Synthesis of 4-diarylamino-3-iodo-2(5 h)-furanones via the simultaneous α -iodination and N β-arylation by an efficient difunctionalizable transfer reagent PhI(OAc)2

Article abstract of DOI:10.1080/00397911.2013.879899

During the studies on the intramolecular cyclization of 4-arylamino-2(5H)-furanones via the Pd-catalyzed C-H activation, a kind of difunctionalization reaction caused by the designed oxidant PhI(OAc)₂ [(diacetoxyiodo)benzene, DIB] was accidentally discovered. When 1.5 eq. DIB is used as a difunctionalizable transfer reagent in the 40 h reaction at 60°C and CH₃CN as solvent, 4-diarylamino-3-iodo-2(5H)-furanones can be obtained with the yields of 57-91% (usually more than 73%). The simultaneous α-iodination and N ^β-arylation reaction without metal catalyst is efficient and convenient. This novel utilization with a greater atom economy provides a simple and practical conversion route for the synthesis of the potential biological 2(5H)-furanone compounds containing multifunctional groups.

Full text of DOI:10.1080/00397911.2013.879899

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Synthesis of 4-Diarylamino-3-iodo-2(5H)-
furanones via the Simultaneous α-
β
Iodination and N -Arylation by an
Efficient Difunctionalizable Transfer
Reagent PhI(OAc)2
Fuling Xue a , Pai Peng a , Jie Shi a , Mingli Zhong a & Zhaoyang Wang
a
a School of Chemistry and Environment, South China Normal
University, Key Laboratory of Theoretical Chemistry of Environment,
Ministry of Education , Guangzhou , China
Accepted author version posted online: 18 Mar 2014.Published
online: 29 May 2014.
To cite this article: Fuling Xue , Pai Peng , Jie Shi , Mingli Zhong & Zhaoyang Wang (2014) Synthesis
of 4-Diarylamino-3-iodo-2(5H)-furanones via the Simultaneous α-Iodination and N β -Arylation
by an Efficient Difunctionalizable Transfer Reagent PhI(OAc)2 , Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 44:13, 1944-1956,
DOI: 10.1080/00397911.2013.879899
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Synthetic Communications1, 44: 1944–1956, 2014
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.879899
SYNTHESIS OF 4-DIARYLAMINO-3-IODO-2(5H)-
FURANONES VIA THE SIMULTANEOUS
a-IODINATION AND Nb-ARYLATION BY AN
EFFICIENT DIFUNCTIONALIZABLE TRANSFER
REAGENT PhI(OAc)2
Fuling Xue, Pai Peng, Jie Shi, Mingli Zhong, and
Zhaoyang Wang
School of Chemistry and Environment, South China Normal University,
Key Laboratory of Theoretical Chemistry of Environment, Ministry of
Education, Guangzhou, China
GRAPHICAL ABSTRACT
Abstract During the studies on the intramolecular cyclization of 4-arylamino-2(5H)-
furanones via the Pd-catalyzed C-H activation, a kind of difunctionalization reaction
caused by the designed oxidant PhI(OAc)2 [(diacetoxyiodo)benzene, DIB] was acciden-
tally discovered. When 1.5 eq. DIB is used as a difunctionalizable transfer reagent in the
40 h reaction at 60ꢀC and CH3CN as solvent, 4-diarylamino-3-iodo-2(5H)-furanones
can be obtained with the yields of 57–91% (usually more than 73%). The simultaneous
a-iodination and Nb-arylation reaction without metal catalyst is efficient and convenient.
This novel utilization with a greater atom economy provides a simple and practical
conversion route for the synthesis of the potential biological 2(5H)-furanone compounds
containing multifunctional groups.
Keywords (Diacetoxyiodo)benzene; difunctionalization; iodination; 2(5H)-furanone;
N-arylation
Received November 26, 2013.
Address correspondence to Z. Wang, School of Chemistry and Environment, South China Normal
University, Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education,
Guangzhou, 510006, China. E-mail: wangwangzhaoyang@tom.com, wangzy@scnu.edu.cn
Color versions of one or more of the figures in the article can be found online at www.tandfonline.
com/lsyc.
1944

