[FeIII(F20-tpp)Cl] Is an effective catalyst for nitrene transfer reactions and animation of saturated hydrocarbons with sulfonyl and aryl azides as nitrogen source under thermal and microwave-assisted conditions

Article abstract of DOI:10.1002/chem.201000581

[Fe^III(F₂₀-tpp)Cl] (F20tpp = meso- tetrakis(pentafluorophenyl)porphyrinato dianion) is an effective catalyst for imido/nitrene insertion reactions using sulfonyl and aryl azides as nitrogen source. Under thermal conditions, aziridination of aryl and alkyl alkenes (16 examples, 60-95% yields), sulfimidation of sulfides (11 examples, 76-96% yields), allylic amidation/amination of α-methylstyrenes (15 examples, 68-83% yields), and amination of saturated C-H bonds including that of cycloalkanes and adamantane (eight examples, 64-80% yields) can be accomplished by using 2 mol % [Fe^III(F_20- tpp)Cl] as catalyst. Under microwave irradiation conditions, the reaction time of aziridination (four examples), allylic amination (five examples), sulfimidation (two examples), and amination of saturated C-H bonds (three examples) can be reduced by up to 16fold (24-48 versus 1.5-6 h) without significantly affecting the product yield and substrate conversion.

Full text of DOI:10.1002/chem.201000581

DOI: 10.1002/chem.201000581
ACHTUNGTRENNUNG ACHTUNGTRENNUNG(F20-tpp)Cl] Is an Effective Catalyst for Nitrene Transfer Reactions and
[FeIII
Amination of Saturated Hydrocarbons with Sulfonyl and Aryl Azides as
Nitrogen Source under Thermal and Microwave-Assisted Conditions
Yungen Liu and Chi-Ming Che*[a]
Abstract:
[FeIII
E
ples, 68–83% yields), and amination of
irradiation conditions, the reaction
time of aziridination (four examples),
allylic amination (five examples), sulfi-
midation (two examples), and amina-
À
meso-tetrakis(pentafluorophenyl)por-
phyrinato dianion) is an effective cata-
lyst for imido/nitrene insertion reac-
tions using sulfonyl and aryl azides as
nitrogen source. Under thermal condi-
tions, aziridination of aryl and alkyl al-
kenes (16 examples, 60–95% yields),
sulfimidation of sulfides (11 examples,
76–96% yields), allylic amidation/ami-
nation of a-methylstyrenes (15 exam-
saturated C H bonds including that of
cycloalkanes and adamantane (eight
examples, 64–80% yields) can be ac-
complished by using 2 mol% [FeIII
A
tion of saturated C H bonds (three ex-
À
amples) can be reduced by up to 16-
fold (24–48 versus 1.5–6 h) without sig-
nificantly affecting the product yield
and substrate conversion.
Keywords: allylic compounds
·
À
azides · C H activation · microwave
chemistry · porphyrinoids
À
Introduction
Saturated C H bonds are generally not regarded as func-
tional groups in organic synthesis. After decades of efforts
À
Metal-catalyzed nitrene/imido transfer reactions, such as
aziridination of alkenes, sulfimidation of sulfides, and ami-
nation/amidation of alkanes, have important applications in
organic synthesis.[1] In particular, the amination of unactivat-
directed to C H bond activation, direct functionalization of
À
saturated C H bonds by metal catalysis has become a viable
approach and could be a useful tool for organic synthesis.[7]
Up to now, most of the metal-catalyzed C H bond activa-
À
À
À
ed C H bonds with acceptable product yields and selectivity
tions have focused on activated C H bonds (such as those
remains a difficult challenge. Most of the reported nitrene/
at the allylic/benzylic position,[8] or adjacent to O or
imido transfer and insertion reactions use N-arylsulfonylim-
N atoms[9]) or intramolecular cyclization reactions.[10] Direct
À
G
functionalization of unactivated saturated C H bonds (e.g.,
gen source.[2] In recent years, there has been a growing inter-
est in the use of organic azides as nitrogen-transfer reagents
because the by-product is nitrogen gas, which is nonhazar-
dous to the environment.[3] Cenini,[4] Katsuki,[5] Zhang,[6] and
their co-workers pioneered the development of nitrene
transfer reactions with organic azides catalyzed by cobalt or
ruthenium complexes.
aliphatic carbon chains) remains a formidable challenge and
relatively few reports with practical applications have been
published in this area.
