Chiral benzazaboroles as catalysts for enantioselective sulfonylation of: Cis -1,2-diols

Article abstract of DOI:10.1039/c8ob03205j

A newly developed benzazaborole smoothly catalyzed the enantioselective sulfonylation of cis-1,2-diols. Using a chiral benzazaborole/NMI co-catalyst system, various sulfonate esters were prepared in high yields with good enantioselectivities.

Full text of DOI:10.1039/c8ob03205j

Organic &
Biomolecular Chemistry
View Article Online
View Journal
PAPER
Chiral benzazaboroles as catalysts for
enantioselective sulfonylation of cis-1,2-diols†
Cite this: DOI: 10.1039/c8ob03205j
Satoru Kuwano, * Yusei Hosaka and Takayoshi Arai
*
Received 26th December 2018,
Accepted 13th March 2019
A newly developed benzazaborole smoothly catalyzed the enantioselective sulfonylation of cis-1,2-diols.
Using a chiral benzazaborole/NMI co-catalyst system, various sulfonate esters were prepared in high
yields with good enantioselectivities.
DOI: 10.1039/c8ob03205j
rsc.li/obc
bioactivity studies4 and synthetic routes to various benz-
oxaboroles have been established.5 However, the chemistry of
Introduction
Benzoxaboroles have promising applications in various fields benzazaboroles, which are nitrogen analogs of benzoxaboroles,
of chemistry (Fig. 1).1,2 Since the discovery of their exceptional still remains to be explored in detail. Only a few applications
sugar-binding properties, these compounds have been used as of benzazaborole derivatives as receptors for glycoproteins or
receptors for a wide range of biomolecules.3 Moreover, various iodide ions have been reported.6 To the best of our knowledge,
nanoparticles and copolymers incorporating the benzoxaborole there is no example of the use of benzoxaboroles and benz-
functionality have been exploited.3 Major developments in azaboroles as catalysts in synthetic organic chemistry.7–10
benzoxaborole chemistry are related to their biological activity, Although benzazaboroles are not being investigated in depth
and large libraries of these compounds have been prepared for at present, we envisaged that they have attractive inherent
utility because the introduction of an additional substituent
on the nitrogen atom may allow us to modify the (1) steric,
(2) electronic, and (3) chiral environments around the boron
center.
In 2011, Taylor et al. carried out a pioneering study on the
organoboron-catalyzed activation of vicinal diols and demon-
strated the borinic acid-catalyzed monoacylation of cis-1,2-
diols.11 This methodology was further extended to the borinic
acid-catalyzed monofunctionalization (acylation, alkylation,
sulfonylation, and glycosylation) of various substrates, includ-
Fig. 1 Applications of benzoxaboroles and benzazaboroles.
ing carbohydrate derivatives.12 Here, we report the develop-
ment of novel chiral benzazaborole catalysts and their appli-
cations in the enantioselective sulfonylation of cis-1,2-diols
because chiral sulfonate esters are important synthetic inter-
mediates in the synthesis of complex molecules (Scheme 1).13–16
Results and discussion
We first commenced the synthesis of the chiral benzazaborole
catalyst (Scheme 2). Simple reductive alkylation of a chiral
Scheme 1 Chiral benzazaborole-catalyzed enantioselective sulfonylation.
primary amine with commercially available 2-formylphenyl-
Soft Molecular Activation Research Center (SMARC), Chiba Iodine Resource
Innovation Center (CIRIC), Molecular Chirality Research Center (MCRC),
Synthetic Organic Chemistry, Department of Chemistry, Graduate School of Science,
Chiba University, 1-33 Yayoi, Inage, Chiba, Japan. E-mail: skuwano@chiba-u.jp,
tarai@faculty.chiba-u.jp
boronic acid readily furnished 2-aminomethyphenylboronic
acid, which was intramolecularly dehydrated after work-up to
give benzazaborole 1a on a gram scale (1.48 g, 72% yield).17
1
The dehydrated structure of 1a was confirmed by H NMR (in
deuterated DMSO), 11B NMR, and ESI-MS spectral analyses
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
c8ob03205j
(see the ESI† for details). Benzazaborole derivatives 1b–1f were
This journal is © The Royal Society of Chemistry 2019
Org. Biomol. Chem.

View Article Online
Paper
Organic & Biomolecular Chemistry
1b was a potential catalyst for the sulfonylation and afforded
the product 4a in 11% yield (entries 1 and 2). Based on this
preliminary result, chiral versions of benzazaborole were
tested as catalysts. Cinchonidine-derived 1a smoothly pro-
moted the reaction, giving the product 4a in 62% yield and
with 30% ee (entry 3). The absolute stereochemistry of 4a was
confirmed by the reported optical rotation of 4a.15a
Cinchonine-derived 1c, which is a pseudo-enantiomer of 1a,
afforded the opposite enantiomer with a similar selectivity
(entry 4). Quinine-derived 1d also promoted the reaction in an
enantioselective manner, but the chemical yield was relatively
low (entry 5). Diphenylethylene diamine-derived benzazaborole
1f was less effective in terms of both reactivity and selectivity
(entry 7). Interestingly, chiral 2-aminomethylphenylboronic
acid derivatives 1g and 1h did not result in effective asym-
metric induction (entries 8 and 9). In the presence of catalyst
1i, which had no boronic acid moiety, sulfonylation did not
proceed at all (entry 10). This result indicates that the organo-
boron functionality is essential for promoting this reaction,
and Lewis base catalysis based on cinchona alkaloids were
excluded from our experiments. Examination of the base effect
revealed that Na2CO3 was the most appropriate base, leading
to increased enantioselectivity (70% ee, entry 14). For further
improvement of the chemical yield, we used a Lewis base co-
catalyst that activates 3a.20 Among the tested co-catalysts,
N-methyl imidazole (NMI) gave the best result, and the
product was obtained in 86% yield with 83% ee (entry 17, see
the ESI† for details). Finally, the optimized conditions for this
enantioselective reaction were set as 10 mol% catalyst 1a and
5 mol% NMI, with 2 equiv. of 3a and Na2CO3 at room tempera-
ture in MeCN, which afforded the product 4a in 92% yield and
with 82% ee (entry 20).
Scheme 2 Synthesis of chiral benzazaborole 1a.
prepared according to the same reductive alkylation procedure.
