to 0 °C. After dropwise addition of
EtOAc (1 mL), the solution was washed with 10% aqueous HCl
and brine, dried (MgSO4), and concentrated. Column chroma-
tography on silica gel with petroleum ether as eluent yielded
49 (∼0.002 g, ∼2%): 1H NMR (CDCl3) 1.80 (ddd, J ) 7.0, 11.0,
and 11.3 Hz, 1H), 2.79 (m, 1H), 2.96 (dd, J ) 7.1 and 15.0 Hz,
1H), 3.57 (m, 1H), 4.24 (dd, J ) 6.8 and 11.3 Hz, 1H), 7.0-
7.55 (m, 6H), 7.7 (m, 1H); M+ ) 192 amu.
9-Deu ter io-10-[m eth oxy(tr im eth ylsilyl)m eth yl]a n th r a -
cen e (55). n-BuLi (20 mL, 1.4 M in pentane, 28.0 mmol) was
added to 54 (6.68 g, 91%) in Et2O (200 mL) at 0 °C. The
resulting solution was stirred at ∼25 °C for 30 min, and 39
(5.52 g, 28.0 mmol) was added. Reaction proceeded rapidly,
and the dark gold solution was stirred for several minutes,
washed with H2O and brine, and dried (MgSO4). Silica gel was
added for sample adsorption. Column chromatography on silica
gel was accomplished using petroleum ether, 10:1 petroleum
ether/toluene, and 4:1 petroleum ether/toluene. Product isola-
tion followed by recrystallization from hexanes yielded 55 (4.56
g, 66%): mp 92-94 °C; 1H NMR (CDCl3) 0.07 (s, 9H), 3.30 (s,
3H), 5.71 (s, 1H), 7.51 (m, 4H), 8.04 (m, 2H), 8.28 (m, 1H),
1
8.38 (s, 0.06H), 9.05 (m, 1H). H NMR reveals that 55 is 94%
deuterated at C-9.
P yr olysis of 55 to 56, 57 a n d 58, 59. Pyrolysis of 55 (200
mg, 0.68 mmol) was effected at 650 °C/10-3 mm as for 7. The
pyrolysate was purified by MPLC using degassed hexanes as
eluent. The following fractions were collected: (1) 56 and 57
1
(0.03 g, 23%); mp 60 °C (dec); H NMR (CDCl3) 5.05 (s with
shoulder, 1.60H), 7.08 (d, 1H), 7.3-7.6 (m, 3H), 7.72 (d, 1H),
7.95 (dm, 1H), 8.11 (dm, 1H), 8.17 (s, 0.38H) and (2) 58 and
59 (0.085 g, 66%); mp 65-69 °C; 1H NMR (CDCl3) 4.08 (s with
shoulder, 1.44H), 6.79 (d with shoulders, 0.67H), 7.3-7.5 (m,
4H), 7.60 (dd, J ) 1.6 and 6.2 Hz, 1H), 7.83 (m, 1H), 7.87 (m,
1H).
P yr olysis of 8 to 11 a n d 46. Pyrolysis of 8 (50 mg, 0.17
mmol) was effected at 560 °C/10-3 mm as previously described
for 7. The pyrolysate was purified by MPLC using degassed
hexanes as eluent. The major reaction product, collected as a
1
single fraction and analyzed by H NMR, was a mixture of 11
(13 mg, 41%) and 46 (7 mg, 22%). At 660 °C/10-3 mm,
decomposition of 8 yielded 11 (15%) and 46 (57%). Yields of
11 ranging from 49% to 52% were obtained upon distilling 8
(up to 1 g) into a vertical quartz-packed pyrolysis unit at 560-
570 °C/0.02-0.07 mm.
9,10-Dib r om o-9,10-d ih yd r o-1H -cyclob u t a [d e]a n t h r a -
cen e (94). Bromine (0.096 g, 0.6 mmol) in CCl4 (2 mL) was
added dropwise to 11 (0.076 g, 0.4 mmol) in CCl4 (5 mL). The
solution was stirred for 5 min and concentrated to a yellow
solid. Trituration of the solid with benzene afforded 94 (0.087
g, 62% stereochemistry unknown): white solid, mp 150 °C
(dec); 1H NMR (CDCl3) 4.03 (d, J ) 13.9 Hz, 1H), 4.50 (d, J )
13.9 Hz, 1H), 5.98 (s, 1H), 7.00 (dd, 1H), 7.2-7.4 (m, 5H), 7.63
(m, 1H); 13C NMR (CDCl3) 42.3, 52.1, 55.0, 124.2, 124.3, 124.6,
128.2, 128.4, 128.7, 130.0, 130.1, 132.2, 137.2, 141.2, 142.1;
exact mass calcd 347.9149, obsd 347.9129. The instability of
94 precludes its elemental analysis.
10-Br om o-1H-cyclobu ta [d e]a n th r a cen e (95). A solution
of 94 in benzene (3 mL) was refluxed for 20 min. Concentration
and purification by MPLC yielded 95 (19%): yellow crystals,
mp 94-96 °C; 1H NMR (CDCl3) 5.01 (s, 2H), 7.09 (d, 1H), 7.5-
7.6 (m, 3H), 7.74 (d, 1H), 7.92 (m, 1H), 8.60 (m, 1H); 13C NMR
(CDCl3) 46.1, 114.9, 115.4, 120.9, 124.3, 125.1, 125.5, 125.6,
126.1, 127.1, 129.2, 132.3, 133.7, 141.0, 143.7; exact mass calcd
267.9888, obsd 267.9850. The product is too unstable for
combustion analysis.
P yr olysis of Sp ir o[in d a zol-3,1-in d en e] (50) to 46. In-
dene 5018 was sublimed into the furnace tube (Figure 1) at
265 °C/0.3 mm. Pyrolysis was incomplete after 2 h. The 1H
and 13C NMR spectra of the product (46, no purification)
exactly match those of 46 previously prepared from 11.
P yr olysis of 5-(9-An th r yl)tetr a zole (12). Flash-vacuum
pyrolysis of 122 (0.050 g, 0.2 mmol) at 660 °C/10-3 mm yielded
3 products. By far, the major product was 13 (∼90%). The 2
other products (∼10%) were 11 and 46 in a 1:10 ratio as
identified by their GC retention times and their MS (M+
190 amu).
)

4266 J . Org. Chem., Vol. 64, No. 12, 1999
Kendall et al.
ylene)-9-anthryl phenyl ketone (21c), 9,10-dihydro-10-(meth-
oxymethylene)-R-methyl-9-anthracenemethanol (21d ), 9,10-
dihydro-10-(methoxymethylene)R-phenyl-9-anthracenemeth-
anol (21e), 9,10-dihydro-10-(methoxymethylene)-R,R-dimethyl-
9-anthracenemethanol (21f), and 1-(methoxymethyl)anthracene
(45) and NMR spectra for 7, 11, 42, 46, 55-58, 94, and 95.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Ack n ow led gm en t. This research was supported by
the National Science Foundation, the National Insti-
tutes of Health, the U.S. Department of Education, the
Procter and Gamble Company, The Ohio State Univer-
sity, and the state of Ohio.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and references for preparing anthracene-1-carboxylic
acid, 1-anthracenemethanol, 9,10-dihydro-10-(methoxymeth-
J O981105B