Filling the gaps in the challenging asymmetric hydroboration of 1,1-disubstituted alkenes with simple phosphite-based phosphinooxazoline iridium catalysts

Article abstract of DOI:10.1002/cctc.201402822

We have identified a readily accessible phosphinooxazoline-based phosphite-oxazoline catalytic system, (S)-4-isopropyl-2-{2-[(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite]-phenyl}-2-oxazoline (L1a), that can hydroborate a range of 1,1-disubstituted aryl olefins with high enantioselectivity (up to 94%), excellent yields and perfect regioselectivity. The new phosphite-oxazoline ligands efficiently hydroborate a broader range of olefins than previous phosphinooxazoline ligands. In particular, a wide range of α-tert-butylstyrenes can be hydroborated that bear aryl substituents with different electronic and steric properties, which complements previous results with N-heterocyclic copper catalysts, the only other system reported to date that has achieved these reactions.

Full text of DOI:10.1002/cctc.201402822

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DOI: 10.1002/cctc.201402822
Filling the Gaps in the Challenging Asymmetric
Hydroboration of 1,1-Disubstituted Alkenes with Simple
Phosphite-Based Phosphinooxazoline Iridium Catalysts
Marc Magre, Maria Biosca, Oscar Pꢀmies,* and Montserrat Diꢁguez*[a]
We have identified a readily accessible phosphinooxazoline-
based phosphite-oxazoline catalytic system, (S)-4-isopropyl-2-
{2-[(3,3’,5,5’-tetra-tert-butyl-1,1’-biphenyl-2,2’-diyl)phosphite]-
phenyl}-2-oxazoline (L1a), that can hydroborate a range of 1,1-
disubstituted aryl olefins with high enantioselectivity (up to
94%), excellent yields and perfect regioselectivity. The new
phosphite-oxazoline ligands efficiently hydroborate a broader
range of olefins than previous phosphinooxazoline ligands. In
particular, a wide range of a-tert-butylstyrenes can be hydro-
borated that bear aryl substituents with different electronic
and steric properties, which complements previous results
with N-heterocyclic copper catalysts, the only other system re-
ported to date that has achieved these reactions.
Introduction
Many of today’s pharmaceutical, fragrance and agrochemical
compounds, and the chemicals used in functional materials are
required as pure enantiomers.[1] As a result, the industrial pro-
duction of enantiopure chiral compounds is gaining impor-
tance and synthetic procedures are constantly evolving to-
wards high selectivity and productivity, atom economy, opera-
tional simplicity, cost efficiency, environmental friendliness and
low energy consumption. In comparison to other synthetic ap-
proaches, asymmetric catalysis is a smart strategy. A small
amount of catalyst can produce large quantities of the desired
chiral compound with only a few reaction steps and synthetic
operations, thus bringing down the overall production cost,
and decreasing the amount of by-products.
favour Markovnikov regioselectivity)[5] but also the face selec-
tivity coordination (due to the presence of the two relatively
similar substituents at the geminal position). To date, high
regio- and enantioselectivities have been reported in only
three publications, with limited substrate scope (Scheme 1).[6]
In 2008 Soderquist and co-workers reported the hydroboration
of 1,1-disubstituted alkenes by using stoichiometric quantities
of chiral boranes with ee values between 28 and 92%
(Scheme 1a).[6a] The highest ee was observed only with 2,3,3-
trimethylbut-1-ene.
Subsequently, two important breakthroughs in the asym-
metric hydroboration of 1,1-disubstituted olefins were reported
(Scheme 1b). They both included metal-catalyzed hydrobora-
tion processes instead of expensive and sacrificial stoichiomet-
ric chiral auxiliaries. One of them, reported by Hoveyda and
co-workers, showed the asymmetric hydroboration of 1,1-di-
substituted aryl-alkyl olefins with chiral copper-based biden-
tate N-heterocyclic carbene catalysts.[6b] A range of a-methyl-
styrenes and some aryl olefins with alkyl substituents other
than the typical methyl unit and exocyclic alkenes were hydro-
borated with high regioselectivities and enantioselectivities in
the range 61–92% ee. Despite this important advance, high
catalyst loading (7.5%), long reaction times (48 h), low temper-
ature (from À158C to À508C) and the presence of an almost
equimolar amount of base were required (Scheme 1b). Mazet
and Gꢁrard also reported the hydroboration of a range of 1,1-
disubstituted aryl-alkyl olefins with excellent yields and regio-
selectivities (with exclusive attack at the desired b position) in
which the iridium catalyst was modified with the readily acces-
sible (S)-4-tert-butyl-2-[2-(diphenylphosphino)phenyl]-2-oxazo-
line ligand (PHOX-tBu, Scheme 1b).[6c] Enantioselectivity (up to
92% ee), however, was only high in the hydroboration of a-
methylstyrene S1. The introduction of substituents at the aryl
ring or the increase in steric requirements at the alkyl substitu-
ent of the substrate decreased the enantioselectivity consider-
Chiral organoboron compounds have received a great deal
of attention lately.[2] They are valuable organic intermediates
because the CÀB bond can be readily transformed to chiral
CÀN, CÀO and CÀC bonds.[2c,3] The synthesis of these com-
pounds by transition-metal catalyzed asymmetric hydrobora-
tion is attracting considerable interest. However, whereas the
asymmetric hydroboration of monosubstituted olefins (i.e.,
styrenes) and internal 1,2-disubstituted olefins (i.e., norborna-
diene) has been well studied, the hydroboration of 1,1-disub-
stituted olefins remains a challenge.[2,4] This is because the
chiral transition metal catalyst has difficulty in controlling not
only the specific boration at the desired terminal b position
rather than at the more substituted a-position (most catalysts
[a] M. Magre, M. Biosca, Dr. O. Pꢀmies, Prof. M. Diꢁguez
Departament de Quꢂmica Fꢂsica i Inorgꢀnica
Universitat Rovira i Virgili
C/Marcel·lꢂ Domingo s/n. 43007 Tarragona (Spain)
Fax: (+34)977559563
E-mail: oscar.pamies@urv.cat
montserrat.dieguez@urv.cat
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201402822.
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L1–L4a–c in the asymmetric iri-
dium-catalyzed hydroboration of
1,1-disubstituted olefins. These
ligands incorporate the advan-
tages of biaryl phosphites such
as higher resistance to oxidation
than phosphines, facile synthesis
from readily available chiral alco-
hols and a straightforward mod-
ular construction.[9] We investi-
gated the catalytic performance
by systematically varying the
electronic and steric properties
of the oxazoline substituents
L1–L4 and using different sub-
stituents and configurations in
the biaryl phosphite group (a–c).
