An original one-pot approach to boronic esters using the titanium-catalyzed reaction of cyclic olefins with alkyldichloroboranes

Article abstract of DOI:10.1016/j.jorganchem.2018.07.019

Boronic esters (dicycloheptylalkylboronates, dicyclooctylalkylboronates, dicyclododecylalkylboronates, dibicyclo[2.2.1]hept-2-ylalkylboronates) are produced with yields ranging from moderate to excellent (52–96%) by the reaction between cyclic olefins (cycloheptene, cis-cyclooctene, cis/trans-cyclododecene, norbornene) and alkyldichloroboranes (alkyl = Et, n-Pent) in the presence of metallic magnesium and the Cp₂TiCl₂ catalyst with subsequent addition of water.

Full text of DOI:10.1016/j.jorganchem.2018.07.019

Journal of Organometallic Chemistry 872 (2018) 8e11
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Communication
An original one-pot approach to boronic esters using the titanium-
catalyzed reaction of cyclic olefins with alkyldichloroboranes
*
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
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 April 2018
Received in revised form
Boronic esters (dicycloheptylalkylboronates, dicyclooctylalkylboronates, dicyclododecylalkylboronates,
dibicyclo[2.2.1]hept-2-ylalkylboronates) are produced with yields ranging from moderate to excellent
(
52e96%) by the reaction between cyclic olefins (cycloheptene, cis-cyclooctene, cis/trans-cyclododecene,
22 June 2018
norbornene) and alkyldichloroboranes (alkyl ¼ Et, n-Pent) in the presence of metallic magnesium and
Accepted 16 July 2018
Available online 17 July 2018
the Cp
2
TiCl
2
catalyst with subsequent addition of water.
©
2018 Elsevier B.V. All rights reserved.
Keywords:
Boronic ester
Cyclic olefins
Norbornene
Alkyldichloroborane
Catalysis
1. Introduction
2. Results and discussion
Recently we have carried out direct cycloboration of
with the boron halogenides in the presence of Mg and Cp
a
-olefins
In continuation of our research into the catalytic cycloboration
of unsaturated compounds, we have performed the reaction be-
tween cyclic olefins (cyclohexene, cycloheptene, cis-cyclooctene,
cyclododecene (cis/trans ¼ 3:1), norbornene) and alkyldi-
chloroboranes (alkyl ¼ Et, n-Pent) in the presence of magnesium
2
TiCl
2
catalyst to afford appropriate 1,2-substituted boriranes [1]. In order
to widen the application scope of this reaction, we have performed
the cycloboration involving cyclic olefins. It was quite unexpected
for us to isolate the boronic esters as products of this reaction
after water treatment. Boronic esters are highly valuable com-
pounds, which have found extensive applications in organic and
medicinal chemistry [2]. Moreover, they are an attractive class of
synthetic intermediates, because of their unique properties as mild
organic Lewis acids, together with their stability and easy of
handling [3].
2 2
metal (a chlorine ion acceptor) and Cp TiCl catalyst under opti-
mized reaction conditions (olefin: [B]: [Mg]: [Ti] ¼ 1: 2: 2: 0.2, THF,
ꢀ
ꢀ
50 C for 5 h, then ~ 22e25 C for 16 h) (Scheme 1).
We have expected that these cycloboration reactions represent
the direct pathway to annelated boriranes 1 and 2 (Fig. 1). However,
it was not possible to isolate these compounds.
13
Thus, in C NMR spectra of samples taken from the reaction
masses after completion of the reactions with the participation of
In this paper, we report on boronic esters produced by the
interaction between cyclic olefins (cycloheptene, cis-cyclooctene,
cis/trans-cyclododecene, norbornene) and alkyldichloroboranes
2
EtBCl and cyclic olefins, instead of signals expected for symmetric
annelated structures 1 and 2 (Fig. 1), much more signals are
observed, which suggests the formation of a mixture of products.
The presence of the broadened signals in the 69e75 ppm region
indicates the incorporation of the oxygen atom through the B-C
bond of the resulting boron-containing compounds.
(
alkyl ¼ Et, n-Pent) under Cp
2 2
TiCl catalysis with subsequent
addition of water.
Probably, the organoboron products of the reaction are
extremely sensitive to trace amounts of oxygen and moisture. We
have assumed that the addition of excess water to the reaction mass
would facilitate the complete conversion of the resulting
*
Corresponding author.
