Stereoselective [3+2] cycloaddition of N-tert-butanesulfinyl imines to arynes facilitated by a removable PhSO2CF2 group: Synthesis and transformation of cyclic sulfoximines

Article abstract of DOI:10.1039/c4cc05042h

An unprecedented [3+2] cycloaddition between N-tert-butanesulfinyl imines and arynes provides a stereoselective method for the synthesis of cyclic sulfoximines. Not only does the difluoro(phenylsulfonyl)methyl group play an important role in facilitating the cycloaddition reaction, it can also be removed or substituted through the transformation of the difluorinated cyclic sulfoximines to cyclic sulfinamides. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4cc05042h

ChemComm
View Article Online
View Journal | View Issue
COMMUNICATION
Stereoselective [3+2] cycloaddition of N-tert-
butanesulfinyl imines to arynes facilitated by a
removable PhSO2CF2 group: synthesis and
transformation of cyclic sulfoximines†
Cite this: Chem. Commun., 2014,
50, 10596
Received 9th July 2014,
Accepted 24th July 2014
Wenchao Ye,‡ Laijun Zhang,‡ Chuanfa Ni, Jian Rong and Jinbo Hu*
DOI: 10.1039/c4cc05042h
www.rsc.org/chemcomm
An unprecedented [3+2] cycloaddition between N-tert-butanesulfinyl
imines and arynes provides a stereoselective method for the synthesis
of cyclic sulfoximines. Not only does the difluoro(phenylsulfonyl)methyl
group play an important role in facilitating the cycloaddition reaction, it
can also be removed or substituted through the transformation of the
difluorinated cyclic sulfoximines to cyclic sulfinamides.
Since their initial discovery in the late 1940s, sulfoximines have
played prominent roles in modern chemistry.1 Due to their unique Scheme 1 [3+2] Cycloaddition of N-tert-butanesulfinyl imines to arynes
and subsequent transformations.
structure and biological activity, sulfoximines have been widely
applied in asymmetric synthesis (both as chiral auxiliaries and
ligands) and in medicinal chemistry and crop protection.2–4
A
sulfoximine functionality is generally constructed by three known quasi-1,3-dipole11,12 for cycloaddition reactions has never been
methods: (a) oxidative imination of a sulfoxide, (b) oxidation of a reported.13 Herein, we report an unprecedented stereoselective
sulfilimine, and (c) substitution reaction with a sulfonimidoyl halide [3+2] cycloaddition of enantiopure difluorinated N-TBS imines
or a sulfonimidate.1 Enantioenriched sulfoximines are commonly with arynes14 for the synthesis of enantiopure cyclic sulfoximines
obtained by resolution of racemic mixtures,5 or oxidative imination (1-(tert-butyl)benzo[d]iso-thiazole 1-oxides) and their subsequent
of enantioenriched sulfoxides.1,2,6 Although enantioenriched cyclic transformation into various cyclic sulfinamides (Scheme 1).
sulfoximines can be obtained from multi-step elaborations of
At the onset of our investigation, o-trimethylsilyl phenyl triflate
enantioenriched linear ones,7 there is still lack of one-step (3a) was chosen as a model substrate,15 and an excess amount of
methods for their synthesis.
CsF was used as an activator to generate the benzyne intermediate
Enantiomerically pure N-tert-butanesulfinyl (TBS) imines, which (see Table 1);16 the reactions between N-TBS imines 1a–c and 3a
8
´
were first reported by Garcıa Ruano and co-workers in 1996, have were carried out at room temperature for 48 h using acetonitrile
found wide applications in asymmetric synthesis since Ellman’s as a solvent with a reactant ratio 1 :3a : CsF = 1:2:3 (Table 1,
seminal work on the practical preparation of enantiomerically pure entries 1–3). However, sulfinimines 1a–c were recovered almost
N-tert-butanesulfinamide and its subsequent condensation with quantitatively. Inspired by the excellent modulating ability of
aldehydes and ketones.9,10a However, the synthetic application of neighbouring fluorine substitution upon the reactivity of organic
N-TBS imines has mainly been based on the high electrophilicity of compounds,17 we envisioned that the introduction of fluorine
CQN bonds towards many different nucleophiles, which affords atom(s) at the a-position of the CQN functionality of N-TBS
a variety of structurally diverse enantioenriched amines.10 To the imines might be able to significantly tune their reactivity by
best of our knowledge, however, the use of N-TBS imine as a enhancing the electrophilicity of the imino carbon atom, while
keeping the sulfur atom (of the sulfinyl group) with reasonable
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai, 200032,
China. E-mail: jinbohu@sioc.ac.cn; Fax: +86 21-64166128
nucleophilicity, thus promoting the desired [3+2] cycloaddition.
