New boron reagents for cycloboration of α-olefins into boriranes under Cp2TiCl2 catalysis

Article abstract of DOI:10.1016/j.jorganchem.2018.08.005

The one-pot cycloboration of α-olefins (oct-1-ene, dec-1-ene) for a facile access to substituted boriranes has been carried out with the use of alkyl, arylalkyl, and cycloalkyl boron dichlorides (EtBCl₂, n-PentBCl₂, n-HexBCl₂, Ph(CH₂)₂BCl₂, cyclo-OctBCl₂, 2-norbornylBCl₂) under Cp₂TiCl₂ catalysis.

Full text of DOI:10.1016/j.jorganchem.2018.08.005

Accepted Manuscript
New boron reagents for cycloboration of α-olefins into boriranes under Cp TiCl
2
2
catalysis
Liliya I. Khusainova, Leila O. Khafizova, Tatyana V. Tyumkina, Kirill S. Ryazanov,
Natalya R. Popodko, Usein M. Dzhemilev
PII:
S0022-328X(18)30706-X
10.1016/j.jorganchem.2018.08.005
JOM 20532
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 4 April 2018
Revised Date: 7 August 2018
Accepted Date: 9 August 2018
Please cite this article as: L.I. Khusainova, L.O. Khafizova, T.V. Tyumkina, K.S. Ryazanov,
N.R. Popodko, U.M. Dzhemilev, New boron reagents for cycloboration of α-olefins into
boriranes under Cp TiCl catalysis, Journal of Organometallic Chemistry (2018), doi: 10.1016/
2
2
j.jorganchem.2018.08.005.
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1
ACCEPTED MANUSCRIPT
New boron reagents for cycloboration of α-olefins into boriranes
under Cp TiCl catalysis
2
2
*
Liliya I. Khusainova, Leila O. Khafizova, Tatyana V. Tyumkina,
Kirill S. Ryazanov, Natalya R. Popodko, Usein M. Dzhemilev
Institute of Petrochemistry and Catalysis of Russian Academy of Sciences,
141 Prospekt Oktyabrya, Ufa 450075, Russian Federation
Abstract
The one-pot cycloboration of α-olefins (oct-1-ene, dec-1-ene) for a facile access to
substituted boriranes has been carried out with the use of alkyl, arylalkyl, and cycloalkyl
boron dichlorides (EtBCl , n-PentBCl , n-HexBCl , Ph(CH ) BCl , cyclo-OctBCl , 2-
2
2
2
2 2
2
2
norbornylBCl ) under Cp TiCl catalysis.
2
2
2
Keywords
Boriranes,
α-olefins,
cycloboration,
catalysis,
titanacyclopropane,
dichloroboranes
1
. Introduction
The three-membered heterocycles such as azacyclopropanes (aziridines) [1],
oxacyclopropanes (oxiranes) [2], thiacyclopropanes (thiiranes) [3], silacyclopropanes (siliranes)
[4] are readily available and have a rich chemistry. In contrast, boron analogs of cyclopropanes
(boracyclopropanes, or boriranes) are more rare [5], presumably because they combine two
features − ring strain and Lewis acidity − that often impart reactivity. For the first time, Berndt
A. and Klusik H. have synthesized boriranes in 1983 [6]. Later, Denmark has synthesized
pyridine complexes of boriranes [7], and Braunschweig [8] and Wang [9] have recently prepared
a number of stable NHC-substituted boriranes. In 2017, D. Curran has reported a direct synthesis
of NHC-boriranes by reactions of dimethyl acetylenedicarboxylate with NHC-boranes [10].
However, before our investigations, catalytic methods for producing boriranes via cycloboration
of unsaturated compounds have not been discussed
.
*
Corresponding author. Fax: +73472842750;
e-mail: khafizovaleila@gmail.com (L.O. Khafizova).

