Methylhydrazine-induced enantioselective α-hydroxylation of β-keto esters with molecular oxygen catalyzed by hydroquinine

Article abstract of DOI:10.1016/j.tet.2014.11.029

Methylhydrazine-induced α-hydroxylation of β-dicarbonyl compounds was achieved using O₂ as the oxygen source. This reaction provides an efficient approach to enantioenriched α-hydroxy β-dicarbonyl compounds, which are valuable substances and widely used in the chemical and pharmaceutical industry. A wide variety of β-keto esters could undergo this oxidation to give the corresponding products in excellent yields (up to 95%) and with good enantioselectivities (up to 85% ee). The mild reaction conditions and the use of molecular oxygen as oxidant make this protocol very environmentally friendly and practical.

Full text of DOI:10.1016/j.tet.2014.11.029

Tetrahedron 71 (2015) 85e90
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Methylhydrazine-induced enantioselective
a
-hydroxylation of
b-keto esters with molecular oxygen catalyzed by hydroquinine
*
Yakun Wang, Ting Xiong, Qingwei Meng
State Key Laboratory of Fine Chemicals, School of Pharmaceutical Science and Technology, Dalian University of Technology, Dalian 116024,
Liaoning Province, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Methylhydrazine-induced
oxygen source. This reaction provides an efficient approach to enantioenriched ɑ-hydroxy
a
-hydroxylation of
b
-dicarbonyl compounds was achieved using O2 as the
-dicarbonyl
compounds, which are valuable substances and widely used in the chemical and pharmaceutical in-
dustry. A wide variety of -keto esters could undergo this oxidation to give the corresponding products in
Received 15 September 2014
Received in revised form 5 November 2014
Accepted 10 November 2014
Available online 15 November 2014
b
b
excellent yields (up to 95%) and with good enantioselectivities (up to 85% ee). The mild reaction con-
ditions and the use of molecular oxygen as oxidant make this protocol very environmentally friendly and
practical.
Keywords:
Methylhydrazine
Ó 2014 Elsevier Ltd. All rights reserved.
b
-Keto esters
Cinchona-alkaloid
Molecular oxygen
Organocatalysis
1. Introduction
keto esters under mild conditions.7 Furthermore, P(OEt)3/O2 sys-
tem has been reported as an efficient combination for enantiose-
Chiral
a
-hydroxy
b
-dicarbonyl compounds represent a func-
lective oxidation of aromatic ketones and oxindoles,8 but the
P(OEt)3/O2 system showed narrow substrate scope possibly be-
cause of the inherent low reactivity to activate O2.
tional and common structural motif in a variety of natural products,
pharmaceuticals, and agrochemicals.1 Furthermore, they have been
used as an important intermediate in the synthesis of the in-
Despite tremendous efforts by many groups, the catalytic
secticide indoxacarb.2 Therefore, the asymmetric
a-hydroxylation
asymmetric
lecular oxygen is still a challenge. Herein we disclose the first
hydroxylation of -dicarbonyl compounds, using O2 as the oxygen
source, through the catalysis by methylhydrazine (H2NNHMe) and
cinchona alkaloid. Enantiomerically -hydroxy- -dicarbonyl
a-hydroxylation of b-dicarbonyl compounds by mo-
of 1,3-dicarbonyl compounds is a significant transformation, which
allows for direct formation of a carboneoxygen bond. A large
number of catalytic systems for asymmetric a-hydroxylation of b-
a-
b
dicarbonyl compounds have been developed over the past two
decades and can be categorized into the following two classes
based on the combination of catalysts and oxidants a) metal com-
plex/active oxidant.3 b) organocatalyst/active oxidant.4 It is worth
mentioning that molecular oxygen has been considered as an ideal
oxidant and an atom-efficient reagent in synthetic chemistry.5 In
recent years, photooxygenation becomes an important oxidation
method using molecular oxygen as oxidant. This oxidation reaction
could be achieved by the activation of O2 with light and photo-
a
a
b
compounds were obtained with excellent yields (up to 95%) and
good enantioselectivities (up to 85% ee).
2. Results and discussions
Hydrazine compounds are useful building blocks in organic
synthesis of pharmaceuticals and pesticides, such as the antitu-
berculosis medication isoniazid and the antifungal fluconazole.9
Furthermore, they are widely used as reducing agent10 and rocket
fuels.11 Recently, methylhydrazine-induced aerobic epoxidation of
ꢀ
sensitizer. In 2004, Cordova and his co-workers first reported
enantioselective photooxygenation of aldehydes and ketones cat-
alyzed by amino-acids6 and our group demonstrated an efficient
b,b
-disubstituted enones has been reported.12 Inspired by these
enantioselective phase-transfer-catalyzed photooxygenation of b-
results, we attempted the reaction of 1-indanone-derived b-keto
ester 1a with commercially available CH3NHNH2 in combination
with Cs2CO3 (Table 1, entry 1). To our delight, 2a was obtained in
80% yield in 6 h. Then we investigated the influence of the base and
hydrazine. The reaction did not take place in the absence of
* Corresponding author. Tel.: þ86 411 84986201; e-mail address: mengqw@dlut.
edu.cn (Q. Meng).
http://dx.doi.org/10.1016/j.tet.2014.11.029
0040-4020/Ó 2014 Elsevier Ltd. All rights reserved.

86
Y. Wang et al. / Tetrahedron 71 (2015) 85e90
Table 1
Hydrazine-induced aerobic asymmetric
a
-hydroxylation of 1a: Optimization of reaction conditionsa
Entry
Hydrazine
Cat.
Base
Solvent
T [h]
T [ꢀC]
Yield [%]b
ee [%]c
1
2
CH3NHNH2
None
d
Cs2CO3
Cs2CO3
none
Cs2CO3
Cs2CO3
Et3N
TMGd
imidazole
d
MTBE
MTBE
MTBE
MTBE
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
6
24
12
12
12
12
6
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
15
80
Nr
Nr
85
89
75
87
73
67
Trace
73
Trace
70
71
50
63
30
51
70
43
Trace
38
65
53
71
85
d
3
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
NH2NH2$H2O
NH2NHCH2CH2OH
NH2NHAc
d
/
4f
PTC-1
Qn
Qn
Qn
Qn
Qn
Qn
Qn
Qn
Qn
Qn
Qn
Cn
Cn1
Qd
HCn
Qn1
Qn2
Qn3
Qn4
Qn5
HQn
HQn
5 (R)e
23 (R)
35 (R)
7 (R)
5
6
7
8
12
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
41 (R)
49 (R)
n.d.
