Mendeleev Commun., 2006, 16(1), 55–56
Solid-state conversion of 1,1-diacetates with N,N'-dibromo-
N,N'-1,2-ethanediylbis(p-toluenesulfonamide) to aldehydes
a
a
a
b
Ramin Ghorbani-Vaghei,* Safar-Ali Akbari, Mohammad A. Zolfigol, BiBi Fatemeh Mirjalili and
Abdolhamid Bamoniric
a
Department of Chemistry, Faculty of Science, Bu-Ali Sina University, 65174 Hamadan, Iran.
Fax: +98 811 827 2404; e-mail: ghorbani@basu.ac.ir
b
Department of Chemistry, Faculty of Science, Yazd University, 89195-741 Yazd, Iran.
Fax: +98 351 821 0644
c
Department of Chemistry, Faculty of Science, Kashan University, 51167 Kashan, Iran.
Fax: +98 361 555 2930
DOI: 10.1070/MC2006v016n01ABEH002200
N,N'-Dibromo-N,N'-1,2-ethanediylbis(p-toluenesulfonamide) can be used for the solid-state conversion of 1,1-diacetates to aldehydes
in excellent yields.
1
,1-Diacylals are of considerable interest because they are stable
Table 1 Deprotection of acylals with BNBTS in a solid state (reagent/
1–6
under neutral and basic conditions. They are important building
blocks for the synthesis of dienes in the Diels–Alder reac-
tion. Therefore, the regeneration of carbonyl compounds from
substrate = 1:1).
7
Time/ Yield
Producta
Entry
R
min
(%)
8
–19
1
,1-diacetates is an important reaction in organic chemistry.
9
,13,15
16,18
1
2
3
4
5
m-NO C H
4
m-Nitrobenzaldehyde
p-Nitrobenzaldehyde
o-Acetoxybenzaldehyde
p-Acetoxybenzaldehyde
p-Acetoxy-m-
methoxybenzaldehyde
o-Chlorobenzaldehyde
Isopropanal
3
4.5
2
1.5
1.5
94
92
98
98
97
However, these methods involve the use of toxic reagents,
long reaction times,
and metals.
N,N'-1,2-ethanediylbis(p-toluenesulfonamide) (BNBTS)
the deprotection of 1,1-diacylals.
2
6
9
,11,16
17
p-NO C H
solvents, microwave irradiation
2
6
4
9,10,13,15
o-AcOC6H4
Therefore, we studied the use of N,N'-dibromo-
p-AcOC H
2
0–23
6
4
for
p-AcO-m-
MeOC H
6
3
6
7
8
9
o-ClC H
Pr
4
2
4
4
92
90
96
90
6
4
Me
Br
i
PhCH=CH
MeCH=CH
Cinnamaldehyde
Crotonaldehyde
N
CH2 2
S
aProducts were characterised by their physical constants, comparison with
authentic samples and IR spectra
O
O
BNBTS
+
It is likely that this reagent releases Br in situ, which can act
1
,1-Diacetates were converted to aldehydes without over-
as an electrophilic species.2
0–23
oxidation to carboxylic acids using BNBTS in a solid state
Scheme 1).
Note that esters, isolated double bonds and silyl ethers did
not react with this reagent. This procedure shows considerable
selectivity between acylal with ester, isolated double bond and
(
Me
Br
N
OAc
R
OAc
OAc
O
H
H2O
solid state,
room temperatre
S
CH2 2
OAc
O
O
O N
2
O N
2
Me
BNBTS
94%
H
N
O
solid state,
room temperature
R
2AcOBr
Br
OH
S
CH2 2
H
O
O
Scheme 1
0
9
%
BNBTS, which can be prepared easily, is stable in atmo-
OAc
OAc
O
spheric conditions for two months. After completing the reaction,
the sulfonamide can be recovered and reused many times without
decreasing the yield.
Various acylals were converted to aldehydes in the presence
of BNBTS in a solid state (Table 1). Furthermore, functional
H
O N
O N
2
2
BNBTS
4%
solid state,
room temperature
†
groups such as chloro, methoxy, acetoxy and nitro were inert to
this reagent and no by-product formation was observed.
CH CH O–SiMe
CH CH OH
2 2
2
2
3
0
%
OAc
OAc
O
H
Scheme 3
†
General procedure for deprotection of acylals with N,N'-dibromo-
N,N'-1,2-ethanediylbis(p-toluenesulfonamide): acylals (0.5 mmol), BNBTS
(0.5 mmol) and a few drops of water were added to a mortar and the
mixture was pulverised with a pestle. A spontaneous reaction took place
[1.5–4.5 min, Table 1, monitored by TLC (9:1, carbon tetrachloride/
acetone)]. After completion of the reaction, CCl4 (10 ml) was added,
and insoluble sulfonamide 1 was removed by filtration. The organic phase
O N
2
O N
2
BNBTS
94%
solid state,
room temperature
O
O
OMe
OH
was washed with H O (10 ml) and dried (MgSO ). After the removal of
0
%
2
4
Scheme 2
the solvent in a vacuum, the product was obtained in 90–98% yield.
Mendeleev Commun. 2006 55