For comparison, chiral 2-aminomethylphenylboronic acids 1g
and 1h were also synthesized.18,19
With the various organoboron species in hand, we next
evaluated their effectiveness as catalysts for the desymmetriza-
tion of cis-1,2-cyclohexanediol 2a using TsCl 3a (Table 1). To
our delight, the initial trial revealed that achiral benzazaborole
Table 1 Optimization of reaction conditionsa
Under the optimized conditions, the substrate scope of this
chiral benzazaborole-catalyzed enantioselective sulfonylation
was examined (Table 2). A variety of para-, meta- and ortho-sub-
stituted benzenesulfonyl chlorides could be readily applied to
this protocol, and compounds 4a–4g were obtained in high
yields with good enantioselectivities. 3,4-Disubstituted benzene-
sulfonyl chlorides and bulky naphthalenesulfonyl chlorides
were also compatible with the reaction conditions, giving 4i–4l
with good selectivities. Furthermore, cis-cyclohex-4-ene-1,2-diol
furnished the corresponding product 4m in 92% yield and
with 76% ee. Unfortunately, the reaction using cis-1,2-cyclo-
pentanediol and heptanediol gave sulfonate esters 4n and 4o
with low selectivities. Non-cyclic diol did not produce the
corresponding product 4p. To demonstrate the synthetic
utility, the gram scale synthesis of 4a was examined. When
1.0 g of 2a was used, 2.17 g of 4a was obtained in 93% yield
with 82% ee without column chromatography after simple
aqueous work-up.
Entry
1
Co-catalyst
Base
Yieldb (%)
eec (%)
1
2
3
4
5
6
7
8
None
1b
1a
1c
1d
1e
1f
1g
1h
1i
1a
1a
1a
1a
1a
1a
1a
1c
None
None
None
None
None
None
None
None
None
None
None
None
None
None
DMAP
DMAPO
NMI
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
Et3N
Pyridine
K2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Trace
11
62
57
32
11
16
54
49
Trace
37
32
60
45
74
81
86
85
—
—
30
−26
51
rac
−8
rac
−9
N.D.
60
5
35
70
63
79
83
81
75
82
9
10
11
12
13
14
15
16
17
18
19d
20e
NMI
NMI
NMI
1a
1a
78
92
The sulfonyl group is more stable under basic conditions as
compared to the acyl or silyl protecting groups, which some-
times cause a decrease in optical purity via intramolecular
1,2-acyl or silyl migrations.15a,21 Considering the importance
of orthogonally protected diols as chiral building blocks, we
implemented the sequential dual protection of diols in one
a The reactions were carried out using 0.1 mmol of 2a with 1.5 equiv.
of 3a in the presence of 1 in the solvent (0.5 mL). b Isolated yield based
on the amount of 2a. c Determined by chiral HPLC analysis. d 10 mol%
NMI were used. e The reaction was carried out using 2 equiv. of TsCl
and Na2CO3 for 14 h.
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2019

View Article Online
Organic & Biomolecular Chemistry
Paper
Table 2 Substrate scopea
Scheme 3 Transformation of sulfonate esters.
Scheme 4 Further applications of the benzazaborole/NMI co-catalyst
system.
a The reactions were carried out using 0.2 mmol of 2.
Table 3 Sequential dual protection in one pota
tated the unique regiodivergent kinetic resolution of the sub-
stituted cyclohexanediol 8 (Scheme 4a). Regioselective sulfony-
lation of the protected methyl α-D-galactopyranoside 11 was
also promoted (Scheme 4b). Interestingly, a matching/mis-
matching effect was observed when pseudo-enantiomeric cata-
lyst 1c was applied, and the reaction rate became slower.22
Mechanistic studies were performed to gain insights
into the reaction intermediates (Scheme 5). When a mixture of
benzazaborole 1a and diol 2a in dry toluene was stirred under
reflux for 14 h, the corresponding condensed compound was
mainly produced in the crude reaction mixture, which was
analyzed by 1H NMR, 11B NMR, and ESI-MS.11 When the
resulting complex was subjected to the standard enantio-
selective sulfonylation conditions described above, 4a was
obtained in 72% yield and with 81% ee, suggesting that the
condensed compound is an actual reaction intermediate.
Based on the experimental observations, we propose a plaus-
ible catalytic cycle, as depicted in Scheme 6. Benzazaborole 1a
enters the catalytic cycle by binding with the diol to form the
condensed compound A. The acidity of the OH proton is
enhanced by the assistance of the boron center, providing the
Entry
Electrophile
5
R
Yield (%)
ee (%)
1
2
3
4
5
BzCl
Ac2O
TESCl
TBSCl
TBDPSCl
5a
5b
5c
5d
5e
Bz
Ac
TES
TBS
TBDPS
80
79
84
76
74
81
79
81
81
81
a The reactions were carried out using 0.1 mmol of 2a.
pot via the Lewis base catalysis of NMI (Table 3). After the com-
pletion of the first 1a/NMI-co-catalyzed enantioselective sulfo-
nylation, MeCN was removed by evaporation, and additional
CHCl3, an electrophile, and pyridine were employed for the
NMI-catalyzed second functionalization. Using this sequential
procedure, various acyl and silyl protecting groups such as Bz,
Ac, TES, TBS, and TBDPS were successfully introduced without
loss of ee.
The synthetic utility of sulfonate esters is shown in
Scheme 3. Treatment of 5e with NaN3 smoothly furnished
azide 6, which is easily converted into 1,2-aminoalcohol.
Dihydroxylation of the olefin unit in 4m gave optically active
tetraol 7 in a diastereoselective manner.
Further application of this benzazaborole/NMI co-catalyst
system is described in Scheme 4. This catalytic system facili- Scheme 5 Mechanistic studies.
This journal is © The Royal Society of Chemistry 2019
Org. Biomol. Chem.

View Article Online
Paper
Organic & Biomolecular Chemistry
0.25 mm 230–400 mesh silica gel containing a fluorescent
indicator (Merck, #1.05715.0009). Silica gel column chroma-
tography was performed on Kanto silica gel 60 (spherical,
100–210 μm). Alumina column chromatography was per-
formed on aluminium oxide 90 active neutral (Merck,
#1.01077.1000). IR spectra were recorded on a JASCO FT/
1
IR-4100 system using ATR. H-NMR spectra were recorded on
JEOL ECS-400 (400 MHz), ECA-500 (500 MHz), and ECX-400
(400 MHz) spectrometers. Chemical shifts of the 1H-NMR
spectra were reported relative to tetramethyl silane (δ 0).