2
ACCEPTED MANUSCRIPT
Recently, for the first time, we have carried out direct cycloboration of α-olefins with
complexes of boron trihalides (BCl ·SMe and BF ·THF) in the presence of Mg and Cp TiCl
2
3
2
3
2
catalyst [11] (Scheme 1) to afford appropriate 1-fluoro(chloro)-2-substituted boriranes 1 and 2.
Scheme 1. Synthesis of 1-flouro(chloro)-2-substituted boriranes from α-olefins and
BF ·THF (or BCl ·SMe ) in the presence of Cp TiCl
2.
3
3
2
2
The experimental data on the preparation of 1-chloroboriranes [11a] are in good
agreement with the results of our theoretical modeling of the mechanism of the one-pot
formation of boriranes from α-olefins and BCl , the key step of which is the replacement of the
3
transition metal atom by the boron atom in the titanacyclopropane intermediate [12]. The
1
13
11
identification of boriranes using multinuclear H, C and B NMR spectroscopy is difficult due
to the lack of signals of endo-cyclic carbon and hydrogen atoms. In addition, chemical shift
1
1
values of boron atoms in B NMR spectra described in the literature for boriranes vary in a wide
range from -1 to +38 ppm [6, 11]. Mass-spectrometry analysis is often unsuitable for the
identification because of the low stability of many boriranes.
Based on the results of the quantum-chemical DFT investigations we have predicted that
along with BCl , aryl(alkyl) boron dichlorides may also serve as transmetallating reagents [12].
3
Later, we have successfully implemented reactions of α-olefins with PhBCl in the presence of
2
metallic magnesium and catalytic amounts of Cp TiCl producing 1-phenyl-2-substituted
2
2
borirans 3 (Scheme 2) [13].
Scheme 2. Cp TiCl -catalyzed cycloboration of α-olefins with PhBCl .
2
2
2
In this paper, we report the results of our further investigations into the structure of initial
R-substituted boron dichlorides and the cycloboration reaction with the participation of α-olefins
under Cp TiCl catalysis.
2
2

3
ACCEPTED MANUSCRIPT
. Results and discussion
2
In order to study the effect of structure of the starting boron dichlorides on the yield and
selectivity of the formation of the three-membered organoboron compounds, we have studied the
reaction of diverse boron dichlorides with acyclic and cyclic olefins in the presence of Cp TiCl2
2
catalyst.
Alkyl boron dichlorides (EtBCl , PentBCl , HexBCl ) and arylalkyl boron dichlorides
2
2
2
(
Ph(CH ) BCl , Naphth(CH ) BCl ) have been selected as the objects of study.
2 2 2 2 2 2
Thus, the reaction of α-olefins (oct-1-ene, dec-1-ene) with alkyl boron dichlorides under
the reaction conditions (olefin: [B]: [Mg]: [Ti] = 1 : 1.2 : 2 : 0.2, THF, 50 ºC for 5h, then ~ 22-25
ºC for 16 h) afforded 1,2-dialkyl boriranes 4a-e in 67‒82% yield, which have been isolated and
identified by spectral and chemical methods (Scheme 3).
Scheme 3. Alkyldichloroboranes in the cycloboration reaction of α-olefins.
Along with borirans 4a-e, under this reaction conditions, small amounts of 2-alkyl-1,2-
oxaborinanes 5a,b (10-12%) have been detected. Formation of 5a,b, apparently, occurs with the
participation of THF, which is used in the reaction as a solvent.
The oxidation of 1,2-dialkylboriranes 4a-d (H O , NaOH) [11‒14] led to the
2
2
corresponding diols 6a‒e and monools 7‒9 in a ratio of 1:1:1:1 (Scheme 4).

4
ACCEPTED MANUSCRIPT
Scheme 4. Oxidation of 1,2-dialkylboriranes.
It should be noted that in contrast to the Cp TiCl -catalyzed cycloboration reactions of α-
2
2
olefins with PhBCl , BCl ·SMe or BF ·THF, which occur at room temperature, the reactions
2
3
2
3
involving alkyldichloroboranes occur only when heated to 50 °C. Experiments have shown that
dichloro[(2-phenyl)ethyl]borane (Ph(CH ) BCl ), hardly reacts with α-olefins in the
2
2
2
cycloboration reaction even at elevated temperatures (50‒100 °С). The formation 1-(2-
phenylethyl)-2-hexylborirane was confirmed only by the oxidation products (octane-1,2-diol 6a,
octan-1-ol 7a, octan-2-ol 8a, 2-phenylethanol 10). Dichloro[2-(2-naphthyl)ethyl]borane
(
Naphth(CH ) BCl ) does not give rise to the desired boriranes under selected reaction
2 2 2
conditions.
Apparently, the low reactivity of arylalkyldichloroboranes is associated with an increase
in the energy barrier at the intramolecular cyclization stage compared with that calculated for
BCl3 [12]. The calculated energy barrier (or energy of activation, Ea) is ~20 kcal /mol for the
reactions, which occur at room temperature. high-energy barriers (more than 20 kcal /mol) at the
stages of borirane formation. We have performed a series of DFT calculations for the
cycloboration reaction according to the proposed mechanism [12] including the insertion of the
boron-containing compound (BnBCl and PhBCl ) into the cyclopropane intermediate and
2
2
subsequent intramolecular cyclization to give the corresponding borirane. It turned out that the
experiment is in good agreement with the theoretical data about the lack of reactivity of
alkyldichloroboranes as compared to PhBCl (see Support. inform. pp. 19), although, it is
2
difficult to analyze different reactivity of alkyldichloroborane and Ph(CH CH )BCl in the direct
2
2
2
cycloboration reaction of α-olefins with organoboron reagents.
Along with alkyl boron dichlorides and arylalkyl boron dichlorides, we have synthesized
aliphatic cycloalkyldichloroboranes, namely, cyclooctyldichloroborane 11 and exo-
norbornyldichloroborane 12, which have been successfully involved in the Cp TiCl -catalyzed
2
2
cycloboration reaction of α-olefins giving rise to 2-alkyl-1-cyclooctyl(norbornyl)boriranes 13a,b
and 14a,b (Scheme 5). Oxidation of boriranes 13a,b and 14a,b under basic conditions
(
H O /NaOH) led to the expected diols 6a,d and monools 7a,d, 8a,d, 15 and 16.
2 2