E-mail address: khafizovaleila@gmail.com (L.O. Khafizova).
https://doi.org/10.1016/j.jorganchem.2018.07.019
022-328X/© 2018 Elsevier B.V. All rights reserved.
0

L.I. Khusainova et al. / Journal of Organometallic Chemistry 872 (2018) 8e11
9
Scheme 1. Cp
2
2
TiCl -catalyzed reaction of cyclic olefins with RBCl
2
(R ¼ Et, n-Pent) after addition of water.
Fig. 1. Proposed structures of boriranes from the Ti-catalyzed cycloboration reaction
between cyclic olefins and RBCl
2
.
organoboron products to oxygen-containing organoboron prod-
ucts. Indeed, the NMR spectra of the reaction masses after the
treatment with water have become much simpler (See SI, page 2, 3
and 5, 6). This allowed us to identify the formation of a mixture of
boronic esters 3a,b and 4a,b, 5a,b and 6a,b, 7a and 8a (Scheme 1).
Scheme 2. Precursors for derivatives of boronic acids 3a,b, 5a,b, 7a and 9a,b.
11
In B NMR spectra of the reaction mass after water treatment the
signal of the boron atom was observed at ~31 ppm.
2
The Ti-catalyzed reaction between cyclic olefins and EtBCl has
certain limitations associated with the ring size of cyclic olefins.
Thus, we could not involve cyclohexene in the above reaction. 2-
Ethyl-1,2-oxaborinane (Fig. 2) was identified as the major product
formed in this reaction as the result of the interaction between
Scheme 3. Probable route for the formation of boronates 6a,b from compounds 5a,b.
2
EtBCl and THF. Reactions of boranes with tetrahydrofuran are well
known in the literature [4].
intensities of the signals attributed to alkyl (Et, n-Pent) and cyclo-
1
Obviously, the precursors for derivatives of boronic acids 3a,b,
heptyl(cyclooctyl, cyclododecyl) or norbornyl fragments in
H
5
1
2
a,b, 7a, and 9a,b are chloro(cycloalkyl)alkylboranes 11a,b, 12a,b,
3a and bicyclo[2.2.1]hept-2-yl(chloro)alkylboranes 14a,b (Scheme
). These organoboron compounds undergo autoxidation [5] and
NMR spectra of compounds 4a,b, 6a,b, 8a and 10a,b. It should be
13
noted that in the C NMR spectra of dibicyclo[2.2.1]hept-2-
ylalkylboronates 10a,b, diastereomeric splitting of a number of
signals is observed due to the interaction between two asymmetric
centers in the boronate molecule (See SI, pages 9e10).
hydrolysis [6], thus converting to cycloheptyl(cyclooctyl, cyclo-
dodecyl) hydrogen alkylboronates 3a,b, 5a,b, 7a and bicyclo[2.2.1]
hept-2-yl hydrogen alkylboronates 9a,b, respectively.
Boronates 4a,b, 6a,b, 8a and 10a,b can be consider as the
products from the condensation of compounds 3a,b, 5a,b, 7a and
Apparently, annelated boriranes, 1 and 2 were not produced in
the Cp TiCl -catalyzed reactions of cyclic olefins with RBCl . The
2
2
2
absence of the expected diols and the formation of exclusively
9
a,b. A probable route for the formation of boronates is shown in
monools 15e19 after oxidation of the reaction mixtures with H O /
2
2
Scheme 3 on the example of transformation of compounds 5a,b to
dicyclooctylalkylboronates 6a,b.
NaOH additionally evidence for this fact and findings (Scheme 4).
The previously proposed mechanism for the Ti-catalyzed
After vacuum distillation of the reaction mixtures, boronic es-
ters 4a,b, 6a,b and 10a,b were obtained with high yields (86e96%).
The smallest yield of boronic ester 8a (52%) was observed in the Ti-
cycloboration of a-olefins with boron chlorides with the partici-
pation of titanacyclopropane intermediates [1d], does not explain
the formation of esters as well as the formation of monoalcohols
after oxidation.
Theoretically calculations of thermodynamic and activation
parameters for the transmetallation of titanium cyclopropane in-
termediate as the key step of the model reaction between cyclo-
catalyzed reaction between cyclododecene and EtBCl
a, in this reaction, 2-ethyl-1,2-oxaborinane is formed (Fig. 2).
