Unique stereochemistry of 3-borabicyclo[3.3.1]nonane derivatives

Article abstract of DOI:10.1007/s11172-005-0057-2

The conformational equilibrium in solution was examined by NMR spectroscopy for a series of 7α-phenyl-3-borabicyclo[3.3.1]nonane derivatives containing various substituents at the boron atom. The structures of these derivatives were studied in the crystal

Full text of DOI:10.1007/s11172-005-0057-2

Russian Chemical Bulletin, International Edition, Vol. 53, No. 9, pp. 1963—1977, September, 2004
1963
Unique stereochemistry of 3ꢀborabicyclo[3.3.1]nonane derivatives
b
a
a
a
M. E. Gurskii,a K. A. Lyssenko, A. L. Karionova, P. A. Belyakov, T. V. Potapova,
ꢀ
M. Yu. Antipin,b and Yu. N. Bubnova,b
aN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5328. Eꢀmail: bor@ioc.ac.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5085. Eꢀmail: kostya@xray.ineos.ac.ru
The conformational equilibrium in solution was examined by NMR spectroscopy for a
series of 7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane derivatives containing various substituents at
the boron atom. The structures of these derivatives were studied in the crystalline state (Xꢀray
diffraction analysis) and by quantumꢀchemical calculations (B3Pw91/6ꢀ31G*). The B...Ph
transannular interactions corresponding to charge transfer from the π system of the phenyl
group to the vacant pꢀorbital of the B atom were demonstrated to be responsible for unique
stability of the chair—chair conformation of these derivatives.
Key words: 3ꢀborabicyclo[3.3.1]nonane derivatives, conformational analysis, dynamic NMR
spectroscopy, transannular interactions, Xꢀray diffraction data, quantumꢀchemical calculations.
The chemistry of compounds of the bicyclo[3.3.1]noꢀ
nane series, including those containing heteroatoms, have
attracted the attention of researchers1—3 because of their
unusual stereochemical properties, due to which they serve
as unique models for the development of theories and
concepts of stereochemistry. Compounds of this type also
find wide use in the synthesis, for example, of adamantane
The general character of these regularities was demꢀ
onstrated for a large number of bicyclo[3.3.1]nonanes conꢀ
taining various substituents.1,10—12
derivatives.4—6 In addition, azabicyclo[3.3.1]nonane is a
component of several alkaloids.7—9
According to the classical concepts of conformational
analysis,1 bicyclo[3.3.1]nonane can adopt three conforꢀ
mations free of angle strain, viz., chair—chair (CC),
chair—boat (CB), and boat—boat (BB). The chair—chair
conformation is strongly destabilized due to repulsion beꢀ
tween the 3ꢀ and 7ꢀendoꢀhydrogen atoms. As a result, the
starting bicyclo[3.3.1]nonane and its 3ꢀexo and 3ꢀexoꢀ
7ꢀexo derivatives exist predominantly in the flattened
chair—chair conformation.
The replacement of the 3ꢀmethylene group in the
bicyclo[3.3.1]nonane structure by the oxygen or nitrogen
atom leads to weakening of the intramolecular 3,7 interꢀ
actions in the chair—chair conformation. Nevertheless,
the conformational behavior of 3ꢀoxaꢀ and 3ꢀazabiꢀ
cyclo[3.3.1]nonanes obeys the same stereochemical rules
as their carbocyclic analogs.13,14
The presence of the trigonal carbon atom at position 3
(for example, in the case of the exo methylene group) also
leads to weakening of repulsion between the 3,7ꢀendoꢀH
atoms, which is thus favorable for stabilization of the
In the presence of substituents at the 3ꢀendo or 7ꢀendo
position equivalent to the axial (αꢀ) position in cyclohexꢀ
ane, this fragment assumes a boat conformation.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1884—1896, September, 2004.
1066ꢀ5285/04/5309ꢀ1963 © 2004 Springer Science+Business Media, Inc.

1964
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
Gurskii et al.
chair—chair conformation.1 Earlier, it has been reported11
that 7ꢀendoꢀhydroxyꢀ3ꢀmethylidenebicyclo[3.3.1]nonane
adopts the chair—chair conformation due to the interacꢀ
tion between the OH group and the π orbital of the double
bond. On the contrary, the chair—boat conformation
is more favorable for 7ꢀmethylideneꢀ3ꢀendoꢀmethoxyꢀ
bicyclo[3.3.1]nonane and 7ꢀendoꢀmethylꢀ3ꢀoxobiꢀ
cyclo[3.3.1]nonane.11,15
ties of 3ꢀborabicyclo[3.3.1]nonane derivatives in detail.
Recent preliminary studies of these compounds revealed
molecular dynamics associated with hindered rotation
about the B—O bond and/or the conformational equilibꢀ
rium between the CC and CB conformations.18 A series
of 7αꢀsubstituted 3ꢀborabicyclo[3.3.1]nonane derivatives
have been studied by Xꢀray diffraction analysis,19,20 which
provided direct evidence that the chair—chair conformaꢀ
tion with an axial orientation of the 7ꢀendo substituent is
more favorable.
In this connection, we performed investigation of the
structures of a series of bicyclic boron compounds, viz.,
7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane derivatives conꢀ
taining various substituents at the boron atom (1—10),
both in solution (by NMR spectroscopy) and in the solid
state (by Xꢀray diffraction analysis).
Our aim was to obtain additional data on the characꢀ
teristic structural features of bicyclic organoboranes and
make conclusions about the causes of stability of the
chair—chair conformation, although the available data
indicate that it is the unoccupied orbital of the boron
atom that is responsible for the unique stereochemical
properties of 3ꢀborabicyclo[3.3.1]nonanes, in particular,
direct transannular contacts between the atoms at posiꢀ
tions 3 and 7.
Investigations of compounds with the threeꢀcoordiꢀ
nate boron atom demonstrated that their conformational
behavior in solution is inconsistent with the aboveꢀmenꢀ
tioned stereochemical features.16—18 In particular, many
3ꢀsubstituted 3ꢀborabicyclo[3.3.1]nonanes possess unique
stereochemical properties. These compounds containing
the threeꢀcoordinate boron atom and the 7ꢀα substituent
are characterized by unpredictable and unusual stability
of the chair—chair conformation. Unfortunately, quantiꢀ
tative data on relative stabilities of the conformations have
previously been unavailable. The scope and the nature of
this new stereochemical effect have not been studied
either.
Analysis of NMR spectra
1
The use of H NMR spectroscopy in the conformaꢀ
tional analysis of bicyclo[3.3.1]nonane derivatives is based
on the known dependence of the vicinal coupling conꢀ
In recent years, considerable progress in the developꢀ
ment of dynamic NMR spectroscopy and lowꢀtemperaꢀ
ture Xꢀray diffraction techniques have provided new posꢀ
sibilities for studying the unique stereochemical properꢀ
3
stants JH,H on the dihedral angle (the Karplus equaꢀ
1
tion).21 The H NMR spectra of most of the compounds
under investigation are rather compex even when they are

