Iron-Catalyzed Dioxygenation of Alkenes and Terminal Alkynes by using (Diacetoxyiodo)benzene as Oxidant

Article abstract of DOI:10.1002/adsc.201500681

An iron-catalyzed syn-diacetoxylation of alkenes and 1,2-oxyacetoxylation of terminal alkynes has been developed using (diacetoxyiodo)benzene as oxidant. A broad range of internal and terminal alkenes, including electron-rich as well as electron-deficient alkenes, gave the desired products in good to excellent yields with high diastereoselectivity (up to >99:1 dr). In addition the high catalytic activity of iron catalysis for the 1,2-oxyacetoxylation of terminal alkynes is also reported. The roles of catalyst, oxidant and other reaction parameters were evaluated for activation of the unsaturated bond.

Full text of DOI:10.1002/adsc.201500681

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DOI: 10.1002/adsc.201500681
Iron-Catalyzed Dioxygenation of Alkenes and Terminal Alkynes
by using (Diacetoxyiodo)benzene as Oxidant
B. T. V. Srinivas,a Vikas S. Rawat,a and Bojja Sreedhara,*
a
Inorganic & Physical Chemistry Division, Indian Institute of Chemical Technology (Council of Scientific & Industrial
Research), Hyderabad – 500007, India
Fax: (+91)-40-2716-0921; e-mail: sreedharb@iict.res.in
Received: July 17, 2015; Revised: September 7, 2015; Published online: November 17, 2015
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201500681.
Abstract: An iron-catalyzed syn-diacetoxylation of iron catalysis for the 1,2-oxyacetoxylation of terminal
alkenes and 1,2-oxyacetoxylation of terminal alkynes alkynes is also reported. The roles of catalyst, oxi-
has been developed using (diacetoxyiodo)benzene as dant and other reaction parameters were evaluated
oxidant. A broad range of internal and terminal al- for activation of the unsaturated bond.
kenes, including electron-rich as well as electron-de-
ficient alkenes, gave the desired products in good to
excellent yields with high diastereoselectivity (up to Keywords: alkenes; alkynes; iodine; iron; oxygena-
>99:1 dr). In addition the high catalytic activity of tion
Introduction
developed.[9–19] However, these non-heme iron
enzyme catalysts have poor thermal stability under
The metal-catalyzed cis-dihydroxylation of alkenes is oxidative conditions and often result in low cis-diol
one of the most important and vastly employed meth- selectivity. Hence, simultaneously transition metals
À
ods for C O bond formation in modern organic syn- like palladium, copper and Lewis acid like BF3·OEt2-
thesis. The presence of a 1,2-diol unit in many syn- catalyzed methods for syn-diacetoxylation of alkenes
thetically important intermediates as well as in natu- were developed by using hypervalent iodine reagents
ral products makes this process highly valuable for or- as oxidant.[20] These methods resulted in the forma-
ganic chemists.[1] A large number of such cis-dihy- tion of the 1,2-diacetate product with good to excel-
droxylation reactions are usually carried out by using lent diastereoselectivity. The formed 1,2-diacetate is
OsO4 as catalyst.[2] In particular, the Sharpless asym- a valuable precursor for 1,2-diols. More recently,
metric dihydroxylation protocol has found wide appli- Brønsted acids like triflic acid were also reported to
cations in the synthesis of complex natural pro- catalyze this reaction efficiently.[21] However, in com-
ducts.[2b–f] Moreover, the use of only catalytic amounts parison to various reports on non-heme iron cis-dihy-
of OsO4 in these methods makes them suitable for droxylation catalysis,[9–19] the relative study on iron-
large scale synthesis.[3] However, osmium compounds catalyzed diacetoxylation of alkenes with hypervalent
are highly toxic and expensive, hence there is always iodine reagents have not been reported so far. Thus,
a demand to develop alternative, less toxic and eco- we herein report an iron-catalyzed vicinal diacetoxy-
nomical transition metal-catalyzed procedure for cis- lation of alkenes by using PhI(OAc)2 as the oxidant.
dihydroxylation of alkenes. As a result of this,
a number of transition metal-catalyzed methods has
been developed by using ruthenium,[4–6] manganese,[7,8] Results and Discussion
and iron[9–13] complexes for the cis-dihydroxylation of
alkenes.
To develop this protocol, we initially started screening
Being economical and environmentally benign, various iron precursors for the diacetoxylation of sty-
lately the use of iron catalysis for cis-dihydroxylation rene (1a) using PhI(OAc)2 as oxidant. The results
of the alkene became a topic of immense interest. from these studies are shown in Table 1. To our de-
Thus, a series of non-heme iron-complexes (Rieske light, various Fe(II) and Fe(III) salts afforded the de-
dioxygenases) with H2O2 or O2 as oxidant has been sired 1-phenylethane-1,2-diyl diacetate (2a) in moder-
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B. T. V. Srinivas et al.
Table 1. Optimization of the reaction conditions for the di-
acetoxylation of styrene 1a in the presence of PhI(OAc)2.[a]
On the other hand, the reaction in H2O as solvent af-
forded only 10% of 2a (Table 1, entry 16). Further-
more, the reaction is found to be susceptible to tem-
perature changes, for example, at room temperature
only 42% of 2a was formed (Table 1, entry 18), while
an increase in temperature to 1008C from 808C (opti-
mized conditions) reduced the reaction yield to 75%
(Table 1, entry 19). A control reaction without any
iron catalyst resulted in a very low (2%) yield of 2a
(Table 1, entry 20).[22] In the absence of an oxidant it
was observed that the reaction was not initiated
(Table 1, entry 21).
Entry Catalyst
Solvent Temp. [8C] Yield [%][b]
1
2
3
4
FeBr2
FeCl3
Fe2O3
Fe(acac)2
Fe(OAc)2
AcOH 80
AcOH 80
AcOH 80
AcOH 80
AcOH 80
38
21
6
15
5
57
Next, we focused our attention to examine the gen-
erality of this diacetoxylation protocol. As shown in
Table 2, a variety of terminal alkenes was diacetoxy-
lated facilely and efficiently.
6
7
8
9
Fe2(SO4)3·xH2O AcOH 80
acetylferrocene AcOH 80
5
6
52
Fe(OTf)2
AcOH 80
Fe(ClO4)2·xH2O AcOH 80
46
10
11
12
13
14
15
16
17
18
19
20
21
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
–
AcOH 80
DCM 40
CH3CN 80
AcOH 80
AcOH 80
AcOH 80
39[c]
25
Both electron-deficient ones like 4-bromostyrene
and electron-rich ones like 3-vinylanisole derivatives
gave the desired diacetate products 2e and 2c in ex-
cellent yields of 85% and 93%, respectively (Table 2,
entries 3 and 5). Simple aliphatic alkenes such as 1-
octene also gave the corresponding diacetate product
2i in good yield of 88% (Table 2, entry 9). Notably, an
anisole derivative 2c, known to be sensitive to some
of the hypervalent iodine reagents, was also tolerated
well under these reaction conditions (Table 2,
entry 3).[23] Subsequently, a series of internal alkenes
was diacetoxylated to further explore the scope and
diastereoselectivity of this protocol. As shown in
Table 3, various 1,2-disubstituted alkenes under the
optimized reaction conditions led to the formation of
dioxygenated products (2j–2m) bearing vicinal stereo-
genic centers with good diastereoselectivity.
