Synthesis of substituted 2,3-dihydro-1H-boroles by transmetalation of aluminacyclopent-2-enes with BF3 · Et2O

Article abstract of DOI:10.1134/S1070428012060024

A procedure was developed for selective synthesis of 4,5-dialkyl-1-fluoro- 2, 3-dihydro-1H-boroles via transmetalation of the corresponding aluminacyclopent-2-enes with BF₃ · Et₂O. 4,5-Dialkyl-1-fluoro-2,3-dihydro-1H-boroles were isolated as complexes with BEtF2. 4-Alkyl-5-dimethylaminomethyl-1-fluoro-2,3- dihydro-1H-boroles were synthesized for the first time.

Full text of DOI:10.1134/S1070428012060024

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 6, pp. 761–766. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © L.O. Khafizova, L.I. Khusainova, T.V. Tyumkina, U.M. Dzhemilev, 2012, published in Zhurnal Organicheskoi Khimii, 2012,
Vol. 48, No. 6, pp. 765–770.
Synthesis of Substituted 2,3-Dihydro-1H-boroles
by Transmetalation of Aluminacyclopent-2-enes with BF3 ·Et2O
L. O. Khafizova, L. I. Khusainova, T. V. Tyumkina, and U. M. Dzhemilev
Institute of Petrochemistry and Catalysis, Russian Academy of Sciences,
pr. Oktyabrya 141, Ufa, 450075 Bashkortostan, Russia
e-mail: ink@anrb.ru
Received November 21, 2011
Abstract—A procedure was developed for selective synthesis of 4,5-dialkyl-1-fluoro-2,3-dihydro-1H-boroles
via transmetalation of the corresponding aluminacyclopent-2-enes with BF3·Et2O. 4,5-Dialkyl-1-fluoro-2,3-
dihydro-1H-boroles were isolated as complexes with BEtF2. 4-Alkyl-5-dimethylaminomethyl-1-fluoro-2,3-
dihydro-1H-boroles were synthesized for the first time.
DOI: 10.1134/S1070428012060024
Boron-containing materials exhibit unique optical
and structural properties. Three-coordinate boron atom
is essentially electron-deficient, which makes boron
compounds promising for use as donor–acceptor mate-
rials in nonlinear optics [1]. Among known methods of
synthesis of cyclic organoboron compounds, important
are those based on exchange reactions with participa-
tion of organometallic compounds.
We recently reported on the synthesis of 3-substi-
tuted 1-fluoroboracyclopentanes by reaction of boron
trifluoride–ether complex with 3-substituted 1-ethyl-
aluminacyclopentanes [2]. In continuation of these
studies we examined the reaction of BF3 ·Et2O with
2,3-substituted 1-ethylaluminacyclopent-2-enes [3, 4]
which were obtained by reaction of disubstituted
acetylenes with Et3Al in the presence of Cp2ZrCl2 as
catalyst (Scheme 1).
mixture showed disappearance of the aluminum signal
at δAl 180 ppm typical of initial compound Ib and
appearance of a new signal at δAl –11 ppm which was
assigned to AlEtF2. These findings indicated trans-
metalation leading to replacement of the aluminum
atom in Ib by boron.
After removal of the solvent and subsequent frac-
tional distillation under reduced pressure in a stream of
argon we isolated a transparent liquid which fumed on
1
exposure to air. The product was identified by H, 13C
(DEPT 135), and 11B NMR spectroscopy, including
one- and two-dimensional techniques (HSQC, HMBC,
HH COSY). In the downfield region of the 13C NMR
spectrum of the isolated compound we observed two
signals which were assigned to double-bonded carbon
atoms, C3 (δC 181.82 ppm) and C2 (δC 147.73 ppm,
broadened). Signals from the other ring carbon atoms
and two nonequivalent propyl groups were reliably
assigned on the basis of the HMBC data (see figure).
The C3 signal displayed couplings with protons on C6
in the propyl group and methylene protons on C4
(δC 36.26, δ 2.42 ppm). Joint analysis of the HSQC and
The reaction of 1-ethyl-2,3-dipropylaluminacyclo-
pent-2-ene (Ib) (prepared from oct-4-yne and AlEt3
[4]) with excess BF3 · Et2O in hexane at –10°C
involved boron–aluminum exchange with formation of
compound IIb. The 27Al NMR spectra of the reaction
Scheme 1.
