Carbenes in polycyclic systems: Generation and fate of potential adamantane-1,3-dicarbenes

Article abstract of DOI:10.1002/poc.1319

Potential formation and reactions of adamantane-1,3-dicarbenes 1-3 generated under different conditions and from different precursors, such as sodium salt of adamantane-1,3-dicarbaldehyde ditosylhydrazone (4a), sodium salt of 1,3-diacetyladamantane ditosylhydrazone (5a), sodium salt of 1,3-dibenzoyladamantane ditosylhydrazone (6a), and 1,3-bis(diazobenzyl) adamantane (7) are reported. Carbene species generated thermally from 4a yielded bishomoa-damantane (15), as a final product, via intramolecular insertion into adjacent C - C bond and formation of putative anti-Bredt olefin species, followed by hydrogen abstraction. Pyrolysis of the same sodium salt 4a in the presence of hydrogen donor n-Bu₃SnH afforded 1,3-dimethyladamantane (17). Thermal decomposition of sodium salt 5a afforded 1,3-divinyladamantane (14). However, thermal decomposition of sodium salt 6a and diazo-precursor 7 gave benzonitrile as a sole identified product. On the contrary, photolysis of 7 afforded dimeric azine 21. Finally, the synthetic pathways of novel tosylhydrazone derivatives 4, 5, 6 and their corresponding sodium salts, as well as bis-diazocompound 7 are described. Copyright

Full text of DOI:10.1002/poc.1319

Research Article
Received: 29 June 2007,
Revised: 6 December 2007,
Accepted: 6 December 2007,
Published online in Wiley InterScience: 26 February 2008
(www.interscience.wiley.com) DOI 10.1002/poc.1319
Carbenes in polycyclic systems:
generation and fate of potential
adamantane-1,3-dicarbenes
a
a
a
´
ˇ
´
´
Lada Klaic , Marija Aleskovic , Jelena Veljkovic
a
*
´
and Kata Mlinaric-Majerski
Potential formation and reactions of adamantane-1,3-dicarbenes 1–3 generated under different conditions and from
different precursors, such as sodium salt of adamantane-1,3-dicarbaldehyde ditosylhydrazone (4a), sodium salt of
1,3-diacetyladamantane ditosylhydrazone (5a), sodium salt of 1,3-dibenzoyladamantane ditosylhydrazone (6a), and
1,3-bis(diazobenzyl)adamantane (7) are reported. Carbene species generated thermally from 4a yielded bishomoa-
damantane (15), as a final product, via intramolecular insertion into adjacent C—C bond and formation of putative
anti-Bredt olefin species, followed by hydrogen abstraction. Pyrolysis of the same sodium salt 4a in the presence of
hydrogen donor n-Bu3SnH afforded 1,3-dimethyladamantane (17). Thermal decomposition of sodium salt 5a afforded
1,3-divinyladamantane (14). However, thermal decomposition of sodium salt 6a and diazo-precursor 7 gave
benzonitrile as a sole identified product. On the contrary, photolysis of 7 afforded dimeric azine 21. Finally, the
synthetic pathways of novel tosylhydrazone derivatives 4, 5, 6 and their corresponding sodium salts, as well as
bis-diazocompound 7 are described. Copyright ß 2008 John Wiley & Sons, Ltd.
Supplementary electronic material for this paper is available in Wiley InterScience at http://www.mrw.interscience.wiley.com/
suppmat/0894-3230/suppmat/
Keywords: polycyclic compounds; adamantane; carbenes; dicarbenes; azines
hydrazone (6a), and 1,3-bis(diazobenzyl)adamantane (7)]
in vacuo, or by photolysis of bis-diazocompound 7 in benzene
solution.
INTRODUCTION
Carbene-intermediates have been the subject of extensive experi-
mental and theoretical investigation.[1–5] Carbenes, which are
readily generated by decomposition of corresponding diazo-
compounds, are versatile synthetic intermediates in organic
chemistry. For example, intramolecular carbene cycloaddition to
the olefinic bond has been used as a successful strategy for
preparation of small ring propellanes.[6–13] Likewise, the carbene
route has been employed for generation of bridgehead double
bonds as in anti-Bredt olefins.[14] Bridgehead double bonds
are readily accommodated in larger ring systems, but in the small
rings they are unstable.[15] The bridgehead-olefin carbene
rearrangement has also been documented.[16–22] Recently,
we reported the evidence for the formation of mono- and
dialkylidene species.[23,24,25] The reactivity profile of carbene and
dicarbene species is highly dependent on the carbene structure.
In order to gain insight into the chemical reactivity of alkyl-
dicarbene species, we studied the generation and reactions of
potential adamantane-1,3-dicarbenes 1–3. By introduction of
two potential carbene centers onto the adamantane framework,
we were able to study both the possibility of simultaneous ring-
expansion to its higher homologue and the introduction of two
double bonds into bridgehead positions of the parent system.