37
60[d]
62[e]
67[f]
10
H2O
80
AcOH 80
AcOH 25
AcOH 100
AcOH 80
AcOH 80
77[g]
42[g]
75[g]
2[h]
0[i]
Fe(OAc)2
[a]
Reaction conditions: styrene (1 mmol), PhI(OAc)2
(1.2 mmol), and catalyst (10 mol%) in solvent (3 mL) for
18 h.
Isolated yield.
5 mol% of catalyst loading.
Reaction in wet AcOH.
With 1 mmol of H2O.
With 3 mmol of H2O.
0.5 mL of Ac2O was added to the reaction mixture after
18 h.
Reaction without catalyst.
[b]
[c]
[d]
[e]
[f]
Indene shows very high reactivity towards the diox-
ygenation reaction due to its inherent ring strain
[g]
[h]
[i]
Table 2. Iron-catalyzed diacetoxylation of terminal alk-
enes.[a]
Reaction without PhI(OAc)2.
ate to good yields in AcOH as solvent at 808C.
Among the screened Fe(II) and Fe(III) salts,
Fe(OAc)2 clearly came out to be the catalyst of
choice for this reaction yielding 57% of 2a (Table 1,
entry 5). Furthermore, solvent screening shows that
AcOH, CH2Cl2 and CH3CN are compatible solvents
for this transformation affording 57%, 25%, and 37%
yields of 2a, respectively (Table 1, entries 5, 11, and
12). The use of wet acetic acid improved the reaction
yield of 2a to 60% (Table 1, entry 13) along with for-
mation of hydroxyacetate product, whilst the maxi-
mum conversion rate was obtained by the addition of
3 equivalents of H2O in the reaction (67% of 2a,
Table 1, entry 15).
Entry
Alkene
1
2
Yield [%][b]
1
2
3
4
5
6
7
8
9
styrene
1a
1b
1c
1d
1e
1f
1g
1h
1i
2a
2b
2c
2d
2e
2f
2g
2h
2i
77
90
93
72
85
85
72
65
88
4-methylstyrene
3-vinylanisole
4-chlorostyrene
4-bromostyrene
2-vinylnaphthalene
2-phenylpropene
4-acetoxystyrene
1-octene
[a]
Reaction conditions: alkene (1.0 mmol), PhI(OAc)2
(1.2 mmol), AcOH (3 mL), H2O (3.0 mmol), and
Fe(OAc)2 (0.1 mmol) for 18 h at 808C; then 0.5 mL of
Ac2O at room temperature for overnight.
The treatment of this reaction mixture with 0.5 mL
of Ac2O after 18 h allows convenient isolation of di-
acetate product 2a in 77% yield (Table 1, entry 17).
[b]
Isolated yield.
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Iron-Catalyzed Dioxygenation of Alkenes and Terminal Alkynes
Table 3. Iron-catalyzed dioxygenation of internal alkenes.[a]
[a]
Reaction conditions: alkene (1.0 mmol), PhI(OAc)2
Scheme 1. Plausible mechanism for the Fe(OAc)2/
PhI(OAc)2-mediated diastereoselective diacetoxylation of
alkenes.
(1.2 mmol), AcOH (3 mL), H2O (3.0 mmol), and
Fe(OAc)2 (0.1 mmol) for 18 h at 808C; then 0.5 mL of
Ac2O at room temperature for overnight.
[b]
Isolated yield.
[c]
Diastereomeric ratio (syn/anti) determined by 1H NMR
Fe(III)(OAc)3 by PhI(OAc)2, that in turn coordinates
and inserts olefin to form the intermediate I and II.
The insertion of Fe(III)(OAc)3 to olefin resulted in
spectroscopy.
(Table 3, 2k). The diacetoxylation of indene results in the trans-addition product (II). Next, the formation of
the formation of syn-diacetate product 2k in 88% acetoxonium ion (III) from II occurs via an SN2-type
yield with good diastereoselectivity of 14.3:1 dr (syn/ reductive elimination process. This process also re-
anti). The reaction of 2,3,4,5-tetrahydro-1,1’-biphenyl sults in the formation of Fe(I)(OAc), that is oxidized
as substrate resulted exclusively in the formation of to the active catalytic Fe(III) species by PhI(OAc)2.
a tertiary alcohol 2m even after treatment with Ac2O. The reaction of the intermediate acetoxonium ion
The formation of this tertiary alcohol under these re- (III) with H2O will then lead to the formation of the
action conditions shows an agreement with Kusumo- hydroxyacetates. These hydroxyacetates are subse-
toꢁs observations.[24] On the other hand, reactions with quently acylated to the corresponding diacetate by
substrates having internal double bonds like cyclohex- Ac2O in the presence of Fe(III) or Fe(II) species pres-
ene and 3-hexene led to the formation of multiple in- ent in the reaction mixture. The presence of Fe(II)
separable products.
and Fe(III) species was confirmed by UV-Vis spec-
Based on the observations during this study and troscopy. The UV-Vis spectrum of a yellow-coloured
previous reports on metal-catalyzed diacetoxyla- solution drawn from the reaction mixture after one
tion,[20,25]
Scheme 1.
a
plausible mechanism is outlined in hour showed a weak band at 410 nm and a broad
band around 330–350 nm, that are characteristic of
In one of our first observations during the optimi- a typical Fe(III) acetate complex,[29] while Fe(II) ace-
zation of the reaction conditions, we noticed the for- tate shows a well-defined peak at 330–350 nm.
mation of isotropic mixture of hydroxyacetate inter-
Recently, Gade et al.[21] reported that protons act as
mediates along with the 1,2-diacetate product (2a) the active catalytic species in the metal salts (Lewis
from styrene (1a) in wet acetic acid. Based on the I2/ acids)-catalyzed diacetoxylation of alkenes using
silver salt-mediated Woodward–Prevost reaction PhI(OAc)2 as the oxidant. In contrast to our proposed
mechanism,[21,26] the formation of these hydroxyace- mechanism, it is still possible that a strong Brønsted
tates indicates the involvement of an acetoxonium ion acid can be generated by the metal/AcOH system
intermediate in this reaction.[20,27] Furthermore, Va- that may have catalyzed this reaction. To affirm this
nAtta et al. reported the iron-catalyzed oxygenation a control proton-trapping experiment was carried out
of alkenes by iodosylbenzene suggesting that the for- and it was found that addition of proton-trapping
mation of acetoxonium ion here can occur via an agents
like
1,8-bis(dimethylamino)naphthalene
Fe(II)-Fe(III) catalytic cycle (Scheme 1).[28] A similar (proton-sponge) and Bu4NOAc led to either partial or
oxidation of Cu(II) to Cu(III) by PhI(OAc)2 was also complete inhibition of the reaction (Table 4).[30]
reported by Chai et al. in their work on the diacetoxy-
Thus, it is concluded that protons also play a crucial
lation of alkenes.[25] As shown in Scheme 1, role in catalyzing the dioxygenation of alkenes. Al-
Fe(II)(OAc)2 catalyst first gets oxidized to the active though it was shown that protons are necessary in
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B. T. V. Srinivas et al.
Table 4. Effect of proton-trapping on the diacetoxylation of
methods need to be developed to directly access a-
acetoxy ketones from commercially available materi-
als. In this regard, the iron-catalyzed synthesis of a-
acetoxy ketones directly from alkynes by using
PhI(OAc)2 as oxidant seems a viable and economical
method.
