Silylation of bicyclic six-membered nitronates. Ring-chain tautomerism of intermediate N,N bis(oxy)iminium cations

Article abstract of DOI:10.1007/s11172-006-0549-8

Silylation of bicyclic six-membered nitronates was studied as a possible route to conjugated enoximes with a distant carbonyl group. Apart from the target enoximes, this reaction yielded nitro compounds. The ratio of these two types of products and the co

Full text of DOI:10.1007/s11172-006-0549-8

Russian Chemical Bulletin, International Edition, Vol. 55, No. 11, pp. 2061—2070, November, 2006
2061
Silylation of bicyclic sixꢀmembered nitronates.
Ring—chain tautomerism of intermediate
N,Nꢀbis(oxy)iminium cations*
V. O. Smirnov,ꢀ Yu. A. Khomutova, A. A. Tishkov, and S. L. Ioffeꢀ
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 135 5328. Eꢀmail: iof@ioc.ac.ru
Silylation of bicyclic sixꢀmembered nitronates was studied as a possible route to conjugated
enoximes with a distant carbonyl group. Apart from the target enoximes, this reaction yielded
nitro compounds. The ratio of these two types of products and the configurations of their
stereogenic centers depend on the nature and configurations of the starting nitronates and the
silylation conditions. The results obtained were interpreted in terms of ring—chain tautomerꢀ
ism of intermediate N,Nꢀbis(oxy)iminium cations.
Key words: nitro compounds, cyclic nitronates, cycloaddition, retroreactions, silylation.
Scheme 1
Reactions of 5,6ꢀdihydroꢀ4Hꢀoxazines 1 and their
Nꢀoxides 2 with electrophilic agents in the presence of
bases are known to lead to migration of the double bond
in the heterocycle and the formation of 5,6ꢀdihydroꢀ2Hꢀ
oxazines 3 (see Refs 1—4). The latter compounds can
undergo fragmentation with loss of the C(6) atom to give
conjugated enoximes 4 (see Ref. 4)** or enimines 5 (see
Refs 1—3), respectively (Scheme 1). The presence of the
NꢀOSiAlk3 group in intermediate oxazines 3 sharply inꢀ
creases the fragmentation rate (cf. Refs 1—3 and 4).
The sequence of transformations for 5,6ꢀdihydroꢀ
oxazines, which is shown in Scheme 1, is employed in
organic synthesis; however, the loss of the C(6) atom
can sometimes be regarded as a drawback to this synꢀ
thesis of enoximes. This drawback can be eliminated
by starting from bicyclic 5,6ꢀdihydroꢀ4Hꢀoxazines1,6
or their Nꢀoxides,7 in which the C(6) atom is bound
to the rest of the molecule by an additional chain of
atoms.
In terms of this approach to the synthesis of enoximes,
it was of interest to investigate silylation of bicyclic
nitronates 6 since the fragmentation of the corresponding
intermediates 7 allows one to obtain virtually unstudied
α,βꢀunsaturated oximes with the distant carbonyl group
R4X = AlkX, AcX, Alk3SiX; X = Hal, OTf
R
4 = Alk,1 Ac,2 Alk3Si,3 Alk3SiO (see Ref. 4); B is a base.
* Dedicated to Academician O. M. Nefedov on the occasion of
his 75th birthday.
from very accessible compounds (simplest nitroalkanes
and derivatives of cyclic ketones) (Scheme 2).
However, the scope of this strategy has been illusꢀ
trated hitherto with only one example.7
** The known examples include fragmentation of the 5,6ꢀdiꢀ
hydroꢀ2Hꢀoxazine anions generated from sixꢀmembered cyclic
nitronates under the action of bases5 via deprotonation of posiꢀ
tion 4 of the oxazine ring.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1983—1992, November, 2006.
1066ꢀ5285/06/5511ꢀ2061 © 2006 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 55, No. 11, November, 2006
Smirnov et al.
Scheme 2
A mixture of diastereomeric nitronates 8a—d prepared
according to a known procedure8 was converted into a
mixture of silylated Eꢀ and Zꢀoximes 10 in 70% yield
(with respect to βꢀnitrostyrene) (Scheme 3).
The goal of the present work was to study the factors
that affect the stereoselectivity of new C=C double bondꢀ
ing in enoximes of the type 10* and determine the scope
of this approach to enoxime synthesis.
Results and Discussion
To investigate the stereochemistry of the silylaꢀ
tion—fragmentation of bicyclic nitronates, we obtained
each of the four stereoisomers 8a—d in the individual
state from βꢀnitrostyrene and 1ꢀtrimethylsilyloxycycloꢀ
hexene with various promoting Lewis acids. Since the
configurations of nitronates 8a,c,d are already known,8,9
the configuration of novel nitronate 8b can be unambiguꢀ
ously determined.
X = AlkO, Alk3SiO
Nitronates 8a—d were silylated with a mixture of
trimethylsilyl bromide and triethylamine at –30 °C (see
Ref. 7). After the silylation was completed (monitoring by
TLC), the reaction products were in situ desilylated with
NH4F in methanol and oximes 10b were purified by colꢀ
1
umn chromatography and analyzed by H and 13C NMR
spectroscopy. The results obtained are given in Table 1.
For their interpretation, it is expedient to discuss the
mechanisms of silylation and fragmentation.
The most plausible way of the transformation 8 → 10b
is shown in Scheme 3 (also see Ref. 7). Earlier,1 the
fragmentation of oxazines 3 has been considered to be a
concerted process. We will also analyze the stereochemiꢀ
* The configuration of the C=N double bond is not discussed;
according to the proposed synthesis of enoximes, it is assumed to
be flexible and its isomerization is possible during both the course
of the reaction and isolation of products.
Note. Hereafter, the letters a, b, c, and d denote the correspondꢀ
ing configurations.
Scheme 3
R = Me3Si (10a), H (10b)

Silylation of bicyclic oxazine Nꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 11, November, 2006 2063
Table 1. Silylation of isomeric bicyclic nitronates 8a—d
certed fragmentation can give only the Eꢀisomer of comꢀ
pound 10a (Scheme 4). The other intermediate cisꢀ9 can
exist as two eaꢀ and aeꢀconformers, which leads to silylated
Eꢀ and Zꢀisomeric oximes (Eꢀ10a and Zꢀ10a, respecꢀ
tively) (see Scheme 4). Therefore, fragmentation of the
isomer transꢀ9 (see Scheme 3, step 3) generated from
isomeric nitronates 8a and 8c should yield, in the context
of concerted fragmentation, the target enoxime with the
transꢀconfiguration (Eꢀ10b). At the same time, the fragꢀ
mentation of the cisꢀjoined oxazine cisꢀ9 (derived from
nitronates 8b and 8d) can a priori give a mixture of isoꢀ
meric oximes Eꢀ10b and Zꢀ10b; their ratio seems to deꢀ
pend on a number of thermodynamic and kinetic factors
and thus is difficult to predict.