45 (R)
n.d.
35 (R)
40 (R)
48 (R)
43 (S)
5 (S)
37 (S)
45 (S)
17 (S)
n.d.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26g
d
d
d
NH2NHPh
NH2NHCH2Ph
d
d
C6H5NHNHCON]NC6H5
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
CH3NHNH2
d
d
d
d
d
d
d
d
d
d
d
7 (R)
41 (R)
36 (R)
50 (R)
67 (R)
a
The reaction of 1a with hydrazine (3.0 equiv) was carried out in the presence of cat (20 mol %) and base (3.0 equiv) in solvent (2 mL) under air atmosphere at room
temperature.
b
c
Isolated yields.
The enantiomeric excess was determined by HPLC analysis of the product 2a using a chiral column (DAICEL Chiralcel OD-H) with hexane/2-propanol (90:10) as the eluent.
TMG¼Tetramethylguanidine.
d
e
The absolute configuration of the products were determined by comparison of the optical rotation and the HPLC retention time of the corresponding ester with literature
values.4b
f
5 mol % of catalyst.
g
Reaction condition: 1equiv. of b
-keto ester, 1.3 equiv of H2NNHMe and 40 mol % of hydroquinine in CHCl3 at 15 ꢀC.
methylhydrazine or Cs2CO3 (Table 1, entries 2, 3). Next, we explored
the use of cinchona alkaloid phase-transfer catalyst PTC-1 for
use different hydrazines to promote this reaction. Nearly no prod-
ucts were obtained when NH2NH2$H2O and H2NNHAc were used to
replace H2NNHMe (Table 1, entries 10 and 12). However, when
NH2NHCH2CH2OH, NH2NHPh, and NH2NHCH2Ph were applied to
enantioselective
a-hydroxylation, but the enantioselectivity was
quite poor (Table 1, entry 4). To our delight, when we use natural
cinchona alkaloid Qn as catalyst, the ee value of 2a was increased to
23% (Table 1, entry 5). Prompted by this result, we investigated the
influence of different bases. Tetramethylguanidine promoted the
reaction but afforded almost racemic product (Table 1, entry 7).
Triethylamine, imidazole were also tested but the desired product
was obtained with moderate ee values (Table 1, entries 6 and 8).
These results indicated that the choice of base was crucial to ach-
this asymmetric
a-hydroxylation, the oxidation product 2a was
obtained in good yields (70%e83%) with moderate ee values (35%e
45%) (Table 1, entries 11, 13, and 14). C6H5NHNHCON]NC6H5 could
lead to the formation of 2a with good enantioselectivity (48%) but
in poor yield (Table 1, entry 15). These results showed that the re-
activity of the hydrazines is possibly related to electron density of
the nitrogen atom. H2NNHMe, NH2NHCH2CH2OH, and
NH2NHCH2Ph bearing electron donating groups (eCH3,
eCH2CH2OH, and eCH2Ph) provided better results than other hy-
drazines. In consideration of atom economy, yield and enantiose-
lectivity of the product, H2NNHMe was selected as the oxygen
ieve good yields and ee values. We were surprised to find that the a-
hydroxylation also took place efficiently with only a catalytic
amount of Qn, through reaction time was extended to 24 h (Table 1,
entry 9). Shibata reported that methylhydrazine is indispensable
for aerobic epoxidation and this phenomenon would not have been
discovered using other hydrazine derivatives.12 We attempted to
activation substance for this
a-hydroxylation. After that, we
screened different cinchona alkaloids as organocatalysts under

Y. Wang et al. / Tetrahedron 71 (2015) 85e90
87
Table 2
certain reaction conditions. Cinchonine (Cn) provided the oxidation
Substrate scope in the asymmetric a-hydroxylation of b
-keto estersa
product 2b in 63% yield and with 43% ee (S) (Table 1, entry 16).
Quinidine (Qd) was also tested and 2a was obtained in 51% yield
and with 37% ee (S) (Table 1, entry 18). Cn-1(epi-9-amino-(9-
deoxy)-cinchonine) gave the
a-hydroxylation product with poor
yield and ee value (Table 1, entry 17). Hydrocinchonine (HCn) was
then introduced, providing a slightly higher ee value and yield
compared with cinchonine (Cn) (Table 1, entry 19). Several Qn
derivatives with modification at C-60 and C-9 were investigated.
Qn-1, bearing a benzyl ether group at C-9 position, provided 2a in
43% yield and with 17% ee (Table 1, entry 20). The di-ether de-
rivative Qn-2 could not promote this reaction (Table 1, entry 21).
The di-hydroxyl derivative Qn-3 was not an effective catalyst for
this reaction, either (Table 1, entry 22). We also investigated the
Entry
Sub
n
R1
R2
Yield [%]b
ee [%]c
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Cl
6-Me
6-MeO
6-F
6-Br
Me
Me
Me
Me
Me
Me
Me
Me
85
78
69
81
85
82
75
71
Trace
72
67
73
78
75
71
95
67
65
78
67
64
68
66
67
Nd
66
75
61
58
60
55
85
impact of C-60 substituent group on this
a-hydroxylation. Neither
an isopropyl (Qn-4) nor a more bulky triisopropylsilyloxy sub-
stituent at this position (Qn-5) could enhance the enantiose-
lectivity and yield (Table 1, entries 23 and 24). To our delight, ee
value was improved to 50% when hydroquinine (HQn) was used as
the catalyst (Table 1 entry 25). After selecting HQn as the catalyst
for this transformation, we optimized the reaction conditions such
as the solvent, temperature, substrate concentration, catalyst
loading and methylhydrazine dosage and others (See
Supplementary data for details). The optimal reaction conditions
required the use of 40 mol % hydroquinine (HQn), 1.3 equiv of
H2NNHMe in CHCl3 at 15 ꢀC in air, 24 h (Table 1, entry 26).