The presence of two cycloheptyl(cyclooctyl, cyclododecyl) or
norbornyl moieties is confirmed by the ratio of the integral
2
. Along with
8
hexene and EtBCl
2
in the presence of metallic magnesium and
Cp TiCl catalyst have demonstrated high activation barriers and
2
2
the thermodynamic unfavorability of this process (see SI p. 11).
Apparently, other catalytically active Ti-containing species
participate in the reaction between alkyldichloroboranes and cyclic
olefins. We can assume that titanium hydride complexes are the
key intermediates in this reaction, leading to precursors 11a,b,
2
Fig. 2. 2-Ethyl-1,2-oxaborinane, the product of the reaction between EtBCl and THF.

10
L.I. Khusainova et al. / Journal of Organometallic Chemistry 872 (2018) 8e11
Scheme 4. Cp
2
TiCl
2
-catalyzed reaction of cyclic olefins (cycloheptene, cis-cyclooctene, cis/trans-cyclododecene, norbornene) with RBCl
2
2 2
(R ¼ Et, n-Pent) after addition H O /NaOH.
12a,b, 13a and 14a,b, from which boronic esters are formed after
4.1. Synthesis of dicycloheptylethylboronate (4a),
oxidation and hydrolysis. Probably, intermediate titanium hydride
complexes are the result of the reaction between the titanocene
dicycloheptylpentylboronate (4b), dicyclooctylethylboronate (6a),
dicyclooctylpentylboronate (6b), dicyclododecylethylboronate (8a),
dibicyclo[2.2.1]hept-2-ylethylboronate (10a), dibicyclo[2.2.1]hept-
2-ylpentylboronate (10b)
2
"Cp Ti", formed under the reaction conditions in the presence of
metallic magnesium, and tetrahydrofuran [7]. To gain a deeper
understanding of the nature of the active species involved in this
catalytic reaction, further investigations are needed to perform.
4.1.1. General procedure
ꢀ
A glass reactor (50 mL), under a dry argon atmosphere at 0 С,
was charged under stirring with Cp
nesium (powder) (20 mmol, 0.486 g), THF (30 mL), the corre-
sponding cyclic olefin (10 mmol) and EtBCl (or n-PentBCl
12 mmol). EtBCl was synthesized according to the methods as
described in Ref. [11]. n-PentBCl was synthesized according to the
2 2
TiCl (2 mmol, 0.498 g), mag-
3
. Conclusion
2
2
)
In summary, we have elaborated the original one-pot
(
2
method for producing boronic esters, namely dicyclohepty-
lalkylboronates, dicyclooctylalkylboronates, and dibicyclo[2.2.1]
hept-2-ylalkylboronates, with yields from good to excellent
2
method as described in Ref. [12]. The temperature was raised to
ꢀ
5
0 С and the mixture was stirred 5 h. Then reaction mixture was
(
86e96%) via the reaction of cyclic olefins such as cycloheptene, cis-
cyclooctene and norbornene with RBCl
(R ¼ Et, n-Pent) in the
presence of the Cp TiCl catalyst with subsequent addition of water.
The Ti-catalyzed reaction between cyclic olefins and RBCl has
ꢀ
cooled to room temperature (~22e25 C) and was stirred for
additional 16 h. Then to a reaction mixture water (2 mL) was added
and the mixture was stirred for 3 h. The organic layer was sepa-
rated, the aqueous layer was extracted with diethyl ether
2
2
2
2
certain limitations associated with the ring size of cyclic olefins.
Yields of dicyclododecylalkylboronates derived from dodecene did
not exceed 52%. Cyclic olefins with small rings (e.g. cyclohexene) do
not give boronic esters at all.
(
2 ꢁ 10 mL), extracts were combined with the organic phase. The
solvent was evaporated and the residue was distilled under
reduced pressure.