We first initiated the optimization studies with phe-
nylacetylene (3a) as model substrate and various reac-
tion parameters such as catalyst, solvent and tempera-
ture were examined and the results are tabulated in
Table 5.
styrene.[a]
Entry
Additive
Yield [%][b]
1
2
3
4
5
–
57
31
trace
36
trace
5% H-sponge
100% H-sponge
5% Bu4NOAc
100% Bu4NOAc
[a]
Table 5. Optimization of the reaction conditions for the 1,2-
oxyacetoxylation of phenylacetylene 3a in the presence of
PhI(OAc)2.[a]
Reaction conditions: styrene (1 mmol), PhI(OAc)2
(1.2 mmol), and Fe(OAc)2 (10 mol%) in 3 mL of AcOH
at 808C for 18 h.
[b]
Isolated yield.
order to activate PhI(OAc)2 in this reaction.[21] How-
ever, in comparison to Brønsted acid (TfOH[21] or
HBF4[31])-catalyzed reactions, the Fe(OAc)2 as catalyst
performed better in terms of yields and diastereose-
lectivity of the reaction. For example, the diacetoxyla-
tion of indene leads to the formation of 2k with 86%
yield with 1:5.3 dr (syn/anti) in the case of TfOH,[21]
whilst with Fe(OAc)2, the reaction resulted in 88% of
2k with 14.3:1 dr.
Encouraged by the results obtained in diacetoxyla-
tion of the alkene, we further explored the dioxygena-
tion of other unsaturated systems such as alkynes by
using Fe(OAc)2-PhI(OAc)2 catalytic system. To our
delight, the dioxygenation of phenylacetylene by
Fe(OAc)2-PhI(OAc)2 catalytic system in CH3CN re-
sulted in 63% yield of 2-oxo-2-phenylethyl acetate
(4a) (a-acetoxy ketones) at room temperature
(Scheme 2). Notably this was one of the foremost ad-
vantages of the present protocol over existing meth-
ods as earlier no single catalytic system was used for
two different protocols.
Entry Catalyst
Solvent Temp. [8C] Yield [%][b]
1
2
Fe(OAc)2
FeBr3
CH3CN 25
CH3CN 25
CH3CN 25
CH3CN 25
CH3CN 25
CH3CN 25
CH3CN 25
63
19
40
trace
trace
39
3
Fe2O3
4
5
FeCl2·4H2O
FeCl3
6
7
Fe(acac)3
Fe(OTf)2
52
8
Fe(ClO4)2·xH2O CH3CN 25
49
9
–
CH3CN 25
toluene 110
trace
62
10
11
12
13
14
15
16
17
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
Fe(OAc)2
DCE
80
74
MeOH 65
47
THF
H2O
60
100
26
38
CH3CN 60
CH3CN 80
CH3CN 100
66
81
62
[a]
Reaction
conditions:
phenylacetylene
(1 mmol),
PhI(OAc)2 (1.2 mmol), and catalyst (10 mol%) in 3 mL
of solvent for 12 h.
Isolated yield.
[b]
a-Acetoxy ketones are a versatile class of com-
pounds that are used as synthetically important inter-
mediates in organic synthesis.[32] Over the past two de-
cades, numerous methods have been developed to
Among the investigated iron precursors, here also
access a-acetoxy ketones from easily accessible start- Fe(OAc)2 was found to be the catalyst of choice for
ing materials such as ketones, alkenes and alkynes.[33] this transformation that gave (4a) in 63% yield at
However, most of these existing methods suffer from room temperature after 12 h (Table 5, entry 1). The
one or more drawbacks such as low chemoselectivi- reaction without catalyst resulted only in a trace
ty,[34] high reaction temperature,[35] need of excess of amount of desired 4a (Table 5, entry 9). Solvent
oxidant,[35b] low yield[34] and limited applicability to screening showed that the reaction in toluene, DCE,
aliphatic terminal alkynes.[36] Thus new improved MeOH, THF and H2O resulted in 4a with 62%, 74%,
47%, 26% and 38% yields, respectively (Table 5, en-
tries 10–14) under refluxing conditions. An optimum
yield of 81% of 4a was achieved by employing
CH3CN as solvent at 808C (Table 5, entry 16). In-
crease in reaction temperature beyond 808C incurred
a negative effect in the reaction efficiency (62% of 4a
at 1008C, Table 5, entry 17).
Scheme 2. Synthesis of 2-oxo-2-phenylethyl acetate (4a) (a-
acetoxy ketones).
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Iron-Catalyzed Dioxygenation of Alkenes and Terminal Alkynes
Table 6. Iron-catalyzed 1,2-oxyacetoxylation of alkynes.[a]
action of 1,3-diethynylbenzene with 1.2 equivalents of
PhI(OAc)2 resulted in dioxygenation of one of the
two triple bonds while the other remains intact (4j,
70% yield, Table 6, entry 10). However, on reaction
with 2.4 equivalents of PhI(OAc)2 both the triple
bonds were dioxygenated affording 65% of the de-
sired product 4k (Table 6, entry 11). Notably, the reac-
tion of aliphatic terminal alkynes also afforded the
corresponding a-acetoxy ketones (4n–p) in excellent
yields (Table 6, entries 14–16).
Entry Alkyne
3
4
Yield
[%][b]
1
2
3
4
5
6
7
8
phenylacetylene
4-ethynyltoluene
4-ethynylanisole
3a 4a 81
3b 4b 92
3c 4c 93
3d 4d 71
3e 4e 85
3f 4f 73
3g 4g 88
3h 4h 76
3i 4i 77
3j 4j 70
3j 4k 65[c]
3k 4l 76
3l 4m 88
3m 4n 86
3n 4o 84
3o 4p 68
Based on the reports on oxymetallation[37] and
metal-catalyzed 1,2-oxyacetoxylation of alkynes[33,38]
a plausible mechanism is proposed (Scheme 3).
2-ethynyl-1,4-dimethylbenzene
1-ethynyl-3,5-dimethoxybenzene
1-ethynyl-4-fluorobenzene
2-(trifluoromethyl)phenylacetylene
1-bromo-4-ethynylbenzene
1-ethynyl-4-pentylbenzene
1,3-diethynylbenzene
1,3-diethynylbenzene
1-ethynyl-2-nitrobenzene
3-ethynylthiophene
9
10
11
12
13
14
15
16
17
18
1-hexyne
1-heptyne
cyclopropylacetylene
4-(trifluoromethoxy)phenylacetylene 3p 4q 85
1-ethynyl-3,5-bis(trifluoromethyl)-
3q 4r 79
benzene
[a]
Reaction conditions: alkyne (1 mmol), PhI(OAc)2
(1.2 mmol), and Fe(OAc)2 (10 mol%) in CH3CN (3 mL)
at 808C for 12 h.
Isolated yield.
With 2.4 mmol of PhI(OAc)2.
[b]
[c]
Scheme 3. A plausible mechanism for iron-catalyzed 1,2-
oxyacetoxylation of alkynes.
With optimized conditions in hand (Table 5,
The reaction proceeds via iron(III)-catalyzed acti-
entry 16), the scope of this transformation on various vation of the triple bond of the terminal alkynes. This
structurally diverse aliphatic and aromatic terminal al- interaction makes the triple bond of the alkyne more
kynes was examined (Table 6).
electron-deficient in nature than that of the corre-
As can be seen from Table 6, various structurally sponding alkyne, resulting in the promotion of an in-
diverse aliphatic and aromatic terminal alkynes are termolecular Michel-type addition of acetate anion
efficiently transformed to the corresponding a-ace- [trace amounts of acetate anion are available in com-
toxy ketones (4a–4p) in moderate to excellent yields. mercial PhI(OAc)2] to the triple bond of an alkyne.
