Acetonyltriphenylphosphonium bromide (ATPB): A versatile reagent for the acylation of alcohols, phenols, thiols and amines and for 1,1-diacylation of aldehydes under solvent-free conditions

Article abstract of DOI:10.1002/ejoc.200500066

A wide variety of alcohols, phenols, amines and thiols may easily be converted into the corresponding acetate derivatives by treatment with acetic anhydride (1.5-2.0 equivalents) in the presence of acetonyltriphenylphosphonium bromide (ATPB; 5 mol %) in good yields at room temperature. With the same precatalyst, both aliphatic and aromatic aldehydes can also be transformed into the corresponding gemdiacetates under reflux conditions.

Full text of DOI:10.1002/ejoc.200500066

FULL PAPER
Acetonyltriphenylphosphonium Bromide (ATPB): A Versatile Reagent for the
Acylation of Alcohols, Phenols, Thiols and Amines and for 1,1-Diacylation of
Aldehydes under Solvent-Free Conditions
[a]
[a]
[a]
Abu T. Khan,* Lokman H. Choudhury, and Subrata Ghosh
Dedicated to Professor K. C. Majumdar[‡]
Keywords: Acylations / Alcohols / Phenols / Amines / Thiols / Acetonyltriphenylphosphonium bromide
A wide variety of alcohols, phenols, amines and thiols may
easily be converted into the corresponding acetate deriva-
tives by treatment with acetic anhydride (1.5–2.0 equiva-
lents) in the presence of acetonyltriphenylphosphonium bro-
mide (ATPB; 5 mol%) in good yields at room temperature.
With the same precatalyst, both aliphatic and aromatic alde-
hydes can also be transformed into the corresponding gem-
diacetates under reflux conditions.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Introduction
reagents can be highly expensive or require longer reaction
times and extremely dry reaction conditions. Although
there are numerous known literature methods through
which to obtain good yields of acetylated products, there is
still a need for mild and effective catalysts applicable for
acetylation reactions for a wide variety of substrates. As a
part of our ongoing research project to develop newer syn-
thetic methodologies, particularly in protection and depro-
The acylation of alcohols and phenols, amines and thiols
is one of the most useful transformations in organic synthe-
sis.[ Of these, the conversion of a hydroxy group into the
corresponding acetate is important due to its ease of intro-
duction, stability under mild acidic reaction conditions and
ease of removal by mild alkaline hydrolysis. The acylation
of alcohols, phenols or amines is usually performed with
acetic anhydride in the presence of amine bases such as tri-
ethylamine or pyridine, or pyridine together with 4-(dimeth-
ylamino)pyridine (DMAP), which acts as a cocatalyst, or
1]
[
19]
tection chemistry,
we speculated that acetonyltriphenyl-
phosphonium bromide (ATPB) might be a useful, effective
and versatile precatalyst for acylation reactions. So far, ace-
tonyltriphenylphosphonium bromide (ATPB) has been uti-
4
-pyrrolidinopyridine (PPY).[2] It is also possible to use tri-
butylphosphane (Bu P) as a less basic catalyst for acylation
[
20a]
lized mainly as a Wittig salt,
for the tetrahydropyranyl-
3
[20b]
ation/depyranylation of alcohols,
and for the cyclo-
[
3]
reactions, particularly for base-sensitive substrates. Vari-
[
20c]
trimerization of aldehydes.
Very recently, we have dem-
[
4]
[5]
[6]
ous metal salts such as CoCl , ZnCl2, RuCl3, TiCl4–
2
onstrated the utility of ATPB for selective deprotection of
[
7]
[8]
[9]
[10]
AgClO4, LiClO4, Mg(ClO ) , Zn(ClO ) ·6H O and
4 2
11]
4 2
[12]
2
[19c]
tert-butyldimethylsilyl (TBS) ethers.
Here we report the
[
[13]
some triflates such as Sc(OTf) , Me SiOTf, In(OTf)3,
3
3
acetylation of alcohols, phenols, amines and thiols with ace-
tic anhydride in the presence of catalytic amounts of aceto-
nyltriphenylphosphonium bromide (ATPB) under solvent
free-conditions, as shown in Scheme 1.
[
14]
[15]
[16]
Cu(OTf)2,
Ce(OTf)3
and Bi(OTf)3
have also been
employed for acylation reactions in recent years. Very
recently, it was also shown that I can be employed as a
2
catalyst for the acetylation of alcohols under solvent-free
[
17]
[8–10]
conditions. Though perchlorates
have been observed
to be effective catalysts for this transformation, they have
some serious drawbacks, such as some of them being highly
[
18]
explosive.
In addition, Mg(ClO ) has to be anhydrous
4 2
[9]
in order to provide better yields. Other methods based on
[
11–16]
[6]
triflates
or RuCl3 also have some disadvantages: the
[
[
a] Department of Chemistry, Indian Institute of Technology Gu-
wahati,
Guwahati 781039, India
‡] A. T. K. thanks Professor K. C. Majumdar for his constant
encouragement as mentor.