R
R
AlEt3, Cp2ZrCl2
BF3 ·Et2O
+
EtAlF2
R
R
R
R
Al
Et
B
F
Ia–Ic
IIa–IIc
R = Et (a), Pr (b), Bu (c).
761

KHAFIZOVA et al.
762
CH3CH2BF2
7-H, 10-H
8-H, 11-H
4-H
6-H
9-H
CH3CH2BF2
5-H
δC, ppm
C5
C4
20
40
60
8
Me
6
7
4
CDCl3
3
10
11
Me
80
5
1
B
2
9
100
120
140
160
180
F
C2
C3
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
δ, ppm
HMBC spectrum of 1-fluoro-4,5-dipropyl-2,3-dihydro-1H-borole (IIb).
COSY spectra allowed us to unambiguously identify
protons on C5 (δC 21.70, δ 1.23 ppm); here, the key
correlation was that observed between protons on C4
and C5 in the HH COSY experiment. The boron
nucleus resonated in the 11B NMR spectrum (CDCl3)
at δB 81 ppm. The above data are very consistent with
the assumed 1-fluoro-4,5-dipropyl-2,3-dihydro-1H-
borole structure (see figure).
more, the 13C NMR spectrum of the product, apart
from signals assigned to 1-fluoro-4,5-dipropyl-2,3-
dihydro-1H-borole, contained additional signals at
δC 9.48 and 14.98 ppm, the latter being broadened.
These signals were assigned to the ethyl group in
BEtF2 molecule formed as a result of reaction of
AlEtF2 with BF3·Et2O (Scheme 2). Analogous results
were obtained in the reactions of BF3·Et2O with sub-
stituted aluminacyclopent-2-enes Ia and Ic; the latter
were synthesized from hex-3-yne and dec-5-yne,
respectively.
The molecular weight of the isolated compound
estimated by cryoscopy was 238.29 which differs from
168.06 calculated for 1-fluoro-4,5-dipropyl-2,3-dihy-
dro-1H-borole but approaches the molecular weight
calculated for the complex of 1-fluoro-4,5-dipropyl-
2,3-dihydro-1H-borole with BEtF2 (245.93). Further-
Thus the reaction of 2,3-dialkyl-1-ethylalumina-
cyclopent-2-enes Ia–Ic with BF3·Et2O yields 4,5-di-
alkyl-1-fluoro-2,3-dihydro-1H-boroles IIa–IIc as
Scheme 2.
R
R
BF3 ·Et2O
hexane, –10°C
BF3 ·Et2O
Distillation
+
EtAlF2
IIa–IIc + EtBF2
IIa–IIc·EtBF2
R
R
Al
Et
B
F
Ia–Ic
IIa–IIc
R = Et (a), Pr (b), Bu (c).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 6 2012

SYNTHESIS OF SUBSTITUTED 2,3-DIHYDRO-1H-BOROLES
763
Scheme 3.
R
R
H2O2, OH–
R
+
R
R
HO
Me
HO
4
3
O
2
5
IIIb, IIIc
IVb, IVc
1
B
R
R
F
MeOH
+
FB(OMe)2
R
IIb, IIc
Vb, Vc
VI
R = Pr (b), Bu (c).
Scheme 4.
R
R
AlEt3 (2 equiv), [Zr]
BF3 ·Et2O, –10°C
NMe2
NMe2
NMe2
Al
Et
B
R
F
VIIa, VIIb
VIIIa, VIIIb
R = Bu (a), C5H11 (b).
complexes with BEtF2 (Scheme 2), as in reactions of
3-substituted 1-ethylaluminacyclopentanes with BF3·
Et2O [2].
Cp2ZrCl2 [8]. These reactions gave 2,3-dihydro-1H-
boroles VIIIa and VIIIb having a dimethylamino-
methyl group on C2 (Scheme 4).
The structure of 4,5-dialkyl-1-fluoro-2,3-dihydro-
1H-boroles was additionally confirmed by their oxida-
tion with hydrogen peroxide in alkaline medium in
accordance with known methods of oxidation of
organoboron compounds [5–7]. As a result, we isolated
unsaturated alcohols IIIb and IIIc and hydroxy
ketones IVb and IVc at a ratio of 1:3. The reaction of
IIb and IIc with methanol afforded 1,2-dialkylbut-1-
enes Vb and Vc together with an equimolar amount of
BF(OMe)2 (VI) via protolytic cleavage of both B–C
bonds (Scheme 3).