Arylacetylenes with electron-donating (Me, OMe) This addition follows an anti-addition rule[39] and the
and electron-withdrawing (NO2, F, Br, CF3) groups, reaction results in the formation of a b-acetoxyvinyl
were converted into the corresponding a-acetoxy ke- iron(II) intermediate (IV). Further, the reaction of IV
tones in excellent yields (Table 6, entries 2–8, 12, 17 with PhI(OAc)2 affords the (b-acetoxyvinyl)iodonium
and 18). However, as can be seen the reaction favours (V)[40] with 1 equivalent of acetate anion. This step
those arylacetylenes having electron-donating sub- also regenerates the Fe(OAc)3 catalyst. Subsequently,
stituents on the aryl ring (Table 6, entries 2–5). Steric the elimination of acetate anion from intermediate V
hindrance at the 2-position of an aryl ring shows a sig- generates iodonium ylide (VI). Further, the addition
nificant effect on the reaction yield. For example, re- of acetate ion on ylides (VI) gives the alkyliodonium
action of a ortho-substituted alkyne such as 2-ethynyl- salts (VII) and Ac2O. Finally, substitution of acetic
1,4-dimethylbenzene afforded the corresponding 2- acid in the place of phenyliodonium group in the salt
(2,5-dimethylphenyl)-2-oxoethyl acetate (4d) with (VII) affords the desired a-acetoxy ketone.[39a,40a,41]
71% yield only (Table 6, entry 4). On the other hand,
Since the present manuscript describes the syn-di-
internal alkynes completely failed to afford any oxi- acetoxylation of alkenes and 1,2-oxyacetoxylation of
dized product under these reaction conditions. The re- terminal alkynes, it provides an opportunity to dem-
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Experimental Section
General Information
All chemicals were purchased from commercial vendors and
used as is, unless otherwise specified. All the glassware was
dried before use. Ethyl acetate, hexane, and acetone were
distilled before use. The IR spectra of all compounds were
recorded on a Perkin–Elmer, Spectrum GX FT-IR spec-
trometer. The IR values are reported in wavenumbers
(cmÀ1). ESI mass spectra were recorded on a Finnigan LCQ
Advantagemax spectrometer. High-resolution mass spectra
(HR-MS) were recorded on QSTAR XL Hybrid MS/MS
mass spectrometer using ESI-QTOF mass spectrometry.
1H NMR and 13C NMR spectra were recorded on
a 300 MHz and a 75 MHz spectrometer, respectively. Chem-
ical shifts are reported relative to chloroform (d=7.26), or
Figure 1. Multigram-scale diacetoxylation of indene and 1,2-
oxyacetoxylation of phenylacetylene.
1
DMSO (d=2.50) for H NMR and chloroform (d=77.2), or
DMSO (d=39.5) for 13C NMR, respectively.
General Procedure for the Diacetoxylation of Olefins
onstrate the synthetic practicality of this new proce-
dure. For this, compounds 2k and 4a were synthesized
in a 10-grams scale (Figure 1).
To a solution of alkene (1.0 mmol), PhI(OAc)2 (386 mg,
1.2 mmol) and H2O (54 mL, 3.0 mmol) in AcOH (3.0 mL)
was added Fe(OAc)2 (17.4 mg, 0.1 mmol). The reaction mix-
ture was stirred at 808C for 18 h. After being cooled down
to room temperature, 0.5 mL of acetic anhydride was added
and the reaction mixture was again stirred at room tempera-
ture for 12 h. After the solvent had been removed under
vacuum, the residue was purified by column chromatogra-
phy using hexane and ethyl acetate as the eluents to afford
the desired product.
As illustrated in Table 3, the catalytic system,
[1.2 equiuv. of PhI(OAc)2, 3 equiv. of H2O, 0.1 equiv.
of Fe(OAc)2, AcOH at 808C for 18 h, then treatment
with Ac2O] proved to be highly efficient to afford the
desired diacetate product 2k in 81% yield with excel-
lent diastereoselectivity of 13:1 (syn/anti). The isolat-
ed yield and diastereomeric ratio value of 2k were in
full agreement with the results of the small-scale reac-
tion. On the other hand, 1,2-oxyacetoxylation of phe-
nylacetylene in a 10-g scale was also performed to fur-
nish the desired product 4a efficiently, further demon-
strating the efficiency of this methodology.
General Procedure for the Preparation of a-Acetoxy
Ketones from Terminal Alkynes
To a solution of terminal alkyne (1.0 mmol) and PhI(OAc)2
(386 mg, 1.2 mmol) in CH3CN (3.0 mL) was added
Fe(OAc)2 (17.4 mg, 0.1 mmol). The reaction mixture was
stirred at 808C for 12 h. The reaction mixture was concen-
trated under vacuum. The residue was purified by column
chromatography using hexane and ethyl acetate as the elu-
ents to afford the desired product.
Conclusions
In conclusion, we have developed a facile and effi-
cient Fe(OAc)2-PhI(OAc)2 catalytic system for the di-
oxygenation of unsaturated bonds (alkenes and termi-
nal alkynes). The use of this catalytic system on a vari-
ety of alkenes in acetic acid afforded the correspond-
ing vicinal diacetate products in good to excellent
yields. Moreover, the reaction with internal alkenes is
found to be highly diastereoselective and results in
1-Phenylethane-1,2-diyl diacetate (2a):[21] Colorless liquid;
yield: 77% (171 mg); FT-IR (neat): n=701, 761, 1046, 1222,
1372, 1455, 1746, 2927 cmÀ1 1H NMR (300 MHz, CDCl3):
;
d=2.05 (s, 3H), 2.12 (s, 3H), 4.29 (dd, 1H, J=7.9, 11.9 Hz),
4.34 (dd, 1H, J=3.9, 12.0 Hz), 6.02 (dd, 1H, J=3.9, 7.9 Hz),
7.31–7.38 (m, 5H); 13C NMR (75 MHz, CDCl3): d=20.7,
21.0, 66.0, 73.2, 126.6, 128.5, 128.5, 136.4, 170.0, 170.5; ESI-
MS: m/z=245 (M+Na)+; ESI-HR-MS: m/z=245.07865
the corresponding vicinal diacetate products with (M+Na)+, calcd. for C12H14O4Na: 245.07871.
1-(p-Tolyl)ethane-1,2-diyl diacetate (2b):[42] Yellow liquid;
yield: 90% (212 mg); FT-IR (neat): n=815, 1046, 1224,
1370, 1436, 1744, 2926 cmÀ1 1H NMR (300 MHz, CDCl3):
a high syn to anti ratio (up to 99%). On the other
hand, a wide variety of a-acetoxy ketones was pre-
pared in moderate to excellent yields on treatment of
terminal alkynes with this catalytic system in acetoni-
trile. Furthermore, in case of the cis-diacetoxylation
of alkenes, the involvement of an Fe(II)-Fe(III) cata-
lytic cycle was established by means of UV-VIS spec-
troscopy.