4
.1.1.1. Spectral date for dicycloheptylethylboronate 4a. Yellow oil
ꢀ
4
. Experimental section
liquid, bp 150 C (5 mm). Yield: 94% (1.25 g, 4.7 mmol). IR spectrum,
ꢂ1
n, cm : 2927, 2858, 2687, 1655, 1608, 1461, 1336, 1221, 1172, 1108,
1
All reactions were carried out using standard Schlenk tech-
1025, 913, 834, 821, 762. H NMR (CDCl
-CH
3
, in ppm, 400.13 MHz):
-CH
niques. Commercially available cyclic olefins (cycloheptene, nor-
bornylene, cis-cyclooctene, cis/trans-cyclododecene), BCl (1 M
solution in hexane), Et B and Cp TiCl (Acros Organics, Aldrich)
were used. THF employed were pre-dried over KOH, refluxed over
sodium-wire for 2 h and distilled from LiAlH in a stream of argon.
d
¼ 0.72 (q, 2H, B-CH
2
3
, J ¼ 7.9 Hz), 0.93 (t, 3Н, B-CH
2
3
,
J ¼ 7.6 Hz), 1.35e1.45 (m, 4Н, cycloheptyl), 1.52e1.73 (m, 16Н,
3
cycloheptyl), 1.75e1.85 (m, 4Н, cycloheptyl), 4.22e4.28 (m, 2H,
3
2
2
13
2CH‒O). С NMR (CDCl
CH ), 8.27 (B-CH -CH ), 22.83, 28.18, 36.67, 72.67. B NMR (CDCl
in ppm, 128.33 MHz):
3
, in ppm, 100.62 MHz):
d
¼ 5.77 (br* B-CH
2
-
1
1
3
,
4
3
2
3
Reactions with organometallic compounds were performed in a dry
argon flow.
d
¼ 30.65.
The H, 13C, 11B and 2D homo- (COSY) and heteronuclear (HSQC,
1
4.1.1.2. Spectral
date
for
dicycloheptylpentylboronate
4b.
ꢀ
HMBC) NMR spectra were measured in CDCl
00 spectrometer [400.13 ( H), 100.62 ( C), 128.33 ( B) MHz].
Chemical shifts ( ) are given in ppm relative to TMS, and the
coupling constants (J) in Hz. H and C NMR shifts were referenced
to internal solvent resonances and reported in parts per million
ppm) relative to Me
external standard of BF
compounds, signals of carbon atoms bonded to boron atoms, occur
as broadened ones, obviously, due to quadrupole broadening effect
of the boron nuclei [8].
3
on a Bruker Avance-
Yellow oil liquid, bp 152 C (1 mm). Yield: 90% (1.39 g, 4.5 mmol). IR
1
13
11
ꢂ1
4
spectrum,
n
, cm : 2911, 2830, 2718, 1428, 1380, 1300, 1210, 1195,
1
d
1170, 1107, 1005, 955, 830, 797, 720, 685. H NMR (CDCl
400.13 MHz): , J ¼ 7.8 Hz), 0.90 (t, 3Н, CH
¼ 0.71 (t, 2H, B‒CH
J ¼ 6.9 Hz), 1.23e1.42 (m, 6Н, 3CH , alkyl), 1.42e1.52 (m, 4Н, 4CH,
cycloheptyl), 1.55e1.84 (m, 20Н, 12CH, 4CH cycloheptyl),
, in ppm, 100.62 MHz):
, alkyl), 14.18 (alkyl), 22.64 (alkyl), 23.05
(cycloheptyl), 24.20 (alkyl), 28.27 (cycloheptyl), 34.97 (alkyl), 36.73
3
, in ppm,
1
13
d
2
3
,
2
1
1
(
4
Si. B NMR spectra were referenced to an
2
,
13
13
$Et
2
O. In the C NMR spectra of boron
4.20e4.30 (m, 2H, 2CH‒O). С NMR (CDCl
¼ 13.90 (br*, B‒CH
3
3
d
2
11
(cycloheptyl), 72.65 (O‒CH). B NMR (CDCl
3
, in ppm, 128.33 MHz):
The treatment of the reaction mixture with H
2
O
2
was done
d
¼ 31.99.
under alkaline conditions as described in Refs. [1,9]. Spectral and
physical characteristics of compounds 15e17, 18b, 19 have been
reported Refs. [10].
