Cp2TiCl2-catalyzed cycloboration of α-olefins with PhBCl2in the synthesis of 2-alkyl(aryl,benzyl)-1-phenylboriranes

Article abstract of DOI:10.1016/j.jorganchem.2017.01.009

A one-pot method for the synthesis of 2-alkyl(aryl, benzyl)-1-phenylboriranes has been developed via the reaction of α-olefins with PhBCl₂in the presence of Cp₂TiCl₂as the catalyst. The method implies the formation of boriranes as the result of transmetalation of titanacyclopropane intermediates generated in the reaction of α-olefins with Cp₂TiCl₂. Individual 1-phenyl-2-substituted boriranes were isolated and their structures confirmed by NMR spectral methods.

Full text of DOI:10.1016/j.jorganchem.2017.01.009

Accepted Manuscript
Cp TiCl -catalyzed cycloboration of α-olefins with PhBCl in the synthesis of 2-
2
2
2
alkyl(aryl,benzyl)-1-phenylboriranes
Liliya I. Khusainova, Leila O. Khafizova, Tatyana V. Tyumkina, Kirill S. Ryazanov,
Usein M. Dzhemilev
PII:
S0022-328X(17)30029-3
10.1016/j.jorganchem.2017.01.009
JOM 19766
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 2 September 2016
Revised Date: 30 December 2016
Accepted Date: 16 January 2017
Please cite this article as: L.I. Khusainova, L.O. Khafizova, T.V. Tyumkina, K.S. Ryazanov, U.M.
Dzhemilev, Cp TiCl -catalyzed cycloboration of α-olefins with PhBCl in the synthesis of 2-
2
2
2
alkyl(aryl,benzyl)-1-phenylboriranes, Journal of Organometallic Chemistry (2017), doi: 10.1016/
j.jorganchem.2017.01.009.
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ACCEPTED MANUSCRIPT
Leave this area blank for abstract info.
Cp2TiCl2-catalyzed cycloboration of α-
olefins with PhBCl2 in the synthesis of
2-alkyl(aryl,benzyl)-1-phenylboriranes
R
Liliya I. Khusainova, Leila O. Khafizova,*
Tatyana V. Tyumkina, Kirill S. Ryazanov,
Usein M. Dzhemilev
R
Mg, Cp2TiCl2 (20 mol%)
B
+
solvent
PhBCl2
R = Ar, Alk

1
ACCEPTED MANUSCRIPT
Cp2TiCl2-catalyzed cycloboration of α-olefins with PhBCl2 in the synthesis of
2-alkyl(aryl,benzyl)-1-phenylboriranes
Liliya I. Khusainova, Leila O. Khafizova,* Tatyana V. Tyumkina, Kirill S. Ryazanov,
Usein M. Dzhemilev
Institute of Petrochemistry and Catalysis of Russian Academy of Sciences,
141 Prospekt Oktyabrya, Ufa 450075, Russian Federation
Abstract
A one-pot method for the synthesis of 2-alkyl(aryl,benzyl)-1-phenylboriranes has been
developed via the reaction of α-olefins with PhBCl2 in the presence of Cp2TiCl2 as the catalyst.
The method implies the formation of boriranes as the result of transmetalation of
titanacyclopropane intermediates generated in the reaction of α-olefins with Cp2TiCl2. Individual
1-phenyl-2-substituted boriranes were isolated and their structures confirmed by NMR spectral
methods.
Keywords
Boriranes, α-olefins, cycloboration, catalysis, PhBCl2, Cp2TiCl2.
1. Introduction
Hydro- and carboboration of unsaturated compounds catalyzed by transition metal (Zr,
Rh, Pd, Pt, Ni) complexes affording various acyclic organoboron compounds are widely covered
in the literature [1]. To the best of our knowledge, there has been no information on the
application of homogeneous metal complex catalysts in the cycloboration reactions of
unsaturated compounds.
Recently, we have carried out direct cycloboration of α-olefins with BCl3·SMe2 (or
BF3·THF) in the presence of metallic magnesium and Cp2TiCl2 catalyst [2] to produce 1-chloro-
2-substituted boriranes 1 existing as complexes with SMe2, and 1-fluoro-2-alkylboriranes (2) as
associates with BF3 (Scheme 1).
* Corresponding author. Fax: +73472842750;
e-mail: khafizovaleila@gmail.com (L.O. Khafizova).

