Bismuth(III) nitrate pentahydrate: A convenient and selective reagent for conversion of thiocarbonyls to their carbonyl compounds

Article abstract of DOI:10.1016/S0040-4039(02)02516-9

A variety of thioamides and thioureas are rapidly transformed to their oxo derivatives with Bi(NO₃)₃·5H₂O in excellent yields. However, thiono esters and thioketones are converted to their corresponding carbonyl compounds in only poor yields. Bi(NO₃)₃·5H₂O is relatively non-toxic, insensitive to air and inexpensive. These features coupled with the selective deprotection of thioamides and thioureas in the presence of thiono esters and thioketones make this method an attractive alternative to the existing routes for deprotection of thiocarbonyl compounds.

Full text of DOI:10.1016/S0040-4039(02)02516-9

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 591–594
Bismuth(III) nitrate pentahydrate: a convenient and selective
reagent for conversion of thiocarbonyls to their
carbonyl compounds
a,
b,
b
Iraj Mohammadpoor-Baltork, * Mohammad Mehdi Khodaei * and Kobra Nikoofar
a
Department of Chemistry, Isfahan University, Isfahan 81744, Iran
b
Department of Chemistry, Razi University, Kermanshah 67149, Iran
Received 18 August 2002; revised 28 October 2002; accepted 8 November 2002
Abstract—A variety of thioamides and thioureas are rapidly transformed to their oxo derivatives with Bi(NO ) ·5H O in excellent
3
3
2
yields. However, thiono esters and thioketones are converted to their corresponding carbonyl compounds in only poor yields.
Bi(NO ) ·5H O is relatively non-toxic, insensitive to air and inexpensive. These features coupled with the selective deprotection of
3
3
2
thioamides and thioureas in the presence of thiono esters and thioketones make this method an attractive alternative to the
existing routes for deprotection of thiocarbonyl compounds. © 2002 Elsevier Science Ltd. All rights reserved.
Functional group manipulations are of paramount
importance to synthetic organic chemists and hence, the
development of novel transformations still remains of
great interest. The conversion of thiocarbonyl com-
pounds to their oxygen analogues has received consid-
erable attention. Different methods and reagents such
Recently, we introduced Bi(III) salts as efficient cata-
24
lysts for the conversion of oxiranes to thiiranes,
25
deprotection of 1,1-diacetates,2 alcoholysis, hydrolysis
6
and acetolysis of epoxides, deprotection of silyl
27
28
ethers, conversion of epoxides to 1,3-dioxolanes,
acetylation, benzoylation and formylation of alcohols
1
2
29
as sodium peroxide, dimethyl selenoxide, diaryl
and phenols. As part of our ongoing program and
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4
selenoxide, t-butyl hypochlorite, bromate or iodate
interest in the introduction of new applications of
Bi(III) salts, we became interested in developing a
convenient method for conversion of thiocarbonyls to
their carbonyl compounds. In this respect, we now
report Bi(NO ) ·5H O as an efficient reagent for the
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6
7
solutions, diaryl telluroxide, singlet oxygen, tetra-
butylammonium hydrogensulfate/NaOH,
8
benzene-
dimethyl
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10
seleninic
anhydride,
thiophosgene,
1
1
12
sulfoxide/iodine,
NOBF ,
m-chloroperbenzoic
4
3
3
2
1
3
+
14
15
3
0
acid, soft NO species, trifluoroacetic anhydride,
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deprotection of thioamides and thioureas (Scheme 1).
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clay supported ferric nitrate, manganese dioxide,
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19
p-nitrobenzaldehyde/TMSOTf, N-nitrosoamines, 2-
nitrobenzenesulfonyl chloride/potassium superoxide,
clayfen or clayan/MW and Caro’s acid supported on
Bismuth(III) nitrate pentahydrate is a commercially
available reagent and requires no special handling. Sev-
eral solvents including acetonitrile, dichloromethane,
chloroform, ether and n-hexane were investigated dur-
ing the course of this study; the best results were
achieved using acetonitrile. As shown in Table 1, when
a variety of primary, secondary and tertiary thioamides
and thioureas were reacted with an equimolar amount
of Bi(NO ) ·5H O in refluxing acetonitrile, the corre-
20
2
1
2
2
silica gel have already been reported in the literature
for this purpose. However, some of these methods
suffer from disadvantages such as long reaction times,
the use of toxic or expensive reagents, and difficult
workup procedures. Therefore, the introduction of new
methods and reagents for this transformation is still in
demand.
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3
2
sponding carbonyl compounds were obtained in excel-
The applications of bismuth compounds to organic
23
transformations have been extensively investigated.
Keywords: bismuth(III) nitrate pentahydrate; thiocarbonyls; carbonyl
compounds.
*
Corresponding author. E-mail: imbaltork@sci.ui.ac.ir
Scheme 1.
0
040-4039/03/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)02516-9

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Table 1. Conversion of thiocarbonyls to carbonyl compounds with Bi(NO ) ·5H O
3
3
2

I. Mohammadpoor-Baltork et al. / Tetrahedron Letters 44 (2003) 591–594
593
Scheme 2.
lent yields (entries 1–31). However, under the same
reaction conditions thiono esters and thioketones are
resistant towards deprotection with this reagent and the
corresponding carbonyl compounds were obtained in
relatively poor yields (entries 32–37).
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We have also investigated the chemoselectivity of this
method and the results are shown in Scheme 2. As can
be seen, thioamides and thioureas are selectively con-
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In conclusion, this work demonstrates a new, useful
and selective method for deprotection of thioamides
and thioureas. The advantages include excellent yields,
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3
1
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solution of substrate (1 mmol) in CH CN (10 mL) was
3
prepared. Bi(NO ) ·5H O (1 mmol) was added to the
3
3
2
solution and the mixture was refluxed for the appropriate
time according to Table 1. The progress of the reaction
2
49–267; (b) Nattier, B. A.; Eash, K. J.; Mohan, R. S.
Synthesis 2001, 1010–1012.
was followed by TLC (eluent: CCl /EtOAc: 4/1). The
4
2
4. (a) Mohammadpoor-Baltork, I.; Aliyan, H. Synth. Com-
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reaction mixture was filtered and the solid material was
washed with CH CN (15 mL). The filtrate was evapo-
3
rated and the resulting crude material was either recrys-
2
2
tallized from EtOH/H O or subjected to column
1
999, 29, 2741–2746.
2
6. Mohammadpoor-Baltork, I.; Tangestaninejad, S.; Aliyan,
chromatography to afford the pure product (Table 1).