5-Br
4-MeO
5,6-diMeO
H
H
H
H
H
H
H
9d
10
11
12
13
14
15
16
Me
Et
C(Et)3
CH(CH3)2
t-Bu
Bn
1Ad
C(Ph)2CH3
Under the optimized reaction conditions (1 equiv of
ter, 1.3 equiv of H2NNHMe and 40 mol % of hydroquinine in CHCl3 at
15 ꢀC, in air, 24 h), a range of
-keto esters were further in-
vestigated, and the results were outlined in Table 2. A series of
indone methyl esters (1ae1h) bearing different substituents, such
as methyl, methoxy, chloro, bromo groups at the phenyl ring could
be converted into the corresponding products 2ae2h in good yields
(71e85%) and with 64e78% ee (Table 2, entries 1e8). Interestingly,
b-keto es-
17
18
1q
1r
1
1
H
H
82
81
73
72
b
19d
20d
1s
1t
2
d
H
d
CH3
d
Trace
Trace
Nd
Nd
a
Unless otherwise noted, the reaction was carried out with 1equiv. of b-keto
ester, 1.3 equiv of H2NNHMe and 40 mol % of hydroquinine in CHCl3 at 15 ꢀC.
5,6-dimethoxy b-keto ester 1i did not give the oxidation product,
b
Isolated yield.
Determined by HPLC.
Monitored by TLC.
possibly due to the inherently low reactivity of 1i. The effect of the
ester group of indanone derivatives on this asymmetric process was
also investigated.
c
d
The yield and enantioselectivity from ethyl ester (1j) was
slightly lower than the methyl ester (Table 2, entry 10). When the
methyl group was replaced by 3-ethyl amyl, the ee value was im-
proved to 75% with a little sacrifice of yield (Table 2, entry 11). The
isopropyl, tert-butyl, 1-Ad, and benzyl groups were also in-
78% yield with high enantioselectivity (65% ee). It is worth men-
tioning that the catalyst hydroquinine (HQn) was recovered in 86%
yield by flash chromatography and the recovered catalyst could be
reused in the model reaction (Table 2, entry 1), giving identical
yield and enantioselectivity.
vestigated. The a-hydroxylation of these substrates gave the cor-
In order to understand the reaction mechanism, we designed
some control experiments. The yield and enatioselectivity of 2a
were slightly better under an O2 atmosphere than under air, and
responding 21-2o in good yields (71e78%) and with high ee values
(55e61%) (Table 2, entries 12e15). Interestingly, when R2 was
changed to eC(Ph)2CH3, the ee value was significantly improved to
85% and the yield of 2p was excellent (Table 2, entry 16). We then
tested some substrates with steric hindrance group. 1q bearing a 9-
anthracenylmethyl afforded the corresponding product 2r in 81%
yield and with 72% ee (Table 2, entry 18). Similarly, 2q was obtained
in 82% yield and with 73% ee (Table 2, entry 17). Overall, this
method showed good substrate suitability. The scope of the re-
action was further probed for six-membered cyclic substrate 1s, as
well as acyclic substrate 1t. Under the optimized reaction condi-
reaction time could be shortened (Table 3, entry 1). The
a-hy-
droxylation did not occur under a nitrogen atmosphere(Table 3,
entry 2). Furthermore, the addition of water to the reaction system
could not promote this transformation (Table 3, entry 3). These
results clearly indicate that the oxygen atom in the hydroxylation
product originates from molecular oxygen in air. It was reported
that in the presence of hydrazine and O2 and base, hydrogen per-
oxide could be formed through a single-electron transfer proc-
ess.13e15 When 30% H2O2 was used instead of the H2NNHMe/air
system, lower ee value and chemical yield were observed (Table 3,
entry 4). We then tested the H2NNHMe/air system with additional
H2O. Interestingly, the reaction could provide 2a with similar
enantioselectivity and yield compared with 30% H2O2 system (Table
3, entry 5). The reaction proceeded well in the presence of the
singlet oxygen inhibitor 1,4-diazabicyclo[2,2,2] octane (DABCO)
(Table 3, entry 6). Furthermore, the reaction also worked well in the
dark (Table 3, entry 8). These results suggest singlet molecular
oxygen was not involved in this transformation. However, when
2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was added, nearly
tions, tetralone
uct, nor did the simple acyclic
20). The inherently lower reactivity of the two substrates led to no
oxidation under this method. In addition, the activity of -hydrogen
atom is so weak that our catalyst is not alkaline enough to activate
the -hydrogen atom. To test the generality of our asymmetric
b
-keto esters (1s) did not give the oxidation prod-
b
-keto ester 1t (Table 2, entries 19,
a
a
oxidation, a 1.12 g sample of indanone carboxylate 1a was treated
with H2NNHMe (1.3 equiv) in 200 mL CHCl3 under the above op-
timized conditions of catalyst Hydroquinine (HQn) loading of
40 mol % on a gram-quantity scale. After stirring 24 h at 15 ꢀC, the
a-
hydroxylation product 3b was obtained by flash chromatography in

88
Y. Wang et al. / Tetrahedron 71 (2015) 85e90
Table 3
3. Conclusion
Some control experimentsa
In
summary,
an
efficient
-hydroxylation of
and
enantioselective
b-keto esters has
methylhydrazine-induced
a
been developed under mild conditions. This transformation is
applicable to a range of -keto esters, providing the desired
products in high yields and with good enantioselectivities. The
hydroxydicarbonyl compounds are highly valued chemicals and
widely used in the chemical and pharmaceutical industry. Mo-
lecular oxygen in air, the most environmentally friendly oxidant,
was employed at room temperature and many kinds of hydrazines
could promote this reaction. Further work on the application of
this methylhydrazine-induced asymmetric oxidation reaction is
currently underway.
b
Entry
Conditions
Yield [%]b
ee [%]c
a
-
1d
2e
3e
4f
5
6
7
8
O2
Nitrogen
87
Nr
Nr
50
58
84
<5
82
68
d
Nitrogenþ5equiv of H2O
30% H2O2 (1.3 equiv)
H2O (0.7 equiv)
DABCO (0.5 equiv)
TEMPO (1.0 equiv)
Without light
d
53
51
54
nd
67
a
Unless otherwise noted, the reaction was carried out with 1 equiv of b-keto
ester, 1.3 equiv of H2NNHMe and 40 mol % of hydroquinine in CHCl3 at 15 ꢀC.
b
Isolated yield.
Determined by HPLC.