SYNTHESIS OF 4-DIARYLAMINO-3-IODO-2(5H)-FURANONES
1945
INTRODUCTION
As a kind of efficient synthetic strategy, difunctionalization reactions,[1–4]
especially the difunctionalization reactions simultaneously yielding two different
functional groups,[5–18] have aroused great interest from organic chemists in recent
years. Among them, the difunctionalization reactions with greater atom economies
from the point of green chemistry are undoubtedly more promising.[2–9,17,18] Usually,
the utilization of transfer reagents, especially some hypervalent organic iodine
reagents, is a simple way for the efficient difunctionalization.[2–8,15–18] It is a pity that
in some cases, there is only a functional group converted from these hypervalent
iodine transfer reagents.[15,16,19–22] Therefore, it is still a challenge for organic
chemists to find a suitable hypervalent organic iodine transfer reagent for the difunc-
tionalization simultaneously yielding two different functional groups in the synthesis
of potential biological heterocyclic compounds.[8,17,18]
Of course, many hypervalent organic iodine reagents are common oxidants in
organic synthesis.[1,23–29] For example, PhI(OAc)2 [(diacetoxyiodo)benzene, DIB] is
an easily accessible hypervalent organic iodine reagent can be used to construct indole
ring derivatives via the oxidation.[30,31] Because of the significance of indole ring deri-
vatives in natural products,[32–34] pharmaceuticals,[34–36] and materials sciences,[37] we
hoped to synthesize the fused indole ring derivatives from 4-amino-2(5H)-furanone 1
by the Pd-catalyzed C-H activation in the presence of oxidant DIB. Surprisingly, a
difunctionalization reaction of hypervalent organic iodine reagent DIB as a transfer
reagent was discovered even without Pd catalysts (Scheme 1).
2(5H)-Furanone is a basic structural unit in many bioactive compounds,[38–41]
and some simple 2(5H)-furanones are important intermediates.[42–45] Therefore,
among the research on 2(5H)-furanone chemistry,[46–59] some attention has been
focused on the efficient synthesis of iodo-2(5H)-furanones also for their diverse value
recently.[59–66] However, there is only a general report available for the synthesis of
3-iodo-2(5H)-furanone. Even so, some uncommon reagents are used at a strictly
low temperature, and the atom economy is also lower with the yields of 54–89%
(mostly more than 70%).[59] Herein, we report an efficient and convenient synthetic
method for the 4-diarylamino-3-iodo-2(5H)-furanones 2 (Scheme 1) by hypervalent
iodine transfer reagent DIB with the yields of 57–91% (usually more than 73%).
Scheme 1. Unexpected difunctionalization of compound 1.

1946
F. XUE ET AL.
RESULTS AND DISSCUSSION
Optimization of Reaction Conditions
Because of the very useful oxidizing properties, especially their benign environ-
mental character and commercial availability, many hypervalent organic iodine
reagents, including inexpensive PhI(OAc)2 (DIB), have been extensively used in dif-
ferent oxidations.[1,23,24,26–31] When we used DIB as an oxidant to promote the intra-
molecular C-C coupling in the substrate 5-methoxy-4-phenylamino-2(5H)-furanone
1a, compound 2a was unexpectedly obtained via the simultaneous a-iodination and
Nb-arylation reaction even without any metal catalysts (Scheme 2).
To the best of our knowledge, only Chen et al. have reported the concurrent
a-iodination and N-arylation of cyclic b-amino ketenes by DIB with the yields of
35–91% (usually more than 71%).[67] However, using DIB as a hypervalent organic
iodine transfer reagent, there is no report on the simultaneous a-iodination and
Nb-arylation of b-amino-2(5H)-furanones before. More noticeably, b-amino-2(5H)-
furanones as a kind of biological heterocyclic compounds,[38,68–72] especially
5-alkoxy-4-amino-2(5H)-furanones 1 with lactone and acetal structures, are more
sensitive than b-amino ketenes to the reaction environment, indicating that their
difunctionalization simultaneously yields two different functional groups that are
more important for the synthesis of potential bioactive compounds. Thus, we inves-
tigated this novel reaction of b-amino-2(5H)-furanones. Using 5-methoxy-4-
phenylamino-2(5H)-furanone 1a as typical substrate (Scheme 2), the suitable reaction
conditions were optimized first (Table 1).
The evaluations on the influences of different DIB dosages show that the yield
is obviously elevated with the increase of DIB dosage (Table 1, entries 1–3) and 1.5
eq. DIB is the most advantageous for the reaction with the greatest yield of 86%
(entry 3). With continually increasing DIB dosage, there is a trend of lower yields
(entries 4 and 5). Therefore, the suitable DIB dosage should be 1.5 eq. Reaction sol-
vent is another important influencing factor. It can be seen that, among the different
solvents (entries 3, 6–11), CH3CN is the best (entry 3).
When the reaction temperature is decreased from 60 ꢀC to 30 ꢀC, the yield can be
lowered (entry 12), but when increasing the temperature, the yield does not increase
yet (entry 13). Thus, the suitable reaction temperature should be 60 ꢀC (entry 3).
Similarly, shortening the reaction time is not beneficial to the yield (entry 14), and
extending the time cannot further improve the yield yet as anticipated (entries 15
and 16), indicating that the suitable reaction time should be 40 h (entry 3). Therefore,
the optimal reaction conditions for this Nb-arylation and a-iodination reaction can be
summarized as follows: 1.5 eq. PhI(OAc)2 in CH3CN at 60 ꢀC for 40 h.
Scheme 2. Synthesis of compound 2a by the reaction of 1a with DIB.