Compounds VIIIa and VIIIb were isolated by
distillation, and their structure was confirmed by NMR
spectroscopy and determination of molecular weights
by cryoscopy. In the 13C NMR spectra of VIIIa and
VIIIb (CDCl3) signals from the double-bonded carbon
atoms were displaced by ~7–12 ppm relative to
those of dihydro-1H-boroles IIa–IIc. The boron signal
was located in the 11B NMR spectra at δB 5.2 ppm,
which is typical of three-coordinate boron atom [9].
Presumably, the heteroatoms in VIIIa and VIIIb are
involved in intra- and intermolecular interactions in
nonpolar solvent. Multiple signal splitting was ob-
served in the 13C NMR spectra, whereas no signals
assignable to the secondary exchange product (BEtF2)
were present.
We also tried to perform transmetalation of more
complex functionally substituted aluminacyclopent-2-
enes. For this purpose, boron trifluoride–ether complex
was brought into reaction with 3-alkyl-1-ethyl-2-
(N,N-dimethylaminomethyl)aluminacyclopent-2-enes
VIIa and VIIb which were synthesized from N,N-di-
methylalk-2-yn-1-amines and AlEt3 in the presence of
Thus aluminacyclopent-2-enes having nitrogen-
containing substituents successfully undergo trans-
metalation by the action of BF3·Et2O with formation
Scheme 5.
R
R
R
H2O2, OH–, 0°C, 24 h
NMe2
O
HO
Me2N
–NMe3
O
B
F
O
VIIIa, VIIIb
X
XIa, XIb
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 6 2012

KHAFIZOVA et al.
764
of the corresponding N,N-dimethyl-3-alkyl-1-fluoro-
4,5-dihydro-1H-borol-2-ylmethanamines.
room temperature, stirred for 30 min, and evaporated,
and the residue was distilled under reduced pressure in
a stream of argon.
The oxidation of VIIIa and VIIIb with hydrogen
peroxide in alkaline medium gave no unsaturated alco-
hols and hydroxy ketones like III and IV (Scheme 3)
but produced lactones XIa and XIb (Scheme 5). The
latter were likely to be formed via intramolecular
rearrangement of intermediate hydroxy ketone X with
simultaneous elimination of trimethylamine.
4,5-Diethyl-1-fluoro-2,3-dihydro-1H-borole–
ethyldifluoroborane (1/1) (IIa). Yield 1.05 g (48%),
colorless liquid, bp 70°C (11 mm). IR spectrum, ν,
cm−1: 2962, 2932, 2874, 1606, 1583, 1460, 1374,
1348, 1317, 1246, 1205, 1173, 1064, 912, 844, 785.
1H NMR spectrum, δ, ppm: 0.98 t (3H, CH3, J =
7.6 Hz), 1.08–1.11 m (3H, CH3CH2BF2), 1.12 t (3H,
CH3, J = 7.6 Hz), 1.24–1.29 m (2H, 5-H), 1.30–1.37 m
(2H, CH2BF2), 2.22 q (2H, CH2, J = 7.6 Hz), 2.40 q
(2H, CH2, J = 7.6 Hz), 2.44 m (2H, 4-H). 13C NMR
spectrum, δC, ppm: 9.44 (CH3CH2BF2), 13.18, 14.72
(CH3CH2BF2), 15.29, 20.38, 21.65 (C5), 23.95, 35.81
(C4), 145.37 (C2), 182.90 (C3). 11B NMR spectrum, δB,
To conclude, we were the first to accomplish trans-
metalation of aluminacyclopent-2-enes, including
functionally substituted derivatives, with boron tri-
fluoride–ether complex to obtain dihydro-1H-boroles.
The described reaction opens a simple and efficient
one-pot synthetic route to five-membered unsaturated
organoboron compounds starting from acetylenes,
organoaluminum compounds, and BF3·Et2O.
ppm: 34.6 (BEtF2, W1/2 = 2.8 kHz), 81.19 (W1/2
=
1.6 kHz). Found, %: C 54.86; H 8.55. M 198.21.
C10H19B2F3. Calculated, %: C 55.03; H 8.78. M 217.87.