Reaction time:12 h.
Monitored by TLC.
4. Experimental
4.1. General
c
d
e
f
The reaction was carried out in the absence of H2NNHMe under nitrogen at-
mosphere (Fig. 1).
Unless otherwise stated, all commercial reagents and solvents
were used without further additional purification. Analytical TLC
was visualized with UV light at 254 nm. Thin layer chromatography
no oxidation product was obtained, indicating a possible radical
mechanism (Table 3, entry 7).
was carried out on TLC aluminum sheets with silica gel 60 F254
.
Purification of reaction products was carried out with chromatog-
raphy on silica gel 60 (200e400 mesh). Melting points were de-
termined with a hot plate apparatus. Optical rotations were
measured on a digital polarimeter with a sodium lamp at room
temperature. 1H NMR (400 MHz) or (500 MHz) spectra were ob-
tained at 25 ꢀC; 13C NMR (101 MHz) were recorded on a VARIAN
INOVA-400M and AVANCE II 400 spectrometer at 25 ꢀC. Chemical
Based on the above observations, we propose the reaction
mechanism as shown in Fig. 2. First, H2NNHMe reacted with mo-
lecular oxygen through a single-electron transfer to generate hy-
drogen peroxide. Different from Shibata’s work,15 in which
stoichiometric Cs2CO3 was used to promote the epoxidation, HQn
was used not only as an organocatalyst, but also as a base in our case.
Moreover, several other hydrazines including NH2NHCH2CH2OH,
NH2NHPh, NH2NHCH2Ph, and C6H5NHNHCON]NC6H5 could pro-
shifts are reported as
d (ppm) values relative to TMS as internal
standard and coupling constants (J) in Hz. The enantiomeric ex-
cesses (ee) were determined by chiral HPLC. HPLC analyses were
performed with Diacel Chiralpak AD-H, OD-H and AS-H chiral
column (0.46 cmꢁ25 cm), using mixtures of n-hexane/isopropyl
alcohol as mobile phase at 25 ꢀC.
mote this
tended the application of this method At the second step, the
generated H2O2 reacted with the substrates, affording -hydroxyl-
a-hydroxylation (Table 1, entries 11, 13e15), which ex-
a
ation products along with 1 equiv of water. The lower chemical yield
of 3a when using 30% H2O2 instead of the H2NNHMe/air system
(entry 5, Table 3) might be explained by the purity of H2O2, since our
H2NNHMe/air system generates highly reactive and pure H2O2.
4.2. General procedure for
a-hydroxylation of b-keto esters
To a solution of -keto ester 1 (0.1 mmol) and catalyst HQn
b
(1.3 mg, 0.04 mmol, 40 mol %) in chloroform (2 mL) was added
H2NNHMe (0.13 M in chloroform solution, 1.3 equiv, 2 mL). The
resulting mixture was stirred at 15 ꢀC for 24 h. The reaction was
monitored by TLC, and the solvent was removed under reduced
pressure upon the completion of the reaction. The residue was
purified by flash chromatography (silica gel; petroleum ether/ethyl
acetate¼13:1e5:1) to afford products.
Fig. 1. Asymmetric
alkaloid/air/system.
a-hydroxylation of b-keto esters by a methylhydrazine/cinchona
4.2.1. Methyl 2-hydroxy-5-chloro-1-oxo-2,3-dihydro-1H-indene-2-
carboxylate (2a). White solid (18.6 mg, 85% yield); [
a
]
25ꢂ61.5 (c
D
0.07, CHCl3, 67% ee); mp 134e136 ꢀC; 1H NMR (500 MHz, CDCl3)
d
7.74 (d, J¼8.2 Hz, 1H), 7.50 (d, J¼0.7 Hz,1H), 7.43 (dd, J¼8.2, 0.8 Hz,
1H), 3.75 (s, 3H), 3.71 (d, J¼17.4 Hz, 1H), 3.24 (d, J¼17.4 Hz, 1H). 13
C
NMR (126 MHz, CDCl3)
d 199.36, 171.53, 153.53, 142.89, 131.99,
129.09, 126.77, 126.40, 80.43, 53.62, 38.95. HPLC conditions: Chir-
alcel OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/
min, 254 nm,
s
R (major)¼10.4 min, R (minor)¼8.8 min.
s
4.2.2. Methyl 2-hydroxy-6-methyl-1-oxo-2,3-dihydro-1H-indene-2-
25
carboxylate (2b). White solid (15.9 mg, 78% yield); [
a]
ꢂ46.2 (c
D
0.04, CHCl3, 65% ee); mp132e134 ꢀC; 1H NMR (500 MHz, CDCl3)
d
7.60 (s, 1H), 7.50 (d, J¼7.8 Hz, 1H), 7.38 (d, J¼7.8 Hz, 1H), 3.74 (s,
3H), 3.68 (d, J¼17.1 Hz, 1H), 3.21 (d, J¼17.1 Hz, 1H), 2.42 (s, 3H). 13
C
NMR (101 MHz, CDCl3)
d 201.03, 172.21, 149.79, 138.44, 137.68,
Fig. 2. Mechanism for methylhydrazine-induced enantioselective
-keto esters.
a-hydroxylation of
b
133.84, 126.31, 125.38, 80.89, 53.64, 39.11, 21.28. HPLC conditions:

Y. Wang et al. / Tetrahedron 71 (2015) 85e90
89
Chiralcel OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10,
1 mL/min, 254 nm, R (minor)¼10.7 min.
