A versatile and practical synthesis of 1,1-diacetates from aldehydes catalyzed by cyanuric chloride

Article abstract of DOI:10.1002/jccs.200700069

Structurally diverse aldehydes are successfully converted into 1,1-diacetates with acetic anhydride using cyanuric chloride as a mild, convenient and inexpensive catalyst under solvent-free conditions. The noteworthy features of the present system are shorter reaction times, and mild and solvent-free conditions. Furthermore, it offers chemoselective protection of aldehydes.

Full text of DOI:10.1002/jccs.200700069

Journal of the Chinese Chemical Society, 2007, 54, 489-492
489
A Versatile and Practical Synthesis of 1,1-Diacetates from Aldehydes
Catalyzed by Cyanuric Chloride
Babasaheb P. Bandgar,* Neeta S. Joshi and Vinod T. Kamble
Organic Chemistry Research Laboratory, School of Chemical Sciences,
Swami Ramanand Teerth Marathwada Univ., Nanded–431606, Maharashtra, India
Structurally diverse aldehydes are successfully converted into 1,1-diacetates with acetic anhydride
using cyanuric chloride as a mild, convenient and inexpensive catalyst under solvent-free conditions. The
noteworthy features of the present system are shorter reaction times, and mild and solvent-free conditions.
Furthermore, it offers chemoselective protection of aldehydes.
Keywords: Cyanuric chloride; Protection; 1,1-Diacetates; Aldehydes; Ketones.
INTRODUCTION
During multi-step synthesis, the protection of the car-
cient protocol for chemoselective protection of aldehydes
to 1,1-diacetates using a catalytic amount of cyanuric chlo-
ride (2 mol%) under solvent-free conditions (Scheme I).
bonyl group is widely achieved by the formation of 1,1-di-
acetates.1 These substrates are important because of their
application as precursors for the synthesis of 1-acetoxy-
dienes, valuable synthetic intermediates for Diels-Alder
cycloaddition reactions. The relative acid stability of 1,1-
diacetates is another interesting feature in the field of pro-
tection-deprotection chemistry.2 In general, the synthesis
of 1,1-diacetates was achieved under the catalysis of strong
protic acids,3 Lewis acids4 and solid catalysis.5 Very recently,
LiOTf,6 Fe2(SO4)3.xH2O,7 Zn(BF4)2,8 Cu(BF4)2.xH2O,9
and Bi(NO3)3.5H2O10 have also been used for this transfor-
mation. However, these methods have not been entirely sat-
isfactory because the use of conventional Bronsted or
Lewis acid catalysts as well as excess organic solvents usu-
ally involves the disadvantages of corrosiveness and te-
dious work-up. Therefore, a practical and more efficient al-
ternative using a mild and inexpensive reagent is still of in-
terest.
Scheme I
R = alkyl, aryl
RESULTS AND DISCUSSION
We first examined the acylation of benzaldehyde us-
ing Ac2O in the absence of cyanuric chloride. The reaction
was sluggish and no corresponding 1,1-diacetate was
formed even after 24 h. However, in the presence of 2
mol% cyanuric chloride, the reaction progressed smoothly
with benzaldehyde at room temperature to afford excellent
yield of the corresponding 1,1-diacetate (Table 1 entry 4).
Likewise we have applied this protocol for the protection of
aliphatic, aromatic and heterocyclic aldehyde and the re-
sults are summarized in Table 1. Both activated and deacti-
vated aromatic aldehydes were converted to 1,1-diacetates.
The tolerances of various functional groups have been ex-
amined by reacting the substrates with chloro, fluoro, meth-
yl, methoxy, cyano and nitro groups, and the reaction con-
ditions are compatible with these functional groups. Acid
sensitive functional groups such as furfuraldehyde and
Over the last few years, there has been a considerable
growth in interest in the use of 2,4,6-trichloro-1,3,5-tri-
azene or its derivatives in organic synthesis.11 Recent
results from our laboratory have shown that simple and
readily available 2,4,6-trichloro-1,3,5-triazine (cyanuric
chloride) can assist some important organic reactions.11n-p
This prompted us to explore the catalytic activity of cya-
nuric chloride for the synthesis of 1,1-diacetates. In this
communication we wish to disclose a new, mild, and effi-
* Corresponding author. Fax: +091-2462-229245; E-mail: bandgar_bp@yahoo.com