EXPERIMENTAL
1-Fluoro-4,5-dipropyl-2,3-dihydro-1H-borole–
ethyldifluoroborane (1/1) (IIb). Yield 1.18 g (48%),
colorless liquid, bp 80°C (13 mm). 1H NMR spectrum,
δ, ppm: 0.90–1.00 m (6H, CH3), 1.10 t (3H, CH3CH2-
BF2, J = 7.6 Hz), 1.23 m (2H, 5-H), 1.30–1.38 m (4H,
CH2, CH3CH2BF2), 1.55 sext (2H, CH2, J = 7.6 Hz),
2.18 t (2H, CH2, J = 7.6 Hz), 2.36 t (2H, CH2, J =
7.6 Hz), 2.42 m (2H, 4-H). 13C NMR spectrum, δC,
ppm: 9.48 (CH3CH2BF2), 14.26, 14.38, 14.95 (CH3-
CH2BF2), 21.61 (C5), 21.85, 24.05, 29.85, 33.30, 36.26
(C4), 148.84 (C2), 183.13 (C3). 11B NMR spectrum, δB,
All reactions with organometallic reagents were
carried out under argon. Commercially available
98% AlEt3, 48% BF3·Et2O, and symmetrically substi-
tuted acetylenes were used without additional purifica-
tion. Alkynylamines were synthesized by aminometh-
ylation of the corresponding terminal alkynes [10].
Hexane was distilled over Al(i-Bu)3. The IR spectra
were recorded from thin films on a Bruker Vertex 70
1
13
11
spectrometer. The H, C, 27Al, and B NMR spectra,
including homo- (COSY) and heteronuclear (HSQC,
HMBC) correlation spectra, were measured from solu-
tions in CDCl3 on a Bruker Avance 400 spectrometer
at 400.13 (1H), 100.62 (13C), 128.33 (11B), and
ppm: 35.16 (EtBF2, W1/2 = 1.6 kHz), 80.76 (W1/2
=
1.2 kHz). Found, %: C 58.32; H 9.21. M 238.29.
C12H23B2F3. Calculated, %: C 58.51; H 9.42. M 245.93.
1
104.22 MHz (27Al); the H and 13C chemical shifts
4,5-Dibutyl-1-fluoro-2,3-dihydro-1H-borole–
ethyldifluoroborane (1/1) (IIc). Yield 1.27 g (47%),
colorless liquid, bp 120°C (14 mm). IR spectrum, ν,
cm−1: 2958, 2928, 2859, 1603, 1582, 1460, 1376,
1348, 1209, 1104, 1074, 1039, 996, 909, 844, 774,
were determined relative to tetramethylsilane, 11B,
relative to BF3 ·Et2O, and 27Al, relative to AlCl3 in
D2O. The molecular weights of organoboron com-
pounds were determined by cryoscopy in benzene
according to the procedure described in [11]. The
elemental compositions were determined on a Carlo
Erba 1106 analyzer.
1
728. H NMR spectrum, δ, ppm: 0.90–1.00 m (6H,
CH3), 1.09 t (3H, CH3CH2BF2, J = 7.6 Hz), 1.23 m
(2H, 5-H), 1.27–1.42 m (10H, CH2, CH3CH2BF2),
2.20 t and 2.38 t (2H each, 4-CH2, 5-CH2, J = 7.6 Hz),
2.42 m (2H, 4-H). 13C NMR spectrum, δC, ppm: 9.48
(CH3CH2BF2), 13.98, 14.08, 14.98 (CH3CH2BF2),
21.70 (C5), 23.07, 27.27, 30.86, 30.94, 33.13, 36.32
(C4), 147.76 (C2), 181.88 (C3). 11B NMR spectrum, δB,
Complexes IIa–IIc of 4,5-dialkyl-1-fluoro-2,3-di-
hydro-1H-boroles with BEtF2 (general procedure).
A glass reactor was charged under dry argon with 5 ml
of hexane, 0.5 mmol of Cp2ZrCl2, 10 mmol of the
corresponding alkyne, and 12 mmol of AlEt3 were
added in succession under stirring at 0°C, and the
mixture was stirred for 8 h at 20–22°C. The mixture
was then diluted with 10 ml of hexane, cooled to
–10°C, and 24 mmol of BF3·Et2O was gradually added
dropwise. The mixture was allowed to warm up to
ppm: 35.16 (EtBF2, W1/2 = 1.6 kHz), 81.57 (W1/2
=
1.2 kHz). Found, %: C 61.17; H 9.68. M 270.15.
