Zinc Hydride-Catalyzed Hydrofuntionalization of Ketones

Article abstract of DOI:10.1021/acs.joc.0c01285

Three new dimeric bis-guanidinate zinc(II) alkyl, halide, and hydride complexes [LZnEt]2 (1), [LZnI]2 (2) and [LZnH]2 (3) were prepared. Compound 3 was successfully employed for the hydrosilylation and hydroboration of a vast number of ketones. The catalytic performance of 3 in the hydroboration of acetophenone exhibits a turnover frequency, reaching up to 5800 h-1, outperforming that of reported zinc hydride catalysts. Notably, both intra- and intermolecular chemoselective hydrosilylation and hydroboration reactions have been investigated.

Full text of DOI:10.1021/acs.joc.0c01285

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Article
Zinc Hydride Catalyzed Hydrofuntionalization of Ketones
Rajata Kumar Sahoo, Mamata Mahato, Achintya Jana, and Sharanappa Nembenna
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c01285 • Publication Date (Web): 05 Aug 2020
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The Journal of Organic Chemistry
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Zinc Hydride Catalyzed Hydrofuntionalization of Ketones
Rajata Kumar Sahoo,a Mamata Mahato,a Achintya Jana,b and Sharanappa Nembenna*a
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aSchool of Chemical Sciences, National Institute of Science Education and Research (NISER), Homi Bhabha National
Institute (HBNI), Bhubaneswar- 752 050 India
bUndergraduate Programme, Indian Institute of Science, Bangalore, 560 012, India
ABSTRACT: Three new dimeric bis-guanidinate zinc(II) alkyl, halide, hydride complexes [LZnEt]2 (1), [LZnI]2 (2) and [LZnH]2
(3) were prepared. Compound 3 was successfully employed for the hydrosilylation and hydroboration of a vast number of ketones.
The catalytic performance of 3 in the hydroboration of acetophenone exhibits turn over frequency, reaching up to 5800 h-1,
outperforming that of reported zinc hydride catalysts. Notably, both intra- and intermolecular chemoselective hydrosilylation and
hydroboration reactions have been investigated.
INTRODUCTION
The catalytic hydrofunctionalization of ketones with silanes
2+
or HBpin is undoubtedly a practical methodology for the
synthesis of silyl ethers or borate esters, which are
extensively utilized as intermediates for the synthesis of
alcohols.1 The design of inexpensive and sustainable
homogenous metal catalysts, particularly, metal hydrides,
is very desirable. In this context, earth-abundant,
environmentally friendly, cheaper, biocompatible zinc2
element fits the bill entirely.
N
N
Dipp
Zn
Mes
THF
Mes
N
H
S
N
N
Zn
H
N
Zn2+
S
Py
H
H
S
Dipp
H
H
Mes
Mes
N
Zn
Zn
B
N
A
N
N
Mes
Mes
C
In 1947, Schlesinger reported the synthesis of zinc
dihydride.3 To date, several synthetic routes are available
for the preparation of zinc dihydride4 (ZnH2)∞, it is a white
solid, for which the exact structure is not clear. Moreover,
it is thermally unstable and poorly soluble in organic
solvents. This provoked many synthetic chemists to prepare
neutral heteroleptic zinc hydrides.5 Such zinc hydrides are
not only important reducing agents, but they can also be
model compounds for enzyme mimicking, as precursors in
material science and catalysts for various organic
transformations.6
Dipp
H
t-Bu
N
THF
Zn
Ph
Ph
N
N
OTf
N
N
Zn
Ph
Ph
SiMe3
Dipp
S
S
t-Bu
N
N
Zn
N
N
H
S
t-Bu
E
H
D
F
+
H
H
N
Ar
Ar
Ar
N
Ar
N
Ar
Ar
H
N
N
N
N
Me2
Zn
Zn
N
N
N
Zn
As far as zinc catalyzed hydrofunctionalization of
carbonyls is concerned, there are reports on zinc-catalyzed
hydrosilylation of carbonyls.7 Mainly, groups of Parkin,8
Nikonov,9 Okuda,10 Rivard,11 Jones,12 Mösch-Zanetti,13 and
Venugopal14 independently reported zinc hydride catalyzed
hydrosilylation of ketones (Figure 1. A-G). Surprisingly,
examples of zinc catalyzed hydroboration of ketones are
scarce.15 To our knowledge, there are only two examples on
the hydroboration of ketones catalyzed by molecular zinc-
hydrides (Figure 1.D-E).11-12 It should be noted that no zinc
N
e2
N
Me2
M
N
H
H
N
Ar
Ar
H
H
G
Ar = 2,6-Et2-C6H3
Mes = 2,4, 6-Me3-C6H2
Dipp = 2,6-iPr2-C6H3
Present Work
Both Hydroboration
and Hydrosilylation
Figure 1. Previously reported selected zinc hydride catalysts for
hydrosilylation (A-G) and hydroboration (D-E) of ketones and
present work.
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catalysts are available in the literature, which performs for
The 1H NMR spectrum of 1 shows one quartet at -0.08 ppm
1
2
3
4
5
6
7
8
both hydrosilylation and hydroboration of many ketones
(Bifunctional), except D and E, which are limited to only
one substrate. However, very recently, the Baker group
reported a copper-based catalyst for hydroboration and
hydrosilylation of carbonyls.16
and one triplet at 0.60 ppm in CDCl3, corresponding to four
and six protons for ZnCH2CH3 and ZnCH2CH3,
respectively. And also, a singlet peak at 5.01 equivalent to
four protons of the side-arm ArNH parts of the ligand. The
13C{1H} NMR show typical ZnCH2CH3 and ZnCH2CH3
resonances at -2.3 and 11.5 ppm, respectively. Complete
disappearance of ZnCH2CH3 and ZnCH2CH3 proton
Recently our group reported inexpensive and sustainable
aluminum-based catalysts bearing conjugated bis-
guanidinate (CBG) anions for the hydroboration of
carbonyl compounds and other challenging unsaturated
organic substrates.17 A few examples of biguanides or
CBGs supported zinc complexes are known in the
literature.18 However, a -diketiminate analogue, i.e., CBG
supported zinc hydride, is not known in the literature.
1
resonances in H NMR and ZnCH2CH3 carbon resonances
in 13C{1H} NMR in C6D6, which indicated the formation of
compound [LZnI]2 (2). The 1H NMR spectrum of 3 in C6D6
displays the Zn-H hydride resonance at 4.52 ppm (4.50
ppm in d8-toluene), a good agreement with the bridged
four-coordinate heteroleptic zinc hydride complexes
reported in the literature (4.57 – 4.59 ppm).5e The 13C{1H}
NMR spectra of compounds 1-3 display a unique resonance
for the N3C carbon atom at 156.6, 157.5, and 157.2 ppm,
respectively. The crystals of 2 suitable for single-crystal X-
ray diffraction analysis were crystallized from toluene
solution at -5 oC. The compound 2 crystallizes in the
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Thus, herein we report the synthesis of three new examples
of molecular CBG zinc alkyl, halide, and hydride
complexes. Further, zinc hydride catalyzed hydrosilylation,
and hydroboration of a broad range of ketones has been
investigated. Moreover, we designed a new, sustainable,
and easily accessible catalyst containing only C, H, N, and
Zn elements. We are employing the very lowest catalyst
loading (0.05 %) for the hydroboration of acetophenone.
1
triclinic system with the P space group. The molecular
structure of compound 2 is depicted in figure 2. The solid-
state structure of 2 shows that each zinc atom is
coordinated to two N atoms from the CBG ligand in N, N’
chelate fashion, and two bridged iodide moieties to form a
distorted tetrahedral geometry.
RESULTS AND DISCUSSION
A
new example of -diketiminate analogue, i.e.,
The Zn11 and Zn1’ bond distances in 2 are
2.5819(15) (Å) and 2.7702(16) (Å), which are comparable
to Zn bond distances of the analogous DippNacnacZn(-
I)2Li(OEt2)2 complex, [Zn–I(1) 2.6142(8) Å and Zn–I(2)
2.6648(8) Å].20 The NMN bite angle of the compound 2
is N1Zn1N4 95.7(3)o, which is acute when compared to
conjugated bis-guanidinate (CBG) stabilized dimeric zinc
hydride, can be accessed in three steps: i) Deprotonation of
a free CBG ligand: a treatment of LH [L = {(ArHN)(ArN)-
C=N-C=(NAr)(NHAr); Ar = 2,6-Et2-C6H3}] with ZnEt2 in
toluene afforded [LZnEt]2 (1) in 78 % yield. ii) Alkyl-
halide exchange: a reaction between compound 1 and two
equivalents of molecular iodine in toluene resulted in
[LZnI]2 (2) in 72 % yield. iii) Salt-metathesis reaction:
Compound 2 upon treatment with [KNH(iPr)BH3] in
toluene allowed the formation of [LZnH]2 (3) in 69 % yield
(Scheme 1).
the
bond
angle
in
DippNacnacZn(-I)2Li(OEt2)2
(N1Zn1N2 98.78(15)o).
Scheme 1. Synthesis of CBG Supported Zinc Complexes 1-
3.
N2
N1
I1
Zn1
H
H
Ar
Ar
Ar
Ar
N
Ar
Ar
N
N
Ar
Ar
N3
N
N
2 Zn
Et2 1 M in hexanes
80 oC, 48 h, toluene
-2 EtH
N
N
N
N
H
H
Zn
N4
N
N
Zn
N
N
2
N
N
Ar
Ar
N5
H
Ar
Ar
1 (78%)
LH
H
H
2I2
rt, 12 h,
touene
-2EtI
Figure 2. The solid-state structure of 2. H atoms are omitted for
clarity. Selected bond lengths (Å) and bond angles (o): Zn1N1
1.956(8), Zn1N4 1.943(8), Zn1I1 2.5819(15), Zn1I1’
2.7702(16), Zn1Zn1' 2.4819(19); N1Zn1N4 95.7(3),
N1Zn1I1 119.5(2), N4Zn1I1 112.2(2), I1Zn1I1’ 104.04
(5), Zn1I1Zn1' 75.59 (5).