Unique stereochemistry of 3ꢀborabicyclononanes
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
1965
1
Table 1. Chemical shifts (δ) in the H NMR spectra of compounds 1—10
Compound
δ
H(1), δ
δ
H(4α), δ
δ
H(4β), δ
δ
H(6α), δ
δ
H(6β), δ
δ
δ
δ
H
syn
H(5)
H(2α)
H(2β)
H(8α)
H(8β)
H(7)
H
(9)
(9)
anti
1а
2b
3а
4а
5а
6b
7b
8а
9c
2.32
2.15
2.36
2.35
1.05
2.33
1.63
1.49
1.57
1.1
1.42
1.72
0.95
2.39
2.22
2.15
1.82
2.32
1.27
2.12
1.87
2.09
2.08
1.59
2.16
2.11
3.10
2.84
3.03
2.88
3.15
2.83
2.77
2.87
2.89
2.99
1.92
1.71
1.89
1.8
1.28
1.98
1.89
2.12
1.95
2.11
1.58
1.41
1.47
1.4
1.16
1.23
1.26
1.32
1.15
1.39
0.72
1.11
0.8
0.39
1.02
2.30 and 2.36 0.71 and 1.15—1.21 0.77 and 0.89 1.15—1.21
2.42
2.45
2.55
0.88
1.08
1.22
0.54
0.79
2.15
1.95—2.07
1.69
1.95—2.07
2.03
10c
0.68
2.11
a CDCl3.
b Tolueneꢀd8.
с Pyꢀd5.
Table 2. Absolute values of the coupling constants (J/Hz) for compounds 1—10
2
2
3
3
Comꢀ
pound
2JH(2α),H(2β) JH(4α),H(4β) JH(6α),H(6β) 2JH
3JH(6α),H(7β) JH(6β),H(7β) JH(2β),H(1) 3JH(6α),H(5) 3JH(6β),H(5)
(9),H (9)
anti
syn
1а
2b
3а
4а
5а
6b
7b
8а
9c
—
—
—
—
—
—
15.62
—
—
—
17.67
17.41
18.02
17.32
17.15
18.03
15.22
13.21
13.07
16.78
14.25
13.98
14.42
13.8
13.97
14.05
—
13.62
13.51
13.7
12.6
5.4
5.96
5.61
6.5
5.4
9.9
11.61
12.82
13.1
11.8
5.06
—
5.6
6.5
—
5.5
5.21
5.6
5.6
5.7
—
5.5
6.01
—
—
5.61
6.01
4.8
5.65
2.09
—
—
—
—
—
3.52
—
—
—
—
—
—
—
8.61
—
—
10.88
—
12.37
13.01
12.76
12.35
12.95
12.82
12.81
12.73
12.6
3.54
3.2
10c
a CDCl3.
b Tolueneꢀd8.
с Pyꢀd5.
recorded at 400—500 MHz due to overlap of signals. Howꢀ
ever, the fine structure of the signals for H(7β) is observꢀ
able in almost all spectra, which allows one to unambiguꢀ
ously establish the major conformation of the cyclohexꢀ
ane fragment. The chemical shifts and the coupling conꢀ
stants of the compounds under study are given in Tables 1
and 2, respectively. The assignment of the signals in the
spectra was made using twoꢀdimensional NMR techniques
(1H—1H COSY and NOESY) and by comparing with the
spectra of related compounds.16—18
to the chair—chair conformation of the 3ꢀborabiꢀ
cyclo[3.3.1]nonane derivatives of this group.*
The presence of the axial substituent is the most surꢀ
prising structural feature of these compounds, which
distinguishes them from other compounds of the biꢀ
cyclo[3.3.1]nonane series, particularly taking into account
the conformational energy of the phenyl group (accordꢀ
ing to different estimates, for phenylcyclohexane this enꢀ
ergy varies from 11.29 to 12.29 kJ mol–1).
The action of a complexꢀforming agent (pyridine) on
bicyclic compounds 9 and 10 results in a substantial inꢀ
The structures given in Tables 1 and 2 can be divided
into two groups. For compounds 1—5, the signal for the
3
crease in the coupling constant J6α,7 from 6 to 11 Hz,
proton at C(7) appears as a broadened triplet of triplets
* A chairꢀlike conformation of the borinane ring is evidenced by
3
with equal coupling constants (3J7 ,6
≈ J7 ,6 (8 )
<
β
α
α
β β β
(8
)
the coupling constants JH(2α),H(1) (3JH(4α),H(5)) and JH(2β),H(1)
(3JH(4β),H(5)), which are ~6 Hz for all the compounds under
study. If the borinane ring adopts a boat conformation, the
1H NMR spectrum would have a larger coupling constant
3JH(2β),H(1) (3JH(4β),H(5) >10 Hz), because the corresponding diꢀ
hedral angle in this case is close to 0°.
3
3
< 6.5 Hz) (Fig. 1).
These vicinal coupling constants correspond to the
equatorial arrangement of the H(7) atom and the axial
orientation of the phenyl group in the chairꢀlike cycloꢀ
hexane moiety of the bicyclic cage and, consequently,

1966
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
Gurskii et al.
2
3
4
3.00
2.95
δ
3.10
3.05
δ
2.90
2.85
δ
Fig. 1. Proton resonance region for H(7) in the 1H NMR spectra of compounds 2—4.
which suggests an increase in the content of the conꢀ
former with the axial H(7) atom, i.e., the boat conformaꢀ
tion of the cyclohexane ring (see Table 2).
tional behavior of these compounds is very similar to that
of the carbon analogs. 3ꢀtertꢀButylꢀ7αꢀphenylꢀ3ꢀborabiꢀ
cyclo[3.3.1]nonane (6) containing the bulky substituent
at position 3 is the only representative of 7αꢀphenylꢀ3ꢀ
borabicyclo[3.3.1]nonane derivatives with the threeꢀcoꢀ
ordinate boron atom, which exists predominantly in the
chair—boat conformation.
According to the published data, the 13C chemical
shifts of the signals for the C(9) atom of the biꢀ
cyclo[3.3.1]nonane system are characteristic for the deꢀ
termination of the prevailing conformation of the bicyclic
fragment.22 The transition from the CC to the CB conforꢀ
mation is accompanied by a substantial upfield shift of the
signal for the C(9) atom. The 13C chemical shifts for
3ꢀborabicyclo[3.3.1]nonane derivatives are given in
Table 3. The chemical shifts of the C(9) atoms for comꢀ
pounds 1—4 lie in a range of δ 34—37. In the spectra
of compounds belonging to the second group (comꢀ
pounds 6—10), the signals for C(9) are shifted upfield
(δ 31—33). It is reasonable to assume that, by analogy
with a number of bicyclo[3.3.1]nonanes, this is associated
with a change in the conformation from CC to CB.
The second group involves compounds 6—10 existing
predominantly in the chair—boat conformation, as unꢀ
ambiguously evidenced by the large coupling constant
(10—14 Hz) between H(7) and H(6α), i.e., by the fact that
the corresponding dihedral angle is close to 180° (Fig. 2).
This group includes primarily compounds containꢀ
ing the fourꢀcoordinate boron atom with the filled
vacant orbital (3ꢀmethylaminoꢀ7αꢀphenylꢀ3ꢀborabiꢀ
cyclo[3.3.1]nonane (7) is characterized by completely hinꢀ
dered rotation about the B—N bond). The conformaꢀ
6
7
8
2.85
2.80
δ
2.85
2.80
δ
2.90
2.85
δ
Fig. 2. Proton resonance region for H(7) in the 1H NMR spectra of compounds 6—8.

Unique stereochemistry of 3ꢀborabicyclononanes
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
1967
Table 3. Chemical shifts (δ) in the 13C NMR spectra of compounds 1—10
Comꢀ C(1), C(5)
pound
C(2), C(4)
C(6), C(8)
C(7)
C(9)
Other
1а
2b
28.7
28.74
37.1
35.31
35.8
35.31
34.5
34.35
37.1
129.06, 129.02, 126.38, 143.9, 11.37 (Me)
37.55 126.92, 129.53, 129.60, 143.9, 5.31 (CH2—CH=),
113.6 (CH=CH2), 138.1 (—CH=)
3а
4а
5а
6b
7b
8а
27.46
27.7
32.2
36.18
29.0
42.4
35.12
36.9
40.2
33.56
34.85
34.85
35.99
34.39 125.84, 127.2, 128.35, 142.63
34.4
51.9
128.3, 127.7, 125.7, 145.2, 52.8
8.9, 125.94, 128.53, 129.02, 140.4
26.66
34.22
38.77
32.34 125.83, 127.34, 128.56, 146.72, 26.42
33.23 37.75, 126.81, 128.50, 129.37, 148.53
31.61 108.67, 110.50, 122.36, 125.34, 127.75, 128.02, 128.36,
132.60, 137.10, 137.23, 137.64, 149.41, 159.09
31.54 124.93, 127.03, 127.72,
28.55 and 28.53 26.84 and 30.87 39.81 and 40.15 30.01
27.13
33.5
36.43
37.96
9c
10c
27.8
28.28
33.27
29.09
36.23
36.44
37.76
38.11
33.22 123.99, 128.24, 128.72
a CDCl3.
b Tolueneꢀd8.
с Pyꢀd5.
It is quite evident that the preponderance of the
chair—chair conformation for compounds 1—6 reflects
the energy compromise between the strain associated with
steric repulsions of the 3,7ꢀendoꢀH atoms and the specific
intramolecular attractive interaction between the vacant
2p orbital of the boron atom and the substituent at the
7ꢀendo position. The results of Xꢀray diffraction analysis
considered below provide direct evidence for this interꢀ
action.
3ꢀborabicyclo[3.3.1]nonane, we carried out Xꢀray diffracꢀ
tion studies of derivatives 2, 4, 7, and 8.
Earlier,19,20 we have demonstrated that molecules 1
and 3 in crystals adopt the CC conformation stabilized by
transannular B...Ph interactions (Fig. 3). This conclusion
was made both based on analysis of the geometry and
investigation of the electron density distribution19,20 in
terms of Bader's theory of Atoms in Molecules (AIM).23
Analysis of the geometry revealed the presence of rather
short intramolecular B(3)...C(10) contacts in both strucꢀ
tures and demonstrated that the phenyl substituent is virꢀ
tually parallel to the C(2)B(3)C(4) plane. Shortening
of the B...C contact is accompanied by substantial
pyramidalization of the B atom, which deviates (dB) from
the plane passing through the atoms involved in its enviꢀ
Xꢀray diffraction study
and quantumꢀchemical calculations
To estimate the influence of the nature of the substituꢀ
ent at the boron atom on the conformation of 7αꢀphenylꢀ
Cl(1)
B(3)
C(4)
B(3)
C(10)
C(2)
C(10)
C(4)
C(5)
C(2)
C(5)
C(6)
C(7)
C(1)
C(6)
C(7)
C(9)
C(1)
C(8)
C(8)
C(9)
1
3
Fig. 3. Crystal structures of compounds 1 and 3.

