Iridium-catalyzed hydroboration of alkenes with pinacolborane

Article abstract of DOI:10.1016/j.tet.2004.09.014

Hydroboration of terminal and internal alkenes with pinacolborane (1.2 equiv) was carried out at room temperature in the presence of an iridium(I) catalyst (3 mol%). Addition of dppm (2 equiv) to [Ir(cod)Cl]₂ gave the best catalyst for hydroboration of aliphatic terminal and internal alkenes at room temperature, resulting in addition of the boron atom to the terminal carbon of 1-alkenes with more than 99% selectivities. On the other hand, a complex prepared from dppe (2 equiv) and [Ir(cod)Cl]₂ resulted in the best yields for vinylarenes such as styrene. These complexes exhibited higher levels of catalyst activity and selectivity than those of corresponding rhodium complexes. Graphical Abstract.

Full text of DOI:10.1016/j.tet.2004.09.014

Tetrahedron 60 (2004) 10695–10700
Iridium-catalyzed hydroboration of alkenes with pinacolborane
*
Yasunori Yamamoto, Rhyou Fujikawa, Tomokazu Umemoto and Norio Miyaura
Division of Molecular Chemistry, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Received 30 July 2004; accepted 1 September 2004
Available online 28 September 2004
Abstract—Hydroboration of terminal and internal alkenes with pinacolborane (1.2 equiv) was carried out at room temperature in the
presence of an iridium(I) catalyst (3 mol%). Addition of dppm (2 equiv) to [Ir(cod)Cl]2 gave the best catalyst for hydroboration of aliphatic
terminal and internal alkenes at room temperature, resulting in addition of the boron atom to the terminal carbon of 1-alkenes with more than
99% selectivities. On the other hand, a complex prepared from dppe (2 equiv) and [Ir(cod)Cl]2 resulted in the best yields for vinylarenes such
as styrene. These complexes exhibited higher levels of catalyst activity and selectivity than those of corresponding rhodium complexes.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
Catecholborane has been used in most of the reactions
studied, but pinacolborane has recently been found to be an
excellent alternative because it is a more stable and an easily
prepared and stored hydroboration reagent. The high
stability of the resulting pinacol organoboronates to
moisture and chromatography is also convenient for
isolation and handling. Much bulkier pinacolborane
increases the terminal selectivity for styrene due to its
steric hindrance. For example, the hydroboration of styrene
with pinacolborane in the presence of RhCl(PPh3)3 yields a
mixture of 2/3Z41/59, and Rh(CO)(PPh3)2Cl and
CpNi(PPh3)Cl selectively afford a terminal product (2O
99%).13 In contrast to such alterable selectivity for
vinylarenes depending upon metal catalysts and hydrobora-
tion reagents, the boron atom is selectively added to the
terminal carbon of aliphatic 1-alkenes. Representative metal
Hydroboration of alkenes and alkynes is the most
convenient method for preparation of alkyl- and
1-alkenylboron compounds. Since most H-B reagents can
be added to double or triple C–C bonds without any
assistance of catalysts,1 catalyzed hydroboration did not
¨
¨
attract much attention until Mannig and Noth reported in
1985 that the Wilkinson complex [RhCl(PPh3)3] catalyzes
the addition of catecholborane to alkenes and alkynes at
room temperature.2 Subsequent extensive works revealed
that the catalyzed hydroboration is a more interesting
strategy for accelerating the slow reaction with (dialkoxy)-
boranes, such as catecholborane3 and pinacolborane,4 and
for achieving the different chemo-, regio-, diastereo- and
enantioselectivities, relative to the uncatalyzed reaction.5
Among them, RhCl(PPh3)3 is the most-extensively studied
catalyst for hydroboration of alkenes with catecholborane,
which provides an internal hydroboration product (3) for