5
ACCEPTED MANUSCRIPT
R
R
11
BCl2
12
BCl2
B
B
R
i
i
14a,b
1
3a,b
i: Cp TiCl (20 mol%), Mg, THF
2 2
ii: H O , OH
C
2
2
a: R = Hex
b: R = Oct
ii
ii
R
OH
R
OH
OH
OH
+
+
+
OH
+
+
+
OH
R
R
R
R
HO
OH
HO
OH
6
a d
7a,d
8a,d
15
6a,d
7a,d
8a,d
16
Scheme 5. Cyclooctyl- and exo-norbornyldichloroboranes in the cycloboration reaction
of α-olefins.
The structures of boriranes 4a‒e and 13a,b obtained by vacuum distillation have been
1
13
11
1
13
confirmed by multinuclear ( Н, С, В) NMR spectroscopy. In H and C NMR spectra of
boriranes 4a‒e and 13a,b signals of carbon and hydrogen atoms, which occupy α-position, i.e.
adjacent to the boron atom, do not occur, obviously, due to quadrupole broadening effects of the
boron nuclei [15], which is characteristic for three-membered boracyclanes [6,11b,13,16]. The
1
1
B NMR spectra (СDCl ) demonstrate expected broadened signals at δ ~31 ppm, which agrees
3
well with the spectral data for alkyl substituted boriranes in СDCl described in the literature
3
[
6,12,13]. The resulting boriranes was analyzed by GC-MS. So, for example, mass spectrum of
+
borirane 4d displayed mass peaks, which were exhibited at 240 (C H BO ), 112 [M ‒H O]
1
4
29
2
2
+
(
C H O ‒ octan-1-ol and octan-2-ol) and 84 [M ‒H O] (hexan-1-ol). All these peaks are
8 18 2
consistent with oxidation and hydrolysis products, arising from 4d in the mass spectrometer.
Similar results have been obtained for the whole series of the synthesized boriranes.
However, the NMR spectra of the expected boriranes 14a,b, along with the signals
attributed to the alkyl substituent and the norbornyl moiety, show the signals of the tertiary
carbon atom of the norbornane skeleton at δ 74 ppm thus indicating the incorporation of an
C
oxygen atom through the B‒C bond with retention of the boracyclopropane fragment. Obviously,
1
-norbornyl-2-alkylboriranes 14a,b being formed under the reaction conditions are very sensitive
to even trace amounts of air oxygen, and therefore 1-(bicyclo[2.2.1]hept-2-yloxy)-2-
alkylboriranes 17a,b have been identified as final products after isolation of the desired product
by distillation.