;
d=2.05 (s, 3H), 2.10 (s, 3H), 2.34 (s, 3H), 4.26–4.33 (m,
2H), 5.98 (dd, 1H, J=4.2, 7.4 Hz), 7.17 (d, 2H, J=7.9 Hz),
7.26 (d, 2H, J=7.9 Hz); 13C NMR (75 MHz, CDCl3): d=
20.7, 21.0, 21.1, 66.0, 73.2, 126.6, 129.2, 133.4, 138.4, 170.0,
170.6; ESI-MS: m/z=259 (M+Na)+; ESI-HR-MS: m/z=
259.09358 (M+Na)+, calcd. for C13H16O4Na: 259.09408.
1-(3-Methoxyphenyl)ethane-1,2-diyl
diacetate
(2c):
Yellow liquid; yield: 93% (234 mg); FT-IR (neat): n=701,
3592
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FULL PAPERS
Iron-Catalyzed Dioxygenation of Alkenes and Terminal Alkynes
1
787, 1044, 1240, 1371, 1744, 2956 cmÀ1; H NMR (300 MHz,
CDCl3): d=2.06 (s, 3H), 2.12 (s, 3H), 3.81 (s, 3H), 4.27 (dd,
1H, J=8.0, 11.9 Hz), 4.33 (dd, 1H, J=3.8, 12.0 Hz), 5.98
(dd, 1H, J=3.6, 8.0 Hz), 6.84–6.92 (m, 2H), 6.95 (d, 1H, J=
7.6 Hz), 7.29 (d, 1H, J=7.9 Hz); 13C NMR (75 MHz,
CDCl3): d=20.7, 21.0, 55.2, 66.1, 73.2, 112.4, 113.8, 118.8,
129.7, 138.0, 159.7, 170.0, 170.6; ESI-MS: m/z=275 (M+
Na)+; ESI-HR-MS: m/z=275.08858 (M+Na)+, calcd. for
C13H16O5Na: 275.08899.
3H, J=6.9 Hz), 1.25–1.32 (m, 8H), 1.54–1.60 (m, 2H), 2.063
(s, 3H), 2.068 (s, 3H), 4.03 (dd, 1H, J=6.7, 11.9 Hz), 4.22
(dd, 1H, J=3.2, 11.9 Hz), 5.04–5.10 (m, 1H); 13C NMR
(75 MHz, CDCl3): d=14.0, 20.7, 21.0, 22.5, 25.0, 29.0, 30.7,
31.6, 65.1, 71.6, 170.6, 170.8; ESI-MS: m/z=253 (M+Na)+;
ESI-HR-MS: m/z=253.14177 (M+Na)+, calcd. for
C12H22NaO4: 253.14158.
E/Z-1,2-Diphenylethane-1,2-diyl diacetate (2j):[25] Mixture
of diastereomers (syn/anti=7:1); white solid; yield: 81%
(241 mg); FT-IR (KBr): n=702, 933, 1037, 1226, 1375, 1454,
1-(4-Chlorophenyl)ethane-1,2-diyl
diacetate
(2d):[43]
Yellow liquid; yield: 72% (184 mg); FT-IR (neat): n=826,
1737, 2854, 2926, 3033 cmÀ1 1H NMR (300 MHz, CDCl3;
;
1014, 1048, 1223, 1370, 1493, 1744, 2852, 2925 cmÀ1
;
normalized values, integral values 2H=1H): d=2.01 (s,
3.1H=1.55H), 2.08 (s, 21.1H=10.55H), 6.05 (s, 7H=
3.5H), 6.08 (s, 1H=0.5H), 7.13–7.16 (m, 14.1H=7.05H),
7.19–7.23 (m, 22.9H=11.45H), 7.27–7.29 (m, 3.1H=
1.55H); 13C NMR (75 MHz, CDCl3): d=20.9, 21.0, 76.4,
77.0, 127.47, 127.52, 128.0, 128.1, 128.3, 136.0, 136.1, 169.5,
169.7 (one signal is overlapping); ESI-MS: m/z=321 (M+
Na)+; ESI-HR-MS: m/z=321.11091 (M+Na)+, calcd. for
C18H18NaO4: 321.11028.
1H NMR (300 MHz, CDCl3): d=2.05 (s, 3H), 2.11 (s, 3H),
4.21–4.37 (m, 2H), 5.97 (dd, 1H, J=4.3, 7.3 Hz), 7.27–7.39
(m, 4H); 13C NMR (75 MHz, CDCl3): d=20.7, 21.0, 65.7,
72.6, 128.1, 128.8, 134.4, 135.0, 169.9, 170.5; ESI-MS: m/z=
279 (M+Na)+; ESI-HR-MS: m/z=279.04019 (M+Na)+,
calcd. for C12H13ClNaO4: 279.04001.
1-(4-Bromophenyl)ethane-1,2-diyl
Yellow liquid; yield: 85% (256 mg); FT-IR (neat): n=822,
1011, 1050, 1222, 1371, 1490, 1746, 2854, 2926 cmÀ1
diacetate
(2e):[44]
;
E/Z-2,3-Dihydro-1H-indene-1,2-diyl diacetate (2k):[25]
Mixture of diastereomers (syn/anti=14.3:1); colourless
liquid; yield: 88% (206 mg); FT-IR (neat): n=756, 963,
1022, 1064, 1247, 1373, 1434, 1462, 1742, 2854, 2925,
1H NMR (300 MHz, CDCl3): d=2.05 (s, 3H), 2.11 (s, 3H),
4.26 (dd, 1H, J=7.7, 11.9 Hz), 4.31 (dd, 1H, J=3.9,
11.9 Hz), 5.95 (dd, 1H, J=3.9, 7.7 Hz), 7.24 (d, 2H, J=
8.3 Hz), 7.50 (d, 2H, J=8.3 Hz); 13C NMR (75 MHz,
CDCl3): d=20.7, 21.0, 65.6, 72.6, 122.6, 128.4, 131.8, 135.5,
169.9, 170.5; ESI-MS: m/z=323 (M+Na)+; ESI-HR-MS:
m/z=322.98900 (M+Na)+, calcd. for C12H13BrNaO4:
322.98949.
3030 cmÀ1 1H NMR (300 MHz, CDCl3; normalized values,
;
integral values 10H=1H) d=2.07 (s, 29.8H=2.98H), 2.09
(s, 31.5H=3.15H), 3.13 (dd, 11.4H=1.14H, J=5.7,
16.0 Hz), 3.24 (dd, 11.5H=1.15H, J=6.7, 16.0 Hz), 5.52–
5.57 (m, 10.5H=1.05H), 6.22 (d, 10H=1H, J=5.3 Hz),
7.26–7.41 (m, 42.7H=4.27H); 13C NMR (75 MHz, CDCl3):
d=20.80, 20.84, 35.8, 73.2, 75.0, 124.9, 125.7, 127.3, 129.5,
138.0, 140.1, 170.42, 170.44; ESI-MS: m/z=257 (M+Na)+;
ESI-HR-MS: m/z=257.07809 (M+Na)+, calcd. for
C13H14NaO4: 257.07898.