styrene with selectivity exceeding 99%.6 Such a high
internal selectivity characteristic for rhodium catalysts and
vinylarenes system is accounted for by a catalytic cycle
proceeding through a p-benzylrhodium intermediate.7
Thus, [RhCl(cod)]2/4PPh3,8 Rh(h3-2-methallyl)(dppb),7
complexes such as Rh(PPh3)3Cl,14 [Rh(nbd)(dppb)]BF4,14
Cp*Sm(THF),12 SmI3
and Cp2ZrHCl16 have been
15
reported to yield terminal products (2) for both catechol-
borane and pinacolborane. Thus, selectivity and activity of
representative metal catalysts have been studied exten-
sively; however, there is little information on the corre-
sponding iridium complexes.9,14b We report here that
neutral iridium(I)–phosphine complexes such as
[Ir(cod)Cl]2/2dppm and [Ir(cod)Cl]2/2dppe are excellent
catalysts for hydroboration of terminal and internal alkenes
possessing an aliphatic or aromatic substituent on the
vinylic carbon with pinacolborane (Eq. 1). Most catalysts
employed were prepared in situ from an air-stable
cyclooctadiene complex and a phosphine ligand since
previous studies using air-sensitive RhCl(PPh3)3 has
resulted in different regioselectivities between complexes
handled under argon and air.17
[Rh(cod)2]BF4/2PPh3 and [Rh(cod)2]BF4/dppb6 selec-
6
tively gave an internal product (3), whereas other metal
complexes such as [Cp*IrCl2]2,9 RuCl2(PPh3)4,10 Cp2-
TiMe2,11 and Cp*Sm12 afforded terminal hydroboration
products (2) for styrene.
Keywords: Hydroboration; Pinacolborane; Iridium; Rhodium.
* Corresponding author. Tel./fax: C81 11 706 6561;
e-mail: miyaura@org-mc.eng.hokudai.ac.jp
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.09.014

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Y. Yamamoto et al. / Tetrahedron 60 (2004) 10695–10700
mixture of 2, 3 and 4 or a mixture of 2 and 4 for styrene
(entries 1 and 3–10). Iridium complexes have rarely been
used as catalysts for hydroboration, but they are catalysts
that show a high terminal selectivity in hydroboration of
styrene with catecholborane.9,14b Indeed, most neutral and
cationic iridium–phosphine complexes mainly afforded a
terminal boron product (2) also for pinacolborane (entries
12–24). Among them, a combination of [IrCl(cod)]2 and
dppe, dppp or dppb was recognized to be the best catalyst
for achieving high yields and high selectivities (entries
13–15). Analogous catalysts prepared from a cationic
iridium(I) precursor also predominated the formation of 2,
but they were less selective than were neutral complexes
(entries 17–24).
(1)
2. Results and discussion
2.1. Iridium-catalyzed hydroboration of alkenes
Effects of rhodium and iridium catalysts on hydroboration
of 1-octene with pinacolborane are summarized in Table 2.
Various neutral and cationic rhodium(I) complexes are
Table 1. Hydroboration of styrene with pinacolboranea
Entry
Catalyst
RhCl(PPh3)3
Rh(CO)(PPh3)2Cl
[Rh(cod)Cl]2
1/2[Rh(cod)Cl]2/dppm
1/2[Rh(cod)Cl]2/dppe
1/2[Rh(cod)Cl]2/dppp
[Rh(cod)2]BF4
[Rh(cod)2]BF4/dppm
[Rh(cod)2]BF4/dppe
[Rh(cod)2]BF4/dppb
[Ir(cod)Cl]2
1/2[Ir(cod)Cl]2/dppm
1/2[Ir(cod)Cl]2/dppe
1/2[Ir(cod)Cl]2/dppp
1/2[Ir(cod)Cl]2/dppb
[Ir(cod)2]PF6
[Ir(cod)2(PPh3)2]PF6
[Ir(cod)2(PMePh2)2]PF6
[Ir(cod)2]PF6/2PCy3
[Ir(cod)2]PF6/2PtBu3
[Ir(cod)]PF6/dppm
[Ir(cod)2]PF6/dppe
[Ir(cod)2]PF6/dppp
[Ir(cod)2]PF6/dppb
Yield/%b
2
3
4
1
2
3
4
5
6
7
8
26
76
48
74
67
68
28
73
79
51
80
66
93
97
94
19
26
63
63
46
63
12
26
25
66
94
75
29
50
44
42
38
37
39
62
99
100
100
98
67
76
100
94
80
96
24
60
67
34
0
2
4
6
23
24
13
0
26
20
7
30
30
1
0
0
2
22
12
0
6
13
4
47
37
56
32
42
56
31
8
0
0
0
0
11
12
0
0
7
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
0
41
13
12
35
27
21
a A mixture of styrene (1 mmol), pinacolborane (1.2 mmol), catalyst (0.03 mmol based on the metals) in toluene was stirred for 24 h at room temperature.