Scheme 1. State-of-the-art asymmetric hydroboration of challenging 1,1-disubstituted olefins. Bpin=Pinacolato.
ably. Although fewer substrates were hydroborated than with
the copper carbene-based catalysts, the PHOX iridium catalysts
allowed this transformation to take place under milder reaction
conditions and with lower catalyst loading (Scheme 1b), which
would be advantageous for sustainable industrial process.
Owing to the limited substrate scope of the three advances
Scheme 2. Synthetic route for the synthesis of new phosphite-oxazoline
PHOX-based ligands L1b and L1c.
mentioned, new developments in this field are still needed.
In most asymmetric transformations involving olefins as pro-
chiral reagents (e.g., epoxidation, hydrogenation), 1,1-disubsti-
tuted olefins are systematically challenging substrates,[7] mainly
due to face selectivity issues (as in the hydroboration reaction). Results and Discussion
We recently demonstrated the highest reported enantioselec-
Ligand synthesis
tivities in the iridium-catalyzed hydrogenation of a very large
range of simple 1,1-disubstituted olefins by introducing
a biaryl phosphite moiety into the ligand.[7c–d,8] Inspired by the
work of Mazet and Gꢁrard[6c] and the similarities of the elemen-
tary steps involved in hydroboration and hydrogenation, we
studied here whether the introduction of a biaryl phosphite
moiety into the ligand was also beneficial for iridium-catalyzed
hydroboration. To this end, we took the previously successful
PHOX ligand family and replaced the phosphine group with
biaryl phosphite moieties (ligands L1–L4a–c, Figure 1). Herein,
we present the application of the phosphite-oxazoline ligands
The new phosphite-oxazoline PHOX-based ligands L1b and
L1c can be synthesized easily by following the procedure pre-
viously described for ligands L1–L4a[10] (Scheme 2). They were
prepared in one step by coupling the oxazoline-alcohol (S)-2-
(4-isopropyl-4,5-dihydrooxazol-2-yl)phenol with one equivalent
of the in situ-formed phosphorochloridite (b–c) under basic
conditions (Scheme 2). All ligands were isolated in good yields
as white solids after purification on neutral alumina. Advanta-
geously, they were stable in air and very stable to hydrolysis,
so further manipulation and storage was performed in air. The
high-resolution electrospray ionization (ESI) mass spectra were
in agreement with the assigned structures. L1b and L1c were
1
also characterized by 31P{1H}, H and 13C{1H} NMR spectroscopy.
1
1
The spectral assignments, made by using 1HÀ H and 13CÀ H
correlation measurements, were as expected for these C1-sym-
metric ligands.
Initial screening experiments of phosphite-oxazoline PHOX-
based ligands
As previously mentioned, the effectiveness of the catalyst in
transferring the chiral information to the hydroborated product
Figure 1. Phosphite-oxazoline PHOX-based ligands L1–L4a–c.
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that ligands with an S biaryl phosphite group provid-
ed better enantioselectivities than ligands with an R
biaryl phosphite group (Table 1, entry 2 vs 3). This is
an advantage because it means that the inexpensive
3,3’,5,5’-tetra-tert-butyl-[1,1’-biphenyl]-2,2’-diyl phos-
phite moiety (a) can be used. For the oxazoline sub-
stituent, the enantioselectivities are highest with
bulky isopropyl and tert-butyl groups (ligands L1a
and L4a, Table 1, entries 1 and 6) but the activities
are best if the steric demand on the oxazoline sub-
stituents is decreased. The trade-off between activi-
ties and enantioselectivities is therefore best with
ligand L1a (Table 1, entry 1). This result contrasts
with the one described by Mazet and Gꢁrard, which
required the presence of a tert-butyl oxazoline sub-
stituent to achieve high enantioselectivity, and it has
an economic advantage because L1a is derived from
l-valinol, which is around eight times cheaper than
the l-tert-leucinol required for the synthesis of the
PHOX-tBu ligand.
Table 1. Asymmetric hydroboration of a-methylstyrene S1 and a-tert-butylstyrene
S2.[a]
Entry
L
Conv.[b] [%] (1a/2a) ee[c] [%]
Conv.[b] [%] (1b/2b) ee[c] [%]
1
2
3
4
5
6
7
L1a
L1b
L1c
L2a
L3a
L4a
100 (>99:1)
50 (>99:1)
60 (>99:1)
100 (>99:1)
100 (>99:1)
96 (>99:1)
44 (S)
7 (S)
100 (>99:1)
46 (>99:1)
59 (>99:1)
100 (>99:1)
100 (>99:1)
84 (>99:1)
0
88 (S)
43 (S)
79 (S)
86 (S)
43 (S)
88 (S)
–
41 (S)
42 (S)
17 (S)
43 (S)
92 (S)[6c]
PHOX-tBu 100 (>99:1)
[a] All reactions performed in duplicate with 1 mmol of substrate, 1.25 mol% of [Ir(m-
OMe)(cod)]2, 2.5 mol% of ligand and 2 mL of hexane. [b] Determined by using
1H NMR, in all cases regioselectivities were >99%. [c] Determined by using HPLC after
conversion to the corresponding alcohols.
Table 2. Asymmetric hydroboration of a-tert-butylstyrene S2: effect of the solvent
depends mainly on its ability to sterically differentiate
between the two geminal substituents of the olefin.
To assess the potential of the phosphite-oxazoline
PHOX-based ligands L1–L4a–c in the hydroboration
of substrates with different steric requirements, we
initially evaluated them in the asymmetric iridium-
catalyzed hydroboration of model substrate S1[2,6]
and the hydroboration of more demanding S2
(Table 1).
and catalyst precursors.[a]
Entry
Solvent
[Cat. precursor]
Conv.[b] [%] (1b/2b)
ee[c] [%]
1
2
3
4
5
6
hexane
THF
CH2Cl2
toluene
hexane
hexane
[Ir(m-OMe)(cod)]2
[Ir(m-OMe)(cod)]2
[Ir(m-OMe)(cod)]2
[Ir(m-OMe)(cod)]2
[Ir(m-Cl)(cod)]2
100 (>99:1)
88 (>99:1)
100 (>99:1)
96 (>99:1)
100 (>99:1)[d]
61 (>99:1)
88 (S)
76 (S)
80 (S)
83 (S)
92 (S)
66 (S)
For purposes of comparison, we first tested L1–
L4a–c under the same optimal reaction conditions
found in the previous study of Mazet and Gꢁrard
with related PHOX iridium catalytic systems.[6c] Reac-
tions were performed at room temperature, with
2.5 mol% of in situ-generated catalyst ([Ir(m-
OMe)(cod)]2/L) and hexane as solvent.[6c] The results
are collected in Table 1. All of the ligands favoured
the attack at the b position and the desired primary
[e]
[Ir(cod)L1a]BArF
[a] All reactions performed in duplicate with 1 mmol of substrate, 1.25 mol% of iridi-
um catalyst precursor, 2.5 mol% of ligand and 2 mL solvent. [b] Determined by using
1H NMR. [c] Determined by using HPLC after conversion to the corresponding alcohol.