The outcomes of the silylation of nitronates 8b—d (see
Table 1) are consistent with our analysis given above.
Indeed, the silylation of nitronate 8c gave the expected
Eꢀisomer 10b. The silylation of both nitronates 8b and 8d
selectively yielded oxime Zꢀ10b, which generally agrees
with the mechanism shown in Scheme 4. However, the
silylation of nitronate 8a gave absolutely different results
from that of nitronate 8c. Obviously, Scheme 4 does not
reflect this process comprehensively. In terms of the conꢀ
certed fragmentation of intermediate transꢀ9, the outꢀ
come of the silylation of nitronate 8a can be explained by
possible epimerization of intermediate cation A (see
Scheme 3). Such a process including the epimerization
Nitronate
τ/h
Product
Yield (%)
73
8a
72
Eꢀ10b + Zꢀ10b
(1 : 10)
8b
8c
8d
72
0.7
24
Zꢀ10b
Eꢀ10b
Zꢀ10b
82
88
84
cal outcome of the silylation—fragmentation of nitronates
8a—d in terms of concerted process.
The formation of cation A (see Scheme 3, step 1) via
reversible transfer of the Me3Si group from trimethylsilyl
bromide to the exocyclic O atom of nitronate 8 does not
affect the relative configurations of the stereogenic cenꢀ
ters C(4), C(5), and C(6); for this reason, four stereoisoꢀ
mers 8a—d should yield the corresponding four diastereoꢀ
meric cations A. Deprotonation of the C(4) atom in catꢀ
ions A makes the C(4) atom nonstereogenic; this can give
rise to only two isomeric 5,6ꢀdihydroꢀ2Hꢀoxazines,
namely, transꢀ9 and cisꢀ9 (step 2), which differ in the type
of joining the heteroꢀ and carbocyclic rings. In the conꢀ
text of concerted fragmentation, it is the configurations
and conformations of transꢀ9 and cisꢀ9 that should be
decisive for the configuration of the resulting C=C double
bond (step 3). Being sterically hindered, transꢀ9 can exist
as only one conformer (eeꢀjoint of the rings) and its conꢀ
A´
A″ through openꢀchain tautomer B is shown in
Scheme 4
Note. i. retroꢀ[4+2]. ii. Desilylation. IR is the inversion of the heterocyclic ring.

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Smirnov et al.
Scheme 5
i. Deprotonation of cations A´, A″, and B. ii. Fragmentation of the intermediates transꢀ9 and cisꢀ9. iii. Desilylation (NH4F in MeOH).
Scheme 6
detail in Scheme 5 with the silylation of nitronate 8a as an
example.*
Note that sequential deprotonation and desilylation
of the openꢀchain intermediate B could yield nitro keꢀ
tone 11, which was not detected in the real reaction
mixture.
More convincing evidence for the epimerization of
the cations of sixꢀmembered bicyclic nitronates was obꢀ
tained in the silylation of 6ꢀmethoxyꢀ4Hꢀ1,2ꢀoxazine
2ꢀoxides 15—17** (Scheme 6).
The configurations of nitronates 15—17 determined
from NMR data are given in Table 2.
Nitronates 15—17 were silylated with
a
Me3SiBr—amine mixture with subsequent standard treatꢀ
ment with NH4F in methanol (see Table 2).
Interpretation of the data obtained is represented in
Scheme 7. The formation of enoximes 23 and 24 is due to
deprotonation of the cyclic cationic tautomers C´ or C″,
while nitro compounds 25—27 form via deprotonation of
the openꢀchain cationic tautomer D followed by deꢀ
silylation of the resulting nitronates 20—22.
n = 1 (12, 15), 2 (13, 16), 3 (14, 17)
It is worth noting that the contribution of the openꢀ
chain cationic tautomer D to the silylation of bicyclic
nitronates 15—17 becomes more substantial than that in
the silylation of nitronates 8. Moreover, the silylation of
nitronate 17a gave nitro derivative 27a as the sole reacꢀ
tion product we isolated (see Table 2, entry 9).
In the series of nitronates 15—17, the nitro comꢀ
pound : enoxime ratio in the reaction products characterꢀ
istically increases with enlargement of the annulated
carbocycle. This trend correlates well with the stability
order of cyclic carbocations, which is determined from
solvolysis of their precursors.14 This correlation confirms
that nitro compounds 25—27 can really form through
deprotonation of the carbocyclic cation D stabilized by
the methoxy group.
* The possibility of ring—chain tautomerism of silyl nitronates
of functionalized nitro compounds in the presence of Lewis
acids has been assumed earlier.10,11 Epimerization of oxazines 1
and nitronates 2 has also been mentioned12 but has not been
studied in detail.
** The Me3SiO group at the C(6) atom was replaced in nitronates
15—17 by the MeO group, which comparably stabilizes the
cation,13 for unambiguous interpretation of the results obtained.
Indeed, when the starting nitronates contain the Me3SiO group
at the C(6) atom, nitro ketones of the type 11 can form both
through "openꢀchain" cationic intermediates and as a result of
desilylation of the starting nitronates (e.g., see Ref. 8).

Silylation of bicyclic oxazine Nꢀoxides
Table 2. Silylation of cyclic nitronates 15—17
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 11, November, 2006 2065
Entry
Nitronate
Silylation conditions
Enoxime
Yield
(%)
Nitro compound
Yield
(%)
Base
τ/h
T/°C
1
2
3
4
5
6
7
8
9
15a (n = 1)
15b/15a (~2.5 : 1)
15a
Et3N
Et3N
96
150
103
114
103
114
68
–30
–30
0
20
0
20
–30
0
23 E/Z ≈ 4.7 : 1
23 E/Z ≈ 0.47 : 1
23 E/Z ≈ 1 : 9
23 E/Z ≈ 1 : 6.7
23 E/Z ≈ 1 : 3
23 E/Z ≈ 1 : 2
24 E/Z ≈ 1 : 1.75
24 Z only
79
94
12*
17
26**
16
65
6
—
—
25a
—
—
76*
73
47**
68
27
88
93
Pri2NEt
Pri2NEt
Pri2NEt
Pri2NEt
Et3N
15a
25a
15b/15a (~1.1 : 1)
15b/15a (~1.1 : 1)
16a (n = 2)
16a
25a,b ~1 : 1
25a,b ~0.6 : 1
26a
Pri2NEt
Et3N
104
24
26a
27a
17a (n = 3)
–30
—
—
* The yield with respect to the consumed compound 15a (the conversion of 15a was 74%). ** The yield with respect to the consumed
mixture of 15a/15b. Apart from the reaction products, the unreacted isomer 15a (28%) was recovered.