In recent years, there has been a surge of interest in de-
veloping iron catalysts for atom- and group-transfer reac-
tions for the construction of C N bonds. Compared with
other transition-metal catalysts, iron complexes are inexpen-
sive and biocompatible.[12] Among the iron complexes re-
ported for this endeavor, iron porphyrins are commercially
available, air and moisture stable, and can be easily pre-
pared and modified. In the literature, iron porphyrins are
[11]
À
[a] Dr. Y. Liu, Prof. Dr. C.-M. Che
Department of Chemistry and Open Laboratory of
Chemical Biology of the Institute of Molecular Technology
for Drug Discovery and Synthesis
The University of Hong Kong
À
known to catalyze C N bond formation with N-(p-
toluenesulfonyl)im
ino
phenyliodinane (PhI=NTs) or broma-
mine-T as the nitrogen source.[1f,11c] Herein, we report that
[FeIII
AHCTUNGTRENNUNG
nyl)porphyrinato dianion) is an effective catalyst for aziridi-
nation of alkenes, sulfimidation of both alkyl and aryl sul-
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201000581.
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Chem. Eur. J. 2010, 16, 10494 – 10501

FULL PAPER
Table 2. Aziridination of styrenes.[a]
fides, direct allylic amidation/amination of a-methylstyrenes,
À
and amination of saturated C H bonds including that of cy-
cloalkanes with sulfonyl and aryl azides as the nitrogen
source.
Entry
1
Substrates
Products
Yield [%][b]
75
Results and Discussion
At the outset, various metal complexes were evaluated by
using aziridination of styrene by tosyl azide (TsN3) as the
2
85
87
test reaction (Table 1). [MnIII(tdcpp)Cl], [RhIII
ACHTNUGTRENNUG AHCUTNGTREN(NUNG F20-tpp)I]
3[c]
Table 1. Aziridination of styrene catalyzed by various metal complexes.[a]
4
5
95
95
Entry
[M]
[MnIII
[RhIII
(F20-tpp)I]
[RuII
(ttp)(CO)]
[FeIII
(salen)Cl]
[FeIII
(tpp)Cl]
[FeIII
(F20-tpp)Cl]
[FeII(tpp)][d]
[FeII(F20-tpp)][d]
Conversion [%][b]
Yield [%][c]
1
2
3
4
5
6
7
8
G
E
0
0
0
40
60
100
50
80
0
0
0
60
80
95
75
85
6
7
8
9
92
93
92
93
E
G
N
E
R
G
N
ACHTUNGTRENNUNG
T
ACHTUNGTRENNUNG
R
ACHTUNGTRENNUNG
C
ACHTUNGTRENNUNG
[a] All reactions were performed with styrene (0.60 mmol), azide
(0.20 mmol), metal complex (0.004 mmol), and 4 ꢁ molecular sieves
(60 mg) in anhydrous ClCH2CH2Cl (1 mL) under N2. [b] Determined by
crude 1H NMR spectroscopy. [c] Yield of isolated product based on con-
version. [d] Formed in situ by NaBH4 reduction. DCE: 1,2-dichloro-
ethane.
10
94
[a] All reactions were performed with styrene (0.60 mmol), azide
(0.20 mmol), [FeIII
(F20-tpp)Cl] (0.004 mmol), and 4 ꢁ molecular sieves
AHCTUNGTRENNUNG
(60 mg) in anhydrous ClCH2CH2Cl (1 mL) under N2. [b] Yield of isolated
product. [c] 1.00 mmol styrene was used.