R (major)¼12.4 min,
J¼7.6, 1.1 Hz,1H), 7.50 (d, J¼7.7 Hz, 1H), 7.47e7.41 (m, 1H), 4.30e4.13
(m, 2H), 3.73 (d, J¼17.2Hz,1H), 3.26(d, J¼17.2Hz,1H),1.19 (t, J¼7.1 Hz,
s
s
3H).13C NMR (126MHz, CDCl3)
d 200.97,171.47,152.30,136.12,133.61,
4.2.3. Methyl 2-hydroxy-6-methoxy-1-oxo-2,3-dihydro-1H-indene-
128.12, 126.46, 125.29, 80.32, 62.79, 39.30, 13.97. HPLC conditions:
2-carboxylate (2c). Yellow solid (15.2 mg, 69% yield); [
a
]
D
25 ꢂ38.6 (c
Chiralcel OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10,1 mL/
0.06, CHCl3, 78% ee); mp 118e120 ꢀC; 1H NMR (500 MHz, CDCl3)
min, 254 nm,
s
R (major)¼11.0 min, R (minor)¼9.6 min.
s
d
7.39 (d, J¼8.3 Hz, 1H), 7.28 (m, 1H), 7.21 (d, J¼8.6 Hz, 1H), 3.84 (s,
3H), 3.75 (s, 3H), 3.65 (d, J¼16.9 Hz, 1H), 3.18 (d, J¼16.9 Hz, 1H). 13
C
4.2.10. 3-Ethyl amyl 2-hydroxy-1-oxo-2,3-dihydro-1H-ind-ene-2-
25
NMR (126 MHz, CDCl3)
d
200.85, 172.04, 159.85, 145.22, 134.66,
carboxylate (2k). Colorless oil (18.4 mg, 67% yield); [
a]
ꢂ23.5 (c
D
127.23, 125.77, 106.19, 81.04, 55.69, 53.57, 38.67. HPLC conditions:
0.05, CHCl3, 75% ee); 1H NMR (500 MHz, CDCl3)
d
7.80 (d, J¼7.7 Hz,
Chiralcel OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10,
1H), 7.65 (td, J¼7.6, 1.1 Hz, 1H), 7.48 (d, J¼7.7 Hz, 1H), 7.42 (t,
J¼7.5 Hz, 1H), 4.04 (s, 1H), 3.64 (d, J¼17.0 Hz, 1H), 3.26 (d, J¼17.0 Hz,
1H), 1.70 (q, J¼7.5 Hz, 6H), 0.65 (t, J¼7.5 Hz, 9H). 13C NMR (126 MHz,
1 mL/min, 254 nm,
s
R (major)¼15.6 min, R (minor)¼13.8 min.
s
4.2.4. Methyl 2-hydroxy-6-fluorine-1-oxo-2,3-dihydro-1H-indene-2-
CDCl3) d 201.47, 170.12, 152.16, 135.80, 134.20, 127.98, 126.21, 124.97,
25
carboxylate (2d). White solid (16.8 mg, 81% yield); [
a
]
ꢂ46.5 (c
92.17, 80.76, 39.66, 26.87, 7.40. HPLC conditions: Chiralcel AS-H
column (250ꢁ4.6 mm), hexane/i-PrOH¼80/20, mL/min,
254 nm, R (minor)¼10.9 min.
R (major)¼9.1 min,
D
0.09, CHCl3, 67% ee); mp 130e132 ꢀC; 1H NMR (500 MHz, CDCl3)
1
d
7.56e7.35 (m, 3H), 3.76 (s, 3H), 3.69 (d, J¼17.1 Hz, 1H), 3.22 (d,
s
s
J¼17.1 Hz, 1H). 13C NMR (101 MHz, CDCl3)
¼200.10, 200.07, 171.57,
d
163.75, 161.27, 147.68, 147.66, 135.26, 135.18, 127.99, 127.92, 124.05,
123.81, 111.12,110.90, 81.04, 53.57, 38.79. HPLC conditions: Chiralcel
OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min,
4.2.11. Isopropyl 2-hydroxy-1-oxo-2,3-dihydro-1H-ind-ene-2-
25
carboxylate (2l). White solid (15.9 mg, 73% yield); [
a]
ꢂ30.9 (c
D
0.06, CHCl3, 61% ee); mp 68e74 ꢀC; 1H NMR (500 MHz, CDCl3)
d
7.80
254 nm,
s
R (major)¼13.0 min,
s
R (minor)¼10.9 min.
(d, J¼7.7 Hz,1H), 7.67 (td, J¼7.6,1.0 Hz,1H), 7.49 (d, J¼7.7 Hz,1H), 7.43
(dd, J¼11.1, 3.9 Hz, 1H), 5.19e4.94 (m, 1H), 3.70 (d, J¼17.2 Hz, 1H),
3.24 (d, J¼17.2 Hz, 1H), 1.20 (d, J¼6.3 Hz, 3H), 1.13 (d, J¼6.3 Hz, 3H).
4.2.5. Methyl 2-hydroxy-6-bromine-1-oxo-2,3-dihydro-1H-indene-
2-carboxylate (2e). Yellow solid (22.9 mg, 85% yield); [
a
]
25 ꢂ28.3 (c
13C NMR (126 MHz, CDCl3)
d 201.02, 171.02, 152.35, 136.03, 133.67,
D
0.10, CHCl3, 64% ee); mp 119e121 ꢀC; 1H NMR (500 MHz, CDCl3)
128.07, 126.41, 125.23, 80.30, 70.91, 39.27, 21.54, 21.34. HPLC con-
d
7.92 (d, J¼1.8 Hz, 1H), 7.78 (dd, J¼8.2, 1.9 Hz, 1H), 7.39 (d, J¼8.2 Hz,
ditions: Chiralcel OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/
1H), 3.75 (s, 3H), 3.67 (d, J¼17.4 Hz, 1H), 3.20 (d, J¼17.4 Hz, 1H). 13
C
10, 1 mL/min, 254 nm,
s
R (major)¼8.7 min, R (minor)¼7.8 min.
s
NMR (101 MHz, CDCl3)
d 199.52, 171.49, 150.67, 138.94, 135.35,
128.13, 128.03, 122.30, 80.61, 53.67, 38.92. HPLC conditions: Chir-
4.2.12. tert-Butyl 2-hydroxy-1-oxo-2,3-dihydro-1H-ind-ene-2-
alcel OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/
carboxylate (2m). White solid (18.0 mg, 78% yield); [
a]
25ꢂ29.5 (c
D
min, 254 nm,
s
R (major)¼14.1 min,
s
R (minor)¼11.8 min.