Preliminary results showed that the reaction with 1d could afford
a [3+2] cycloaddition product 4d in 32% yield with excellent
stereoselectivity (dr 4 99 : 1, er 4 99 : 1) (Table 1, entry 4).18,19
Although 1e is expected to be more reactive than 1d, its reaction
with 3a failed to give the desired product; indeed, a complete
† Electronic supplementary information (ESI) available. CCDC 1009678–1009684.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4cc05042h
‡ W. Ye and L. Zhang contributed equally to this work.
10596 | Chem. Commun., 2014, 50, 10596--10599
This journal is ©The Royal Society of Chemistry 2014

View Article Online
Communication
ChemComm
Table 1 Screening of N-tert-butanesulfinyl imines
Entry
Sulfinimine
R1
R2
Sulfoximine
Yielda (%)
drb
erc
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
Ph
Ph
Ph
Ph
CF3
Ph
CF2SO2Ph
CF2SO2Ph
H
Me
Ph
CF2H
Ph
CH2F
Ph
4a
4b
4c
4d
4e
5f
0d
0d
—
—
—
—
—
—
499 : 1
—
—
499 : 1
499 : 1
0d
32
499 : 1e
—
0 f
0d
—
499 : 1
499 : 1
2a
2a
5a
5a
74
Ph
87g
a
b
c
d
Isolated yield. Determined by 19F NMR analysis of the crude product. Determined by chiral HPLC analysis of the isolated product. Imines
e
f
g
1a–c and 1f were recovered. Determined by HPLC-MS analysis of the crude product. Imine 1e decomposed. Conditions: 2a/3a/CsF = 1 : 3 : 5,
CH3CN, rt, 12 h.
decomposition of 1e was detected (Table 1, entry 5). The poor imines 2a–i, bearing either electron-donating or electron-
yields (when 1d and 1e were used in the reaction with benzyne) withdrawing substituents, could undergo the reaction smoothly
can be partially attributed to their sensitivity to humidity.20 to provide 5a–i in good yields with excellent stereocontrol
Moreover, similar to non-fluorinated sulfinimines 1a–c, mono- (dr 4 99 : 1) (Table 2, entries 1–9). When styryl sulfinimine 2j
fluorinated sulfinimine 1f was found to be inert under the same was employed, the reaction proceeded readily giving 5j as the
reaction conditions with 1f being recovered (Table 1, entry 6). All single product in 61% yield with excellent diastereomeric
these results indicated that a,a-difluoro substitution on N-TBS control (dr 4 99 : 1) (Table 2, entry 10). Moreover, alkyl sulfi-
imines plays a crucial role in tuning their chemical reactivity as nimine 2k also underwent the reaction, giving 5k in lower yield
quasi-1,3-dipoles.
(36%) but still with an excellent diastereomeric ratio (dr 4 99: 1)
To find more reactive sulfinimine-type 1,3-dipoles, an
exhaustive screening of the difluorinated sulfinimines was
carried out. It was found that PhSO2CF2-sulfinimines 2 are
generally air- and moisture-stable and can be readily prepared
from tert-butanesulfinamide and the corresponding ketones.
The [3+2] cycloaddition between 2a and benzyne was efficient,
and sulfoximine 5a was obtained in 74% yield (Table 1, entry 7).