Scheme 1.
2782
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200500066
Eur. J. Org. Chem. 2005, 2782–2787

Acylations under Solvent-Free Conditions
FULL PAPER
Results and Discussion
Table 1. Acetylation of alcohols, phenols, amines and thiols at
room temperature in the presence of acetonyltriphenylphosphon-
ium bromide as precatalyst.
For this study we first prepared the reagent acetonyltri-
phenylphosphonium bromide by the literature pro-
[
20a]
cedure.
We then attempted the acylation of cetyl alcohol
(1a) with acetic anhydride in the presence of acetonyltri-
phenylphosphonium bromide (5 mol%) at room tempera-
ture (Table 1). The reaction was complete within 25 min,
and the pure acetate derivative of cetyl alcohol (2a) was
obtained in 96% yield after chromatographic separation.
We next examined benzoyl-, tert-butyldimethylsilyl- and
tert-butyldiphenylsilyl-protected alcohols 1b–d and found
that they were smoothly converted into the corresponding
acetates 2b–d in good yields under identical reaction condi-
tions, without the protecting groups being affected. Like-
wise, various benzylic alcohols (1e–g), secondary alcohols
(1h–k), allyl alcohol (1l) and butyne-1,4-diol (1m) were con-
verted in similar manner into the corresponding acetate de-
rivatives 2e–m in very good yields. It is interesting to men-
tion that neither alkyl bromide formation nor HBr addition
at double bonds or even triple bonds took place under the
experimental conditions. It had been observed that the TBS
group was unlikely to survive acetylation with use of Ce-
[
15]
(OTf)3,
while our procedure offered the advantage that
the TBS group was unaffected under the reaction condi-
tions. It is also worthwhile to point out that our procedure
is more efficient: the acetylation of cholesterol (entry 1k),
for example, was completed much more quickly than in the
recently reported procedure.[
15]
Notably, chiral alcohols
such as menthol (entry 1j) were easily acetylated in high
yields and with complete retention of optical activity. Re-
markably, an isopropylidene-protected alcohol 1n could
also be acetylated under identical conditions without cleav-
age of the isopropylidene group. A tertiary alcohol (1o) and
a sterically hindered tertiary alcohol, adamentanol (1p),
were also smoothly converted into the corresponding ace-
tate derivatives 2o and 2p, respectively, without any diffi-
culty. We have noticed that this method is more efficient
than the ruthenium(iii) chloride method[ in terms of reac-
tion times, particularly for the preparation of 2p.
6]
We next investigated whether or not the same reagent can
be employed for acetylation of phenolic compounds. By the
same procedure, various phenolic compounds 1q–s were
easily transformed into the corresponding acetate deriva-
tives 2q–s. Again, we observed that 4-nitrophenol (entry 1r)
and 2-naphthol (entry 1s) were converted into the corre-
sponding acetate derivatives much more quickly than in the
recently reported procedure.[ We next turned our attention
to whether or not our methodology could be extended fur-
ther, for acetylation of carbohydrates and nucleosides. We
found that various carbohydrate molecules such as 1t–v and
thymidine (1w) were converted into the corresponding ace-
tate derivatives 2t–w in good yields under similar reaction
conditions. Importantly, a thio group and a methoxy group
at the anomeric position were unaffected under the experi-
mental conditions. The reaction times and yields of the
products are summarized in Table 1. Interestingly, it is also
possible for a primary OH group to be acetylated chemose-
6]
Eur. J. Org. Chem. 2005, 2782–2787
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. T. Khan, L. H. Choudhury, S. Ghosh
FULL PAPER
Table 1. (Continued)
Scheme 2.
When an aliphatic aldehyde was treated with acetic anhy-
dride in the presence of ATPB (10 mol%) at room tempera-
ture, the reaction was very sluggish and the yield was low.
On heating at reflux, however, the same reaction mixture
provided the corresponding gem-diacetate derivative in
good yield by our procedure, more activation energy for the
formation of 1,1-diacetates having been provided. Various
aliphatic and aromatic aldehydes were smoothly converted
into the corresponding gem-diacetates in good yields in the
presence of the same precatalyst under reflux conditions;
the reaction times and yields of the 1,1-diacetates are listed
in Table 2. The products were characterized by checking of
1
a] All the acetylated compounds were characterized by IR, 1
their melting points and by their IR and H NMR spectra,
[
H
NMR and elemental analyses. [b] Isolated yield. [c] The data for and elemental analyses, as well as by comparison of the
the acetates were also compared with those for the authentic com- compounds’ data with the reported data. It is important to
pounds. [d] Acetic anhydride (3–5 equivalents) was used instead of
mention that neither α-bromination nor cyclotrimerization
under the experimental conditions were noticed. This
method is relatively harsher than previously reported meth-
1.5–2.0 equivalent. [e] Acetic anhydride (1 equivalent) was used.