Scheme 7
Note. RO is ring opening and RC is ring closure. i. Deprotonation of cations C´, C″, and D. ii. Fragmentation of intermediates 18
and 19. iii. Desilylation (NH4F in MeOH).

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Smirnov et al.
The formation of nitro derivatives 25—27 is proꢀ
moted by sterically more hindered bases. For inꢀ
stance, the silylation of nitronate 15a in the presence of
ethyl(diisopropyl)amine (Hunig´s base) afforded nitro
compound 25a in 73% yield, while the silylation in
the presence of triethylamine gave only a mixture of
isomeric oximes E,Zꢀ23. Replacement of triethylꢀ
amine by sterically more hindered Hunig´s base in
the silylation of nitronate 16a also radically increased
the yield of nitro compound 26a (see Table 2, entries 3,
4, 7, 8). An increase in the size of the base molecule
sharply lowers the silylation rate; that is why the reacꢀ
tion temperature should be substantially raised for
the reaction to be completed over a reasonable period
of time.
The configuration of the C=C double bond in oximino
derivatives 10a and 10b has been completely confirmed
earlier.7 The configuration of the C=C double bond in
isomeric oximes Eꢀ and Zꢀ23 was determined from their
NMR spectra similar to those of standard oximes 10b.
The NOE technique was used to assign the configurations
of conjugated oximes Eꢀ and Zꢀ24. Irradiation at the freꢀ
quency of the oximine proton (δ 7.81 for Eꢀ24 and δ 8.26
for Zꢀ24) gave rise to the responses of the vinylic proton
in Eꢀ24 (δ 5.95) and of the allylic proton in Zꢀ24 (δ 2.34).
Nitro compounds 25a and 25b were assigned to the
erythroꢀ and threoꢀseries, respectively, from close similarꢀ
ity of the signals (δ and J values) for their benzyl protons
to those for erythroꢀ and threoꢀ1ꢀ(βꢀnitroꢀαꢀphenylꢀ
ethyl)cyclohexanones.8,9
*
It should be emphasized that the formation of nitro
compounds 25—27 is stereoselective. The silylation of
nitronates 15a—17a gave diastereomerically pure nitro
compounds 25a—27a. Product 25a was assigned the
erythroꢀconfiguration (see below). The silylation of a mixꢀ
ture of isomeric nitronates 15a and 15b, which differ in
the configuration of the stereogenic center at the C(4)
and C(5) atoms, gave a mixture of isomeric erythroꢀ25a
and threoꢀ25b. The ratio of the isomers 25a : 25b can
depend not only on the 15a : 15b ratio but also on the
relative deprotonation rates of the corresponding openꢀ
chain cationic intermediates D. A comparison of entries 5
and 6 (see Table 2) revealed that isomeric openꢀchain
cationic intermediates D formed from nitronates 15a
and 15b are probably deprotonated at different rates.
The 25a : 25b ratio also depends on the silylation temꢀ
perature. Taking into consideration the results under enꢀ
try 5 (see Table 2), one can conclude that the silylation of
nitronate 15b in the presence of Hunig´s base occurs
slightly more rapidly than the silylation of isomeric
nitronate 15a.
The structures and purity of the compounds obtained
were confirmed by NMR spectra and elemental analyꢀ
sis data.
The configurations of novel nitronates 15a—17a
and 15b were taken to be the same as for nitronates 8a
and 8b, respectively, because of the similarity of their
NMR spectra (characteristic signals for H(3) and H(4),
see Experimental) and with consideration for the methods
of their preparation.
Thus, we interpreted the results of the silylation of
bicyclic nitronates 8 and 15—17 in terms of ring—chain
tautomerism of cationic silylation intermediates (see
Scheme 7, transformation C
D). For more convincꢀ
ing confirmation of the tautomeric equilibrium, we atꢀ
tempted its direct detection.
Recently,15 we have proposed a lowꢀtemperature NMR
procedure for direct detection of cationic intermediates
generated in the silylation of sixꢀmembered cyclic nitroꢀ
nates. Our purpose was to observe openꢀchain tautomeric
cation 28 in the silylation of nitronate 17a (Scheme 8).
However, the lowꢀtemperature NMR spectra contained
only one set of signals for one of the two stereoisomers of
cyclic cationic tautomer 29. In contrast, in the silylation
of nitronate 30, the openꢀchain cation of silyl nitronate 31
was detected only.**
Thus, the silylation of bicyclic nitronates with silyl
triflates gave both cyclic and openꢀchain cations; however,
these forms were not in mobile tautomeric ring—chain
equilibrium. For this reason, ring—chain tautomerism of
cationic intermediates can be regarded so far only as a
fairly justified hypothesis.
Hence, the silylation of annulated bicyclic sixꢀmemꢀ
bered nitronates in the presence of bases afforded a small
series of conjugated enoximes with the distant carboxy
group. Extension of this strategy to other objects can be
hindered by a side process such as the formation of cyclic
vinylic ethers containing a nitro fragment. The stereoꢀ
selectivity of the generation of the new C=C double bond
is determined by both the configurations of the starting
* For instance, for the threoꢀisomer of 1ꢀ(βꢀnitroꢀαꢀphenylꢀ
ethyl)cyclohexanone, the signals for the protons at the nitro
group appear at δ 4.92 (dd, 1 H, J = 4.5 Hz, J = 12.5 Hz) and
4.64 (dd, 1 H, J = 9.7 Hz, J = 12.5 Hz), while for the
erythroꢀisomer, the corresponding signal appears at δ 4.79 (d,
2 H, J = 7.5 Hz).
** Nitronate 30 has been kindly provided by A. V. Lesiv.
Silylation of nitronate 30 in the presence of bases will be reꢀ
ported elsewhere.

Silylation of bicyclic oxazine Nꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 11, November, 2006 2067
Scheme 8
(750 mg, 2.34 mmol, 39%) were filtered off, the mother liquor
was concentrated in vacuo, and the residue was chromatographed
on silica gel (AcOEt—hexane, 1 : 3) to give nitronate 8b
(0.74 g, 2.34 mmol, 39%) as a colorless oil contaminated with
8% nitronate 8a (1H NMR data).
bicyclic nitronates and the contributions from tautomeric
processes.