H
H
H
H
H
H
H
Ar
Ar
2 KNH(iPr)BH3
rt, 3 h, toluene
Ar
N
Ar
N
Ar
Ar
Ar
Ar
N
Ar
N
N
Ar
Ar
I
I
N
N
N
H
N
N
N
Zn
N
N
Zn
Ar
N
N
Zn
N
N
Zn
-2 KI,
N
N
H
- "iPrN(H)BH2 oligomers"
Ar
Ar
N
Ar
Ar
H
2 (72%)
3 (69%)
X-ray diffraction studies confirm that compound 3 is in
dimeric form. However, despite several attempts, weakly
diffracting crystals led to relatively poor data collection.19
Further, a temperature-dependent NMR (d8-toluene, 298 -
358 K, Supporting Information Figures S143-S146) studies
have been performed to know the solution structure of
Ar = 2,6-Et2-C6H3
All three CBG Zn(II) complexes are air and moisture
sensitive and thermally stable. Compounds 1-3 were
characterized by 1H and 13C{1H} NMR and mass
spectrometric analyses. Moreover, the molecular structure
of CBG Zn(II) iodide (2) is established by single-crystal X-
ray diffraction studies19, which is dimeric.
compound 3. These experiments indicate that
a
temperature-variable dimer-monomer equilibrium exists.
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The dimeric µ-hydride, [LZnH]2 complex presents at 298
1
2
K, and the
Scheme 2. Substrate Scope for Compound 3 Catalyzed Hydrosilylation and Hydroboration of Ketonesa
3
4
5
6
H2O/ NaOH
MeOH, 60 oC, 6 h
HSiHPh2
3
cat. (0.3 mol%)
7
8
rt, 12 h, Neat
OH
9
O-SiHPh2 / Bpin
O
R
R'
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
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58
59
60
R
R'
R
R'
2o Alcoholb
4a 4y,
-
>99%
>99%
5a 5s,
7a-7s,
-
59-92%
65-94%
Silica gel/ MeOH
60 oC, 6 h
6a 6y,
-
HBpin
3
cat. (0.2 mol%)
rt, 6 h, Neat
R, R' = aliphatic/ aromatic
OH
OH
OH
OH
OH
MeO
5d
, 75%
7d
, 78%
5e
, 79%
7e
, 81%
5c
7c
, 81%
, 84%
5a
7a
, 92%
, 94%
5b
7b
, 86%
, 83%
OH
OH
OH
OH
OH
Cl
F
Br
Cl
5f
7f
, 72%
, 70%
5g
7g
5h
7h
5j
, 83%
7j
, 79%
, 79%
, 83%
, 76%
, 71%
5i
, 84%
7i
, 80%
OH
HO
OH
O
N
OH
MeO2C
NC
OH
5m
7m
, 74%
, 71%
5k
7k
5n
, 59%
7n
, 65%
5o
7o
, 77%
, 68%
, 68%
, 73%
5l
7l
, 65%
, 73%
OH
HO
O-SiHPh2 / Bpin
OH
OH
C11H23
H
H3CS
O
4t
, >99%
6t
, >99%
Ph
5r
7r
5s
, 73%
7s
, 82%
, 77%
, 72%
5p
7p
5q
7q
, 82%
, 88%
, 69%
, 75%
O-SiHPh2 / Bpin
O-SiHPh2 / Bpin
O-SiHPh2 / Bpin
NH2
O-SiHPh2 / Bpin
O-SiHPh2 / Bpin
O
O-SiHPh2 / Bpin
O2N
4xc
6xc
4y
6y
4v
6v
, >99%
, >99%
4u
6u
4w
6w
, >99%
, >99%
, >99%
, >99%
, 81%
, 86%
, >99%
, >99%
aReaction conditions for hydrosilylation and hydroboration: All reactions were carried out with ketones (1 mmol), diphenyl silane (1.1 mmol) or pinacolborane (1.1
mmol), 0.3 mol% and 0.2 mol % of 3 for hydrosilylation and hydroboration, respectively for all ketones, except 4t and 6t, 0.5 mol% of 3 and diphenylsilane (2.2
mmol) or pinacolborane (2.2 mmol) were used, at rt for 6 h for hydroboration and 12 h for hydrosilylation under N2; bIsolated yields were determined after column
chromatography; cNitromethane was used as an internal standard for the substrates 4x and 6x and reaction timings 8h and 1.5 h, respectively.
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equilibrium shifted towards a monomeric complex, LZnH alcohols (7a-7s) can be found in supporting information
1
2
3
4
5
6
7
8
at increasing temperatures (Supporting Information Figures
S143-S146). As a result, increasing the temperature from
298 K to 358 K results in a decrease of Zn-H chemical shift
from 4.50 ppm to 4.19 ppm shows a change in the
coordination geometry of the complex at increasing
(see Figures.S47-S134).
Further, a bulk scale hydroboration reaction was performed
to verify the practical applicability of this protocol.
Strikingly, a 10 mmol scale reaction of acetophenone under
standard reaction conditions forming a quantitative yield of
boronate ester, which upon hydrolysis yielded the alcohol
7a in 88 % (Scheme 3).
temperature. Hence,
a temperature-dependent dimer-
monomer equilibrium is controlled by the dinuclear species
at 298 K, while a monomeric species is at elevated
temperatures.21
Scheme 3. Bulk Scale Hydroboration of Acetophenone
9
Considering the fewer reports on highly efficient zinc
catalysts for hydroboration and hydrosilylation of ketones,
we aimed to explore CBG ZnH catalyzed
with HBpin
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60
OH
O
3
Cat. (0.2 mol%)
rt, 6 h, neat
hydrofunctionalization of ketones. We chose
a
+
HBpin
diphenylsilane, Ph2SiH2 as hydride source for
a
Silica gel/ MeOH
60 oC, 6 h
hydrosilylation, because this reagent is much ideal in terms
of cost for the small and medium scale industries.1a The
reaction of acetophenone and diphenylsilane with 5 mol %
11 mmol
(1.60 mL)
7a
1.08 g, 88%
10 mmol
(1.16 mL)
It is important to note that, substrate scope includes
excellent tolerance of amine, nitro, nitrile, ester,
heterocycle, alkene, and alkyne functionalities in both
catalyst
3
gave quantitative conversion to the
hydrosilylation product after 12 h at room temperature (see
table S1, entry 1 in Supporting Information). Lowering the
catalyst loadings to 3.0, 1.0, and 0.3 mol % gave
quantitative conversion at the same reaction conditions.
However, at a loading of 0.3 mol % catalyst, we observed a
93% yield of the product within 8 h. Thus, 1.0 mmol of
acetophenone and 1.1 mmol of Ph2SiH2 and 0.3 mol% of
catalyst loading at room temperature in the neat condition
are the optimized conditions for hydrosilylation reaction
(see Table S1 in Supporting Information). A vast range of
substrates has been investigated including electron-
donating (5b-5f, 5s), electron-withdrawing substituents
(5g-5l), seven-membered ring attached with phenyl ring
(5m), heterocycles (5n-5o), fused system (5p), substituted
benzophenone (5q) and long-chain aliphatic ketone (5r)
and some exotic ketones (4t-4y) (Scheme 2). It is worthy to
note that compound 3 is capable of catalyzing the insertion
of 2-acetyl pyridine into all two of the Si-H bonds of
Ph2SiH2 to afford 4n’, which upon hydrolysis yielded 5n.
hydrosilylation
and
hydroboration
reactions.
(Intramolecular chemoselectivity). It is no surprise that
substrate bearing the aldehyde functional group (4t or 6t)
was not tolerated in both hydrosilylation and hydroboration
under reaction conditions. Remarkably, hydroboration
proceeded more efficiently than hydrosilylation.
Scheme
4.
Competitive
Hydrosilylation
and
Hydroboration Reaction
OBPin
O
3
Cat.
(0.2 mol%)
Ph2SiH2
+
+
Ph2SiH2
HBpin
+
rt, 15 min, Neat
unreacted
6a
, >99%
Next, a one-pot reaction of acetophenone, with both
diphenylsilane and HBpin in the presence of catalyst 3 (0.2
mol %) under neat conditions at room temperature for 15
min, has been carried out, which showed the formation of
6a alone in quantitative yield (Scheme 4).
In each case, the hydrolysis of the silylated ethers resulted
in the formation of secondary alcohols with good to
Table 1. Hydroboration of Acetophenone Catalyzed by 3a
1
excellent yields (59-92%, 5a-5s). H and 13C{1H} NMR
spectra of silylated ethers (4a-4y) are provided in the
supporting information (see Figures. S11-S46 in
Supporting Information).
OBpin
O
3
Cat.
+
HBpin
Examine as to whether B-H bond activation could be
augmented to the catalyst 3; we investigated the
hydroboration reaction with the same ketone substrates.
The reaction of acetophenone and HBpin with 0.2 mol %
6a
entry
cat. (mol%)
time (h)
yield (%)
TON
TOF (h-1
)
catalyst
3
gave quantitative conversion to the
hydroboration product after 6 h at room temperature (see
Table S2 in Supporting Information).
1
2
3
4
5
6
7
0.2
0.2
6
1
>99
>99
>99
>99
>99
>99
97
500
500
83
500
With these optimized conditions in hand, we determined to
expand the same ketone substrates, which employed for the
hydrosilylation reaction. To our delight, in all instances, a
quantitative conversion of ketones into their corresponding
boronates esters (6a-6y) was observed. The good to the
excellent yield of alcohol was noticed upon the hydrolysis
of the boronated esters (65-94%, 7a-7s, Scheme 2). The 1H
and 13C{1H} NMR spectra for boronate esters (6a-6y) and
0.2
0.25
1
500
2000
1000
2666
4000
5800
0.1
1000
1333
2000
1940
0.075
0.05
0.05
0.5
0.5
0.334
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aReaction conditions: catalyst (x mol %, 100 μL from stock
13C NMR indicated the formation of [LZnOCHPh2], 3B,
and corresponding peaks for OCH appeared at 6.36 and
77.2 ppm in 1H and 13C{1H} NMR, respectively (see
Figures. S9-S10 in Supporting Information).
solution in toluene), acetophenone (1 mmol), HBpin (1.11 mmol)
at rt. Yields were determined by 1H NMR spectroscopy using
nitromethane as an internal standard. TON was calculated through
the dividing number of moles of the product by the number of
moles of catalyst used. TOF was determined to divide TON by
time of reaction.
1
2
3
4
5
6
7
8
9
We were curious to know the catalytic efficiency of
compound 3 for the hydroboration of acetophenone. Under
the optimized conditions, the reaction of HBpin and
acetophenone with catalyst loading 0.2 mol % provided
>99 % conversion within 6 h (TOF 83 h-1).