0.06, CHCl3, 58% ee); mp 128e129 ꢀC; 1H NMR (500 MHz, CDCl3)
d
7.79 (d, J¼7.7 Hz, 1H), 7.64 (d, J¼7.5 Hz, 1H), 7.48 (d, J¼7.7 Hz, 1H),
7.42 (t, J¼7.5 Hz, 1H), 3.65 (d, J¼17.1 Hz, 1H), 3.22 (d, J¼17.1 Hz, 1H),
1.36 (s, 9H). 13C NMR (126 MHz, CDCl3)
201.37, 170.55, 152.33,
4.2.6. Methyl 2-hydroxy-1-oxo-2,3-dihydro-1H-indene-2-
25
carboxylate (2f). Colorless solid (15.5 mg, 82% yield); [
a
]
ꢂ56.1
d
D
(c 0.08, CHCl3, 68% ee); mp 134e136 ꢀC; 1H NMR (500 MHz, CDCl3)
135.86, 133.93, 127.95, 126.28, 125.08, 83.95, 83.51, 80.54, 80.11,
39.44, 27.70. HPLC conditions: Chiralcel OD-H column
(250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min, 254 nm, sR
(major)¼6.8 min, sR (minor)¼6.3 min.
d
7.81 (d, J¼7.7 Hz, 1H), 7.68 (t, J¼7.5 Hz, 1H), 7.50 (d, J¼7.7 Hz, 1H),
7.44 (t, J¼7.5 Hz, 1H), 3.78e3.69 (m, 4H), 3.26 (d, J¼17.2 Hz, 1H). 13
C
NMR (126 MHz, CDCl3)
d 200.82, 171.93, 152.21, 136.21, 133.54,
128.19, 126.49, 125.36, 80.38, 53.50, 39.26. HPLC conditions: Chir-
alcel OD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼80/20, 1 mL/
4.2.13. Benzyl 2-hydroxy-1-oxo-2,3-dihydro-1H-indene-2-
26
min, 254 nm,
s
R (major)¼9.2 min,
s
R (minor)¼8.0 min.
carboxylate (2n). Colorless solid (20.0 mg, 75% yield); [
a]
ꢂ47.6
D
(c 0.04, CHCl3, 60% ee); mp 94e97 ꢀC; 1H NMR (500 MHz, CDCl3)
4.2.7. Methyl 2-hydroxy-5-bromine-1-oxo-2,3-dihydro-1H-indene-
d
7.80 (d, J¼7.7 Hz, 1H), 7.65 (t, J¼7.2 Hz, 1H), 7.50e7.39 (m, 2H),
2-carboxylate (2g). White solid (20.2 mg, 75% yield); [
a
]
D
25 ꢂ63.1 (c
7.33e7.26 (m, 3H), 7.14 (dd, J¼6.5, 2.8 Hz, 2H), 5.22 (d, J¼12.4 Hz,
1H), 5.12 (d, J¼12.4 Hz, 1H), 3.72 (d, J¼17.2 Hz, 1H), 3.25 (d,
0.08, CHCl3, 66% ee); mp 126e128 ꢀC; 1H NMR (500 MHz, CDCl3)
d
7.74e7.63 (m, 2H), 7.58 (dd, J¼8.2, 0.6 Hz, 1H), 3.75 (s, 3H), 3.70 (d,
J¼17.2 Hz, 1H). 13C NMR (126 MHz, CDCl3)
d 200.77, 171.28, 152.21,
J¼17.4 Hz, 1H), 3.24 (d, J¼17.4 Hz, 1H). 13C NMR (101 MHz, CDCl3)
136.19, 134.77, 133.60, 128.59, 128.47, 128.18, 127.76, 126.49, 125.35,
80.62, 68.01, 39.27; HPLC conditions: Chiralcel OD-H column
(250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min, 254 nm, sR
(major)¼19.1 min, sR (minor)¼15.9 min.
d
199.52, 171.49, 150.67, 138.94, 135.35, 128.13, 128.03, 122.30, 80.61,
53.67, 38.92. HPLC conditions: Chiralcel OD-H column
(250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min, 254 nm, sR
(major)¼15.8 min, sR (minor)¼13.4 min.
4.2.14. 1-Adamantyl 2-hydroxy-1-oxo-2,3-dihydro-1H-inde-ne-2-
25
4.2.8. Methyl 2-hydroxy-4-methoxy-1-oxo-2,3-dihydro-1H-indene-
carboxylate (2o). Colorless oil (22.0 mg, 71% yield); [
a
]
D
ꢂ25.0 (c
2-carboxylate (2h). White solid (15.6 mg, 71% yield); [
a
]
25 ꢂ45.7 (c
0.05, CHCl3, 55% ee); 1H NMR (500 MHz, CDCl3)
d
7.79 (d, J¼7.7 Hz,
D
0.07, CHCl3, 67% ee); mp 141e143 ꢀC; 1H NMR (500 MHz, CDCl3)
1H), 7.65 (td, J¼7.6, 1.1 Hz, 1H), 7.48 (d, J¼7.7 Hz, 1H), 7.42 (t,
J¼7.5 Hz, 1H), 3.66 (d, J¼17.1 Hz, 1H), 3.22 (d, J¼17.1 Hz, 1H), 2.12 (s,
3H),1.96 (d, J¼3.1 Hz, 6H),1.60 (d, J¼2.6 Hz, 6H). 13C NMR (126 MHz,
d
7.47e7.35 (m, 2H), 7.12 (d, J¼7.1 Hz, 1H), 3.92 (s, 3H), 3.74 (s, 3H),
3.66 (d, J¼17.7 Hz, 1H), 3.12 (d, J¼17.7 Hz, 1H). 13C NMR (101 MHz,
CDCl3)
d
201.05, 172.08, 156.71, 141.21, 134.86, 129.71, 116.64, 116.32,
CDCl3) d 201.44, 170.22, 152.36, 135.80, 134.01, 127.91, 126.26,
80.23, 55.58, 53.47, 36.17. HPLC conditions: Chiralcel OD-H column
(250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min, 254 nm, sR
(major)¼14.2 min, sR (minor)¼16.0 min.