(H2F20-tpp=meso-tetrakis(pentafluorophenyl)porphyrin),
and [RuII
ACHTUNGTRENNUNG(ttp)(CO)] (H2ttp=meso-tetrakisAHCTUNGTERNN(UGN p-tolyl)porphyr-
in) were found to be inactive and in each case no product
was detected with TsN3 recovered quantitatively under the
employed experimental conditions (Table 1, entries 1–3).
tuted styrenes, including those with electron-withdrawing or
electron-donating substituents, gave the corresponding aziri-
dines in excellent yields (92–95%, Table 2, entries 4–10) and
with complete azide consumption.
[FeIII
ACHTUNGTRENNUNG
G
Sulfimidation[14] is a useful nitrene/imido transfer reaction.
In this work, both diethyl sulfide and thioanisoles were con-
verted to sulfimides in high yields by TsN3 and with [FeIII-
was employed as the catalyst, the aziridine product was ob-
tained in 80% yield with 60% azide consumption (Table 1,
entry 5). The use of [FeIII
N
ACHTUNGTRENNUNG
porphyrin ligand gave the aziridine product in 95% yield
and with complete azide consumption in 12 h (Table 1,
ACHTUNGTRENNUNG
(Table 3, entry 1). The sulfimidation of substituted thioani-
soles is affected by the substituent group on the aryl ring.
Strong electron-withdrawing groups such as NO2 led to a
longer reaction time (Table 3, entry 4 versus entry 8). With
the other nitrogen sources, p-nitrobenzenesulfonyl azide
(Table 3, entry 9), diphenyl phosphoryl azide (DPPA,
Table 3, entry 10), phenyl carboxyl azide (Table 3, entry 11),
and 4-nitrophenyl azide (Table 3, entry 12), the correspond-
ing sulfimidation reactions also proceeded smoothly.
entry 6). The two iron(II) porphyrins [FeII
ACHTUNGTRENNUNG
[FeII
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
lower than that displayed by their parent iron
complexes (Table 1, entries 7 and 8).
ACHTUNGTREN(NGNU III) porphyrin
With [FeIII
ACHTUNGTRENNUNG(F20-tpp)Cl] as catalyst, other azides, such as
methanesulfonyl azide (MsN3), p-acetamidobenzenesulfonyl
azide (p-ABSA), and 4-nitrophenyl azide, were also exam-
ined as the nitrogen source (Table 2, entries 1–3). TsN3 gave
the best result when compared with MsN3, p-ABSA, and 4-
nitrophenyl azide. With TsN3 as the nitrogen source, substi-
Aziridination of aliphatic alkenes could also be accom-
plished with the “ACHTNUGRTENNUG ACHTUGNTREN(NUNG F20-tpp)Cl]+sulfonyl or aryl azide”
[FeIII
protocol. Compared with the reactions with styrenes, aziridi-
nation of aliphatic alkenes is conspicuously difficult due to
Chem. Eur. J. 2010, 16, 10494 – 10501
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10495

C.-M. Che and Y. Liu
Table 3. Sulfimidation of sulfides.[a]
Table 4. Aziridination of aliphatic alkenes.[a]
Entry
1
Substrates
Products
Yield [%][b]
Entry
Substrates
Products
t
Yield
[%][b]
[h]
60 (35 cvn[c]
70 (50 cvn[c]
75 (55 cvn[c]
85
)
)
)
1[c]
2
12
12
0
2
3
4
96
3
4
5
6
24
24
24
24
94
95
95
93
5
6
83
75
7
8
90
80
7
8
24
48
92
90
[a] All reactions were performed with alkene (1.00 mmol), azide
(0.20 mmol), [FeIII
(F20-tpp)Cl] (0.004 mmol), and 4 ꢁ molecular sieves
AHCTUNGTRENNUNG
9
24
24
24
95
91
76
(60 mg) in anhydrous ClCH2CH2Cl (1 mL) under N2. [b] Yield of isolated
product based on conversion. [c] Conversion (cvn) was determined by
1
crude H NMR spectroscopy.
10
11
azide consumption (Table 4, entry 6). Although tosyl azide
was found to give 2-(tosylamino)-1-phenylethanone from a-
(trimethylsiloxy)styrene (Table 4, entry 7), the amidation of
2-(trimethylsiloxy)-1-decene could only be accomplished by
using 4-nitrobenzenesulfonyl azide as the nitrogen source,
which gave 1-(4-nitrobenzenesulfonylamino)-2-decanone in
80% yield and with complete azide consumption (Table 4,
entry 8).