1-(Naphthalen-2-yl)ethane-1,2-diyl
Yellow liquid; yield: 85% (231 mg); FT-IR (neat): n=750,
820, 1047, 1222, 1369, 1743, 2852, 2927 cmÀ1 1H NMR
diacetate
(2f):[25]
;
(300 MHz, CDCl3): d=2.06 (s, 3H), 2.15 (s, 3H), 4.37–4.44
(m, 2H), 6.18 (dd, 1H, J=4.4, 7.6 Hz), 7.46–7.51 (m, 3H),
7.82–7.87 (m, 4H); 13C NMR (75 MHz, CDCl3): d=20.7,
21.1, 66.0, 73.4, 124.1, 126.1, 126.4, 127.7, 128.0, 128.5, 133.0,
133.2, 133.8, 170.1, 170.6; ESI-MS: m/z=295 (M+Na)+;
ESI-HR-MS: m/z=295.09343 (M+Na)+, calcd. for
C16H16O4Na: 295.09408.
E/Z-1,2,3,4-Tetrahydronaphthalene-1,2-diyl
diacetate
(2l):[25] Mixture of diastereomers (syn/anti=1.5:1); colour-
less liquid; yield: 79% (196 mg); FT-IR (neat): n=748, 967,
1
1042, 1245, 1369, 1740, 2932, 3025 cmÀ1; H NMR (300 MHz,
CDCl3): d=1.92–2.02 (m, 2H), 2.04 (s, 3H), 2.05 (s, 3H),
2.09 (s, 3H), 2.11(s, 3H), 2.14–2.22 (m, 2H), 2.87–3.07 (m,
4H), 5.15–5.29 (m, 2H), 6.07 (d, 1H, J=5.8 Hz), 6.18 (d,
1H, J=3.2 Hz), 7.13–7.30 (m, 8H); 13C NMR (75 MHz,
CDCl3): d=21.05, 21.05, 23.3, 24.9, 25.6, 27.0, 69.2, 70.0,
71.0, 71.4, 126.38, 126.42, 128.2, 128.5, 128.6, 128.7, 129.0,
129.9, 132.6, 136.3, 136.5, 170.2, 170.3, 170.5 (some signals
are overlapping); ESI-MS: m/z=271 (M+Na)+; ESI-HR-
MS: m/z=271.09469 (M+Na)+, calcd. for C14H16NaO4:
271.09463.
2-Phenylpropane-1,2-diyl diacetate (2g):[21] Yellow liquid;
yield: 72% (170 mg); FT-IR (neat): n=700, 765, 1046, 1130,
1
1235, 1370, 1448, 1743, 2854, 2927 cmÀ1; H NMR (300 MHz,
CDCl3): d=1.89 (s, 3H), 2.05 (s, 3H), 2.08 (s, 3H), 4.30 (d,
1H, J=11.5 Hz), 4.39 (d, 1H, J=11.5 Hz), 7.26–7.38 (m,
5H); 13C NMR (75 MHz, CDCl3): d=20.7, 21.8, 22.0, 69.8,
81.5, 124.8, 127.6, 128.3, 141.1, 169.3, 170.4; ESI-MS: m/z=
259 (M+Na)+; ESI-HR-MS: m/z=259.09367 (M+Na)+,
calcd. for C13H16O4Na: 259.09408.
1-(4-Acetoxyphenyl)ethane-1,2-diyl diacetate (2h): Yellow
liquid; yield: 65% (182 mg); FT-IR (neat): n=850, 911,
cis-Acetic acid 2-hydroxy-2-phenylcyclohexyl ester
(2m):[44] (syn/anti= >99:1); white solid; yield: 92%
(215 mg); FT-IR (KBr): n=699, 757, 994, 1034, 1079, 1253,
1015, 1047, 1169, 1221, 1371, 1509, 1745, 2956 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=2.06 (s, 3H), 2.11 (s, 3H),
2.30 (s, 3H), 4.27 (dd, 1H, J1 =8.0, J2 =11.9 Hz), 4.33 (dd,
1H, J1 =3.8, J2 =11.9 Hz), 6.02 (dd, 1H, J=3.8, 8.0 Hz), 7.10
(d, 2H, J=8.5 Hz), 7.39 (d, 2H, J=8.5 Hz); 13C NMR
(75 MHz, CDCl3): d=20.7, 21.0, 21.1, 65.9, 72.6, 121.8,
127.9, 134.0, 150.7, 169.3, 169.9, 170.6; ESI-MS: m/z=303
(M+Na)+; ESI-HR-MS: m/z=303.08323 (M+Na)+, calcd.
for C14H16O6Na: 303.08391.
1376, 1718, 2857, 2940, 3026, 3532 cmÀ1; H NMR (300 MHz,
1
CDCl3): d=1.45–1.58 (m, 2H), 1.65–1.78 (m, 2H), 1.80 (s,
3H), 1.83–1.93 (m, 4H), 2.27 (br s, 1H), 5.29 (dd, 1H, J=
5.0, 10.6 Hz), 7.21–7.26 (m, 1H), 7.30–7.35 (m, 2H), 7.43–
7.47 (m, 2H); 13C NMR (75 MHz, CDCl3): d=20.8, 21.0,
24.1, 27.1, 39.7, 75.2, 76.2, 124.6, 126.9, 128.2, 145.9, 169.7;
ESI-MS: m/z=257 (M+Na)+; ESI-HR-MS: m/z=
257.11598 (M+Na)+, calcd. for C14H18NaO3: 257.11536.
2-Oxo-2-phenylethyl acetate (4a):[45] yellow liquid; yield:
81% (144 mg); FT-IR (KBr): n=562, 632, 686, 754, 968,
1080, 1227, 1373, 1426, 1600, 1699, 1742, 2939, 3066,
Octane-1,2-diyl diacetate (2i):[21] Colourless liquid; yield:
88% (202 mg); FT-IR (neat): n=1046, 1226, 1371, 1744,
2858, 2929 cmÀ1 1H NMR (300 MHz, CDCl3): d=0.88 (t,
;
Adv. Synth. Catal. 2015, 357, 3587 – 3596
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B. T. V. Srinivas et al.
3464 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=2.23 (s, 3H),
2-(4-Bromophenyl)-2-oxoethyl acetate (4h):[45] White
solid; yield: 76% (195 mg); FT-IR (KBr): n=561, 814, 970,
1069, 1226, 1248, 1375, 1430, 1586, 1694, 1745, 2950,
5.34 (s, 2H), 7.46–7.52 (m, 2H), 7.59–7.63 (m, 1H), 7.90–
7.93 (m, 2H); 13C NMR (75 MHz, CDCl3): d=20.5, 65.9,
127.6, 128.7, 133.8, 134.1, 170.3, 192.1; ESI-MS: m/z=201
(M+Na)+; ESI-HR-MS: m/z=179.07016 (M+H)+, calcd.
for C10H11O3: 179.07019.
3377 cmÀ1 1H NMR (300 MHz, CDCl3): d=2.23 (s, 3H),
;
5.29 (s, 2H), 7.62–7.66 (m, 2H), 7.76–7.80 (m, 2H);
13C NMR (75 MHz, CDCl3): d=20.5, 65.8, 129.1, 129.2,
132.2, 132.9, 170.3, 191.3; ESI-MS: m/z=279 (M+Na)+;
ESI-HR-MS: m/z=278.96311 (M+Na)+, calcd. for
C10H9O3BrNa: 278.96309.