2
ACCEPTED MANUSCRIPT
Scheme 1. Cycloboration of α-olefins with BCl3·SMe2 or BF3·THF catalyzed by Cp2TiCl2.
In the literature, there are examples of only non-catalytic syntheses of boriranes. Berndt
A. and Klusik H. synthesized the first boriranes in 1983 by [2+2] cycloaddition of acetone and
diphenylacetylene with methyleneborane [3]. Later, there appeared information about the
preparation of boriranes under photoizomerization conditions from tetramethylammonium
triphenylstyrylborate [4] and pyridinium diphenyl((E)-2-phenylethenyl)borate [5] under UV
irradiation. Recently the research group of Wang S. has reported the synthesis of a number of
intramoleculary base-stabilized boriranes via UV irradiation of dimesitylboranes chelated by a
variety of N-C [6] and C-CNHC (NHC = N-heterocyclic carbene) [7] biaryl-like groups.
Braunschweig H. et. al. has reported a facile and selective synthetic route to monocyclic NHC-
stabilized boriranes [8].
In this paper, we report an efficient one pot synthesis of 2-alkyl(aryl, benzyl)-1-phenyl-
boriranes via the reaction of α-olefins with PhBCl2 in the presence of Cp2TiCl2 as the catalyst.
2. Results and discussion
In continuation of our ongoing research, aimed at developing new methods for the
synthesis of boriranes using available and preparatively convenient organoboron reagents, we
have studied the reaction between α-olefins and PhBCl2 in the presence of Cp2TiCl2 exhibiting a
high catalyst activity and selectivity in the cyclometalation reaction of α-olefins with BCl3·SMe2
or BF3·THF.
The reaction of oct-1-ene with PhBCl2 in the presence of metallic magnesium (acceptor
of chloride ions) and catalytic amounts of Cp2TiCl2 has selected as a model reaction. We have
found that the interaction between oct-1-ene and PhBCl2 (20 mol% Cp2TiCl2, 25 ºC, 14 h)
affords 2-hexyl-1-phenyl-borirane 3 (Scheme 2). The reaction proceeds to full conversion of the
original oct-1-ene.

3
ACCEPTED MANUSCRIPT
4
6
8
3
Hex
_
Mg, Cp2TiCl2 (20 mol%)
2
H2O2, OH
7
5
9
B
+
Et2O, 25 oC
0oC
PhBCl2
3
Hex
+
OH
OH
OH
OH
+
Hex
+
Hex
HO
4
5
6
7
BSA
Hex
OTMS
OTMS
OTMS
+
+
+
Hex
Hex
TMSO
OTMS
9
10
11
Me
N
O
SiMe3
Me Si
BSA =
3
Scheme 2. Synthesis and oxidation of 2-hexyl-1-phenylborirane 3.
Formation of 2-hexyl-1-phenylborirane 3 does not occur in the absence of a catalyst.
We assumed that the expected 2-hexyl-1-phenylboriran 3 is a labile compound.
Therefore, after removal of the solvent from the reaction mixture, the residue was dissolved in
CDCl3 and the resulting solution containing the intended substance was analyzed by the 13C and
1H NMR spectral methods.
13
Thus, the С (CDCl3) NMR signals at δC 14.30, 22.87, 29.51, 29.74, 32.04, and 38.63
ppm reveal the presence of a hexyl substituent. In the HSQC spectrum, which exhibits a
broadened С4 methylene signal (δ 38.63), cross-peaks appear with magnetically nonequivalent
protons [δ(С4HA) 1.53 and δ(С4HB) 1.75 ppm]. Diastereotopicity of these protons is due to the
nearby С2 asymmetric center of the borirane ring. In the 13С NMR spectrum the signals of carbon
atoms of borirane ring do not occur, apparently, due to the quadrupole broadening effects of the
boron nuclei [9].
For this reason, there is no signal of the quaternary carbon atom of the phenyl substituent
directly attached to the boron atom. In the 13С NMR spectrum of the source
phenyldichloroborane the same signal is also absent. These signals in the low-temperature (T =
13
210 K) С NMR spectrum of compound 3 have not been registered, apparently due to the lack
of conformational mobility of the three-membered B-containing ring at room temperature. Other
signals of the phenyl substituent in the 13С NMR spectrum of borirane 3 observed in the
expected region of sp2-hybridized carbon atoms (128.17, 132.88, and 135.84 ppm).