13C-NMR spectra were recorded on JEOL ECS-400 (100 MHz),
ECA-500 (125 MHz), and ECX-400 (100 MHz) spectrometers.
Chemical shifts of the 13C-NMR spectra were reported relative
to CDCl3 (δ 77.0). Splitting patterns were reported as s, singlet;
d, doublet; t, triplet; q, quartet; m, multiplet; and br, broad.
Scheme 6 Proposed catalytic cycle.
Synthesis of chiral benzazaboroles and boronic acid catalysts
A. 1a, 1b, 1c, 1d and 1e. 2-Formylphenylboronic acid
(1.5 eq.), amine (1 eq.), 4 Å molecular sieves and 1,2-dichloro-
ethane (0.35 M) were added to a round-bottom flask contain-
ing a stir bar under Ar. After being stirred for an appropriate
length of time at room temperature, 4 Å molecular sieves were
removed from the mixture by filtration, and the filtrate was
concentrated in a one-necked round-bottom flask under
reduced pressure. The residue was dissolved in MeOH (0.35 M)
and sodium borohydride (2 eq.) was added portionwise at
0 °C. After being stirred for 10 minutes at 0 °C, the mixture
was further stirred for an appropriate length of time at room
temperature. The reaction was quenched by the addition of
water at 0 °C, and the aqueous layer was extracted with di-
chloromethane 5 times. The combined organic layers were
dried over Na2SO4 and concentrated under reduced pressure.
After purification by alumina column chromatography (chloro-
form/methanol = 1/0 to 100/1), the corresponding catalysts
were obtained.
Scheme 7 Control experiments.
ate complex B under basic conditions. On the other hand,
NMI activates sulfonyl chloride as a nucleophilic catalyst to
give the corresponding imidazolium salt. Sulfonyl transfer
from the imidazolium salt to the ate complex produces inter-
mediate C. Finally, alcohol exchange of C with the additional
diol liberates the target product and the condensed compound
A is regenerated. Control experiments reveal that the combi-
nation of the phenyl boronic acid and amine base is not
effective for reaction promotion (Scheme 7). These results
support the importance of the benzazaborole structure.
Conclusions
In conclusion, we have developed unique chiral benzazaborole
catalysts, which can be easily synthesized from a chiral
primary amine and commercially available 2-formylphenyl-
boronic acid. Although the application of benzazaboroles as
catalysts in synthetic organic chemistry is an unestablished
research field, the newly developed benzazaboroles smoothly
catalyze the enantioselective sulfonylation of cis-1,2-diols.
Using the chiral benzazaborole/Lewis base co-catalyst system,
various sulfonate esters are obtained in high yields with good
enantioselectivities. The sequential dual protection of the diol
in one pot is also demonstrated. Our ongoing research is
aimed at the elucidation of a more precise reaction mecha-
nism and the application of the chiral benzazaborole catalysts
to obtain more complex carbohydrate derivatives.
2-((S)-Quinolin-4-yl((1S,2S,4S,5R)-5-vinylquinuclidin-2-yl)-
methyl)-2,3-dihydro-1H-benzo[c][1,2]azaborol-1-ol (1a).
Cinchonidine-derived amine was used; reaction time: 22 h for
Schiff base formation, 4 h for reduction; white solids (72%
1
yield); H NMR (400 MHz, CD3OD): δ 8.94 (d, J = 4.5 Hz, 1H),
8.44 (d, J = 7.7 Hz, 1H), 8.10 (d, J = 8.4 Hz, 1H), 7.86–7.71 (m,
3H), 7.49 (d, J = 6.6 Hz, 1H), 7.20–6.96 (m, 2H), 6.86 (br s, 1H),
6.00–5.76 (m, 1H), 5.27–4.95 (m, 3H), 3.88 (br, 2H), 3.59–3.21
(m, 3H), 3.05–2.67 (m, 2H), 2.36 (br s, 1H), 1.62 (br s, 3H),
1.40–1.28 (m, 1H), 0.73 (br s, 1H); 13C NMR (100 MHz,
CD3OD): δ 150.8, 149.1, 144.9, 142.6, 134.1, 131.2, 130.2, 129.6,
128.6, 128.3, 127.9, 124.8, 121.6, 115.0, 61.3, 56.6, 52.2, 41.9,
40.8, 28.7, 28.4, 26.6; IR (neat) 3255, 3060, 3001, 2941, 1593,
1446, 1392, 1360, 1218, 745 cm−1; HRMS (ESI+) calcd for
C26H29BN3O [M + H]+ 410.2404, found 410.2394; [α]2D4 = +36.8
(c = 1.0, CHCl3).
Experimental
General
2-Benzyl-2,3-dihydro-1H-benzo[c][1,2]azaborol-1-ol (1b).
Benzyl amine was used; reaction time: 16 h for Schiff base for-
Dry solvents were purchased from commercial suppliers and mation, 3 h for reduction; white solids (56% yield); 1H NMR
used without further purification. Analytical thin-layer chroma- (400 MHz, CD3OD): δ 8.28 (s, 1H), 7.48–7.18 (m, 9H), 4.39
tography (TLC) was performed on glass plates coated with (s, 2H), 3.87 (s, 2H); 13C NMR (100 MHz, CD3OD): δ 142.2,
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2019

View Article Online
Organic & Biomolecular Chemistry
Paper
136.1, 131.6, 130.8, 129.9, 129.4, 128.3, 127.6, 124.3, 54.1, 52.2; dried over Na2SO4. After the removal of the solvent under
IR (neat) 3240, 3071, 3038, 1452, 1354, 1289, 1218, 1180, 741, reduced pressure, the resulting residue was purified by silica-
702 cm−1; HRMS (ESI+) calcd for C14H17BNO2 [M + H3O]+ gel column chromatography (hexane/ethyl acetate = 3 : 1 or
242.1352, found 242.1347.
2 : 1) to afford product 4. The enantiomeric excesses of the pro-
2-((S)-(6-Methoxyquinolin-4-yl)((1S,2S,4S,5R)-5-vinylquinuclidin- ducts were determined by chiral stationary phase HPLC on
2-yl)methyl)-2,3-dihydro-1H-benzo[c][1,2]azaborol-1-ol (1c). Daicel Chiralpak AS-H, AD-3, and Chiralcel OJ-H columns.