Interestingly, allylic amidation/amination occurred with
no aziridine detected when a-methylstyrenes were used as
substrates. The results are listed in Table 5. In the literature,
there are only a few reports on the direct allylic amidation
of substituted a-methylstyrenes.[1a,4d,f] With TsN3, substituted
a-methylstyrenes gave the corresponding allylic sulfamides
as the major products (Table 5, entries 1–8, 70–82% yields).
The reaction of the structurally similar 2-isopropenylnaph-
thalene (Table 5, entry 9) gave the allylic amidation product
in 78% yield. The reactions of a-methylstyrene with the
other nitrogen sources, p-ABSA (Table 5, entry 10) and p-
nitrobenzenesulfonyl azide (Table 5, entry 11), also gave the
allylic amidation products in good yields. Allylic amination
of 4-tert-butyl a-methylstyrene was accomplished in 83%
product yield when 4-nitrophenyl azide was used as the ni-
trogen source (Table 5, entry 12). Both allylic amination and
hydroxyamination products were obtained when a-methyl-
styrene (Table 5, entry 13) and 2-isopropenylnaphthalene
(Table 5, entry 14) were employed as the substrates and by
12
36
78
[a] All reactions were performed with sulfide (0.60 mmol), azide
(0.20 mmol), [FeIII
(F20-tpp)Cl] (0.004 mmol), and 4 ꢁ molecular sieves
(60 mg) in anhydrous ClCH2CH2Cl (1 mL) under N2. [b] Yield of isolated
product. [c] Without catalyst.
ACHTUNGTRENNUNG
the low reactivity of aliphatic alkenes. For example, aziridi-
nation of styrene with MsN3 could be accomplished in 75%
yield with complete azide consumption (Table 2, entry 1),
whereas under similar conditions the aziridination of allyl-
benzene can only be achieved in 60% yield with 35% azide
consumption (Table 4, entry 1). With the other azides p-
ABSA and TsN3, both the azide consumption and product
yield in each case were improved (Table 4, entries 2 and 3).
The best result was obtained when p-nitrobenzenesulfonyl
azide was used as the nitrogen source. The aziridination of
allylbenzene and 1-decene by p-nitrobenzenesulfonyl azide
was accomplished in product yields of 85 and 83%, respec-
tively, and with complete azide consumption (Table 4, en-
tries 4 and 5). 4-Nitrophenyl azide gave an aziridination
product from allylbenzene in 75% yield with complete
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Iron Porphyrin Catalysts
FULL PAPER
Table 5. Allylic amidation of a-methylstyrenes.[a]
Table 5. (Continued)
Entry
Substrates
Products
Yield
[%][b]
18[c,d]
83
Entry
Substrates
Products
Yield
[%][b]
[a] Reactions were performed with a-methylstyrene (0.80 mmol), azide
(0.20 mmol), [FeIII
(F20-tpp)Cl] (0.004 mmol), and 4 ꢁ molecular sieves
(60 mg) in anhydrous ClCH2CH2Cl (1 mL) under N2. [b] Yield of isolated
product. [c] 1.00 mmol olefin was used. [d] Heated to reflux for 48 h.
AHCTUNGTRENNUNG
1
2
80
81
using 4-nitrophenyl azide as the nitrogen source. 2-Phenyl-2-
butene (Table 5, entry 15) gave only one allylic amidation
product in 68% yield without any amidation at the two ter-
minal methyl groups. In addition, the amidation was exclu-
sively found at the methylene group of a-methylenetetralin
(Table 5, entry 16). Unfortunately, this reaction was found
not to be applicable to 2-methyl-2-alkyl-substituted terminal
alkenes. 2-Methyl-4-phenyl-1-butene (Table 5, entry 17) and
2-methyl-1-decene (Table 5, entry 18) gave aziridines as the
major products and without any allylic amination product
detected.