Scheme 6. Proposed Mechanism for the Zinc Catalyzed
Hydrosilylation and Hydroboration of Ketones
OH
H
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11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
R2
R1
We noticed the >99% conversion of acetophenone into
corresponding boronate ester at room temperature with a
turn-over number and frequency 1940 and 5800 h-1,
respectively (see Table 1, entry 5). To the best of our
knowledge, CBG Zn(II) hydride catalysts (3) exhibited the
highest catalytic activity as compared with molecular zinc
hydride catalysts reported in the literature for the ketone
hydroboration reaction (see Table S3).11-12
SiHPh2
H
Bpin
O
H
O-SiHPh2/Bpin
O
LZn
R2
R1
LZn
R2
R1
H
R2
R1
H
H
HSiHPh2
3C
3C'
H
B
p
in
LZn
O
R2
R1
R2
R1
LZn
O
H
3
3B
H
3B
We are further excited to investigate the catalytic efficiency
of 3 in the intermolecular chemoselectivity hydroboration
between ketone vs. ester or amide. Thus, when
acetophenone was mixed with benzyl benzoate and HBpin
under optimized conditions, a 98% yield of hydroboration
of ketone was noticed in the choice of ester. Likewise,
acetophenone provides the corresponding boronate ester in
a 95 % yield in preference to the
O
R2
R1
O
R2
R1
O
R1
R2
Zn
L
Zn
L
H
H
R1,R2 = aliphatic/ aromatic
3A
3A
CONCLUSION
In summary, the first examples of -diketiminate
analogues, i.e., CBG-supported zinc alkyl (1), halide (2),
and hydride (3) complexes have been reported. Moreover,
we have exemplified earth-abundant, cheaper, easily
accessible, [LZnH]2 (3) as an efficient catalyst for
hydrosilylation and hydroboration of many ketones under
mild conditions. It is noted that reported examples of zinc-
based catalysts for hydrosilylation, and hydroboration
reactions require high catalyst loading (5-10 mol%),
limited substrate scope, longer reaction times. This work
presents a remarkably active ketone reduction via the
insertion/heterolytic cleavage mechanistic pathway.
N,N’-dimethyl benzamide. Similarly, 2-tridecanone, N, N’-
dimethylacetamide, and HBpin were reacted together with
catalyst 3, which solely yielded 6a in quantitative yield in
preference to amide (Scheme 5).
Scheme 5. Intermolecular Chemoselective Reactions
O
O
OBpin
O
O
3
Cat.
(0.2 mol%)
O
O
a)
+
HBpin
+
+
rt, 6 h, Neat
37
38
39
40b)
41
42
6a
, 98%
unreacted
EXPERIMENTAL SECTION
3
O
Cat.
OBpin
O
All manipulations were performed under a nitrogen
atmosphere using standard glove box and Schlenk
techniques unless otherwise stated. The ligand LH (L =
{(ArNH)(ArN)–C=N–C=(NAr)(NHAr)}; Ar = 2,6-Et2-
C6H3) was synthesized by using a protocol developed in
our laboratory.22 Diethyl zinc solution, 1 M in hexanes, was
procured from Sigma Aldrich. Iodine granules were
purchased from Spectrochem. The hydride source
[KNH(iPr)BH3] was prepared as per the reported
procedure.5c The solvents used for the synthesis and NMR
experiments were dried, distilled, and degassed before use
by standard methods.23 The 1H, 13C{1H} NMR spectra were
recorded on 400 MHz Bruker AV spectrometer. The
(0.2 mol%)
N
N
+
+
HBpin
HBpin
+
+
+
rt, 1 h, Neat
unreacted
6a, 95%
3
Cat.
O
O
O
43
OBpin
(0.2 mol%)
c)
+
N
C11H23
N
C11H23
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
rt, 1 h, Neat
6r
, >99%
unreacted
In all three cases, only ketones were reduced in preferences
to other reducible functionalities.
We established the mechanism as earlier described by
others
for
the
metal
hydride
catalyzed
hydrofunctionalization reactions.1 Insertion of Zn-H moiety
into C=O functionality of ketone yielded the zinc alkoxide,
LZnOR (3B), via intermediate 3A. Next, a reaction of 3B
with HBpin or Ph2SiH2 affords silyl ether or boronate ester
via 3C or 3C' along with the restoration of the LZnH
catalyst (Scheme 6). Further to confirm the formation of
reactive intermediate 3B, a stoichiometric reaction of
LZnH with benzophenone has been carried out. The 1H and
1
chemical shifts (δ ppm) in H and 13C{1H} NMR spectra
were referenced to the deuterated solvents' residual proton
signals. The crystal data of compound 2 were collected on
a Rigaku Oxford diffractometer at 120 K. Selected data
collection parameters, and other crystallographic results are
summarized in Table S4. The structure was determined
using direct methods employed in ShelXT,24 OleX,25, and
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The Journal of Organic Chemistry
Page 6 of 13
refinement was carried out using least-square minimization
14.2. 1H NMR (400 MHz, d8-toluene) δ 7.05 (s, 12H), 6.83
implemented in ShelXL.26 All non-hydrogen atoms were
refined with anisotropic displacement parameters.
Hydrogen atom positions were fixed geometrically in
idealized positions and were refined using a riding model.
High-resolution mass spectra (HRMS) were recorded on a
Bruker micrOTOF-Q II spectrometer.
(t, JHH = 7.6 Hz, 4H), 6.58–6.56 (d, JHH = 7.6 Hz, 8H),
4.96 (s, 4H), 4.50 (s, 2H), 3.02–2.92 (m, 8H), 2.76–2.66
(m, 8H), 2.38–2.28 (m, 8H), 2.18–2.10 (m, 8H), 1.29 (t,
3JHH = 7.5 Hz, 24H), 0.93 (t, 3JHH = 7.6 Hz, 24H). 13C{1H}
NMR (100 MHz, d8-toluene) δ 157.6, 142.6, 141.4, 139.2,
135.4, 126.9, 126.7, 126.2, 125.6, 25.2, 24.6, 14.6, 14.5.
HRMS (ESI) m/z: [M/2 + H]+ Calcd for C42H55N5Zn
694.3822, Found: 694.3816.
3
3
1
2
3
4
5
6
7
8
Synthesis of [LZnEt]2 (1): A 1.5 g (2.38 mmol) of LH was
dissolved in ~20 mL of toluene. Next, a diethylzinc
solution (2.5 mL, 2.5 mmol, 1 M in hexanes) was added at
9
Synthesis of LZnOCHPh2 (3B): A solution of compound
3 (0.070 g, 0.05 mmol) in THF (~3 mL) was slowly added
to a solution of benzophenone (0.018 g, 0.1 mmol) in THF
(2 mL) at room temperature. The reaction mixture was
o
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
room temperature. It was then heated at 80 C in oil bath
for 2 days. The clear solution was filtered through a Celite.
The desired product 1 was isolated as colorless crystalline
compound after removing the entire solution in high
o
stirred at 65 C in oil bath for 12 h. Then volatiles were
o
1
vacuum. (1.340 g, yield 78%); Mp 178-182 C. H NMR
removed in vacuo. The residue was washed with n-hexane
o
3
(400 MHz, 25 C, CDCl3) δ 7.16–7.14 (d, JHH = 7.1 Hz,
and dried in high vacuum to obtain a colorless powder.
3
1
8H), 7.11–7.07 (m, 4H), 6.84 (t, JHH = 7.5 Hz, 4H), 6.63–
6.61 (d, JHH = 7.5 Hz, 8H), 5.01 (s, 4H), 2.93–2.85 (m,
(0.068 g, yield 77%). H NMR (400 MHz, CDCl3) δ 7.42–
3
3
3
7.40 (d, JHH = 7.3 Hz, 1H), 7.37 (t, JHH = 7.6 Hz, 2H),
8H,), 2.70–2.61 (m, 8H), 2.42–2.33 (m, 8H), 2.17–2.12 (m,
7.28 (s, 2H), 7.25–7.24 (m, 3H), 7.19–7.17 (m, 2H), 7.09
3
3
3
3
8H), 1.29 (t, JHH = 7.5 Hz, 24H), 0.92 (t, JHH = 7.5 Hz,
24H,), 0.60 (t, 3JHH = 8.0 Hz, 6H), –0.08 (q, 3JHH = 8.1 Hz,
4H). 13C{1H} NMR (100 MHz, CDCl3) δ 156.6, 143.0,
141.4, 138.9, 135.2, 126.3, 126.2, 125.3, 125.3, 24.9, 24.2,
14.4, 14.3, 11.5, -2.3. HRMS (ESI) m/z: [M/2 + H]+ Calcd
for C44H59N5Zn 722.4135; Found: 722.4094.
(t, JHH = 7.5 Hz, 2H), 6.99–6.97 (d, JHH = 7.3 Hz, 4H),
3
3
6.76 (t, JHH = 7.5 Hz, 2H), 6.54–6.52 (d, JHH = 7.5 Hz,
4H), 6.36 (s, 1H), 4.70 (s, 2H), 2.68–2.60 (m, 4H), 2.54–
2.47 (m, 4H), 2.33–2.26 (m, 4H), 2.13–2.05 (m, 4H), 1.14
3
3
(t, JHH = 7.5 Hz, 12H), 0.85 (t, JHH = 7.5 Hz, 12H).
13C{1H} NMR (100 MHz, CDCl3) δ 156.6, 141.0, 138.3,
135.5, 128.5, 128.2, 127.0, 126.5, 126.3, 125.6, 124.8,
124.6, 77.2, 24.6, 23.0, 14.2, 13.4. Note: Despite multiple
attempts, a satisfactory value for HRMS or CHNS was not
obtained.
Synthesis of [LZnI]2 (2): A 0.7 g (0.48 mmol) of
compound 1 dissolved in ~15 mL of dry toluene. Also,
0.25 g (0.99 mmol) of iodine was dissolved in ~10 mL of
dry toluene in another Schlenk tube. Then the solution of
iodine was added dropwise to the [LZnEt]2 (1) solution.
Immediately after the addition, a rose red could be
observed. The reaction mixture was stirred for 12 h, during
this period a pale yellow solution was observed. Then the
volatiles were evacuated, to the yellow powder a dry
toluene was added. The product 2 was crystallized in the
form of block shaped crystals suitable for X-ray diffraction
General Procedure for Hydrosilylation of Ketones.
Ketone (1.0 mmol), Ph2SiH2 (1.1 mmol), 4 mg (0.3 mol %)
of catalyst 3 were charged in an air-tight vial with a
magnetic bead inside the glove box. The reaction mixture
was allowed to stir at ambient temperature for 12 h. The
reaction's progress was checked by 1H NMR, which
indicated the completion of the reaction by the formation of
silyl ether by showing a new OCH resonance (4a-4y). The
reaction mixture was then charged with 2 mL of aqueous
15 M NaOH solution followed by 2 mL of methanol and
further heated in an oil bath at 60 oC for 6 h. Next,
combining organic layers followed by purification through
column chromatography using silica gel with ethyl acetate
and n-hexane yielded corresponding secondary alcohols.
o
o
at -5 C after 12 h. (0.573 g, yield 72%); Mp 238–242 C.