4.1.1.3. Spectral date for dicyclooctylethylboronate 6a. Yellow oil
liquid, bp 160 C (5 mm). Yield: 96% (1.41 g, 4.8 mmol). IR spectrum,
ꢀ

L.I. Khusainova et al. / Journal of Organometallic Chemistry 872 (2018) 8e11
11
ꢂ1
1H NMR (CDCl
CH ), 1.04e1.21 (m, 22H, 5CH
3.70e3.85 (m, 2H, 2CH‒O). С NMR (CDCl
¼ 14.03 (alkyl), 15.89 (br*, B‒CH , alkyl), 22.42 (22.52) (alkyl),
23.72 (23.83) (alkyl), 24.28, 28.36, 34.78, 34.83 (alkyl), 35.35, 42.25
n
1
, cm : 2923, 2854, 2695, 1712, 1466, 1447, 1390, 1342, 1311, 1263,
3
, in ppm, 400.13 MHz):
, 12CH), 2.05e2.25 (m, 4Н, 4CH),
, in ppm, 100.62 MHz):
d
¼ 0.65e1.00 (m, 5Н, B‒CH
2
,
1
216, 1181, 1117, 1053, 991, 908, 845, 805, 762, 736, 706, 677, 648. H
NMR (CDCl , in ppm, 400.13 MHz): -CH
¼ 0.72 (q, 2H, B-CH
J ¼ 7.6 Hz), 0.93 (t, 3Н, B-CH -CH , J ¼ 7.8 Hz), 1.45e1.60 (m, 16Н,
cyclooctyl), 1.60e1.80 (m, 12Н, cyclooctyl), 4.22e4.27 (m, 2H, 2CH‒
3
2
13
3
d
2
3
,
3
2
3
d
2
1
3
11
O). С NMR (CDCl
CH ), 8.27 (B-CH -CH
CDCl , in ppm, 128.33 MHz):
3
, in ppm, 100.62 MHz):
), 22.81, 25.38, 27.41, 34.15, 72.23. B NMR
¼ 30.76.
d
¼ 5.92 (br*, B-CH
2
-
(42.32), 43.73 (43.77), 75.24 (75.30). B NMR (CDCl
128.33 MHz):
¼ 30.96.
3
, in ppm,
11
3
2
3
d
(
3
d
Acknowledgement
4
.1.1.4. Spectral date for dicyclooctylpentylboronate 6b. Yellow oil
ꢀ
liquid, bp 171 C (1 mm). Yield: 92% (1.55 g, 4.6 mmol). IR spectrum,
ꢂ1
This work was financially supported by Russian Science Foun-
dation (project No. 17-73-10124). The structural studies of com-
pounds were performed with the use of unique equipment in
n
, cm : 2902, 2838, 2704, 1455, 1400, 1385, 1312, 1260, 1205, 1171,
1
1
4
125, 998, 975, 831, 800, 766, 727, 680, 650. H NMR (CDCl
00.13 MHz): , J ¼ 7.8 Hz), 0.89 (t, 3Н, CH
¼ 0.70 (t, 2H, B‒CH
, alkyl), 1.42e1.62 (m, 16Н, 4CH,
, cyclooctyl), 1.65e1.78 (m, 12Н, 4CH, 4CH , cyclooctyl),
, in ppm, 100.62 MHz):
, alkyl), 14.09 (alkyl), 22.58 (alkyl), 22.80
3
, in ppm,
d
2
3
,
"Agidel" Collective Usage Centre at the Institute of Petrochemistry
J ¼ 6.8 Hz), 1.24e1.42 (m, 6Н, 3CH
2
and Catalysis of RAS.
6
4
d
CH
.17e4.32 (m, 2H, 2CH‒O). С NMR (CDCl
¼ 13.50 (br*, B‒CH
2
2
13
3
2
Appendix A. Supplementary data
(
cyclooctyl), 24.16 (alkyl), 25.39 (cyclooctyl), 27.43 (cyclooctyl),
11
3
4.13 (cyclooctyl), 34.90 (alkyl), 72.23 (O‒CH). B NMR (CDCl
¼ 31.36.
In the 13C NMR spectra of boron compounds, signals of carbon
3
, in
Supplementary data related to this article can be found at
https://doi.org/10.1016/j.jorganchem.2018.07.019.
ppm, 128.33 MHz):
d
*
atoms bonded to boron atoms, occur as broadened ones, obviously,
due to quadrupole broadening effect of the boron nuclei [8].
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4
.1.1.5. Spectral
date
for
dicyclododecylethylboronate
8a.
ꢀ
b) L.I. Khusainova, L.O. Khafizova, T.V. Tyumkina, U.M. Dzhemilev, Russ. J. Gen.
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Yellow oil liquid, bp 178 C (0.1 mm). Yield: 52% (1.06 g, 2.6 mmol).