[d] 91% isolated yield. [e] BArF =[B{3,5-(CF3)2C6H3}4]À.
(pinacolato)boron adduct 1 was achieved with perfect regio-
control (1/2 ratio >99). Although enantioselectivities were
moderate for a-methylstyrene S1, an unprecedentedly high
enantioselectivity was achieved for the more challenging a-
tert-butylstyrene S2 (ee values up to 88%). Notably, the hydro-
boration of S2 by using the related PHOX-tBu ligand provided
no conversion under the same reaction conditions (Table 1,
entry 7). These important results indicate that both PHOX-
based ligand families are complementary, thus, we can hydro-
borate both substrate types by the correct combination of
substrate and ligand type (phosphine/oxazoline or phosphite/
oxazoline).
We next optimized the reaction conditions by evaluating
a variety of solvents and catalyst precursors with ligand L1a,
which had provided the best results (Table 2). Although in all
cases regioselectivity towards the desired b adduct 1 remained
excellent, activity and enantioselectivity were highly depen-
dent on the solvent and the nature of the catalyst precursor.
The combination of hexane and [Ir(m-Cl)(cod)]2 (cod=1,5-cyclo-
octadiene) as catalyst precursor was found to be optimal
(Table 2, entry 5). Under these new reaction conditions we
were therefore able to increase the enantioselectivity to 92%
while maintaining the excellent yield and regioselectivity of
the desired b compound 1. To the best of our knowledge, iridi-
um–L1a is the first catalytic system that can hydroborate S2
with perfect regioselectivity, excellent yield and high enantio-
selectivity.
As far as the effect of the ligand parameters on activities
and enantioselectivities is concerned, we found that bulky tert-
butyl groups are needed at the ortho and para positions of the
biaryl phosphite moiety to achieve the highest activities and
enantioselectivities (Table 1, entry 1 vs 2 and 3). We also found
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related PHOX iridium catalysts for which the introduction of
any type of substituent at the aryl ring of the substrate had
a negative effect on enantioselectivity.[6c]
Table 3. Asymmetric hydroboration of 1,1-disubstituted olefins: scope
and limitations.[a]
We then looked into the hydroboration of aryl and trifluoro-
methyl olefins. Owing to the unique properties of the fluorine,
the efficient hydroboration of these substrates opened up an
appealing route for obtaining organic intermediates for the
preparation of drugs, agrochemicals and materials. To the best
of our knowledge, only Hoveyda and co-workers have attempt-
ed the hydroboration of this substrate class with their N-het-
erocyclic carbene copper catalysts, although they obtained un-
desired difluoroallylboronates.[6b] Here, we have tested the new
iridium–L1a and related PHOX iridium catalysts in the hydro-
boration of the model 1-methoxy-4-(3,3,3-trifluoroprop-1-en-2-
yl)benzene S11 substrate (Table 3, entries 11 and 12). Although
PHOX-tBu iridium was found to be inadequate because it pro-
vided exclusively the hydrogenated product in racemic form,
the iridium–L1a catalyst gave the desired hydroborated prod-
uct with perfect regioselectivity and good yield, albeit with
low enantiocontrol. This result opens up new possibilities for
further research and it demonstrates once again that the be-
haviour is not that observed with PHOX iridium catalysts.
Entry
Substrate R1
R2
1/2
Yield[b] [%] ee[c] [%]
1
2
3
4
5
6
7
8
S1
C6H5
Me
tBu
Et
iBu
iPr
>99:1 93
>99:1 91
>99:1 90
>99:1 88
>99:1 89
>99:1 92
>99:1 91
>99:1 94
>99:1 89
>99:1 90
>99:1 88
50 (S)
92 (S)
55 (S)
56 (S)
58 (S)
94 (S)
93 (S)
90 (S)
87 (S)
92 (S)
18 (S)
n.d.
S2
C6H5
S3
C6H5
S4
C6H5
S5
C6H5
S6
4-Me-C6H4
tBu
S7
4-OMe-C6H4 tBu
S8
S9
S10
S11
S11
4-CF3-C6H4
2-naphthyl
3-Me-C6H4
4-OMe-C6H4 CF3
4-OMe-C6H4 CF3
tBu
tBu
tBu
9
10
11
12[d]
–
0
[a] All reactions performed in duplicate with 1 mmol of substrate,
1.25 mol% of [Ir(m-Cl)(cod)]2, 2.5 mol% of L1a and 2 mL hexane. [b] De-
termined by using 1H NMR. [c] Determined by using HPLC or GC after
conversion to the corresponding alcohol. [d] Reaction performed by
using PHOX-tBu iridium catalyst; hydrogenated product isolated in 45%
yield and 0% ee.
Conclusion
Asymmetric hydroboration of other 1,1-disubstituted ole-
fins: scope and limitations
We have identified a readily accessible phosphinooxazoline
(PHOX)-based phosphite-oxazoline iridium catalytic system (iri-
dium–L1a) that can hydroborate a range of 1,1-disubstituted
aryl olefins with high enantioselectivity (up to 94%), excellent
yields and perfect regioselectivity. The new phosphite-oxazo-
line PHOX-based ligands could efficiently hydroborate a broad-
er range of olefins than previous PHOX ligands. Particularly, we
could hydroborate a wide range of a-tert-butylstyrenes, with
aryl substituents that had different electronic and steric prop-
erties, thus complementing the results of N-heterocyclic car-
bene copper catalysts, the only other system reported to date
that has attempted these reactions. In addition, the introduc-
tion of a biaryl phosphite moiety allowed, for the first time,
the highly regioselective hydroboration of aryl and trifluoro-
methyl olefins. Another advantage over previous PHOX ligands
was that the new ligands were stable to air and therefore
easier to handle, manipulate and store. This contribution
opens up the path for the synthesis of new iridium phosphite-
based catalysts for the challenging hydroboration of 1,1-disub-
stituted olefins. Further studies on the design of new phos-
phite-based iridium catalysts to further broaden the scope of
this hydroboration reaction are currently underway.
The unprecedented results obtained up to this point with the
iridium–L1a catalyst in the hydroboration of S2 encouraged us
to test iridium–L1a in the hydroboration of other 1,1-disubsti-
tuted olefins (Table 3).