1H NMR (400 MHz, 25 C, C6D6) δ 7.10 (s, 12H), 6.87 (t,
o
3JHH = 7.5 Hz, 4H), 6.62–6.60 (d, JHH = 7.5 Hz, 8H), 5.08
3
(s, 4H), 3.08–3.04 (m, 8H), 2.74–2.69 (m, 8H), 2.36–2.28
3
(m, 8H), 2.18–2.12 (m, 8H), 1.32 (t, JHH = 7.4 Hz, 24H),
3
0.94 (t, JHH = 7.5 Hz, 24H). 13C{1H} NMR (100 MHz,
C6D6) δ 157.5, 141.0, 140.8, 138.8, 134.7, 126.6, 126.5,
126.4, 125.2, 24.8, 24.3, 14.3, 14.1. HRMS (ESI) m/z: [M/2
+ H]+ Calcd for C42H54IN5Zn 820.2788, Found: 820.2819.
Diphenyl(1-phenylethoxy)silane (4a)27. NMR yield:
1
(>99%). H NMR (400 MHz, CDCl3) δ 7.78–7.76 (d, J =
Synthesis of [LZnH]2 (3): A 0.85 g (0.52 mmol) of
compound 2 was dissolved in ~10 mL of dry toluene. Also,
0.121 g (1.08 mmol) of [KNH(iPr)BH3] was dissolved in
another Schlenk tube. Then, the solution of compound 2
was added to the [KNH(iPr)BH3] solution. The reaction
mixture was stirred for 3h. Then the mixture was filtered
through Celite and removed the solvent in vacuo to yield a
white crystalline solid. (0.501 g, yield 69%); Mp 229–233
oC. 1H NMR (400 MHz, C6D6) δ 7.10–7.08 (m, 12H), 6.90
6.5 Hz, 2H), 7.73–7.71 (d, J = 7.1 Hz, 2H), 7.54–7.43 (m,
10H), 7.38–7.36 (d, J = 8.0 Hz, 1H), 5.58 (s, 1H), 5.17 (q, J
= 6.3 Hz, 1H), 1.66–1.64 (d, J = 8.0 Hz, 3H). 13C{1H}
NMR (100 MHz, CDCl3) δ 145.3, 134.8, 134.7, 134.3,
134.1, 130.4, 130.3, 128.3, 128.1, 128.0, 127.2, 125.6,
72.8, 26.3.
Diphenyl(1-(o-tolyl)ethoxy)silane (4b)28. NMR yield:
1
(>99%). H NMR (400 MHz, CDCl3) δ 7.83–7.81 (d, J =
6.2 Hz, 2H), 7.79–7.77 (d, J = 8.0 Hz, 2H), 7.61–7.50 (m,
7H), 7.42 (t, J = 7.1 Hz, 1H), 7.33 (t, J = 7.0 Hz, 1H),
7.25–7.24 (d, J = 7.4 Hz, 1H), 5.63 (s, 1H), 5.42 (q, J = 6.3
Hz, 1H), 2.33 (s, 3H), 1.69–1.67 (d, J = 8.0 Hz, 3H).
13C{1H} NMR (100 MHz, CDCl3) δ 143.6, 134.9, 134.8,
134.4, 134.2, 133.7, 130.4, 130.4, 130.2, 128.1, 128.1,
127.1, 126.4, 125.7, 69.7, 25.3, 19.0.
3
3
(t, JHH = 7.6 Hz, 4H), 6.66–6.64 (d, JHH = 7.6 Hz, 8H),
5.00 (s, 4H), 4.52 (s, 2H, ZnH), 3.08–2.99 (m, 8H), 2.76–
2.66 (m, 8H), 2.42–2.33 (m, 8H), 2.22–2.13 (m, 8H), 1.30
3
3
(t, JHH = 7.5 Hz, 24H), 0.96 (t, JHH = 7.6 Hz, 24H).
13C{1H} NMR (100 MHz, C6D6) δ 157.2, 142.6, 141.1,
138.8, 135.2, 126.7, 126.3, 125.7, 125.2, 24.9, 24.2, 14.4,
6
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The Journal of Organic Chemistry
Diphenyl(1-(p-tolyl)ethoxy)silane (4c)27. NMR yield:
5.52 (s, 1H), 5.12 (q, J = 6.3 Hz, 1H), 1.57–1.56 (d, J = 6.5
Hz, 3H).
(>99%). 1H NMR (400 MHz, CDCl3) δ 7.77–7.69 (m, 4H),
7.54–7.45 (m, 6H), 7.37–7.36 (d, J = 7.0 Hz, 2H), 7.25–
7.24 (d, J = 6.8 Hz, 2H), 5.55 (s, 1H), 5.14 (q, J = 6.4 Hz,
1H), 2.46 (s, 3H), 1.64–1.63 (d, J = 6.4 Hz, 3H). 13C{1H}
NMR (100 MHz, CDCl3) δ 142.4, 136.8, 134.8, 134.7,
134.4, 134.2, 130.3, 130.3, 129.0, 128.0, 128.0, 125.6,
72.6, 26.3, 21.2.
1
2
3
4
5
6
7
8
Methyl 4-(1-((diphenylsilyl)oxy)ethyl)benzoate (4l). NMR
yield: (>99%, colorless oil). 1H NMR (400 MHz, CDCl3) δ
8.06–8.03 (m, 2H), 7.69–7.66 (m, 2H), 7.65–7.62 (m, 2H),
7.47–7.43 (m, 8H), 5.48 (s, 1H), 5.12–5.06 (m, 1H), 3.96
(s, 3H), 1.57–1.56 (d, J = 6.5 Hz, 3H). HRMS (ESI) m/z:
[M + nNa]+ Calcd for C22H22O3SiNa 385.1230, Found:
385.1217.
(1-(4-Methoxyphenyl)ethoxy)diphenylsilane (4d)27. NMR
9
1
yield: (>99%). H NMR (400 MHz, CDCl3) δ 7.73–7.66
Diphenyl((6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-
yl)oxy)silane (4m). NMR yield: (>99%, colorless oil). H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(m, 4H), 7.52–7.44 (m, 6H), 7.37–7.34 (d, J = 8.6 Hz, 2H),
6.95–6.93 (d, J = 8.0 Hz, 2H), 5.51 (s, 1H), 5.09–5.05 (m,
1H), 3.87 (s, 3H), 1.61–1.60 (d, J = 5.9 Hz, 3H).
1
NMR (400 MHz, CDCl3) δ 7.96–7.86 (m, 2H), 7.82–7.80
(m, 2H), 7.64–7.47 (m, 6H), 7.38–7.18 (m, 4H), 5.68 (s,
1H), 5.23– 5.17 (m, 1H), 3.21–3.15 (m, 1H), 2.84–2.78 (m,
1H), 2.28–2.12 (m, 2H), 1.96–1.58 (m, 4H). HRMS (ESI)
m/z: [M + nNa]+ Calcd for C23H24OSiNa 367.1489, Found:
367.1481.
Diphenyl(1-phenylpropoxy)silane (4e)27. NMR yield:
1
(>99%). H NMR (400 MHz, CDCl3) δ 7.75–7.74 (d, J =
6.8 Hz, 2H), 7.69–7.67 (d, J = 6.5 Hz, 1H), 7.53–7.49 (m,
4H), 7.44–7.41 (m, 4H), 7.37–7.28 (m, 4H), 5.53 (s, 1H),
4.87–4.84 (m, 1H), 2.05–1.89 (m, 2H), 1.01 (t, J = 7.4 Hz,
3H).
(2-Methyl-1-phenylpropoxy)diphenylsilane (4f)29. NMR
yield: (>99%).1H NMR (400 MHz, CDCl3) δ 7.70–7.68 (d,
J = 7.5 Hz, 2H), 7.63–7.61 (d, J = 7.2 Hz, 2H), 7.52–7.46
(m, 4H), 7.40–7.35 (m, 6H), 5.43 (s, 1H), 4.57–4.55 (d, J =
6.2 Hz, 1H), 2.21–2.07 (m, 1H), 1.10–1.08 (d, J = 6.5 Hz,
3H), 0.89–0.88 (d, J = 6.6 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 142.7, 135.7, 134.8, 134.7, 134.4, 130.3,
130.1, 128.0, 127.9, 127.8, 127.2, 127.0, 82.3, 36.2, 19.0,
18.4.
Diphenyl((6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-
yl)oxy)silane (4n’). NMR yield: (>99%, light yellowish
1
oil). H NMR (400 MHz, CDCl3) δ 8.51–8.50 (d, J = 7.5
Hz, 1H), 8.42–8.41 (d, J = 7.5 Hz, 1H), 7.82–7.77 (m, 2H),
7.69–7.65 (m, 4H), 7.58–7.57 (m, 1H), 7.45–7.41 (m, 7H),
7.15–7.04 (m, 2H), 5.27–5.17 (m, 2H), 1.54–1.53 (d, J =
6.5 Hz, 3H), 1.43–1.42 (d, J = 6.5 Hz, 3H). HRMS (ESI)
m/z: [M + nNa]+ Calcd for C26H26N2O2SiNa 449.1656,
Found: 449.1638.
(1-(Benzofuran-2-yl)ethoxy)diphenylsilane (4o). NMR
yield: (>99%, colorless oil). 1H NMR (400 MHz, CDCl3) δ
7.81 (t, J = 7.6 Hz, 4H), 7.77–7.75 (d, J = 6.3 Hz, 4H),
7.53–7.51 (m, 6H), 6.72 (s, 1H), 5.68 (s, 1H), 5.33(q, J =
6.5 Hz, 1H), 1.82–1.80 (d, J = 6.5 Hz, 3H). HRMS (ESI)
m/z: [M + nNa]+ Calcd for C22H20O2SiNa 367.1125, Found:
367.1134.
(1-(4-Fluorophenyl)ethoxy)diphenylsilane (4g)30. NMR
yield: (>99%). 1H NMR (400 MHz, CDCl3) δ 7.74–7.72 (d,
J = 6.80 Hz, 2H), 7.68–7.66 (d, J = 7.0 Hz, 2H), 7.54–7.43
(m, 6H), 7.40–7.37 (m, 2H), 7.08 (t, J = 8.5 Hz, 2H), 5.53
(s, 1H), 5.11(q, J = 6.4 Hz, 1H), 1.61–1.59 (d, J = 6.2Hz,
3H).