The excellent reactivity of 2a toward benzyne can be attributed
to both the strong electron-withdrawing ability of the PhSO2CF2
group and the steric protection of CQN by the relatively hydro-
phobic PhSO2 group. After further optimization of the reaction
between sulfinimine 2a and benzyne precursor 3a, the optimal
yield of 5a (87%) was obtained when the reaction was performed at
room temperature for 12 h with a reactant ratio of 2a :3a :CsF =
1 : 3 : 5 (Table 1, entry 8). It is noteworthy that, although the
reactant ratio, temperature, and reaction time can somewhat
influence the yields of 5a, these parameters have no influence
on the stereochemical outcome of this reaction (see ESI,†
Section S2). The absolute configuration of N-TBS imine 2a was
determined by the X-ray crystal structure analysis of its para-
brominated analogue 2e, and that of product 5a was determined
by its X-ray crystal structure analysis (see ESI,† Section S3.1).19 It
turned out that the reaction between 2a and 3a proceeded in a highly
stereoselective mode, giving product 5a (dr 4 99 : 1, er 4 99 : 1) with
the configuration of the sulfur stereogenic center retained.
Table 2 [3+2] Cycloaddition of PhSO2CF2–sulfinimines with arynesa
Entry Sulfinimine
3
Sulfoximine Yieldb (%) drc
1
2
3
4
5
6
7
8
2a R1 = Ph
3a 5a
87
81
62
73
78
76
80
78
90
61
36
80
74
70
78
75
72
74
62
60
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
499 : 1
2b R1 = 3-MeC6H4 3a 5b
2c R1 = 4-MeC6H4 3a 5c
2d R1 = 4-ClC6H4
2e R1 = 4-BrC6H4
3a 5d
3a 5e
2f R1 = 3-MeOC6H4 3a 5f
2g R1 = 4-MeOC6H4 3a 5g
2h R1 = 4-CF3C6H4 3a 5h
2i R1 = 6-Br-2-Naph 3a 5i
9
10
11
12
2j R1 = (E)-styryl
2k R1 = iPr
3a 5j
3a 5k
3b 5l
2a R1 = Ph
13d 2b R1 = 3-MeC6H4 3b 5m
14d 2d R1 = 4-ClC6H4
3b 5n
15d 2f R1 = 3-MeOC6H4 3b 5o
16
2a R1 = Ph
3c 5p
17d 2b R1 = 3-MeC6H4 3c 5q
18d 2f R1 = 3-MeOC6H4 3c 5r
19d 2a R1 = Ph
3d 5s
20d 2f R1 = 3-MeOC6H4 3d 5t
21
2a R1 = Ph
3e 5u
91 (46 : 54)e 499 : 1/499 : 1
By using the optimized reaction conditions as the standard
(see Table 1, entry 8), we examined the substrate scope of this
novel [3+2] cycloaddition reaction with enantiopure PhSO2CF2–
a
b
c
Reactant ratio: 2 : 3: CsF = 1 : 3 : 5. Isolated yield. The dr of 5 was
determined by 19F NMR analysis of the crude product. Performed at
d
e
sulfinimines. As shown in Table 2, a variety of aromatic N-TBS 80 1C. The product 5u was obtained as a mixture of two regio-isomers.