IR spectrum,
ꢂ1
n, cm : 2927, 2863, 1694, 1577, 1543, 1482, 1415, 1333,
1
1
222, 1076, 1049, 906, 797, 763, 717, 600. H NMR (CDCl
00.13 MHz): -CH , J ¼ 6.7 Hz), 0.92 (t, 3Н, B-
¼ 0.75 (q, 2H, B-CH
CH -CH
, J ¼ 8.0 Hz), 1.25e1.50 (m, 28Н, cyclododecyl), 1.51e1.75
m, 16Н, cyclododecyl), 3.97e4.08 (m, 2H, 2CH‒O). С NMR (CDCl
in ppm, 100.62 MHz): -CH ), 7.90 (B-CH -CH
0.91, 23.22, 23.40, 23.76, 24.16, 32.38, 69.38. B NMR (CDCl , in
3
, in ppm,
4
d
2
3
2
3
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13
(
3
,
3
),
d
¼ 5.34 (br*, B-CH
2
3
2
11
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3
ppm, 128.33 MHz):
d
¼ 30.64.
[
[
3] a) N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457;
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4.1.1.6. Spectral date for dibicyclo[2.2.1]hept-2-ylethylboronate 10a.
ꢀ
Yellow oil liquid, bp 140 C (5 mm). Yield: 90% (1.18 g, 4.5 mmol). IR
spectrum,
ꢂ1
n, cm : 2916, 2900, 2859, 2831, 2189, 1470, 1430, 1388,
[5] M.M. Midland, H.C. Brown, J. Am. Chem. Soc. 95 (1973) 4069.
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1335, 1263, 1233, 1201, 1150, 1113, 1063, 980, 855, 790, 760, 726,
1
6
95, 670. H NMR (CDCl
CH
, J ¼ 8.1 Hz), 0.87e0.95 (m, 3Н, B-CH
CH), 1.25e1.52 (m, 8H, 4CH, 2CH ), 1.57e1.67 (m, 4H, 4CH), 2.12
br.s, 2H, 2CH), 2.23 (br.s, 2H, 2CH), 3.85e4.15 (m, 2H, 2CH‒O).
NMR (CDCl , in ppm, 100.62 MHz): ), 7.94 (8.00)
¼ 5.43 (br*, B‒CH
B-CH -CH ), 24.33, 28.41, 34.78, 35.38, 42.23 (42.30), 43.70 (43.75),
5.25. B NMR (CDCl , in ppm, 128.33 MHz):
¼ 30.94.
3
, in ppm, 400.13 MHz):
d
¼ 0.73 (q, 2Н, B‒
[
2
2
-CH ), 1.00e1.12 (m, 4Н,
3
4
(
2
[8] B. Wrackmeyer, Annu. Rep. NMR Spectrosc. 20 (1988) 61.
[9] H.C. Brown, M. Zaidlewicz, J. Am. Chem. Soc. 98 (1976) 4917.
10] a) R.D. Rieke, R.M. Wehmeyer, T.-Ch Wu, G.W. Ebert, Tetrahedron 45 (1989)
13
С
[
3
d
2
443;
(
7
2
3
b) L. Pehlivan, E. Metay, O. Boyron, P. Demonchaux, G. Mignani, M. Lemaire,
Eur. J. Org Chem. 24 (2011) 4687;
c) G.C. Levy, R.A. Komoroski, R.E. Echols, Org. Magn. Reson. 7 (1975) 172;
d) I.C. Jones, G.J. Sharman, J. Pidgeon, Magn. Reson. Chem. 43 (2005) 497;
e) S.K. Upadhyay, Sh Hoz, J. Org. Chem. 76 (2011) 1355.
1
1
3
d
4.1.1.7. Spectral date for dibicyclo[2.2.1]hept-2-ylpentylboronate 10b.
ꢀ
[11] a) H.C. Brown, D. Basavaiah, N.G. Bhat, Organometallics 2 (1983) 1309;
b) H.C. Brown, A.B. Levy, J. Organomet. Chem. 44 (1972) 233;
Yellow oil liquid, bp 145 C (1 mm). Yield: 86% (1.31 g, 4.3 mmol). IR
spectrum,
ꢂ1
n, cm : 2910, 2850, 2828, 2190, 1450, 1425, 1398, 1359,
c) R. K o€ ster, M.A. Grassberger, Liebigs Ann. Chem. 719 (1968) 1699.
1300, 1269, 1235, 1160, 1107, 1065, 970, 875, 795, 750, 699, 660, 637.
[12] H.C. Brown, N. Ravindran, S.U. Kulkarni, J. Org. Chem. 45 (1980) 384.