Quinine-derived amine was used; reaction time: 15 h for Schiff
Analytical data for products of enantioselective sulfonylation
of cis-1,2-diols
base formation, 5 h for reduction; white solids (35% yield);
1H NMR (400 MHz, CD3OD): δ 7.61–7.24 (m, 7H), 7.24–7.13
(m, 2H), 7.07 (d, J = 7.0 Hz, 1H), 3.98 (s, 2H), 3.86 (s, 2H);
(1R,2S)-2-Hydroxycyclohexyl 4-methylbenzenesulfonate (4a).
13C NMR (100 MHz, CD3OD): δ 158.7, 146.8, 144.0, 141.4, Reaction time: 13 h; colorless oil (50.9 mg, 92% yield);
132.9, 130.4, 129.5, 126.6, 122.6, 120.4, 113.8, 101.5, 59.9, 55.4, 1H NMR (400 MHz, CDCl3): δ 7.82 (d, J = 8.4 Hz, 2H), 7.35 (d,
55.1, 50.4, 48.6, 40.6, 39.5, 27.5, 27.3, 25.4, 11.1; IR (neat) J = 8.4 Hz, 2H), 4.70–4.61 (m, 1H), 3.83 (br, 1H), 2.46 (s, 3H),
3370, 2484, 2229, 2065, 1473, 1370, 1120, 974 cm−1; HRMS 2.01 (d, J = 5.0, H), 1.95–1.87 (m, 1H), 1.78–1.71 (m, 1H),
(ESI+) calcd for C27H31BN3O2 [M + H]+ 440.2509, found 1.67–1.47 (m, 4H), 1.34–1.25 (m, 2H); 13C NMR (100 MHz,
440.2505; [α]2D4 = +13.8 (c = 1.0, CHCl3).
CDCl3): δ 144.9, 133.8, 129.9, 127.7, 123.9, 122.4, 80.6, 67.0,
(S)-2-(1-Phenylethyl)-2,3-dihydro-1H-benzo[c][1,2]azaborol-1-ol 31.4, 28.4, 21.6; IR (neat) 3418, 2945, 2870, 1343, 1174, 930,
(1d). (S)-(−)-1-Phenylethylamine was used; reaction time: 20 h 892, 669 cm−1; HRMS (ESI+) calcd for C13H18O4NaS [M + Na]+
for Schiff base formation, 2 h for reduction; white solids (50% 293.0818, found 293.0812; [α]2D2 = +3.4 (c = 1.0, CHCl3, 81% ee).
1
yield); H NMR (400 MHz, DMSO-D6): δ 8.23 (s, 1H), 7.69 (d, The enantiomeric excess was determined by HPLC with a
J = 7.0 Hz, 1H), 7.39–7.16 (m, 8H), 4.89 (q, J = 7.0 Hz, 1H), Chiralcel OJ-H column (hexane : 2-propanol = 90 : 10, 1.0 mL
4.00 (d, J = 16.6 Hz, 1H), 3.65 (d, J = 16.6 Hz, 1H), 1.60 (d, J = min−1, 254 nm); minor enantiomer tR = 13.5 min, major enan-
7.0 Hz, 3H); 13C NMR (100 MHz, CD3OD): δ 141.3, 140.5, tiomer tR = 12.1 min, 81% ee.
133.0, 130.0, 129.5, 128.6, 127.9, 126.6, 58.9, 53.8, 20.9;
(1R,2S)-2-Hydroxycyclohexyl benzenesulfonate (4b). Reaction
IR (neat) 3294, 3001, 1446, 1337, 1300, 1218, 1186, 1110, 908, time: 12 h; colorless oil (25.7 mg, 96% yield); 1H NMR
751, 708 cm−1; HRMS (ESI+) calcd for C15H19BNO2 [M + H3O]+ (400 MHz, CDCl3): δ 7.95 (d, J = 7.3 Hz, 2H), 7.67 (t, J = 7.3 Hz,
256.1503, found 256.1502; [α]2D4 = –2.1 (c = 1.0, CHCl3).
1H), 7.57 (t, J = 7.3 Hz, 2H), 4.69–4.65 (m, 1H), 3.84 (br, 1H),
2-((1S,2S)-2-(1H-Benzo[de]isoquinolin-2(3H)-yl)-1,2-diphenyl- 1.97–1.89 (m, 2H), 1.79–1.72 (m, 1H), 1.68–1.48 (m, 4H),
ethyl)-2,3-dihydro-1H-benzo[c][1,2]azaborol-1-ol (1e). (1S,2S)-2- 1.35–1.25 (m, 2H); 13C NMR (100 MHz, CDCl3): δ 137.1, 133.8,
(1H-Benzo[de]isoquinolin-2(3H)-yl)-1,2-diphenylethan-1-amine 129.3, 127.6, 83.4, 69.1, 30.2, 27.7, 21.6, 20.7; IR (neat) 3213,
was used; reaction time: 16 h for Schiff base formation, 2 h for 2945, 2865, 1451, 1355, 1184, 1098, 937, 895 cm−1; HRMS
reduction; white solids (11% yield); 1H NMR (400 MHz, (ESI+) calcd for C12H20NSO4 [M + NH4]+ 274.1108, found
CD3OD): δ 7.65 (d, J = 8.2 Hz, 2H), 7.49 (d, J = 7.0 Hz, 2H), 274.1103; [α]2D3 = +3.6 (c = 1.0, CHCl3, 84% ee). The enantio-
7.40–7.12 (m, 13H), 7.05 (t, J = 6.8 Hz, 1H), 6.92 (td, J = 6.1, meric excess was determined by HPLC with a Chiralcel OJ-H
1.4 Hz, 1H), 6.66 (d, J = 7.7 Hz, 1H), 5.22 (d, J = 11.8 Hz, 1H), column (hexane : 2-propanol = 90 : 10, 1.0 mL min−1, 254 nm);
4.72 (d, J = 11.8 Hz, 1H), 4.24 (d, J = 13.8 Hz, 2H), 3.93 (s, 2H), minor enantiomer tR = 18.2 min, major enantiomer tR
3.85 (d, J = 12.5 Hz, 2H); 13C NMR (100 MHz, CD3OD): δ 136.4, 15.2 min, 84% ee.