Carbenes were generated via pyrolysis of corresponding
precursors [i.e., dry sodium salt of adamantane-1,3-
dicarbaldehyde p-toluenesulfonylhydrazone (4a), sodium salt
of 1,3-diacetyladamantane p-toluenesulfonylhydrazone (5a),
sodium salt of 1,3-dibenzoyladamantane p-toluenesulfonyl-
RESULTS AND DISCUSSION
The routes to prepare the carbene precursors 4a, 5a, 6a, and 7 are
shown in Scheme 1. The synthesis started from 1,3-dibromo-
adamantane via corresponding diacid 8 and dialdehyde 10 or
diketones 11 and 12. Hitherto unknown dicarbonyl compounds
10, 11, and 12 were converted in a high yield to new
corresponding tosylhydrazones 4, 5, and 6. Subsequent conver-
sion to their tosylhydrazone sodium salts 4a, 5a, and 6a, was
achieved using our previously developed procedure.[11,12] Novel
bis-diazo precursor 7 was prepared in 75% overall yield via
reaction of 12 with hydrazine monohydrate followed by
[26]
oxidation of dihydrazone 13 with BaMnO4
of CaO.
in the presence
Flash vacuum pyrolysis of dry Na-salts 4a and 5a were carried
out at 2108C and 1 ꢀ 10ꢁ3 mm Hg. The products were collected
ˇ ´
Department of Organic Chemistry and Biochemistry, Ruper Boskovic Institute,
*
ˇ
Bijenicka cesta 54, P.O. Box 180, 10002 Zagreb, Croatia.
E-mail: majerski@irb.hr
´
ˇ
´
´
´
a
L. Klaic, M. Aleskovic, J. Veljkovic, K. Mlinaric-Majerski
ˇ
´
Department of Organic Chemistry and Biochemistry, Ruper Boskovic Institute,
ˇ
Bijenicka cesta 54, 10002 Zagreb, Croatia
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L. KLAIC ET AL.
Scheme 1.
into a trap cooled by liquid nitrogen, dissolved in C6D6 and
analyzed by NMR and GC-MS. Pyrolysis of 5a (Scheme 2) afforded
1,3-divinyladamantane (14) as a sole product in 42% yield. Olefin
14 forms as a product of 1,2-CH insertion which is favored to
C—C insertion when both reactions are possible.[2,4,5]
achieve stabilization through hydrogen abstraction leading to
the formation of saturated bishomoadamantane product. Given
that bishomoadamantane 15 is a stable product of high
symmetry and a product of migration into a shorter bridge, it
seemed likely that 15 would be the main product. Analysis of the
Therefore we presumed, that by having the carbon–hydrogen
bonds at a larger distance from the carbene center, as it is in
carbene species 1, the carbon–carbon insertion reaction will be
preferred, enabling us to test the generation of anti-Bredt olefin.
However, a problem that could arise here stems from the fact that
1 has several bonds for ring-expansion. Carbene insertion into
different C—C bonds would lead to the formation of several
related bridgehead alkenes (Scheme 3).
The 1H NMR spectrum of the product obtained by pyrolysis of
Na-salt 4a was complex, but all signals were in the aliphatic
region showing no olefinic protons. We hypothesized that
two carbene centers subsequently underwent carbene-
rearrangements which are known to take place through exclusive
migration of the shorter bridges.[27,28] Hypothesized highly
strained and reactive anti-Bredt intermediates would tend to
crude product by GC-MS exhibited a single peak with
mass Mþ(164) and some polymers which appeared at high
temperature. To test our hypothesis, an authentic sample of
bishomoadamantane 15[29] was prepared and compared with
the product obtained by pyrolysis of 4a. MS fragmentation
patterns as well as GC-retention time (compared by two different
capillary columns, HP-5 and DB-210) proved identical with the
data obtained for the authentic sample of 15 prepared from
2,6-adamantanedione. When Na-salt 4a was subjected to the
pyrolysis with simultaneous introduction of n-Bu3SnH into the
system, 1,3-dimethyladamantane (17) was obtained as the sole
hydrocarbon product. The formation of bishomoadamantane 15
and 1,3-dimethyladamantane (17) entails the generation of either
dicarbene species 1 or sequential formation of monocarbene
species as shown in Scheme 3.
Scheme 2.
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CARBENES IN POLYCYCLIC SYSTEMS
Scheme 3.
To achieve stabilization of putative bridgehead olefin through
conjugative effect, phenyl-substituted precursors 6a and 7 were
prepared. The introduction of substituents to bridgehead olefins
is believed to alter their stability and reactivity. Schleyer[15] and
Jones[30] proposed that replacement of the vinyl hydrogen by
bulky groups with steric protection or substituents which provide
electronic stabilization could aid the formation of observable
species. In that regard, Eguchi et al.[31] reported conjugative
stabilization of the double bond at the bridgehead of homo-
adamantene through the 1,2-C shift of 1-adamantylcarbene
intermediate generated from (1-adamantyl)diazophenyl-
methane. However, flash vacuum pyrolysis of Na-salt 6a, at
2108C under reduced pressure (ꢂ1 ꢀ 10ꢁ3 mm Hg) afforded
benzonitrile (18) as the only isolated product (Scheme 4).