b Isolated yields by chromatography.
effective for catalyzing hydroboration of styrene and other
Table 2. Hydroboration of 1-octene with pinacolboranea
arylethenes with catecholborane (HBcat) at room tempera-
Entry
Catalyst
Yield/%b
ture. The reaction selectively provides an internal hydro-
boration product (3) when
RhCl(PPh3)3,8,17
RhCl(CO)(PPh3)2
and [Rh(cod)2]BF4/dppb6 are used.
1
2
3
4
5
6
7
8
RhCl(PPh3)3
18
63
56
71
82
50
78
89
86
53
78
4,13
Rh(CO)(PPh3)2Cl
1/2[Rh(cod)Cl]2/dppm
1/2[Rh(cod)Cl]2/dppe
1/2[Rh(cod)Cl]2/dppp
[Ir(cod)Cl]2
1/2[Ir(cod)Cl]2/3PCy3
1/2[Ir(cod)Cl]2/dppm
1/2[Ir(cod)Cl]2/dppe
1/2[Ir(cod)Cl]2/dppp
1/2[Ir(cod)Cl]2/dppb
The formation of dehydrogenative coupling products (4) has
been reported in the hydroboration of arylethenes with
phosphine-free catalysts such as [RhCl(p-MeOC6H4-
18
CH]CH2)2]2 and [RhCl(cod)]2.19 Among the repre-
sentative rhodium catalysts screened for styrene,
pinacolborane (HBpin) showed a high terminal selectivity,
giving 2 in the presence of RhCl(CO)(PPh3)2 (Table 1, entry
2).13 This regioselectivity is completely opposite to that of
catecholborane, which selectively provided 3 in the
presence of RhCl(PPh3)3, [Rh(cod)2]BF4/2PPh3 or
[Rh(cod)2]BF4/dppb.6,8,17 Other neutral and cationic rho-
dium complexes effective for catecholborane5 resulted in a
9
10
11
a A mixture of 1-octene (1 mmol), pinacolborane (1.2 mmol), and catalyst
(0.03 mmol based on the metals) in CH2Cl2 was stirred for 24 h at room
temperature.
b Isolated yields of 2 by chromatography on silica gel. Formations of 3 and
4 were not observed.

Y. Yamamoto et al. / Tetrahedron 60 (2004) 10695–10700
Table 3. Iridium-catalyzed hydroboration of terminal alkenes with pinacolboranea
10697
Entry
Alkene
CH3(CH2)5CH]CH2
CH3C(]O)CH2CH2CH]CH2
BrCH2CH2CH]CH2
PhOCH2CH]CH2
NCCH2CH]CH2
Product no.
Yield/%b dppm
Yield/%b dppe
1
2
3
4
6
7
9
10
11
12
13
2a
2b
2c
2d
2e
2f
2g
2h
2i
89
68
77
89
15
66
76
77
60
84
21
—
—
—
—
—
93
80
99
82
91
—
PhCH]CH2
4-CH3OC6H4CH]CH2
4-CH3C6H4CH]CH2
C6F5CH]CH2
2-NaphthylCH]CH2
4-PyridylCH]CH2
2j
2k
a Alkene (1 mmol) and pinacolborane (1.2 mmol) were added to a solution of [Ir(cod)Cl]2 (0.015 mmol) and dppm or dppe (0.03 mmol) in CH2Cl2. The
resulting mixture was stirred for 24 h at room temperature.
b Isolated yields of the terminal addition products (2) by Kugelrohr distillation or by chromatography over silica gel. The internal addition product (3) and the
dehydrogenative coupling product (4) were less than 0.6% in each reactions.
In contrast to styrene, which was more prone to yield
internal addition products (3) or dehydrogenative coupling
products (4), all rhodium(I) and iridium(I) catalysts
selectively provided a terminal hydroboration product (2)
for 1-octene without accompanying 3 or 4. Addition of dppp
(2 equiv to [Rh(cod)Cl]2) afforded the best rhodium
catalyst, giving 2 (RZn-C6H13) in 82% yield (entry 5).