1968
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
Gurskii et al.
Table 4. Selected geometric parameters of the molecules in the crystalline and isolated states and the energy differences between the
Comꢀ
pound
Substiꢀ
tuent (X)
at atom B
Conforꢀ
mation
Method
Distance/Å
B(3)...C(10)
B(3)—C(2)
(B(3)—C(4))
B—X
C(7)—C(10)
1
Me
CC
CC
CB
CC
CC
CB
CB
CC
CB
CB
CC
CB
Xꢀray f
QCCg
QCC
Xꢀray
Xꢀray
Xꢀray
QCC
QCC
Xꢀray
QCC
QCC
Xꢀray
1.575(3)
1.581
1.581
1.598(4)
1.559(1)
1.574(2)
1.585
1.585
1.590(2)
1.591
1.593
1.598(3)
2.983(1)
3.026
—
2.996(4)
2.908(1)
—
—
3.179
—
1.569(3)
1.576
1.576
1.594(5)
1.782(1)
1.358(2)
1.363
1.363
1.391(2)
1.409
1.409
1.619(3) N(1)
1.550(3) O(1)
1.538(3)
1.535
1.519
1.558(4)
1.5322(8)
1.514(2)
1.516
1.531
1.515(2)
1.519
1.538
1.505(3)
2
3
4
All
Cl
OMe
7
NHMe
quin
—
3.113
—
8h
a The angle between the B(3)...C(10) line and the plane of the phenyl ring.
b The deviation of the boron atom from the plane passing through the C(2), C(4), and X atoms.
c The deviation of the C(10) atom from the plane passing through the C(11), C(7), and C(15) atoms.
d The deviation of the B(3) atom from the C(1)C(2)C(4)C(5) plane.
e The deviation of the C(9) atom from the C(1)C(2)C(4)C(5) plane.
f Data from Xꢀray diffraction study.
g Results of quantumꢀchemical calculations.
h For compound 8, the average values for three independent molecules are given.
ronment toward the phenyl substituent (Table 4). It should
be noted that, on the contrary, the deviation of the
ipsоꢀC(10) atom of the phenyl ring (dC) from the plane
passing through the C(6), C(11) and C(15) atoms toward
the B(3) atom decreases.
presence of substituents at the boron atom that can comꢀ
pete with the phenyl πꢀsystem and shield the vacant orꢀ
bital of the boron atom, thus weakening the B(3)...C(10)
dative interaction.
Xꢀray diffraction study of compounds 2, 4, and 7 demꢀ
onstrated that the 3ꢀborabicyclo[3.3.1]nonane fragment
adopts the CC conformation only in 2 (Fig. 4), whereas
the CB conformation is observed in 4 and 7 as well as in
compound 8 containing the fourꢀcoordinate boron atom
(Figs 4 and 5).
Taking into account that the preponderance of a parꢀ
ticular conformation in the crystal can be associated with
the crystal packing effects, we performed quantumꢀchemiꢀ
cal calculations (B3PW91/6ꢀ31G(d)) for both conformaꢀ
tions of compounds 1, 4, and 7.
The functional and the basis set used in these calcuꢀ
lations adequately reproduce the experimental geomꢀ
etry (see Table 4). Small elongation of the B...C contact
agrees well with the known dependence of the dative inꢀ
teractions on the polarity of the environment. Earlier,24,25
the lengths of dative contacts and, particularly, bond
lengths in donorꢀacceptor boron complexes in the gasꢀ
eous phase have been demonstrated to be systematiꢀ
cally larger that the corresponding values in the crystalꢀ
line state.
Since the geometric parameters serve only as indirect
evidence for the specific interactions, we carried out toꢀ
pological analysis of the electron density distribution funcꢀ
tion ρ(r), which was determined based on the results of
quantumꢀchemical calculations without geometry optiꢀ
mization of 1,19 and the data from highꢀprecision Xꢀray
diffraction for compound 3.20 It was shown that the critiꢀ
cal point (CP) (3, –1) in both molecules is localized in
the region of the interatomic B(3)...C(10) contact. Acꢀ
cording to the AIM23 theory, this critical point serves as
the criterion of chemical bonding. The nature of this inꢀ
teraction was studied in detail using compound 3 as an
example. Analysis of the deformation electron density
distribution, the Laplacian of the electron density, and
the electron localization function (ELF) demonstrated
that this interaction corresponds to charge transfer from
the π system of the phenyl fragment to the vacant orbital
of the boron atom.20 It should be noted that the critical
point (3, –1) in compound 1 was revealed not only in the
region of the B...C interaction but also in the region of the
C—H...Ph contact19 (see Fig. 3).
A comparison of the energies of the CC and CB conꢀ
formations showed that the conformation of the bicyclic
fragment observed in the crystals of compounds 1, 4,
It was of interest to analyze the changes in the characꢀ
ter and strength of the B(3)...C(10) interaction in the

Unique stereochemistry of 3ꢀborabicyclononanes
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
1969
conformations (∆E) according to the results of B3PW91/6ꢀ31G(d) calculations
a
Angle/deg
d/Å
α
∆E
/kJ mol–1
/deg
b
c
d
e
C(11)—C(10)—C(15) C(2)—B(3)—C(4)
dB
dC
d1
–d2
116.9(2)
116.7
117.9
115.9(3)
116.95(5)
117.8(1)
117.9
117
117.9(1)
117.9
116.9
117.7(3)
117.0(2)
117.4
117.8
116.8(3)
121.21(5)
120.3(1)
119
119.4
117.2(1)
117.2
118.4
113.6(2)
0.076
0.0677
0.032
0.0684
0.0921
0.0425
0.0334
0.0627
0.0142
0.009
0.0478
—
0.052
0.0521
0
0.0483
0.0473
0.0142
0
0.0432
0
0
0.299
0.273
0.3
0.75
0.75
0.76
0.76
0.76
0.76
0.76
0.76
0.75
0.76
0.76
0.75
73
80.2
—
83
82
—
—
64.3
—
—
0
1.0385
—
—
—
0
2.4359
—
—
0.29
0.27
0.245
0.38
0.26
0.45
0.48
0.3
—
79
—
0.0476
0.018
8.74
—
0.51
and 7 corresponds to the energy minimum, although the
energy difference between CC and CB in 1 and 4 is small.
The shortest B...C contact (2.908(1) Å) is observed in
compound 3 (see Table 4), whereas the corresponding
contacts in 4 and 7 (according to the results of calculaꢀ
tions by the B3PW91/6ꢀ31G(d) method) are substantially
longer (3.179 and 3.113 Å, respectively). Small elongaꢀ
tion of the B(3)...C(10) contact in 2 compared to that in 1
is apparently associated with an increase in steric repulꢀ
sion due to the allylic substituent.
C(20)
C(19)
C(21)
C(18)
C(13)
C(18)
C(22)
C(17)
C(14)
C(17)
C(23)
C(24)
C(16)
C(16)
B(3)
C(15)
C(12)
C(11)
O(1)
N(1)
C(4)
C(4)
B(3)
C(10)
C(6)
C(2)
C(6)
C(2)
C(1)
C(15)
C(11)
C(7)
C(14)
C(13)
C(5)
C(5)
C(9)
C(8)
C(7)
C(8)
C(10)
C(1)
C(9)
C(12)
2
8
Fig. 4. Crystal structures of compounds 2 and 8.