C14H27B2F3. Calculated, %: C 61.29; H 9.92. M 273.98.
Oxidation of 4,5-dialkyl-1-fluoro-2,3-dihydro-
1H-boroles IIb and IIc with hydrogen peroxide in
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 6 2012

SYNTHESIS OF SUBSTITUTED 2,3-DIHYDRO-1H-BOROLES
765
alkaline medium (genral procedure). Compound IIb
or IIc was dissolved in 10 ml of hexane, 6 ml of 20%
aqueous sodium hydroxide was added at 0°C, and 2 ml
of 30% hydrogen peroxide was then added dropwise.
The mixture was stirred for 6 h, the organic phase was
separated, the aqueous phase was extracted with
diethyl ether (2×30 ml), the extracts were combined
with the organic phase, dried over CaCl2, and concen-
trated under reduced pressure, and the residue was
subjected to column chromatography on silica gel (40–
100 mesh, 30 cm×12 mm) using ethyl acetate−hexane
(1:50) as eluent.
Reaction of 4,5-dialkyl-1-fluoro-2,3-dihydro-1H-
boroles IIb and IIc with methanol (general proce-
dure). A solution of 5 mmol of compound IIb or IIc in
10 ml of hexane was cooled to 0°C, 20 mmol of
methanol was added, and the mixture was stirred for
1 h. The solvent and excess methanol were removed
under reduced pressure, and the residue was distilled in
a vacuum. The spectral parameters and physical con-
stants of Vb and Vc were reported in [12, 13].
(3-Alkyl-1-fluoro-4,5-dihydro-1H-borol-2-yl)-
N,N-dimethylmethanamines VIIIa and VIIIb (gen-
eral procedure). A glass reactor was charged under
argon with 50 ml of hexane, 2.0 mmol of Cp2ZrCl2,
10 mmol of the corresponding alkynylamine, and
20 mmol of AlEt3 were added in succession, and the
mixture was stirred for 3 h at 40°C. The mixture was
then cooled to –10°C, 40 mmol of BF3·Et2O was grad-
ually added dropwise, the mixture was allowed to
warm up to room temperature, stirred for 30 min, and
evaporated, and the residue was distilled under reduced
pressure in a stream of argon.
3-Propylhept-3-en-1-ol (IIIb). Yield 31%, Rf 0.62
1
(ethyl acetate–hexane, 1:5). H NMR spectrum, δ,
ppm: 0.91 t (6H, CH3, J = 7.2 Hz), 1.32–1.45 m (4H,
CH2), 1.98–2.04 m (4H, CH2), 2.25 t (2H, CH2CH=C,
J = 6.2 Hz), 3.64 m (2H, CH2OH), 5.23 t (1H, CH=C,
J = 7.0 Hz). 13C NMR spectrum, δC, ppm: 13.86,
14.09, 21.64, 23.13, 29.89, 31.80, 39.93, 60.42,
128.51, 135.38. Found, %: C 76.77; H 12.79. C10H20O.
Calculated, %: C 76.86; H 12.90.
3-Butyloct-3-en-1-ol (IIIc). Yield 29%, Rf 0.62
(ethyl acetate–hexane, 1:5). H NMR spectrum, δ,
(3-Butyl-1-fluoro-4,5-dihydro-1H-borol-2-yl)-
N,N-dimethylmethanamine (VIIIa). Yield 1.22 g
(62%), yellow oily liquid, bp 101°C (10 mm). IR spec-
trum, ν, cm−1: 2961, 2952, 2853, 1487, 1458, 1419,
1
ppm: 0.92 t (6H, CH3, J = 7.0 Hz), 1.32–1.38 m (8H,
CH2), 2.01–2.05 m (4H, CH2), 2.27 t (2H, CH2, J =
6.2 Hz), 3.66 t (2H, CH2OH, J = 6.4 Hz), 5.24 t (1H,
CH=C, J = 7.0 Hz). 13C NMR spectrum, δC, ppm:
13.96, 13.99, 22.42, 22.79, 27.47, 29.49, 30.76, 32.24,
39.98, 60.40, 128.50, 135.42. Found, %: C 77.95;
H 13.02. C12H24O. Calculated, %: C 78.19; H 13.13.
