Reactions of halo- and dihaloadamantanes with nitromethane anions by the SRN1 mechanism

Article abstract of DOI:10.1002/poc.603

The reactions of 1-bromo-, 2-bromo-, 1,3-dibromo- and 1, 4-dibromoadamantane with ^-CH₂NO₂ anions were studied in DMSO and in liquid ammonia. The photostimulated reaction of 1-haloadamantane (1-AdX, X = Br, I) or 2-AdBr with ^-CH ₂NO₂ anions gave good yields of the substitution product 1-AdCH₂NO₂ and 2-AdCH₂NO₂, respectively, in the presence of the enolate anions of acetone (entrainment conditions). On the other hand, 1-adamantanol was the main product of the reaction performed in DMSO without irradiation, but not in liquid ammonia. 1,3-Dibromo and 1,4-dibromoadamantane reacted with ^-CH ₂NO₂ anions under irradiation in the presence of the enolate anions of acetone. The first compound gave the disubstitution product 11, and the second the monobromo-substitution products 15 and 16, together with the disubstitution product 17. Compounds 15 and 16 were shown to be intermediates in the formation of 17. Copyright

Full text of DOI:10.1002/poc.603

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
J. Phys. Org. Chem. 2003; 16: 413–419
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/poc.603
Reactions of halo- and dihaloadamantanes with nitro-
methane anions by the SRN1 mechanism
Ana N. Santiago,* Carlos A. Toledo and Roberto A. Rossi*
INFIQC, Departamento de QuÂõmica OrgaÂnica, Facultad de Ciencias QuõÂmicas, Universidad Nacional de Co rdoba, Ciudad Universitaria, Haya
de la Torre esq. Medina Allende, 5000 Co rdoba, Argentina
Received 9 September 2002; revised 28 November 2002; accepted 20 December 2002
ABSTRACT: The reactions of 1-bromo-, 2-bromo-, 1,3-dibromo- and 1,4-dibromoadamantane with ÀCH2NO2
anions were studied in DMSO and in liquid ammonia. The photostimulated reaction of 1-haloadamantane (1-AdX,
X = Br, I) or 2-AdBr with ÀCH2NO2 anions gave good yields of the substitution product 1-AdCH2NO2 and
2-AdCH2NO2, respectively, in the presence of the enolate anions of acetone (entrainment conditions). On the other
hand, 1-adamantanol was the main product of the reaction performed in DMSO without irradiation, but not in liquid
ammonia. 1,3-Dibromo and 1,4-dibromoadamantane reacted with ÀCH2NO2 anions under irradiation in the presence
of the enolate anions of acetone. The first compound gave the disubstitution product 11, and the second the
monobromo-substitution products 15 and 16, together with the disubstitution product 17. Compounds 15 and 16 were
shown to be intermediates in the formation of 17. Copyright  2003 John Wiley & Sons, Ltd.
KEYWORDS: SRN1; haloadamantanes; nitromethane anion; electron transfer
INTRODUCTION
ꢀ2†
ꢀ3†
The reactivity of the bridgehead halides with different
nucleophiles depends on the strain energy, the nature of
the leaving group, the nucleophiles and the solvent.
Bridgehead halides have a high-energy barrier for a polar
mechanism owing to strain factors and some of these
halides have been found to react by the SRN1 mechan-
ism.1 The SRN1 mechanism is a chain process. The
initiation step [Eqn. (1)] is an electron transfer (ET) from
the nucleophile or from a suitable electron source to give
the radical and the halide ion by a dissociative ET.2 The
propagation steps consist in the coupling of the radical
with the nucleophile to give a radical anion [Eqn. (2)],
which by ET to the substrate [Eqn. (3)], forms the inter-
mediates necessary to continue the propagation cycle.
A reaction between a nucleophile and a substrate may
show low efficiency in the initiation, but be fairly reactive
at propagation. The addition of another nucleophile that
is more reactive at initiation increases the generation of
the reactive intermediates and allows the less reactive
nucleophile to start its own propagation (entrainment
reaction).1
In liquid ammonia solution, the photostimulated
reaction of 1-iodoadamantane (1-AdI) with several
carbanions such as those derived from acetone, N-
acetylmorpholine, acetylacetone or acetonitrile afforded
the reduction product adamantane (AdH) and the dimeric
product 1,1'-biadamantane (1-Ad)23 as the only products.