1970
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
Gurskii et al.
C(16)
O(1)
B(3)
C(16)
N(1)
B(3)
C(4)
C(2)
C(4)
C(2)
C(1)
C(11)
C(11)
C(12)
C(13)
C(12)
C(13)
C(8)
C(8)
C(7)
C(6)
C(1)
C(9)
C(5)
C(9)
C(5)
C(7)
C(10)
C(10)
C(15)
C(6)
C(14)
C(14)
C(15)
4
7
Fig. 5. Crystal structures of compounds 4 and 7.
Topological analysis of ρ(r) revealed charge transꢀ
fer from the π system to the vacant orbital of B(3) in
all compounds, including 4 and 7, which exist in
the CC conformation. However, the values of ρ(r)
(0.047—0.075 eÅ–3) at the corresponding critical points
(3, –1) in 4 and 7 are somewhat smaller. It should be
noted that there are no C—H...π interactions in comꢀ
pounds 4 and 7 (see Fig. 3). Estimation of the energy
of intramolecular interactions based on the potential enꢀ
ergy densities at the critical points (3, –1)26—28 demonꢀ
strated that the energy of interactions in 2 is virtually
twice as high as that in 4 (7.94 and 4.18 kJ mol–1, respecꢀ
tively).
tacts, because pyramidalization is observed in the case of
the chair—boat conformation as well (except for comꢀ
pound 7).
On the contrary, the geometric parameters describing
the phenyl substituent are more sensitive to the conforꢀ
mational changes. A weak B(3)...C(10) dative interaction
in the CC conformation leads to substantial elongation of
the C(7)—C(10) bond (1.532—1.538 Å) compared to that
observed in the CB conformation (1.505—1.515 Å).
Analogous differences are observed also for the
ipsoꢀC(11)C(7)C(15) angle and the distance dC.
The conformation of the sixꢀmembered boronꢀconꢀ
taining ring is also rather sensitive to the nature of the
substituent at the boron atom. The deviation of the boron
atom from the C(1)C(2)C(4)C(5) (d1) plane in 7 is as
high as 0.45 Å and is virtually equal to the corresponding
value in 8 (0.51 Å), whereas the boat conformation in the
other structures is more flattened and d1 varies within a
rather narrow range of 0.24—0.30 Å.
Therefore, the replacement of the alkyl substituent at
the boron atom in 7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane
by the methoxy or methylamino group leads to weakening
of the B...Ph dative interaction, which appears to be suffiꢀ
cient for a decrease in the portion of the CC conformaꢀ
tion in the CC
CB equilibrium.
It should be noted that a substantial conjugation of the
lone electron pair of the nitrogen atom with the vacant
orbital of the B(3) atom in compound 7 follows also from
the analysis of the geometry. The N(1) atom is characterꢀ
ized by a planarꢀtrigonal configuration (the sum of
the bond angles at the N(1) atom is 359.9°), and the
B(3)—N(1) (1.391 Å) bond angle falls within a range of
values typical of aminoboranes.29
A comparison of the geometry of 7αꢀphenylꢀ3ꢀboraꢀ
bicyclo[3.3.1]nonane derivatives in the CC and CB
conformations demonstrated that the B—X and B—C
bond lengths, as well as the parameters describing disꢀ
tortions of the environment about the B atom, reꢀ
main virtually unchanged. In particular, the degree of
pyramidalization of the B(3) atom cannot be considered
as a reliable criterion of the presence of transannular conꢀ
Other bond lengths and bond angles in the bicycles are
virtually independent of the nature of the substituent at
the B(3) atom. In particular, the deviations of the C(9)
and C(7) atoms from the C(1)C(5)C(6)C(8) plane in the
compounds under study remain virtually constant (0.71,
–0.62 Å and 0.68, 0.66 Å in the CC and CB conformaꢀ
tions, respectively).
The geometric parameters in 8, including the
B(3)—N(1) and B(3)—O(1) bond lengths, are close
to the corresponding values in 7αꢀmethylꢀ3ꢀborabiꢀ
cyclo[3.3.1]nonꢀ3ꢀyl quinolinꢀ8ꢀolate.30
Analysis of the contacts in the crystal packings of 2, 4,
7, and 8 showed that all intermolecular contacts correꢀ
spond to usual van der Waals interactions, and no shortꢀ
ened intermolecular contacts are present even in the crysꢀ
tals of 7 containing the MeNH group.

Unique stereochemistry of 3ꢀborabicyclononanes
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
1971
Therefore, the Xꢀray diffraction studies and quantumꢀ
chemical calculations demonstrated that the chair—chair
conformation in the series of 7αꢀphenylꢀ3ꢀborabiꢀ
cyclo[3.3.1]nonane derivatives is stabilized owing to weak
B...Ph dative interactions. The contribution of these inꢀ
teractions is determined primarily by the electrophilic
characteristics of the boron atom (the occupancy of the
vacant 2p orbital of the B atom) rather than by steric
factors.
To obtain direct supproting evidence for the role of
dative interactions, we performed calculations for two
model compounds containing the methyl group at the
boron atom and the pꢀaminophenyl or pꢀnitrophenyl subꢀ
stituent at position 7. Calculations by the B3Pw91/6ꢀ31G*
method demonstrated that the B(3)...C(10) distances and
the distances dB in 1 and the model compounds are slightly
different, the steric characteristics of the groups at posiꢀ
tions 3 and 7 remaining unchanged. For example, the
B(3)...C(10) distance in the 4ꢀamino derivatives decreases
to 2.983 Å, whereas deactivation of C(10) in the 4ꢀnitro
compound leads to elongation of the corresponding disꢀ
tance to 3.076 Å (for comparison, the corresponding disꢀ
tance in isolated molecule 1 is 3.026 Å).
the conformational equilibrium.31 At 303 K, the ratio
between the CC and CB conformations of compound 1 is
76 : 24, which corresponds to ∆G° = 2.84 kcal mol–1
.
Examination of the 13C and H NMR spectra in a
wide temperature range (163—373 K) demonstrated that
an increase in the temperature leads to a shift of this
equilibrium toward the chair—chair conformation. This
1
1
is manifested in the fact that the H chemical shift of
the the methyl group in the spectrum of compound 1
changes with temperature. In the CC conformation, the
protons of the methyl group are located close to the cenꢀ
ter of the plane of the phenyl ring and should be strongly
shielded due to magnetic anisotropy. At 303 K, δCH
3
is 0.065, and this signal is shifted to δ –0.5 as the temperaꢀ
ture decreases to 193 K. For 3ꢀmethylꢀ7ꢀphenylꢀ3ꢀborabiꢀ
cyclo[3.3.1]nonꢀ6ꢀene (11), in which the methyl group is
virtually unaffected by ring currents of the phenyl group,
δCH = 0.63. The temperature dependence of the chemiꢀ
3
cal shift of the protons of the methyl group of compound 1
(Fig. 6) is consistent with the theoretically expected exꢀ
ponential dependence due to the shift of the equilibꢀ
rium and the inverse dependence on the cube of the disꢀ
tance to the plane of the phenyl ring.
Due to rapid exchange between the CC and CB conꢀ
formations, the 1H NMR spectrum has only one averaged
signal of the methyl group, whose chemical shift (δ) deꢀ
pends on the equilibrium constant determined from the
equation
Dynamic processes in
3ꢀborabicyclo[3.3.1]nonane derivatives
1. Conformational equilibria. Bicycloboranes 1—6 posꢀ
sess high conformational lability, which is manifested in
the equilibria characteristic of bicyclo[3.3.1]nonane deꢀ
rivatives.
K = (δCB – δ)/(δ – δCC).
(1)
Assuming that δCC and δCB are independent of the
temperature in the temperature range used, these paramꢀ
eters were varied in such a way as to achieve the linear
dependence of lnK on 1/T, and then K was calcuꢀ
lated by Eq. (1). The following values were obtained:
δ(B—Me)
–0.1
δ
δ
Me (303 K) 0.065
Me (193 K) –0.5
δMe (303 K) 0.65
–0.2
–0.3
–0.4
–0.5
–0.6
In the 1H NMR spectrum of compound 2 (303 K), the
signal for the H(7) atom appears as a broadened triplet of
triplets with the equal coupling constants 3J7 ,6α ≈ 3J
6 Hz, whereas the calculated coupling constants for the
geometry determined from the Xꢀray diffraction data for
the chair—chair conformation are J7 ,6α(72°) = 1.56 Hz
≈
β β
7 ,6
β
3
β
and 3J7β,6β(42°) = 5.71 Hz. On the other hand, the correꢀ
sponding experimental coupling constants for deuterioꢀ
pyridine complex 9, which adopts the chair—boat conꢀ
formation, are 3J7β,6α = 13.1 Hz and 3J7β,6β = 5.6 Hz.
Based on these data for the CC and CB conformaꢀ
tions, one can estimate the fractions of the conformers in
150
200
250
T/K
Fig. 6. Temperature dependence of the chemical shift of the
protons of the methyl group in the H NMR spectrum of comꢀ
pound 1.
1