First, we studied the hydroboration of several phenyl and
alkyl olefins bearing alkyl substituents with different steric de-
mands (S3–S5, Table 3, entries 3–5). Excellent regioselectivities
of the desired b adduct 1 were achieved. Enantioselectivities
were moderate regardless of the steric demands of the alkyl
substituent (entries 3–5). However, enantioselectivities were
not as low as those observed with related PHOX iridium cata-
lysts with increased steric hindrance on the alkyl substituents
(i.e., ee values decreased from 92 to 31% on replacing Me by
Et substituent).[6c]
We next studied several a-tert-butylstyrenes that had aryl
substituents with different electronic and steric properties (S6–
S10, Table 3, entries 6–10). Advantageously, iridium–L1a is very
tolerant to variations in the substituents of the aryl ring and
can hydroborate a wide range of a-tert-butylstyrenes with
comparably high enantioselectivities (up to 94%) and yields
and perfect regioselectivity. Accordingly, our results with sever-
al para-substituted a-tert-butylstyrenes (S6–S8) indicated that
the enantioselectivity was relatively insensitive to the electron-
ic effects in the aryl ring (ee values of 90–94%, entries 2, 6–8).
Enantioselectivities were, however, highest in the hydrobora-
tion of electron-rich olefins S6 and S7 (entries 6–7). Enantiose-
lectivities were also excellent in the hydroboration of meta-
substituted olefins (S9–S10, entries 9–10). Again, these results
contrasted with the ones described by Mazet and Gꢁrard with
Experimental Section
General
All reactions were performed by using standard Schlenk tech-
niques under an argon atmosphere. Solvents were purified and
dried by standard procedures. Phosphorochloridites were prepared
easily in one step from the corresponding binaphthols.[11] Inter-
mediate compound (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)phe-
nol,[12] ligands L1–L4a[10] and substrates S2,[13] S3,[14] S4,[15] S5[13]
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and S11[7c] were prepared as previously reported. Substrates S6–
S10 were prepared by using the Wittig olefination procedure (for
(SiO2, Et2O/cyclohexane=(9:1) to give the hydroborated product
as a colourless oil.
1
details, see the Supporting Information). H, 13C and 31P NMR spec-
ee Values were determined after oxidation of the pinacolborane
derivatives to the corresponding alcohols. Pinacolborane derivative
(0.25 mmol) was dissolved in Et2O (2 mL) and cooled to 08C. NaOH
(3n, 2.0 mL) and H2O2 (30%, 1.5 mL) were then added. The result-
ing solution was stirred at RT for 2 h. Then, the solution was ex-
tracted twice with Et2O (2 mL) and dried over MgSO4. The crude
product was purified by column chromatography (SiO2, Et2O/cyclo-
hexane=4:1) to yield the desired chiral primary alcohol.
tra were recorded by using a 400 MHz spectrometer. Chemical
shifts are relative to those of SiMe4 (1H and 13C) as internal standard
or H3PO4 (31P) as external standard. 1H, 13C and 31P assignments
1
1
were made on the basis of H–1H gCOSY and H–13C gHSQC NMR
analyses.
Preparation of phosphite-oxazoline ligands L1–L4a–c
4,4,5,5-Tetramethyl-2-(2-phenylpropyl)-1,3,2-dioxaborolane (1a):
1H NMR (CDCl3): d=1.08 (s, 12H, CH3, Bpin), 1.09 (m, 2H, CH2), 1.20
(d, 3JHÀH =8 Hz, 3H, CH3), 2.95 (m, 1H, CH), 7.0–7.2 ppm (m, 5H,
CH=); 13C NMR (CDCl3): d=24.6 (CH3, Bpin), 24.7 (CH3, Bpin), 24.9
(CH3), 35.8 (CH), 82.9 (C, Bpin), 125.7 (CH=), 126.6 (CH=), 128.1
(CH=), 149.2 ppm (C); HRMS elemental analysis calcd (%) for
C15H23BO2 [M+]: 246.1791, found: 246.1794.
General procedure: The corresponding phosphorochloridite
(1.1 mmol) produced in situ was dissolved in toluene (5 mL) and
pyridine (0.36 mL, 4.6 mmol) was added. Hydroxyl-oxazoline inter-
mediate (1 mmol) was azeotropically dried with toluene (3ꢃ1 mL)
and then dissolved in toluene (5 mL), to which pyridine (0.36 mL,
4.6 mmol) had been added. The hydroxyl-oxazoline solution was
transferred slowly at À788C to the solution of phosphorochloridite.
The reaction mixture was allowed to warm to RT and stirred over-
night. The pyridine salts were then removed by filtration. Evapora-
tion of the solvent gave a white foam, which was purified by flash
chromatography (Al2O3, toluene/NEt3 =100:1) to produce the cor-
responding ligand.
ee Values were determined after oxidation to phenylpropan-1-ol:
1H NMR (CDCl3): d=1.23 (d, 3JHÀH =8 Hz, 3H, CH3), 2.95 (m, 1H,
CH), 3.71 (m, 2H, CH2), 7.2–7.4 ppm (m, 5H, CH=);13C NMR (CDCl3):
d=17.5 (CH3), 42.4 (CH), 68.7 (CH2), 126.7 (CH=), 127.4 (CH=), 128.6
(CH=), 143.6 ppm (C); HRMS elemental analysis calcd (%) for
C9H12O [M+]: 136.0888, found: 136.0885; ee (HPLC, Chiracel IA
column, hexane/2-propanol=99:1, 0.5 mLminÀ1, l=254 nm): tR =
38.9 (R), 41.7 min (S).
(S)-4-isopropyl-2-{2-[(R)-3,3’-di-tert-butyl-5,5’,6,6’-tetra-methyl-
1,1’-biphenyl-2,2’-diyl)phosphite]phenyl}-2-oxazoline
(L1b):
Yield: 423 mg (72%); 31P NMR (C6D6): d=132.6 ppm (s); 1H NMR
(C6D6): d=0.62 (d, 6H, 3JHÀH =6.4 Hz, CH3, iPr), 1.27 (s, 9H, CH3,
tBu), 1.37 (s, 9H, CH3, tBu), 1.39 (m, 1H, CH, iPr), 1.61 (s, 3H, CH3),
1.68 (s, 3H, CH3), 1.93 (s, 3H, CH3), 2.03 (s, 3H, CH3), 3.03 (dd, 1H,
2-(3,3-Dimethyl-2-phenylbutyl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
1
borolane (1b): H NMR (CDCl3): d=0.83 (s, 9H, CH3, tBu), 0.91 (s,
6H, CH3, Bpin), 0.96 (s, 6H, CH3, Bpin), 1.18 (m, 2H, CH2), 2.67 (m,
1H, CH), 7.05–7.20 ppm (m, 5H, CH=); 13C NMR (CDCl3): d=24.2
(CH3, Bpin), 24.5 (CH3, Bpin), 27.7 (CH3, tBu), 34.0 (C, tBu), 51.6 (CH),
82.7 (C, Bpin), 125.6 (CH=), 127.1 (CH=), 129.7 (CH=), 144.3 ppm
(C); HRMS elemental analysis calcd (%) for C18H29BO2 [M+]:
288.2261, found: 288.2259.