This journal is ©The Royal Society of Chemistry 2014
Chem. Commun., 2014, 50, 10596--10599 | 10597

View Article Online
ChemComm
Communication
Table 3 Synthesis of cyclic sulfonamides
Table 4 Synthesis of cyclic sulfinimines
Entry Sulfinamide R1
R2 R3 Sulfinimine Yielda (%) erb
Entry Sulfoximine R1
R2 R3
Sulfinamidea Yieldb (%)
1
2
3
4
5
6
6a
6b
6c
6d
6h
6i
Ph
H
H
H
H
H
H
H
H
7a
7b
7c
7d
70
66
71
73
65
62
98 : 2c
96 : 4
97 : 3
95 : 5
93 : 7
95 : 5
3-MeC6H4
4-BrC6H4
4-CF3C6H4
Ph
1
2
3
4
5
6
7
8
9
10
5a
5b
5e
5h
5i
5j
5k
5l
Ph
H
H
H
H
H
H
H
H
H
H
H
6a
6b
6c
6d
6e
6f
96
92
93
94
94
96
91
92
96
95
3-MeC6H4
4-BrC6H4
4-CF3C6H4
6-Br-2-Naph H
(E)-styryl
iPr
Ph
3-MeC6H4
Ph
Me Me 7e
3-MeC6H4 Me Me 7f
H
H
a
b
c
Isolated yield. Determined by chiral HPLC analysis of 7. The er of
6g
6h
6i
7a can be improved to 499 : 1 after a single recrystallization.
Me Me
Me Me
5m
5p
(CH2)3 6j
sulfinimines from 6 and their subsequent addition reactions
with other nucleophiles (Scheme 2). Such an elimination–
addition process would be synthetically valuable, as it corre-
sponds to a formal nucleophilic substitution of the PhSO2CF2
group. After screening of the reaction conditions, it was estab-
lished that treatment of 6a with Cs2CO3 in THF at 42–45 1C
afforded sulfinimine 7a in 70% yield with 98 : 2 er (Table 4,
entry 1). Other sulfinamides 6b–d, 6h and 6i could also be
treated under the same conditions to give 7b–f in good yields
with high enantioselectivity (Table 4, entries 2–6). The retention
of the absolute configuration of the sulfur atom was confirmed
by X-ray crystallographic analysis of 7c (see ESI,† Section S3.4).19
Note that these chiral sulfinimines represent a new class of
synthons that are otherwise difficult to prepare when employing
classical condensation methods.25 The further reaction of the
cyclic sulfinimines was exemplified by the addition of several
enolate anions to enantioenriched 7a (Table 5). When potassium
hexamethyldisilazide (KHMDS) was used as a base, the reactions
with carbonyl compounds 8 proceeded smoothly at À78 1C to
give adducts 9a–f in excellent yields with high diastereoselectivity
(Table 5, entries 1–7). The absolute configuration of the quaternary
carbon center of 9c was identified to be S by X-ray crystallographic
analysis of its corresponding sulfonamide S4 (see ESI,†
Section S3.6),19 which could be rationalized by coordination
of the potassium enolate to the sulfinyl oxygen and subsequent
addition to the re-face of sulfinimine (S)-7a.
a
The dr of 6 was determined by 19F NMR analysis of the crude product.
Isolated yield.
b
(Table 2, entry 11). To underline the practicality and efficiency of
this novel stereoselective [3+2] cycloaddition reaction, several
other aryne precursors 3b–e were used to react with N-TBS
imines 2. When the standard reaction conditions (except that
the temperature was elevated to 80 1C) were applied, 3b–e readily
reacted with 2a–b, 2d, and 2f to give desired cycloaddition
products 5l–u in satisfactory yields (60–91%) with excellent
stereocontrol (dr 4 99: 1) (Table 2, entries 12–21). When aryne
precursor 3e was employed to react with 2a under similar
reaction conditions, a mixture of two regio-isomers of 5u was
obtained in a ratio of 46: 54 (Table 2, entry 21), supporting the
involvement of an aryne intermediate in this reaction.
With cyclic sulfoximes 5 in hand, we investigated their
transformation into cyclic sulfinamides 6 by de-tert-butylation.
Although chiral cyclic sulfonamides (sultams) have become an
important class of synthetic targets,21 there are only very few
examples available for the stereocontrolled synthesis of cyclic
sulfinamides.22 After a brief scanning of different reaction con-
ditions, we found that alkyl, alkenyl and aryl-substituted cyclic
sulfoximines 5 could be readily converted into cyclic sulfina-
mides 6 in excellent yields with very high stereochemical fidelity
(dr 4 99 : 1) upon treatment of HCl–1,4-dioxane in CH2Cl2 at
À78 1C (Table 3).23 The absolute configuration of 6a was determined
by the X-ray crystal structure analysis of its N-(6-bromonaphthalen-2-
yl)methyl derivative compound S3 (see ESI,† Section S3.3),19 which
demonstrates that the configuration of the sulfur stereogenic center
was retained during the loss of the tert-butyl group.