1972
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
Gurskii et al.
δCC = –0.625 0.005, δCB = 0.837 0.005, ∆H° =
7.9 0.2 kJ mol–1, ∆S° = 20.4 0.5 J mol–1 K–1
.
A decrease in the temperature leads to insignificant
changes in the chemical shifts in the 11B NMR spectra of
these compounds. For example, cooling of a solution of
compound 1 from 298 to 213 K results in ∆δ of 1.3 ppm
(δ changes from 82.0 to 80.7).
2. Hindered rotation about the BO (or BN) bond.
Investigation of the 13C NMR spectra of 3ꢀmethoxyꢀ7αꢀ
phenylꢀ3ꢀborabicyclo[3.3.1]nonane 4 in a wide temperaꢀ
ture range revealed molecular dynamics associated with
hindered rotation of the methoxy group about the B—O
bond. This is clearly evident from the fact that certain
carbon atoms (C(2), C(4); C(1), C(5); C(6), C(8)) beꢀ
come nonequivalent in the 13C NMR spectra as the temꢀ
perature decreases (a double set of signals in a ratio
of 1 : 1) (Fig. 7).
The barrier to rotation about the B—O bond is attribꢀ
utable to πꢀbonding of the vacant 2p orbital of the boron
atom with the lone electron pair of the oxygen atom.
The activation parameters for this process, which were
determined by analyzing the line shapes, are as follows:
For
3ꢀmethylaminoꢀ7αꢀphenylꢀ3ꢀborabicycꢀ
lo[3.3.1]nonane (7), complete inhibition of free rotation
about the B—N single bond is observed at room temperaꢀ
ture. This is clearly evident from the nonequivalence of
certain carbon atoms (C(2), C(4); C(1), C(5); C(6), C(8))
in the 13C NMR spectrum and the corresponding hydroꢀ
∆H# = 56.6 0.9 kJ mol–1; ∆S# = 19.7 4.3 kJ mol–1 K–1
;
∆G# = 50.8 0.9 kJ mol–1. According to the published
298
data,32 the measured barriers to rotation about the B—O
bond are in a range of 55.6—54.2 kJ mol–1
.
gen atoms in the H NMR spectrum (a double set of the
1
Interestingly, ∆H# for 3ꢀmethoxyꢀ7ꢀphenylꢀ3ꢀboraꢀ
bicyclo[3.3.1]nonꢀ6ꢀene (12) characterized by weaker
endocyclic interactions is also substantially lower.
signals in a ratio of 1 : 1). According to the published
data,33 the barrier to rotation about the B—N bond in
(dimethylamino)methyl(phenyl)borane is 111.2 kJ mol–1
.
213 K
217 K
223 K
227 K
233 K
237 K
243 K
247 K
253 K
257 K
263 K
267 K
C(2) C(4)
C(5)
C(8)
36
C(9)
34
C(1)
273 K
40
38
32
30
28
26
24
22
δ
Fig. 7. Temperature dependence of the 13C NMR spectra of 3ꢀmethoxyꢀ7ꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonꢀ6ꢀene (12).

Unique stereochemistry of 3ꢀborabicyclononanes
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
1973
in the chair—chair conformation, in particular, the interꢀ
actions between the vacant p orbital of the boron atom
and the substituent at position 7, the thermodynamic paꢀ
rameters of the CC
CB conformational equilibria,
These results provide an explanation for the Xꢀray
diffraction data for compounds 4 and 7. Overlap of the
vacant 2p orbital of the boron atom with the electron pair
of the oxygen or nitrogen atom leads to the disappearance
of an interaction between boron and the 7ꢀendo substituꢀ
ent and destabilization of the chair—chair conformation.
The results of the present study unambiguously show
that the sterically hindered chair—chair conformations
of 3,7ꢀendoꢀdisubstituted compounds of the 3ꢀborabiꢀ
cyclo[3.3.1]nonane series can be stabilized due to the
specific interaction between the vacant p orbital of the
boron atom and the π electrons of the 7ꢀendoꢀphenyl
group.
and the influence of these equilibria on other processes of
molecular dynamics (hindered rotation about the B—O
bond and the [1,3]ꢀshift of boron in 3ꢀallylꢀ3ꢀboraꢀ
bicyclo[3.3.1]nonane derivatives).
Experimental
All operations with organoboron compounds were carꢀ
ried out under dry argon. The 1H, 13C, and 11B NMR spectra
were recorded on Bruker ACꢀ200P (200.13 MHz for 1H,
50.32 MHz for 13C, and 64.21 MHz for 11B), Bruker AMXꢀ400
(400.13 MHz for 1H and 100.13 MHz for 13C), and Bruker
DRXꢀ500 (500.13 MHz for 1H and 125.75 MHz for 13C) instruꢀ
ments.
3. Permanent allylic rearrangement. As in other allylꢀ
boranes, the [1,3]ꢀsigmatropic shift of boron, viz., the
permanent allylic rearrangement,5 is observed in 7αꢀsubꢀ
stituted 3ꢀallylꢀ3ꢀborabicyclo[3.3.1]nonane derivatives.
Stereochemical nonrigidity of these bicyclic comꢀ
pounds is responsible for a substantial influence of conꢀ
formational equilibria on the thermodynamic paramꢀ
eters of the rearrangement. The activation parameters
for 3ꢀallylꢀ7αꢀmethylꢀ3ꢀborabicyclo[3.3.1]nonane (13)
3ꢀMethylꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane (1),19
3ꢀmethoxyꢀ7ꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonꢀ6ꢀene (12),37
3ꢀchloroꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane
(3),37
3ꢀmethoxyꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane (4),37 and
3ꢀmethoxyꢀ1,5ꢀdimethylꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]noꢀ
nane18 were synthesized according to procedures described
earlier.
The complexes of 3ꢀmethoxyꢀ and 3ꢀmethylꢀ7αꢀphenylꢀ3ꢀ
borabicyclo[3.3.1]nonane with pyridineꢀd5 (9 and 10) were preꢀ
pared by dissolution of the borabicyclic compounds in an excess
of the ligand (Pyꢀd5).
(∆G≠
= 73.7 kJ mol–1) and 3ꢀallylꢀ7αꢀphenylꢀ3ꢀ
298
borabicyclo[3.3.1]nonane (2) (∆G≠
= 72.6 kJ mol–1
)
298
Xꢀray diffraction study of compounds 2, 4, 7, and 8. Single
crystals of compounds 2 and 7 suitable for Xꢀray diffraction
study were grown by slow cooling of a melt. Single crystals of
chelate compound 8 were prepared by recrystallization from
diethyl ether. Bicyclic compound 4 crystallized spontaneously
(after storage for 6 months).
were measured using 2D NMR spectroscopy with chemiꢀ
1
cal exchange34 (2D H—1H ESXY). These values are
the highest of all the known parameters for allylic triꢀ
organoboranes, except for allyldimesitylborane (14), in
which the allylic rearrangement was not observed up
to 140 °C.36
The structures were solved by direct methods and refined
against F 2 by the leastꢀsquares method with anisotropic disꢀ
Hence, 3,7ꢀdisubstituted 3ꢀborabicyclo[3.3.1]nonanes
hkl
are unique models for studying transannular interactions
placement parameters for nonhydrogen atoms. The hydrogen

