Easy preparation of [bis(trifluoroacetoxy)iodo]arenes from iodoarenes, with sodium percarbonate as the oxidant

Article abstract of DOI:10.3390/71100810

Easy and effective preparations of the nearly pure [bis(trifluoroacetoxy) iodo]arenes, ArI(OCOCF)₃, from some iodoarenes, ArI, are reported, using an anhydrous) sodium (percarbonate/(CF₃CO)₂O/CH ₂Cl₂ system. The colorless, freshly prepared (ArI(OCOCF)₃)₂ thus obtained were 98-99% pure (by iodometry).

Full text of DOI:10.3390/71100810

Molecules 2002, 7, 806-809
molecules
ISSN 1420-3049
http://www.mdpi.org
Easy Preparation of (Diacetoxyiodo)arenes from Iodoarenes
with Sodium Percarbonate as the Oxidant†
Agnieszka Zielinska and Lech Skulski*
Chair and Laboratory of Organic Chemistry, Faculty of Pharmacy, Medical University, PL 02-097,
1 Banacha Street, Warsaw, Poland.
†
This short paper was presented at the Sixth Electronic Conference on Synthetic Organic Chemistry
(ECSOC-6, http://www.mdpi.net/ecsoc-6/), September 1-30, 2002 (paper A006).
* To whom correspondence should be addressed. E-mail: lskulski@farm.amwaw.edu.pl; Tel./Fax:
+(48) 22 5720643
Received: 15 October 2002; in revised form: 18 October 2002 / Accepted: 18 October 2002 /
Published: 30 November 2002
Abstract: Easy and effective preparations of nearly pure (diacetoxyiodo)arenes, ArI(OAc)2,
from iodoarenes, ArI, are reported. In most cases the crude colorless products thus obtained
need not be further purified, i.e., by recrystallization. As an example, the PhI(OAc)2 thus
prepared was 99% pure (by iodometry).
Keywords: (Diacetoxyiodo)arenes from iodoarenes, sodium percarbonate as oxidant
Introduction
(Diacetoxyiodo)arenes, ArI(OAc)2, and particularly the parent compound (diacetoxyiodo)benzene,
PhI(OAc)2, have been known for a long time [1]. The well - pronounced electrophilic character of
organic hypervalent iodine compounds is utilized in many organic syntheses, while
(diacetoxyiodo)arenes are used as potent, often chemoselective, oxidizing agents. They are also used
for
the
facile
syntheses
of,
for
example,
[bis(trifluoroacetoxy)iodo]arenes,
[hydroxy(tosyloxy)iodo]arenes (selective oxidants), and aromatic iodonium salts (arylating reagents).

Molecules 2002, 7
807
Several methods are available for the preparation of (diacetoxyiodo)arenes [2, 3]. Historically, the first
member – (diacetoxyiodo)benzene (DIB) – was synthesized by Willgerodt in 1892, by dissolving
iodosylbenzene in hot acetic acid [4]. So far, the substrates used have generally been:
-
-
iodosylarenes dissolved in glacial acetic acid;
(dichloroiodo)arenes in which the chlorine atoms are exchanged by acetoxy groups coming either
from silver, lead(II) or sodium acetate, or from acetic acid in the presence of mercury(II) oxide in
chlorinated solvents;
-
iodoarenes are oxidized in warm glacial acetic acid by either peracetic acid, sodium perborate
tetrahydrate, or electrolytically [5].
The standard, and most general, method for the synthesis of ArI(OAc)2 (oxidative diacetoxylation
of ArI by warm peracetic acid solutions) is, in fact, a very prolonged reaction (12-16 hours), and the
utmost care should be taken to maintain the exact temperature, 40ûC. Better methods were published in
references [2] and [3].
Results and Discussion
In our laboratory, we have recently devised a simple and efficient method for preparing ArI(OAc)2
from the respective iodoarenes in an anhydrous ternary solvent system: Ac2O/AcOH/CH2Cl2, using
commercial sodium percarbonate, 2Na2CO3·3H2O2, as the oxidant (Scheme 1). Our results are
summarized in Table 1.
Scheme 1
AcOH/Ac2O/CH2Cl2
3ArI + 2Na2CO3·3H2O2 + 8Ac2O
3ArI(OAc)2 + 6AcOH + ↓4AcONa
+ ↑ 2CO2
25-40ûC, ca. 6.5h, 18-84%
Table 1. Yields and melting points (uncorrected) of the (diacetoxyiodo)arenas prepared
Substrate
Product
Yield (%)
Mp (oC)
159-161
179-181
139-140
150-152
Lit. [3] mp (oC)
161.1-162.2
177.0-179.8
140.0-142.0
154
C6H5-I
4-FC6H4-I
C6H5-I(OAc)2
79
80
84
76
28
76
74
20
18
70
4-FC6H4-I(OAc)2
2-MeC6H4-I(OAc)2
3-MeC6H4-I(OAc)2
4-MeC6H4-IO2
2-MeOC6H4-I(OAc)2
3-MeOC6H4-I(OAc)2
2-ClC6H4-I(OAc)2
3-ClC6H4-I(OAc)2
4-ClC6H4-IO2
2-MeC6H4-I
3-MeC6H4-I
4-MeC6H4-I
2-MeOC6H4-I
3-MeOC6H4-I
2-ClC6H4-I
3-ClC6H4-I
4-ClC6H4-I
230 (expl.) 229 (dec.)
146-148
129-131
140-142
148-151
146.9-150.1
133-135
140-142
153.1-154.7
240 (expl.) 243 (expl.)