To exclude the fragmentation of Na-salt 6a prior to the
formation of diazo-precursor 7, we prepared pure 7 by a direct
method (refer to Experimental section for details) and carried out
the vacuum pyrolysis at 6008C (Scheme 5).
Scheme 4.
Scheme 5.
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L. KLAIC ET AL.
A benzene solution of 7 was injected into a quartz tube
inserted into an oven preheated to 6008C. The quartz tube was
connected to the vacuum line (1 ꢀ 10ꢁ1 mm Hg) and product
was collected in a trap cooled by liquid nitrogen. Again, analysis
of the product showed 18 to be the main product apart from
some polymers and traces of unidentified material.
EXPERIMENTAL
General
The purity of all compounds was determined by GC and/or
13C NMR spectral analysis. GC analyses were performed using a
Varian 3380 gas chromatograph equipped with either a DB-210 or
a DB-1701 capillary column. GC-MS analyses were performed on a
HP 5890-II, MSD 5970 equipped with HP-5 column (25 m ꢀ
0.2 mm), operated over temperature range 60–2508C. 1H and
13C NMR spectra were recorded on 300 MHz and 600 MHz Brucker
spectrometers using TMS or CDCl3 as the internal standard. IR
spectra were recorded on a Perkin Elmer M-297 and ABB Bomem
M-102 spectrophotometers. UV-spectra were recorded on 100
Bio UV/VIS spectrophotometers. Melting points were determined
Based on these results, we propose the formation of
monocarbene intermediate species 19 which undergoes intra-
molecular gas phase reaction with the second diazo-group to
yield cyclic azine 20 as shown in Scheme 5. Subsequent
homolytic cleavage of azine 20 at higher temperature affords
benzonitrile (18) and adamantane-diradical which polymerizes.
To generate carbene species 3 photochemically, a benzene
solution of 7 was irradiated with a high-pressure Hg-lamp
through a Pyrex filter until the red color of the diazo-compound
completely disappeared. The product obtained in 88% yield was
on
a Koffler apparatus or Electrothermal 9100 and are
uncorrected. Elemental microanalyses were performed on Perkin
Elmer Series II CHNS/O Analyzer 2400. Adamantane-1,3-
dicarboxylic acid[34] and the dimethyl ester of adamantane-1,3-
dicarboxylic acid[35] were prepared according to the literature
procedures. Unless stated otherwise, reagent grade solvents
were used.
1
identified as azine-dimer 21 (Scheme 5). The H and 13C NMR
spectra of the product were identical to the spectra of the azine
21 obtained by the coupling reaction of the dihydrazone 13 and
diketone 12 performed in refluxing xylene and catalyzed with
p-toluenesulfonic acid.[32] Since the product was stable toward
thermolysis in solution at 1408C, a control experiment under
conditions of flash vacuum pyrolysis was carried out. Likewise,
when azine-dimer 21 was subjected to the pyrolysis at 2108C and
0.5 ꢀ 10ꢁ3 mm Hg, no benzonitrile was obtained, and 21 was
recovered quantitatively. However, pyrolysis of azine 21 at 6008C
and 1 ꢀ 10ꢁ1 mm Hg led to homolytic cleavage whereupon
benzonitrile was obtained as the sole volatile product.