SYNTHESIS OF 4-DIARYLAMINO-3-IODO-2(5H)-FURANONES
Table 1. Effects of different conditions on the reaction
1947
Entrya
DIB dosage (eq.)
Solvent
Time (h)
Temperature (ꢀC)
Yieldb (%)
1
2
0.5
1.0
1.5
2.0
2.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
CH3CN
40
40
40
40
40
40
40
40
40
40
40
40
40
24
70
96
60
60
60
60
60
60
60
60
60
60
60
30
90
60
60
60
51
76
CH3CN
CH3CN
CH3CN
CH3CN
ClCH2CH2Cl
CH2Cl2
EtOAc
3
86
71
4
5
63
73
6
7
45
8
Trace
Trace
Trace
65
9
DMSO
DMF
10
11
12
13
14
15
16
Toluene
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
36
86
40
86
87
aReaction conditions: 5-methoxy-4-phenylamino-2(5H)-furanone 1a (0.2 mmol) and solvent (totally
10 mL).
bIsolated yield.
Influences of Different Substrates
Under the optimized conditions, the substrate scopes are examined (Table 2).
Though different substrates 1 can react smoothly with the yields of 57–91% (usually
more than 73%), it seems that whether methoxy or benzyloxy, or ethoxy in 5-position
of 2(5H)-furanone 1, the change of the yields is not regular. Similarly, whether
p-position substituted group of benzene ring in 4-arylamino of the substrates 1 is
an electron-withdrawing group or electron-donating group has no obvious effects
on the reaction. In other words, different groups can be tolerated in the process.
Of course, with the increase of the number of electron-donating group (e.g.,
methyl) in 4-arylamino, the yields have a rising trend (Table 2, entries 2 vs 3, 10 vs
11). Interestingly, if there is p-bromo substituted or m-chloro substituted (especially
the latter) benzene ring in 4-arylamino of the substrates 1, the reaction usually has
a relatively greater yield than other cases (entries 7, 8, 15, and 16). However, the rea-
sons for these phenomena are not very clear yet; they may be related to the reaction
mechanism, which is further discussed in the following.
At the same time, the structures of all new products 2a–2s are demonstrated
by their Fourier-transform infrared (FTIR), ultraviolet (UV), NMR spectroscopic,
mass spectrometry (MS), and elemental analysis data. Meanwhile, the structures
of the products 2a and 2e are also confirmed by the x-ray crystallographic data,
and their ORTEP structures are respectively shown in Figs. 1 and 2.
Possible Reaction Mechanism
There is no report on the synthesis of 4-diarylamino-3-iodo-2(5H)-furanones
via the difunctionalizable transfer reagent DIB. According to the literature on the

1948
F. XUE ET AL.
Table 2. Scope of 5-alkoxy-4-amino-2(5H)-furanone substrates 1 in the simultaneous a-iodination and
Nb-arylation reaction
Entry
Substrates 1
Product 2
Isolated yield (%)
1
86
2
3
57
73
4
5
58
63
6
7
61
81
(Continued )