Among the iridium complexes examined, [Ir(cod)Cl]2 and
dppm or dppe was recognized to be the best combination for
obtaining 2, with yields of 89 and 86%, respectively (entries
8 and 9).
(2)
Iridium-catalyzed hydroboration of representative terminal
Iridium(I)-catalyzed hydroboration of internal alkenes with
alkenes are summarized in Table 3. Since pinacol
alkylboronates are thermally stable and insensitive to silica
gel, they were easily isolated by chromatography or
Kugelrohr distillation. Addition of dppm to [IrCl(cod)]2
worked well for aliphatic terminal alkenes, whereas dppe
was a better ligand than dppm for aromatic alkenes (entries
7–12). However, both catalysts failed to catalyze hydro-
boration of nitrile and pyridine derivatives in high yields
due to their strong coordination ability to the metal
catalysts (entries 6 and 13). It has been reported that
hydroboration of the terminal double bond of 1-hexen-5-one
with catecholborane is much faster than reduction of the
carbonyl group in the presence of RhCl(PPh3)3; thus
giving hydroboration product (2) and 1-hexen-5-ol in a
ratio of 83/17.3 Such a carbonyl group also remained
perfectly intact in the iridium-catalyzed hydroboration with
pinacolborane (entry 2). All aliphatic and aromatic terminal
alkenes selectively gave terminal products (2) even for
pentafluorophenylethene (entry 11). Pentafluorophenyl-
ethene, which is inert to uncatalyzed hydroboration with
9-BBN or HBSia2 (SiaZ1,2-dimethylpropyl), has
previously been hydroborated with catecholborane in the
presence of RhCl(PPh3)3 (Eq. 2). Catecholborane predomi-
nantly afforded the internal product (5/6Z79/21), and
bulkier pinacolborane effected to further increase the
terminal product in a ratio of 5/6Z29/71.20 Thus, both
iridium(I)–dppm and –dppe complexes shown in entry 11
were found to be the best catalysts for obtaining a perfect
anti-Markovnikov addition product.
pinacolborane is shown in Table 4. Hydroboration of both
(E)- and (Z)-4-octene resulted in the formation of pinacol
1-alkylboronates (entries 1 and 2). The corresponding
reaction of (Z)-2-butene and (Z)-1-phenylpropene also
resulted in isomerization to the terminal carbon (entries 3
and 4). Such isomerization to the terminal carbon, which is
popular in catalyzed hydrometallation of internal alkenes, is
greatly dependent on catalysts and borane reagents
Table 4. Iridium-catalyzed hydroboration of internal alkenes with
pinacolboranea
Entry
Alkene
Product
no.
Yield/%b
1
2
3
4
5
6
7
8
9
(E)-4-Octene
(Z)-4-Octene
(Z)-CH3CH]CHCH3
(Z)-PhCH]CHCH3
Cyclohexene
2a
2a
2l
2m
2n
2o
2p
2q
2r
77c
78c
65d
75e
74
Norbornene
66f
1-t-Butyl-4-methylenecyclohexane
t-BuMe2SiOCH2C(CH3)]CH2
2-Methy-2-butene
97
73
5 (36)g
a A mixture of alkene (1 mmol), pinacolborane (1.2 mmol), [Ir(cod)Cl]2 (0.
015 mmol) and dppm (0.03 mmol) in CH2Cl2 was stirred for 24 h at room
temperature.
b Isolated yields.
c Pinacol 1-octylboronate.
d Pinacol 1-butylboronate. dppb (0.03 mmol) was used in place of dppm.
e Pinacol 3-phenylpropylboronate.
f
exo Isomer was selectively given.
g [Ir(cod)Cl]2 (0.015 mmol) was used in the absence of phosphine ligand.