4
ACCEPTED MANUSCRIPT
The 11В NMR spectrum exhibited a broadened signal at 30.29 ppm, which is close to the
value of the boron signal peak for borirane-2-ylideneborane δ(11B) = 34.0 ppm [3] and
trimesitylborirene δ(11B) = 34.8 ppm [10].
The boron signal of 3 was shifted downfield compared to the signals of the boron atom in
1-chloro(fluoro)-2-substituted boriranes 1 and 2, being identified in the spectra of complexes
with SMe2 (δ ~2 ppm) for 1 [2a] or associates with BF3 (δ ~ −1 ppm) for 2 [2b].
Upon treatment of the reaction mass with H2O2 under alkaline conditions [2, 11] diol 4
and monools 5 and 6 (1:1:1 ratio) have been obtained in 75% total yield (Scheme 2). Along with
alcohols 4–6, phenol 7 has also formed. The identification of diol and monools in the reaction
mixture testifies the formation of the target borirane 3. Alcohols 4–7 were isolated using column
chromatography and identified by spectral methods. For GLC determining of alcohols, they were
converted into the corresponding ethers 8–10 by treating the reaction mixture with
bis(trimethylsilyl)acetamide (BSA) [12].
Considering that acyclic and cyclic organoboron compounds form sufficiently strong
molecular complexes with heteroatomic compounds, e.g., pyridine [11c, 10], we have introduced
an equimolar amount of pyridine into the reaction mixture containing, as we believed, 1-phenyl-
11
2-hexylborirane 3. Meanwhile in В NMR spectrum the second signal of the boron atom with
greater intensity at 2.1 ppm appeared thus indicating the molecular complex formation between 3
and pyridine. This chemical shift value was close to those exhibited by the known boriranes
11
containing the pyridine fragment. For example, the B NMR spectra of (2S,3S,2”S)-1-[3-(2-N-
methylpyrrolidinyl)pyridinium] 1,2,3-triphenylboratirane and chelate borabicyclo[4.1.0]hepta-
2,4-diene show the signals at −5.02 [5] and −4.55 ppm [6d] respectively.
Apparently, in the solution there exists equilibrium between complexed and uncomplexed
forms of 2-hexyl-1-phenylborirane 3 (Scheme 4). The reversible complexation with pyridine for
the three-membered B-containing rings is reported [10].
Scheme 4. The reversible complexation between borirane 3 and pyridine.
We have evaluated the thermodynamic possibility of the complex formation between 1-
phenyl-2-ethylborirane and a pyridine molecule by comparing the calculated Gibbs energies of
the complex and the original molecules (PBE/3z, Priroda 6.0) [13]. It turned out that the
formation of such complex is thermodynamically possible (∆G = –13.2 kcal/mol).