=
135.1, 134.5, 133.7, 132.9, 131.6, 131.3, 129.7, 129.5, 129.2,
(1R,2S)-2-Hydroxycyclohexyl 4-(tert-butyl)benzenesulfonate
129.0, 128.9, 128.3, 128.0, 127.4, 127.0, 126.6, 123.1, 72.5, 60.4, (4c). Reaction time: 19 h; colorless oil (54.7 mg, 86% yield);
54.2, 51.4; IR (neat) 33 358, 3060, 3038, 2935, 2506, 2224, 2077, 1H NMR (400 MHz, CDCl3): δ 7.85 (d, J = 8.8 Hz, 2H), 7.56 (d,
1446, 1376, 1110, 968, 751, 702 cm−1; HRMS (ESI+) calcd for J = 8.8 Hz, 2H), 4.69–4.65 (m, 1H), 3.85–3.81 (m, 1H), 2.01 (br,
C33H30BN2O [M + H]+ 481.2451, found 481.2439; [α]2D4 = +46.5 1H), 1.97–1.89 (m, 1H), 1.81–1.73 (m, 1H), 1.68–1.51 (m, 4H),
(c = 1.0, CHCl3).
1.35 (s, 9H), 1.33–1.25 (m, 2H); 13C NMR (100 MHz, CDCl3):
δ 157.6, 134.0, 127.4, 126.2, 83.1, 68.9, 35.2, 31.0, 30.2, 27.7,
21.7, 20.7; IR (neat) 3555, 2956, 1344, 1189, 943, 900,
761 cm−1; HRMS (ESI+) calcd for C16H28O4NS [M + NH4]+
General procedure for enantioselective sulfonylation of
cis-1,2-diols
Diol 2 (0.2 mmol, 1 eq.), sodium carbonate (0.4 mmol, 2 eq.), 330.1734, found 330.1730; [α]2D3 = +4.2 (c = 1.0, CHCl3, 77% ee).
catalyst 1a (0.02 mmol, 10 mol%), and sulfonyl chloride 3 The enantiomeric excess was determined by HPLC with
(0.4 mmol, 2 eq.) were added to a one-necked round-bottom
a Chiralpak AS-H column (hexane : 2-propanol = 95 : 5,
flask containing a stir bar, under an Ar atmosphere. To the 1.0 mL min−1, 254 nm); minor enantiomer tR = 24.7 min,
flask, 10 mM solution of 1-methylimidazole (NMI) in aceto- major enantiomer tR = 20.4 min, 77% ee.
nitrile (1.0 ml, 0.01 mmol, 5 mol%) was added. After stirring
(1R,2S)-2-Hydroxycyclohexyl 4-chlorobenzenesulfonate (4d).
for an appropriate length of time at room temperature, water Reaction time: 13 h; colorless oil (54.8 mg, 90% yield);
was added to the reaction mixture and then the aqueous layer 1H NMR (400 MHz, CDCl3): δ 7.88 (d, J = 8.6 Hz, 2H), 7.54 (d,
was extracted with ethyl acetate 3 times. The combined J = 8.8 Hz, 2H), 4.70–4.67 (m, 1H), 3.86–3.84 (m, 1H), 1.98–1.90
organic layers were washed with water and brine, and then (m, 1H), 1.82–1.49 (m, 6H), 1.36–1.25 (m, 2H); 13C NMR
This journal is © The Royal Society of Chemistry 2019
Org. Biomol. Chem.

View Article Online
Paper
Organic & Biomolecular Chemistry
(100 MHz, CDCl3): δ 140.3, 135.6, 129.5, 129.1, 83.8, 69.0, 30.2, 1H), 2.69 (s, 3H), 2.00 (d, J = 4.8 Hz, 1H), 1.94–1.86 (m, 1H),
27.8, 21.5, 20.8; IR (neat) 3534, 2951, 2865, 1350, 1189, 1.81–1.74 (m, 1H), 1.67–1.46 (m, 4H), 1.36–1.26 (m, 2H);
1092, 932, 900 cm−1; HRMS (ESI+) calcd for C12H15O4ClNaS 13C NMR (100 MHz, CDCl3): δ 138.2, 135.3, 133.7, 132.5, 129.5,
[M + Na]+ 313.0272, found 313.0267; [α]2D3 = +1.9 (c = 1.0, 126.1, 83.1, 68.9, 30.2, 27.5, 27.8, 20.6, 20.2; IR (neat) 3533,
CHCl3, 80% ee). The enantiomeric excess was determined 2946, 2870, 1452, 1337, 1180, 925, 892 cm−1; HRMS (ESI+)
by HPLC with a Chiralcel OJ-H column (hexane : 2-propanol = calcd for C16H19N3NaO2 [M + Na]+ 308.1369, found 308.1362;
90 : 10, 1.0 mL min−1, 254 nm); minor enantiomer tR
17.1 min, major enantiomer tR = 11.2 min, 80% ee.
=
[α]2D4 = +7.6 (c = 1.0, CHCl3, 84% ee). The enantiomeric excess
was determined by HPLC with a Chiralcel OJ-H column
(1R,2S)-2-Hydroxycyclohexyl 4-(trifluoromethyl)benzene- (hexane : 2-propanol = 90 : 10, 0.5 mL min−1, 254 nm); minor
sulfonate (4e). Reaction time: 14 h; colorless oil (53.6 mg, enantiomer tR = 22.0 min, major enantiomer tR = 20.2 min,
1
82% yield); H NMR (400 MHz, CDCl3): δ 8.08 (d, J = 8.2 Hz, 84% ee.
2H), 7.83 (d, J = 8.4 Hz, 2H), 4.78–4.75 (m, 1H), 3.88–3.86 (m,
(1R,2S)-2-Hydroxycyclohexyl 3-bromo-4-methylbenzenesulfonate
1H), 2.01–1.93 (m, 1H), 1.81–1.71 (m, 1H), 1.68–1.52 (m, 4H), (4i). Reaction time: 13 h; colorless oil (56.2 mg, 80% yield);
1.38–1.30 (m, 2H); 13C NMR (100 MHz, CDCl3): δ 140.8, 135.3 1H NMR (400 MHz, CDCl3): δ 7.79 (d, J = 2.0 Hz, 1H), 7.72 (d,
(d, J = 33.5 Hz), 128.2, 126.4 (d, J = 3.8 Hz), 123.0 (d, J = 274.0 J = 8.4 Hz, 1H), 7.60 (dd, J = 2.3, 8.4 Hz, 1H), 4.7–4.65 (m, 1H),
Hz), 84.3, 69.0, 30.2, 27.9, 21.5, 20.8; IR (neat) 3424, 2941, 3.86–3.84 (m, 1H), 2.49 (s, 3H), 2.05–1.90 (m, 2H), 1.81–1.72
2870, 1360, 1333, 1170, 1120, 930, 898, 768 cm−1; HRMS (ESI+) (m, 1H), 1.68–1.50 (m, 4H), 1.36–1.25 (m, 2H); 13C NMR
calcd for C13H15O4F3NaS [M + Na]+ 347.0535, found 347.0526; (100 MHz, CDCl3): δ 139.7, 136.1, 133.3, 131.3, 129.4, 126.2,
[α]2D2 = +1.8 (c = 1.0, CHCl3, 78% ee). The enantiomeric excess 83.7, 68.9, 30.2, 27.8, 23.0, 21.6, 20.7; IR (neat) 3463, 2941,
was determined by HPLC with a Chiralcel OJ-H column 2865, 1354, 1174, 925, 898, 757 cm−1; HRMS (ESI+) calcd for
(hexane : 2-propanol = 90 : 10, 1.0 mL min−1, 254 nm); minor C13H17BrO4NaS [M + Na]+ 372.9903, found 372.9895; [α]2D2
enantiomer tR = 10.1 min, major enantiomer tR = 7.6 min, +2.6 (c = 1.0, CHCl3, 80% ee). The enantiomeric excess was
=
78% ee.