1974
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
Gurskii et al.
Table 5. Main crystallographic parameters and details of refinement
Parameter
2
4
7
8
Molecular formula
Molecular weight
Crystal system
Space group
C
238.16
Triclinic
17H23
B
C15H21BO
228.13
Monoclinic
P21/c
C15H22BN
227.15
Monoclinic
P21/c
C23H24BNO
341.24
Triclinic
–
P1
–
P1
T/K
Diffractometer
Z (Z´)
120
«SMART CCD»
2 (1)
110
120
298
«Siemens P3»
6 (3)
«SMART CCD»
4 (1)
«SMART CCD»
4 (1)
a/Å
b/Å
с/Å
α/deg
7.449(5)
9.544(7)
11.940(9)
69.44(2)
82.32(3)
67.32(2)
733.4(9)
1.079
7.761(3)
15.576(6)
10.726(4)
—
96.741(9)
—
1287.8(8)
1.177
0.70
15.157(3)
7.318(2)
12.538(2)
—
111.781(8)
—
1291.4(4)
1.168
0.66
10.445(2)
15.338(3)
19.037(4)
76.04(3)
77.67(3)
78.13(3)
2853.0(10)
1.192
β/deg
γ/deg
V/Å3
dcalc/g cm–3
µ/cm–1
0.59
0.71
F(000)
260
496
496
1092
Scanning mode
ω
ω
ω
ω
2θmax/deg
52
60
60
50
Number of measured reflections
4231
9919
7490
10016
Number of independent reflections
2728
3609
3666
9420
Number of reflections with I > 2σ(I )
1699
2889
2656
4825
Rint 0.0481
Number of parameters
in refinement
GOOF
0.0312
255
0.0265
250
0.0383
242
703
0.977
0.0741
1.075
0.0528
1.008
0.0597
0.923
0.0437
R1
wR2
0.1699
0.1298
0.1426
0.0978
Residual electron
–0.19/0.20
0.37/–0.28
0.49/–0.21
0.24/–0.18
density/e•Åꢀ3 (dmin/dmax
)
atoms in compounds 2, 4, and 7 were located from difference
Fourier maps and refined isotropically. In compound 8, the
positions of the hydrogen atoms were calculated geometrically
and refined using the riding model. The main crystallographic
parameters and details of the refinement are given in Table 5. All
calculations were carried out on an IBMꢀPC/AT using the
SHELXTL PLUS program package.
Determination of the activation parameters for rotation of the
methoxy group in 3ꢀborabicyclo[3.3.1]nonane derivatives. The
data from the NMR experiments were processed with the use of
the standard Bruker software (DISNMR on ASPECTꢀ3000 with
the Adakos OS, XWINNMR on IBMꢀcompatible personal comꢀ
puters with the Linux OS) and programs for recording and autoꢀ
matic processing the DNMR spectra (GlobalꢀDNMR) develꢀ
oped by us.
The full shapes of the resonance lines were analyzed using
the DYNNMR program.40 The crossꢀrelaxation times were meaꢀ
sured at each temperature point.
Quantumꢀchemical calculations were carried out using the
Gaussian 98W program38 with the B3PW91 hybrid functional
and the 6ꢀ31G(d) basis set. Topological analysis of the theoretiꢀ
cal (calculated) electron density distribution was performed with
the use of the EXTREME program.39
compound 7 (5.35 g, 23 mmol). The reaction mixture was heated
at 100 °C for 1 h. Then methanol was distilled off in vacuo
(15 Torr, 20 °C). Distillation of the residue afforded product 15
in a yield of 5.8 g (84.6%), b.p. 155—156 °C (1.5 Torr).
Found (%): C, 80.54; H, 10.48; B, 3.62. C20H31BO. Calcuꢀ
lated (%): C, 79.98; H, 10.45; B, 3.42. 1H NMR (CDCl3), δ:
0.8—0.91 (dd, 2 H, H(2β), H(4β), 2J = 16.54 Hz); 0.91—1.00 (t,
3 H, (CH3), J = 6.61 Hz); 1.05—1.20 (d, 2 H, H(2α), H(4α),
2J = 16.54 Hz); 1.40—1.55 (m, 9 H, Hsyn(9), H(CH2)4);
1.85—2.05 (m, 3 H, Hanti(9), H(6α), H(8α)); 2.10—2.30 (m,
2 H, H(6β), H(8β), 2J = 13.97 Hz); 2.35—2.55 (m, 2 H,
H(1), H(5)); 2.95—3.15 (m, 1 H, H(7)); 3.60—3.70 (t, 2 H,
H(—O—CH2), 2J = 6.61 Hz); 7.25—7.40 (m, 5 H, Ph).
13C NMR (CDCl3), δ: 13.96 (C(Me)); 22.57 (C(5´)); 25.48
(C(4´)); 27.11 (C(1), C(5)); 27.74 (C(2), C(4)); 31.36 (C(9));
31.58 (C(7)); 33.27 (C(3´)); 35.02 (C(2´)); 37.36 (C(6), C(8));
65.18 (C(1´)); 125.35, 127.18, 127.93, 145.81 (Ph).
3ꢀAllylꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane (2). A mixture
of compound 15 (5.8 g, 19 mmol) and allyl bromide (2.35 g,
19 mmol) was added dropwise to a suspension of a Mg powder
(0.449 g, 19 mmol) in Et2O (20 mL). The reaction mixture
was refluxed for 4 h. The diethyl ether was removed in vacuo.
Hexane (90 mL) was added to the residue and the mixture
was refluxed for 0.5 h. The solution was filtered and the solꢀ
vent was removed. The residue was distilled and compound 2
3ꢀHexyloxyꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane (15).
Hexyl alcohol (2.34 g, 23 mmol) was added with stirring to