Table 5 Nucleophilic addition to cyclic sulfiniminesa
Subsequently, taking advantage of this nucleofugality of the
PhSO2CF2 anion,24 we focused on the formation of chiral cyclic
Entry
R
Sulfinamide Yieldb (%) drc
erc
1
2
3
4
5
6
4-EtC6H4
4-NO2C6H4
4-BrC6H4
2-benzo[b]thienyl 9d
2-Naph
EtO
9a
9b
9c
93
84
95
97
91
88
95 : 5
88 : 12 99 : 1
92 : 8
94 : 6
95 : 5
95 : 5
99 : 1
99 : 1
99 : 1
99 : 1
99 : 1
9e
9f
a
b
Scheme 2 Elimination–addition reaction of PhSO2CF2-substituted
sulfonamides.
Reactant ratio: 7a : 8 : KHMDS = 1 : 2 : 2. Total isolated yield of 9.
Determined by chiral HPLC analysis of 9.
c
10598 | Chem. Commun., 2014, 50, 10596--10599
This journal is ©The Royal Society of Chemistry 2014

View Article Online
Communication
ChemComm
sulfilimines, see: J. Wang, M. Frings and C. Bolm, Angew. Chem.,
Int. Ed., 2013, 52, 8661; and references therein.
7 For examples, see: (a) M. Harmata and P. Zheng, Org. Lett., 2007,
9, 5251; (b) M. Harmata, Y. Chen and C. L. Barnes, Org. Lett., 2007,
9, 4701; (c) C. Bolm and H. Villar, Synthesis, 2005, 1421; and references
therein; ; (d) T. R. Williams and D. J. Cram, J. Org. Chem., 1973, 38, 20.
´
8 J. L. Carcıa Ruano, I. Fernandez, M. del Prado Catalina and A. A. Cruz,
Tetrahedron: Asymmetry, 1996, 7, 3407.
9 G. Liu, D. A. Cogan and J. A. Ellman, J. Am. Chem. Soc., 1997, 119, 9913.
10 For recent reviews, see: (a) M. T. Robak, M. A. Herbage and J. A.
Ellman, Chem. Rev., 2010, 110, 3600; (b) F. Ferreira, C. Botuha,
´
F. Chernla and A. Perez-Luna, Chem. Soc. Rev., 2009, 38, 1162;
Scheme 3 Reductive desulfonylation.
(c) J. Liu and J. Hu, Future Med. Chem., 2009, 1, 875.
11 The 1,3-dipoles are generally defined as ‘‘having a p-electron system
consisting of two filled and one empty orbital and are analogous with
the allyl or propargyl anion’’. According to this criterion, N-tert-
butanesulfinyl imines do not belong to real 1,3-dipoles. See:
(a) F. A. Carey and R. J. Sundberg, Advanced Organic Chemistry, Part
A: Structure and Mechanisms, Springer, New York, 2007, p. 873; (b) 1,3-
Dipolar Cycloaddition Chemistry, ed. A. Padwa, Wiley, New York, 1984.
We finally turned our attention to the release of the masked
CF2H from PhSO2CF2. Upon treatment with Mg0 under mild
acidic conditions (HOAc–AcONa) in a DMF–H2O system,26 5a
and 6a could be conveniently converted into the difluoromethyl-
ated products 10 and 11 in high yields with excellent stereo- 12 For examples of quasi-1,3-dipoles, see: (a) E. Brunn and R. Huisgen,
Angew. Chem., Int. Ed. Engl., 1969, 8, 513; (b) R. Huisgen, E. Brunn,
R. Gilardi and I. Karle, J. Am. Chem. Soc., 1969, 91, 7766.
13 There are only two examples on the one-step cyclizations with the
chemical fidelity (Scheme 3). Since the CF2H group can act as a
more lipophilic hydrogen bond donor than typical donors such
as OH and SH, the CF2H-containing chiral cyclic sulfoximines
and sulfinamides represent interesting new structural motifs for
life science-related applications.