5
ACCEPTED MANUSCRIPT
To separate the pyridine complex from the solution, after pre-evacuation of the reaction
o
mixture, the residue was subjected to a high-vacuum sublimation (oil bath 180 to 200 C, 2
hours). As a result, we have succeeded in isolating an air- and moisture-sensitive compound,
whose structure corresponds to 2-hexyl-1-phenylborirane 3.
Its mass spectrum (70eV) displayed mass peaks, which were exhibited at 231 and 232
(C14H21BO2), 130 (C8H18O), 114 (C8H18) 94 (PhOH). All these peaks are consistent with
oxidation and hydrolysis products, arising from 3 in the mass spectrometer.
Our attempts to isolate a pyridine complex by vacuum sublimation resulted in an
individual borirane 3, free from pyridine molecules. Apparently, the pyridine complex is not
strong enough and under thermal conditions undergoes cleavage. We have established that NMR
spectra of the individual 2-hexyl-1-phenylborirane 3 and the product from the reaction mass are
virtually identical.
It should be noted that the reaction in THF also leads to 2-hexyl-1-phenylborirane 3, the
formation of which was controlled by NMR (1H, 13C, 11B) spectra and oxidation products 4-7.
It turned out that the boron signal of compound 3 in THF appears at 2.7 ppm and is close in
value to the boron signal of pyridine complex, however shifted upfield relative to the signal of 3
in diethyl ether and chloroform (~ 30 ppm). Apparently, this takes place due to the complex
formation between borirane 3, and molecules of pyridine and tetrahydrofuran, whereas in diethyl
ether the specified solvation (close association with the solvent) on the boron atom does not
occur.
In an analogous fashion, hex-1-ene, dec-1-ene, styrene, o-, m-, and p-methylstyrene react
with PhBCl2 in the presence of Cp2TiCl2 catalyst. The reaction is of a general nature. It resulted
in the formation of 1-phenyl-2-substituted boriranes 12a‒f under reaction conditions designed
for oct-1-ene (Scheme 5).

6
ACCEPTED MANUSCRIPT
Scheme 5. Cp2TiCl2-catalyzed cycloboration of α-olefins with PhBCl2.
Upon oxidation of boriranes 12a‒f with hydrogen peroxide [2, 11] diols 13a‒f, monools
14a‒f, 15a‒f and phenol 7 were detected (Scheme 5). The ratio of diol and monools in each
experiment was ~ 1:1:1. The reaction between allylbenzene and PhBCl2 afforded, along with the
target 2-benzyl-1-phenylborirane 12g, 1-phenylpropene 16 (2:3 ratio), being a product of
catalytic isomerization of the initial α-olefin under the action of titanium complexes [14]
(Scheme 6).
Scheme 6. Cp2TiCl2-catalyzed reaction of allylbenzene with PhBCl2.
1
13
The identification of resulting products 12c‒g were based on the analysis of the Н, С,
and 11В NMR spectral data and products of oxidation with hydrogen peroxide in alkaline
medium.
To obtain more stable compounds and suitable for mass spectrometry analysis, we have
performed the reaction between 1-phenyl-2-octylborirane 12b and 4-methylmorpholine N-oxide
in order to incorporate the oxygen atom in the structure of boracyclane [15]. The resulting
product was analyzed by GC-MS. Its mass spectrum displayed mass peaks, which were exhibited
at 158 (decanol-1) and 94 (phenol), as well as the molecular ion peak at 259, 260, 261. This mass
may corresponds to the structure A or B.
3. Conclusion
In summary, for the first time, we have carried out direct cycloboration of α-olefins with
different chemical structure using PhBCl2 in ethereal solvents in the presence of metallic