(1-(Naphthalen-1-yl)ethoxy)diphenylsilane (4p)32. NMR
1
yield: (>99%). H NMR (400 MHz, CDCl3) δ 8.14–8.12
(1-(2-Chlorophenyl)ethoxy)diphenylsilane (4h)27. NMR
(m, 1H), 7.97–7.96 (d, J = 7.0 Hz, 1H), 7.88–7.86 (d, J =
8.0 Hz, 2H), 7.79–7.72 (m, 3H), 7.60–7.43 (m, 10H), 5.91–
5.86 (m, 1H), 5.61 (q, J = 8.00 Hz, 1H), 1.81–1.79 (d, J =
6.0 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 141.0,
135.8, 134.8, 134.3, 134.1, 133.8, 130.4, 130.3, 130.1,
128.9, 128.1, 128.0, 127.7, 125.8, 125.6, 125.4, 123.4,
123.0, 70.3, 25.9.
Diphenyl(phenyl(o-tolyl)methoxy)silane (4q). NMR yield:
(>99%, colorless oil). 1H NMR (400 MHz, CDCl3) δ 7.91–
7.89 (d, J = 7.5 Hz, 1H), 7.85–7.82 (m, 4H), 7.61–7.54 (m,
7H), 7.51–7.41 (m, 6H), 7.30–7.28 (d, J = 7.3 Hz, 1H),
6.31 (s, 1H), 5.68 (s, 1H), 2.30 (s, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 143.1, 141.5, 135.4, 135.4, 135.1, 134.1,
134.1, 130.7, 130.6, 128.5, 128.3, 128.3, 127.7, 127.7,
127.5, 127.4, 127.4, 126.3, 76.0, 19.7. HRMS (ESI) m/z:
[M + nNa]+ Calcd for C26H24OSiNa 403.1489, Found:
403.1487.
1
yield: (>99%). H NMR (400 MHz, CDCl3) δ 7.84–7.81
(m, 1H), 7.77–7.74 (m, 2H), 7.71–7.68 (m, 2H), 7.53–7.44
(m, 6H), 7.37–7.34 (m, 2H), 7.28–7.23 (m, 1H), 5.57–5.56
(d, J = 6.2 Hz, 1H), 5.54–5.49 (m, 1H), 1.60–1.59 (d, J =
6.3 Hz, 3H).
(1-(4-Chlorophenyl)ethoxy)diphenylsilane (4i)27. NMR
1
yield: (>99%). H NMR (400 MHz, CDCl3) δ 7.71–7.64
(m, 4H), 7.50–7.43 (m, 6H), 7.34–7.33 (d, J = 8.0 Hz, 4H,),
5.51 (s, 1H), 5.07–5.02 (m, 1H), 1.57–1.56 (d, J = 5.9 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ 143.8, 135.7,
134.7, 134.7, 133.8, 132.8, 130.4, 130.4, 128.4, 128.1,
128.0, 127.0, 72.1, 26.2.
(1-(4-Bromophenyl)ethoxy)diphenylsilane (4j)29. NMR
1
yield: (>99%). H NMR (400 MHz, CDCl3) δ 7.76–7.72
(m, 4H), 7.71–7.69 (d, J = 7.8 Hz, 2H), 7.53–7.50 (m, 6H),
7.33–7.31 (d, J = 8.1 Hz, 2H), 5.56 (s, 1H), 5.07 (m,
1H),1.61–1.59 (d, J = 6.4 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 144.4, 135.8, 134.7, 134.7, 134.4, 131.4,
130.0, 128.2, 128.1, 128.0, 127.4, 121.0, 72.2, 26.2.
4-(1-((Diphenylsilyl)oxy)ethyl)benzonitrile (4k)31. NMR
yield: (>99%). 1H NMR (400 MHz, CDCl3) δ 7.71–7.69 (d,
J = 7.5 Hz, 2H), 7.67–7.65 (m, 2H), 7.53–7.41 (m, 10H),
Diphenyl(tridecan-2-yloxy)silane (4r). NMR yield: (>99%,
colorless oil). 1H NMR (400 MHz, CDCl3) δ 7.72–7.69 (m,
4H), 7.51–7.43 (m, 6H), 5.53 (s, 1H), 4.06 (q, J = 6.0 Hz,
1H), 1.67–1.64 (m, 1H), 1.54–1.44 (m, 2H), 1.34–1.31 (m,
17H), 1.28–1.27 (d, J = 6.2 Hz, 3H), 0.96 (t, J = 6.6 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ 134.7, 134.7,
130.2, 127.9, 71.0, 39.3, 32.0, 29.7, 29.7, 29.6, 29.6, 29.4,
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25.7, 23.3, 22.7, 14.1. HRMS (ESI) m/z: [M + nNa]+ Calcd
Page 8 of 13
was stirred at room temperature for 6 h. The progress of the
reaction was monitored by 1H NMR in CDCl3, which
indicated the formation of boronate ester by showing a new
OCH resonance (6a-6y). Then the reaction mixture was
treated with silica gel and methanol, heated in an oil bath at
1
2
3
4
5
6
7
8
for C25H38OSiNa 405.2584, Found: 405.2591.
(1-(4-(methylthio)phenyl)ethoxy)diphenylsilane (4s). NMR
1
yield (>99%, colorless oil). H NMR (400 MHz, CDCl3) δ
7.77–7.73 (m, 4H), 7.53–7.48 (m, 6H), 7.41–7.39 (d, J =
8.3 Hz, 2H), 7.35–7.33 (d, J = 8.3 Hz, 2H), 5.58 (s, 1H),
5.14–5.09 (m, 1H), 2.58 (s, 3H), 1.65–1.63 (d, J = 6.4 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ 142.4, 135.8,
134.8, 134.7, 130.4, 130.4, 130.0, 128.2, 128.1, 128.0,
126.8, 126.3, 72.4, 26.2, 16.1. HRMS (ESI) m/z: [M +
nNa]+ Calcd for C21H22OSSiNa 373.1053, Found:
373.1042.
o
60 C for 6h. Next, combining organic layers followed by
purification through column chromatography using silica
gel as a stationary phase and ethyl acetate and n-hexane as
the mobile phase yielded corresponding secondary
alcohols.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4,4,5,5-Tetramethyl-2-(1-phenylethoxy)-1,3,2-
dioxaborolane (6a)36. NMR yield: (>99%). H NMR (400
1
MHz, CDCl3) δ 7.41–7.40 (d, J = 7.2 Hz, 2H), 7.35 (t, J =
7.5 Hz, 2H), 7.27 (t, J = 7.1 Hz, 1H), 5.31 (q, J = 6.4 Hz,
1H), 1.54–1.53 (d, J = 6.4 Hz, 3H), 1.28 (s, 6H), 1.25 (s,
6H). 13C{1H} NMR (100 MHz, CDCl3) δ 144.6, 128.2,
127.1, 125.3, 82.7, 72.6, 25.4, 24.5, 24.5.
((4-(2-((diphenylsilyl)oxy)-2-
phenylethoxy)benzyl)oxy)diphenylsilane (4t). NMR yield:
1
(>99%, colorless gum). H NMR (400 MHz, CDCl3) δ
7.967.80 (m, 10H), 7.57-7.55 (d, J = 7.0 Hz, 15H),
7.427.40 (d, J = 7.7 Hz, 2H), 6.996.96 (m, 2H),
5.795.79 (d, J = 3.5 Hz, 1H), 5.71 (s, 1H), 5.45 (d, J
= 10.6 Hz), 5.175.16 (d, J = 3.1 Hz, 2H), 4.384.33 (s,
1H), 4.25 – 4.23 (m, 1H). HRMS (ESI) m/z: [M + nNa]+
Calcd for C39H36O3Si2Na 631.2095, Found: 631.2072.
4,4,5,5-Tetramethyl-2-(1-(o-tolyl)ethoxy)-1,3,2-
1
dioxaborolane (6b)37. NMR yield: (>99%). H NMR (400
MHz, CDCl3) δ 7.58–7.56 (d, J = 8.0 Hz, 1H), 7.23 (t, J =
8.0 Hz, 1H), 7.19–7.12 (m, 2H), 5.49 (q, J = 6.4 Hz, 1H),
2.37 (s, 3H), 1.50–1.48 (d, J = 6.4 Hz, 3H), 1.27 (s, 6H),
1.23 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ 142.8,
133.7, 130.0, 126.9, 126.1, 125.1, 82.7, 69.5, 24.5, 24.5,
24.2, 19.0.
(1-(furan-2-yl)ethoxy)diphenylsilane (4u). NMR yield:
1
(>99%, yellowish oil.). H NMR (400 MHz, CDCl3) δ
7.767.70 (m, 4H), 7.537.44 (m, 6H), 7.417.39 (d, J =
6.6 Hz, 1H), 6.37 (t, J = 5.3 Hz, 1H), 6.286.27 (d, J = 3.1
Hz, 1H), 5.17 (q, J = 10.0 Hz, 1H), 1.691.67 (d, J = 6.6
Hz, 3H). HRMS (ESI) m/z: [M + nNa]+ Calcd for
C18H18O2SiNa 317.0968, Found: 317.0970.
(cyclohex-2-en-1-yloxy)diphenylsilane (4v)33. NMR yield
(>99%). 1H NMR (400 MHz, CDCl3) δ 7.77–7.76 (m, 4H),
7.53–7.47 (s, 6H), 5.92–5.89 (d, J = 13.3 Hz, 1H), 5.86–
5.83 (d, J = 12.0 Hz, 1H), 5.63 (s, 1H), 4.58–4.47 (m, 1H),
2.17–2.11 (m, 1H), 2.04–1.95 (m, 2H), 1.92–1.82 (m, 2H),
1.67–1.58 (m, 1H).
4,4,5,5-Tetramethyl-2-(1-(p-tolyl)ethoxy)-1,3,2-
dioxaborolane (6c)36. NMR yield: (>99%).1H NMR (400
MHz, CDCl3) δ 7.31–7.29 (d, J = 8.0 Hz, 2H), 7.17–7.16
(d, J = 8.0 Hz, 2H), 5.28 (q, J = 6.4 Hz, 1H), 2.36 (s, 3H),
1.52–1.51 (d, J = 6.4 Hz, 3H),1.28 (s, 6H), 1.25 (s, 6H).
13C{1H} NMR (100 MHz, CDCl3) δ 141.6, 136.6, 128.8,
125.3, 82.7, 72.4, 25.4, 24.5, 24.5 21.1.