Table 2. Formation of gem-diacetates from the corresponding alde-
hydes in the presence of ATPB (10 mol%) as precatalyst under sol-
vent-free conditions.
lectively (entry 1x) under similar reaction conditions. By
our procedure, both aliphatic and aromatic amines (entry
1y–z), as well as thiols (entry 1aЈ and 1bЈ), were trans-
formed into the corresponding acetate derivatives 2y–bЈ in
good yields with the same precatalyst.
We next turned our attention to whether the same precat-
alyst would be useful for the 1,1-diacetylation of aldehydes.
The formation of geminal diesters from the corresponding
aldehyde compounds is an important organic transforma-
tion because they serve as building blocks for asymmetric
[
25]
[26]
allylic alkylation
and Diels–Alder reactions.
More-
over, acylals are commonly used as protecting groups for
aldehydes because they are stable under neutral and basic
[
27]
conditions.
The formation of a 1,1-diacetate is usually
achieved by treatment of an aldehyde compound with acetic
anhydride in the presence of an acid or Lewis acid, acting as
a catalyst. The literature includes several reported methods
[28]
employing various reagents such as LiOTf, ceric ammo-
[
29]
[30]
[31]
[32]
[38]
nium nitrate,
InCl3,
H NSO H,
LiBF4,
2
3
[
33]
[34]
[35]
[36]
[37]
H SO , PCl3, NBS, I , TMSCl·NaI, FeCl ,
and Bi(NO ) ·5H O for similar transformations.
2
4
2
3
[39]
Some
3
3
2
metal triflates (e.g., Cu(OTf)2[ and Sc(OTf)3 ) have also
been utilized as catalysts for the preparation of 1,1-diacetate
derivatives from the corresponding aldehydes. Some of
these methods have certain drawbacks, such as require-
ments for longer reaction times or use of expensive reagents,
and sometimes fail to provide acylals from aliphatic alde-
hydes or aromatic aldehydes possessing electron-donating
groups in the aromatic ring,[ so there would be scope for
an alternative method. With our precatalyst, various alde-
hydes can be converted smoothly into the corresponding
40]
[41]
39]
1
[
a] All the products were characterized by melting point, IR, H
1,1-diacetates, as shown in Scheme 2.
NMR and elemental analysis. [b] Isolated yield.
2784
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 2782–2787

Acylations under Solvent-Free Conditions
FULL PAPER
ods for the formation of gem-diacetates, but both aliphatic General Procedure for 1,1-Diacetylation of Aldehydes: A mixture of
aldehyde (1 mmol) and acetic anhydride (4 mmol) was placed in a
and aromatic aldehydes can nevertheless be converted into
the corresponding diacetates in good yields. Like a pre-
viously reported method,[39] this procedure did not provide
any 1,1-diacetates from ketones under identical reaction
conditions: when acetophenone, for example, was treated
with acetic anhydride in the presence of the same precata-
lyst under reflux conditions, it did not give the correspond-
ing 1,1-diacetate derivative.
10 mL round-bottomed flask fitted with a reflux condenser. The
acetonyltriphenylphosphonium bromide precatalyst (0.1 mmol)
was then added and the mixture was stirred under reflux condi-
tions. After completion of the reaction as monitored by TLC, it was
quenched with a saturated solution of sodium hydrogencarbonate
(
(
2 mL) and the mixture was extracted with ethyl acetate
20 mL×2). The combined organic layer was dried over anhydrous
sodium sulfate and was concentrated in vacuo. Finally, the crude
The formation of the product can be explained as fol- residue was passed through a silica gel column to provide the de-
lows. We believe that HBr is generated in the reaction me- sired 1,1-diacetate derivatives.
dium from the reaction between acetonyltriphenylphos-
phonium bromide and alcohol, and that this catalyses the
acetylation of the alcohols to provide the corresponding 1.48–1.62 (m, 2 H, –CH ), 2.04 (s, 3 H, –COCH ), 4.04 (t, J =
1
Compound 2a: Colourless liquid. H NMR (400 MHz, CDCl
=
3
): δ
),
0.88 (t, J = 7.2 Hz, 3 H, –CH ), 1.22–1.36 (m, 26 H, –CH
3
2
2
3
acetates. However, the corresponding reaction failed when 7.2 Hz, 2 H, –OCH ) ppm. IR (neat): ν˜ = 2919, 2858, 1747 (CO),
2
–
1
carried out with benzyltriphenylphosphonium bromide in- 1465, 1368, 1235, 1045 cm . C18
36 2
H O (284.48): calcd. C 76.00, H
2.75; found C 75.82, H 12.69%.
1
stead of acetonyltriphenylphosphonium bromide, indicating
that ATPB generates HBr much more easily than the other
alkylphosphonium bromide.