Unique stereochemistry of 3ꢀborabicyclononanes
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
1975
was obtained in a yield of 3.24 g (71.6%), b.p. 115—120 °C
(1.5 Torr), m.p. 27—30 °C. Found (%): C, 85.73; H, 9.73;
B, 4.54. C17H23BO. Calculated (%): C, 85.65; H, 9.71; B, 4.18.
1H NMR (tolueneꢀd8), δ: 0.72 (dd, 2 H, H(2β), H(4β),
7.2—7.25 (m, 4 H, H(oꢀPh), H(mꢀPh)), 7.12 (t, 1 H, H(pꢀPh),
J = 7.2 Hz).
7αꢀPhenylꢀ3ꢀborabicyclo[3.3.1]nonanꢀ3ꢀyl quinolinꢀ8ꢀolate
(8). A solution of 8ꢀhydroxyquinoline (1.38 g, 9.5 mmol) in
Et2O (20 mL) was added to a solution of compound 4 (2.17 g,
9.5 mmol) in Et2O (10 mL). The reaction mixture was stirred for
1 h, the solvent was distilled off in vacuo, and the residue
was recrystallized from Et2O. Compound 8 was isolated in a
yield of 3.10 g (95.6%), m.p. 146—148 °C. Found (%): C, 80.95;
H, 7.09; B, 3.17. C23H24BNO. Calculated (%): C, 81.38; H, 7.05;
B, 3.00. 1H NMR (CDCl3), δ: 0.54 (dd, 2 H, H(2β), H(4β),
3
2JH(2β),H(2α) = 17.41 Hz, JH(2β),H(1) = 5.5 Hz); 1.02 (d, 2 H,
3
(CH2—CH), JH(Y),H(X) = 7.56 Hz); 1.41 (br.d, 1 H, Hsyn(9),
2JH
= 12.37 Hz); 1.49 (d, 2 H, H(2α), H(4α),
(9),H
(9)
syn
2JH(2α),H(2aβn)t=i 17.41 Hz); 1.71 (dm, 1 H, Hanti(9)); 1.87 (dt, 2 H,
2
3
H(6β), H(8β), JH(6β),H(6α) = 13.98 Hz, JH(6α),H(7) = 5.96 Hz);
2.15 (m, 2 H, H(1), H(5)); 2.22 (br.d, 4 H, H(6α), H(8α),
3
3JH(6α),H(7) = 5.96 Hz); 2.84 (m, 1 H, H(7), JH(7),H(6α)
=
3
3
5.96 Hz); 4.70 (dd, 2 H, (CH2=CH), JH(A),H(X) = 10.08 Hz,
3JH(B),H(X) = 17.06 Hz); 5.59 (ddt, 1 H, (CH=CH2), 3JH(X),H(A)
2JH(2β),H(2α) = 13.21 Hz, JH(2β),H(1) = 4.8 Hz); 0.88 (dd, 2 H,
=
H(2α), H(4α), 2JH(2α),H(2β) = 13.21 Hz); 1.32 (br.d, 1 H, Hsyn(9),
10.08 Hz, 3JH(X),H(B) = 17.06 Hz, 3JH(X),H(Y) = 7.56 Hz); 6.93 (t,
1 H, (pꢀPh), 2J = 7.33 Hz); 7.05 (m, 2 H, (mꢀPh)); 7.21 (d, 2 H,
(oꢀPh), 2J = 7.56 Hz).
1,3,5ꢀTrimethylꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane (5).
Analogously to the synthesis of compound 2, compound 5 was
synthesized from MeMgI (prepared from Mg (0.47 g, 19.5 mmol)
and MeI (2.8 g, 19 mmol)) and 3ꢀmethoxyꢀ1,5ꢀdimethylꢀ7ꢀ
phenylꢀ3ꢀborabicyclo[3.3.1]nonane (4.8 g, 18.7 mmol). The
yield was 3.7 g (82%), b.p. 118—120 °C (1.5 Torr), m.p. 63 °C.
Found (%): C, C, 85.00; H, 10.49; B, 4.50. C17H25B. Calcuꢀ
lated (%): C, 85.16; H, 10.39; B, 4.36.
2JH
(9) = 12.81 Hz); 1.95—2.07 (m, 4 H, H(6α), H(8α),
(9),H
syn
anti
H(6β), H(8β)); 2.12 (dm, 1 H, Hanti(9), 2JH
=
(9),H (9)
12.81 Hz); 2.42 (m, 2 H, H(1), H(5)); 2.87 (tatn,ti1 H, H(7),
3JH(7),H(6α) = 12.82 Hz, JH(7),H(6β) = 5.6 Hz); 7.03 (d, 1 H,
syn
3
H(7´), J = 7.61 Hz); 7.09 (d, 1 H, H(5´), J = 8.01 Hz); 7.18 (t,
1 H, H(oꢀPh)); 7.33 (t, 1 H, H(mꢀPh), J = 7.61 Hz); 7.49 (d,
2 H, H(oꢀPh), J = 7.61 Hz); 7.51 (m, 1 H, H(3´)); 7.59 (t, 1 H,
H(6´), J = 8.01 Hz); 8.24 (d, 1 H, H(4´), J = 8.01 Hz); 8.27 (d,
1 H, H(2´), J = 4.81 Hz).
3ꢀMethylꢀ7ꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonꢀ6ꢀene (11).
A solution of compound 12 (7.96 g, 35.2 mmol) in Et2O (20 mL)
was added to a solution of MeMgI prepared from Mg (0.86 g,
35.3 mmol) and MeI (5 g, 35.3 mmol) in Et2O (30 mL). The
reaction mixture was refluxed for 3 h and then cooled. The
diethyl ether was distilled off. The precipitate was washed
with hexane and filtered off. The filtrate was concentrated
in vacuo and the residue was distilled. Compound 11 was isoꢀ
lated in a yield of 3.48 g (47%), b.p. 126—127 °C (1.5 Torr),
3ꢀtertꢀButylꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane (6). The
Grignard reagent prepared from ButCl (5.4 g, 57 mmol) and Mg
(1.4 g, 57.5 mmol) in Et2O (25 mL) was added dropwise to a
solution of compound 4 (6.52 g, 28 mmol) in pentane (25 mL).
The reaction mixture was stirred for 3 h and filtered. The solvent
was distilled off in vacuo and the residue was distilled. Comꢀ
pound 6 was prepared in a yield of 5.07 g (70%), b.p. 127—128 °C
(5•10–2 Torr), nD 1.5348. Found (%): C, 85.03; H, 10.70;
nD 1.5615. Found (%): C, 85.73; H, 9.11; B, 5.15. C15H19B.
20
20
1
B, 4.26. C18H27B. Calculated (%): C, 84.78; H, 10.61; B, 4.10.
1H NMR (CDCl3), δ: 0.79 (s, 9 H, But); 1.02 (dd, 2 H, H(2β),
Calculated (%): C, 85.66; H, 9.05; B, 5.11. H NMR (CDCl3),
δ: 0.64 (s, 3 H, CH3); 1.1, 1.2, 1.25, and 1.31 (all m, 2 H, H(2β),
H(4β)); 1.50, 1.56, 1.61, and 1.68 (all m, 2 H, H(2α), H(4α));
1.68, 1.72, 1.85, and 1.91 (all m, 2 H, Hsyn(9), Hanti(9));
2.15 (dd, 1 H, H(8α)); 2.52, 2.65 (m, 2 H, H(1), H(5));
2.66, 2.75 (m, 1 H, H(8β)); 6.12 (m, 1 H, H(6)); 7.10—7.35
(m, 5 H, Ph).
3ꢀHexyloxyꢀ7αꢀmethylꢀ3ꢀborabicyclo[3.3.1]nonane was preꢀ
pared analogously to compound 15 from 3ꢀmethoxyꢀ7αꢀmeꢀ
thylꢀ3ꢀborabicyclo[3.3.1]nonane (7.78 g, 46.9 mmol) and hexyl
alcohol (4.79 g, 46.9 mmol). The yield was 9.1 g (82%), b.p.
120—123 °C (1.5 Torr). Found (%): C, 76.27; H, 12.38; B, 4.58.
C15H29BO. Calculated (%): C, 76.01; H, 12.12; B, 3.98.
1H NMR (CDCl3), δ: 0.80—1.00 (m, 8 H, H(2β), H(4β), 2 CH3);
1.05—1.45 (m, 9 H, H(6α), H(8α), Hsyn(9), (CH2)4); 1.50—1.70
(m, 3 H, H(2α), H(4α), Hanti(9)); 1.75—2.0 (m, 3 H, H(6β),
H(8β), H(7)); 2.15—2.2 (m, 2 H, H(1), H(5)); 3.75—3.90 (t, 2 H,
H(—O—CH2)). 13C NMR (CDCl3), δ: 13.94 (C(CH2CH3));
22.59 (C(5´)); 24.33 (C(CHCH3)); 25.35 (C(4’); 25.52 (C(7));
27.07 (C(1), C(5), C(2), C(4)); 31.42 (C(3´)); 31.58 (C(2´));
34.09 (C(9)); 65.15 (C(1´)).
3ꢀAllylꢀ7αꢀmethylꢀ3ꢀborabicyclo[3.3.1]nonane (13) was synꢀ
thesized analogously to compound 2 from 3ꢀhexyloxyꢀ7αꢀ
methylꢀ3ꢀborabicyclo[3.3.1]nonane (11.6 g, 39 mmol) and
allylmagnesium bromide prepared from Mg (1.89 g, 77.8 mmol)
and AllBr (4.72 g, 39 mmol) in Et2O. Compound 13 was isolated
in a yield of 7.79 g (84%), b.p. 115—120 °C (1.5 Torr).
Found (%): C, 81.14; H, 11.92; B, 5.28. C12H21B. Calcuꢀ
lated (%): C, 81.84; H, 12.02; B, 6.14. 1H NMR (tolueneꢀd8), δ:
2
3
H(4β), JH(2β),H(2α) = 18.03 Hz, JH(2β),(H1) = 5.61 Hz); 1.23
(br.d, 1 H, Hsyn(9), 2JH
(9) = 12.95 Hz); 1.27 (ddd, 2 H,
(9),H
syn
anti
2
3
H(6α), H(8α), JH(6α),H(6β) = 14.05 Hz, JH(6α),H(5) = 3.52 Hz,
3JH(6α),H(7)
2JH(2
=
9.9 Hz); 1.72 (dd,
= 18.03 Hz); 1.98 (dm, 1 H, Hanti(9)); 2.16 (ddd,
β
2 H, H(2α), H(4α),
α
),H(2 )
2
3
2 H, H(6β), H(8β), JH(6β),H(6α) = 14.05 Hz, JH(6β),H(7)
=
5.5 Hz, 3JH(6β),H(5) = 8.61 Hz); 2.33 (m, 2 H, H(1), H(5)); 2.83
(tt, 1 H, H(7)); 7.13 (t, 1 H, H(pꢀPh), 2J = 7.21 Hz); 7.19 (d,
2 H, H(oꢀPh), 2J = 7.21 Hz); 7.25 (t, 2 H, H(mꢀPh), 2J =
7.61 Hz).
3ꢀMethylaminoꢀ7αꢀphenylꢀ3ꢀborabicyclo[3.3.1]nonane (7).
Gaseous MeNH2 (1.06 g, 34.2 mmol) was introduced into a
solution of compound 3 (1.47 g, 6.3 mmol) in CH2Cl2 (20 mL).
The reaction mixture was stirred for 0.5 h, the solvent was disꢀ
tilled off, and the residue was distilled. Compound 7 was isoꢀ
lated in a yield of 0.74 g (51.7%), b.p. 125—126 °C (1.5 Torr),
m.p. 59—60 °C. Found (%): C, 84.97; H, 10.25; B, 4.78.
C
15H22BN. Calculated (%): C, 84.27; H, 9.98; B, 4.32. 1H NMR
(tolueneꢀd8), δ: 0.71 (br.d, 1 H, H(4α), 2JH(4α),H(4β) = 15.2 Hz);
2
3
0.77 (dd, 1 H, H(2β), JH(2 ),H(2 = 15.62 Hz, JH(2 ),H(1)
=
β
α
β
)
2
6.01 Hz); 0.89 (dd, 1 H, H(4β), JH(4β),H(4α) = 15.22 Hz,
3JH(4β),(H5) = 6.01 Hz); 1.15—1.21 (m, 3 H, H(6α), H(8α),
H(2α)); 1.26 (dm, 1 H, Hsyn(9), 2JH
(dm, 1 H, Hanti(9), 2JH
(9) = 12.8 Hz); 1.89
anti
= 12.81 Hz); 2.11 (m, 2 H,
(9),H
syn
(9),H (9)
anti
H(6β), H(8β)); 2.30 and 2.36 s(ybnoth m, 2 H, H(1), H(5)); 2.61
2
3
(d, 3 H, CH3, J = 6.01 Hz); 2.77 (tt, 1 H, H(7), JH(7),H(6
11.61 Hz, JH(7),H(6β) = 5.21 Hz); 3.75 (br.s, 1 H, (NH));
=
α
)
3