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Y. Yamamoto et al. / Tetrahedron 60 (2004) 10695–10700
employed. It has been reported that such isomerization is
slow in hydroboration with catecholborane using a neutral
or cationic rhodium(I) catalyst17 and that the use of much
bulkier pinacolborane is more prone to afford the isomerized
pinacol 1-alkylboronates13,16 (Eq. 3). The reaction also took
place smoothly for cyclic alkenes such as cyclohexene and
norbornene (entries 5 and 6) and for 1,1-disubstituted
alkenes (entries 7 and 8). Hydroboration of trisubstituted
alkenes such as 2-methyl-2-butene was very slow as was
reported in related metal-catalyzed hydroboration. All
attempts at finding a practical catalyst for trisubstituted
alkenes failed, though a phosphine-free [IrCl(cod)]2
exhibited a higher level of catalyst activity than that of
phosphine complexes (entry 9).
The spectral data of compounds synthesized in Tables 3 and
4 are followed.
3.2.1. 2-Octyl-4,4,5,5-tetramethyl-[1,3,2]-dioxaborolane
1
(2a). H NMR (400 MHz, CDCl3) d 0.77 (t, JZ7.8 Hz,
2H), 0.87 (t, JZ6.8 Hz, 3H), 1.24 (s, 12H), 1.21–1.29 (m,
10H), 1.38–1.41 (m, 2H); 13C NMR (100 MHz, CDCl3) d
14.1, 22.7, 24.0, 24.8, 29.2, 29.4, 31.9, 32.4, 82.8; MS (EI)
m/z 41 (81), 59 (58), 69 (50), 85 (82), 129 (100), 183 (10),
225 (52), 240 (3); HRMS calcd for C14H29BO2; 240.2261,
found: 240.2265.
3.2.2. 2-(5-Oxohexyl)-4,4,5,5-tetramethyl-[1,3,2]-dioxa-
borolane (2b). H NMR (400 MHz, CDCl3) d 0.78 (t, 2H,
1
JZ7.8 Hz), 1.24 (s, 12H), 1.30–1.45 (m, 2H), 1.54–1.62 (m,
2H), 2.13 (s, 3H), 2.42 (t, 2H, JZ7.4 Hz); 13C NMR
(100 MHz, CDCl3) d 23.5, 24.7, 26.3, 29.6, 43.5, 82.8,
209.1; MS (EI) m/z 43 (100), 55 (39), 69 (15), 83 (25), 111
(12), 168 (9), 211 (1), 241 (0.2); HRMS calcd for
C12H23BO3; 226.1740, found: 226.1750.
3.2.3. 2-(4-Bromobutyl)-4,4,5,5-tetramethyl-[1,3,2]-
dioxaborolane (2c). H NMR (400 MHz, CDCl3) d 0.80
1
(t, 2H, JZ7.8 Hz), 1.25 (s, 12H), 1.55 (tt, JZ7.5, 7.8 Hz,
2H), 1.87 (tt, JZ6.8, 7.5 Hz, 2H), 3.40 (t, JZ6.8 Hz, 2H);
13C NMR (100 MHz, CDCl3) d 22.7, 24.8, 33.6, 35.3, 83.0;
MS (EI) m/z 41 (85), 55 (66), 69 (42), 83 (100), 96 (25), 129
(34), 163 (19), 183 (66), 247 (27), 262 (0.8); HRMS calcd
for C10H20BBrO2; 262.0740, found: 262.0729.
(3)
3.2.4. 2-(3-Phenoxypropyl)-4,4,5,5-tetramethyl-[1,3,2]-
dioxaborolane (2d). H NMR (400 MHz, CDCl3) d 0.92
1
(t, JZ7.8 Hz, 2H), 1.28 (s, 12H), 1.90 (tt, JZ6.7, 7.8 Hz,
2H), 3.95 (t, JZ6.7 Hz, 2H), 6.89–6.93 (m, 3H), 7.24–7.28
(m, 2H); 13C NMR (100 MHz, CDCl3) d 23.7, 24.8, 69.4,
83.0, 114.5, 120.3, 129.3, 159.1; MS (EI) m/z 41 (49), 57
(38), 69 (24), 83 (41), 94 (100), 101 (28), 119 (19) 169 (16),
189 (33), 262 (17); HRMS calcd for C15H23BO3; 262.1740,
found: 262.1738.