1
Compound 2b: Colourless liquid. H NMR (400 MHz, CDCl
1.30–1.50 (m, 8 H, –CH ), 1.60–1.70 (m, 2 H, –CH ), 1.72–1.80
q, 2 H, –CH ), 2.04 (s, 3 H, –COCH ), 4.05 (t, J = 7.2 Hz, 2 H,
), 4.32 (t, J = 6.8 Hz, 2 H, –OCH ), 7.44 (t, J = 8.0 Hz, 2
H, ArH), 7.55 (t, J = 8.0 Hz, 1 H, ArH), 8.04 (d, J = 7.6 Hz, 2 H,
ArH) ppm. IR (neat): ν˜ = 3063, 2930, 2858, 1731 (CO), 1593, 1455,
3
): δ
=
(
2
2
2
3
–OCH
2
2
Conclusions
In conclusion, we have demonstrated a new, efficient and
chemoselective procedure for the acetylation of alcohols,
phenols, amines and thiols by use of a catalytic amount
of acetonyltriphenylphosphonium bromide as precatalyst at
room temperature under very mild conditions. In addition,
both aliphatic and aromatic aldehydes can be converted
into gem-diacetates by employing the same catalyst under
reflux conditions. The significant features of this method
include its ease of operation, high efficiency, mild condi-
tions and chemoselectivity, which may prove widely useful
–
1
1
6
378, 1271, 1240, 1112, 1035 cm . C17
9.84, H 8.27; found C 69.70, H 8.21%.
24 4
H O (292.37): calcd. C
1
Compound 2c: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ
], 0.85 [s, 9 H,
), 1.44–1.55 (m, 2 H, –CH ),
), 2.00 (s, 3 H, –COCH ), 3.54 (t, J =
), 4.00 (t, J = 6.8 Hz, 2 H, –OCH
): δ = –5.3, 0.0, 18.3, 21.0, 25.7, 25.8, 26.0
3C), 29.2, 29.3, 32.3, 32.8, 63.2, 64.6, 171.2 ppm. IR (neat): ν˜ =
=
–0.01 [s, 3 H, –Si(CH
SiC(CH ], 1.26–1.40 (m, 8 H, –CH
.57–1.61 (m, 2 H, –CH
.8 Hz, 2 H, –OCH
3 2 3 2
) ], 0.00 [s, 3 H, –Si(CH )
–
1
6
3
)
3
2
2
2
3
1
3
2
2
) ppm.
C
NMR (100 MHz, CDCl
(
3
3056, 2920, 2848, 1740 (CO), 1475, 1433, 1373, 1245, 1112,
–
1
in organic synthesis. Moreover, a wide variety of other pro- 1035 cm . C H O Si (302.53): calcd. C 63.52, H 11.33; found C
1
6
34
3
tecting groups, such as benzyl, benzoyl, TBS, TBDPS and 63.34, H 11.24%.
isopropylidene, survived under the experimental conditions,
as did methoxy and thio groups at anomeric positions.
1
Compound 2d: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ
), 1.52–1.68
), 3.65 (t, J = 6.4 Hz, 2 H,
), 4.05 (t, J = 6.8 Hz, 2 H, –OCH ), 7.36–7.42 (m, 6 H,
=
1.04 [s, 9 H, –SiC(CH
3 3 2
) ], 1.20–1.40 (m, 8 H, –CH
m, 4 H, –CH ), 2.01 (s, 3 H, –COCH
(
2
3
–OCH
2
2
Experimental Section
ArH), 7.66–7.68 (dd, J = 1.6, J = 7.6 Hz, 4 H, ArH) ppm. IR
(
1
neat): ν˜ = 3058, 2925, 2848, 1742 (CO), 1475, 1434, 1373, 1245,
Melting points were recorded on a Büchi B-545 melting point appa-
ratus and were uncorrected. IR spectra were recorded in KBr or
–
1
112, 1035 cm . C26
H
38
O
3
Si (426.67): calcd. C 73.19, H 8.98;
1
found C 73.01, H 8.91%.
neat on a Nicolet Impact 410 spectrophotometer. H NMR spectra
and 13C NMR spectra were recorded on a Jeol 400-MHz spectrom-
1
Compound 2g: Colourless liquid. H NMR (400 MHz, CDCl
=
–
7
2
3
): δ
], 2.08 (s, 3 H,
), 6.81 (d, J = 8.0 Hz, 2 H, ArH),
3
eter in CDCl with TMS as internal reference. Elemental analyses
0.19 [s, 6 H, Si(CH
3 2 3 3
) ], 0.98 [s, 9 H, –SiC(CH )
were carried out with a Perkin–Elmer 2400 automatic carbon, hy-
drogen, nitrogen and sulfur analyzer. Column chromatographic
separations were carried out on SRL silica gel (60–120 mesh).
COCH ), 5.02 (s, 2 H, –OCH
3
2
.22 (d, J = 8.0 Hz, 2 H, ArH) ppm. IR (neat): ν˜ = 2954, 2930,
–1
888, 2859, 1747 (CO), 1610, 1521, 1237, 1229, 913 cm .