determined by HPLC with a Chiralpak AD-3 column (hexane :
(1R,2S)-2-Hydroxycyclohexyl 3-bromobenzenesulfonate (4f). 2-propanol = 90 : 10, 1.0 mL min−1, 254 nm); minor enantio-
Reaction time: 13 h; colorless oil (52.9 mg, 77% yield); mer tR = 15.8 min, major enantiomer tR = 12.9 min, 80% ee.
1H NMR (400 MHz, CDCl3): δ 8.09 (t, J = 1.8 Hz, 1H), 7.89–7.86
(1R,2S)-2-Hydroxycyclohexyl 3,4-dichlorobenzenesulfonate
(m, 1H), 7.80–7.77 (m, 1H), 7.44 (t, J = 7.9 Hz, 1H), 4.73–4.69 (4j). Reaction time: 13 h; colorless oil (55.7 mg, 84% yield);
(m, 1H), 3.87–3.85 (m, 1H), 1.98–1.92 (m, 1H), 1.79–1.72 (m, 1H NMR (400 MHz, CDCl3): δ 8.03 (d, J = 2.3 Hz, 1H), 7.77 (dd,
1H), 1.70–1.51 (m, 5H), 1.39–1.30 (m, 2H); 13C NMR (100 MHz, J = 8.4, 2.3 Hz, 1H), 7.64 (d, J = 8.4 Hz, 1H), 4.75–4.68 (m, 1H),
CDCl3): δ 138.9, 136.8, 130.7, 130.5, 126.2, 123.1, 83.9, 69.1, 3.88–3.85 (m, 1H), 2.05–1.95 (m, 2H), 1.81–1.52 (m, 5H),
30.1, 27.9, 21.5, 20.8; IR (neat) 3550, 2940, 2860, 1355, 1178, 1.39–1.24 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 136.7, 136.9,
927, 900 cm−1; HRMS (ESI+) calcd for C12H19O4BrS [M + NH4]+ 133.8, 131.3, 129.6, 126.6, 84.3, 69.0, 30.3, 27.9, 21.5, 20.8;
354.0198, found 354.0187; [α]2D3 = –9.0 (c = 0.5, CHCl3, 73% ee). IR (neat) 3430, 2935, 2859, 1365, 1174, 925 cm−1; HRMS (ESI+)
The enantiomeric excess was determined by HPLC with calcd for C12H14O4Cl2NaS [M + Na]+ 346.9882, found 346.9874;
a
Chiralcel OJ-H column (hexane : 2-propanol
1.0 mL min−1, 254 nm); minor enantiomer tR = 27.6 min, was determined by HPLC with a Chiralpak AD-3 column
major enantiomer tR = 24.7 min, 73% ee.
(hexane : 2-propanol = 90 : 10, 1.0 mL min−1, 254 nm); minor
=
90 : 10, [α]2D2 = +0.4 (c = 1.0, CHCl3, 77% ee). The enantiomeric excess
(1R,2S)-2-Hydroxycyclohexyl 3-fluorobenzenesulfonate (4g). enantiomer tR = 14.3 min, major enantiomer tR = 12.1 min,
Reaction time: 13 h; colorless oil (52.4 mg, 95% yield); 77% ee.
1H NMR (400 MHz, CDCl3): δ 7.75 (d, J = 7.9 Hz, 1H), 7.65 (td,
(1R,2S)-2-Hydroxycyclohexyl naphthalene-2-sulfonate (4k).
J = 7.9, 2.3 Hz, 1H), 7.67–7.64 (m, 1H), 7.37 (dt, J = 3.4, 8.3 Hz, Reaction time: 14 h; white solids (52.5 mg, 85% yield);
1H), 4.76–4.69 (m, 1H), 3.87–3.85 (m, 1H), 2.10–1.91 (m, 2H), 1H NMR (400 MHz, CDCl3): δ 8.52 (d, J = 1.6 Hz, 1H), 8.00 (dd,
1.81–1.72 (m, 1H), 1.70–1.50 (m, 4H), 1.37–1.24 (m, 2H); J = 8.4, 2.7 Hz, 2H), 7.94 (d, J = 8.2 Hz, 1H), 7.89 (dd, J = 8.6,
13C NMR (100 MHz, CDCl3): δ 162.2 (d, J = 253.9 Hz), 139.0, 1.8 Hz, 1H), 7.71–7.63 (m, 2H), 4.72–4.67 (m, 1H), 3.89–3.84
131.1, 123.4, 121.0 (d, J = 21.1 Hz), 115.0 (d, J = 24.9 Hz), 84.0, (m, 1H). 1.98–1.90 (m, 1H), 1.87 (br, 1H), 1.79–1.72 (m, 1H),
68.9, 30.1, 27.8, 21.5, 20.7; IR (neat) 3588, 3020, 2940, 1.68–1.48 (m, 4H), 1.34–1.25 (m, 2H); 13C NMR (100 MHz,
1365, 1220, 1173, 921, 755 cm−1; HRMS (ESI+) calcd for CDCl3): δ 135.2, 133.8, 131.9, 129.7, 129.4, 128.0, 127.8, 83.5,
C12H19O4NFS [M + NH4]+ 292.1013, found 292.1013; [α]2D3
=
69.0, 30.2, 27.8, 21.7, 20.7; IR (neat) 3523, 2940, 2865,
+1.3 (c = 1.0, CHCl3, 82% ee). The enantiomeric excess was 1350, 1173, 664 cm−1; HRMS (ESI+) calcd for C16H22O4NS
determined by HPLC with a Chiralpak AD-3 column (hexane : [M + NH4]+ 324.0264, found 324.1260; [α]D23 = +0.4 (c =
2-propanol = 90 : 10, 1.0 mL min−1, 254 nm); minor enantio- 1.0, CHCl3, 84% ee). The enantiomeric excess was determined
mer tR = 19.9 min, major enantiomer tR = 15.6 min, 82% ee.
by HPLC with a Chiralcel OJ-H column (hexane : 2-propanol =
(1R,2S)-2-Hydroxycyclohexyl 2-methylbenzenesulfonate (4h). 90 : 10, 1.0 mL min−1, 254 nm); minor enantiomer tR
Reaction time: 14 h; colorless oil (54.1 mg, 95% yield); 28.4 min, major enantiomer tR = 19.3 min, 84% ee.