7
ACCEPTED MANUSCRIPT
magnesium and Cp2TiCl2 as the catalyst. The developed method opens a simple and efficient
one-pot pathway to the synthesis of three-membered cyclic organoboron compounds, namely, 1-
phenyl-2-substituted boriranes from available and commonly used monomers.
4. Experimental section
All reactions were carried out using standard Schlenk techniques. Commercially available
PhBCl2 and Cp2TiCl2 were purchased from Acros Organics. Ethereal solvents (Et2O, THF)
employed were pre-dried over KOH, refluxed over sodium-wire for 2 h and distilled from
LiAlH4 in a stream of argon. The 1H, 13C, 11B and 2D homo- (COSY) and heteronuclear (HSQC,
HMBC) NMR spectra were recorded on a Bruker-Avance-400 spectrometer [400.13 (1H), 100.62
(13C), 128.33 (11B) MHz] (CDCl3). Chemical shifts (δ) are given in ppm relative to TMS, and the
1
coupling constants (J) in Hz. H and 13C NMR shifts were referenced to internal solvent
resonances and reported in parts per million (ppm) relative to Me4Si. 11B NMR spectra were
referenced to an external standard of BF3·Et2O.
Mass spectra were obtained on Shimadzu GCMS-QP2010 Ultra, capillary column Supelco
PTE-5 (60 m × 0.25 mm, carrier gas helium, ramp from 40 to 280°С at a rate 8 deg/min, ionizing
electrons energy 70 eV, injector temperature 260°С, ion source temperature 200°С).
The H2O2 oxidation of boriranes was done under alkaline conditions as described in [2,
10]. Spectral and physical characteristics of compounds (4−6, 13a−g, 14a−g, 15a−g, 16) have
been reported [16].
4.1. Synthesis of 2-hexyl-1-phenylborirane (3), 2-butyl-1-phenylborirane (12а), 2-octyl-1-
phenylborirane (12b).
General procedure. A glass reactor (50 mL), under a dry argon atmosphere at 0 °С, was
charged under stirring with Cp2TiCl2 (2 mmol, 0.498 g), magnesium (powder) (20 mmol, 0.486
g), Et2O (30 mL), the corresponding α-olefin (10 mmol) and PhBCl2 (12 mmol, 1.91 g). The
temperature was raised to 25 °С and the mixture was stirred for additional 14 h. Then the
reaction mixture was centrifuged, the excess of magnesium was filtered off, the diethyl ether was
evaporated, and 12 mmol of pyridine was added. The mixture was stirred for 30 min and placed
in a sublimation chamber. Pyridine was removed; the residue was subjected to vacuum
sublimation in an argon atmosphere.
Spectral data for 3: White solid. Yield: 75% (1.50 g, 7.5 mmol). 1H NMR (CDCl3, in ppm,
400.13 MHz):
C4НA), 1.75−1.78 (m, 1Н, C4НВ), 7.40‒7.72 (m, 4Н, Ph), 8.24‒8.40 (m, 1Н, Ph). 13С NMR
(CDCl3, in ppm, 100.62 MHz): = 14.30, 22.87, 29.51, 29.74, 32.04, 38.63, 128.17, 132.88,
135.84. 11B NMR (CDCl3, in ppm, 128.33 MHz): = 30.29. [In the 1H and 13C spectra signals of
δ
= 0.83−1.05 (m, 3Н, C9Н3), 1.06−1.53 (m, 8Н, С5−8Н2), 1.53‒1.58 (m, 1Н,
δ
δ