However, the reaction of 1-AdI with the anion from
N-acetylthiomorpholine has been successfully achieved
under irradiation or in the presence of FeBr2 in DMSO.4
In a detailed kinetic study, it has been shown that the
reaction of 1-AdI with N-thioacetylmorpholine anion
gave good yields of substitution products with as low as
0.6–1.6 mol% of FeBr2 in DMSO.5
ꢀ1†
*Correspondence to: A. N. Santiago and R. A. Rossi, INFIQC,
Departamento de Qu´ımica Orga´nica, Facultad de Ciencias Qu´ımicas,
Universidad Nacional de Co´rdoba, Ciudad Universitaria, Haya de
la Torre esq. Medina Allende, 5000 Co´rdoba, Argentina.
E-mail: rossi@dqo.fcq.unc.edu.ar
Contract/grant sponsor: Agencia Co´rdoba Ciencia.
Contract/grant sponsor: Consejo Nacional de Investigaciones Cientı´-
ficas y Te´cnicas (CONICET).
In DMSO solution, the photostimulated reaction of
1-AdI with acetone enolate anions gave AdH (17%) and
1-adamantylacetone (20%). Higher yields of substitution
Contract/grant sponsor: SECYT.
Contract/grant sponsor: Universidad Nacional de Co´rdoba.
Contract/grant sponsor: FONCYT.
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 413–419

414
A. N. SANTIAGO, C. A. TOLEDO AND R. A. ROSSI
product were obtained with acetophenone enolate anions,
which gave AdH in low yield, and 48% of 1-adamantyl-
acetophenone (or 65% in presence of 18-crown-6 ether)
under irradiation6,7 or 85% in the reaction induced by
FeBr2.8 The photostimulated reaction of 1-AdI with
anthrone anion also gave good yields (75%) of the
substitution product in DMSO.7
On the other hand, no reaction has been observed under
irradiation of 1-AdI with ÀCH2NO2 ion. However, this
anion gave the substitution product in the presence of
acetophenone (58%) or acetone enolate anions (87%) as
entrainment nucleophiles under irradiation6,7 or in the
We have investigated the reactions of 1-bromo-,
2-bromo-, 1,3-dibromo- and 1,4-dibromoadamantane
with ÀCH2NO2 anions in DMSO and in liquid ammonia
by the SRN1 mechanism. This approach provides a facile
preparation of adamantyl compounds bearing a nitro
group. Since a nitro group is readily transformed into a
number of other useful functional groups,9 this extends
the synthetic value of the reaction.
RESULTS AND DISCUSSION
.
8
presence of FeBr2 in DMSO. Even though the 1-Ad
radicals are formed under photostimulation with acetone
enolate ion [Eqn. (1)], they do not couple with the
nucleophile to follow the SRN1 mechanism at least at a
rate to compete with other reactions (reduction or
dimerization). The ÀCH2NO2 ion is unable to initiate
the photostimulated SRN1 reaction, but it does propagate
the chain cycle very efficiently.7 The following relative
reactivity order has been determined for the reaction of
ReactÀions of 1-halo- and 2-bromoadamantanes
with CH2NO2 anions
1-AdCl did not react with ÀCH2NO2 anions in liquid
ammonia in the dark. There is a sluggish reaction under
irradiation, even in the presence of acetone enolate
anions as entrainment reagent, but in DMSO 20% yield of
the substitution product was obtained (Table 1, expts 1
and 2). There was no dark reaction of 1-AdBr with
ÀCH2NO2 anions (in the presence of acetone enolate
anions), but it reacted under photostimulation in the
presence of acetone enolate anions to give the
.