1,3-bis(hydroxymethyl)adamantane (9)
To a suspension of LiAlH4 (1.56 g, 41.8 mmol) in dry THF (200 ml)
was added dropwise a solution of dimethyl ester of adamanta-
ne-1,3-dicarboxylic acid (2.63 g, 10.5 mmol) in dry THF (150 ml)
and the mixture was heated to reflux. After 70 h of reflux, the
reaction mixture was cooled down to rt and diluted with THF
(70 ml). The excess of LiAlH4 was quenched with water (13 ml),
THF solution was decanted off and the white solid was washed
with THF (2 ꢀ 30 ml). Organic extracts were dried over anhydrous
MgSO4, filtered, and evaporated to give 9 as a colorless crystalline
CONCLUSIONS
The potential generation of two carbene centers attached to the
1,3-bridgehead position of an adamantane system such as 1 has
been investigated. The results can be interpreted such that, in the
gas-phase and absence of trapping reagent, pyrolysis of sodium
salt 4a generates potential dicarbene 1, which is forced to
undergo insertion reaction into adjacent C—C bonds of
adamantane framework leading to generation of an anti-Bredt
olefin, 1,8-bishomoadamantanediene. Stabilization by hydrogen
abstraction leads to the formation of bishomoadamantane 15, as
confirmed by comparison with authentic sample. On the
contrary, when sodium salt 4a was subjected to the pyrolysis
in the presence of trapping reagent (n-Bu3SnH) 1,3-dimethyl-
adamantane (17) was formed possibly as a product of hydrogen
abstraction by adamantane-1,3-dicarbene (1). Pyrolysis of sodium
salt 5a produced 1,3-divinyladamantane (14)[33] in 41.3% yield,
possibly as the product formed by 1,2-H shift reaction from
adamantane dicarbene 2. However, the consecutive reaction and
formation of monocarbene species like 1a, 1b and 1c or 2a and
2b cannot be excluded. All of the products can be rationalized by
sequential reactions of monocarbenes as well as by reactions of
dicarbenes. Generation of dicarbene species 3 proved to be
unsuccessful both by pyrolysis of sodium salt 6a and
corresponding 1,3-bis(diazobenzyl)adamantane (7) or by pho-
tolysis of 7. The formed products, azines 20 and 21, suggest that
gas-phase pyrolysis of 6a and 7 proceed through the formation of
monocarbene intermediate 19, which then reacts intramolecu-
larly with the second diazo-group to yield cyclic azine 20. On the
other hand, photolysis of bis-diazo precursor 7 affords mono-
carbene 19 which in solution reacts intermolecularly furnishing
azine-dimer 21 as the only product.
solid (1.776 g, 86.7%): mp 1818C (lit.[35] 180.5–182.08C); H NMR
1
(CD3OD) d 1.24 (s, 2H), 1.40–1.55 (m, 8H), 1.66 (br.s, 2H), 2.06 (br.s,
2H), 3.14 (s, 4H); 13C NMR (CD3OD) d 30.0 (d, 2C), 36.2 (t, 1C), 38.0 (t,
1C), 40.1 (t, 4C), 42.0 (s, 2C), 74.0 (t, 2C); IR (KBr) ~n 3264 (s), 2898 (s),
2844 (s), 1452 (m), 1045 (s), 1026 (m) cmꢁ1
.
Adamantane-1,3-dicarbaldehyde (10)
To a suspension of pyridinium chlorochromate (PCC; 0.850 g,
4.0 mmol) in CH2Cl2 (ꢂ10 ml) was added a suspension of 9
(0.196 g, 1.0 mmol) in dry THF (ꢂ5 ml). The reaction mixture was
stirred at rt for 2.5 h, whereupon it was diluted with dry diethyl
ether (ꢂ50 ml) and filtered through a plug of florisil. The filtrate
was evaporated in vacuo to afford 10 (0.183 g, 95%). According to
GC analysis (DB 210, 1508C) product 10 had a purity of over 95%.
Since dialdehyde 10 is unstable and decomposes on silica gel, it
1
was used in the next step without further purification. H NMR
(CDCl3) d 1.60–1.84 (m, 12H), 2.29 (br.s, 2H), 9.39 (s, 2H); 13C NMR
(CDCl3) d 26.6 (d, 2C), 34.2 (t, 1C), 35.0 (t, 4C), 35.3 (t, 1C), 44.5 (s,
2C), 204.4 (d, 2C); IR (KBr) ~n 2910 (s), 2850 (m), 2800 (w), 2700 (w),
1720 (s), 1450 (m) cmꢁ1
.
Adamantane-1,3-dicarbaldehyde ditosylhydrazone (4)
To a solution of 10 (0.317 g, 1.7 mmol) in abs. MeOH (8 ml) was
added p-toluenesulfonylhydrazine (0.672 g, 3.3 mmol) in small
portions and the reaction mixture was stirred at rt for 2 days. The
progress of the reaction was monitored by TLC (2% MeOH
in CH2Cl2). After the reaction was completed, water (20 ml) was
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CARBENES IN POLYCYCLIC SYSTEMS
added and the resulting white suspension was extracted with
diethyl ether (3 ꢀ 20 ml). The combined organic extracts were
dried over anhydrous MgSO4, filtered and concentrated in vacuo
to give crude 4 (1.108 g). Further purification by column
chromatography on silica gel (0–3% MeOH in CH2Cl2) yielded
4 (0.824 g, 92%) as a white microcrystalline solid: mp 163–1658C;
1H NMR (CD3OD) d 1.40–1.75 (m, 14H), 2.12 (s, 2H), 2.50 (s, 6H),
7.03 (s, 2H), 7.46 (d, 4H, J ¼ 7.6 Hz), 7.83 (d, 4H, J ¼ 7.6 Hz); 13C NMR
(CD3OD) d 21.8 (2C), 29.4 (2C), 36.8 (1C), 38.5 (1C), 40.2 (4C), 42.7
(2C), 129.2 (4C), 130.8 (4C), 137.5 (2C), 145.5 (2C), 159.5 (2C); IR
(KBr) ~n 3160 (s), 2900 (s), 2840 (s), 1620 (w), 1590 (m), 1480 (w),
1430 (s), 1350 (s), 1310 (s), 1150 (s) cmꢁ1; Anal. Calcd.