125.06, 83.94, 80.54, 40.93, 39.55, 35.87, 30.82. HPLC conditions:
Chiralcel AD-H column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10,
1 mL/min, 254 nm,
s
R (major)¼18.2 min, R (minor)¼11.3 min.
s
4.2.9. Ethyl 2-hydroxy-1-oxo-2,3-dihydro-1H-indene-2-carboxylate
4.2.15.
ylate(2p). White solid (31.7 mg, 89% yield); [
CHCl3, 85% ee); mp 90e92 ꢀC; 1H NMR (400 MHz, DMSO)
a
-Methyl-
a
-phenyl-benzyl
2-hydroxy-1-indanone-carbox-
25
25
(2j). Colorless oil (14.7 mg, 72% yield); [
a
]
ꢂ41.5 (c 0.14, CHCl3,
a]
ꢂ4.3 (c 0.12,
D
D
66% ee); 1H NMR (500 MHz, CDCl3)
d
7.81 (d, J¼7.7 Hz, 1H), 7.68 (td,

90
Y. Wang et al. / Tetrahedron 71 (2015) 85e90
(c) Christoffers, J.; Werner, T.; Frey, W.; Baro, A. Chem. Eur. J. 2004, 10,
d
7.90e7.78 (m, 2H), 7.70 (d, J¼7.7 Hz, 1H), 7.57 (t, J¼7.4 Hz, 1H),
1042e1045; (d) Wellington, K. D.; Cambie, R. C.; Rutledge, P. S.; Bergquist, P. R. J.
Nat. Prod. 2000, 63, 79e85; e) Olack, G.; Morrison, H. J. Org. Chem. 1991, 56,
4969e4971; (f) Davis, F. A.; Clark, C.; Kumar, A.; Chen, B. C. J. Org. Chem. 1994,
59, 1184e1190; (g) Buchi, G.; Matsumoto, K. E.; Nishimura, H. J. Am. Chem. Soc.
1971, 93, 3299e3301; (h) Chooi, Y.; Hong, Y. J.; Cacho, R. A.; Tantillo, D. J.; Tang,
Y. J. Am. Chem. Soc. 2013, 135, 16805e16808; (i) Matsuda, Y.; Awakawa, T.;
Wakimoto, T.; Abe, I. J. Am. Chem. Soc. 2013, 135, 10962e10965; (j) Hayakawa, Y.;
Kobayashi, T.; Izawa, M. J. Antibiot. (Tokyo) 2013, 66, 731e733; (k) Ding, G. Z.;
Liu, J.; Wang, J. M.; Fang, L.; Yu, S. S. J. Asian Nat. Prod. Res. 2013, 15, 446e452;
(m) Konda, V.; Urban, J.; Desai, A.; Dahlberg, C.J. Google Patents, 2014.
2. McCann, S. F.; Annis, G. D.; Shapiro, R.; Piotrowski, D. W.; Lahm, G. P.; Long, J. K.;
Lee, K. C.; Hughes, M. M.; Myers, B. J.; Griswold, S. M.; Reeves, B. M.; March, R.
W.; Sharpe, P. L.; Lowder, P.; Barnette, W. E.; Wing, K. D. Pest. Manag. Sci. 2001,
57, 153e164.
7.23e7.07 (m, 6H), 7.02e6.85 (m, 4H), 6.69 (br s, 1H), 3.76 (d,
J¼17.4 Hz, 1H), 3.20 (d, J¼17.4 Hz, 1H), 2.08 (s, 3H). 13C NMR
(100 MHz, DMSO)
d 202.11, 169.26, 152.41, 145.36, 145.27, 136.58,
134.74, 128.72, 128.53, 128.51, 127.54, 127.49, 127.45, 125.35, 125.32,
124.85, 85.71, 81.09, 41.24, 26.25. HPLC conditions: Chiralcel OD-H
column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min, 254 nm,
s
R (major)¼19.9 min, R (minor)¼15.4 min.
s
4.2.16. 2,7-Dibromo-9H-fluoren-9-yl 2-hydroxyl-1-indanone-2-
25
carboxylate (2q). White solid (42.0 mg, 82% yield); [
a
]
ꢂ18.8 (c
D
0.05, CHCl3, 73% ee); mp 168e172 ꢀC; 1H NMR (500 MHz, CDCl3)
3. (a) A. L. Casalnuovo, WO Patent WO/03/002255, 2003. (b) Toullec, P. Y.; Bo-
naccorsi, C.; Mezzetti, A.; Togni, A. Proc. Natl. Acad. Sci. U.S.A. 2004, 101,
5810e5814; (c) Ishimaru, T.; Shibata, N.; Nagai, J.; Nakamura, S.; Toru, T.; Ka-
nemasa, S. J. Am. Chem. Soc. 2006, 128, 16488e16489; (d) Smith, A. M.; Billen,
D.; Hii, K. K. Chem. Commun. 2009, 3925e3927; (e) Smith, A. M.; Rzepa, H. S.;
White, A. J.; Billen, D.; Hii, K. K. J. Org. Chem. 2010, 75, 3085; (f) Li, J.; Cheng, G.;
Wang, Z.; Zhang, R. Z.; Zhang, X. M.; Ding, K. L. Chem. Sci. 2011, 2, 1141e1144; (g)
Jiang, J. J.; Wang, D.; Zhao, M. X.; Shi, M. Tetrahedron: Asymmetry 2010, 21,
794e799; (h) Yin, C. K.; Cao, W. D.; Lin, L. L.; Liu, X. H.; Feng, X. M. Adv. Synth.
Catal. 2013, 355, 1924e1930.
d
7.83 (d, J¼7.7 Hz, 1H), 7.64 (dd, J¼13.0, 5.1 Hz, 2H), 7.56e7.52 (m,
1H), 7.49 (dd, J¼8.1, 1.5 Hz, 1H), 7.43 (m, 5H), 6.66 (s, 1H), 3.76 (d,
J¼17.2 Hz, 1H), 3.31 (d, J¼17.2 Hz, 1H). 13C NMR (100 MHz, CDCl3)
d
200.36, 172.07, 152.16, 142.55, 142.36, 139.08, 138.76, 136.37,
133.17, 133.09, 129.26, 129.03, 128.35, 126.56, 125.44, 122.10, 122.06,
121.48, 121.36, 80.85, 76.05, 39.05. HPLC conditions: Chiralcel OD-H
column (250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min, 254 nm,
4. (a) Lu, M.; Zhu, D.; Lu, Y. P.; Zeng, X. F.; Tan, B.; Xu, Z. J.; Zhong, G. F. J. Am. Chem.
Soc. 2009, 131, 4562e4563; (b) Gong, B.; Meng, Q. W.; Su, T.; Lian, M. M.; Wang,
Q.; Gao, Z. X. Synlett 2009, 2659e2662; (c) Cai, Y. C.; Lian, M. M.; Li, Z.; Meng, Q.