6
ACCEPTED MANUSCRIPT
R
B
O
1
7a,b
3
. Conclusion
In summary, we have successfully carried out direct cycloboration of a-olefins with new
boron reagents, namely, ethyl-, n-pentyl-, n-hexyl-, phenylethyl-, cyclooctyl-, and exo-norbornyl
boron dichlorides in THF in the presence of metallic magnesium and Cp TiCl as the catalyst.
2
2
For the first time, 1-alkyl(cycloalkyl)-2-alkyl substituted boriranes have been synthesized from
available and commonly used monomers with good yields.
4
. Experimental section
All reactions were carried out using standard Schlenk techniques. Commercially available
olefins, HBCl ·SMe , BCl (1 M solution in hexane), Et B and Cp TiCl (Aldrich) were used.
2
2
3
3
2
2
THF employed were pre-dried over KOH, refluxed over sodium-wire for 2 h and distilled from
LiAlH in a stream of argon. Reactions with organometallic compounds were performed in a dry
4
argon flow.
1
13
11
The H, C, B and 2D homo- (COSY) and heteronuclear (HSQC, HMBC) NMR spectra
1
13
were measured in CDCl on a Bruker Avance-400 spectrometer [400.13 ( H), 100.62 ( C),
3
1
1
1
28.33 ( B) MHz]. Chemical shifts (δ) are given in ppm relative to TMS, and the coupling
1
13
constants (J) in Hz. H and C NMR shifts were referenced to internal solvent resonances and
11
reported in parts per million (ppm) relative to Me Si. B NMR spectra were referenced to an
4
external standard of BF ·Et O.
3
2
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 H O oxidation of boriranes was done under alkaline conditions as described in Refs.
2
2
[
11‒14]. Spectral and physical characteristics of compounds (6, 7, 8, 9, 15, 16) have been
reported [17].
4
.1. Synthesis of n-PentBCl , n-HexBCl , Ph(CH ) BCl , Naphth(CH ) BCl , cyclo-OctBCl (11),
2 2 2 2 2 2 2 2 2
exo-2-norbornylBCl (12) as complexes with SMe .
2
2

7
ACCEPTED MANUSCRIPT
4
.1.1. General procedure.
Boron dichlorides, RBCl (R = n-Pent, n-Hex, Ph(CH ) , Naphth(CH ) , cyclo-Oct, exo-
2
2 2
2 2
norbornyl) were synthesized as complexes with SMe according to the method as described in
2
Ref. [18]. Spectral assignments for dichloroborane‒dimethyl sulfides reagent have been made for
the first time.
4
.1.1.1. Spectral data for n-pentyldichloroborane-dimethyl sulfide. Colorless steaming liquid, bp
-1
1
61 ºC. IR spectrum, ν, cm : 2958, 2928, 2871, 2861, 1459, 1383, 1220, 1180, 1038, 908, 824,
1
7
33, 649. H NMR (CDCl , in ppm, 400.13 MHz):
δ
= 0.84−0.94 (m, 5Н, B‒CН , CН ),
3
2
3
13
1
.25−1.36 (m, 4Н, 2СН ), 1.37‒1.48 (m, 2Н, CН ), 2.38 (br.s, 6Н, Me S). С NMR (CDCl , in
2 2 2 3
11
ppm, 100.62 MHz):
δ
= 13.97, 19.58 (br, Me S), 22.44, 24.90, 26.06 (br, B−CH ), 34.61. B
2
2
NMR (CDCl , in ppm, 128.33 MHz):
δ
= 11.66.
3
4
1
1
5
.1.1.2. Spectral data for n-hexyldichloroborane-dimethyl sulfide. Colorless steaming liquid, bp
-1
69 ºC. IR spectrum, ν, cm : 2960, 2935, 2927, 2870, 2861, 1455, 1458, 1380, 1210, 1221,
1
185, 1050, 900, 833, 820, 730, 699. H NMR (CDCl , in ppm, 400.13 MHz):
δ = 0.86−0.94 (m,
3
1
3
Н, B‒CН , CН ), 1.25−1.38 (m, 6Н, 3СН ), 1.40‒1.48 (m, 2Н, CН ), 2.38 (br.s, 6Н, Me S). С
2
3
2
2
2
NMR (CDCl , in ppm, 100.62 MHz):
δ = 14.12, 19.48 (br, Me S), 22.62, 25.29, 25.77 (br,
2
3
1
1
B−CH ), 31.76, 32.17. B NMR (CDCl , in ppm, 128.33 MHz): δ = 10.87.
2
3
4
.1.1.3. Spectral data for cyclooctyldichloroborane-dimethyl sulfide 11. Colorless steaming
-1
liquid, bp 90 ºC (10 mm). IR spectrum, ν, cm : 2870, 2848, 2350, 2218, 2111, 1461, 1401, 1355,
1
1
248, 1211, 1209, 1180, 1135, 1039, 960, 850, 801, 730, 621. H NMR (CDCl , in ppm, 400.13
3
A
MHz):
δ
= 0.90‒1.02 (m, 1Н, B‒CН), 1.41‒1.67 (m, 10Н, 2CH , 4СН ), 1.67−1.84 (m, 4Н,
2
B
13
2
СН , СН ), 2.40 (br.s, 6Н, Me S). С NMR (CDCl , in ppm, 100.62 MHz):
δ
= 19.66 (br,
2
2
3
1
1
Me S), 26.47, 27.23, 27.35, 29.50, 30.03 (br, B‒CH). B NMR (CDCl , in ppm, 128.33 MHz):
δ
2
3
=
13.30.
4
.1.1.4. Spectral data for exo-2-norbornyldichloroborane-dimethyl sulfide 12. Pale yellow
-1
steaming liquid, bp 112 ºC (40 mm). IR spectrum, ν, cm : 2951, 2869, 2359, 2253, 1454, 1372,
1
1
4
265, 1219, 1199, 1149, 1108, 1033, 950, 908, 834, 735, 650, 546. H NMR (CDCl , in ppm,
3
2
7
А 2
00.13 MHz):
δ = 0.86 (t, 1Н, B‒C Н, J = 8.2 Hz), 1.06 (d, 1Н, С Н , J = 9.5 Hz), 1.16−1.19
5
А
6
А
3
A
3
B
5
B
6
B
(
m, 2Н, С Н , С Н ), 1.29‒1.36 (m, 1Н, C Н ), 1.46−1.57 (m, 3Н, С Н , С Н , С Н ), 1.70 (dt,