8
ACCEPTED MANUSCRIPT
protons and carbon atoms directly attached to the boron atom (B-CH2, B-CH-) were not
detected].
1
Spectral date for 12а: White solid. Yield: 80% (1.38 g, 8.0 mmol). H NMR (CDCl3, in
ppm, 400.13 MHz):
Ph), 7.55‒7.64 (m, 1Н, Ph), 8.24‒8.35 (m, 2Н, Ph). 13С NMR (CDCl3, in ppm, 100.62 MHz):
δ
= 0.89−0.99 (m, 3Н, C7Н3), 1.22−1.48 (m, 4Н, С5−6Н2), 7.29−7.39 (m, 2Н,
δ
=
14.32, 22.80, 31.96, 128.19, 132.92, 135.85. 11B NMR (CDCl3, in ppm, 128.33 MHz):
δ = 29.02.
1
[In the H and 13C spectra signals of protons and carbon atoms directly attached to the boron
atom (B-CH2, B-CH-) and C4H2 were not detected].
1
Spectral date for 12b: White solid. Yield: 70% (1.60 g, 7.0 mmol). H NMR (CDCl3, in
ppm, 400.13 MHz):
2Н, Ph), 7.50−7.60 (m, 1Н, Ph), 8.20 (m, 2Н, Ph). 13С NMR (CDCl3, in ppm, 100.62 MHz):
14.34, 22.91, 29.55, 29.73, 29.81, 29.92, 32.13, 128.21, 132.93, 135.87. 11B NMR (CDCl3, in
δ
= 0.91−1.01 (m, 3Н, C11Н3), 1.19−1.55 (m, 12Н, С5−10Н2), 7.20−7.30 (m,
δ
=
1
13
ppm, 128.33 MHz):
δ = 28.66. [In the H and C spectra signals of protons and carbon atoms
directly attached to the boron atom (B-CH2, B-CH-) and C4H2 were not detected].
4.2. Synthesis of 1,2-diphenylborirane (12с), 2-(2-methylphenyl)-1-phenylborirane (12d),
2-(3-methylphenyl)-1-phenylborirane (12e), 2-(4-methylphenyl)-1-phenylborirane (12f), 2-
benzyl-1-phenylborirane (12g).
General procedure. A glass reactor (50 mL), under a dry argon atmosphere at 0 °С, was
charged under stirring with Cp2TiCl2 (2 mmol, 0.498 g), magnesium (powder) (20 mmol, 0.486
g), Et2O (30 mL), the corresponding α-olefin (10 mmol) and PhBCl2 (12 mmol, 1.91 g). The
temperature was raised to 25 °С and the mixture was stirred for additional 14 h. The excess of
magnesium was filtered off, the diethyl ether was evaporated, and borirane analyzed by NMR.
Spectral date for 12c: Yield: 80%. 1H NMR (CDCl3, in ppm, 400.13 MHz):
δ = 7.01‒7.30
(m, 5Н, Ph), 7.35−7.60 (m, 3Н, Ph), 8.21 (m, 2Н, Ph). 13С NMR (CDCl3, in ppm, 100.62 MHz):
11
δ
= 125.30, 126.99, 127.10, 128.89, 131.90, 136.15, 144.10. B NMR (CDCl3, in ppm, 128.33
1
MHz):
δ
= 30.51. [In the H and 13C spectra signals of protons and carbon atoms directly
attached to the boron atom (B-CH2, B-CH-) were not detected].
Spectral date for 12d: Yield: 55%. 1H NMR (CDCl3, in ppm, 400.13 MHz):
δ = 2.25 (br, s,
3Н, MePh), 6.50‒6.75, 8.15‒8.30 (m, 9Н, Ar). 13С NMR (CDCl3, in ppm, 100.62 MHz):
δ =
19.19, 120.68, 125.91, 126.26, 126.57, 128.36, 128.88, 130.45, 135.95, 142.57. 11B NMR
1
(CDCl3, in ppm, 128.33 MHz):
δ
= 30.83. [In the H and 13C spectra signals of protons and
carbon atoms directly attached to the boron atom (B-CH2, B-CH-) were not detected].
Spectral date for 12e: Yield: 47%. 1H NMR (CDCl3, in ppm, 400.13 MHz):
= 2.34‒2.56
(br, s, 3Н, MePh), 6.70−6.85, 8.10−8.25 (m, 9Н, Ar). 13С NMR (CDCl3, in ppm, 100.62 MHz):
δ
δ