SYNTHESIS OF 4-DIARYLAMINO-3-IODO-2(5H)-FURANONES
Table 2. Continued
1949
Entry
Substrates 1
Product 2
Isolated yield (%)
8
91
74
60
78
61
73
9
10
11
12
13
14
64
(Continued )

1950
F. XUE ET AL.
Table 2. Continued
Entry
Substrates 1
Product 2
Isolated yield (%)
15
16
82
89
17
18
19
83
79
66
hypervalent organic iodine reagents,[17,18,67] a possible mechanism for the
Nb-arylated a-iodo reaction in the presence of DIB is proposed (Scheme 3).
First, a-iodo iminium salt A would be formed from substrates 1 and
PhI(OAc)2. However, intermediate A is greatly unstable for the presence of a lactone
ring system, which would be deprotonated instantly to give the stabilized a-iodo
butenolide B. With the leave of AcOH, intermediate B would be converted to
iodine-nitrogen 1,4-dipoles C.[5,6,67,73] Finally, the ipso attack of the negative
nitrogen on the phenyl ring, through a five-membered cyclic intermediate D,[67,74]
would afford the Nb-arylated a-iodo butenolide 2 (Scheme 3).
It is obvious that the R2 substituent on benzene ring in the substrates 1 is not
greatly related to the stability of the important intermediate D. Therefore, whether
R2 substituent is electron-withdrawing or electron-donating, it has relatively less
effect on the reaction (Table 2). Of course, according to the reaction mechanism,

SYNTHESIS OF 4-DIARYLAMINO-3-IODO-2(5H)-FURANONES
1951
Figure 1. ORTEP structure of compound 2a.
not only the N-arylated substituted furanones but also the N-alkylated substrates are
suitable for this system.[67] Meanwhile, this is an intramolecular functional group
transfer process indeed, which is confirmed by the comparative experiment.
Scheme 4 is purposely designed as an intermolecular reaction, but no corresponding
product was obtained or detected.
According to the reaction mechanism and the results in the
literature,[5,6,17,18,67,73,74] we can conclude that, as an important difunctionalizable
transfer reagent, DIB is also suitable for the simultaneous a-iodination and
Ob-arylation reaction of b-hydroxyl-a,b-unsaturated carbonyl compounds. There-
fore, these investigations provide a simple difunctionalized conversion route with
greater atom economy for b-amino(hydroxyl)-a,b-unsaturated carbonyl compounds,
including 4-aryl-amino-2(5H)-furanones.
It is noticeable that not only 4-amino-2(5H)-furanones can be a-iodinated in
this way, but also the product 4-diarylamino-3-iodo-2(5H)-furanones can be easily
dehalogenated.[57] Thus, further combining the different conversion of Csp2-I in
organic synthesis,[59,75–77] the simple and easy difunctionalizable reactions of simul-
taneous a-iodination and N(O)b-arylation can provide a good platform for more
functional interconversions using iodo a,b-unsaturated carbonyl compounds as inter-
mediates. Of course, this result also makes the intramolecular cyclization of
4-arylamino-2(5H)-furanones via the Pd-catalyzed C-H activation more possible,
which is in progress in our laboratory.

1952
F. XUE ET AL.
Figure 2. ORTEP structure of compound 2e.
Scheme 3. Plausible mechanism for DIB-promoted difunctionalization.
Scheme 4. Designed intermolecular difunctionalization reaction promoted by DIB.