8
ACCEPTED MANUSCRIPT
7
B
4
4
1
13
1
Н, С Н , J = 1.9 Hz), 2.25 (br.s, 1Н, C H), 2.26 (br.s, 1Н, C H), 2.36 (br.s, 6Н, Me S). С
2
5
6
3
NMR (CDCl , in ppm, 100.62 MHz):
δ = 20.25 (br, Me S), 28.68 (C ), 33.67 (C ), 34.38 (C ),
2
3
2
4
7
1
11
3
6.42 (br, B‒C H), 36.73 (C ), 36.89 (C ), 39.36 (C ). B NMR (CDCl , in ppm, 128.33 MHz):
3
δ
= 12.15.
4
.2. Synthesis of 1-ethyl-2-hexylborirane (4а), 1-ethyl-2-octylborirane (4b), 2-octyl-1,2-
oxaborinane (5a), 2-decyl-1,2-oxaborinane (5b)
4
.2.1. General procedure.
A glass reactor (50 mL), under a dry argon atmosphere at 0 °С, was charged under
stirring with Cp TiCl (2 mmol, 0.498 g), magnesium (powder) (20 mmol, 0.486 g), THF (30
2
2
mL), the corresponding α-olefin (10 mmol) and EtBCl (12 mmol). EtBCl was synthesized
2
2
according to the methods as described in Refs. [19]. The temperature was raised to 55‒60 °С and
the mixture was stirred 5 h. Then reaction mixture was cooled to room temperature (~ 20‒22 ºC)
and was stirred for additional 16 h. Then the reaction mixture was centrifuged, the excess of
magnesium was filtered off, the solvent was evaporated and the residue was distilled under
reduced pressure in a stream of argon.
4
.2.1.1. Spectral date for 1-ethyl-2-hexylborirane 4а. Yield: 82% (1.25 g, 8.2 mmol). Pale
-
yellow liquid, bp 72 ºC (10 mm). IR spectrum, ν, cm 1: 2960, 2901, 2855, 1490, 1410, 1350,
1
1
0
1
211, 1101, 1050, 980, 905, 890, 765, 725, 693. H NMR (CDCl , in ppm, 400.13 MHz):
δ
=
3
1
3
.85−0.98 (m, 6Н, CH , B-CH -CH ), 1.22−1.52 (m, 8Н, 4CH ). С NMR (CDCl , in ppm,
3
2
3
2
3
1
1
00.62 MHz):
δ = 7.92 (B-CH -CH ), 14.06, 22.63, 29.25, 29.34, 31.80. B NMR (CDCl , in
2 3 3
1
13
ppm, 128.33 MHz):
δ = 31.34. [In the H and C spectra signals of protons and carbon atoms
2
3
4
directly attached to the boron atom (B-С H, B-C H (cycle), B-СH ) and C H were not
2
2
2
detected].
4
.2.1.2. Spectral date for 1-ethyl-2-octylborirane 4b. Yield: 80% (1.44 g, 8.0 mmol). Pale yellow
-1
liquid, bp 86 ºC (10 mm). IR spectrum, ν, cm : 2955, 2854, 1481, 1460, 1415, 1333, 1219, 1119,
1
1
0
1
076, 1051, 968, 910, 895, 793, 762, 722, 665. H NMR (CDCl , in ppm, 400.13 MHz):
δ
=
3
1
3
.87−0.95 (m, 6Н, CH , B-CH -CH ), 1.20‒1.46 (m, 12Н, 6CH ). С NMR (CDCl , in ppm,
3
2
3
2
3
11
00.62 MHz):
δ = 7.83 (B-CH -CH ), 14.06, 22.69, [(29.38, 29.62, 29.67) 4C], 31.94. B NMR
2 3
1
13
(
CDCl , in ppm, 128.33 MHz): δ = 31.36. [In the H and C spectra signals of protons and
3
2
3
4
carbon atoms directly attached to the boron atom (B-С H, B-C H (cycle), B-СH ) and C H
2
2
2
were not detected].