=
1H NMR (400 MHz, CDCl3): δ 8.01 (d, J = 8.4 Hz, 1H), 7.53 (t,
(1R,2S)-2-Hydroxycyclohexyl naphthalene-1-sulfonate (4l).
J = 7.5 Hz, 1H), 7.37–7.30 (m, 2H), 4.65–4.61 (m, 1H), 3.89 (br, Reaction time: 13 h; white solids (54.6 mg, 89% yield);
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2019

View Article Online
Organic & Biomolecular Chemistry
Paper
1H NMR (400 MHz, CDCl3): δ 8.64 (dd, J = 8.6, 0.9 Hz, 1H),
8.31 (dd, J = 7.4, 1.4 Hz, 1H), 7.97 (d, J = 8.3 Hz, 1H), 7.73 (dt,
J = 7.9, 1.4 Hz, 1H), 7.64 (dt, J = 7.5, 1.1 Hz, 1H), 7.58 (t, J =
7.9 Hz, 1H), 4.65–4.61 (m, 1H), 3.73–3.71 (m, 1H), 1.93–1.79
(m, 2H), 1.74–1.49 (m, 4H), 1.45–1.37 (m, 1H), 1.30–1.17
(m, 2H); 13C NMR (100 MHz, CDCl3): δ 135.3, 134.1, 132.2,
130.0, 129.0, 128.7, 128.3, 127.2, 124.6, 124.1, 83.8, 69.0, 30.2,
4 (a) S. J. Baker, C. Z. Ding, T. Akama, Y.-K. Zhang,
V. Hernandez and Y. Xia, Future Med. Chem., 2009, 1, 1275;
(b) V. M. Dembitsky, A. A. A. Al Quntar and M. Srebnik,
Chem. Rev., 2011, 111, 209; (c) R. T. Jacobs, J. J. Plattner and
M. Keenan, Curr. Opin. Infect. Dis., 2011, 24, 586;
(d) S. J. Baker, J. W. Tomsho and S. J. Benkovic, Chem. Soc.
Rev., 2011, 40, 4279; (e) G. A. Ellis, M. J. Palte and
R. T. Raines, J. Am. Chem. Soc., 2012, 134, 3631; (f) J. Q. Del
Rosso and J. J. Plattner, J. Clin. Aesthet. Dermatol., 2014, 7,
13; (g) C. T. Liu, J. W. Tomsho and S. J. Benkovic, Bioorg.
Med. Chem., 2014, 22, 4462.
27.7, 21.6, 20.8; IR (neat) 3397, 2935, 1343, 1170, 757 cm−1
;
HRMS (ESI+) calcd for C16H18O4NaS [M + Na]+ 329.0818, found
329.0813; [α]2D2 = +10.0 (c = 1.0, CHCl3, 76% ee). The enantio-
meric excess was determined by HPLC with a Chiralpak AS-H
column (hexane : 2-propanol = 90 : 10, 1.0 mL min−1, 254 nm);
5 J. Zhang, M. Zhu, Y. Lin and H. Zhou, Sci. China: Chem.,
2013, 56, 1372.
minor enantiomer tR = 27.7 min, major enantiomer tR
=
24.9 min, 76% ee.
6 (a) K. L. Bicker, J. Sun, J. J. Lavigne and P. R. Thompson,
ACS Comb. Sci., 2011, 13, 232; (b) R. Zhang, Y.-D. Zhang,
L.-X. Wang, C.-H. Ge, Z.-Y. Ma, J.-P. Miao and X.-D. Zhang,
Inorg. Chem. Commun., 2016, 74, 52.
7 use of benzoxaboroles as reaction promotors, see:
K. Oshima and Y. Aoyama, J. Am. Chem. Soc., 1999, 121,
2315.
8 For boronic acid derivative-catalyzed reactions, see:
(a) K. Ishihara, S. Ohara and H. Yamamoto, J. Org. Chem.,
1996, 61, 4196; (b) E. Dimitrijević and M. S. Taylor,
ACS Catal., 2013, 3, 945; (c) H. Zheng and D. G. Hall,
Aldrichimica Acta, 2014, 47, 41; (d) M. S. Taylor, Acc. Chem.
Res., 2015, 48, 295.
9 Lewis acid catalysis, see: (a) K. Ishihara and H. Yamamoto,
Eur. J. Org. Chem., 1999, 527; (b) K. Ishihara, in Lewis Acids
in Organic Synthesis, ed. H. Yamamoto, Wiley-VCH,
Weinheim, 2000, vol. 1, p. 89; (c) K. Ishihara and
H. Yamamoto, in Modern Aldol Reactions, ed. R. Mahrwald,
Wiley-VCH, Weinheim, 2004, p. 25.
(1R,6S)-6-Hydroxycyclohex-3-en-1-yl benzenesulfonate (4m).
Reaction time: 14 h; colorless oil (27.7 mg, 92% yield);
1H NMR (400 MHz, CDCl3): δ 7.82 (d, J = 8.4 Hz, 2H), 7.36 (d,
J = 8.4 Hz, 2H), 5.60–5.51 (m, 1H), 5.51–5.46 (m, 1H), 4.78–4.75
(m, 1H), 4.05–4.03 (m, 1H), 2.46 (s, 3H), 2.44–2.64 (m, 1H),
2.30–2.22 (m, 2H), 2.09 (d, J = 5.7 Hz, 1H); 13C NMR (100 MHz,
CDCl3): δ 144.9, 133.9, 129.9, 127.7, 123.9, 122.4, 80.6, 67.1,
31.5, 28.5, 21.7; IR (neat) 3517, 3038, 2919, 1604, 1354, 1180,
914, 881, 745, 669 cm−1; HRMS (ESI+) calcd for C13H16O4NaS
[M + Na]+ 291.0662, found 291.0656; [α]2D2 = +7.8 (c = 1.0,
CHCl3, 76% ee). The enantiomeric excess was determined by
HPLC with a Chiralcel OJ-H column (hexane : 2-propanol =
90 : 10, 1.0 mL min−1, 254 nm); minor enantiomer tR
18.0 min, major enantiomer tR = 20.4 min, 76% ee.