1-Ad radical with the carbanions from anthrone (80)7
>CH3NO2 (32)7 > CH3COPh (11)7 > N-acetylthiomor-
pholine (3.3)4 > CH3COCH3 (1.0).7
Table 1. Reactions of haloadamantanes with nitromethane and acetonate anionsa
Expt
Substrate
Conditions
NH3, hv, 300 min
XÀ (%)b
AdCH2NO2 (%)c
Other products (%)c
1
2
1-AdCl
1-AdCl
1-AdBr
1-AdBr
1-AdBrf
1-AdBr
1-AdBrf
1-AdBr
1-AdBr
1-AdBrf
1-AdBrf
1-AdBrf
1-AdBri
1-AdBri
1-AdI
8
27
<1
96
<5
21
36
82
38
58
67
69
<1
98
<1
77
53
93
<1
77
<5
68
4d
—
DMSO, hv, 360 min
NH3, dark, 360 min
NH3, hv, 360 min
20
AdH (9)
—
d
3
—
4
83e
—
5
NH3, hv, 360 min
2d
—
6
NH3, hv, 360 min, p-DNBg
DMSO, dark, 360 min
DMSO, hv, 360 min
DMSO, dark, 360 min
DMSO, dark, 360 min, p-DNBg
DMSO, hv, 360 min
DMSO, dark, 360 min, t-BuOHh
DMSO, dark, 120 min
DMSO, hv, 360 min
NH3, dark, 240 min
NH3, hv, 240 min
17
—
50
—
—
—
—
—
7
1-AdOH (35)
1-AdOH (37)
1-AdOH (35)
1-AdOH (53)
1-AdOH (66)
1-AdOH (64)
—
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
d
—
j
—
—
—
d
—
1-AdI
70e
—
AdH (10)
1-AdOH (57)
1-AdOH ꢁ4
—
AdH (11)
—
AdH (6)
1-AdIf
DMSO, dark, 360 min
DMSO, hv, 360 min
NH3, dark, 300 min
NH3, hv, 300 min
DMSO, dark, 360 min
DMSO, hv, 360 min
1-AdI
87
d
2-AdBr
2-AdBr
2-AdBr
2-AdBr
—
68
d
—
62
a
Substrate concentration, 2.5 Â 10À3 M; nitromethane anion, 3 Â 10À2 M; acetone enolate anion, 2 Â 10À2 M, unless indicated otherwise.
b
c
d
e
f
Determined potentiometrically.
Quantified by GC using the internal standard method, unless indicated otherwise.
Most of the substrate was recovered.
Isolated yield.
Only the nitromethane anion was present.
p-Dinitrobenzene (20 mol%) was added.
g
h
tert-Butanol (5 ml) was added.
Only the acetone enolate anion was present.
i
j
Adamantane (56%) was the only product found. Some adamantane is lost in the work-up.
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 413–419

SRN1 REACTIONS OF HALOADAMANTANES WITH NITROMETHANE ANIONS
415
1-AdCH2NO2 in 83% isolated yield [Eqn. (4)].
anions) in liquid ammonia. Under the same experimental
conditions, but under photostimulation, 1-AdCH2NO2
was obtained in 70% isolated yield together with 10% of
AdH (Table 1, expts 15 and 16).
ꢀ4†
À
In DMSO, the dark reaction of 1-AdI with CH2NO2
As the ÀCH2NO2 anion reacts 32 times faster than
acetone enolate anion,7 no substitution products derived
from the latter were found (entrainment reactions). The
photostimulated reaction in presence of acetone enolate
anions was inhibited by p-dinitrobenzene, (p-DNB), a
well-known inhibitor of SRN1 reactions1 (Table 1, expts
3–6).
Similar entrainment has been described previously in
the reaction of 1-AdI7 and also 2-AdI10 with ÀCH2NO2
anions by the SRN1 mechanism in DMSO.
anions afforded 1-AdOH (57%) in the same fashion as
did 1-AdBr. In contrast, under irradiation, 1-AdCH2NO2
was formed (87% yield), along with small amounts of
1-AdOH. These results indicate that in the dark 1-AdI
reacted only by a polar mechanism with ÀCH2NO2
anions to furnish 1-AdOH, but under irradiation the SRN
1
mechanism takes over the polar reaction to give mainly
the substitution product. On the other hand, 1-AdCl did
not give 1-AdOH in the reaction with ÀCH2NO2 anions in
DMSO.
Another feÀature that emerged from the reaction of
1-AdBr with CH2NO2 anions (with or without acetone
enolate anions) in DMSO, either in the dark or under
irradiation, is the formation of significant amounts of
1-adamantanol (1-AdOH) (360 min, 35–37% yield). This
‘solvolytic’ product was unexpected, owing to the low
reactivity of 1-AdBr in SN1 substitution reactions.