2-(1-(2-Methoxyphenyl)ethoxy)-4,4,5,5-tetramethyl-1,3,2-
1
dioxaborolane (6d)36. NMR yield: (>99%). H NMR (400
MHz, CDCl3) δ 7.32–7.30 (d, J = 8.0 Hz, 2H), 6.88–6.86
(d, J = 8.0 Hz, 2H), 5.24 (q, J = 6.4 Hz, 1H), 3.81 (s, 3H),
1.50–1.48 (d, J = 6.5 Hz, 3H), 1.26 (s, 6H), 1.23 (s, 6H).
13C{1H} NMR (100 MHz, CDCl3) δ 158.7, 136.8, 126.6,
113.5, 82.6, 72.2, 55.2, 25.3, 24.5, 24.5.
(1-(4-nitrophenyl)ethoxy)diphenylsilane (4w)34. NMR
yield: (>99%). 1H NMR (400 MHz, CDCl3) δ 8.22–8.20 (d,
J = 7.9 Hz, 2H), 7.69–7.62 (m, 4H), 7.55–7.53 (d, J = 8.0
Hz, 2H), 7.48–7.42 (m, 6H), 5.51 (s, 1H), 5.16 (q, J = 6.5
Hz, 1H), 1.58–1.57 (d, J = 6.4 Hz, 3H).
4,4,5,5-Tetramethyl-2-(1-phenylpropoxy)-1,3,2-
2-(1-((diphenylsilyl)oxy)ethyl)aniline (4x)35. NMR yield:
1
dioxaborolane (6e)15a. NMR yield: (>99%). H NMR (400
1
(81%). H NMR (400 MHz, CDCl3) δ 7.70–7.64 (m, 6H),
MHz, CDCl3) δ 7.38–7.35 (m, 4H), 7.28–7.27 (m, 1H),
5.07–5.06 (m, 1H), 1.86–1.81 (m, 2H), 1.27 (s, 6H), 1.24
(s, 6H), 0.94 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz,
CDCl3) δ 143.4, 128.0, 127.1, 125.9, 82.6, 77.7, 32.0, 24.5,
24.5, 9.8.
7.47–7.42 (m, 4H), 7.13 (t, J = 7.4 Hz, 1H), 7.02–7.00 (d, J
= 8.0 Hz, 1H), 6.75–6.68 (m, 2H), 5.50 (s, 1H), 5.11 (q, J =
6.5 Hz, 1H), 4.27 (br, 2H), 1.69–1.67 (d, J = 6.8 Hz, 3H).
4,4,5,5-Tetramethyl-2-(2-methyl-1-phenylpropoxy)-1,3,2-
diphenyl((4-phenylbut-3-yn-2-yl)oxy)silane (4y). NMR
1
dioxaborolane (6f)38. NMR yield: (>99%). H NMR (400
1
yield: (>99%, yellow oil). H NMR (400 MHz, CDCl3) δ
MHz, CDCl3) δ 7.34–7.33 (m, 4H), 7.28–7.24 (m, 1H),
4.85–4.84 (d, J = 6.2 Hz, 1H), 2.02–1.97 (m, 1H), 1.24 (s,
6H), 1.20 (s, 6H), 0.94–0.93 (d, J = 6.7 Hz, 3H), 0.87–0.85
(d, J = 6.8 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ
142.4, 127.8, 126.9, 126.5, 82.6, 81.4, 35.3, 24.5, 18.8,
17.5.
7.78–7.74 (m, 4H), 7.48–7.42 (m, 6H), 7.38–7.32 (m, 5H),
5.67 (s, 1H), 5.00 (q, J = 6.6 Hz, 1H), 1.66–1.65 (d, J = 6.5
Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 135.7, 134.8,
134.8, 134.3, 131.6, 130.3, 128.2, 128.1, 128.0, 128.0,
122.8, 90.4, 84.8, 61.3, 25.0. HRMS (ESI) m/z: [M + nNa]+
Calcd for C22H20OSiNa 351.1176, Found: 351.1171.
General Procedure for Hydroboration of Ketones.
Ketone (1.0 mmol), HBpin (1.1 mmol), 3 mg (0.2 mol %)
of catalyst 3 were charged in an air-tight vial with a
magnetic bead inside the glove box. The reaction mixture
2-(1-(4-fluorophenyl)ethoxy)-4,4,5,5-tetramethyl-1,3,2-
1
dioxaborolane (6g)36. NMR yield: (>99%). H NMR (400
MHz, CDCl3) δ 7..33 (m, 2H), 7.01 (t, J = 8.6 Hz,
2H), 5.26 (q, J = 6.4 Hz, 1H), 1.49–1.48 (d, J = 6.4 Hz,
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The Journal of Organic Chemistry
3H), 1.25 (s, 6H), 1.23 (s, 6H). 13C{1H} NMR (100 MHz,
CDCl3) δ 163.1, 160.7, 140.3 (d, J = 3.1 Hz), 127.0 (d, J =
8.0 Hz), 115.0, 114.8, 82.8, 72.0, 25.3, 24.5, 24.4.
2-(1-(Benzofuran-2-yl)ethoxy)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (6o)43. NMR yield (>99%).1H NMR (400
MHz, CDCl3) δ 7.56–7.54 (d, J = 8.0 Hz, 1H), 7.47–7.45
(d, J = 8.0 Hz, 1H), 7.27–7.22 (m, 2H), 6.64 (s, 1H), 5.43
(q, J = 6.5 Hz, 1H), 1.67–1.66 (d, J = 6.6 Hz, 3H), 1.30 (s,
12H). 13C{1H} NMR (100 MHz, CDCl3) δ 159.2, 154.7,
128.2, 123.9, 122.5, 120.9, 111.2, 102.0, 83.0, 66.6, 24.6,
24.5, 21.2.
1
2
3
4
5
6
7
8
3-(1-(3-chlorophenyl)ethoxy)-4,4,5,5-
1
tetramethyldioxaborolane (6h)39. NMR yield: (>99%). H
NMR (400 MHz, CDCl3) δ 7.66–7.64 (d, J = 8.0 Hz, 1H),
7.31–7.28 (m, 2H), 7.21–7.19 (m, 1H), 5.63 (q, J = 6.3 Hz,
1H), 1.51–1.49 (d, J = 6.3 Hz, 3H), 1.27 (s, 6H), 1.24 (s,
6H). 13C{1H} NMR (100 MHz, CDCl3) δ 142.2, 131.0,
129.1, 128.1, 127.0, 126.6, 82.8, 69.5, 24.5, 23.8.
4,4,5,5-Tetramethyl-2-(naphthalen-1-yl)ethoxy)-1,3,2-
9
1
dioxaborolane (6p)17c. NMR yield (>99%). H NMR (400
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
MHz, CDCl3) δ 8.12–8.10 (d, J = 8.2 Hz, 1H), 7.88–7.86
(d, J = 8.0 Hz, 1H), 7.76 (t, J = 7.7 Hz, 2H), 7.53–7.46 (m,
3H), 6.04 (q, J = 6.3 Hz, 1H), 1.68–1.67 (d, J = 6.4 Hz,
3H), 1.27 (s, 6H), 1.23 (s, 6H). 13C{1H} NMR (100 MHz,
CDCl3) δ 140.3, 133.7, 129.9, 128.8, 127.5, 125.7, 125.6,
125.3, 123.3, 122.4, 82.8, 69.9, 25.0, 24.5, 24.5.
2-(1-(4-Chlorophenyl)ethoxy)-4,4,5,5-tetramethyl-1,3,2-
1
dioxaborolane (6i)40. NMR yield: (>99%). H NMR (400
MHz, CDCl3) δ 7.30–7.28 (m, 4H), 5.25 (q, J = 6.4 Hz,
1H), 1.49–1.47 (d, J = 6.4 Hz, 3H), 1.25 (s, 6H), 1.23 (s,
6H). 13C{1H} NMR (100 MHz, CDCl3) δ 143.1, 132.7,
128.3, 126.7, 82.8, 71.9, 25.3, 24.5, 24.5.
4,4,5,5-tetramethyl-2-(phenyl(o-tolyl)methoxy)-1,3,2-
dioxaborolane (6q)43. NMR yield (>99%).1H NMR (400
MHz, CDCl3) δ 7.65–7.63 (d, J = 8.0 Hz, 1H), 7.39–7.37
(d, J = 8.0 Hz, 2H), 7.33 (t, J = 7.7 Hz, 2H), 7.29–7.22 (m,
3H), 7.17–7.15 (d, J = 8.0 Hz, 1H), 6.40 (s, 1H), 2.31 (s,
3H), 1.26 (s, 6H), 1.25 (s, 6H). 13C{1H} NMR (100 MHz,
CDCl3) δ 142.3, 140.8, 135.1, 130.3, 128.2, 127.3, 127.2,
127.1, 126.9 125.9, 82.9, 75.3, 24.5, 24.5, 19.5.
2-(1-(4-Bromophenyl)ethoxy)-4,4,5,5-tetramethyl-1,3,2-
1
dioxaborolane (6j)36. NMR yield: (>99%). H NMR (400
MHz, CDCl3) δ 7.46–7.44 (d, J = 8.5 Hz, 2H), 7.26–7.24
(d, J = 8.4 Hz, 2H), 5.23 (q, J = 6.4 Hz, 1H), 1.48–1.47 (d,
J = 6.5 Hz, 3H), 1.25 (s, 6H), 1.22 (s, 6H). 13C{1H} NMR
(100 MHz, CDCl3) δ 143.6, 131.2, 127.1, 120.8, 82.8, 71.9,
25.3, 24.5, 24.5.
4-(1-((4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-
4,4,5,5-tetramethyl-2-(tridecan-2-yloxy)-1,3,2-
yl)oxy)ethyl)benzonitrile (6k)38. NMR yield: (>99%). H
1
1
dioxaborolane (6r)43. H NMR (400 MHz, CDCl3) δ 4.18–
NMR (400 MHz, CDCl3) δ 7.62–7.60 (d, J = 8.2 Hz, 2H),
7.47–7.45 (d, J = 8.2 Hz, 2H), 5.29 (q, J = 6.5 Hz, 1H),
1.48–1.47 (d, J = 6.5 Hz, 3H), 1.24 (s, 6H), 1.21 (s, 6H).
13C{1H} NMR (100 MHz, CDCl3) δ 149.8, 132.1, 126.0,
118.8, 110.9, 83.0, 71.8, 25.2, 24.5, 24.5.
4.14 (m, 1H), 1.34–1.31 (m, 3H), 1.27 (s, 17H), 1.26 (s,
12H), 1.19–1.18 (d, J = 6.2 Hz, 3H), 0.89 (t, J = 6.8 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ 82.3, 70.9, 38.2,
31.9, 29.6, 29.6, 29.6, 29.5, 29.3, 25.5, 24.5, 24.4, 22.6,
22.5, 14.0.