for C26H32N4S2O4 (528.70): C, 59.07; H, 6.10; N, 10.60. Found: C,
59.06; H, 6.04; N, 10.80.
residue precipitated out of the reaction mixture. The residue was
collected by filtration, washed with MeOH and dry diethyl ether
to yield 5 (0.345 g, 100%) as a white powder: mp 217–2198C;
1H NMR (CD3OD) d 1.28 (s, 2H), 1.45–1.73 (m, 18 H, with strongly
expressed singlet at 1.72 (CH3)), 2.06 (br.s, 2H), 2.41 (s, 6H), 7.35 (d,
4H, J ¼ 8.3 Hz), 7.81 (d, 4H, J ¼ 8.3 Hz); 13C NMR (CD3OD) d 11.9 (d,
2C), 21.8 (q, 2C), 30.0 (q, 2C), 37.1 (t, 1C), 40.1 (t, 4C), 42.6 (t, 1C),
42.7 (s, 2C), 129.7 (d, 4C), 130.5 (d, 4C), 137.6 (s, 2C), 145.3 (s, 2C),
~
165.6 (s, 2C); IR (KBr) n 3230 (s), 2920 (m), 2850 (w), 1600 (w), 1340
(s), 1160 (s) cmꢁ1; Anal. Calcd. for C28H36N4S2O4 (556.75): C, 60.41;
H, 6.52; N, 10.06. Found: C, 60.52; H, 6.53; N, 10.23.
Preparation and pyrolysis of sodium salt of
1,3-diacetyladamantane ditosylhydrazone (5a)
To a suspension of NaH (50% dispersion in mineral oil; 0.112 g,
2.3 mmol) in dry THF (4 ml) heated to 608C was added 5 (0.493 g,
0.9 mmol) in small portions. After 2 h at 608C, the reaction mixture
was cooled to rt and the solvent was removed in vacuo. The
product was additionally dried under high vacuum
(ꢂ1 ꢀ 10ꢁ3 mm Hg) for 2 h and the resulting salt was used in
the pyrolysis without further purification. The dry 5a (1 mmol)
was heated at 2108C and 1 ꢀ 10ꢁ3 mm Hg for 20 min, during
which, salt changed its color from white to pink. The volatile
product was collected in a liquid nitrogen cooled trap, and the
product was dissolved in C6D6 under a nitrogen atmosphere.
Analysis of the crude product by GC (DB 210, 1008C, 1 min; 108C/
min; 2008C) showed the presence of one product with 90% purity.
Purification of the crude product by chromatography on
neutral Al2O3 (activity 1) with pentane as the eluent afforded
1,3-divinyladamantane (14) as a colorless oil (0.069 g, 41.3%).
Preparation and pyrolysis of sodium salt of
adamantane-1,3-dicarbaldehyde ditosylhydrazone (4a)
To a solution of 4 (0.351 g, 0.664 mmol) in dry THF (3.5 ml) was
added NaH (50% dispersion in mineral oil, 0.063 g, 1.31 mmol) in
small portions over 2 h at rt. The solvent was removed under
reduced pressure, and the crude product was additionally dried
under high vacuum (ꢂ1 ꢀ 10ꢁ3 mm Hg) for several hours. The dry
4a (1.0 mmol) was pyrolyzed at 2108C and 1 ꢀ 10ꢁ3 mm Hg for
20 min. The volatile product was collected into a trap cooled by
liquid nitrogen and subsequently dissolved in C6D6 (0.5 ml) under
a nitrogen atmosphere. The crude product was analyzed by
GC-MS (as in Supplementary data).
1,3-Diacetyladamantane (11)
Adamantane-1,3-dicarbaldehyde (0.231 g, 1.2 mmol) was dis-
solved in dry THF (10 ml) under a nitrogen atmosphere and
cooled to 08C. To the resulting solution was added dropwise 2 M
solution of CH3Li in hexane (1.2 ml, 2.4 mmol). The reaction
mixture was stirred for 48 h at rt, quenched with saturated
aqueous NH4Cl (15 ml) and water (5 ml) and extracted with
diethyl ether (4 ꢀ 30 ml). The combined organic extracts were
dried over anhydrous MgSO4, filtered, and concentrated in vacuo
to afford 0.183 g (65%) of the crude product. The crude product
was dissolved in CH2Cl2 (5 ml), and added in small portions to a
solution of pyridinium chlorochromate (0.707 g, 3.3 mmol)
in CH2Cl2 (5 ml). The reaction mixture was stirred at rt for 2 h
and then was diluted with dry diethyl ether (ꢂ50 ml), and filtered
through a small plug of florisil. The organic filtrate was
concentrated in vacuo to give 0.180 g of the mixture of products
which, according to GC (DB-210, 1508C) contained 60% of
diacetyladamantane. Purification by column chromatography on
silica gel (10–30% diethyl ether in pentane) yielded 11 (0.137 g,
51.8%) as a white solid. Analytical sample of 11 was obtained by
sublimation: mp 528C; 1H NMR (CDCl3) d 1.66–1.85 (m, 12H), 2.11
(s, 6H), 2.18–2.23 (br.s, 2H); 13C NMR (CDCl3) d 24.3 (d, 2C), 27.7 (q,
2C), 35.3 (t, 1C), 37.3 (t, 4C), 38.4 (t, 1C), 46.5 (s, 2C), 212.8 (s, 2C); IR
Spectral data for 14 1H NMR, 13C NMR and IR, were identical with
[33]
published data
(as in Supplementary Data).
