Easy and safe preparations of (diacetoxyiodo)arenes from iodoarenes, with Urea-Hydrogen Peroxide adduct (UHP) as the oxidant and the fully interpreted 1H- and 13C-NMR spectra of the products

Article abstract of DOI:10.3390/10010190

An easy and safe, though only moderately effective method is presented for preparing (diacetoxyiodo)arenes, ArI(OAc)2, from iodoarenes, ArI, using the commercially available and easily handled urea-hydrogen peroxide adduct (UHP) as the oxidant. The reactions take place in anhydrous AcOH/Ac₂O/AcONa (a catalyst) mixtures, at 40°C for 3.5 h to afford the purified ArI(OAc)₂ in 37-78% yields. The fully interpreted ¹H- and ¹³C-NMR spectra of the ArI(OAc)₂ products are reported.

Full text of DOI:10.3390/10010190

Molecules 2005, 10, 190–194
molecules
ISSN 1420-3049
http://www.mdpi.org
Easy and Safe Preparations of (Diacetoxyiodo)arenes from
Iodoarenes, with Urea-Hydrogen Peroxide Adduct (UHP) as the
1
13
Oxidant and the Fully Interpreted H- and C-NMR Spectra of
the Products†
Agnieszka Zielinska and Lech Skulski *
Chair and Laboratory of Organic Chemistry, Faculty of Pharmacy, Medical University, 1 Banacha
Street, PL 02-097 Warsaw, Poland
† This short paper was presented at the Seventh Electronic Conference of Synthetic Organic Chemistry
(ECSOC-7, http://www.mdpi.net/ecsoc-7), November 1-30, 2003 (paper A001).
*
To whom correspondence should be addressed; E-mail: lechskulski@yahoo.com; Tel./Fax: (+48) 22
5720643;
Received: 30 April 2004; in revised form: 12 January 2005 / Accepted: 13 January 2005 / Published:
31 January 2005
Abstract: An easy and safe, though only moderately effective method is presented for
preparing (diacetoxyiodo)arenes, ArI(OAc)2, from iodoarenes, ArI, using the
commercially available and easily handled urea-hydrogen peroxide adduct (UHP) as the
oxidant. The reactions take place in anhydrous AcOH/Ac2O/AcONa (a catalyst)
mixtures, at 40 ºC for 3.5 h to afford the purified ArI(OAc)2 in 37-78% yields. The fully
interpreted 1H- and 13C-NMR spectra of the ArI(OAc)2 products are reported.
Keywords: (Diacetoxyiodo)arenes, iodoarenes, urea-hydrogen peroxide adduct as
oxidant, 1H- and 13C-NMR spectra
Introduction
(Diacetoxyiodo)arenes, ArI(OAc)2, and particularly the parent compound (diacetoxyiodo)benzene,
PhI(OAc)2, have been known for a long time [1,2]. They are used in organic synthesis as potent, often
chemoselective, oxidizing agents. They are also used for facile syntheses of several classes of aromatic

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Molecules 2005, 10
hypervalent iodine compounds, e.g. [bis(trifluoroacetoxy)iodo]arenes, [hydroxy(tosyloxy)iodo]arenes,
aromatic iodonium salts [3], etc. In our two latest reviews [4,5] we relate and explain our previous
novel syntheses of ArI(OAc)2 from corresponding ArI, as well our novel aromatic iodination methods,
and preparations of several classes of aromatic hypervalent iodine compounds, easily attainable from
aromatic iodides; particularly see ref. 4, pp. 1343-1345 and 1352-1354.
During the course of our systematic studies on effective and easy preparations of ArI(OAc)2 from
the corresponding ArI [4, 5], we have devised several methods for their syntheses. In this work we
have oxidized seven iodoarenes (Table 1) in anhydrous AcOH/Ac2O mixtures; the reactions did not
proceed in the absence of sodium acetate, AcONa (used in a stoichiometric quantity) – cf. our former
work [6], where its presence in the reaction mixtures was also indispensable. The reactions took place
as follows:
AcOH/Ac2O/AcONa
ArI + [urea] ··· H2O2
ArI(OAc)2 + [acetylurea] + H2O
3. 5 h ; 40 °C
In our opinion, the novel method presented in this paper is easy and safe, albeit only moderately
effective (yields are in the 37-78% range). For the first time, we have used UHP as the oxidant. This
compound, which is now commercially available, may be considered a “dry carrier” of the unstable
and hazardous hydrogen peroxide. The UHP solid is easy to handle, safe and stable at room
temperature. Its ability to release oxidative species in water and organic media has made it a useful
reagent in organic synthesis [7].
Experimental
General
Melting points submitted in the Table 1 are uncorrected. All the reagents were purchased from
Aldrich or Lancaster and were used without further purification. The NMR spectra were run in CDCl3
solutions at room temperature, with TMS as an internal standard; the spectra were recorded on a
1
Brucker AVANCE DMX 400 spectrometer. To obtain better assignments, also H – 13C NMR
correlation spectra were recorded.
Optimized Procedure for Preparing (Diacetoxyiodo)arenes from Iodoarenes:
Urea-Hydrogen Peroxide adduct, 98% (3.02 g, 31.5 mmol, 350% excess) was added portionwise to
a stirred mixture of glacial AcOH (24 mL) with Ac2O (9 mL). An appropriate iodoarene (7 mmol) was
slowly added, the solution was cooled to 10-15 °C, and powdered AcONa (1.26 g, 15 mmol) was
suspended. Stirring at 40 °C was continued for 3.5 h. After cooling, water (35 mL) was slowly added
with stirring. The precipitated ArI(OAc)2 were collected by filtration, washed on the filter with a cold
(5-10 °C) 10% aq. AcOH, and air-dried in the dark; if necessary, they were recrystallized from
AcOEt/Ac2O (9:1, v/v). The oily or semisolid products were extracted with CH2Cl2, the combined