9
ACCEPTED MANUSCRIPT
= 22.36, 124.24, 126.03, 126.14, 127.98, 128.45, 130.57, 135.60, 138.80, 145.10. 11B NMR
1
(CDCl3, in ppm, 128.33 MHz):
δ
= 31.03. [In the H and 13C spectra signals of protons and
carbon atoms directly attached to the boron atom (B-CH2, B-CH-) were not detected].
Spectral date for 12f: Yield: 53%. 1H NMR (CDCl3, in ppm, 400.13 MHz):
= 2.44, 2.48
(br, s, 3Н, MePh), 7.10−7.70, 8.10‒8.30 (m, 9H, Ar). 13С NMR (CDCl3, in ppm, 100.62 MHz):
= 21.58, 123.44, 127.22, 127.63, 133.78, 134.80, 138.08, 144.32. 11B NMR (CDCl3, in ppm,
128.33 MHz):
= 30.98. [In the 1H and 13C spectra signals of protons and carbon atoms directly
δ
δ
δ
attached to the boron atom (B-CH2, B-CH-) were not detected].
Spectral date for 12g: Yield: 40%. 1H NMR (CDCl3, in ppm, 400.13 MHz):
δ = 2.85−2.90
(m, 1Н, C4НА), 3.02−3.10 (m, 1Н, C4НВ), 7.42‒7.90, 8.45−8.50 (m, 9Н, Ar). 13С NMR (CDCl3,
11
in ppm, 100.62 MHz):
δ
= 38.41, 125.65, 127.73, 128.25, 128.65, 131.34, 135.66, 142.42. B
NMR (CDCl3, in ppm, 128.33 MHz):
δ
= 31.13. [In the 1H and 13C spectra signals of protons and
carbon atoms directly attached to the boron atom (B-CH2, B-CH-) were not detected].
4.3. Synthesis of pyridinium 2-hexyl-1-phenylboriran-1-ide (3·Py).
A glass reactor (50 mL), under a dry argon atmosphere at 0 °С, was charged under stirring
with Cp2TiCl2 (2 mmol, 0.498 g), magnesium (powder) (20 mmol, 0.486 g), Et2O (30 mL), oct-
1-en (10 mmol) and PhBCl2 (12 mmol, 1.91 g). The temperature was raised to 25 °С and the
mixture was stirred for additional 14 h. Then the excess of magnesium was filtered off, the
diethyl ether was evaporated, equimolar amount of pyridine was added, and borirane analyzed by
NMR. 1H NMR (CDCl3, in ppm, 400.13 MHz):
δ
= 0.68−0.85 (m, 3Н, C9Н3), 1.01−1.50 (m, 8Н,
С5−8Н2), 7.00‒7.30, 7.40‒7.60, 7.97‒8.05, 8.53‒8.85 (m, 10Н, Py, Ph). 13С NMR (CDCl3, in
ppm, 100.62 MHz):
δ = 13.69, 22.25, 29.00, 29.01, 31.50, 124.29, 127.09, 129.09, 133.18,
11
1
13
136.14, 148.50. B NMR (CDCl3, in ppm, 128.33 MHz):
δ = 2.10. [In the H and C spectra
signals of protons and carbon atoms directly attached to the boron atom (B-CH2, B-CH-) and
C4H2 were not detected].
4.4. Synthesis of 2-hexyl-1-phenylborirane (3) in·THF.
A glass reactor (50 mL), under a dry argon atmosphere at 0 °С, was charged under stirring
with Cp2TiCl2 (2 mmol, 0.498 g), magnesium (powder) (40 mmol, 0.972 g), tetrahydrofuran (30
mL), the corresponding α-olefin (10 mmol) and PhBCl2 (20 mmol, 3.18 g). The temperature was
raised to 25 °С and the mixture was stirred for additional 14 h. The excess of magnesium was
1
filtered off, the tetrahydrofuran was evaporated, and borirane analyzed by NMR. H NMR
(CDCl3, in ppm, 400.13 MHz):
δ
= 0.90−1.06 (m, 3Н, C9Н3), 1.20−1.43 (m, 8Н, С5−8Н2),
13
1.53‒2.05 (m, THF), 3.50−3.68 (m, THF), 6.90‒7.92 (m, 4Н, Ph), 8.14‒8.35 (m, 1Н, Ph). С
NMR (CDCl3, in ppm, 100.62 MHz):
δ = 14.16, 22.70, 25.17 (THF), 29.35, 29.60, 31.95, 69.45

10
ACCEPTED MANUSCRIPT
11
1
(THF), 127.64, 130.72, 133.35. B NMR (CDCl3, in ppm, 128.33 MHz):
δ
= 2.84. [In the H
and 13C spectra signals of protons and carbon atoms directly attached to the boron atom (B-CH2,
B-CH-) and C4H2 were not detected].
Acknowledgement
This research was supported by Russian Foundation for Basic Research (projects № 14-03-
00295) and Government of the Russian Federation (NSh-6651.2016.3). The structural studies of
compounds were performed with the use of Collective Usage Centre “Agidel” at the Institute of
Petrochemistry and Catalysis of RAS.
References
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Highlights
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Cp2TiCl2 catalyzes cycloboration of α-olefins with PhBCl2.
Phenyl-substituted boriranes are the final products.