General Procedure for Acetylation of Alcohols or Phenols or Amines
and Thiols: Acetonyltriphenylphosphonium bromide (0.05 mmol)
was added to a mixture of the alcohol, or phenol, or amine or thiol
C
15
H
24SiO
3
(280.44): calcd. C 64.24, H 8.63; found C 64.59, H
8.55%.
1
Compound 2h: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ
), 2.07
), 5.66 (t, J = 7.2 Hz, 1 H, –CHOAc), 7.20–7.37
m, 5 H, ArH) ppm. IR (neat): ν˜ = 3063, 3022, 2976, 2925, 2879,
(1 mmol) and acetic anhydride (1.5–2.0 mmol) and the mixture was
=
0.87 (t, J = 7.2 Hz, 3 H, –CH
3 2
), 1.81–1.95 (m, 2 H, –CH
stirred at room temperature for ca. 0.5–3.5 h. After complete disap-
pearance of the starting material as monitored by TLC, the mixture
was quenched with a saturated hydrogencarbonate solution (2 mL).
Finally, the reaction mixture was extracted with ethyl acetate
(s, 3 H, –COCH
3
(
–
1
14 2
1742 (CO), 1491, 1460, 1378, 1250, 1055 cm . C11H O (178.23):
calcd. C 74.13, H 7.92; found C 74.01, H 7.85%.
(20 mL×3). The combined organic extract was washed with water
and dried over anhydrous sodium sulfate. After removal of the or-
ganic solvent in a rotary evaporator, the crude residue was sub-
jected to silica gel column to isolate the desired pure acetate.
Compound 2i: Colourless gummy liquid. 1H NMR (400 MHz,
CDCl ): δ = 2.15 (s, 3 H, –COCH ), 6.88 (s, 1 H, –CHOAc), 7.32–
7.34 (m, 10 H, ArH) ppm. IR (neat): ν˜ = 3073, 3037, 2935, 1747
3
3
Eur. J. Org. Chem. 2005, 2782–2787
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2785

A. T. Khan, L. H. Choudhury, S. Ghosh
FULL PAPER
–
1
(CO), 1598, 1496, 1445, 1373, 1235, 1020 cm . C15
H
14
O
2
(226.27): 1.80 (m, 2 H, –CH
CH(OAc) ] ppm. IR (neat): ν˜ = 2930, 2863, 1762, 1465, 1378, 1250,
1214, 1112, 1015, 968 cm . C11
.32; found C 60.89, H 9.27.
2 3
), 2.07 (s, 6 H, 2×COCH ), 6.77 [t, 1 H,
calcd. C 79.62, H 6.24; found C 79.41, H 6.18%.
2
–
1
1
20 4
H O (216.28): calcd. C 61.09, H
Compound 2m: Colourless, low-melting solid. H NMR (400 MHz,
9
CDCl
OCH
156, 1038 cm . C
C 56.19, H 5.85%.
3
): δ = 2.10 (s, 6 H, 2×–COCH
3
), 4.71 (s, 4 H, 2×–
1
2
) ppm. IR (neat): ν˜ = 2949, 1752 (CO), 1435, 1383, 1222,
Compound 4c: Solid, m.p. 84 °C. H NMR (400 MHz, CDCl
3
): δ =
–1
1
8
H
10
O
4
(170.16): calcd. C 56.47, H 5.92; found
2.10 (s, 6 H, 2×COCH
J = 8.8 Hz, 2 H, ArH), 7.61 [s, 1 H, CH(OAc)
= 3063, 2986, 2930, 1762, 1593, 1486, 1378, 1245, 1214, 1076, 1015,
3
), 7.39 (d, J = 8.4 Hz, 2 H, ArH), 7.53 (d,
2
] ppm. IR (KBr): ν˜
1
Compound 2o: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ
),
), 1.62–1.90 (m, 4 H,
) ppm. 13C NMR (100 MHz, CDCl
):
–
1
9
4
68 cm . C11
6.21, H 3.80.
H11BrO
4
(287.10): calcd. C 46.02, H 3.86; found C
=
1
–
0.85 (t, J = 8.0 Hz, 3 H, –CH
.24–1.34 (m, 6 H, –CH ), 1.37 (s, 3 H, –CH
CH ), 1.97 (s, 3 H, –COCH
3 3
), 0.89 (t, J = 7.2 Hz, 3 H, –CH
2
3
1
Compound 4h: Solid, m.p. 85–86 °C. H NMR (400 MHz, CDCl
3
):
2
3
3
δ = 8.13, 14.17, 22.48, 22.72, 23.37 (2C), 30.91, 32.25, 37.81, 85.13,
δ = 2.15 (s, 6 H, 2×COCH
(m, 2 H, ArH) 8.05 (dd, J = 0.8, J = 7.6 Hz, 1 H, ArH), 8.20 [s, 1
H, CH(OAc) ] ppm. IR (KBr): ν˜ = 1771, 1587, 1525, 1454, 1377,
1351, 1244, 1208, 1105, 1075, 1025 cm . C11
3
), 7.57–7.61 (m, 1 H, ArH), 7.67–7.74
1
1
70.18 ppm. IR (neat): ν˜ = 2935, 2873, 1737 (CO), 1465, 1373,
–1
250, 1143, 1025 cm . C11
H
22
O
2
(186.29): calcd. C 70.92, H 11.90;
2
–
1
found C 70.76, H 11.85%.