Experimental
Nitronate 8b, Rf 0.28 (AcOEt—hexane, 1 : 1). 1H NMR
(300.13 MHz), δ: 7.22—7.40 (m, 3 H, Ph); 7.15—7.22 (m, 2 H,
Ph); 6.47 (d, 1 H, CH=N, J = 2.8 Hz); 4.41 (dd, 1 H, CHPh,
J = 2.8 Hz, J = 6.0 Hz); 2.34 (t, CHCHPh, J = 6.5 Hz); 2.21 (m,
1 H, CH2); 1.87 (m, 2 H, CH2); 0.90—1.80 (m, 5 H, CH2);
0.27 (s, 9 H, Si(CH3)3). 13C NMR, δ: 137.7, 128.7, 128.5,
127.4, 113.0, 105.2, 41.6, 40.7, 37.5, 24.8, 24.5, 22.8, 1.8.
29Si NMR, δ: 16.6.
Silylation of nitronates 8a—d (general procedure). Triethyꢀ
lamine (2.6 mmol, 0.36 mL) and Me3SiBr (2.3 mmol, 0.31 mL)
were successively added at –30 °C (cooling with acetone—liqꢀ
uid nitrogen) to a stirred solution of nitronate 8 (320 mg, 1 mmol)
in CH2Cl2 (3 mL). The reaction mixture was kept in a freezing
chamber at –30 °C for a time specified in Table 1. Methanol
(2.5 mL) and 0.1 M NH4F in MeOH (0.5 mL) were added. The
resulting reaction mixture was kept at room temperature until
silylated products disappeared completely (usually for 4—5 h;
TLC monitoring in AcOEt—hexane, 1 : 1) and neutralized with
trifluoroacetic acid (0.024 mL). Silica gel (1 g) was added and
the resulting suspension was evaporated to dryness in a rotary
evaporator. The solid residue was placed at the head of a column
prepacked with silica gel (15 g) and eluted as normal with
AcOEt—hexane (1 : 1). The products obtained and their yields
are specified in Table 1.
All reactions were carried out in an atmosphere of dry argon.
The reagents Et3N (Acros), EtPri2N (Acros), SnCl4 (Acros),
and Me3SiBr (Acros) and the solvents CH2Cl2, CDCl3, and
CD2Cl2 were distilled over CaH2 under dry argon. NMR spectra
were recorded on a Bruker AMꢀ300 instrument (300 (1H),
75 (13C), and 59.6 MHz (29Si)) at 30 °C in CDCl3, unless
otherwise specified; the NMR scale was calibrated against the
residual signal of the solvent.16 Chemical shifts are quoted in
ppm (δ scale) and coupling constants are given in Hz. The
INEPT technique was used in recording 29Si spectra. Column
chromatography was carried out on Silica gel 60 (Merck,
230—400 mesh). Thinꢀlayer chromatography was carried out on
Merck plates (silica gel 60 F254 on an aluminum sheet).
Trimethylsilyl triflate,17 βꢀnitrostyrene,18 1ꢀ(trimethylsilylꢀ
oxy)cyclohexene,19 1ꢀmethoxycyclohexene,20 1ꢀmethoxycycloꢀ
heptene,20 1,1ꢀdimethoxycyclooctane,20 and nitronates 8a,8 8c,8
and 8d were prepared as described earlier (see Refs 8, 9).
relꢀ(4S,4aS,8aR)ꢀ4ꢀPhenylꢀ8aꢀtrimethylsilanyloxyꢀ
4a,5,6,7,8,8aꢀhexahydroꢀ4Hꢀbenzo[e][1,2]oxazine 2ꢀoxide (8b).
Tin tetrachloride (7.2 mmol, 0.84 mL) was added at –94 °C
(cooling with acetone—liquid nitrogen) to a stirred solution of
βꢀnitrostyrene (0.90 g, 6 mmol) and 1ꢀ(trimethylsilyloxy)cycloꢀ
hexene (1.74 mL, 8.92 mmol) in CH2Cl2 (24 mL). The reaction
mixture was kept at –94 °C for 5 min and poured into a vigorꢀ
ously stirred mixture of light petroleum (75 mL) and a saturated
aqueous solution of NaHCO3 (50 mL). The organic layer was
separated and the aqueous phase was washed with light petroꢀ
leum (75 mL). The combined organic phases were successively
washed with a saturated aqueous solution of NaHCO3 and brine
(2×30 mL), dried over Na2SO4, and concentrated in vacuo.
Light petroleum (5 mL) was added to the resulting colorless oil.
On cooling to –30 °C for 16 h, white crystals of nitronate 8a
6ꢀ(E)ꢀ8ꢀHydroxyiminoꢀ7ꢀphenyloctꢀ6ꢀenoic acid (Eꢀ10b),
Rf 0.20 (AcOEt—hexane, 1 : 1), m.p. 106—110 °C. Found (%):
C, 67.62; H, 6.76; N, 5.49. C14H17NO3. Calculated (%):
1
C, 68.00; H, 6.93; N, 5.66. H NMR, δ: 9.80 (br.s., 2 H, OH);
7.91 (s, 1 H, HC=N); 7.35 (m, 3 H, Ph); 7.12 (m, 2 H, Ph); 5.97
(t, 1 H, HC=C, 3J = 7.5 Hz); 2.20 (t, 2 H, CH2CO2, 3J =
3
7.2 Hz); 2.06 (dt, 2 H, CH2C=C, 3J ≈ J ≈ 7.4 Hz); 1.52 (tt, 2 H,
CH2, 3J ≈ 3J ≈ 7.4 Hz); 1.42 (tt, 2 H, CH2, 3J ≈ 3J ≈ 7.2 Hz).
13C NMR, δ: 178.9, 153.7, 140.3, 137.0, 135.4, 129.3, 128.4,
127.7, 33.7, 28.7, 28.6, 24.3.

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Smirnov et al.
6ꢀ(Z )ꢀ8ꢀHydroxyiminoꢀ7ꢀphenyloctꢀ6ꢀenoic acid (Zꢀ10b),
Rf 0.18 (AcOEt—hexane, 1 : 1), m.p. 103—105 °C. Found (%):
C, 67.99; H, 7.05; N, 5.83. C14H17NO3. Calculated (%):
CHCHPh); 2.00—1.82 (m, 2 H, CH2); 1.56—1.74 (m, 4 H,
CH2); 1.04—1.53 (m, 4 H, CH2). 13C NMR, δ: 138.9, 129.0,
128.8, 127.9, 115.4, 109.0, 49.7, 47.3, 44.6, 32.4, 26.9, 26.2,
25.5, 20.0.