2-Oxo-2-(p-tolyl)ethyl acetate (4b):[35b] White solid; yield:
92% (177 mg); FT-IR (KBr): n=557, 810, 964, 1081, 1227,
1372, 1423, 1604, 1694, 1745, 2952, 3430 cmÀ1 1H NMR
;
2-Oxo-2-(4-pentylphenyl)ethyl acetate (4i): Colourless
liquid; yield: 77% (191 mg); FT-IR (neat): n=567, 821, 970,
(300 MHz, CDCl3): d=2.23 (s, 3H), 2.42 (s, 3H), 5.32 (s,
2H), 7.28 (d, 2H, J=8.5 Hz), 7.82 (d, 2H, J=8.5 Hz);
13C NMR (75 MHz, CDCl3): d=20.5, 21.7, 65.9, 127.8, 129.4,
131.6, 144.8, 170.4, 191.6; ESI-MS: m/z=215 (M+Na)+;
ESI-HR-MS: m/z=215.06847 (M+Na)+, calcd. for
C11H12O3Na: 215.06848.
1222, 1373, 1420, 1607, 1701, 1752, 2862, 2931 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=0.87–0.91 (m, 3H), 1.29–
1.37 (m, 4H), 1.59–1.64 (m, 2H), 2.23 (s, 3H), 2.66 (t, 2H,
J=7.7 Hz), 5.32 (s, 2H), 7.29 (d, 2H, J=8.3 Hz), 7.83 (d,
2H, J=8.3 Hz); 13C NMR (75 MHz, CDCl3): d=13.9, 20.5,
22.4, 30.6, 31.3, 35.9, 65.9, 127.8, 128.8, 131.8, 149.7, 170.3,
191.6; ESI-MS: m/z=271 (M+Na)+; ESI-HR-MS: m/z=
271.13108 (M+Na)+, calcd. for C15H20O3Na: 271.13113.
2-(3-Ethynylphenyl)-2-oxoethyl acetate (4j): Yellow
liquid; yield: 70% (141 mg); FT-IR (neat): n=674, 779,
2-(4-Methoxyphenyl)-2-oxoethyl acetate (4c):[38] White
solid; yield: 93% (193 mg); FT-IR (KBr): n=605, 833, 970,
1025, 1176, 1227, 1425, 1603, 1692, 1745, 2929 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=2.22 (s, 3H), 3.87 (s, 3H),
5.30 (s, 2H), 6.95 (d, 2H, J=8.9 Hz), 7.90 (d, 2H, J=
8.9 Hz); 13C NMR (75 MHz, CDCl3): d=20.5, 55.5, 65.7,
114.0, 127.1, 130.0, 164.0, 170.4, 190.5; ESI-MS: m/z=231
(M+Na)+; ESI-HR-MS: m/z=231.06341 (M+Na)+, calcd.
for C11H12O4Na: 231.06346.
1083, 1226, 1373, 1705, 1746, 2927, 3276, 3742 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=2.23 (s, 3H), 3.16 (s, 1H),
5.31 (s, 2H), 7.42–7.51 (m, 1H), 7.71 (d, 1H, J=7.7 Hz),
7.89 (d, 1H, J=7.9 Hz), 8.00–8.03 (m, 1H); 13C NMR
(75 MHz, CDCl3): d=20.4, 65.9, 78.7, 82.1, 123.0, 127.8,
128.9, 131.3, 134.2, 140.0, 170.3, 191.4; ESI-MS: m/z=225
(M+Na)+; ESI-HR-MS: m/z=203.07027 (M+H)+, calcd.
for C12H11O3: 203.07032.
2-(2,5-Dimethylphenyl)-2-oxoethyl acetate (4d):[46] Yellow
liquid; yield: 71% (146 mg); FT-IR (neat): n=770, 1218,
1375, 1728, 2853, 2924 cmÀ1 1H NMR (300 MHz, CDCl3):
;
d=2.21 (s, 3H), 2.36 (s, 3H), 2.46 (s, 3H), 5.17 (s, 2H),
7.14–7.25 (m, 2H), 7.40 (s, 1H); 13C NMR (75 MHz,
CDCl3): d=20.5, 20.6, 20.8, 67.2, 128.5, 132.1, 132.9, 134.2,
135.3, 135.8, 170.4, 195.8; ESI-MS: m/z=229 (M+Na)+;
ESI-HR-MS: m/z=207.10208 (M+H)+, calcd. for C12H15O3:
207.10218.
1,3-Phenylenebis(2-oxoethane-2,1-diyl) diacetate (4k):
Yellow solid; yield: 65% (181 mg); FT-IR (KBr): n=682,
794, 1027, 1079, 1189, 1240, 1377, 1424, 1699, 1750, 2925,
3197, 3380 cmÀ1 1H NMR (300 MHz, CDCl3): d=2.24 (s,
;
6H), 5.36 (s, 4H), 7.65 (t, 1H, J=7.7 Hz), 8.15 (dd, 2H, J=
1.5, 7.7 Hz), 8.42–8.45 (m, 1H); 13C NMR (75 MHz, CDCl3):
d=20.5, 66.0, 126.9, 129.6, 132.6, 134.7, 170.3, 191.4; ESI-
MS: m/z=279 (M+H)+; ESI-HR-MS: m/z=279.08652
(M+H)+, calcd. for C14H15O6: 279.08679.
2-(3,5-Dimethoxyphenyl)-2-oxoethyl acetate (4e): Yellow
liquid; yield: 85% (202 mg); FT-IR (KBr): n=847, 1063,
1159, 1235, 1305, 1373, 1427, 1598, 1700, 1750, 2844, 2938,
3088, 3389 cmÀ1 1H NMR (300 MHz, CDCl3): d=2.28 (s,
;
3H), 3.82 (s, 6H), 5.28 (s, 2H), 6.68 (t, 1H, J=2.0 Hz), 7.03
(d, 2H, J=2.0 Hz); 13C NMR (75 MHz, CDCl3): d=20.4,
55.5, 66.0, 105.4, 105.9, 135.8, 160.9, 170.3, 191.7; ESI-MS:
m/z=261 (M+Na)+; ESI-HR-MS: m/z= 239.09122 (M+
H)+, calcd. for C12H15O5: 239.09128.
2-(2-Nitrophenyl)-2-oxoethyl acetate (4l):[47] Dark yellow
liquid; yield: 76% (169 mg); FT-IR (neat): n=703, 1074,
1214, 1348, 1531, 1728, 1748, 2853, 2924 cmÀ1 1H NMR
;
(300 MHz, CDCl3): d=2.02 (s, 3H), 4.99 (s, 2H), 7.51 (dd,
1H, J1 =1.3, J2 =7.4 Hz), 7.65–7.69 (m, 1H), 7.76–7.80 (m,
1H), 8.17 (dd, 1H, J=1.0, 8.2 Hz); 13C NMR (75 MHz,
CDCl3): d=20.1, 67.5, 123.9, 128.7, 131.3, 134.3, 134.6, 146.2,
170.0, 197.0; ESI-MS: m/z=246 (M+Na)+; ESI-HR-MS: m/
z=246.03709 (M+Na)+, calcd. for C10H9O5NNa: 246.03719.