=
Conflicts of interest
There are no conflicts to declare.
10 DATB catalyst having an azaborine ring, see: (a) H. Noda,
M. Furutachi, Y. Asada, M. Shibasaki and N. Kumagai, Nat.
Chem., 2017, 9, 571; (b) H. Noda, Y. Asada, M. Shibasaki
and N. Kumagai, Chem. Commun., 2017, 53, 7447;
(c) Z. Liu, H. Noda, M. Shibasaki and N. Kumagai, Org.
Lett., 2018, 20, 612; (d) H. Noda, Y. Asada, M. Shibasaki
and N. Kumagai, J. Am. Chem. Soc., 2019, 141, 1546.
11 D. Lee and M. S. Taylor, J. Am. Chem. Soc., 2011, 133, 3724.
12 (a) L. Chan and M. S. Taylor, Org. Lett., 2011, 13, 3090;
(b) C. Gouliaras, D. Lee, L. Chan and M. S. Taylor, J. Am.
Chem. Soc., 2011, 133, 13926; (c) D. Lee, C. L. Williamson,
L. Chan and M. S. Taylor, J. Am. Chem. Soc., 2012, 134,
8260; (d) E. Dimitrijevic and M. S. Taylor, Chem. Sci., 2013,
4, 3298; (e) K. A. D’Angelo and M. S. Taylor, J. Am. Chem.
Soc., 2016, 138, 11058.
Acknowledgements
This work was financially supported by the Toray Award in
Synthetic Organic Chemistry, Japan and the JSPS KAKENHI
Grant Number 15K18841.
Notes and references
1 (a) A. Adamczyk-Wozniak, M. K. Cyranski, A. Zubrowska
and A. Sporzynski, J. Organomet. Chem., 2009, 694, 3533;
(b) A. Adamczyk-Wozniak, K. M. Borys and A. Sporzynski,
Chem. Rev., 2015, 115, 5224.
2 (a) Boronic Acids: Preparation and Applications in Organic 13 For reviews, see: (a) M. D. Díaz-de-Villegas, J. A. Gálvez,
Synthesis, Medicine and Materials, ed. D. G. Hall, Wiley-
VCH, Weinheim, 2011, vol. and 2; (b) Y. Kubo,
R. Nishiyabu and T. D. James, Chem. Commun., 2015, 51,
2005; (c) X. Sun and T. D. James, Chem. Rev., 2015, 115,
8001.
R. Badorrey and M. P. López-Ram-de-Víu, Chem. – Eur. J.,
2012, 18, 13920; (b) L. W. Xu, Y. Chen and Y. Lu, Angew.
Chem., Int. Ed., 2015, 54, 9456; (c) A. Borissov, T. Q. Davies,
S. R. Ellis, T. A. Fleming, M. S. W. Richardson and
D. J. Dixon, Chem. Soc. Rev., 2016, 45, 5474.
1
3 (a) M. Dowlut and D. G. Hall, J. Am. Chem. Soc., 2006, 128, 14 For a chiral catalyst/achiral borinic acid co-catalyst system,
4226; (b) M. Bérubé, M. Dowlut and D. G. Hall, J. Org.
Chem., 2008, 73, 6471.
see: (a) R. Z. Li, H. Tang, K. R. Yang, L. Q. Wan, X. Zhang,
J. Liu, Z. Fu and D. Niu, Angew. Chem., Int. Ed., 2017, 56,
This journal is © The Royal Society of Chemistry 2019
Org. Biomol. Chem.

View Article Online
Paper
Organic & Biomolecular Chemistry
7213; (b) M. Pawliczek, T. Hashimoto and K. Maruoka,
Chem. Sci., 2018, 9, 1231.
M. S. Taylor, Org. Lett., 2009, 11, 5486; (c) T. Hashimoto,
A. O. Gálvez and K. Maruoka, J. Am. Chem. Soc., 2015, 137,
16016; (d) N. Hayama, T. Azuma, Y. Kobayashi and
Y. Takemoto, Chem. Pharm. Bull., 2016, 64, 704;
(e) N. Hayama, R. Kuramoto, T. Földes, K. Nishibayashi,
Y. Kobayashi, I. Pápai and Y. Takemoto, J. Am. Chem. Soc.,
2018, 140, 12216.
15 For enantioselective sulfonylation, see: (a) Y. Demizu,
K. Matsumoto, O. Onomura and Y. Matsumura,
Tetrahedron Lett., 2007, 48, 7605; (b) K. W. Fiori,
A. L. A. Puchlopek and S. J. Miller, Nat. Chem., 2009, 1,
630.
16 (a) X. Sun, H. Lee, S. Lee and K. L. Tan, Nat. Chem., 2013, 19 G. E. Garrett, D. B. Diaz, A. K. Yudin and M. S. Taylor,
5, 790; (b) C. L. Allen and S. J. Miller, Org. Lett., 2013, 15, Chem. Commun., 2017, 53, 1809.
6178; (c) I.-H. Chen, K. G. M. Kou, D. N. Le, C. M. Rathbun 20 (a) N. Mannville, H. Alite, F. Haeffner, A. H. Hoveyda and
and V. M. Dong, Chem. – Eur. J., 2014, 20, 5013.
17 M. Lauer and G. Wulff, J. Organomet. Chem., 1983, 256, 1.
M. L. Snapper, Nat. Chem., 2013, 5, 768; (b) D. Lee and
M. S. Taylor, Org. Biomol. Chem., 2013, 11, 5409.
18 For a chiral boronic acid catalyst, see: (a) K. Arnold, 21 J. Mulzer and B. Schöllhorn, Angew. Chem., Int. Ed. Engl.,
B. Davies, D. Hérault and A. Whiting, Angew. Chem., Int. 1990, 29, 431.
Ed., 2008, 47, 2673; (b) D. Lee, S. G. Newman and 22 Side products were not formed when 1c was applied.
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2019