In order to determine if an ET was involved in the
formation of 1-AdOH, we performed the reaction of
1-AdBr and ÀCH2NO2 anions in the presence of p-DNB
to inhibit the radical reaction. In this case there was an
increase in the percentage of 1-AdOH (53% yield) and no
Entrainment was also needed in order to substitute
2-AdBr in liquid ammonia and DMSO with ÀCH2NO2
anions to give the substitution product 2-AdCH2NO2 in
68 and 62% yields, respectively, together with a small
amount of AdH (6–11%). No dark reactions were
detected (Table 1, expts 19–22). Again, the 2-position
of the adamantane ring shows a lower reactivity in
Polar11 and free radical reactions compared with that of
the 1-position.12,13 It has been reported that 2-AdBr
reacts with Ph2PÀ ions under irradiation whereas 2-AdCl
does not. The latter reacts, however, with Me3SnÀ ions to
give the substitution product in high yield.13 In competi-
tion experiments, 1-AdBr was shown to be 1.4 times
more reactive than 2-AdBr toward Ph2PÀ ions, whereas
1-AdCl is 12 times more reactive than 2-AdCl toward
Me3SnÀ ions.13 Previously, the photostimulated reaction
of 2-AdI in DMSO with carbanionic nucleophiles to
afford substitution products by the SRN1 mechanism has
been described.10
À
substitution by CH2NO2 anions. This result shows that
1-AdOH is formed through a polar pathway.
One possibility is a bromophilic reaction to give
1-adamantyl anion, which is attacked by the oxygen of
the nucleophile to give an oxime, which then is
hydrolyzed to 1-AdOH in the work-up. When we carried
out the reaction of 1-AdBr and ÀCH2NO2 anions in the
presence of t-BuOH to trap any carbanion derived from
adamantane, 1-AdOH was formed in 64% yield, and no
AdH was found. Also, the yield of 1-AdOH increased
ReactÀions of 1,3- and 1,4-dibromoadamantanes
with CH2NO2 anions in DMSO
À
when the reaction of 1-AdBr and CH2NO2 anions was
irradiated in the absence of acetone enolate anions (Table
1, expts 10–12). 1-AdBr did not react in the dark with
acetone enolate anions, nor was 1-AdOH formed,
whereas under irradiation the main product was AdH,
as has been reported previously3 (Table 1, expts 13 and
14).
Although the mechanism of formation of 1-AdOH is
still unknown, it seems to operate only with ÀCH2NO2
anions in the dark at room temperature in DMSO. The
fact that 1-AdBr did not react with acetonate anions in
DMSO, and that when it reacts with ÀCH2NO2 anions the
formation of 1-AdOH was not inhibited by p-DNB or by
t-BuOH, suggest that 1-AdOH is formed by a polar
bromophilic type mechanism within a solvent cage
reaction to furnish the observed product. More experi-
mental studies remain to be undertaken to elucidate this
novel substitution of 1-AdBr.
The SRN1 reactions of nucleophiles with substrates
bearing two leaving groups afford either the monosub-
stitution or disubstitution product depending on the
structure of the substrate, the nature of the nucleofugal
groups and their spatial separation, or the nucleophile.1
1-Iodo-2-chloroadamantane and 1-chloro-2-iodoada-
mantane are known to react with acetophenone enolate
anions under irradiation to afford the chloro monosub-
stitution product and small amounts of the disubstitution
product. The chloro monosubstitution products have been
shown to be intermediates in the formation of disubstitu-
tion compounds.10
A similar behavior has been found with 1,2-diiodoa-
damantane (1), which reacted with ÀCH2NO2 anions
under irradiation to give the monosubstitution product
with retention of iodine 2 (traces of iodine in the
2-position were found, indicating that the radical anion
fragment faster at the 1-position) and the disubstitution
There was no reaction in the dark of 1-AdI with
ÀCH2NO2 anions (in the presence also of acetone enolate
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 413–419

416
A. N. SANTIAGO, C. A. TOLEDO AND R. A. ROSSI
product 3 [Eqn. (5)]. In this reaction acetone enolate
anions were used as the entrainment reagent. At short
irradiation times, the main product is 2, but at longer
irradiation times, the disubstitution product 3 is the main
product, indicating that 2 is an intermediate to furnish
3.10
after acidification of the reaction [Eqns (7) and (8)].