2-Oxo-2-(thiophen-3-yl)ethyl acetate (4m): Yellow solid;
yield: 88% (162 mg); FT-IR (KBr): n=629, 795, 1004, 1184,
2-(4-Fluorophenyl)-2-oxoethyl acetate (4f):[38] Brown
solid; yield: 73% (143 mg); FT-IR (KBr): n=559, 789, 833,
973, 1085, 1158, 1221, 1372, 1421, 1599, 1703, 1749, 2950,
3384 cmÀ1 1H NMR (300 MHz, CDCl3): d=2.23 (s, 3H),
;
5.30 (s, 2H), 7.14–7.19 (m, 2H), 7.93–7.98 (m, 2H);
13C NMR (75 MHz, CDCl3): d=20.4, 65.7, 116.0 (d, J=
22.1 Hz), 130.4 (d, J=9.0 Hz), 165.0, 167.0, 170.3, 190.6;
ESI-MS: m/z=219 (M+Na)+; ESI-HR-MS: m/z=
197.06140 (M+H)+, calcd. for C10H10FO3: 197.06140.
1
1227, 1429, 1690, 1744, 2932, 3106 cmÀ1; H NMR (300 MHz,
CDCl3): d=2.22 (s, 3H), 5.20 (s, 2H), 7.35–7.40 (m, 1H),
7.55 (dd, 1H, J=1.1, 5.0 Hz), 8.10–8.13 (m, 1H); 13C NMR
(75 MHz, CDCl3): d=20.4, 66.1, 126.4, 126.7, 132.1, 138.6,
170.3, 186.6; ESI-MS: m/z=207 (M+Na)+; ESI-HR-MS:
m/z=185.02716 (M+H)+, calcd. for C8H9O3S: 185.02724.
2-Oxohexyl acetate (4n):[35b] Yellow liquid; yield: 86%
(136 mg); FT-IR (neat): n=759, 1029, 1233, 1375, 1459,
2-Oxo-2-[2-(trifluoromethyl)phenyl]ethyl acetate (4g):[35b]
Yellow liquid; yield: 88% (216 mg); FT-IR (neat): n=770,
1132, 1216, 1315, 1728, 2930, 3462 cmÀ1; H NMR (300 MHz,
1
CDCl3): d=2.16 (s, 3H), 5.04 (s, 2H), 7.56 (d, 1H, J=
7.2 Hz), 7.60–7.67 (m, 2H), 7.74 (d, 1H, J=7.2 Hz);
13C NMR (75 MHz, CDCl3): d=20.3, 67.6, 121.4, 125.1,
126.60, 126.66, 126.7, 126.8, 127.3, 127.6, 127.7, 130.8, 131.9,
136.3, 170.1, 197.1; ESI-MS: m/z=269 [M+Na]+; ESI-HR-
MS: m/z=269.03944 (M+Na)+, calcd. for C11H9O3F3Na:
269.03954, found: .
1743, 2926, 2958, 3448 cmÀ1 1H NMR (300 MHz, CDCl3):
;
d=0.91 (t, 3H, J=7.3 Hz), 1.30–1.38 (m, 2H), 1.56–1.63 (m,
2H), 2.17 (s, 3H), 2.42 (t, 2H, J=7.4 Hz), 4.65 (s, 2H);
13C NMR (75 MHz, CDCl3): d=13.7, 20.4, 22.2, 25.3, 38.5,
67.9, 170.2, 203.9; ESI-MS: m/z=181 (M+Na)+; ESI-HR-
3594
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Iron-Catalyzed Dioxygenation of Alkenes and Terminal Alkynes
MS: m/z=181.08415 (M+Na)+, calcd. for C8H14NaO3:
181.08406.
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D. H. B. Ripin, Chem. Rev. 2006, 106, 2943–2989.
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Angew. Chem. Int. Ed. 1999, 38, 980–983.
2-Oxoheptyl acetate (4o):[36] Yellow liquid; yield: 84%
(144 mg); FT-IR (neat): n=747, 1072, 1272, 1459, 1731,
2925, 2957 cmÀ1 1H NMR (300 MHz, CDCl3): d=0.89 (t,
;
3H, J=6.7 Hz), 1.26–1.37 (m, 4H), 1.58–1.70 (m, 2H), 2.17
(s, 3H), 2.41 (t, 2H, J=7.3 Hz), 4.65 (s, 2H); 13C NMR
(75 MHz, CDCl3): d=13.8, 20.4, 22.3, 22.9, 31.1, 38.7, 67.8,
170.2, 203.9; ESI-MS: m/z=195 (M+Na)+; ESI-HR-MS:
m/z=195.09959 (M+Na)+, calcd. for C9H16NaO3:
195.09971.
2-Cyclopropyl-2-oxoethyl acetate (4p):[38] Colourless
liquid; yield: 68% (97 mg); FT-IR (neat): n=1249, 1459,
1610, 1731, 2852, 2923, 3444 cmÀ1
;
1H NMR (300 MHz,
CDCl3): d=0.93–1.03 (m, 2H), 1.09–1.17 (m, 2H), 1.89–2.00
(m, 1H), 2.17 (s, 3H), 4.83 (s, 2H); 13C NMR (75 MHz,
CDCl3): d=11.3, 17.2, 20.5, 68.3, 170.2, 203.6; ESI-MS:
m/z=165 (M+Na)+; ESI-HR-MS: m/z=165.05289 (M+
Na)+, calcd. for C7H10NaO3: 165.05276.
2-Oxo-2-[4-(trifluoromethoxy)phenyl]ethyl
acetate
(4q):[48] Colourless solid; yield: 85% (222 mg); FT-IR (KBr):
n=1234, 1305, 1429, 1605, 1702, 2941, 2984, 3388, 3648,
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3674 cmÀ1 1H NMR (300 MHz, CDCl3): d=2.23 (s, 3H),
;
5.31 (s, 2H), 7.32 (d, 2H, J=8.5 Hz), 7.98 (d, 2H, J=
8.5 Hz); 13C NMR (75 MHz, CDCl3): d=20.4, 65.8, 120.5,
129.8, 132.2, 134.0, 153.0, 179.4, 190.7; ESI-MS: m/z=285
(M+Na)+; ESI-HR-MS: m/z=285.03155 (M+Na)+, calcd.
for C11H9O4F3Na: 285.03181.
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2-[3,5-Bis(trifluoromethyl)phenyl]-2-oxoethyl acetate (4r):
Colourless solid; yield: 79% (248 mg); FT-IR (KBr): n=
1136, 1170, 1208, 1284, 1716, 1741, 2854, 2926, 2993 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=2.24 (s, 3H), 5.34 (s, 2H),
8.12 (br s, 1H), 8.34 (br s, 2H); 13C NMR (75 MHz, CDCl3):
d=20.3, 65.8, 119.4, 121.5, 123.7, 126.9, 127.8, 132.2, 132.5,
132.8, 133.1, 135.6, 170.2, 190.0; ESI-MS: m/z=337 (M+
Na)+; ESI-HR-MS: m/z=337.02711 (M+Na)+, calcd. for
C12H8F6NaO3: 337.02753.
[10] M. Klopstra, G. Roelfes, R. Hage, R. M. Kellogg, B. L.
Feringa, Eur. J. Inorg. Chem. 2004, 846–856.
Acknowledgements
BTV Srinivas thanks the Council of Scientific and Industrial
Research, New Delhi, India for the award of a Senior Re-
search Fellowship (SRF).
[11] P. C. A. Bruijnincx, I. L. C. Buurmans, S. Gosiewska,
M. A. H. Moelands, M. Lutz, A. L. Spek, G. van Koten,
R. J. M. K. Gebbink, Chem. Eur. J. 2008, 14, 1228–1237.
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[13] S. M. Barry, P. J. Rutledge, Synlett 2008, 2172–2174.
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Adv. Synth. Catal. 2015, 357, 3587 – 3596