W. Tetrahedron 2012, 38, 7973e7977; (d) Lian, M. M.; Li, Z.; Meng, Q. W.; Gao, Z.
X. Eur. J. Org. Chem. 2010, 34, 6525e6530; (e) Yao, H. J.; Lian, M. M.; Li, Z.; Wang,
Y. K.; Meng, Q. W. J. Org. Chem. 2012, 77, 9601e9608; (f) Zou, L.; Wang, B.; Mu,
H.; Zhang, H.; Song, Y.; Qu, J. Org. Lett. 2013, 15, 3106e3109; (g) Odagi, M.;
Furukori, K.; Watanabe, T.; Nagasawa, K. Chem. Eur. J. 2013, 19, 16740e16745; (h)
Acocella, M. R.; Mancheno, O. G.; Bella, M.; Jørgensen, K. A. J. Org. Chem. 2004,
69, 8165e8167.
s
R (major)¼21.9 min,
s
R (minor)¼18.6 min.
4.2.17. 9-Anthracenemethyl
2-hydroxy-1-indanone-2-carboxylate
25
(2r). Yellow solid (29.6 mg, 81% yield); [
a
]
ꢂ20.0 (c 0.16, CHCl3,
D
72% ee); mp 111e113 ꢀC; 1H NMR (500 MHz, CDCl3)
d
8.45 (s, 1H),
8.12 (d, J¼8.1 Hz, 2H), 8.05e7.93 (m, 2H), 7.70 (d, J¼7.6 Hz, 1H), 7.53
(t, J¼7.5 Hz, 1H), 7.50e7.42 (m, 4H), 7.33 (t, J¼7.5 Hz, 1H), 7.29e7.23
(m, 1H), 6.36 (d, J¼12.6 Hz, 1H), 6.00 (d, J¼12.6 Hz, 1H), 3.49 (d,
J¼17.1 Hz, 1H), 3.11 (d, J¼17.1 Hz, 1H). 13C NMR (126 MHz, CDCl3)
5. For some reviews on reactions using molecular oxygen as an oxidant, see: (a)
Stahl, S. S. Science 2005, 309, 1824; (b) Stahl, S. S. Angew. Chem., Int. Ed. 2004, 43,
3400; (c) Schultz, M. J.; Sigman, M. S. Tetrahedron 2006, 62, 8227; (d) Sigman,
M. S.; Jensen, D. R. Acc. Chem. Res. 2006, 39, 221; (e) Beccalli, E. M.; Broggini, G.;
Martinelli, M.; Sottocornola, S. Chem. Rev. 2007, 107, 5318; (f) Piera, J.; Bckvall, J.
E. Angew. Chem., Int. Ed. 2008, 47, 3506; (g) Punniyamurthy, T.; Velusamy, S.;
Iqbal, J. Chem. Rev. 2005, 105, 2329; (h) Shi, Z.; Zhang, C.; Tang, C.; Jiao, N. Chem.
Soc. Rev. 2012, 41, 3381.
d
200.73, 171.56, 152.15, 135.97, 133.47, 131.23, 130.95, 129.66,
129.08, 128.00, 126.81, 126.37, 125.24, 125.11, 124.83, 123.58, 80.77,
61.27, 39.17. HPLC conditions: Chiralcel OD-H column
(250ꢁ4.6 mm), hexane/i-PrOH¼90/10, 1 mL/min, 254 nm, sR
(major)¼31.7 min,
s
R (minor)¼25.3 min.
ꢀ
ꢀ
6. (a) Cordova, A.; Sunden, H.; Engqvist, M.; Ibrahem, I.; Casas, J. J. Am. Chem. Soc.
ꢀ
ꢀ
2004, 126, 8914e8915; (b) Ibrahem, I.; Zhao, G. L.; Sunden, H.; Cordova, A.
Acknowledgements
ꢀ
Tetrahedron Lett. 2006, 47, 4659e4663; (c) Sunden, H.; Engqvist, M.; Casas, J.;
Ibrahem, I.; Cordova, A. Angew. Chem., Int. Ed. 2004, 43, 6532e6535.
ꢀ
7. Lian, M. M.; Li, Z.; Cai, Y. C.; Meng, Q. W.; Gao, Z. X. Chem. Asian J. 2012, 7,
2019e2023.
8. (a) Sano, D.; Nagata, K.; Itoh, T. Org. Lett. 2008, 10, 1593e1595; (b) Dehmlow, E.
V.; Wagner, S.; Muller, A. Tetrahedron 1999, 55, 6335; (c) DeVries, E. F. J.; Ploeg,
L.; Colao, M.; Brussee, J.; VanderGen, A. Tetrahedron: Asymmetry 1995, 6,
1123.
We would like to thank the National Natural Science Foundation
of China (No. 21176041) and the State Key Laboratory of Fine
Chemicals for their support.
Supplementary data
9. Schirmann, J. P.; Bourdauducq, P. “Hydrazine” in Ullmann’s Encyclopedia of In-
dustrial Chemistry; Wiley-VCH: Weinheim, 2002.
10. Stankovich, S.; Dikin, D. A.; Piner, R. D.; Kohlhaas, K. A.; Kleinhammes, A.; Jia, Y.
Y.; Wu, Y.; Nguyen, S. T.; Ruoff, R. S. Carbon 2007, 45, 1558e1565.
11. Vieira, R.; Pham-Huu, C.; Keller, N.; Ledoux, M. J. Chem. Commun. 2002,
954e955.
12. Kawai, H.; Okusu, S.; Yuan, Z.; Tokunaga, E.; Yamano, A.; Motoo Shiro, M.;
Shibata, N. Angew. Chem., Int. Ed. 2013, 52, 2221e2225.
13. Taniguchi, T.; Sugiura, Y.; Zaimoku, H.; Ishibashi, H. Angew. Chem. 2010, 122,
10352e10355.
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2014.11.029.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
References and notes
14. Samsel, E. G.; Kochi, J. K. Inorg. Chem. 1986, 25, 2450e2451.
15. Kosower, E. Acc. Chem. Res. 1971, 4, 193e198.
1. (a) Christoffers, J.; Baro, A.; Werner, T. Adv. Synth. Catal. 2004, 346, 143e151; (b)
Zhu, J.; Klunder, A. J. H.; Zwanenburg, B. Tetrahedron Lett. 1994, 35, 2787e2790;