3
2
2JHÀH =11.6 Hz, JHÀH =5.2 Hz, CH2ÀO), 3.12 (dd, 1H, JHÀH =11.2 Hz,
3JHÀH =5.2 Hz, CH2ÀO), 4.22 (m, 1H, CHÀN), 6.7–7.5 (m, 6H, CH=),
3
8.59 ppm (d, 1H, JHÀH =6.4 Hz, CH=); 13C NMR (C6D6): d=16.2 (CH3,
iPr), 16.4 (CH3, iPr), 17.8 (CH3), 19.1 (CH3), 19.9 (CH3), 20.0 (CH3), 28.6
(CH, iPr), 31.0 (d, CH3, tBu, JCÀP =5.3 Hz), 31.3 (CH3, tBu), 34.4 (C,
tBu), 34.8 (C, tBu), 45.3 (CH2-O), 55.4 (CH-N), 118.4–150.9 (CAr),
163.4 ppm (C=N); HRMS (ESI): m/z: calcd for C36H46NO4P+Na+:
610.3062 [MÀNa]+, found 610.3067.
ee Values were determined after oxidation to 3,3-dimethyl-2-phe-
1
nylbutan-1-ol: H NMR (CDCl3): d=0.87 (s, 9H, CH3, tBu), 2.65 (m,
1H, CH), 4.01 (m, 2H, CH2), 7.05–7.35 ppm (m, 5H, CH=); 13C NMR
(CDCl3): d=28.4 (CH3, tBu), 33.1 (C, tBu), 58.9 (CH), 62.6 (CH2), 125.6
(CH=), 126.8 (CH=), 127.1 (CH=), 128.2 (CH=), 140.2 ppm (C); HRMS
elemental analysis calcd (%) for C12H18O [M+]: 178.1358, found:
178.1357; ee (HPLC, Chiracel IA column, hexane/2-propanol=98:2,
0.5 mLminÀ1, l=220 nm): tR =23.0 (S), 25.2 min (R).
(S)-4-isopropyl-2-{2-[(S)-3,3’-di-tert-butyl-5,5’,6,6’-tetra-methyl-
1,1’-biphenyl-2,2’-diyl)phosphite]phenyl}-2-oxazoline (L1c): Yield:
376 mg (64%); 31P NMR (C6D6): d=133.9 ppm (s); 1H NMR (C6D6):
3
3
d=0.55 (d, 3H, JHÀH =6.4 Hz, CH3, iPr), 0.63 (d, 3H, JHÀH =6.8 Hz,
CH3, iPr), 1.35 (s, 9H, CH3, tBu), 1.39 (s, 9H; CH3, tBu), 1.42 (m, 1H,
CH, iPr), 1.65 (s, 3H, CH3), 1.79 (s, 3H, CH3), 1.97 (s, 3H, CH3), 2.06
(s, 3H, CH3), 3.35 (m, 2H, CH2ÀO), 4.28 (m, 1H, CHÀN), 6.7–7.7 (m,
6H, CH=), 8.60 ppm (d, 1H, 3JHÀH =8.0 Hz, 4JHÀH =2.0 Hz, CH=);
13C NMR (C6D6): d=16.2 (CH3, iPr), 16.6 (CH3, iPr), 18.1 (CH3), 19.1
4,4,5,5-Tetramethyl-2-(2-phenylbutyl)-1,3,2-dioxaborolane (1c):
1H NMR (CDCl3): d=0.73 (t, 3JHÀH =8.0 Hz, 3H, CH3), 1.08 (s, 12H,
CH3, Bpin), 1.12 (m, 2H, CH2), 1.59 (m, 2H, CH2), 2.65 (m, 1H, CH),
7.0–7.2 ppm (m, 5H, CH=); 13C NMR (CDCl3): d=12.2 (CH3), 24.6
(CH3, Bpin), 24.7 (CH3, Bpin), 35.8 (CH), 43.3 (CH2), 82.9 (C, Bpin),
125.7 (CH=), 127.4 (CH=), 128.0 (CH=), 147.2 ppm (C); HRMS ele-
mental analysis calcd (%) for C16H25BO2 [M+]: 260.1948, found:
260.1947.
(CH3), 20.0 (CH3), 21.4 (CH3), 28.6 (CH, iPr), 31.2 (d, CH3, tBu, JCÀP
=
4.6 Hz), 31.4 (CH3, tBu), 34.4 (C, tBu), 34.7 (C, tBu), 45.6 (CH2ÀO),
55.5 (CHÀN), 119.3–150.4 (CAr), 163.4 ppm (C=N); HRMS (ESI): m/z:
calcd for C36H46NO4P+Na+: 610.3062 [MÀNa]+, found 610.3068.
ee Values were determined after oxidation to 2-phenylbutan-1-ol:
3
1H NMR (CDCl3): d=0.85 (t, JHÀH =8.0 Hz, 3H, CH3), 1.5–1.8 (m, 2H,
Asymmetric hydroboration of 1,1-disubstituted substrates
CH2), 2.65 (m, 1H; CH), 3.75 (m, 2H, CH2), 7.20–7.35 ppm (m, 5H,
CH=); 13C NMR (CDCl3): d=12.5 (CH3), 25.7 (CH2), 50.5 (CH), 67.3
(CH2), 126.7 (CH=), 128.1 (CH=), 128.6 (CH=), 142.2 ppm (C); HRMS
elemental analysis calcd (%) for C10H14O [M+]: 150.1045, found:
150.1043; ee (GC, CP-Chirasil-Dex CB column, 90 kPa H2, 1108C iso-
therm): tR =8.8 (S), 9.2 min (R).