ꢀ7†
ꢀ8†
ꢀ5†
Different results were obtained in the photostimulated
reaction of 1,3-diiodoadamantane with nitromethane
anion in DMSO [Eqn. (6)]. In this case, the only product
obtained by the SRN1 mechanism, is the ring opened 4.14
1,3-Dibromo- and 1-bromo-3-chloroadamantane did
not react with ÀCH2NO2 anions (<5%) under irradiation
(3 h) in DMSO.14 There is no reaction of 1,3-dibromo-
adamantane (10) with ÀCH2NO2 and acetone enolate
anions in DMSO in the dark, but under irradiation it
affords the disubstitution product 11, in yields that
depend on the experimental conditions. When the
substrate concentration is decreased from 10 Â 10À3 to
2.5 Â 10À3 M, the yield of 11 increases from 25 to 84%
[Eqn. (9)] (Table 2, expts 1–4).
ꢀ6†
The formation of 4 has been explained considering that
once the 3-iodoadamantyl radical is formed, it couples
with the nucleophile to give the radical anion inter-
mediate 5, which by an intermolecular ET to the substrate
forms the halomonosubstitution product 6. This com-
pound is deprotonated in the basic reaction conditions to
give the carbanion 7, which by a ring-opening reaction
renders 8, which is deprotonated to give the carbanion 9.
This carbanion transforms into the most stable isomer 4
ꢀ9†
In liquid ammonia, 10 did not react with ÀCH2NO2 and
acetone enolate anions, but under irradiation it afforded
the disubstitution compound 11 in high yields (80%)
(Table 2, expts 5–7).
Table 2. Reaction of dibromoadamantanes with ÀCH2NO2 and acetone enolate anions in DMSO
Expt
Substrate (M Â 103)
ÀCH2COCH3/ÀCH2NO2 (M Â 103)
Conditions (min)
BrÀ (%)a
Disubstitution product (%)
b
1
10, 2.5
10, 10
10, 5
10, 2.5
10, 2.5
10, 2.5
14,f 1.8
14,f 1.8
14,f 1.8
20/30
20/60
20/30
20/30
20/30
20/30
20/30
20/30
20/30
Dark (360)
hv (360)
<1
36
73
89
81
<5
<5
72
82
—
2
11, 25c
11, 49c
11, 84c
11, 80c
3
hv (300)
4
hv (360)
5d
6d
7
hv (300)
e
Dark (300)
Dark (360)
hv (360)
—
b
—
8
17, 47g
17, 77h
9d
hv (360)
a
Determined potentiometrically considering two bromide ions per molecule of substrate.
Substrate (97%) was quantified with 1-bromonaphthalene as reference.
Quantified by GC using the internal standard method with Ph3As as reference.
In liquid ammonia as solvent.
Substrate (88%) was quantified with 1-bromonaphthalene as reference.
A mixture of E- and Z-isomers was used.
b
c
d
e
f
g
Quantified by GC with 1-bromonaphthalene as reference. 1-AdCH2NO2 (5%), 2-AdCH2NO2 (2%) and a mixture of (E)- and (Z)-4-bromo-1-
nitromethyladamantane (15) and 1-bromo-4-nitromethyladamantane (16) isomers (32%) were quantified.
h
Isolated yield.
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 413–419

SRN1 REACTIONS OF HALOADAMANTANES WITH NITROMETHANE ANIONS
417
4-bromo-1-nitromethyladamantane (16) (a mixture of E-
and Z-isomers) together with 47% yield of the disubstitu-
tion product 17 (E- and Z-isomers in a 1:1 ratio) [Eqn.
(11)] (Table 2, expts 7 and 8).
ꢀ11†
Figure 1. Relative yields of the decrease of substrate 10 (&)
and the formation of 11 (*) in DMSO vs time.
These results indicate that 14 also reacts with
ÀCH2NO2 anions (with acetone enolate anions as
entrainment reagent) by the SRN1 mechanism. When 14
receives one electron, it fragments either at the 1- (major)
or at the 4-position (minor) to give radicals that react with
To fact that the formation of 11 does not occur through
the intermediacy of the monosubstitution product
1-bromo-3-nitromethyladamantane is shown by a plot
of product formation vs time, which indicates that the
production of 11 and the decrease of 10 occur
simultaneously (Fig. 1).