1
1374, 1337, 1220, 1053, 765, 724. H NMR spectrum,
δ, ppm: 0.90 br.m (3H, CH3), 1.22–1.43 br.m (4H,
CH2), 1.45–1.54 br.m (2H, 5-H), 2.36–2.58 br.m (10H,
CH2, CH3N), 3.71 br.s (2H, CH2N). 13C NMR spec-
trum, δC, ppm: 13.97, 14.06, 14.43 (CH3); 23.28, 23.65
(C8); 28.85 (C5); 31.26, 31.29, 31.32 (C7); 32.71, 32.77
(C6); 32.56 (C4); 42.35, 42.79 (NCH3); 51.06 (CH2N),
135.20 (C2), 195.16 (C3). 11B NMR spectrum:
δB 5.2 ppm (W1/2 = 1.6 kHz). Found, %: C 66.54;
H 10.41; N 6.97. M 184.33. C11H21BFN. Calculated,
%: C 66.96; H 10.73; N 7.10. M 197.10.
7-Hydroxy-5-propylheptan-4-one (IVb). Yield
1
62%, Rf 0.67 (ethyl acetate–hexane, 1:5). H NMR
spectrum, δ, ppm: 0.89 m (6H, CH3), 1.27–1.45 m (2H,
CH2), 1.35 m (2H, CH2), 1.55 m (2H, CH2), 1.60 m
(1H, CH2), 1.76 m (1H, CH2), 2.42 m (2H, CH2),
2.64 m (1H, CH), 3.56 t (2H, CH2OH, J = 8.0 Hz).
13C NMR spectrum, δC, ppm: 13.70, 13.73, 16.81,
20.52, 34.00, 34.06, 44.34, 48.75, 60.67, 215.30.
Found, %: C 69.61; H 11.61. C10H20O2. Calculated, %:
C 69.72; H 11.70.
(1-Fluoro-3-pentyl-4,5-dihydro-1H-borol-2-yl)-
N,N-dimethylmethanamine (VIIIb). Yield 1.27 g
(60%), yellow oily liquid, bp 75°C (2 mm). IR spec-
trum, ν, cm−1: 2959, 2963, 2858, 1491, 1416, 1382,
1
6-Butyl-8-hydroxyoctan-5-one (IVc). Yield 58%,
1338, 1225, 1048, 763, 731. H NMR spectrum, δ,
1
Rf 0.67 (ethyl acetate–hexane, 1:5). H NMR spec-
ppm: 0.90 br.m (3H, CH3), 1.20–1.40 br.m (6H, CH2),
1.45–1.55 br.m (2H, 5-H), 2.37–2.60 br.m (10H, CH2,
CH3N), 3.73 br.s (2H, CH2N). 13C NMR spectrum, δC,
ppm: 13.89, 13.97, 14.06 (CH3); 22.56, 22.62 (C9);
28.04, 28.07 (C7); 28.80 (C5); 31.04, 31.11, 31.97,
32.05 (C8); 32.47 (C4); 36.52, 36.79 (C6); 42.31, 42.79
(NCH3); 51.00 (CH2N), 135.00 (C2), 194.56 (C3).
11B NMR spectrum: δB 5.2 ppm (W1/2 = 1.6 kHz).
Found, %: C 67.85; H 10.69; N 6.47. M 233.45.
trum, δ, ppm: 0.93 m (6H, CH3), 1.27–1.48 m (6H,
CH2), 1.35 m (2H, CH2), 1.56 m (2H, CH2), 1.58 m
(1H, CH2), 1.78 m (1H, CH2), 2.44 m (2H, CH2),
2.66 m (1H, CH), 3.63 t (2H, CH2OH, J = 8.0 Hz).
13C NMR spectrum, δC, ppm: 14.06, 14.12, 22.38,
22.78, 25.65, 29.70, 31.56, 34.01, 42.15, 49.06, 61.02,
215.39. Found, %: C 71.83; H 12.00. C12H24O2. Cal-
culated, %: C 71.95; H 12.08.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 6 2012

KHAFIZOVA et al.
766
C12H23BFN. Calculated, %: C 68.20; H 10.97; N 6.63.
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1. Chen, J., Kampf, J.W., and Ashe, A.J. III, Organo-
metallics, 2008, vol. 27, p. 3639.