1
C, 68.00; H, 6.93; N, 5.66. H NMR, δ: 10.30 (br.s, 2 H, OH);
8.31 (s, 1 H, HC=N); 7.30 (m, 5 H, Ph); 5.93 (t, 1 H, HC=C,
r e l ꢀ ( 4 R , 4 a S , 1 0 a R ) ꢀ 1 0 a ꢀ M e t h o x y ꢀ 4 ꢀ p h e n y l ꢀ
4a,5,6,7,8,9,10,10aꢀoctahydroꢀ4Hꢀcycloocta[e][1,2]oxazine
2ꢀoxide (17a). Tin tetrachloride (2.08 g, 0.94 mL, 8 mmol) was
added at –78 °C (cooling with acetone—dry ice) to a stirred
solution of βꢀnitrostyrene (0.6 g, 4 mmol) and 1,1ꢀdimethoxyꢀ
cyclooctane (1.03 g, 6 mmol) in CH2Cl2 (8 mL). The reaction
mixture was kept at –78 °C for 5 min and then EtNPri2 (0.83 g,
1.06 mL, 6.4 mmol) was added. After the mixture was stirred at
–78 °C for an additional 10 min, it was poured into a vigorously
stirred mixture of AcOEt (40 mL) and a saturated aqueous soluꢀ
tion of NaHCO3 (20 mL). The organic layer was separated and
the aqueous phase was washed with AcOEt (2×20 mL). The
combined organic phases were successively washed with a satuꢀ
rated aqueous solution of NaHCO3 and brine (2×15 mL), dried
over Na2SO4, and concentrated in vacuo. The product was puriꢀ
fied by column chromatography on silica gel with AcOEt—hexꢀ
ane (1 : 1) as an eluent. The yield was 0.613 g (53%), m.p.
126—128 °C (Et2O), Rf 0.33 (AcOEt—hexane, 1 : 1). Found (%):
C, 70.77; H, 7.79; N, 5.03. C17H23NO3. Calculated (%):
C, 70.56; H, 8.01; N, 4.84. 1H NMR, δ: 7.38—7.26 (m, 3 H,
Ph); 7.19—7.25 (m, 2 H, Ph); 6.27 (d, 1 H, CH=N, J = 2.9 Hz);
3.51 (dd, 1 H, CHPh, J = 2.9 Hz, J = 11.1 Hz); 3.46 (s, 3 H,
OCH3); 2.14—2.28 (m, 2 H, CHCHPh + CH2); 1.94—2.06 (m,
1 H, CH2); 1.21—1.83 (m, 10 H, CH2). 13C NMR, δ: 138.9,
129.0, 128.8, 127.8, 115.5, 109.3 (–), 49.7, 45.1, 40.8, 30.6,
28.4, 26.3, 26.2, 24.5, 21.0.
Silylation of nitronates 15a—17a and 15b (general proceꢀ
dure). A solution of a nitronate (1 equiv.) in CH2Cl2 (3 mL per
millimole of the nitronate) was cooled to –30 °C. An appropriꢀ
ate amine (1.5 equiv., see Table 2) and Me3SiBr (1.2 equiv.)
were successively added with stirring and the reaction mixture
was kept at –30 °C for a time specified in Table 2. Methanol
(2.5 mL) and 0.1 M NH4F in MeOH (0.5 mL) were added. The
resulting mixture was kept at room temperature until silylated
products disappeared completely (usually for 4—5 h; TLC moniꢀ
toring). Silica gel (1 g) was added and the resulting suspension
was evaporated to dryness. The solid residue was placed at the
head of a column prepacked with silica gel (15 g) and eluted as
normal with AcOEt—hexane (1 : 3). The yields of the products
obtained are specified in Table 2.
3
3J = 7.8 Hz); 2.37 (dt, 2 H, CH2C=C, 3J ≈ J ≈ 7.3 Hz); 2.33 (t,
2 H, CH2CO2, 3J = 7.1 Hz); 1.66 (tt, 2 H, CH2, 3J ≈ 3J ≈
7.4 Hz); 1.54 (tt, 2 H, CH2, 3J ≈ 3J ≈ 7.5 Hz). 13C NMR, δ:
179.0, 147.9, 139.3, 138.9, 134.8, 128.6, 128.3, 127.6, 33.8, 29.0,
28.0, 24.4.
Synthesis of nitronates 15a,b and 16 (general procedure). Tin
tetrachloride (12 mmol, 1.40 mL) was added at –78 °C (cooling
with acetone—dry ice) to a stirred solution of βꢀnitrostyrene
(1.50 g, 10 mmol) in CH2Cl2 (30 mL). The mixture was kept at
this temperature for 5 min and then an appropriate vinylic ether
(15 mmol) was added. The reaction mixture was kept at –78 °C
for an additional 10 min and poured into a vigorously stirred
mixture of AcOEt (90 mL) and a saturated aqueous solution of
NaHCO3 (50 mL). The organic layer was separated and the
aqueous phase was washed with AcOEt (2×50 mL). The comꢀ
bined organic phases were successively washed with a saturated
aqueous solution of NaHCO3 and brine (2×30 mL), dried over
Na2SO4, and concentrated in vacuo to give a colorless oil, which
crystallized as colorless crystals of the target product upon addiꢀ
tion of ether (15 mL).
relꢀ(4R,4aS,8aR)ꢀ8aꢀMethoxyꢀ4ꢀphenylꢀ4a,5,6,7,8,8aꢀ
hexahydroꢀ4Hꢀbenzo[e][1,2]oxazine 2ꢀoxide (15a). The yield
was 69%, m.p. 134—135 °C (Et2O), Rf 0.25 (AcOEt—hexane,
1 : 1). Found (%): C, 69.11; H, 7.55; N, 5.44. C15H19NO3.
Calculated (%): C, 68.94; H, 7.33; N, 5.36. 1H NMR, δ:
7.22—7.35 (m, 3 H, Ph); 7.12—7.18 (m, 2 H, Ph); 6.30 (d, 1 H,
CH=N, J = 3.0 Hz); 3.51 (dd, 1 H, CHPh, J = 3.0 Hz, J =
11.0 Hz); 3.44 (s, 3 H, OCH3); 2.20—2.28 (m, 1 H, CHCHPh);
1.80 (dt, 1 H, CH2, J = 3.8 Hz, J = 11.4 Hz); 1.62—1.72 (m,
2 H, CH2); 1.05—1.52 (m, 5 H, CH2). 13C NMR, δ: 138.6,
128.9, 128.5, 127.8, 115.6, 105.4, 49.1, 44.0, 43.2, 28.9, 25.7,
24.9, 22.1.
relꢀ(4R,4aR,8aR)ꢀ8aꢀMethoxyꢀ4ꢀphenylꢀ4a,5,6,7,8,8aꢀ
hexahydroꢀ4Hꢀbenzo[e][1,2]oxazine 2ꢀoxide (15b). The mother
liquor from the crystallization of nitronate 15a was concenꢀ
trated in vacuo and cooled with ether (5 mL) to –30 °C. The
resulting colorless crystals were filtered off. According to
1H NMR data, the crystals were composed of nitronates 15b
and 15a in the ratio from 2.5 : 1 to 1 : 1. The yield of nitronate
15b was ~10% (1H NMR data), Rf 0.25 (AcOEt—hexane, 1 : 1).