1976
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
Gurskii et al.
0.95 (d, 3 H, CH3, 2J = 7.34 Hz); 1.22 (dd, 2 H, H(2β), H(4β),
15. J. F. Richardson and T. S. Sorensen, Can. J. Chem., 1985,
63, 1166.
3
2JH(2β),H(2α) = 18.1 Hz, JH(2β),(H1) = 6.12 Hz); 1.49 (br.d, 2 H,
H(6α), H(8α), 2JH(6α),H(6β) = 12.23 Hz); 1.65 (br.d, 1 H, Hsyn(9),
16. M. E. Gurskii, A. S. Shashkov, and B. M. Mikhailov, Izv.
Akad. Nauk SSSR, Ser. Khim., 1981, 341 [Bull. Acad. Sci.
USSR, Div. Chem. Sci., 1981, 30 (Engl. Transl.)].
17. M. E. Gurskii, A. S. Shashkov, and B. M. Mikhailov,
J. Organomet. Chem., 1980, 199, 171.
18. M. E. Gurskii, I. D. Gridnev, Yu. N. Bubnov, A. Pelter, and
P. Rademacher, J. Organomet. Chem., 1999, 590, 2.
19. M. E. Gurskii, A. V. Gueiderikh, Yu. N. Bubnov, M. Yu.
Antipin, K. A. Lyssenko, I. D. Gridnev, R. Boese, and
D. Blaeser, J. Organomet. Chem., 2001, 636, 3.
20. K. A. Lyssenko, M. Yu. Antipin, M. E. Gurskii, Yu. N.
Bubnov, A. L. Karionova, and R. Boese, Chem. Phys. Lett.,
2004, 384, 40.
21. N. S. Zefirov, Usp. Khim., 1975, 44, 413 [Russ. Chem. Rev.,
1975, 44, 196 (Engl. Transl.)].
2JH
(9) = 12.71 Hz); 1.84—1.92 (m, 3 H, Hanti(9), H(2α),
(9),H
syn
H(4α)); 2a.0nt3i —2.06 (m, 3 H, H(6β), H(8β), H(7)); 2.18 (d, 2 H,
(CH2—CH), 3JH(Y),H(X) = 7.33 Hz); 2.32 (m, 2 H, H(1), H(5));
5.1 (dd, 2 H, (CH2=CH), JH(A),H(X) = 10.27 Hz, JH(B),H(X)
16.87 Hz); 5.71 (m, 1 H, (CH=CH2), JH(X),H(A) = 10.57 Hz,
3JH(X),H(B) = 16.87 Hz, JH(X),H(Y) = 7.33 Hz).
3
3
=
3
3
We thank I. D. Gridnev for recording lowꢀtemperaꢀ
ture NMR spectra of a series of compounds and helpful
discussion.
This study was financially supported by the Foundaꢀ
tion of the President of the Russian Federation (Federal
Program for the Support of Leading Scientific Schools,
Project Nos NShꢀ1917.2003.3 and NShꢀ1060.2003.30),
the Division of Chemistry and Materials Science of the
Russian Academy of Sciences (Program No. 1), and the
Russian Foundation for Basic Research (Project No. 03ꢀ
03ꢀ32214, the Program for Support of Young Doctors,
Grant MKꢀ1209.2003.03).
22. J. A. Peters, J. H. van der Toorn, and H. van Bekkum,
Tetrahedron, 1977, 33, 349.
23. (a) R. F. W. Bader, Atoms in Molecules. A Quantum Theory,
Clarendron Press, Oxford, 1990; (b) R. F. W. Bader, J. Chem.
Phys., 1998, A102, 7314.
24. K. R. Leopold, M. Canagaratna, and J. A. Philips, Acc.
Chem. Res., 1997, 30, 57.
25. A. A. Korlyukov, K. A. Lyssenko, M. Yu. Antipin, V. N.
Kirin, E. A. Chernyshev, and S. P. Knyazev, Inorg. Chem.,
2002, 41, 5043.
References
26. E. Espinosa, E. Mollins, and C. Lecomte, Chem. Phys. Lett.,
1998, 285, 170.
27. K. A. Lyssenko and M. Yu. Antipin, Izv. Akad. Nauk, Ser.
Khim., 2001, 400 [Russ. Chem. Bull., Int. Ed., 2001, 50, 418].
28. C. Gatti, E. May, and F. Cargnoni, J. Phys. Chem., 2002,
A106, 2707.
29. R. Boese, N. Niederprüm, and D. Bläser, in Molecules in
Natural Science and Medicine: An Encomium for Linus
Pauling, Eds Z. Maksic´ and M. EckertꢀMaksic´, Ellis
Horwood Limited, England, 1991, 103.
1. N. S. Zefirov and V. A. Palyulin, in Topics in Stereochemisꢀ
try, Eds E. L. Eliel and S. H. Wilen, Wiley, New York, 1991,
20, 171—230.
2. (a) V. S. Mastryukov, E. L. Osina, O. V. Dorofeeva,
M. V. Popik, L. V. Vilkov, and N. A. Belikova, J. Mol.
Structure, 1979, 52, 211; (b) V. S. Mastryukov, M. V. Popik,
O. V. Dorofeeva, A. V. Golubinskii, L. V. Vilkov, N. A.
Belikova, and N. L. Allinger, J. Am. Chem. Soc., 1981,
103, 1334.
3. J. A. Peters, Synthesis, 1979, 321.
30. B. M. Mikhailov, M. E. Gurskii, S. V. Baranin, Yu. N.
Bubnov, M. V. Sergeeva, K. A. Potekhina, A. V. Maleev,
and Yu. T. Struchkov, Izv. Akad. Nauk SSSR, Ser. Khim.,
1986, 1645 [Bull. Acad. Sci. USSR, Div. Chem. Sci., 1986, 35,
1494 (Engl. Transl.)].
4. T. Sasaki, Adv. Heterocycl. Chem., 1982, 30, 79.
5. B. M. Mikhailov and Yu. N. Bubnov, Organoboron Comꢀ
pounds in Organic Synthesis, Harwood Acad. Sci. Publ., Lonꢀ
don—New York, 1984.
6. R. S. Fort, Adamantane, The Chemistry of Diamond Molꢀ
ecules, Decker, New York—Basel, 1976.
31. N. S. Zefirov, V. S. Blagoveshchensky, I. Y. Kazimirchik,
and N. S. Surova, Tetrahedron, 1971, 27, 3111.
7. T. A. Henry, Plant Alkaloids, J. and A. Churdull Ltd, Lonꢀ
don, 1956.
8. N. K. Hurt, S. R. Jones, and J. A. Lamberton, Aust. J. Chem.,
1967, 20, 561.
9. S. W. Pelletier, Chemistry of the Alkaloids, van Nostrand,
New York, 1970.
10. J. A. Peters, J. M. van der Toorn, and H. van Bekkum,
Tetrahedron, 1977, 33, 349.
32. M. Oki, Application of Dynamic NMR Spectroscopy to Orꢀ
ganic Chemistry, in Methods in Stereochemichal Analysis,
Ed. A. P. Marchand, VCH Publishers, Inc., 1985, 4, p. 96.
33. H. Beall and C. H. Bushweller, Chem. Rev., 1973, 73, 465.
34. C. L. Perrin and T. J. Dwyer, Chem. Rev., 1990, 90, 935.
35. Yu. N. Bubnov, M. E. Gursky, I. D. Gridnev, A. V.
Ignatenko, Yu. A. Ustynyuk, and V. I. Mstislavsky,
J. Organomet. Chem., 1992, 424, 127.
11. Y. Senda, J. I. Ishiyama, and S. Imaizumi, J. Chem. Soc.,
Perkin Trans. 2, 1981, 90.
36. N. M. D. Brown, F. Davidson, and J. W. Wilson,
J. Organomet. Chem., 1981, 209, 1.
12. H.ꢀJ. Schneider and W. Ansorge, Tetrahedron, 1977,
33, 265.W
13. J. A. Peters, P. E. J. Peters van Granenburgh, J. M. van der
Toorn, Th. M. Wortel, and H. van Bekkum, Tetrahedron,
1978, 34, 2217.
37. B. M. Mikhailov and K. L. Cherkasova, Izv. Akad. Nauk
SSSR, Ser. Khim., 1971, 1244 [Bull. Acad. Sci. USSR, Div.
Chem. Sci., 1971, 20, 1150 (Engl. Transl.)].
38. M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A.
Montgomery, Jr., R. E. Stratmann, J. C. Burant,
S. Dapprich, J. M. Millam, A. D. Daniels, K. N. Kudin,
14. Th. R. Bok and W. N. Speckamp, Tetrahedron, 1979,
35, 267.W

Unique stereochemistry of 3ꢀborabicyclononanes
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 9, September, 2004
1977
M. C. Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi,
R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Clifford,
J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui,
K. Morokuma, D. K. Malick, A. D. Rabuck,
K. Raghavachari, J. B. Foresman, J. Cioslowski, J. V. Ortiz,
A. G. Baboul, B. B. Stefanov, G. Liu, A. Liashenko,
P. Piskorz, I. Komaromi, R. Gomperts, R. L. Martin, D. J.
Fox, T. Keith, M. A. AlꢀLaham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, J. L. Andres, C. Gonzalez, M. HeadꢀGordon,
E. S. Replogle, and J. A. Pople, Gaussian 98, Revision A.7,
Gaussian, Inc., Pittsburgh (PA), 1998.
39. J. Cheeseman, T. A. Keith, and R. W. F. Bader, AIMPAC
Program Package, McMaster University, Hamilton
(Ontario), 1992.
40. A. V. Shastin, T. I. Godovikova, S. P. Golova, M. V. Povorin,
D. E. Dmitriev, M. O. Dekaprilevich, Yu. A. Strelenko,
Yu. T. Struchkov, L. I. Khmel´nitskii, and B. L. Korsunskii,
Khim. Geterotsikl. Soedin., 1995, 31, 679 [Chem. Heterocycl.
Compd., 1995, 31 (Engl. Transl.)].
Received July 8, 2004;
in revised form August 13, 2004