1,3-Dibenzoyladamantane (12)
A solution of 8 (1.5 g, 6.7 mmol) in SOCl2 (15 ml) was refluxed
overnight. Evaporation of excess of SOCl2 afforded adamanta-
ne-1,3-dicarboxylic acid dichloride as a white solid (1.726 g, 99%),
which was characterized by IR spectroscopy: IR (KBr) ~n 2915 (m),
2863 (m), 1794 (s), 1455 (s), 1446 (s), 1061 (s), 1040 (s), 943 (s), 833
(s), 670 (s) cmꢁ1. The compound was used in the next step
without further purification due to its instability.
To the magnesium turnings (0.488 g, 20.1 mmol) in dry diethyl
ether (7 ml) was added dropwise a solution of bromobenzene
(2.1 ml, 20.1 mmol) in dry diethyl ether (10 ml) under a nitrogen
atmosphere, and the reaction mixture was stirred at rt. The
reaction mixture changed color from turbid white to brown. After
addition of the reagent had been completed, the resulting
mixture was refluxed until the magnesium turnings disappeared.
Reaction mixture was cooled in an ice bath and to the suspension
was added CdCl2 (1.842 g, 10 mmol) in several portions within
10 min. After the addition of CdCl2 had been completed, mixture
was heated to reflux for 1.5 h. The mixture was cooled down to rt
and the solvent was removed under vacuum. The residue was
suspended in dry benzene (15 ml), a solution of adamantane-
1,3-dicarboxylic acid dichloride (1.73 g, 6.6 mmol) in dry benzene
(15 ml) was added dropwise, and the reaction mixture was
refluxed overnight. The reaction mixture was poured on the ice
and subsequently was added 10% sulfuric acid (20 ml). Organic
layer was separated and the aqueous layer was extracted
with diethyl ether (4 ꢀ 25 ml). The combined organic extracts
~
(KBr) n 2931 (w), 2905 (w), 2851 (w), 1707 (s), 1450 (m), 1343 (m),
1252 (m), 1191 (s), 596 (s) cmꢁ1; Anal. Calcd. for C14H20O2 (220.31):
C, 76.33; H, 9.15. Found: C, 76.47; H, 9.11.
1,3-Diacetyladamantane ditosylhydrazone (5)
To a solution of 11 (0.137 g, 0.6 mmol) in abs. MeOH (2.5 ml) was
added p-toluenesulfonylhydrazine (0.236 g, 1.2 mmol) in small
portions. The solution was stirred at rt for 24 h. The reaction was
monitored by TLC (2% MeOH in CH2Cl2). While stirring, a white
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´
L. KLAIC ET AL.
were washed with water (25 ml) and dried over anhydrous
MgSO4. Solvent was removed in vacuo and the resulting residue
was purified by column chromatography on silica gel (0–10%
ethyl acetate in hexane). Fractions eluted with 100% hexane
afforded biphenyl (0.062 g) as a side product, while fractions
eluted using (3–5%) ethyl acetate in hexane afforded compound
12 (1.87 g, 81.9%) as a colorless crystalline solid: mp 108–1108C;
1H NMR (CDCl3) d 1.75 (br.s, 2H), 1.95–2.12 (m, 8H), 2.27 (br.s, 4H),
7.37–7.49 (m, 6H), 7.54–7.60 (m, 4H); 13C NMR (CDCl3) d 28.0 (d,
2C), 35.3 (t, 1C), 38.1 (t, 4C), 40.0 (t, 1C), 47.1 (s, 2C), 127.0 (d, 4C),
127.9 (d, 4C), 130.4 (d, 2C), 138.9 (s, 2C), 208.8 (s, 2C); IR (KBr) ~n
2934 (m), 2891 (m), 2854 (w), 1660 (s), 1444 (m), 1241 (m), 917 (m),
707 (m), 651 (m) cmꢁ1; Anal. Calcd. for C24H24O2 (344.46): C, 83.69;
H, 7.02. Found: C, 83.74; H, 6.76.