SYNTHESIS OF 4-DIARYLAMINO-3-IODO-2(5H)-FURANONES
1953
CONCLUSION
In summary, a series of novel 3-iodo-2(5H)-furanone derivatives containing
multibenzene rings are synthesized via the green difunctionalizable transfer reagent
PhI(OAc)2. This method is very simple, convenient, and mild with greater atom
economy. It provides a practical route for the synthesis of some potential bioactive
2(5H)-furanone compounds with multifunctional groups.
EXPERIMENTAL
All melting points were determined on an X-5 digital melting-point apparatus
and were uncorrected. Infrared spectra were recorded on a Bruker Vector 33 FT-IR
instrument by liquid film method in the absorption range of 4000–450 cmꢁ1. 1H and
13C NMR spectra were obtained in CDCl3 on a Varian DRX 400-MHz spectrometer,
and tetramethylsilane (TMS) was used as an internal standard. The UV absorption
peaks were measured by Shimazu UV-2550 ultraviolet absorption detector with
dichloromethane as a solvent. Elemental analysis was performed on a Thermo
Flashea TM 112 elemental analyzer. The mass spectra (MS) were recorded on
Thermo LCQ DECA XP MAX mass spectrometer.
All reagents and solvents were commercially available and used as received.
The intermediates 5-alkoxy-4-arylamino-2(5H)-furanones 1 were prepared according
to the literature.[57b]
Typical Procedure
A flame-dried 25-mL round-bottomed flask was charged with 5-alkoxy-4-
arylamino-2(5H)-furanones 1 (0.2 mmol) in CH3CN (5 mL), and PhI(OAc)2
(1.5 eq.) in CH3CN (5 mL) was added dropwise in 25 min. The mixture was stirred
at 60 ꢀC, and the reaction was monitored by TLC. After the completion of the reac-
tion (about 40 h), the reaction was allowed to cool to room temperature. The reaction
mixture was diluted with a saturated aqueous solution of NH4Cl (20 mL) and
extracted with ethyl acetate (3 ꢂ 20 mL). Then, the organic layer was dried over anhy-
drous MgSO4, filtered, and concentrated in vacuo. The purification of the residue
by silica-gel column chromatography yielded the desired compounds 2 in 57–91%
isolated yields (Table 2).
Typical Characterization Data for Compound 2a
Yellow solid, yield 86%, mp 177.9–179.2 ꢀC; UV-vis (CH2Cl2) kmax: 319 nm; 1H
NMR (400 MHz, CDCl3) d, ppm: 3.20 (s, 3H), 5.73 (s, 1H), 7.18 (d, J ¼ 8 Hz, 4H),
7.29 (t, J ¼ 8 Hz, 2H), 7.38–7.42 (m, 4H); 13C NMR (100 MHz, CDCl3) d, ppm:
55.36, 56.86, 101.65, 126.35, 126.94, 127.10, 127.13, 129.32, 129.42, 142.60, 142.64,
162.47, 169.73; IR (film) n, cmꢁ1: 3059, 2924, 2851, 1761, 1616, 1585, 1489, 1452,
1377, 1323, 1153, 1119, 951, 750, 698, 515; ESI-MS m=z (%): 408 ([M þ H]þ, 100),
430 ([M þ Na]þ, 93). Anal. calcd. for C17H14INO3: C, 50.14; H, 3.47; N, 3.44.
Found: C, 50.32; H, 3.21; N, 3.57.

1954
F. XUE ET AL.
X-Ray Structure Determination of Compounds 2a and 2e
Two suitable x-ray-quality crystals of compound 2a and 2e were respectively
grown by slow evaporation of petroleum ether=dichloromethane solvent mixture
in the temperature variation of 25 ꢀC. Diffraction data of 2a and 2e were collected
on a Bruker APEX II Smart CCD diffractometer equipped with graphite-
˚
monochromated MoKa radiation (k ¼ 0.71073 A) using the x-scan technique. The
data were corrected for absorption with the SADABS program. The structures were
solved by direct methods using the SHELXS-97 program and all the nonhydrogen
atoms were refined anisotropically with the full-matrix leastsquares on F2 using the
SHELX-97 program.[78] Crystallographic data for the structures reported in this
article have been deposited with the Cambridge Crystallographic Data Centre as sup-
plementary publication nos. 962686 and 962687. Copies of the data can be obtained
free of charge on application to the director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK. E-mail: deposit@ccdc.cam.ac.uk.
FUNDING
The authors are grateful to the Third Talents Special Funds of Guangdong
Higher Education (No. Guangdong-Finance-Education [2011]431), the National
Natural Foundation of China (No. 20772035), and the Guangdong Natural Science
Foundation (No. S2011010001556) for financial support.
SUPPLEMENTAL MATERIAL
Full experimental detail, characterization data for other new compounds
2b–2s, 1H NMR and 13C NMR spectra, and MS data for all new compounds
2a–2s can be can be accessed on the publisher’s website.
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