Under irradiation, 10 receives an electron from the
acetone enolate ion and fragments to afford 3-bromo-
adamantyl radical, which couples with ÀCH2NO2 anions
to give the radical anion intermediate 12, which by an
intramolecular ET to the other C—Br bond forms the
radical 13 to continue the chain propagation step and
ultimately give 11 [Eqn. (10)].
.
À
ÀCH2NO2 anions to furnish the radical anions 15 and
.
À
16 ; the main reaction pathway of these radical anion
intermediates is the intermolecular ET to 14 to give 15
and 16 as products the ratio of products 15 and 16 is ca
4:1, which indicates that the 1-position fragments faster
than the 4-position, as found previously15. This ET is
faster than the intramolecular ET to the C—Br bond, in
contrast to the behavior shown by the 1,3-dibromo isomer
10, for which the intramolecular ET is faster than the
intermolecular ET. The same behavior has been found in
the photostimulated reactions of 10 and 14 with Me3SnÀ
ions in liquid ammonia.15
On the other hand, the photostimulated reaction of 14
with ÀCH2NO2 and acetone enolate ion furnishes 17 in
77% isolated yield in liquid ammonia (Table 2, expt 9).
ꢀ10†
CONCLUSIONS
In the photostimulated reaction of 1-iodo-, 1-bromo-,
2-bromo- and 1,3-dibromoadamantane with ÀCH2NO2
anions in the presence of an entrainment reagent
(acetonate anion) it is possible to achieve the synthesis
of mono- and disubstitution products in very good yields
by the SRN1 mechanism either in liquid ammonia or
DMSO. In DMSO and under similar reaction conditions
1-AdBr gives 1-AdOH through a competitive process.
On the other hand, a very low yield of substitution is
obtained by reaction of 1-AdCl with ÀCH2NO2 anions (in
the presence of acetone enolate anions) under irradiation
in either liquid ammonia or DMSO.
The reaction of 1,4-dibromoadamantane with
ÀCH2NO2 and acetone enolate anions under irradiation
renders the bromo monosubstitution product as an
intermediate, in contrast to the similar reaction of
1,3-dibromoadamantane where no intermediate was
observed.
The fact that with 1,3-diiodoadamantane the intermol-
ecular ET to the substrate to give 1-iodonitromethyl-
adamantane as an intermediate is faster than the
intramolecular ET to the other C—I bond might be
ascribed to the better electron acceptor capability of
1,3-diiodoadamantane with respect to the dibromo
derivative 10. The lack of formation of ring opening
product, in the sense of Eqn. (6), is another factor which
indicates that 1-bromo-3-nitromethyladamantane is not
an intermediate in these reactions,
On the other hand, a mixture of isomers (E and Z) of
1,4-dibromoadamantane (14) did not react in the dark
with ÀCH2NO2 and acetone enolate anions in DMSO, but
under irradiation it gave (32%) of the monosubstituted
compounds 1-bromo-4-nitromethyladamantane (15) and
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 413–419

418
A. N. SANTIAGO, C. A. TOLEDO AND R. A. ROSSI
The procedure here reported is an easy method for
products were quantified by GC using the internal
standard method.
preparing adamantyl compounds containing nitro groups,
which will allow the synthesis of other adamantyl
derivatives. Therefore, we will continue the study with
other nitranions to define the scope and limitations of
these reactions.
Photostimulated reactions of 1-halo-, 2-halo- and
1,3- and 1,4-dibromoadamantanes with ÀCH2NO2
anion in DMSO
The following procedure is representative. The reactions
were carried out in a 250 ml three-necked round-
bottomed flask equipped with nitrogen inlet and magnetic
stirrer. To 100 ml of dry and degassed DMSO under
nitrogen were added CH3NO2 (3 mmol) and acetone
(2 mmol) and then t-BuOK (5 mmol) and 10 min after
last addition when no more solid was present, ÀCH2NO2
and ÀCH2COCH3 anions were ready for use. After
15 min, 1-AdX (1.0 mmol) was added and the reaction
mixture was irradiated. Then, the reaction was quenched
with an excess of ammonium nitrate. The residue was
dissolved with water (300 ml) and then extracted with
diethyl ether (100 ml). The products were isolated by
column chromatography. In the other experiments the
products were quantified by GC using the internal
standard method.