6
H11NO (253.21):
calcd. C 52.18, H 4.38, N 5.53; found C 51.93, H 4.30, N 5.38.
1
Compound 2t: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ =
), 2.07 (m, 1 H, 4-H), 3.39 (s, 3 H, –OCH ),
.59–3.63 (m, 3 H), 3.82–3.88 (m, 1 H, 5-H), 3.90 (t, J = 9.2 Hz, 1
1
Compound 4j: Solid, m.p. 63–64 °C. H NMR (400 MHz, CDCl
3
):
1
3
.94 (s, 3 H, –COCH
3
3
δ = 2.21 (s, 6 H, 2×COCH
3
), 3.88 (s, 3 H), 3.92 (s, 3 H), 6.88 (d,
J = 8.0 Hz, 1 H, ArH), 7.05 (s, 1 H, ArH), 7.11 (d, J = 8.0 Hz, 1
H, 3-H), 4.01 (dd, J = 2.4, J = 11.4 Hz, 1 H, 6-H), 4.32 (dd, J =
.8 Hz, 1 H, 6Ј-H), 4.47 (d, J = 12.0 Hz, 1 H, –OCHPh), 4.58 (d,
J = 10.8 Hz, 1 H, –OCHPh), 4.60 (d, J = 12.0 Hz, 1 H, –OCHPh),
.66 (d, J = 12.0 Hz, 1 H, –OCHPh), 4.69 (d, J = 3.6 Hz, 1 H, 1-
H), 4.78 (d, J = 12.0 Hz, 1 H, –OCHPh), 4.96 (d, J = 10.8 Hz, 1
H, –OCHPh), 7.22–7.40 (m, 15 H, ArH) ppm. IR (neat): ν˜ = 3032,
1
3
H, ArH), 7.62 [s, 1 H, CH(OAc)
CDCl ): δ = 20.7 (2C), 55.9 (2C), 89.8, 109.6, 111.5, 119.5, 128.0,
49.1, 150.1, 168.7 (2C) ppm. IR (KBr): ν˜ = 2965, 2847, 1751,
2
] ppm. C NMR (100 MHz,
2
3
1
1
4
–
1
602, 1525, 1464, 1387, 1346, 1254, 1208, 1152, 1064, 998 cm .
(268.26): calcd. C 58.21, H 6.01; found C 57.95, H 5.96.
13 16 6
C H O
–1
2
36 7
899, 1742 (CO), 1455, 1363, 1240, 1091, 1055 cm . C31H O
(
520.62): calcd. C 71.52, H 6.97; found C 71.25, H 6.90%.
Acknowledgments
1
Compound 2u: Solid, m.p.: 63 °C. H NMR (400 MHz, CDCl
3
): δ
=
1.32 (t, J = 7.6 Hz, 3 H, –SCH
2
CH
3
), 2.03 (s, 3 H, –COCH ),
3
A. T. K. acknowledges to the Department of Science and Technol-
2
3
1
.64–2.80 (m, 2 H, –SCH CH ), 3.44 (t, J = 9.2 Hz, 1 H), 3.50– ogy (DST), New Delhi for a research grant (Grant No. SP/S1/G-
2
3
.52 (m, 1 H, 5-H), 3.54 (t, J = 9.6 Hz, 1 H), 3.71 (t, J = 8.8 Hz,
H), 4.19 (dd, J = 4.4, J = 11.6 Hz, 1 H, H- 6), 4.33 (dd, J = 1.6,
35/98). L. H. C. is grateful to the CSIR, Govt. of India, and S. G.
to IITG for their research fellowships. We are also grateful to the
Director, IITG for general facilities to carry out our research works.
We are thankful to the referees for their valuable comments and
J = 12.0 Hz, 1 H, 6Ј-H), 4.47 (d, J = 9.6 Hz, 1 H, 1-H), 4.57 (d, J
11.2 Hz, 1 H, –OCHPh), 4.74 (d, J = 10.4 Hz, 1 H, –OCHPh),
=
4
–
1
.85 (d, J = 10.8 Hz, 1 H, –OCHPh), 4.86 (d, J = 10.8 Hz, 1 H, suggestions.
OCHPh), 4.92 (d, J = 10.4 Hz, 1 H, –OCHPh), 4.95 (d, J =
0.8 Hz, 1 H, –OCHPh), 7.26–7.36 (m, 15 H, ArH) ppm. IR (KBr):
[
1] T. W. Greene, P. G. M. Wuts, Protective Groups in Organic syn-
ν˜ = 3063, 3027, 2925, 2868, 1737 (CO), 1455, 1363, 1235,
1
thesis, 3rd ed., John Wiley & Sons, Inc., New York, 1999, pp.