column chromatography on silica gel (50–80% EtOAc in hexane)
to yield 13 (0.827 g, 76.4%), as a white solid: mp 169.7–173.38C;
1H NMR (CDCl3) d 1.4–1.8 (m, 12H), 2.0 (s, 2H), 4.7 (s, 4H), 6.8–7.5
(m, 10H); 13C NMR (CDCl3) d 28.5 (d, 2C), 35.7 (t, 1C), 39.4 (t, 4C),
39.8 (s, 2C), 42.8 (t, 1C), 128.0 (d, 4C), 128.2 (d, 4C), 128.7 (d, 2C),
~
133.1 (s, 2C), 159.8 (s, 2C); IR (KBr) n 3369 (m), 2925 (s), 2897 (s),
2848 (s), 1621 (w), 1491 (w), 1439 (w), 1073 (w), 1021 (w), 712
(s) cmꢁ1; Anal. Calcd. for C24H28N4 (372.51): C, 77.38; H, 7.58; N,
15.04. Found: C, 76.96; H, 7.83; N, 14.98; MS EI Mþ calcd. 372.2308,
found 372.2309.
In some reactions besides 13, the sideproduct, 1-(phenylcarbinol)-
3-benzoyladamantane hydrazone, was formed in various per-
centage (from 13.6 to 36.3%): mp 208.9–2108C; 1H NMR (CDCl3) d
1.19–2.29 (m, 14H), 4.25 (s, 1H), 4.78 (s, 2H), 6.94-7.33 (m, 10H);
13C NMR (CDCl3) d 28.3 (d, 2C); 36.0 (t, 1C); 36.5 (t, 1C); 37.4 (s, 1C);
37.7 (s, 1C); 39.7 (t, 2C); 41.0 (t, 2C); 82.5 (d, 1C); 127.2 (d, 1C); 127.4
(d, 2C); 127.6 (d, 2C); 128.0 (d, 1C); 128.2 (d, 2C); 128.8 (d, 2C); 133.2
(s, 1C); 140.9 (s, 1C); 160.1 (s, 1C); IR (KBr) ~n 3403 (s), 3304 (m), 2901
1,3-Dibenzoyladamantane ditosylhydrazone (6)
To a solution of 12 (0.580 g, 1.7 mmol) in abs. MeOH (8 ml) was
added p-toluenesulfonylhydrazine (0.939 g, 5.0 mmol) in small
portions and the reaction mixture was stirred at reflux for 4 days.
The reaction was monitored by TLC (2% MeOH in CH2Cl2). While
stirring, a white residue precipitated out of the reaction mixture.
The residue was collected by filtration, washed with methanol
and diethyl ether to afford product 6 (0.938 g, 82%) as a white
powder solid: mp 172–1748C; 1H NMR (DMSO-d6) d 1.31–1.54 (m,
12H), 1.97 (br.s, 2H), 2.39 (s, 6H), 6.87 (br.s, 4H), 7.36 (d, 4H,
J ¼ 7.6 Hz), 7.42 (br.s, 6H), 7.69 (d, 4H, J ¼ 7.6 Hz), 9.27 (br.s, 2H);
13C NMR (CDCl3) d 21.6 (q, 2C), 27.9 (d, 2C), 35.1 (t, 1C), 38.7 (t, 4C),
40.6 (s, 2C), 41.5 (t, 1C), 127.5 (d, 4C), 127.7 (d, 4C), 129.2 (d, 4C),
129.3 (d, 2C), 129.4 (d, 4C), 130.8 (s, 2C), 135.2 (s, 2C), 143.9 (s, 2C),
(s), 2847 (s), 1490 (m), 1449 (m), 709 (s) cmꢁ1
.
1,3-bis(diazobenzyl)adamantane (7)
To a suspension of a barium manganate (BaMnO4; 0.635 g,
2.48 mmol) and powdered CaO26 (0.959, 17.1 mmol) in dry THF
(10 ml) was added a solution of 13 (0.115 g, 0.31 mmol) in dry THF
(10 ml) under a nitrogen atmosphere. The reaction mixture was
stirred at rt for 1 h. Filtration of solids and evaporation of the
solvent afforded 7 (0.111 g, 98.2%), as a red-wine colored oil. IR
spectrum with characteristic absorption band at 2031 cmꢁ1
confirmed formation of diazo-compound 7 which was used in the
further experiments without purification. 1H NMR (C6D6) d
1.30-2.10 (m, aliphatic H), 6.92–7.30 (m, Ph-H); 13C NMR (C6D6) d
29.3 (d, 2C), 33.1 (t, 1C), 35.6 (s, 2C), 40.1 (t, 4C), 44.4 (t, 1C), 124.7
(d, 2C), 125.8 (d, 4C), 129.2 (d, 4C), 131.1 (s, 2C); IR (KBr) ~n 2901 (s),
2848 (s), 2031 (m), 1655 (m), 1449 (m), 1025 (m), 737 (s) cmꢁ1; UV
(EtOH) lmax/nm (log e): 501.2 (1.18).