9
ACCEPTED MANUSCRIPT
4
1
1
.2.1.3. Spectral date for 2-octyl-1,2-oxaborinane 5a. Yellow oil liquid, bp 75 ºC (1 mm). Yield:
-1
0% (0.20 g, 1.0 mmol). IR spectrum, ν, cm : 2925, 2855, 1458, 1416, 1332, 1296, 1209, 1180,
1
077, 1049, 893, 793, 722. H NMR (CDCl , in ppm, 400.13 MHz):
δ = 0.74 (t, 2Н, B-CH2,
3
cycle, J = 7.8 Hz), 0.88 (t, 3Н, CH , J = 6.2 Hz), 0.97 (t, 2Н, B-CH , alkyl, J = 7.8 Hz), 1.26 (m,
3
2
1
5
2
2Н, 6CH , alkyl), 1.55 (m, 2H, CH , cycle), 1.64 (m, 2H, CH , cycle), 4.04 (t, 2H, O-CH , J =
2 2 2 2
1
3
.8 Hz). С NMR (CDCl , in ppm, 100.62 MHz):
δ = 14.27, 16.09 (br, B-CH , cycle), 19.42,
2
3
1
1
2.21 (br, B-CH , alkyl), 22.92, 24.24, 28.23, 29.56, 29.81, 32.20, 32.98, 66.48. B NMR
2
+
(
CDCl , in ppm, 128.33 MHz):
δ
= 52.73. MS m/z: 196 [M] .
3
4
1
1
2
.2.1.4. Spectral date for 2-decyl-1,2-oxaborinane 5b. Yellow oil liquid, bp 88 ºC (1 mm). Yield:
-1
2% (0.27 g, 1.2 mmol). IR spectrum, ν, cm : 2918, 2835, 1460, 1425, 1415, 1341, 1300, 1211,
1
155, 1089, 1040, 888, 795, 730, 702, 695. HMR (CDCl , in ppm, 400.13 MHz):
δ = 0.75 (t,
3
Н, B-CH , cycle, J = 7.8 Hz), 0.89 (t, 3Н, CH , J = 6.5 Hz), 0.98 (t, 2Н, B-CH , alkyl, J = 7.0
2
3
2
Hz), 1.27 (m, 16Н, 8CH , alkyl), 1.56 (m, 2H, CH , cycle), 1.64 (m, 2H, CH , cycle), 4.06 (t, 2H,
2
2
2
1
3
O-CH , J = 5.4 Hz). С NMR (CDCl , in ppm, 100.62 MHz):
δ
= 14.11, 15.92 (br, B-CH2,
2
3
cycle), 19.18, 21.89 (br, B-CH , alkyl), 22.70, 24.05, 27.98, 29.32, 29.58, 29.66, 29.69, 31.96,
2
1
1
+
3
2.76, 66.34. B NMR (CDCl , in ppm, 128.33 MHz): δ = 52.76. MS m/z: 224 [M] .
3
4
.3. Synthesis of 1-pentyl-2-hexylborirane (4c), 1,2-dihexylborirane (4d), 1-pentyl-2-
octylborirane (4e), 1-cyclooctyl-2-hexylborirane (13a), 1-cyclooctyl-2-octylborirane (13b), 1-
bicyclo[2.2.1]hept-2-yloxy)-2-hexylborirane (17a), 1-(bicyclo[2.2.1]hept-2-yloxy)-2-
octylborirane (17b)
(
4
.3.1. General procedure
A glass reactor (50 mL), under a dry argon atmosphere at 0 °С, was charged under
stirring with Cp TiCl (2 mmol, 0.498 g), magnesium (powder) (20 mmol, 0.486 g), THF (30
2
2
†
mL), the corresponding α-olefin (10 mmol) and RBCl ·SMe (12 mmol). The temperature was
2
2
raised to 55‒60 °С and the mixture was stirred 5 h. Then reaction mixture was cooled to room
temperature (~ 20‒22 ºC) and was stirred for additional 16 h. Then the reaction mixture was
centrifuged, the excess of magnesium was filtered off, the solvent was evaporated and the
residue was distilled under reduced pressure in a stream of argon.
†
Initial boron dichlorides were involved in the reaction as complexes with SMe [18] because they are more stable
2
and resistant to oxidation. The isolated in vacuum boriranes did not contain SMe in their structure as in the case
2
with individual RBCl2.