3. Experimental
3.1. Reagents
Pinacolborane purchased from Aldrich was purified by
distillation before use or it can be synthesized from
BH3$SMe2 (BMS) and pinacol.4 RhCl(PPh3)3,21
Rh(CO)(PPh3)2Cl,22 [RhCl(cod)]2,23 [Rh(cod)2]BF4,24,26
3.2.5. 2-(3-Cyanopropyl)-4,4,5,5-tetramethyl-[1,3,2]-
dioxaborolane (2e). H NMR (400 MHz, CDCl3) d 0.94
[IrCl(cod)]2,25 [Ir(cod)2]PF6,24,26 [Ir(cod)(PPh3)2]PF6, and
1
24,27
[Ir(cod)(PMePh2)2]PF6
were prepared by the reported
(t, JZ7.8 Hz, 2H), 1.24 (s, 12H), 1.78 (tt, JZ7.2, 7.8 Hz,
2H), 2.37 (t, JZ7.2 Hz, 2H); 13C NMR (100 MHz, CDCl3)
d 20.3, 24.5, 24.8, 83.3, 129.0; MS (EI) m/z 43 (100), 59
(72), 68 (36), 85 (78), 96 (81), 109 (15), 137 (19), 180 (64),
194 (4); HRMS calcd for C10H18BNO2; 195.1431, found:
195.1429.
procedures. All phosphine ligands of dppm (Ph2PCH2PPh2),
dppe (Ph2PCH2CH2PPh2), dppp (Ph2PCH2CH2CH2PPh2),
dppb (Ph2P(CH2)4PPh2), PCy3 (CyZcyclohexyl), and
P(t-Bu)3 were commercially available.
3.2. Iridium-catalyzed hydroboration of alkenes
(Tables 3 and 4)
3.2.6. 2-(2-Phenylethyl)-4,4,5,5-tetramethyl-[1,3,2]-
dioxaborolane (2f). H NMR (400 MHz, CDCl3) d 1.14
1
(t, JZ8.1 Hz, 2H), 1.22 (s, 12H), 2.75 (t, JZ8.1 Hz, 2H),
7.13–7.28 (m, 5H); 13C NMR (100 MHz, CDCl3) d 24.8,
29.9, 83.1, 125.5, 128.0, 128.1, 144.4; MS (EI) m/z 41 (72),
59 (33), 69 (19), 84 (100), 91 (82), 105 (40) 132 (38), 175
(17), 232 (6); HRMS calcd for C14H21BO2; 232.1635,
found: 232.1649.
The catalytic hydroboration of alkenes with pinacolborane
was carried out by the following general procedure. A
round-bottom flask charged with [Ir(cod)Cl]2 (0.015 mmol,
1.5 mol%) and dppm or dppe (0.03 mmol) was flushed with
argon. CH2Cl2 (3 ml), pinacolborane (1.2 mmol), and
alkene (1.0 mmol) were added successively at room
temperature. The mixture was then stirred at room
temperature for the period shown in Tables 3 and 4. The
reaction was quenched with methanol (1 ml) and water
(3 ml), the product was extracted with ether, and dried over
MgSO4. Chromatography on silica gel with CH2Cl2 gave a
pinacol 1-alkylboronate.
3.2.7. 2-(2-(4-Methoxyphenyl)ethyl)-4,4,5,5-tetramethyl-
[1,3,2]-dioxaborolane (2g). 1H NMR (400 MHz, CDCl3) d
1.11 (t, JZ8.1 Hz, 2H), 1.22 (s, 12H), 2.69 (t, JZ8.1 Hz,
2H), 3.78 (s, 3H), 6.79–6.82 (m, 2H), 7.12–7.18 (m, 2H);
13C NMR (100 MHz, CDCl3) d 24.8, 29.0, 55.2, 83.0, 113.5,

Y. Yamamoto et al. / Tetrahedron 60 (2004) 10695–10700
10699
128.8, 136.5, 157.5; MS (EI) m/z 41 (53), 59 (15), 69 (10),
84 (45), 91 (15), 121 (100) 134 (46), 161 (11), 262 (14);
HRMS calcd for C15H23BO3; 262.1740, found: 262.1718.
82.7; MS (EI) m/z 43 (23), 69 (44), 82 (30), 85 (26), 110
(30), 124 (100), 129 (23), 195 (38); HRMS calcd for
C12H23BO2; 210.1791, found: 210.1773.