General procedure: The corresponding ligand (2.5ꢃ10À2 mmol)
and [Ir(m-Cl)(cod)]2 (8.4 mg, 2.5ꢃ10À5 mmol) were dissolved in
hexane (2 mL) and stirred for 10 min at RT. Then, the slightly turbid
solution was cooled to 08C and the desired 1,1-disubstituted olefin
(1.0 mmol) slowly added. After 5 min, pinacolborane (150 mL,
1.0 mmol) was added dropwise. The ice bath was then removed
and the reaction stirred at RT. After 18 h, the volatiles were evapo-
rated and the crude mixture purified by column chromatography
4,4,5,5-Tetramethyl-2-(4-methyl-2-phenylpentyl)-1,3,2-dioxabor-
olane (1d): 1H NMR (CDCl3): d=0.81 (d, 3JHÀH =6.0 Hz, 3H, CH3,
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3
iBu), 0.85 (d, JHÀH =8.0 Hz, 3H, CH3, iBu), 1.02 (s, 12H, CH3, Bpin),
ee Values were determined after oxidation to 2-(4-methoxyphenyl)-
3,3-dimethylbutan-1-ol: H NMR (CDCl3): d=0.87 (s, 9H, CH3, tBu),
1
1.2–1.6 (m, 5H), 2.95 (m, 1H, CH), 7.1–7.3 ppm (m, 5H, CH=);
13C NMR (CDCl3): d=22.0 (CH3, iBu), 23.4 (CH3, iBu), 24.6 (CH3, Bpin),
24.7 (CH3, Bpin), 29.6 (CH2, iBu), 39.2 (CH, iBu), 49.0 (CH), 82.8 (C,
Bpin), 125.6 (CH=), 127.4 (CH=), 128.0 (CH=), 147.6 ppm (C); HRMS
elemental analysis calcd (%) for C18H29BO2 [M+]: 288.2261, found:
288.2262.
2.63 (m, 1H, CH), 3.82 (s, 3H, CH3O), 3.97 (m, 2H, CH2), 6.87 (d, 2H,
3
3JHÀH =8.4 Hz, CH=), 7.14 ppm (d, 2H, JHÀH =8.4 Hz, CH=); 13C NMR
(CDCl3): d=28.3 (CH3, tBu), 33.1 (C, tBu), 55.2 (OCH3), 58.1 (CH),
62.5 (CH2), 113.6 (CH=), 130.6 (CH=), 131.6 (C), 158.4 ppm (C);
HRMS elemental analysis calcd (%) for C13H20O2 [M+]: 208.1463,
found: 208.1460; ee (GC, CP-Chirasil-Dex CB column, 90 kPa H2,
110 8C for 40 min, 58CminÀ1 until 1508C, 208CminÀ1 until 1708C):
tR =49.6 (S), 49.9 min (R).
ee Values were determined after oxidation to 4-methyl-2-phenyl-
1
pentan-1-ol: H NMR (CDCl3): d=0.79 (m, 6H, CH3, iBu), 1.2–1.6 (m,
5H), 2.85 (m, 1H, CH), 3.62 (m, 2H, CH2), 7.1–7.3 ppm (m, 5H,
CH=); 13C NMR (CDCl3): d=21.8 (CH3, iBu), 23.5 (CH3, iBu), 25.3 (CH2,
iBu), 41.1 (CH, iBu), 46.4 (CH), 68.0 (CH2), 126.7 (CH=), 128.1 (CH=),
128.6 (CH=), 142.4 ppm (C); HRMS elemental analysis calcd (%) for
C12H18O [M+]: 178.1358, found: 178.1356; ee (HPLC using Chiracel
IA column, hexane/2-propanol=98:2, 0.5 mLminÀ1, l=220 nm):
tR =22.5 (S), 24.3 min (R).
2-(3,3-Dimethyl-2-(4-(trifluoromethyl)phenyl)butyl)-4,4,5,5-tetra-
methyl-1,3,2-dioxaborolane (1h): H NMR (CDCl3): d=0.86 (s, 6H,
1
CH3, Bpin), 0.88 (s, 6H, CH3, Bpin), 0.95 (s, 9H, CH3, tBu), 1.27 (m,
2H, CH2) 2.77 (m, 1H, CH), 7.28 (d, 2H, 3JHÀH =8.0 Hz, CH=),
7.47 ppm (d, 2H, 3JHÀH =8.0 Hz, CH=); 13C NMR (CDCl3): d=24.1
(CH3, Bpin), 24.5 (CH3, Bpin), 27.6 (CH3, tBu), 29.7 (C, tBu), 51.6 (CH),
82.9 (C, Bpin), 124.1 (CH=), 132.2 (CH=), 128.9 (C), 152.3 ppm (C);
HRMS elemental analysis calcd (%) for C19H28BF3O2 [M+]: 356.2134,
found: 356.2133.
4,4,5,5-Tetramethyl-2-(3-methyl-2-phenylbutyl)-1,3,2-dioxaboro-
1
3
lane (1e): H NMR (CDCl3): d=0.65 (d, JHÀH =8.0 Hz, 3H, CH3, iPr),
3
0.87 (d, JHÀH =8.0 Hz, 3H, CH3, iPr), 1.02 (s, 12H, CH3, Bpin), 1.04 (s,
12H, CH3, Bpin), 1.0–1.2 (m, 2H, CH2), 1.68 (m, 1H, CH, iPr), 2.55 (m,
1H, CH), 7.0–7.2 ppm (m, 5H, CH=);13C NMR (CDCl3): d=20.4 (CH3,
iPr), 20.6 (CH3, iPr), 24.4 (CH3, Bpin), 24.6 (CH3, Bpin), 35.3 (CH, iPr),
48.3 (CH), 82.7 (C, Bpin), 125.6 (CH=), 127.7 (CH=), 128.3 (CH=),
146.1 ppm (C); HRMS elemental analysis calcd (%) for C17H27BO2
[M+]: 274.2104, found: 274.2102.
ee Values were determined after oxidation to 3,3-dimethyl-2-(4-(tri-
fluoromethyl)phenyl)butan-1-ol: 1H NMR (CDCl3): d=0.87 (s, 9H,
3
CH3, tBu), 2.76 (m, 1H, CH), 4.06 (m, 2H, CH2), 7.34 (d, 2H, JHÀH
=
7.6 Hz, CH=), 7.59 ppm (d, 2H, 3JHÀH =7.6 Hz, CH=); 13C NMR
(CDCl3): d=28.3 (CH3, tBu), 32.1 (C, tBu), 58.8 (CH), 62.5 (CH2), 125.0
(CH=), 130.6 (CH=), 145.8 (C), 160.0 ppm (C); HRMS elemental anal-
ysis calcd (%) for C13H17BF3O [M+]: 246.1231, found: 246.1229; ee
(HPLC, Chiracel IA column, hexane/2-propanol=98:2, 0.5 mLminÀ1
l=220 nm): tR =32.7 (S), 38.4 min (R).
ee Values were determined after oxidation to 3-methyl-2-phenylbu-
tan-1-ol: 1H NMR (CDCl3): d=0.75 (d, 3JHÀH =8.0 Hz, 3H, CH3, iPr),
,
3
1.02 (d, JHÀH =8.0 Hz, 3H, CH3, iPr), 1.93 (m, 1H, CH, iPr), 2.55 (m,
1H, CH), 3.8–4.0 (m, 2H, CH2), 7.2–7.4 ppm (m, 5H, CH=); 13C NMR
(CDCl3): d=21.0 (CH3, iPr), 21.1 (CH3, iPr), 30.1 (CH, iPr), 55.8 (CH),
65.2 (CH2), 126.7 (CH=), 128.5 (CH=), 128.7 (CH=), 141.6 ppm (C);
HRMS elemental analysis calcd (%) for C11H16O [M+]: 164.1201,
found: 164.1202; ee (HPLC, Chiracel IA column, hexane/2-propa-
nol=98:2, 0.5 mLminÀ1, l=210 nm): tR =25.2 (S), 26.5 min (R).