1
0
ACCEPTED MANUSCRIPT
4
.3.1.3. Spectral date for 1-pentyl-2-hexylborirane 4c. Yield: 77% (1.50 g, 7.7 mmol). Pale
-1
yellow liquid, bp 107 ºC (10 mm). IR spectrum, ν, cm : 2940, 2920, 2833, 2801, 1501, 1490,
1
1
315, 1310, 1056, 1015, 1009, 932, 850, 724, 650. H NMR (CDCl , in ppm, 400.13 MHz):
δ
=
3
13
0
.90 (t, 6Н, 2CH , J = 6.4 Hz), 1.10−1.50 (m, 12Н, 6CH ), 1.50−1.70 (m, 2Н, CH ). С NMR
3
2
2
(
CDCl , in ppm, 100.62 MHz):
δ
= 14.29 (2С), 22.68, 22.87, [(29.50, 29.59) 3C], 32.05, 32.14.
3
1
1
1
13
B NMR (CDCl , in ppm, 128.33 MHz):
δ = 31.70. [In the H and C spectra signals of protons
3
2
3
4
and carbon atoms directly attached to the boron atom (B-С H, B-C H (cycle), B-СH ) and C H
2
2
2
were not detected].
4
.3.1.4. Spectral date for 1,2-dihexylborirane 4d. Yield: 67% (1.40 g, 6.7 mmol). Pale yellow
-1
liquid, bp 80 ºC (2 mm). IR spectrum, ν, cm : 2955, 2924, 2855, 1458, 1415, 1332, 1077, 1055,
1
1
029, 909, 892, 800, 723, 665. H NMR (CDCl , in ppm, 400.13 MHz):
δ
= 0.84‒0.90 (m, 6Н,
3
1
3
2
CH ), 1.27‒1.42 (m, 14Н, 7CH ), 1.50‒1.65 (m, 2Н, CH ). С NMR (CDCl , in ppm, 100.62
3
2
2
3
1
1
MHz):
in ppm, 128.33 MHz):
directly attached to the boron atom (B-С H, B-C H (cycle), B-СH ) and C H were not
δ = 14.02, 14.08, 22.64 (2C), [(29.27, 29.38) 3C], 31.62, 31.83, 31.94. B NMR (CDCl ,
3
1
13
δ
= 31.25. [In the H and C spectra signals of protons and carbon atoms
2
3
4
2
2
2
detected].
4
.3.1.5. Spectral date for 1-pentyl-2-octylborirane 4e. Yield: 74% (1.64 g, 7.4 mmol). Pale
-1
yellow liquid, bp 85 ºC (2 mm). IR spectrum, ν, cm : 2947, 2935, 2923, 2855, 1460, 1458, 1450,
1
1
330, 1081, 1054, 1033, 1032, 990, 908, 892, 810, 727, 631. H NMR (CDCl , in ppm, 400.13
3
13
MHz):
δ = 0.85‒0.95 (m, 6Н, 2CH ), 1.23‒1.60 (m, 18Н, 9CH ). С NMR (CDCl , in ppm,
3 2 3
1
1
1
00.62 MHz):
δ = 14.09 (2С), 22.46, 22.67, [(29.29, 29.35, 29.61, 29.65) 5C], 31.90 (2C). B
1
13
NMR (CDCl , in ppm, 128.33 MHz):
δ
= 30.66. [In the H and C spectra signals of protons and
3
2
3
4
carbon atoms directly attached to the boron atom (B-С H, B-C H (cycle), B-СH ) and C H
2
2
2
were not detected].
4
.3.1.6. Spectral date for 1-cyclooctyl-2-hexylborirane 13a. Pale yellow liquid, bp 110 ºC (1
1
mm). Yield: 70% (1.64 g, 7.0 mmol). H NMR (CDCl , in ppm, 400.13 MHz):
δ = 0.90 (t, 3Н,
3
13
CH , J = 6.2 Hz), 1.20−1.80 [m, 22Н, 4CH (alkyl), 7CH (cyclooctyl)]. С NMR (CDCl , in
3
2
2
3
ppm, 100.62 MHz):
δ = 14.11, 22.68, 25.54 (cyclooctyl), 26.65 (cyclooctyl), 26.83 (cyclooctyl),
1
1
2
9.37, 29.70, 30.78 (cyclooctyl), 31.92. B NMR (CDCl , in ppm, 128.33 MHz): δ = 32.01. [In
3
1
13
the H and C spectra signals of protons and carbon atoms directly attached to the boron atom (2
4
B-СH, B-CH ) and C H were not detected].
2
2