Molecules 2002, 7
808
Acknowledgements
We are thankful to Dr. Pawel Kazmierczak for his valuable advice.
Experimental
General
Chemical structures of the compounds in Table 1 were confirmed by microanalyses at the Institute
of Organic Chemistry, the Polish Academy of Sciences, Warsaw.
Optimized Procedure for Preparing (Diacetoxyiodo)arenes from Iodoarenes
Sodium percarbonate (18.4 mmol, 330% excess) was slowly added portionwise to a stirred mixture
of Ac2O (7.0 mL), AcOH (5.8 mL), and CH2Cl2 (40 mL). The stirring was continued for 1.5 h at ≤
30ûC. An appropriate iodoarene was then added (6.4 mmol), and the reaction mixture was then stirred
at 40ûC for 5 h. After cooling, the precipitated CH3COONa was collected by filtration under reduced
pressure, washed with CH2Cl2 (2 x 15 mL) and discarded. The filtrates were evaporated under vacuum,
and cold (0-5 ûC) 10% aq. CH3COOH (15 mL) was rapidly added. The flask was left in a cooler for a
few hours. The colorless crystals formed were collected by filtration, washed with hexane and air-dried
in the dark. Most of those crude products thus obtained need not be further purified, as they were 96-
99% pure, according to iodometric analysis [6]. When necessary, the crude products were
recrystallized from AcOEt/Ac2O (9:1, v/v) [2]. They should be stored in the dark, preferably in a
cooler. See Table 1 for more details. Under these conditions 4-iodotoluene and 4-chloroiodobenzene
were unexpectedly oxidized to the corresponding iodylarenes (recrystallized from boiling water).
References
1. Willgerodt, C. Die organischen Verbindungen mit mehrwertigem Jod; Enke Verlag: Stuttgart,
1914.
2. Kazmierczak, P.; Skulski, L. A Simple, Two-Step Conversion of Various Iodoarenes to
(Diacetoxyiodo)arenes with Chromium(VI) Oxide as the Oxidant. Synthesis 1998, 1721-1723, and
references therein.
3. Kazmierczak, P.; Skulski, L.; Kraszkiewicz, L. Syntheses of (Diacetoxyiodo)arenes or Iodylarenes
from Iodoarenes, with Sodium Periodate as the Oxidant. Molecules 2001, 6, 881-891; Avail. at
URL: http://www.mdpi.org/molecules/papers/61100881.pdf
4. Willgerodt, C. Zur Kenntniss aromatischer Jodidchloride, des Jodoso- und Jodobenzols. Ber.
Dtsch. Chem. Ges. 1892, 25, 3494-3502, p3498.

Molecules 2002, 7
809
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http://www.mdpi.org/molecules/papers.51201331.pdf
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Sample Availability: Available from the authors.
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