Found (together with 15a) (%): C, 69.04; H, 7.57; N, 5.41.
Methyl 6ꢀ(E )ꢀ8ꢀhydroxyiminoꢀ7ꢀphenyloctꢀ6ꢀenoate (Eꢀ23),
Rf 0.25 (AcOEt—hexane, 1 : 3). 1H NMR, δ: 8.53 (br.s, 1 H,
OH); 7.80 (s, 1 H, HC=N); 7.24—7.41 (m, 3 H, Ph); 7.08—7.16
(m, 2 H, Ph); 5.91 (t, 1 H, HC=C, J = 7.5 Hz); 3.63 (s, 3 H,
OMe); 2.22 (t, 2 H, CH2CO2, J = 7.3 Hz); 2.06 (q, 2 H,
C
15H19NO3. Calculated (%): C, 68.94; H, 7.33; N, 5.36.
1H NMR, δ: 7.22—7.35 (m, 3 H, Ph); 7.10—7.18 (m, 2 H, Ph);
6.44 (d, 1 H, CH=N, J = 2.8 Hz); 4.43 (dd, 1 H, CHPh, J =
2.8 Hz, J = 6.4 Hz); 3.49 (s, 3 H, OCH3); 2.36 (br.d, 1 H,
CHCHPh, J = 13.4 Hz); 0.90—1.95 (m, 8 H, CH2). 13C NMR,
δ: 137.4, 128.8, 128.4, 127.4, 113.5, 106.1, 49.2, 40.7, 39.7, 31.2,
24.9, 24.4, 22.2.
3
CH2C=C, J = 7.3 Hz); 1.54 (tt, 2 H, CH2, 3J ≈ J ≈ 7.4 Hz); 1.41
(tt, 2 H, CH2, 3J ≈ 3J ≈ 7.2 Hz). 13C NMR, δ: 174.0, 153.4,
139.6, 137.1, 135.6, 129.2, 128.3, 127.6, 51.5, 33.8, 28.7,
28.6, 24.4.
relꢀ(4R,4aS,9aR)ꢀ9aꢀMethoxyꢀ4ꢀphenylꢀ4,4a,5,6,7,8,9,9aꢀ
octahydrocyclohepta[e][1,2]oxazine 2ꢀoxide (16a). The yield
was 75%, m.p. 152—153 °C (Et2O), Rf 0.26 (AcOEt—hexane,
1 : 1). Found (%): C, 69.72; H, 7.84; N, 5.21. C16H21NO3.
Calculated (%): C, 69.79; H, 7.69; N, 5.09. 1H NMR, δ:
7.22—7.36 (m, 3 H, Ph); 7.13—7.19 (m, 2 H, Ph); 6.24 (d,
1 H, CH=N, J = 3.0 Hz); 3.49 (dd, 1 H, CHPh, J = 3.1 Hz,
J = 11.2 Hz); 3.45 (s, 3 H, OCH3); 2.07—2.20 (m, 1 H,
Methyl 6ꢀ(Z )ꢀ8ꢀhydroxyiminoꢀ7ꢀphenyloctꢀ6ꢀenoate (Zꢀ23),
Rf 0.25 (AcOEt—hexane, 1 : 1). 1H NMR, δ: 8.74 (br.s, 1 H,
OH); 8.17 (s, 1 H, HC=N); 7.22—7.41 (m, 5 H, Ph); 5.88 (t,
1 H, HC=C, 3J = 7.7 Hz); 3.67 (s, 3 H, OMe); 2.36 (q, 2 H,
CH2C=C, J = 7.4 Hz); 2.33 (t, 2 H, CH2CO2, 3J = 7.2 Hz); 1.70
(tt, 2 H, CH2, J = 7.4 Hz); 1.55 (tt, 2 H, CH2, J = 7.2 Hz).
13C NMR, δ: 174.0, 147.6, 138.4, 137.1, 135.0, 128.6, 128.1,
127.5, 51.5, 33.8, 29.1, 27.8, 24.4.

Silylation of bicyclic oxazine Nꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 11, November, 2006 2069
For the mixture of the isomers Eꢀ23 and Zꢀ23, found (%):
C, 69.11; H, 7.48; N, 5.62; C15H19NO3; calculated (%): C, 68.94;
H, 7.33; N, 5.36.
4.4 Hz, J = 11.5 Hz); 2.00—2.25, 1.64—1.80 (both m, 2 H each,
CH2); 1.41—1.56 (m, 1 H, CH2); 1.16—1.40 (m, 3 H, CH2);
0.96—1.14 (m, 2 H, CH2). 13C NMR, δ: 155.1, 139.3, 128.9,
128.1, 127.5, 99.2, 80.1, 54.3, 45.6, 40.2, 32.4, 32.3, 27.8,
26.4, 25.5.
Methyl 7ꢀ(E )ꢀ9ꢀhydroxyiminoꢀ8ꢀphenylnonꢀ7ꢀenoate (Eꢀ24),
Rf 0.26 (AcOEt—hexane, 1 : 3). 1H NMR, δ: 8.40 (br.s, 1 H,
OH); 7.81 (s, 1 H, HC=N); 7.25—7.38 (m, 3 H, Ph); 7.10—7.18
Study of cationic intermediates in the silylation of sixꢀmemꢀ
bered cyclic nitronates (general procedure). A solution of a
nitronate (0.05 mmol) and 2,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethylpyridine
(10 mg, 0.05 mmol) in CD2Cl2 (0.5 mL) was prepared in an
NMR tube filled with argon and closed with a septum. The tube
was cooled to 200 K and a silyl triflate (0.075 mmol; TMSOTf
for 29 and TBDMSOTf for 31) was added with a microsyringe.