1
1
ACCEPTED MANUSCRIPT
4
.3.1.7. Spectral date for 1-cyclooctyl-2-octylborirane 13b. Pale yellow liquid, bp 120 ºC (1
1
mm). Yield: 68% (1.78 g, 6.8 mmol). H NMR (CDCl , in ppm, 400.13 MHz):
δ = 0.89 (t, 3Н,
3
13
CH , J = 6.4 Hz), 1.22−1.89 [m, 26Н, 6CH (alkyl), 7CH (cyclooctyl)]. С NMR (CDCl , in
3
2
2
3
ppm, 100.62 MHz):
δ = 14.09, 22.65, 25.40 (cyclooctyl), 26.71 (cyclooctyl), 26.91 (cyclooctyl),
11
[
29.25, 29.37, 29.70 (4C)], 31.05 (cyclooctyl), 31.86. B NMR (CDCl , in ppm, 128.33 MHz): δ
3
1
13
=
32.38. [In the H and C spectra signals of protons and carbon atoms directly attached to the
4
boron atom (2 B-СH, B-CH ) and C H were not detected].
2
2
4
.3.1.8. Spectral date for 1-(bicyclo[2.2.1]hept-2-yloxy)-2-hexylborirane 17a. Yellow oil liquid,
1
bp 103 ºC (1 mm). Yield: 75% 1.76 g, 7.5 mmol). H NMR (CDCl , in ppm, 400.13 MHz):
δ =
3
0
.90 (t, 3Н, СН , J = 6.2 Hz), 1.00‒1.19 (m, 3Н, 3CH), 1.20‒1.75 (m, 15H, 3CH, 6CH ), 2.15
3 2
1
3
(
m, 1H, CH), 2.23 (m, 1H, CH), 4.02 (m, 1H, O‒CH). С NMR (CDCl , in ppm, 100.62 MHz):
3
δ
= 14.08 (alkyl), 22.65 (alkyl), 24.36, 28.35, 29.28 (alkyl), 29.36 (alkyl), 31.83 (alkyl), 31.90
11
(
alkyl), 34.82, 35.38, 42.13, 43.64, 75.25. B NMR (CDCl , in ppm, 128.33 MHz):
δ
= 30.92.
3
1
13
[
In the H and C spectra signals of protons and carbon atoms directly attached to the boron
2
3
atom (B-С H, B-C H (cycle)) were not detected].
2
4
.3.1.9. Spectral date for 1-(bicyclo[2.2.1]hept-2-yloxy)-2-octylborirane 17b. Yellow oil liquid,
1
bp 120 ºC (1 mm). Yield: 72% 1.89 g, 7.2 mmol). H NMR (CDCl , in ppm, 400.13 MHz):
δ =
3
1
3
0
.80‒0.95 (m, 3Н, СН ), 1.00‒1.80 (m, 24H, 2CH, 11CH ), 4.02 (m, 1H, 2CH‒O). С NMR
3
2
(
CDCl , in ppm, 100.62 MHz):
δ
= 14.08 (alkyl), 22.65 (alkyl), 24.27, 28.40, [29.21, 29.62 (4C,
3
11
alkyl)], 31.83 (alkyl), 32.60 (alkyl), 34.80, 35.37, 42.20, 43.74, 74.95. B NMR (CDCl , in ppm,
3
1
13
1
28.33 MHz): δ = 30.91. [In the H and C spectra signals of protons and carbon atoms directly
2
3
attached to the boron atom (B-С H, B-C H (cycle)) were not detected].
2
Acknowledgement
This work was financially supported by Russian Science Foundation (project No. 17-73-
1
0124). The structural studies of compounds were performed with the use of unique equipment
in "Agidel" Collective Usage Centre at the Institute of Petrochemistry and Catalysis of RAS .
References

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ACCEPTED MANUSCRIPT
Highlights
•
•
•
Cp TiCl catalyzes cycloboration of α-olefins with RBCl
2 2 2
Alkyl, arylalryl, cycloalkyldichloroboranes act as transmetallating agents
Disubstituted boriranes are the final products