3.2.8. 2-(2-(4-Methylphenyl)ethyl)-4,4,5,5-tetramethyl-
[1,3,2]-dioxaborolane (2h). H NMR (400 MHz, CDCl3)
3.2.15. (exo)-2-(Bicyclo-[2,2,1]-hept-2-yl)-4,4,5,5-tetra-
methyl-[1,3,2]-dioxaborolane (2o). H NMR (400 MHz,
1
1
d 1.12 (t, JZ8.1 Hz, 2H), 1.23 (s, 12H), 2.30 (s, 3H), 2.70 (t,
JZ8.1 Hz, 2H), 7.05–7.12 (m, 4H); 13C NMR (100 MHz,
CDCl3) d 20.9, 24.8, 29.4, 83.0, 127.8, 128.8, 134.8, 141.3;
MS (EI) m/z 41 (67), 59 (21), 69 (16), 84 (100), 105 (63),
118 (23), 146 (16), 189 (6), 246 (9); HRMS calcd for
C15H23BO2; 246.1791, found: 246.1781.
CDCl3) d 0.87–0.94 (m, 1H), 1.23 (s, 12H), 1.14–1.40 (m,
4H), 1.42–1.68 (m, 4H), 2.22–2.29 (m, 2H); 13C NMR
(100 MHz, CDCl3) d 24.7, 29.3, 32.2, 32.2, 36.6, 38.1, 38.7,
82.8; MS (EI) m/z 41 (100), 55 (42), 67 (34), 84 (33), 108
(12), 136 (14), 207 (15), 222 (0.6); HRMS calcd for
C13H23BO2; 222.1791, found: 222.1813.
3.2.9. 2-(2-Pentafluorophenylethyl)-4,4,5,5-tetramethyl-
[1,3,2]-dioxaborolane (2i). H NMR (400 MHz, CDCl3) d
3.2.16. 2-(4-tert-Butyl-cyclohexylmethyl)-4,4,5,5-tetra-
methyl-[1,3,2]-dioxaborolane (2p). H NMR (400 MHz,
1
1
1.10 (t, JZ8.1 Hz, 2H), 1.23 (s, 12H), 2.79 (t, JZ8.1 Hz,
2H); 13C NMR (100 MHz, CDCl3) d 16.9, 24.7, 83.3, 117.1,
138.0, 138.6, 140.5, 143.7, 146.1; MS (EI) m/z 43 (100), 59
(91), 69 (21), 85 (47), 129 (28), 181 (30) 222 (23), 307 (21),
322 (6); HRMS calcd for C14H16BF5O2; 322.1164, found:
322.1185.
CDCl3) d 0.69–1.02 (m, 4H), 0.82 (s, 9H), 1.25 (s, 12H),
1.39–1.57 (m, 5H), 1.69–1.78 (m, 2H), 2.05 (br s, 1H); 13C
NMR (100 MHz, CDCl3) d 21.2, 24.8, 27.5, 28.6, 32.8,
36.3, 48.6, 82.7; MS (EI) m/z 41 (27), 57 (61), 85 (100), 87
(24), 95 (24), 101 (55), 129 (39), 167 (24), 223 (20), 265
(13), 280 (11); HRMS calcd for C17H33BO2; 280.2574,
found: 280.2584.
3.2.10. 2-(2-(2-Naphthyl)ethyl)-4,4,5,5-tetramethyl-
[1,3,2]-dioxaborolane (2j). H NMR (400 MHz, CDCl3) d
1
3.2.17.
2-[3-(tert-Butyldimethylsilyloxy)-2-methyl-
1.23 (t, JZ8.1 Hz, 2H), 1.22 (s, 12H), 2.92 (t, JZ8.1 Hz,
2H), 7.36–7.43 (m, 3H), 7.64 (s, 1H), 7.73–7.79 (m, 3H);
13C NMR (100 MHz, CDCl3) d 24.8, 30.1, 83.1, 124.9,
125.7, 125.7, 127.3, 127.4, 127.5, 127.7, 131.9, 133.6,
142.0; MS (EI) m/z 41 (50), 59 (15), 69 (14), 84 (71), 115
(37), 141 (100), 154 (69), 166 (18), 182 (18), 282 (26);
HRMS calcd for C18H23BO2; 282.1791, found: 282.1774.
propyl]-4,4,5,5-tetramethyl-[1,3,2]-dioxaborolane (2q).