Methyl-4-(1-((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)oxy)ethyl)benzoate (6l)17b. NMR yield: (>99%). 1H
NMR (400 MHz, CDCl3) δ 8.02–8.00 (d, J = 8.3 Hz, 2H),
7.46–7.43 (d, J = 8.2 Hz, 2H), 5.32 (q, J = 6.4 Hz, 1H),
3.92 (s, 3H), 1.51–1.50 (d, J = 6.5 Hz, 3H), 1.26 (s, 6H),
1.22 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ 167.0,
149.7, 129.6, 128.9, 125.2, 82.9, 72.2, 52.0, 25.3, 24.5,
24.4.
4,4,5,5-tetramethyl-2-(1-(4-(methylthio)phenyl)ethoxy)-
1
1,3,2-dioxaborolane (6s)43. NMR yield (>99%). H NMR
(400 MHz, CDCl3) δ 7.32–7.30 (d, J = 8.3 Hz, 2H), 7.25–
7.22 (d, J = 8.3 Hz, 2H), 5.25 (q, J = 6.4 Hz, 1H), 2.48 (s,
3H), 1.49–1.48 (d, J = 6.3 Hz, 3H), 1.26 (s, 6H), 1.23 (s,
6H). 13C NMR (100 MHz, CDCl3) δ 141.6, 136.9, 126.6,
125.9, 82.7, 72.2, 25.3, 24.5, 24.5, 16.0.
4,4,5,5-tetramethyl-2-((4-(2-phenyl-2-((4,4,5,5-tetramethyl-
1,3,2-dioxaborolan-2-yl)oxy)ethoxy)benzyl)oxy)-1,3,2-
4,4,5,5-Tetramethyl-2-((6,7,8,9-tetrahydro-5H-
1
dioxaborolane (6t). NMR yield: (>99%, yellow oil). H
benzo[7]annulen-5-yl)oxy)-1,3,2-dioxaborolane
(6m)41.
NMR (400 MHz, CDCl3) δ 7.48–7.47 (d, J = 7.3 Hz, 2H),
7.40–7.37 (m, 2H), 7.34–7.32 (d, J = 7.2 Hz, 1H), 7.28–
7.26 (d, J = 8.6 Hz, 2H), 6.88–6.86 (d, J = 8.6 Hz, 2H),
5.53–5.50 (q, J = 12.0 Hz, 1H), 4.86 (s, 2H), 4.10–4.03 (m,
2H), 1.29 (s, 12H), 1.27 (s, 12H). 13C{1H} NMR (100
MHz, CDCl3) δ 158.2, 139.3, 131.7, 128.4, 128.3, 127.9,
126.2, 114.4, 83.0, 82.8, 74.8, 72.9, 66.4, 24.9, 24.6, 24.5.
HRMS (ESI) m/z: [M + nNa]+ Calcd for C27H38B2O7Na
519.2705, Found: 519.2728.
1
NMR yield (>99%). H NMR (400 MHz, CDCl3) δ 7.50–
7.48 (d, J = 8.0 Hz, 1H), 7.22–7.14 (m, 2H), 7.11–7.10 (d,
J = 7.1 Hz, 1H), 5.30–5.28 (d, J = 7.8 Hz, 1H), 2.99–2.94
(m, 1H), 2.77 (t, J = 7.7 Hz, 1H), 2.08–2.04 (m, 1H), 1.99–
1.92 (m, 1H), 1.90–1.78 (m, 3H), 1.50–1.42 (m, 1H), 1.29
(s, 6H), 1.26 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ
143.1, 140.6, 129.3, 126.8, 125.9, 125.1, 82.7, 76.2, 36.5,
35.7, 27.7, 27.6, 24.6, 24.5.
2-(1-(furan-2-yl)ethoxy)-4,4,5,5-tetramethyl-1,3,2-
2-(1-((4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-
1
dioxaborolane (6u)44. NMR yield: (>99%). H NMR (400
yl)oxy)ethyl)pyridine (6n)42. NMR yield (>99%).1H NMR
(400 MHz, CDCl3) δ 8.54–8.53 (d, J = 5.5 Hz, 1H), 7.93 (t,
J = 7.7 Hz, 1H), 7.43 (t, J = 6.5 Hz, 2H), 5.19 (q, J = 6.6
Hz, 1H), 1.50–1.49 (d, J = 6.7 Hz, 3H), 1.25 (s, 6H), 1.23
(s, 6H).13C{1H} NMR (100 MHz, CDCl3) δ 163.6, 141.6,
140.8, 123.7, 119.7, 80.1, 71.3, 25.8, 25.7, 22.4.
MHz, CDCl3) δ 7.32–7.31 (m, 1H), 6.27–6.27 (m, 1H),
6.22–6.21 (d, J = 6.5 Hz, 1H), 5.25 (q, J = 8.6 Hz, 1H),
1.54–1.52 (d, J = 6.6 Hz, 3H), 1.24 (s, J = 6.5 Hz, 12H).
13C{1H} NMR (100 MHz, CDCl3) δ 156.2, 141.6, 109.9,
105.5, 82.8, 66.0, 24.5, 24.4, 20.9.
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2-(cyclohex-2-en-1-yloxy)-4,4,5,5-tetramethyl-1,3,2-
NMR (400 MHz, CDCl3) δ 7.32–7.30 (d, J = 8.6 Hz, 2H),
1
dioxaborolane (6v)42. NMR yield: (>99%). H NMR (400
6.91–6.88 (d, J = 8.7 Hz, 2H), 4.88 (q, J = 6.4 Hz, 1H),
3.82 (s, 3H), 2.14 (br, 1H), 1.49–1.48 (d, J = 6.4 Hz, 3H).
13C{1H} NMR (100 MHz, CDCl3) δ 158.9, 138.0, 126.6,
113.8, 69.9, 55.3, 25.0.
1
2
3
4
5
6
7
8
MHz, CDCl3) δ 5.82–5.77 (m, 1H), 5.71–5.68 (d, J = 17.1
Hz, 1H), 4.56 (dd, J = 3.0, 1.4 Hz, 1H), 2.04–1.98 (m, 1H),
1.96–1.92 (d, J = 19.5 Hz, 1H), 1.86–1.81 (m, 1H), 1.78–
1.74 (m, 1H), 1.70–1.63 (m, 1H), 1.58–1.50 (m, 1H), 1.25
(s, 12H, C(CH3)2).13C{1H} NMR (100 MHz, CDCl3) δ
130.2, 128.8, 82.5, 68.0, 30.7, 24.8, 24.5, 18.9.
1-Phenylpropan-1-ol (7e)43. The title compound was
purified by silica gel chromatography (hexane/ethyl
1
acetate, 85:15); Yield: 0.110 g (81%, colorless oil). H
4,4,5,5-tetramethyl-2-(1-(4-nitrophenyl)ethoxy)-1,3,2-
NMR (400 MHz, CDCl3) δ 7.40–7.35 (m, 4H), 7.32–7.29
(m, 1H), 4.60 (t, J = 6.4 Hz, 1H), 2.20 (br, 1H), 1.90–1.74
(m, 2H), 0.94 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 144.6, 128.3, 127.4, 126.0, 76.0, 31.8,
10.1.
2-Methyl-1-phenylpropan-1-ol (7f)47. The title compound
was purified by silica gel chromatography (hexane/ethyl
acetate, 90:10); Yield: 0.105g (70%, colorless oil). 1H
NMR (400 MHz, CDCl3) δ 7.37–7.32 (m, 5H), 4.37–4.35
(d, J = 6.8 Hz, 1H), 2.20 (br, 1H), 2.00–1.95 (m, 1H),
1.04–1.02 (d, J = 6.7 Hz, 3H), 0.83–0.82 (d, J = 6.4 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ 143.6, 128.1,
127.3, 126.6, 80.0, 35.2, 19.0, 18.3.
9
1
dioxaborolane (6w)45. NMR yield: (>99%). H NMR (400
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15
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17
18
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21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
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41
42
43
44
45
46
47
48
49
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52
53
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55
56
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MHz, CDCl3) δ 8.21–8.19 (d, J = 8.5 Hz, 2H), 7.55–7.53
(d, J = 8.4 Hz, 2H), 5.36 (q, J = 6.4 Hz, 1H), 1.53–1.51 (d,
J = 6.5 Hz, 3H), 1.26 (s, 6H), 1.23 (s, 6H). 13C{1H} NMR
(100 MHz, CDCl3) δ 151.8, 147.1, 126.1, 123.6, 83.1, 71.7,
25.2, 24.5, 24.5.
2-(1-((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
1
yl)oxy)ethyl)aniline (6x)15a. NMR yield: (86%). H NMR
(400 MHz, CDCl3) δ 7.13–7.05 (m, 2H), 6.71 (t, J = 7.6
Hz, 1H), 6.66–6.64 (d, J = 8.0 Hz, 1H), 5.31 (q, J = 6.4 Hz,
1H), 4.18 (br, 2H), 1.59–1.58 (d, J = 6.9 Hz, 3H), 1.26 (s,
6H), 1.24 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ
144.5, 134.3, 128.3, 127.3, 117.9, 116.5, 82.9, 73.0, 24.5,
24.5, 21.9.
1-(4-fluorophenyl)ethanol (7g)43. The title compound was
purified by silica gel chromatography (hexane/ethyl
1
4,4,5,5-tetramethyl-2-((4-phenylbut-3-yn-2-yl)oxy)-1,3,2-
acetate, 90:10); Yield: 0.116 g (83%, colorless oil). H
1
dioxaborolane (6y)46. NMR yield: (>99%). H NMR (400
NMR (400 MHz, CDCl3) δ 7.33–7.29 (m, 2H), 7.01 (t, J =
8.7 Hz, 2H), 4.87 (q, J = 6.4 Hz, 1H), 2.31 (br, 1H), 1.46–
1.44 (d, J = 6.4Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3)
δ 163.3, 160.8, 141.5 (d, J = 3.1 Hz), 127.0 (d, J = 8.1 Hz),
115.3, 115.1, 69.7, 25.2.
MHz, CDCl3) δ), 7.46–7.43 (m, 6H), 7.32–7.30 (m, 5H),
5.12 (q, J = 6.4 Hz, 1H), 1.59–1.57 (d, J = 6.5 Hz, 3H),
1.30 (s, 12H). 13C{1H} NMR (100 MHz, CDCl3) δ 131.6,
128.2, 128.1, 122.8, 89.8, 83.6, 83.0, 61.3, 24.5, 23.9.
1-(2-Chlorophenyl)ethan-1-ol (7h)48. The title compound
was purified by silica gel chromatography (hexane/ethyl
Analytical Data of 2o Alcohols (7a-7s).