The tube was rapidly shaken several times for homogenization
and placed in the cooled (210 K) probe of an NMR spectroꢀ
meter. The spectra of the starting nitronates and the sample with
silyl triflate are given below. The cationic intermediate derived
from compound 17a was assigned cyclic structure 29 since its
characteristic parameters in the NMR spectra were similar to
the corresponding parameters of cations obtained in the silylation
of sixꢀmembered cyclic nitronates.15 The cationic intermediate
derived from compound 30 was assigned acyclic structure 31
according to its spectrum. The characteristic signal in the
29Si NMR spectrum is typical of silyl nitronates.
Nitronate 17a. 1H NMR (CD2Cl2, –63 °C), δ: 7.25—7.40
(m, 3 H, Ph); 7.20 (d, 2 H, oꢀPh, J = 7.3 Hz); 6.21 (d, 1 H,
H(3), J = 2.5 Hz); 3.44 (dd, 1 H, H(4), J = 10.6 Hz, J = 2.3 Hz);
3.35 (s, 3 H, OMe); 2.14 (br.t, 1 H, H(4a), J ≈ 9.0 Hz); 1.92,
1.70 (both m, 1 H each, C(10)H2); 1.10—1.66 (m, 10 H,
C(5)H2—C(9)H2). 13C NMR (CD2Cl2, –63 °C), δ: 138.6
(s, Phipso); 128.6, 128.4, 127.3 (CH, Ph); 115.1 (C(3)); 108.9
(C(10a)); 49.2 (OMe); 44.2 (C(4)); 36.8 (C(4a)); 25.5 (2 C);
24.0, 23.8, 22.0, 21.0 (C(5)—C(10)).
Intermediate 29. 1H NMR (CD2Cl2, –63 °C), δ: 8.13 (d,
1 H, H(3), J = 2.3 Hz); 7.36—7.50 (m, 3 H, Ph); 7.20 (d, 2 H,
oꢀPh, J = 7.8 Hz); 3.97 (dd, 1 H, H(4), J = 11.5 Hz, J = 2.3 Hz);
3.47 (s, 3 H, OMe); 2.44 (br.t, 1 H, H(4a), J ≈ 9.0 Hz); 2.09,
2.30 (both m, 1 H each, C(10)H2); 1.84, 0.98—1.76 (2 m, 1 H
and 9 H, C(5)H2—C(9)H2); 0.45 (s, 9 H, SiMe3). 13C NMR
(CD2Cl2, –63 °C), δ: 143.2 (C(3)), 132.8 (s, Phipso); 129.6,
129.0 (CH, Ph); 122.0 (C(10a)); 119.5 (q, CF3); 51.8 (OMe);
45.0 (C(4)); 36.3 (C(4a)); 26.0, 24.4, 23.3, 22.7, 21.0, 20.4 (s,
CH2); 1.4 (Si(CH3)3). 29Si NMR (CD2Cl2, –63 °C), δ: 49.7.
Nitronate 30. 1H NMR (CD2Cl2, –63 °C), δ: 7.10—7.40
(m, 5 H, Ph); 3.80 (br.t, 4 H, C(11)H, C(12)H); 3.50 (d, 1 H,
H(4), J = 10.6 Hz); 3.40 (br.q, 4 H, C(9)H, C(10)H); 2.65—3.00
(3 m, 3 H, C(5)H, C(8)H, C(8a)H); 1.70 (s, 3 H, C(3)Me); 1.50
(m, 6 H, C(6)H2, C(7)H2), C(5)H, C(8)H). 13C NMR (CD2Cl2,
–63 °C), δ: 140.9 (s, Phipso); 128—130 (CH, Ph); 122.4 (C(3));
100.1 (C(8a)); 67.9 (C(11), C(12)); 46.9 (C(4)); 44.7, 44.0
(C(9), C(10)); 39.8 (C(4a)); 25.3, 23.2, 22.2, 18.0 (4 CH2);
22.0 (C(13)).
Intermediate 31. 1H NMR (CD2Cl2, –63 °C), δ: 7.47 (d,
2 H, oꢀPh, J = 7.3 Hz); 7.42 (t, 2 H, mꢀPh, J = 7.2 Hz); 7.36 (t,
1 H, pꢀPh, J = 7.1 Hz); 4.63 (d, 1 H, H(4), J = 11.7 Hz); 4.43
(ddd, 1 H, H(9), J = 13.4 Hz, J = 7.8 Hz, J = 3.2 Hz); 4.28 (m,
1 H, H(9) or H(10)); 4.21 (m, 1 H, H(9) or H(10)); 4.13 (br.d,
1 H, H(9) or H(10), J = 13.3 Hz); 4.22 (m, 1 H, H(4a)); 4.05,
3.92 (both m, 4 H, H(11), H(12)); 3.28 (td, 1 H, H(8), J =
12.5 Hz, J = 5.5 Hz); 3.20 (br.d, 1 H, H(8), J = 14.4 Hz); 2.28
(m, 1 H, H(7)); 1.96 (br.d, 1 H, H(5), J = 14.8 Hz); 1.90 (s, 3 H,
C(3)Me); 1.85 (m, 2 H, H(5), H(7)); 1.65, 1.48 (both m, 2 H,
3
(m, 2 H, Ph); 5.95 (t, 1 H, HC=C, J = 7.7 Hz); 3.66 (s, 3 H,
OMe); 2.22 (t, 2 H, CH2CO2, J = 7.3 Hz); 2.06 (q, 2 H,
CH2C=C, J = 7.3 Hz); 1.66 (tt, 2 H, CH2, J = 7.5 Hz); 1.51 (tt,
2 H, CH2, J = 7.1 Hz); 1.41 (tt, 2 H, CH2, J = 6.7 Hz).
13C NMR, δ: 174.0, 148.3, 140.1, 136.7, 135.6, 129.2, 128.6,
128.1, 51.5, 33.9, 29.2, 28.8, 28.6, 24.8.
Methyl 7ꢀ(Z )ꢀ9ꢀhydroxyiminoꢀ8ꢀphenylnonꢀ7ꢀenoate (Zꢀ24),
Rf 0.26 (AcOEt—hexane, 1 : 3). 1H NMR, δ: 8.28 (br.s, 1 H,
OH); 8.26 (s, 1 H, HC=N); 7.27—7.32 (m, 5 H, Ph); 5.92 (t,
1 H, HC=C, 3J = 7.7 Hz); 3.67 (s, 3 H, OMe); 2.34 (q, 2 H,
CH2C=C, J = 7.4 Hz); 2.32 (t, 2 H, CH2CO2, 3J = 7.3 Hz); 1.66
(tt, 2 H, CH2, J = 7.5 Hz); 1.51 (tt, 2 H, CH2, J = 7.1 Hz); 1.41
(tt, 2 H, CH2, J = 6.7 Hz). 13C NMR, δ: 174.0, 148.3,
139.5, 139.0, 134.5, 128.5, 128.0, 127.4, 51.5, 34.0, 29.1, 28.7,
28.0, 24.7.