–1
071 cm . C31
H
36
O
6
S (536.68): calcd. C 69.38, H 6.76, S 5.97;
150–160.
found C 69.23, H 6.70, S 5.70%.
[2] G. Hofle, V. Steglich, H. Vorbrueggen, Angew. Chem. Int. Ed.
Eng. 1978, 17, 569–583.
1
Compound 2v: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ =
), 3.40–3.44 (m, 2 H), 3.59 (dd, 1 H), 3.83–
.87 (m, 1 H), 3.97 (t, 1 H), 4.46–4.56 (m, 4 H), 4.62–4.71 (m, 3
[
3] a) E. Vedejs, S. T. Diver, J. Am. Chem. Soc. 1993, 115, 3358–
359; b) E. Vedejs, N. S. Bennet, L. M. Conn, S. T. Diver, M.
Gingras, S. Lin, P. A. Oliver, M. J. Peterson, J. Org. Chem.
993, 58, 7286–7288.
1
3
.83 (s, 3 H, –COCH
3
3
H), 4.82 (d, J = 3.6 Hz, 1 H, 1-H), 4.90 (d, J = 12.0 Hz, 1 H), 5.04
t, J = 8.0 Hz, 1 H), 7.25–7.40 (m, 20 H, ArH) ppm. IR (neat): ν˜
3065, 3030, 2918, 2867, 1748, 1503, 1457, 1376, 1234, 1101,
1
(
[4] J. Iqbal, R. R. Srivastava, J. Org. Chem. 1992, 57, 2001–2007.
[5] R. H. Backer, F. G. Bordwell, Org. Synth. 1955, 3, 141–142.
[6] S. K. De, Tetrahedron Lett. 2004, 45, 2919–2922.
=
–1
1045 cm . C36
H
38
O
7
(582.69): calcd. C 74.20, H 6.57; found C
[
7] M. Miyashita, I. Shiina, S. Miyoshi, T. Mukaiyama, Bull.
Chem. Soc., Jpn. 1993, 66, 1516–1520.
74.01, H 6.60%.
1
Compound 2x: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ
),
), 4.07–4.09 (m, 1 H, –OCH), 4.21(d, J
[8] Y. Nakae, I. Kusaki, T. Sato, Synlett 2001, 1584–1586.
=
3
=
(
1.71 (br.s, 1 H, OH, D
.60–3.64 (m, 2 H, –OCH
5.2 Hz, 2 H, –CH
CO),1424, 1240, 1045, 933 cm . C
9.35, H 5.94; found C 39.10, H 5.86%.
2
O exchangeable), 2.12 (s, 3 H, –COCH
3
[9] G. Bartoli, M. Bosco, R. Dalpozzo, E. Marcantoni, M. Mas-
2
saccesi, S. Rinaldi, L. Sambri, Synlett 2003, 39–42.
Cl) ppm. IR (neat): ν˜ = 3437 (OH), 2960,1737 [10] G. Bartoli, M. Bosco, R. Dalpozzo, E. Marcantoni, M. Mas-
2
–
1
saccesi, L. Sambri, Eur. J. Org. Chem. 2003, 4611–4617.
11] K. Ishihara, M. Kubota, H. Kurihara, H. Yamamoto, J. Org.
Chem. 1996, 61, 4560–4567.
12] P. A. Procopiou, S. P. D. Baugh, S. S. Flack, G. G. A. Inglis, J.
Org. Chem. 1998, 63, 2342–2347.
5 9 3
H ClO (152.62): calcd. C
[
[
3
1
Compound 2bЈ: Colourless liquid. H NMR (400 MHz, CDCl
0.88 (t, J = 7.2 Hz, 3 H, –CH ), 1.20–1.40 (m, 18 H, –CH
.45–1.60 (m, 2 H, –CH ), 2.32 (s, 3 H, –COCH ), 2.86 (t, J =
.6 Hz, 2 H, –SCH ) ppm. IR (neat): ν˜ = 2940, 2853, 1692 (CO),
460, 1342, 1132, 948 cm . C14
3
): δ
=
3
2
),
1
7
1
1
2
3
[13] K. K. Chauhan, C. G. Frost, I. Love, D. Waite, Synlett 1999,
743–1744.
[14] a) P. Saravanan, V. K. Singh, Tetrahedron Lett. 1999, 40, 2611–
614; b) K. L. Chandra, P. Saravanan, R. K. Singh, V. K.
1
2
–1
H
28SO (244.44): calcd. C 68.79, H
2
1.55, S 13.12; found C 68.49, H 11.49, S 12.97%.
Singh, Tetrahedron 2002, 58, 1369–1374.