1-Phenylethan-1-ol (7a)43. The title compound was purified
1
acetate, 90:10); Yield: 0.111 g (71%, colorless oil). H
NMR (400 MHz, CDCl3) δ 7.58–7.56 (d, J = 8.0 Hz, 1H),
7.33–7.26 (m, 2H),7.19 (t, J = 7.7 Hz, 1H), 5.28 (q, J = 6.3
Hz, 1H), 3.17 (br, 1H), 1.46–1.45 (d, J = 6.4 Hz, 3H).
13C{1H} NMR (100 MHz, CDCl3) δ 143.1, 131.5, 129.3,
128.3, 127.2, 126.4, 66.8, 23.5.
1-(4-Chlorophenyl)ethan-1-ol (7i)43. The title compound
was purified by silica gel chromatography (hexane/ethyl
acetate, 85:15); Yield: 0.125 g (80%, colorless oil). 1H
NMR (400 MHz, CDCl3) δ 7.29–7.27 (d, J = 8.5 Hz, 2H),
7.24–7.22 (d, J = 8.5 Hz, 2H), 4.80 (q, J = 6.4 Hz, 1H),
3.44 (br, 1H), 1.42–1.40 (d, J = 6.4 Hz, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ 144.2, 132.9, 128.5, 126.8, 69.5, 25.1.
1-(4-Bromophenyl)ethan-1-ol (7j)43. The title compound
was purified by silica gel chromatography (hexane/ethyl
acetate, 85:15);Yield: 0.159 g (79%, colorless oil). 1H
NMR (400 MHz, CDCl3) δ 7.47–7.45 (d, J = 8.4 Hz, 2H),
7.22–7.20 (d, J = 8.3 Hz, 2H), 4.83 (q, J = 6.4 Hz, 1H),
2.63 (br, 1H), 1.45–1.43 (d, J = 6.5 Hz, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ 144.7, 131.5, 127.1, 121.1, 69.6, 25.2.
4-(1-Hydroxyethyl)benzonitrile (7k)49. The title compound
was purified by silica gel chromatography (hexane/ethyl
acetate, 90:10); Yield: 0.100 g (68%, colorless oil). 1H
NMR (400 MHz, CDCl3) δ 7.59–7.57 (d, J = 8.3 Hz, 2H),
7.47–7.45 (d, J = 8.1 Hz, 2H), 4.94 (q, J = 6.5 Hz, 1H),
3.03 (br, 1H), 1.46–1.45 (d, J = 6.5 Hz, 3H). 13C{1H} NMR
by silica gel chromatography (hexane/ethyl acetate, 85:15);
1
Yield: 0.115 g (94%, colorless oil). H NMR (400 MHz,
CDCl3) δ 7.39–7.38 (m, 4H), 7.32–7.29 (m, 1H), 4.92 (q, J
= 6.4 Hz, 1H), 2.21 (br, 1H), 1.52–1.51 (d, J = 6.4 Hz, 3H).
13C{1H} NMR (100 MHz, CDCl3) δ 145.8, 128.5, 127.4,
125.4, 70.3, 25.1.
1-(o-Tolyl)ethan-1-ol (7b)43. The title compound was
purified by silica gel chromatography (hexane/ethyl
1
acetate, 85:15); Yield: 0.113 g (83%, colorless oil). H
NMR (400 MHz, CDCl3) δ 7.54–7.53 (d, J = 8.0 Hz, 1H),
7.27 (t, J = 8.0 Hz, 1H), 7.23–7.16 (m, 2H), 5.15 (q, J = 6.4
Hz, 1H), 2.37 (s, 3H), 2.27 (br, 1H), 1.49–1.48 (d, J = 6.4
Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 143.8, 134.2,
130.3, 127.1, 126.3, 124.5, 66.8, 23.9, 18.9.
1-(p-Tolyl)ethan-1-ol (7c)43. The title compound was
purified by silica gel chromatography (hexane/ethyl
1
acetate, 90:10); Yield: 0.114 g (84%, colorless oil). H
NMR (400 MHz, CDCl3) δ 7.31–7.29 (d, J = 8.0 Hz, 2H),
7.22–7.20 (d, J = 8.0 Hz, 2H), 4.87 (q, J = 6.4 Hz, 1H),
3.09 (br, 1H), 2.42 (s, 3H), 1.52–1.50 (d, J = 6.4 Hz, 3H).
13C{1H} NMR (100 MHz, CDCl3) δ 143.0, 136.9, 129.1,
125.4, 70.0, 25.1, 21.1.
1-(4-Methoxyphenyl)ethan-1-ol (7d)43. The title compound
was purified by silica gel chromatography (hexane/ethyl
1
acetate, 90:10); Yield: 0.119 g (78%, colorless oil). H
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The Journal of Organic Chemistry
(100 MHz, CDCl3) δ 151.4, 132.2, 126.1, 118.9, 110.6,
69.4, 25.2.
3H), 1.24 (s, 17H), 1.17–1.15 (d, J = 6.2 Hz, 3H), 0.86 (t, J
= 6.8 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 68.1,
1
2
3
4
5
6
7
8
39.3, 31.9, 29.6, 29.6, 29.6, 29.3, 25.7, 23.4, 22.6, 14.0.
1-(4-(Methylthio)phenyl)ethanol (7s)43. The title compound
Methyl 4-(1-hydroxyethyl)benzoate (7l)43. The title
compound was purified by silica gel chromatography
(hexane/ethyl acetate, 85:15); Yield: 0.132 g (73%,
was purified by silica gel chromatography (hexane/ethyl
1
1
colorless oil). H NMR (400 MHz, CDCl3) δ 7.94–7.92 (d,
acetate, 85:15); Yield: 0.138 g (82%, colorless oil). H
J = 8.3 Hz, 2H), 7.38–7.36 (d, J = 8.3 Hz, 2H), 4.90 (q, J =
6.4 Hz, 1H), 3.86 (s, 3H), 3.22 (br, 1H), 1.45–1.43 (d, J =
6.5 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 167.1,
151.2, 129.7, 128.8, 125.3, 69.7, 52.0, 25.1.
NMR (400 MHz, CDCl3) δ 7.23–7.21 (m, 4H), 4.80 (q, J =
6.4 Hz, 1H), 2.98 (br, 1H), 2.46 (s, 3H), 1.43–1.42 (d, J =
5.6 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 142.9,
137.1, 126.7, 126.0, 69.7, 25.1, 15.9.
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6,7,8,9-Tetrahydro-5H-benzo[7]annulen-5-ol (7m)43. The
title compound was purified by silica gel chromatography
(hexane/ethyl acetate, 85:15); Yield: 0.115 g (71%, white
solid). 1H NMR (400 MHz, CDCl3) δ 7.47–7.45 (d, J = 7.6
Hz, 1H), 7.28–7.11 (m, 3H), 4.97–4.95 (d, J = 6.7 Hz, 1H),
2.98–2.92 (m, 1H), 2.75 (t, J = 7.7 Hz), 2.09–1.96 (m, 2H),
1.86–1.78 (m, 3H), 1.62 (br, 1H), 1.54–1.47 (m, 1H).
13C{1H} NMR (100 MHz, CDCl3) δ 144.2, 140.8, 129.5,
127.0, 126.1, 124.6, 74.0, 36.6, 35.7, 27.7, 27.6.
1-(Pyridin-2-yl)ethanol (7n)47. The title compound was
purified by silica gel chromatography (hexane/ethyl
acetate, 80:20); Yield: 0.80 g (65%, colorless oil). 1H NMR
(400 MHz, CDCl3) δ 8.48–8.47 (d, J = 6.1 Hz, 1H), 7.68–
7.64 (m, 1H), 7.31–7.29 (d, J = 8.0 Hz, 1H), 7.18–7.15 (dd,
J = 7.3, 5.0 Hz, 1H), 4.90 (q, J = 6.5 Hz, 1H), 4.34 (br,
1H), 1.49–1.47 (d, J = 6.5 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 163.3, 148.0, 136.8, 122.2, 119.8, 69.0,
24.1.
General Procedure for Intermolecular Chemoselective
Hydroboration. Ketone (1.0 mmol), another competitor
substrate (1.0 mmol), HBpin (1.1 mmol), 0.2 mol% of
catalyst 3 were charged in an air-tight vial with a magnetic
bead inside the glove box. The resultant mixture was stirred
at ambient temperature, and the reaction progress was
monitored by 1H NMR. The completion of the reaction was
indicated by the appearance of a new -CH- resonance.
ASSOCIATED CONTENT
Detailed optimizations, NMR spectra of the products, and
crystallographic data and structure refinement summary
(PDF).
Crystallographic information files (CIF)
AUTHOR INFORMATION
1-(Benzofuran-2-yl)ethanol (7o)43. The title compound was
Corresponding Author
purified by silica gel chromatography (hexane/ethyl
*E-mail: snembenna@niser.ac.in. Tel: 0091-6742494174.
ORCID
1
acetate, 85:15); Yield: 0.118 g (73%, colorless oil). H
NMR (400 MHz, CDCl3) δ 7.57–7.55 (m, 1H), 7.50–7.48
(d, J = 8.0 Hz, 1H), 7.30–7.25 (m, 2H), 6.61 (s, 1H), 5.04
(q, J = 6.5 Hz, 1H), 2.68 (br, 1H), 1.66–1.64 (d, J = 6.4 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ 160.3, 154.8,
128.2, 124.1, 122.7, 121.1, 111.2, 101.8, 64.1, 21.4.
Sharanappa Nembenna: 0000-0001-8856-4561
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
1-(Napthalen-1-yl)ethanol (7p)47. The title compound was
The authors thank the National Institute of Science Education and
Research (NISER), HBNI, Bhubaneswar, Department of Atomic
Energy (DAE), Govt. of India.
purified by silica gel chromatography (hexane/ethyl
1
acetate, 85:15); Yield: 0.156 g (88%, colorless oil). H
NMR (400 MHz, CDCl3) δ 8.11–8.08 (m, 1H), 7.94–7.92
(m, 1H), 7.83–7.81 (d, J = 8.0 Hz, 1H), 7.70–7.68 (d, J =
8.0 Hz, 1H), 7.57–7.48 (m, 3H), 5.62 (q, J = 6.3 Hz, 1H),
3.12 (br, 1H), 1.67–1.66 (d, J = 6.4 Hz, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ 141.5, 133.8, 130.3, 128.9, 127.8,
126.0, 125.6, 125.5, 123.3, 122.1, 66.9, 24.4.
DEDICATION
Dedicated to Prof. Bharati V. Badami, Department of Chemistry,
Karnatak University Dharwad for her excellent teaching and
training to many chemists.
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