EXPERIMENTAL
General methods
NMR spectra were recorded on a Bruker AC-200 NMR
spectrometer. Mass spectral measurements were obtained
with
a Shimadzu GCMS QP5050 GC-17A gas
chromatograph–mass spectrometer system. Gas chroma-
tographic (GC) analyses were performed on a Hewlett-
Packard 5890 Series II instrument with a flame-ionization
detector and a Hewlett-Packard 3396 Series II data
system, using an HP5 (5% methylsilicone, 0.5 m Â
0.53 mm i.d.) column. Irradiation was conducted in a
reactor equipped with two 400 W UV lamps emitting
maximally at 350 nm (Philips Model HPT, water-
refrigerated). Column chromatography was performed
on silica gel (70–270 mesh ASTM). Potentiometric
titration of halide anions was performed with a pH meter
À
Reaction with CH2NO2 anion in the dark
‡
(Orion Model 420A), using an Ag/Ag electrode and
AgNO3 as standard. Melting-points were obtained with a
Bu¨chi 510 apparatus and are not corrected.
The procedure was similar to that for the previous
reaction, except that the reaction flask was wrapped with
aluminum foil.
Materials
À
Inhibited reaction with CH2NO2 anion
1- and 2-AdBr, 1-AdI, 1-AdCl, 1,3- and 1,4-dibromo-
adamantane, acetone, nitromethane, and potassium tert-
butoxide were commercially available and used as
received.
The procedure was similar to that for the previous
reaction, except that p-DNB was added to the solution of
nucleophile prior to substrate addition.
Photostimulated reactions of 1-halo-, 2-halo- and
1,3- and 1,4-dibromoadamantanes with ÀCH2NO2
in liquid ammonia
Isolation and identi®cation of the products
1-AdCH2NO2. Isolated as a yellow oil after column
chromatography on silica gel, eluted with petroleum
ether–diethyl ether (98:2) and identified by comparison
with an authentic sample.7
The following procedure is representative of these
reactions. To 300 ml of distilled ammonia were added
CH3NO2 (3 mmol) and (CH3)2CO (2 mmol) and then
t-BuOK (5 mmol) and 10 miÀn after the last addition when
2-AdCH2NO2. Isolated as a yellow oil after column
chromatography on silica gel, eluted with petroleum
ether–diethyl ether (98:2) and identified by comparison
with an authentic sample.10
À
no more solid was present, CH2NO2 and CH2COCH3
anions were ready for use. The haloadamantane (1 mmol)
dissolved in 1 ml of anhydrous diethyl ether was added to
the solution and the reaction mixture was irradiated.
Then, the reaction was quenched with an excess of
ammonium nitrate and the ammonia was allowed to
evaporate. The residue was dissolved with water and then
extracted with diethyl ether. The products were isolated
by column chromatography. In the other experiments the
1,3-Bis(nitromethyl)adamantane. Isolated as a white
solid after column chromatography on silica gel, eluted
with petroleum ether–diethyl ether (90:10); m.p. decomp.
>185°C. 1H NMR (CD3COCD3), ꢀ: 1.26–2.52 (14H, m);
4.35 (4H, s). 13C NMR (CD3COCD3), ꢀ: 28.32, 35.46,
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 413–419

SRN1 REACTIONS OF HALOADAMANTANES WITH NITROMETHANE ANIONS
419
35.60, 38.94, 41.88 and 87.32. MS (EI‡), m/z (%): 208
(19), 177 (13), 161 (27), 160 (12), 147 (26), 133 (29), 131
(15), 119 (39), 117 (18), 107 (16), 106 (14), 105 (77), 93
(42), 91 (100), 81 (42), 79 (66), 77 (42), 69 (12), 67 (35),
65 (17), 55 (23), 53 (17).
Ciencia, the Consejo Nacional de Investigaciones
Cient´ıficas y Te´cnicas (CONICET), SECYT, Universi-
dad Nacional de Co´rdoba and FONCYT. C.A.T. grate-
fully acknowledges receipt of a fellowship from
FONCYT.
(E)- and (Z)-1,4-bis(nitromethyl)adamantane. Isolated
as a mixture of E- and Z-isomers (ratio 1:1) as a light
yellow liquid after column chromatography on silica gel,
1
eluted with petroleum ether–diethyl ether (90:10). H
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34.09, 36.92, 39.83, 39.99, 40.45, 42.10, 42.20, 78.13,
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This work was supported in part by the Agencia Co´rdoba
Copyright  2003 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2003; 16: 413–419