1H NMR (400 MHz, CDCl3) d 0.002 (s, 6H), 0.55 (dd,
JZ8.8, 15.6 Hz, 1H), 0.82–0.85 (m, 1H), 0.86 (s, 9H), 0.87
(d, JZ6.5 Hz, 2H), 1.22 (s, 12H), 1.76–1.89 (m, 1H), 3.28
(dd, JZ7.2, 9.6 Hz, 1H), 3.40 (dd, JZ5.7, 9.6 Hz, 1H); 13C
NMR (100 MHz, CDCl3) d K5.35, 18.3, 19.0, 24.8, 26.0,
32.2, 70.0, 82.8; MS (EI) m/z 75 (24), 115 (23), 101 (11),
115 (23), 157 (100), 257 (23), 299 (2), 313 (0.2); HRMS
calcd for C12H26BO3Si (–tert-butyl); 274.1744, found:
274.1753.
3.2.11. 2-(2-(4-Prydyl)ethyl)-4,4,5,5-tetramethyl-[1,3,2]-
dioxaborolane (2k). 1H NMR (400 MHz, CDCl3) d 1.15 (t,
JZ8.1 Hz, 2H), 1.25 (s, 12H), 2.74 (t, JZ8.1 Hz, 2H),
7.11–7.16 (m, 2H), 8.42–8.58 (m, 2H); 13C NMR
(100 MHz, CDCl3) d 24.7, 29.2, 83.3, 123.5, 149.2, 153.4;
MS (EI) m/z 41 (52), 59 (59), 93 (39), 106 (29), 133 (100),
147 (40), 218 (43), 233 (50); HRMS calcd for C13H20BNO2;
233.1587, found: 233.1576.
3.2.18. 2-(1,2-Dimethyl-propyl)-4,4,5,5-tetramethyl-
[1,3,2]-dioxaborolane (2r). H NMR (400 MHz, CDCl3)
1
d 0.86 (d, JZ6.8 Hz, 6H), 0.90 (d, JZ6.6 Hz, 3H), 1.23–
1.28 (m, 1H), 1.25 (s, 12H), 1.42–4.52 (m, 1H); 13C NMR
(100 MHz, CDCl3) d 11.7, 22.2, 24.8, 32.9, 82.8; MS (EI)
m/z 41 (16), 57 (38), 69 (16), 83 (35), 87 (37), 99 (34), 129
(100), 183 (52), 198 (17); HRMS calcd for C11H23BO2;
198.1791, found: 198.1791.
3.2.12. 2-(1-Butyl)-4,4,5,5-tetramethyl-[1,3,2]-dioxa-
1
borolane (2l). H NMR (400 MHz, CDCl3) d 0.78 (t, JZ
7.7 Hz, 2H), 0.88 (t, JZ7.2 Hz, 3H), 1.25 (s, 12H), 1.27–
1.43 (m, 4H); 13C NMR (100 MHz, CDCl3) d 13.8, 24.7,
25.3, 26.1, 82.7; MS (EI) m/z 43 (16), 59 (24), 85 (50), 129
(62), 169 (100), 184 (3); HRMS calcd for C10H21BO2;
184.1635, found: 184.1638.
References and notes
3.2.13. 4,4,5,5-Tetramethyl-2-(3-phenyl-propyl)-[1,3,2]-
dioxaborolane (2m). H NMR (400 MHz, CDCl3) d 0.83
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1
(t, JZ7.8 Hz, 2H), 1.24 (s, 12H), 1.73 (tt, JZ7.8, 7.9 Hz,
2H), 2.60 (t, JZ7.9 Hz, 2H), 7.14–7.21 (m, 3H), 7.24–7.26
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82.9, 125.5, 128.1, 128.5, 142.7; MS (EI) m/z 41 (22), 59
(10), 85 (100), 91 (62), 118 (93), 127 (24), 146 (13), 173
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246.1791, found: 246.1796.
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1
¨ ¨
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