For the mixture of Eꢀ24 and Zꢀ24, found (%): C, 69.99;
H, 7.53; N, 5.41; C16H21NO3; calculated (%): C, 69.79;
H, 7.69; N, 5.09.
erythroꢀ[1ꢀ(2ꢀMethoxycyclohexꢀ2ꢀenyl)ꢀ2ꢀnitroethyl]benꢀ
zene (25a), Rf 0.55 (AcOEt—hexane, 1 : 1). Found (%): C, 69.20;
H, 7.25; N, 5.19. C15H19NO3. Calculated (%): C, 68.94; H,
7.33; N, 5.36. 1H NMR, δ: 7.21—7.36 (m, 5 H, Ph); 4.83—4.90
(m, 1 H, CH=COCH3); 4.67—4.77 (m, 2 H, CH2NO2); 3.75
(dt, 1 H, CHPh, J = 6.0 Hz, J = 9.6 Hz); 3.52 (s, 3 H, OCH3);
2.42—2.50 (m, 1 H, CHCHPh); 2.04—2.15 (m, 2 H, CH2);
1.37—1.72 (m, 4 H, CH2). 13C NMR, δ: 155.2, 139.3, 128.7,
128.1, 127.9, 96.1, 80.0, 53.5, 47.2, 40.6, 25.6, 23.5, 18.3.
threoꢀ[1ꢀ(2ꢀMethoxycyclohexꢀ2ꢀenyl)ꢀ2ꢀnitroethyl]benzene
1
(25b), Rf 0.55 (AcOEt—hexane, 1 : 1). H NMR, δ: 7.10—7.40
(m, 5 H, Ph); 4.95 (dd, 1 H, CHNO2, J = 13.0 Hz, J = 10.7 Hz);
4.77 (t, 1 H, CH=COCH3, J = 3.0 Hz); 4.66 (dd, 1 H, CHNO2,
J = 13.4 Hz, J = 4.7 Hz); 4.00 (dt, 1 H, CHPh, J = 10.9 Hz, J =
3.8 Hz); 3.54 (s, 3 H, OCH3); 2.66 (m, 1 H, CHCHPh); 1.97
(m, 1 H, CH2); 1.86 (m, 1 H, CH2); 1.55—1.64 (m, 1 H, CH2);
1.25—1.40 (m, 3 H, CH2). 13C NMR, δ: 154.3, 138.3, 128.5,
128.2, 127.2, 97.4, 77.7, 53.9, 46.0, 41.8, 26.7, 23.6, 21.5.
For the mixture of 25a and 25b, found (%): C, 68.63; H, 7.00;
N, 5.55; C15H19NO3; calculated (%): C, 68.94; H, 7.33; N, 5.36.
Eꢀ1ꢀMethoxyꢀ7ꢀ(2ꢀnitroꢀ1ꢀphenylethyl)cycloheptene (26a),
Rf 0.51 (AcOEt—hexane, 1 : 3), m.p. 111—112 °C. Found (%):
C, 69.52; H, 7.54; N, 4.88. C16H21NO3. Calculated (%):
C, 69.79; H, 7.69; N, 5.09. 1H NMR, δ: 7.21—7.38 (m, 5 H,
Ph); 4.83—4.93 (m, 1 H, CH=COCH3); 4.57—4.66 (m, 2 H,
CH2NO2); 3.86—4.00 (m, 1 H, CHPh); 3.47 (s, 3 H, OCH3);
2.53—2.64 (m, 1 H, CHCHPh); 2.08—2.36 (m, 2 H, CH2);
1.24—1.83 (m, 6 H, CH2). 13C NMR, δ: 160.4, 138.8, 128.9,
127.9, 127.6, 98.7, 81.0, 54.2, 47.3, 44.2, 28.1, 27.2, 25.8, 24.3.
Eꢀ1ꢀMethoxyꢀ8ꢀ(2ꢀnitroꢀ1ꢀphenylethyl)cyclooctene (27a),
Rf 0.57 (AcOEt—hexane, 1 : 3), m.p. 58ꢀ59 °C. Found (%):
C, 70.29; H, 8.24; N, 4.56. C17H23NO3. Calculated (%):
C, 70.56; H, 8.01; N, 4.84. 1H NMR, δ: 7.18—7.38 (m, 5 H,
Ph); 4.80 (t, 1 H, CH=COCH3, J = 8.2 Hz); 4.64 (dd, 1 H,
CHNO2, J = 12.3 Hz, J = 4.5 Hz); 4.53 (dd, 1 H, CHNO2, J =
12.3 Hz, J = 10.5 Hz); 3.72 (dt, 1 H, CHPh, J = 4.5 Hz, J =
10.6 Hz); 3.54 (s, 3 H, OCH3); 3.01 (dt, 1 H, CHCHPh, J =

2070
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 11, November, 2006
Smirnov et al.
H(6)); 0.90 (s, 9 H, But); 0.22, 0.25 (both s, 6 H, SiMe2).
13C NMR (CD2Cl2, –63 °C), δ: 195.5 (C(8a)); 135.3 (s, Phipso);
130.0, 129.5, 128.8 (CH, Ph); 125.5 (C(3)); 66.9, 66.5 (C(11),
C(12)); 54.7, 54.8 (C(9), C(10)); 49.4 (C(4)); 42.9 (C(4a)); 31.4
(C(8)); 30.0 (C(5)); 28.0 (C(7)); 26.0 (CH3, But); 24.9 (C(13));
18.7 (C(6)); 18.6 (Cquat, But); –2.7, –3.9 (Si(CH3)2). 29Si NMR
(CD2Cl2, –63 °C), δ: 32.2.
8. M. A. Brook and D. Seebach, Can. J. Chem., 1987, 65, 836.
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74, 1894.
15. V. O. Smirnov, S. L. Ioffe, A. A. Tishkov, Yu. A. Khomutova,
I. D. Nesterov, M. Yu. Antipin, W. A. Smit, and V. A.
Tartakovsky, J. Org. Chem., 2004, 69, 8485.
This work was financially supported by the Rusꢀ
sian Foundation for Basic Research (Project Nos 03ꢀ
03ꢀ32881, 05ꢀ03ꢀ08175, and 03ꢀ03ꢀ04001), the Founꢀ
dation of the German Research Society (Deutsche
Forschungsgemeinschaft, Project No. MA 673/19), and
the Ministry of Education and Science (Target Scientific
and Technical Program, Project RIꢀ112/001/279).
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Received December 26, 2005;
in revised form September 11, 2006