Oxidation of (3-alkyl-1-fluoro-4,5-dihydro-1H-
borol-2-yl)-N,N-dimethylmethanamines VIIIa and
VIIIb (general procedure). A solution of 5 mmol of
compound VIIIa or VIIIb in 10 ml of hexane was
cooled to 0°C, 6 ml of 20% aqueous sodium hydroxide
was added, and 2 ml of 30% hydrogen peroxide was
then slowly added dropwise. The mixture was stirred
for 24 h, the organic phase was separated, the aqueous
phase was extracted with diethyl ether (2×30 ml), the
extracts were combined with the organic phase, dried
over CaCl2, and concentrated under reduced pressure,
and the residue was subjected to column chromatog-
raphy on silica gel using hexane–ethyl acetate (50:1)
as eluent.
2. Khafizova, L.O., Khusainova, L.I., Tyumkina, T.V., and
Dzhemilev, U.M., Russ. J. Org. Chem., 2012, vol. 48,
p. 755.
3. Dzhemilev, U.M., Ibragimov, A.G., and Zolotarev, A.P.,
Mendeleev Commun., 1992, no. 4, p. 135.
4. Dzhemilev, U.M. and Ibragimov, A.G., Russ. Chem.
Rev., 2000, vol. 69, p. 121.
5. Mikhailov, B.M. and Bubnov, Yu.N., Bororganicheskie
soedineniya v organicheskom sinteze (Organoboron
Compounds in Organic Synthesis), Moscow: Nauka,
1977.
6. Brown, H.C. and Gupta, S.K., J. Am. Chem. Soc., 1972,
vol. 94, p. 4370.
3-Butyltetrahydrofuran-2-one (XIa). Yield 62%,
Rf 0.52 (ethyl acetate–hexane, 1:5). H NMR spec-
7. Kulkarni, S.U., Lee, H.D., and Brown, H.C., Synthesis,
1
1982, p. 193.
trum, δ, ppm: 0.93 t (3H, CH3, J = 7.0 Hz), 1.20–
1.51 m (4H, CH2), 1.87–2.00 m (2H, CH2), 2.36–
2.44 m (2H, CH2), 2.49–2.64 m (1H, CH), 4.20 m and
4.35 m (1H each, CH2O). 13C NMR spectrum, δC, ppm:
13.87, 22.44, 28.63, 29.48, 30.03, 39.23, 66.44,
179.62. Found, %: C 67.46; H 9.85. C8H14O2. Calculat-
ed, %: C 67.57; H 9.92
8. Ramazanov, I.R., Kadikova, R.N., and Dzhemi-
lev, U.M., Izv. Ross. Akad. Nauk, Ser. Khim., 2011,
no. 1, p. 96.
9. Hermanek, S., Chem. Rev., 1992, vol. 92, p. 325.
10. Shaibakova, M.G., Titova, I.G., Ibragimov, A.G., and
Dzhemilev, U.M., Russ. J. Org. Chem., 2008, vol. 44,
p. 1126.
3-Pentyltetrahydrofuran-2-one (XIb). Yield 62%,
Rf 0.52 (ethyl acetate–hexane, 1:5). H NMR spec-
11. Rybak, B.M., Analiz nefti i nefteproduktov (Analysis of
Petroleum and Petrochemicals), Moscow: Gostoptekh-
izdat, 1962.
1
trum, δ, ppm: 0.89 t (3H, CH3, J = 6.8 Hz), 1.25–
1.48 m (6H, CH2), 1.87–2.00 m (2H, CH2), 2.35–
2.43 m (2H, CH2), 2.47–2.55 m (1H, CH), 4.18 m (1H,
CH2O), 4.33 m (1H, CH2O). 13C NMR spectrum, δC,
ppm: 13.95, 22.42, 26.97, 28.61, 30.26, 31.50, 39.23,
66.49, 179.63. Found, %: C 69.10; H 10.24. C9H16O2.
Calculated, %: C 69.19; H 10.32.
12. Takahashi, T., Xi, Ch., Kageyama, M., Fischer, R.,
Nakajima, K., and Negishi, E., J. Org. Chem., 1998,
vol. 63, p. 6802.
13. Negishi, E., Kondakov, D.Y., Choueiry, D., Kasai, K.,
and Takahashi, T., J. Am. Chem. Soc., 1996, vol. 118,
p. 9577.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 6 2012