3
4
5
6
7
82
72
70
78
74
À
Direct functionalization of saturated C H bonds is ap-
pealing in organic synthesis. At first, we examined the ami-
dation of ethylbenzene by using sulfonyl azides (e.g., MsN3,
TsN3, p-ABSA, and p-nitrobenzenesulfonyl azide) as the ni-
trogen source; however, no amidation product was obtained
in each of the reactions studied. Eventually, amination of
ethylbenzene was achieved to give 4-nitro-N-(1-phenyl-
8
70
78
72
9
AHCTUNGTREGeNNUN thyl)benzenamine in 71% yield and with complete azide
10
consumption when 4-nitrophenyl azide was employed
(Table 6, entry 1). Starting with 4-nitrophenyl azide, the ben-
À
zylic C H bonds of tetralin (Table 6, entry 2), diphenylme-
11
83
83
thane (Table 6, entry 3), fluorene (Table 6, entry 4), and xan-
thene (Table 6, entry 5) were successfully aminated in mod-
erate to good yields. Importantly, amination of the unreac-
12[c]
À
tive saturated C H bonds of cycloheptane (Table 6, entry 6),
cyclooctane (Table 6, entry 7), and adamantane (Table 6,
entry 8) was accomplished in moderate product yields. In
the case of adamantane, the amination reaction occurred at
32
49
26
55
68
17
13[c]
À
À
38 C H bonds with no products derived from 28 C H bonds
detected. Similarly, the amination of 1-cyclohexylallene also
À
occurred at the 38 C H bond with the allene moiety and 28
À
C H bonds remaining intact (Table 6, entry 9).
14[c]
As reported in the literature, microwave irradiation could
significantly shorten the time for completion of a reaction.[15]
Thus, some of the sluggish substrates were selected for the
catalysis under microwave irradiation and the results are de-
picted in Table 7. In this work, microwave irradiation was
found to shorten the reaction time by up to 16-fold. As an
example, the reaction of styrene with DPPA was slow under
thermal conditions, as the conversion of DPPA was only
20% even after heating at reflux in ClCH2CH2Cl for 24 h.
Under microwave irradiation, this reaction could be com-
pleted in 2.5 h (Table 7, entry 1), and the time to complete
the aziridination of both styrene and 1-decene was short-
ened greatly (Table 7, entries 2–4). Allylic amidation of a-
15
16
67
61
17[c,d]
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C.-M. Che and Y. Liu
[a]
Table 7. Microwave-accelerated nitrogen group transfer reactions.[a]
À
Table 6. Saturated C H bond activation.
Entry
Substrates
Products
t
Conv.
[%][b]
Yield
[%][c]
Entry
Substrates
Products
t
Yield
[%][b]
[h]
[h]
1
2
36
36
100
100
71
73
1
2.5
75
2
1
3
93
82
3[c]
3
4
5
48
24
24
100
100
100
72
80
78
4[c]
5[d]
2
75
75
1.5
6[d]
7[d]
8[d]
1.5
1.5
1.5
78
70
73
6[d]
7[d]
48
48
63
65
65
64
9[d]
10
1.5
2.5
74
76
8
9
48
24
60
68
64
100
11
3
5
75
70
[a] Reactions were performed with alkane (2.00 mmol), 4-nitrophenyl
azide (0.20 mmol), [FeIII
(F20-tpp)Cl] (0.004 mmol), and 4 ꢁ molecular
AHCTUNGTRENNUNG
sieves (60 mg) in anhydrous ClCH2CH2Cl (1 mL) under N2. [b] Deter-
mined by crude 1H NMR spectroscopy. [c] Yield of isolated product
based on conversion. [d] 5.00 mmol cycloalkane was used.
12[e]
13[f]
14[e]
3.5
6
64
65
methylstyrenes was finished in 1.5 h with TsN3 as the nitro-
gen source (Table 7, entries 5–9). Compared with the reac-
tion conducted under thermal conditions, microwave irradia-
tion accelerated the reaction by nearly 16-fold (24 versus
1.5 h). Not surprisingly, sulfimidation of thioanisole was also
accelerated under microwave irradiation conditions with
TsN3 or 4-nitrophenyl azide used as the nitrogen source
(Table 7, entries 10 and 11). Notably, amination of the un-
[a] Reactions were performed with alkene (0.30 mmol), azide
(0.10 mmol), [Fe(F20-tpp)Cl] (0.002 mmol), and 4 ꢁ molecular sieves
(40 mg) in anhydrous ClCH2CH2Cl (1.0 mL). [b] Yield of isolated prod-
uct. [c] 0.50 mmol olefin was used. [d] 0.40 mmol olefin was used.