2-(3,3-Dimethyl-2-(naphthalen-2-yl)butyl)-4,4,5,5-tetramethyl-
1
1,3,2-dioxaborolane (1i): H NMR (CDCl3): d=0.81 (s, 9H, CH3, tBu),
0.87 (s, 6H, CH3, Bpin), 0.91 (s, 6H, CH3, Bpin), 1.2–1.4 (m, 2H, CH2),
2.89 (m, 1H, CH), 7.4–7.8 ppm (m, 7H, CH=); 13C NMR (CDCl3): d=
24.1 (CH3, Bpin), 24.5 (CH3, Bpin), 27.8 (CH3, tBu), 34.4 (C, tBu), 51.7
(CH), 82.7 (C, Bpin), 124.4 (CH=), 125.4 (CH=), 126.3 (CH=), 127.3
(CH=), 127.7 (CH=), 132.2 (C), 133.0 ppm (C); HRMS elemental anal-
ysis calcd (%) for C22H31BO2 [M+]: 338.2417, found: 338.2415.
2-(3,3-Dimethyl-2-(p-tolyl)butyl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (1 f): 1H NMR (CDCl3): d=0.85 (s, 9H, CH3, tBu), 0.94 (s,
6H, CH3, Bpin), 0.97 (s, 6H, CH3, Bpin), 1.21 (m, 2H, CH2), 2.27 (s,
3H, CH3), 2.67 (m, 1H, CH), 6.9–7.1 ppm (m, 4H, CH=); 13C NMR
(CDCl3): d=20.9 (CH3), 24.2 (CH3, Bpin), 24.5 (CH3, Bpin), 27.7 (CH3,
tBu), 34.0 (C, tBu), 51.2 (CH), 82.7 (C, Bpin), 127.7 (CH=), 129.5
(CH=), 134.9 (C), 141.2 ppm (C); HRMS elemental analysis calcd (%)
for C19H31BO2 [M+]: 302.2417, found: 302.2415.
ee Values were determined after oxidation to 3,3-dimethyl-2-(naph-
thalen-2-yl)butan-1-ol: 1H NMR (CDCl3): d=0.83 (s, 9H, tBu), 2.79
(m, 1H, CH), 4.07 (m, 2H, CH2), 7.30–7.77 ppm (m, 7H, CH=);
13C NMR (CDCl3): d=28.5 (CH3, tBu), 33.7 (C, tBu), 59.1 (CH), 62.6
(CH2), 125.5 (CH=), 126.1 (CH=), 127.5 (CH=), 127.6 (CH=), 127.7
(CH=), 132.5 (C), 133.2 (C), 137.7 ppm (C); HRMS elemental analysis
calcd (%) for C16H20O [M+]: 228.1514, found: 228.1513; ee (HPLC,
Chiracel IA column, hexane/2-propanol=98:2, 0.5 mLminÀ1, l=
220 nm): tR =40.4 (S), 44.5 min (R).
ee Values were determined after oxidation to 3,3-dimethyl-2-(p-tol-
1
yl)butan-1-ol: H NMR (CDCl3): d=0.88 (s, 9H, CH3, tBu), 2.33 (s, 3H,
CH3), 2.64 (m, 1H, CH), 4.0 (m, 2H, CH2), 7.1–7.2 ppm (m, 4H,
CH=); 13C NMR (CDCl3): d=21.0 (CH3), 28.4 (CH3, tBu), 33.0 (C, tBu),
58.9 (CH), 62.5 (CH2), 128.9 (CH=), 129.6 (CH=), 136.3 (C),
136.7 ppm (C); HRMS elemental analysis calcd (%) for C13H20O [M+]:
192.1514, found: 192.1511; ee (GC using Chiradex B-DM column,
77 kPa H2, 1108C isotherm): tR =26.5 (S), 27.5 min (R).
2-(3,3-Dimethyl-2-(m-tolyl)butyl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (1j): 1H NMR (CDCl3): d=0.93 (s, 9H, CH3, tBu), 0.95 (s,
6H, CH3, Bpin), 0.96 (s, 6H, CH3, Bpin), 1.23 (m, 2H, CH2), 2.29 (s,
3H, CH3), 2.68 (m, 1H, CH), 6.9–7.1 ppm (m, 5H, CH=); 13C NMR
(CDCl3): d=21.4 (CH3), 24.2 (CH3, Bpin), 24.5 (CH3, Bpin), 27.7 (CH3,
tBu), 34.0 (C, tBu), 51.5 (CH), 82.6 (C, Bpin), 126.2 (CH=), 127.0
(CH=), 136.3 (CH=), 138.0 (C), 144.3 ppm (C); HRMS elemental anal-
ysis calcd (%) for C19H31BO2 [M+]: 302.2417, found: 302.2414.
2-(2-(4-Methoxyphenyl)-3,3-dimethylbutyl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (1g): 1H NMR (CDCl3): d=0.83 (s, 9H, CH3,
tBu), 0.90 (s, 6H, CH3, Bpin), 0.97 (s, 6H, CH3, Bpin), 1.22 (m, 2H,
3
CH2), 2.65 (m, 1H, CH), 3.76 (s, 3H, OCH3), 6.75 (d, 2H, JHÀH
=
ee Values were determined after oxidation to 3,3-dimethyl-2-(m-tol-
yl)butan-1-ol: H NMR (CDCl3): d=0.89 (s, 9H, CH3, tBu), 2.35 (s, 3H,
CH3), 2.65 (m, 1H, CH), 4.01 (m, 2H, CH2), 7.05–7.2 ppm (m, 5H,
CH=); 13C NMR (CDCl3): d=21.6 (CH3), 28.4 (CH3, tBu), 33.0 (C, tBu),
58.9 (CH), 62.6 (CH2), 126.8 (CH=), 128.05 (CH=), 137.7 ppm (C);
HRMS calcd for C13H20O [M+]: 192.1514, found: 192.1512; ee (GC,
8.0 Hz, CH=), 7.07 ppm (d, 2H, 3JHÀH =8.0 Hz, CH=); 13C NMR
(CDCl3): d=24.2 (CH3, Bpin), 24.6 (CH3, Bpin), 27.6 (CH3, tBu), 34.1
(C, tBu), 50.7 (CH), 55.2 (OCH3), 82.7 (C, Bpin), 112.5 (CH=), 130.4
(CH=), 136.6 (C), 157.7 ppm (C); HRMS elemental analysis calcd (%)
for C19H31BO3 [M+]: 318.2366, found: 318.2365.