CQN-S subunit of sulfinimines forming cyclic sulfinamides. See:
(a) F. A. Davis, J. Qu, V. Srirajan, R. Joseph and D. D. Titus, Hetero-
cycles, 2002, 58, 251; (b) T. Andreassen, M. Lorentzen, L.-K. Hansen
and O. R. Gautun, Tetrahedron, 2009, 65, 2806.
In summary, we have shown that difluorinated N-TBS imi- 14 For selected reviews, see: (a) H. Pellisier and M. Santelli, Tetrahedron,
˜
´
´
2003, 59, 701; (b) D. Pena, D. Perez and E. Guitian, Heterocycles, 2007,
74, 89; (c) A. Bhunia, S. R. Yetra and A. T. Biju, Chem. Soc. Rev., 2012,
41, 3140; (d) P. M. Tadross and B. M. Stoltz, Chem. Rev., 2012, 112, 3550;
(e) C. M. Gampe and E. M. Carreira, Angew. Chem., Int. Ed., 2012,
51, 3766; ( f ) A. V. Dubrovskiy, N. A. Markina and R. C. Larock, Org.
Biomol. Chem., 2013, 11, 191.
nes can act as novel chiral quasi-1,3-dipoles in stereoselective
[3+2] cycloaddition reactions with arynes, which opens up a
new avenue for the synthesis of enantiopure cyclic sulfoximines.
The PhSO2CF2 group enhances the reactivity of the N-TBS imines
(due to its electron-withdrawing ability) and improves the stability
15 Y. Himeshima, T. Sonoda and H. Kobayashi, Chem. Lett., 1983, 1211.
of such imines against water (by increasing the hydrophobicity), 16 (a) C. Ni, L. Zhang and J. Hu, J. Org. Chem., 2008, 73, 5699;
(b) Y. Zeng, L. Zhang, Y. Zhao, C. Ni, J. Zhao and J. Hu, J. Am. Chem.
Soc., 2013, 135, 2955.
17 (a) K. Uneyama, Organofluorine Chemistry, Blackwell, Oxford, 2006,
thus facilitating the subsequent stereoselective [3+2] cycloaddition
reaction. On the other hand, the synthetic utility of these [3+2]
reaction products was conveniently demonstrated by their ready
transformation into cyclic sulfinamides via stereoselective de-tert-
butylation, as well as the subsequent transformation of the cyclic
sulfinamides into non-fluorinated ones by a formal nucleophilic
substitution of the PhSO2CF2 group.
p. 101; for recent examples, see: (b) J. M. Baskin, J. A. Prescher,
S. T. Laughlin, N. J. Agard, P. V. Chang, I. A. Miller, A. Lo,
J. A. Codelli and C. R. Bertozzi, Proc. Natl. Acad. Sci. U. S. A., 2007,
104, 16793; (c) X. Shen, L. Zhang, Y. Zhao, L. Zhu, G. Li and J. Hu,
Angew. Chem., Int. Ed., 2011, 50, 2588.
18 The absolute configuration of 1d was determined by the X-ray
crystal structure of its analogue S2, and that of 5a was determined
by its X-ray crystal structure analysis (see ESI,† Section S3.1).19
.
Our work was supported by the National Basic Research
Program of China (2012CB215500 and 2012CB821600), the 19 CCDC 1009678 (2e), 1009680 (5a), 1009679 (4d), 1009681 (7c), 1009682
(S2), 1009683 (S3) and 1009684 (S4) contain the supplementary crystallo-
graphic data for this paper and its ESI†.
20 For discussion on their instability towards moisture, see: (a) H. Wang,
NNSF of China (21002115 and 21372246), Shanghai QMX
program (13QH1402400), and Chinese Academy of Sciences.