1
Compound 4a: Colourless liquid. H NMR (400 MHz, CDCl
3
): δ
[15] R. Dalpozzo, A. D. Nino, L. Maiuolo, A. Procopio, M. Nardi,
G. Bartoli, R. Romeo, Tetrahedron Lett. 2003, 44, 5621–5624.
=
0.98 (t, J = 6.8 Hz, 3 H, CH
3
), 1.22–1.40 (m, 8 H, –CH
2
), 1.66–
2786
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 2782–2787

Acylations under Solvent-Free Conditions
FULL PAPER
[
16] A. Orita, C. Tanahashi, A. Kakuda, J. Otera, Angew. Chem.
[27] T. W. Greene, P. G. M. Wuts, Protective Groups in Organic syn-
thesis, 3rd ed., John Wiley & Sons, Inc., New York, 1999, pp.
306–307.
Int. Ed. 2000, 39, 2877–2879.
[
[
17] P. Phukan, Tetrahedron Lett. 2004, 45, 4785–4787.
18] J. C. Schumacher, Perchlorates––Their Properties, Manufacture
and Use, in: ACS Monograph Series, Reinhold, New York,
[28]
[
[
B. Karimi, J. Maleki, J. Org. Chem. 2003, 68, 4951–4954.
29] S. C. Roy, B. Banerjee, Synlett 2002, 1677–1678.
30] J. S. Yadav, B. V. S. Reddy, C. Srinivas, Synth. Commun. 2002,
2, 2169–2174.
31] T.-S. Jin, G. Sun, Y.-W. Li, T.-S. Li, Green Chem. 2002, 4, 255–
56.
1
996.
[
19] a) A. T. Khan, E. Mondal, B. M. Borah, S. Ghosh, Eur. J. Org.
Chem. 2003, 4113–4117; b) A. T. Khan, E. Mondal, S. Ghosh,
S. Islam, Eur. J. Org. Chem. 2004, 2002–2009; c) A. T. Khan,
S. Ghosh, L. H. Choudhury, Eur. J. Org. Chem. 2004, 2198–
3
[
2
[
[
32] N. Sumida, K. Nashioka, T. Sato, Synlett 2001, 1921–1922.
33] M. J. Gregory, J. Chem. Soc., B 1970, 1201–1207.
2204; d) A. T. Khan, L. H. Choudhury, S. Ghosh, Tetrahedron
Lett. 2004, 45, 7891–7894; e) A. T. Khan, S. Islam, L. H.
Choudhury, S. Ghosh, Tetrahedron Lett. 2004, 45, 9617–9621.
20] a) Y.-S. Hon, C.-F. Lee, Tetrahedron Lett. 1999, 40, 2389–2392;
b) Y.-S. Hon, C.-F. Lee, R.-J. Chenn, P.-H. Szu, Tetrahedron
[34] J. K. Michie, J. A. Miller, Synthesis 1981, 824.
[35] B. Karimi, H. Seradj, G. R. Ebrahimian, Synlett 2000, 623–
624.
[36] N. Deka, D. J. Kalita, R. Borah, J. C. Sarma, J. Org. Chem.
1997, 62, 1563–1564.
[37] N. Deka, R. Borah, D. J. Kalita, J. C. Sarma, J. Chem. Res.
(S) 1998, 94–95.
[38] K. S. Kochhar, B. S. Bal, R. P. Despande, S. N. Rajadhyaksha,
H. W. Pannick, J. Org. Chem. 1983, 48, 1765–1767.
[39] D. H. Aggen, J. N. Arnold, P. D. Hayes, N. J. Smoter, R. S. Mo-
han, Tetrahedron 2004, 60, 3675–3679.
[
[
2
001, 57, 5991–6001; c) Y.-S. Hon, C.-F. Lee, Tetrahedron 2001,
5
7, 6181–6188.
21] J. W. Hilborn, E. MacKnight, J. A. Pincock, P. J. Wedge, J. Am.
Chem. Soc. 1994, 116, 3337–3346.
22] A. McKillop, M. E. Ford, Tetrahedron 1974, 30, 2467–2475.
23] C. A. Grob, P. Sawlewicz, Helv. Chim. Acta 1988, 71, 1508–
[
[
1510.
[24] K. Fujimoto, Y. Tokuda, H. Mackawa, Y. Matsubara, T. Mi-
zuno, I. Nishiguchi, Tetrahedron 1996, 52, 3889–3896.
[40] K. L. Chandra, P. Saravanan, V. K. Singh, Synlett 2000, 359–
360.
[
[
25] B. M. Trost, C. Lee, J. Am. Chem. Soc. 2001, 123, 12191–12201.
26] H. Held, A. Rengstle, D. Mayer, Ullman’s Encyclopedia of In-
[41] V. K. Aggarwal, S. Fonquerna, G. P. Vennall, Synlett 1998,
th
dustrial Chemistry, 5 (Ed.: W. Gerhartz), VCH, New York,
849–850.
Vol. A1, p. 68.
Received: January 27, 2005
Eur. J. Org. Chem. 2005, 2782–2787
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2787