[e] 1.00 mmol alkane was used. [f] 2.5 mmol alkane was used.
AHCTUNGTRENNUNG
À
reactive saturated C H bonds of cycloheptane and adaman-
as the by-product whereas iminophenyliodinanes release
PhI as a side product. The drawbacks of organic azides in-
clude their difficulty in undergoing decomposition and their
low oxidizing power, which is not favorable for the genera-
tion of highly active oxidative imido/nitrene reaction inter-
mediates.
tane can be accomplished in 64 and 65% yields, respectively
(4-nitrophenyl azide as the limiting reagent) with complete
azide conversion within a reaction time of 3.5 and 6 h, re-
spectively. For all of the substrates, their reactions under mi-
crowave irradiation gave comparable product yields (slightly
lower) to those obtained under thermal conditions within a
reaction time shortened by up to 16-fold.
The reactions depicted in Table 5 might go through direct
À
allylic C H bond insertion or rearrangement of aziridines
Compared with the reported nitrene/imido transfer reac-
tions using iminophenyliodinanes (e.g., PhI=NTs) as the ni-
trogen source, the organic azides in our work have been
found to give good results for both the aziridination and sul-
fimidation reactions described herein. In the context of
green chemistry, organic azides only generate nitrogen gas
(Scheme 1). In this work, the allylic amidation product of 2-
phenyl-2-butene (Table 5, entry 15) was obtained in 68%
yield without any amidation at the two terminal methyl
groups detected [Scheme 1, Eq. (1)]. This reveals that the
product is derived from the ring opening of the aziridine in-
termediate [Scheme 1, Eq. (2)]. The reaction can be viewed
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Iron Porphyrin Catalysts
FULL PAPER
plexes. Very recently, Zhang and co-workers[6b,f,g] reported
À
inter- and intramolecular amination of saturated C H bonds
with CoII-porphyrin as the catalyst and with organic azides
as the nitrogen source. However, iron complex-catalyzed ni-
À
trene/imido group insertions into saturated C H bonds are
sparse in the literature.[11d,g,h] In addition, most of the report-
ed reactions use iminophenyliodinanes (e.g., PhI=NTs) as
the nitrogen source. Up to now, there have only been a few
reports on the use of organic azides as the nitrogen source
[4c,6b,19d]
À
for the activation of unactivated C H bonds.
Also,
lower product yields are usually encountered in the aziridi-
nation of aliphatic alkenes by organic azides using metal
complexes as catalysts.[4–6] Thus, the protocol “[FeIII
ACHTNUGTRENNUG ACHTUNGTRENNUNG(F20-
tpp)Cl]+4-nitrophenyl azide” described in this work is
useful in that it is a simple system and yet can realize inter-
À
molecular amination of saturated C H bonds, even the un-
reactive ones of cycloalkanes and adamantane, with accepta-
ble product yields.
Based on the similar results obtained for the aziridination
of styrene catalyzed by ironACHTNUTRGNE(UNG III) porphyrin and its iron(II)
Scheme 1. Mechanistic study on direct allylic amidation.
counterpart with tosyl azide as the nitrogen source, the ni-
trene/imido insertion and transfer reactions described in this
work might go through a reactive iron-imido/nitrene inter-
mediate generated by the reaction of organic azide with [Fe-
À
as a formal direct allylic C H bond insertion. When 4-nitro-
phenyl azide was employed as the nitrogen source, the aziri-
dine intermediate could be isolated in the course of the re-
action. Thus, the allylic amination/amidation and hydroxy-
AHCTUNGTRENNUNG
(F20-tpp)]n+ (n=0, 1) generated in situ. As suggested by
Mansuy and co-workers, the Fe(V) imido species containing
A
a porphyrin ligand, if it exists, should be highly reactive and
[22]
À
hydrolysis of the aziridine intermediate, respectively
[Table 5, entry 13, and Scheme 1, Eq. (3)]. In addition, the
result of the amination reaction of a-methylenetetralin
(Table 5, entry 16) also supports the hypothesis depicted in
Scheme 1 [Eq. (4)].