1
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[3] See for example: a) D. S. Matteson, Chem. Rev. 1989, 89, 1535–1551;
b) E. Hupe, I. Marek, P. Knochel, Org. Lett. 2002, 4, 2861–2863; c) D.
Imao, B. W. Glasspoole, V. S. Laberge, C. M. Crudden, J. Am. Chem. Soc.
2009, 131, 5024–5025.
[4] S. P. Thomas, V. K. Aggarwal, Angew. Chem. Int. Ed. 2009, 48, 1896–
1898; Angew. Chem. 2009, 121, 1928–1930.
[5] a) M. Sato, N. Miyaura, A. Suzuki, Tetrahedron Lett. 1990, 31, 231–234;
b) K. Burgess, M. J. Ohlmeyer, J. Org. Chem. 1988, 53, 5178–5179; c) K.
Burgess, W. A. van der Donk, M. J. Ohlmeyer, Tetrahedron: Asymmetry
1991, 2, 613–621; d) T. Hayashi, Y. Matsumoto, Y. Ito, Tetrahedron: Asym-
metry 1991, 2, 601–612.
[6] a) A. Z. Gonzalez, J. G. Romꢄn, E. Gonzalez, J. Martinez, J. R. Medina, K.
Matos, J. A. Soderquist, J. Am. Chem. Soc. 2008, 130, 9218–9219; b) R.
Corberꢄn, N. W. Mszar, A. H. Hoveyda, Angew. Chem. Int. Ed. 2011, 50,
7079–7082; Angew. Chem. 2011, 123, 7217–7220; c) C. Mazet, D.
Gꢁrard, Chem. Commun. 2011, 47, 298–300.
[7] See for example: a) B. Wang, O. A. Wong, M.-X. Zhao, Y. Shi, J. Org.
Chem. 2008, 73, 9539–9543 (epoxidation); b) X. Wang, M. Zak, M. Mad-
dess, P. O’Shea, R. Tillyer, E. J. J. Grabowski, P. J. Reider, Tetrahedron Lett.
2000, 41, 4865–4869 (dihydroxylation); c) J. Mazuela, J. J. Verendel, M.
Coll, B. Schꢅffner, A. Bçrner, P. G. Andersson, O. Pꢀmies, M. Diꢁguez, J.
Am. Chem. Soc. 2009, 131, 12344–12353 (hydrogenation); d) O. Pꢀmies,
P. G. Andersson, M. Diꢁguez, Chem. Eur. J. 2010, 16, 14232–14240 (hy-
drogenation).
CP-Chirasil-Dex CB column, 90 kPa H2, 1108C isotherm): tR =20.1
(S), 21.9 min (R).
4,4,5,5-Tetramethyl-2-(3,3,3-trifluoro-2-(4-methoxyphenyl)prop-
1
yl)-1,3,2-dioxaborolane (1k): H NMR (CDCl3): d=1.03 (s, 6H, CH3,
Bpin), 1.09 (s, 6H, CH3, Bpin), 1.40 (m, 2H, CH2), 3.54 (m, 1H, CH),
3
3.79 (s, 3H, CH3O), 6.84 (d, 2H, JHÀH =8.4 Hz, CH=), 7.23 ppm (d,
3
2H, JHÀH =8.4 Hz, CH=); 13C NMR (CDCl3): d=24.3 (CH3, Bpin), 24.4
3
(CH3, Bpin), 44.8 (q, CH, JHÀF =28.1 Hz), 55.2 (CH3O), 83.0 (C, Bpin),
113.6 (CH=), 128.5 (d, C, JCÀF =29.7 Hz), 128.7 (C), 130.0 (CH=),
159.2 ppm (C); HRMS elemental analysis calcd (%) for C16H22BF3O3
[M+]: 330.1614, found: 330.1612.
ee Values were determined after oxidation to 3,3,3-trifluoro-2-(4-
1
methoxyphenyl)propan-1-ol: H NMR (CDCl3): d=3.45 (m, 1H, CH),
3.8 (s, 3H, CH3O), 3.98 (m, 1H, CH2), 4.16 (m, 1H, CH2), 6.92 (d, 2H,
3
3JHÀH =8.4 Hz, CH=), 7.25 ppm (d, 2H, JHÀH =8.4 Hz, CH=); 13C NMR
(CDCl3): d=51.5 (q, CH, JCÀF =25.4 Hz), 55.2 (CH3O), 61.2 (CH2),
114.3 (CH=), 124.6 (d, C, JCÀF =30.2 Hz), 130.2 (CH=), 159.7 ppm (C);
HRMS elemental analysis calcd (%) for C10H11F3O [M+]: 220.0711,
found: 220.0712; ee (GC, CP-Chirasil-Dex CB column, 90 kPa H2,
110 8C isotherm): tR =28.2 (S), 29.4 min (R).
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Acknowledgements
We thank the Spanish Government for providing grant
CTQ2013–40568, the Catalan Government for grant 2014SGR670,
and the ICREA Foundation for providing M.D. and O.P. with finan-
cial support through the ICREA Academia awards.
Keywords: alkenes · asymmetric catalysis · hydroboration ·
iridium · phosphite-oxazoline ligands
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Received: October 14, 2014
Published online on && &&, 0000
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 8
&
7
&
ÞÞ
These are not the final page numbers!

FULL PAPERS
M. Magre, M. Biosca, O. Pꢀmies,*
M. Diꢁguez*
&& – &&
Filling the Gaps in the Challenging
Asymmetric Hydroboration of 1,1-
Disubstituted Alkenes with Simple
Phosphite-Based Phosphinooxazoline
Iridium Catalysts
Might of the phosphite: The highly
regio- and enantioselective hydrobora-
tion of challenging 1,1-disubstituted
olefins is achieved by using iridium cat-
alysts modified with chiral phosphite-
based phosphinooxazoline ligands. Use
of the biaryl phosphite moiety in the
ligand design is adventitious in terms of
substrate versatility. The scope of the
new phosphite-based catalysts is com-
plementary to that exhibited by tert-
butyl-substituted phosphinooxazoline
iridium and N-heterocyclic carbene
copper catalysts. Bpin=Pinacolato.
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 8
&
8
&
ÞÞ
These are not the final page numbers!