~
164.3 (s, 2C); IR (KBr) n 3276 (w), 3208 (w), 2927 (m), 2904 (m), 2854
(w), 1598 (w), 1442 (w), 1385 (m), 1338 (m), 1168 (s), 704 (m), 674
(m), 555 (s) cmꢁ1; Anal. Calcd. for C38H40N4S2O4 (680.89): C, 67.03;
H, 5.92; N, 8.23. Found: C, 66.56; H, 5.60; N, 8.06.
Preparation and pyrolysis of sodium salt of
1,3-dibenzoyladamantane ditosylhydrazone (6a)
Pyrolysis of 1,3-bis(diazobenzyl)adamantane (7)
To a suspension of 6 (0.681 g, 1.0 mmol) in dry THF (5 ml) was
added NaH (50% dispersion in mineral oil, 0.096 g, 2.0 mmol) in
small portions during 2 h at rt. Upon addition of NaH, stirring was
continued for additional 20 min, whereupon solvent was
removed in vacuo. Crude product was dried under high vacuum
(ꢂ1 ꢀ 10ꢁ3 mm Hg) for several hours. The salt was used in the
pyrolysis without further purification. The dry 6a (1 mmol) was
pyrolyzed at 2108C and 1 ꢀ 10ꢁ3 mm Hg for 10 min during which
the salt changed its color from white to pink. Volatile products
were collected in a trap cooled by liquid nitrogen, and the
resulting crude product was dissolved in benzene under a
nitrogen atmosphere. Analysis of the crude product by GC (DB
210, 608C, 10 min; 158C/min; 2008C) and GC-MS (HP-5) showed
the presence of benzonitrile and polymeric material. Benzonitrile
was confirmed by comparison of the GC and GC-MS analysis of
the authentic sample: GC-MS (HP-5; 608C, 10 min; 158C/min;
2508C); tR ¼ 14.01; m/e: 103 (Mþ 100%), 76 (39%), 50 (23%).
Diazo-compound 7 (1.0 mmol) was subjected to the pyrolysis at
6008C under reduced pressure (1 ꢀ 10ꢁ1 mm Hg). Volatile
products were collected in a trap cooled by liquid nitrogen,
and subsequently dissolved in benzene under an atmosphere of
nitrogen. Analysis of the crude product by GC (DB 210 and DB
1701; 608C, 10 min; 158C/min; 2008C) and GC-MS analysis showed
the presence of two compounds. GC-MS analysis (HP-5) showed
that the major peak has mass of Mþ(103) and corresponding to
the benzonitrile (18): GC-MS (HP-5; 608C, 10 min; 158C/min;
2508C); tR ¼ 14.01; m/e: 103 (Mþ 100%), 76 (35%), 50 (15%).
Photolysis of 1,3-bis(diazobenzyl)adamantane (7)
A degassed solution of 7 (0.046 g, 0.13 mmol) in C6D6 (0.675 ml)
was irradiated with a high pressure Hg-lamp through a Pyrex filter
until the characteristic color of the diazo-compound disappeared.
Evaporation of the solvent afforded azine 21 (0.048 g) as a pale
yellow solid: 1H NMR (C6D6) d 1.15–2.11 (m, aliphatic H), 6.87–7.36
(m, Ph-H); 13C NMR (C6D6) d 28.8, 35.9, 39.7, 40.7, 43.0, 127.3, 127.7,
128.0, 137.1, 165.3; IR (KBr) ~n 2902 (s), 2851 (s), 1743 (w), 1593 (m),
1490 (w), 1444 (m), 1341 (m), 1238 (w), 1067 (m), 764 (m), 697
(s) cmꢁ1. HRMS for C48H48N4 [M þ 1]þ calcd. 681.3957, found
681.3951.
1,3-Dibenzoyladamantane dihydrazone (13)
A solution of 12 (1.0 g, 2.9 mmol) and hydrazine monohydrate
(2.8 ml, 58 mmol) in abs. EtOH (25 ml) was refluxed for 4 days. The
solvent was removed in vacuo and the resulting solid purified by
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J. Phys. Org. Chem. 2008, 21 299–305

CARBENES IN POLYCYCLIC SYSTEMS
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´
59, 2374–2380.
ˇ
´
To a solution of 12 (0.092 g, 0.27 mmol) and 13 (0.100 g,
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p-TsOH. The mixture was heated to reflux and the reaction was
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with 0.1 M NaOH (2 ꢀ 15 ml) and water (2 ꢀ 20 ml) and dried over
anhydrous MgSO4. The solvent was evaporated in vacuo to give
21 (0.120 g, 65%), as a yellowish solid.
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Copyright ß 2008 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2008, 21 299–305