able to rapidly react with saturated C H bonds. In this
work, this kind of Fe(V)-imido intermediate is unlikely as
À
the nitrene insertion into the C H bonds of ethylbenzene
cannot be accomplished with TsN3 as the nitrogen source.
Thus, the iron(IV) imido/iron(II) nitrene species is a more
reasonable reaction intermediate for the catalysis described
in this work. In our previous studies on nitrene transfer re-
General remark: In the literature, there are many reports
on metal-catalyzed nitrene/imido group transfer and inser-
tion reactions using organic azides as the nitrogen source,
but the majority of the reported reactions focus on aziridi-
nation of alkenes and sulfimidation of sulfides. Over the
ACTHNUTRGNEUNG
actions with [FeII(Cl3terpy)2]2+ (Cl3terpy=4,4’,4’’-trichloro-
2,2’:6’,2“-terpyridine) as the catalyst and PhI=NTs as the ni-
trogen source, the [Fe(Cl3terpy)2A
(NTs)]2+ reactive inter-
mediate was characterized by ESIMS analysis.[11h] Aryl im-
idoiron(IV)/aryl nitrene iron(II) might have enough activity
A
CHTUNGTRENNUNG
past few decades, functionalization of unactivated C H
ACHTUNGTRENNUNG
À
bonds through metal-catalyzed nitrene/imido group inser-
tion has been realized and a number of metal catalysts were
reported to give good results. In the 1980s, Breslow,[16a] Man-
suy[16b] and co-workers reported nitrene transfer reactions
catalyzed by MnIII and FeIII complexes of tpp with PhI=
NTs as the nitrogen source. In recent years, Du Bois and co-
to undergo nitrene insertion into saturated C H bonds. This
hypothesis has support from the recent work by King and
Betley,[23] which revealed that amination of the primary C
H bond of coordinated trimesityldipyrromethene can occur
via an aryl imidoiron(IV) intermediate.
À
workers developed dirhodiumACTHNUTRGENUGN(II,II) complexes as effective
À
catalysts for the functionalization of saturated C H bonds
with practical interest.[10b,17] In our group, ruthenium porphy-
rin complexes have been demonstrated to catalyze aziridina-
Conclusion
The commercially available and air stable [FeIII
ACTHNUTRGNEUGN(F20-tpp)Cl]
À
tion of alkenes and amidation of saturated C H bonds with
complex is a useful catalyst for imido/nitrene transfer reac-
tions with sulfonyl and aryl azides as the nitrogen source.
Aziridination of alkenes, sulfimidation of sulfides, allylic
amination of a-methylstyrenes, and amination of unactivat-
iminophenyliodinanes as nitrogen source.[1d,18] Other metal
complexes, such as those of Cu,[19] Ag,[20] and Au,[21] have
also been revealed to display potent activity toward func-
À
À
tionalization of unactivated C H bonds by nitrene insertion
reactions. Cenini, Katsuki, and their co-workers reported in-
ed saturated C H bonds can all be accomplished in good to
excellent product yields. In addition, the reactions can be
significantly accelerated by up to 16-fold under microwave
irradiation conditions.
À
termolecular amination of saturated C H bonds with organ-
ic azides catalyzed by ruthenium[4a,g,5e] or cobalt[4a–c,e] com-
Chem. Eur. J. 2010, 16, 10494 – 10501
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10499

C.-M. Che and Y. Liu
Acknowledgements
Experimental Section
This work was supported by the Hong Kong Research Grants Council
(HKU1/CRF/08 and HKU700708) and the Areas of Excellence Scheme
established under the University Grants Committee of the Hong Kong
Special Administrative Region, China (AoE/P-10/01).