490 J. Chin. Chem. Soc., Vol. 54, No. 2, 2007
Bandgar et al.
yields (Table 1, entries 17-19). This protocol was then ap-
plied to protect naphthaldehydes. The yields of the corre-
sponding 1,1-diacetates of naphthaldehydes (Table 1, en-
tries 12-13) are good, although the time required for the
completion of the reaction was longer compared to other al-
dehydes. This transformation was achieved in the presence
of several acid-sensitive protecting groups such as o-allyl,
methylenedioxy, t-butyl diethyl silyl and O-Ph under the
present reaction conditions (Table 1, entries 20-23).
As aldehydes are converted faster than ketones, this
procedure affords chemoselective protection of aldehydes
in the presence of ketones (Scheme II).
Table 1. Cyanuric chloride catalyzed synthesis of 1,1-diacetates
Time
Yielda,b
(%)
Entry
Substrate
n-C3H7CHO
(min.)
1
30
30
40
05
10
10
10
10
05
15
15
20
25
25
30
45
89
88
89
98
98
95
92
93
98
98
97
90
91
90
86
89
2
n-C5H11CHO
3
n-C7H15CHO
4
C6H5CHO
5
4-ClC6H4CHO
6
4-FC6H4CHO
7
4-MeC6H4CHO
4-OMeC6H4CHO
4-CNC6H4CHO
4-NO2C6H4CHO
3-NO2C6H4CHO
1-Naphthaldehyde
2-Naphthaldehyde
9-Anthraldehyde
Furfuraldehyde
Thiophene-2-
8
9
10
11
12
13
14
15
16
Although various methods have been reported for this
conversion, most of them require long reaction times,3a-c,4a
expensive catalysts,6,7,9,10 are not readily available and need
to be prepared catalysts.4e,6 In contrast cyanuric chloride is
a mild, inexpensive and commercially available reagent
and affords the desired products in a short reaction time.
In conclusion, cyanuric chloride catalyzed procedure
provides a highly efficient methodology for the conversion
of aldehydes to the corresponding 1,1-diacetates. The im-
portant features of the present method are chemoselective
protection of aldehydes in the presence of ketones, high
yields, mild reaction conditions compatible with acid sen-
sitive substrates, cost efficiency, and mild and solvent-free
conditions.
carboxaldehyde
Ph-CH=CH-CHO
CH3CH=CH-CHO
CH2=CHCHO
17
18
19
20
21
22
23
30
30
30
10
15
20
25
95
92
93
91
92
94
90
3(O-allyl)C6H4CHO
3,4-(O-CH2O)C6H3CHO
4-(OTBDMS)C6H4CHO
4-(OPh)C6H4CHO
a Refers to yields of pure isolated products.
b Products are characterized by spectral data (IR, 1H NMR).
thiophene-2-carboxaldehyde (Table 1, entries 15, 16) are
also protected as 1,1-diacetates in good yields without for-
mation of by-products which are normally encountered in
acidic conditions. The protocol is equally efficient in pro-
tecting a,b-unsaturated aldehydes as 1,1-diacetates in good
EXPERIMENTAL SECTION
All reactions were carried out in oven-dried flasks.
All chemicals were of analytical grade. IR spectra were re-
Scheme II
H
CHO
C(OAc)2
(2 mol%)
AC2O, Cyanuric chloride
rt, neat, 30 min.
COCH3
CHO
COCH3
93%
COCH3
HC(OAc)2
+
COCH3
(2 mol%)
AC2O, Cyanuric chloride
rt, neat, 15 min.
+
Br
Br
94%
98%

A Synthesis of 1,1-Diacetates from Aldehydes with (CNCl)3
J. Chin. Chem. Soc., Vol. 54, No. 2, 2007 491
1
corded on a Bomem MB104 FT-IR spectrometer and H
4.60; N, 5.96.
NMR spectra were recorded on an AC 300 F spectrometer
(300 MHz).
(10) 4-Nitrobenzylidenediacetate mp. 124 °C; IR
(CHCl3): nmax 1730, 1500, 1320, 1205, 985 cm-1; 1H NMR:
d 8.28 (m, 2H), 7.75 (s, 1H), 7.75 (d, J = 7.9 Hz, 2H), 2.15
(s, 6H). Anal calcd for C11H11O6N (253.209): C, 52.17; H,
4.378; N, 5.52. Found: C, 52.05; H, 4.37; N, 5.20.
In a typical procedure, a mixture of benzaldehyde (5
mmol), Ac2O (15 mmol) and cyanuric chloride (0.02 mmol)
was stirred at room temperature for 5 min. After comple-
tion of the reaction, as indicated by TLC, diethylether was
added and the mixture was washed successively with 1 M
NaOH solution (2 ´ 20 mL), brine (10 mL) and H2O (10
mL). The organic layer was separated and dried (Na2SO4).
Evaporation of the solvent under reduced pressure furnished
almost pure product. Further purification was achieved by
column chromatography (silica gel, ethylacetate: hexane =
1:9) or recrystalization from EOAc:hexane to afford pure
product in good to excellent yields (Table 1).
(11) 3-Nitrobenzylidenediacetate, mp. 128 °C. IR
(CHCl3): nmax 1735, 1505, 1325, 1210, 990 cm-1; 1H NMR:
d 8.29 (m, 2H), 7.70 (s, 1H), 7.71 (d, J = 7.9 Hz, 2H), 2.10
(s, 6H). Anal calcd for C11H11O6N (253.209): C, 52.17; H,
4.378; N, 5.52. Found: C, 52.07; H, 4.30; N, 5.18.
Received May 15, 2006.
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