X. Zhao, Y. Li and L. Lu, Org. Lett., 2006, 8, 1379; (b) H. Chen, W. Yu,
X. H. Guo, W. D. Meng and Y. G. Huang, Chin. Chem. Lett., 2012, 23, 277.
21 For recent examples, see: (a) T. Nishimura, A. Noishiki, G. C. Tsui
Notes and references
1 M. Reggelin and C. Zur, Synthesis, 2000, 1.
and T. Hayashi, J. Am. Chem. Soc., 2012, 134, 5056; (b) H. Wang,
T. Jiang and M.-H. Xu, J. Am. Chem. Soc., 2013, 135, 971; (c) G. Yang
and W. Zhang, Angew. Chem., Int. Ed., 2013, 52, 7540; (d) F. Foschi,
A. Tagliabue, V. Mihali, T. Pilati, I. Pecnikaj and M. Penso, Org. Lett.,
2013, 15, 3686.
2 For reviews, see: (a) H. Okamura and C. Bolm, Chem. Lett., 2004,
33, 482; (b) H.-J. Gais, Heteroat. Chem., 2007, 18, 472; (c) C. Worch,
A. C. Mayer and C. Bolm, in Organosulfur Chemistry in Asymmetric
Synthesis, T. Toru and C. Bolm, Wiley-VCH, Weinheim, 2008.
´
3 For recent examples, see: (a) M. Frings, I. Thome and C. Bolm, 22 (a) M. Wills, R. J. Butlin, I. D. Linney and R. W. Gibson, J. Chem. Soc.,
Beilstein J. Org. Chem., 2012, 8, 1443; (b) X. Shen, W. Zhang,
L. Zhang, T. Luo, X. Wan, Y. Gu and J. Hu, Angew. Chem., Int. Ed.,
2012, 51, 6966; (c) X. Shen, W. Zhang, C. Ni, Y. Gu and J. Hu, J. Am.
Chem. Soc., 2012, 134, 16999.
Perkin Trans. 1, 1991, 3383; (b) M. M. Endeshaw, A. Bayer, L. K. Hansen
and O. R. Gautun, Eur. J. Org. Chem., 2006, 5249; (c) M. Harmata and
P. Zheng, Org. Lett., 2007, 9, 5251; (d) J. Coulomb, V. Certal, M.-H.
ˆ
Larraufie, C. Ollivier, J.-P. Corbet, G. Mignani, L. Fensterbank, E. Lacote
4 For more recent reviews, see: (a) U. Lu¨cking, Angew. Chem., Int. Ed.,
and M. Malacria, Chem. – Eur. J., 2009, 15, 10225.
2013, 52, 9399; (b) V. Bizet, R. Kowalczyk and C. Bolm, Chem. Soc. Rev., 23 For the removal of S-t-Bu group in acyclic sulfoximines, see:
¨
2014, 43, 2426; (c) X. Shen and J. Hu, Eur. J. Org. Chem., 2014, 4437.
5 (a) C. R. Johnson and C. W. Schroeck, J. Am. Chem. Soc., 1973, 95, 7418;
(b) J. Brandt and H. J. Gais, Tetrahedron: Asymmetry, 1997, 8, 909.
S. Gaillard, C. Papamicael, G. Dupas, F. Marsais and V. Levacher,
Tetrahedron, 2005, 61, 8138.
24 X. Shen, C. Ni and J. Hu, Helv. Chim. Acta, 2012, 95, 2043.
6 (a) O. Mancheno and C. Bolm, Chem. – Eur. J., 2007, 13, 6674; and 25 M. Daniel and R. A. Stockman, Tetrahedron, 2006, 62, 8869.
references therein; (b) for oxidation of enantioenriched 26 C. Ni and J. Hu, Tetrahedron Lett., 2005, 46, 8273.
;
This journal is ©The Royal Society of Chemistry 2014
Chem. Commun., 2014, 50, 10596--10599 | 10599