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Molecules 2005, 10
extracts were dried over anhydrous Na2SO4 and filtered, the solvent was distilled off under vacuum,
and the solidified residues were recrystallized from AcOEt/Ac2O (9:1).The purities and homogeneities
of the purified ArI(OAc)2 were firstly checked by TLC, and next confirmed by their melting points, all
close to those reported in the literature (Table 1). Their chemical structures were fully supported by the
1H- NMR (Table 2) and 13C-NMR (Table 3) spectra (in CDCl3).
Table 1. Final yields and melting points (uncorrected) of the purified (diacetoxyiodo)-
arenes obtained from the corresponding iodoarenes.
Yield
(%)
44
37
78
64
69
48
57
Mp
(°C)
Lit. Mp
(°C)
161-163 [6]
144-145 [8]
179 [8]
140-142 [6]
128 [9]
147-149 [6]
133-135 [6]
Substrate
Product
C6H5I
3-FC6H4I
4-FC6H4I
C6H5I(OAc)2
3-FC6H4I(OAc)2
4-FC6H4I(OAc)2
161-162
143-145
177-180
142-147
126-128
145-147
130-132
2-MeC6H4I
2,4-Me2C6H3I
2-MeOC6H4I
3-MeOC6H4I
2-MeC6H4I(OAc)2
2,4-Me2C6H3I(OAc)2
2-MeOC6H4I(OAc)2
3-MeOC6H4I(OAc)2
Table 2. 1H-NMR chemical shifts for pure (diacetoxyiodo)arenes. Cf. our present
experimental values with those previously reported [11].
Chemical shifts δ (ppm)
Product
CH3
CH3
(p)
CH3
in OAc
H2
H3
H4
H5
H6 OCH3
(o)
8.10 7.50 7.60 7.50 8.10
2.01
s
2.02
s
2.02
s
1.98
s
1.98
s
1.97
s
2.02
s
C6H5I(OAc)2
3-FC6H4I(OAc)2
-
-
-
-
-
-
-
-
-
-
-
-
d
7.29
d
t
t
t
d
7.84 7.51 7.84
t
-
m
t
8.09 7.19
7.19 8.09
4-FC6H4I(OAc)2
-
d
t
t
d
7.52 7.52 7.26 8.17
2.72
s
2.68
s
2-MeC6H4I(OAc)2
2,4-Me2C6H3I(OAc)2
2-MeOC6H4I(OAc)2
3-MeOC6H4I(OAc)2
-
d
7.31
s
t
t
d
7.05 8.04
d
2.40
s
-
-
-
d
7.16 7.59 7.04 8.14 3.99
-
-
-
-
d
t
t
d
s
7.65
s
7.10 7.41 7.67 3.87
-
d
t
s
s

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Molecules 2005, 10
Table 3. 13C NMR chemical shifts for pure (diacetoxyiodo)arenes and coupling constants
J
J
19 F−13C
19 F−C−13C
and
(Hz). Cf. our present experimental values with those
previously reported incompletely [10, 12].
Chemical shifts of aromatic C atoms in δ (ppm)
Product
C1
C2
C3
C4
C5
C6
121.58
134.94
130.96
131.74
130.96
134.94
C6H5I(OAc)2
s
120.65
s
s
122.56
d
s
161.33
d
s
119.26
d
s
132.33
s
s
130.87
s
3-FC6H4I(OAc)2
J = 24.6 J = 253.0 J = 20.7
137.74
s
115.64
s
118.59
d
164.63
d
118.82
d
135.95
s
4-FC6H4I(OAc)2
J = 22.6 J = 253.7 J = 22.6
127.29
140.72
128.51
130.97
132.82
137.30
2-MeC6H4I(OAc)2
2,4-Me2C6H3I(OAc)2
2-MeOC6H4I(OAc)2
3-MeOC6H4I(OAc)2
s
s
s
s
s
s
124.09
143.73
131.78
140.66
129.40
137.32
s
s
s
s
s
s
113.63
156.46
112.33
134.70
122.91
137.94
s
121.62
s
s
120.68
s
s
160.72
s
s
118.14
s
s
131.73
s
s
127.25
s
Chemical shifts of C atoms in substituents in δ (ppm)
Product
CH3
(o)
CH3
(p)
CH3
C=O
OCH3
in OAc
in OAc
20.36
176.39
C6H5I(OAc)2
3-FC6H4I(OAc)2
-
-
-
-
-
-
-
-
-
-
-
-
s
s
20.51
176.76
s
s
20.47
176.66
4-FC6H4I(OAc)2
s
s
25.68
20.42
176.53
2-MeC6H4I(OAc)2
2,4-Me2C6H3I(OAc)2
2-MeOC6H4I(OAc)2
3-MeOC6H4I(OAc)2
s
25.56
s
s
s
21.64
s
20.52
176.57
s
20.54
s
s
57.06
176.82
-
-
s
55.92
s
s
176.64
s
20.56
s
-
-

194
Molecules 2005, 10
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Sample Availability: The samples of pure (diacetoxyiodo)arenes, prepared one year ago and kept in a
fridge, have deteriorated in full or in part. Hence, they are not available.
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