General: Reagents were obtained commercially and used without further
purification unless otherwise indicated. 1,2-Dichloroethane (DCE) was
freshly distilled from calcium hydride under a nitrogen atmosphere. Mo-
lecular sieves (4 ꢁ) were dried at 3008C for 3 h prior to use. Flash
column chromatography (silica gel, 230–400 mesh) was performed with a
gradient solvent system (EtOAc/n-hexane as eluent unless specified oth-
erwise). 1H and 13C NMR spectra were recorded on a Bruker DPX-500
or DPX-400 spectrometer. Chemical shifts (d ppm) were determined
with tetramethylsilane (TMS) as internal reference. Mass spectra were
recorded on a Finnigan MAT 95 mass spectrometer. Microwave irradia-
tion experiments were conducted with a CEM Discover Synthesis Unit
(CEM Corp., Matthews, NC). Caution! Organic azides are potentially ex-
plosive and should be handled with great care.
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General procedure for aziridination of styrenes: 1,2-Dichloroethane
(1 mL) was added to
a mixture of styrene (0.60 mmol), azide
(0.20 mmol), catalyst (0.004 mmol), and 4 ꢁ molecular sieves (60 mg).
Then the reaction mixture was heated to reflux and kept at this tempera-
ture under nitrogen. After complete consumption of the azide as moni-
tored by TLC, the mixture was concentrated under reduced pressure and
the residue was purified by flash column chromatography. In some cases,
the consumption of azide was determined by crude 1H NMR spectrosco-
py with 1,1-dipenylethene as the internal standard.
General procedure for sulfimidation of sulfides: 1,2-Dichloroethane
(1 mL) was added to a mixture of sulfide (0.60 mmol), azide (0.20 mmol),
catalyst (0.004 mmol), and 4 ꢁ molecular sieves (60 mg). Then the reac-
tion mixture was heated to reflux and kept at this temperature under ni-
trogen. After complete consumption of the azide as monitored by TLC,
the mixture was concentrated under reduced pressure and the residue
was purified by flash column chromatography.
General procedure for aziridination of aliphatic alkenes: 1,2-Dichloro-
ethane (1 mL) was added to a mixture of alkene (1.00 mmol), azide
(0.20 mmol), catalyst (0.004 mmol), and 4 ꢁ molecular sieves (60 mg).
Then the reaction mixture was heated to reflux and kept at this tempera-
ture under nitrogen. After complete consumption of the azide as moni-
tored by TLC, the mixture was concentrated under reduced pressure and
the residue was purified by flash column chromatography. In some cases,
the consumption of azide was determined by crude 1H NMR spectrosco-
py with 1,1-dipenylethene as the internal standard.
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and the residue was purified by flash column chromatography.
À
General procedure for amination of saturated C H bonds: 1,2-Dichloro-
ethane (1 mL) was added to
a
mixture of saturated hydrocarbon
(2.00 mmol), azide (0.20 mmol), catalyst (0.004 mmol), and 4 ꢁ molecular
sieves (60 mg). Then the reaction mixture was heated to reflux and kept
at this temperature under nitrogen. After complete consumption of the
azide as monitored by TLC, the mixture was concentrated under reduced
pressure and the residue was purified by flash column chromatography.
In some cases, the consumption of azide was determined by crude
1H NMR spectroscopy with 1,1-dipenylethene as the internal standard.
General procedure for nitrogen transfer reactions under microwave irra-
diation conditions: (Caution! All of the reactions were conducted by
using 16 mg organic azide in 1 mL 1,2-dichloroethane in a 10 mL glass
vial.)
A mixture of alkene, sulfide or alkane (0.30, 0.30, or 1.00–
2.50 mmol), azide (0.10 mmol), catalyst (0.002 mmol), and 4 ꢁ molecular
sieves (40 mg) was suspended in 1,2-dichloroethane (1.0 mL) in a 10 mL
glass vial equipped with a small magnetic stirring bar. The mixture was ir-
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reaction was monitored by TLC. The mixture was then concentrated
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Received: March 5, 2010
Published online: July 20, 2010
Chem. Eur. J. 2010, 16, 10494 – 10501
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10501