A simple and efficient heterogeneous procedure for thioacetalization of aldehydes and ketones

Article abstract of DOI:10.1055/s-2005-865303

A new procedure for the protection of aldehydes and ketones as thioacetals promoted by catalytic amount of p-toluene-sulfonic acid and silica gel has been developed. This procedure offers versatility, short reaction time, excellent yield, good selectivity

Full text of DOI:10.1055/s-2005-865303

1326
PAPER
A Simple and Efficient Heterogeneous Procedure for Thioacetalization of
Aldehydes and Ketones
Thioacetalizationof
Ao
h
K
etone
s
ammed Hashmat Ali,* Maria Goretti Gomes
Chemistry Department, Southeast Missouri State University, Cape Girardeau, MO 63701, USA
Fax +1(573)9866433; E-mail: mhali@semo.edu
Received 13 July 2004; revised 18 December 2004
p-Toluenesulfonic acid has been utilized in the past for
Abstract: A new procedure for the protection of aldehydes and ke-
tones as thioacetals promoted by catalytic amount of p-toluene-
sulfonic acid and silica gel has been developed. This procedure
offers versatility, short reaction time, excellent yield, good selectiv-
promoting thioacetalization reactions in homogeneous re-
action media.22 In this reported reaction, the by-product
water was removed by distillation as benzene azeotrope to
ity, and flexibility in terms of choice of solvent that can be utilized help equilibrium favor formation of the product. The het-
in this reaction. The procedure is easy to carry out and does not re-
erogeneous procedure reported in this communication
quire aqueous work-up. A simple filtration followed by removal of
solvent in most cases produces pure product.
does not require removal of water by distillation. Hygro-
scopic silica gel used in this procedure removes the water
produced in this reaction thereby shifting the equilibrium
in favor of the thioacetal formation.
Key words: thioacetal, silica gel, heterogeneous, ketones, alde-
hydes
According to this procedure, when an equimolar mixture
of aldehydes or ketones, 1,2-ethanedithiol (or two equiv-
It is often necessary to protect carbonyl groups to avoid
alents of an alkanethiol), small amounts of p-toluene-
complications that may arise from involvement of a nu-
sulfonic acid, and silica gel in dichloromethane is heated
cleophile targeted for another part of the molecule.1 Thio-
under reflux, cyclic (or acyclic) thioacetals are produced
acetals are stable in both acidic and basic reaction media
in excellent yields (Scheme 1).
and a wide range of homogeneous and heterogeneous re-
agents are available to remove thioacetal protection from
carbonyl groups.2 Therefore, conversion of a carbonyl
group to a thioacetal is generally a preferred method of
protection in organic syntheses. Thioacetalization of car-
bonyl groups using TiCl4,3 TeCl4,4 InCl3,5 Sc(OTf)3,6 zinc
9
and magnesium triflates,7 BF3·OEt2,8 and Bi(NO3)3 in ho-
mogeneous reaction conditions have been reported. Het-
erogeneous reagents such as silica gel treated with thionyl
chloride,10 Nafion-H,11 Zeolites,12 Amberlyst-15,13 Fe3+-
Montmorillonite,14 ZrCl415 and CoBr2 on silica gel,16 En-
virocat EPZG,17 Cu(OTf)2-SiO2,18 and heteropolyacids19
are known to promote thioacetalization of carbonyl
groups.
Heterogeneous reagents offer additional benefits that their
homogeneous counterparts do not. In general, procedures
involving heterogeneous reagents require minimum han- Scheme 1
dling of the reagents, show higher product selectivity, pro-
duce enhanced reaction rates, generate smaller amounts of
The most important advantages of this procedure are that
solid waste, and make product isolation easy. These ad-
an aqueous work-up is not necessary and a simple filtra-
vantages associated with heterogeneous reagents satisfy a
tion allows isolation of products. The procedure for thio-
acetalization in the presence of silica gel reported here is
number of important criteria for Green Chemistry.20
very clean and produces excellent yields of the desired
thioacetals. In most cases the isolated products required
no further purification. Polar byproducts, if formed, re-
main absorbed on the silica gel and are removed during
filtration. However, a limited number of products was
found to be contaminated with a trace amount of p-tolu-
enesulfonic acid. Products contaminated with p-toluene-
sulfonic acid were easily purified using the column or
radial chromatography techniques.
In continuation of our interest in the utilization of solid
supports in organic reactions,21 we have investigated the
title reaction using p-toluenesulfonic acid and silica gel in
dichloromethane and hexanes media.
SYNTHESIS 2005, No. 8, pp 1326–1332
x
x
.
x
x
.2
0
0
5
Advanced online publication: 07.04.2005
DOI: 10.1055/s-2005-865303; Art ID: M05004SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Thioacetalization of Aldehydes and Ketones
1327
Silica gel facilitates the reaction by removing water as duced a near quantitative yield of the corresponding cyclic
soon as it is produced in the reaction mixture. We have thioacetal 2a in 6 hours compared to 25 hours required for
carried our thioacetalization reaction on a number of alde- cyclododecanone (1b) to produce the corresponding thio-
hydes and ketones, some containing additional functional- acetals 2b in dichloromethane reaction media (Table 1).
ities. These results are presented in the tables below. Also, we observed that the thioacetalization of aldehydes
Thioacetalization of aliphatic aldehydes and ketones are is faster than those for ketones. The a,b-unsaturated alde-
presented in Table 1.
hyde 1h produced excellent yields of the aldehyde pro-
tected product 2h. We conclude that this rate difference is
due to greater steric hindrance posed by the ketones com-
pared to the aldehydes. Under similar reaction conditions,
aromatic aldehydes and ketones also produced excellent
yields of cyclic thioacetals. Results of acetalization of ar-
omatic aldehydes 3a–j and ketones 5a–g are presented in
the Tables 2 and 3 respectively.
Aliphatic aldehydes and ketones produced excellent
yields of the protected thioacetals. As expected, sterically
hindered ketones 1b, 1f, 1g, and 1i reacted sluggishly
compared to unhindered ketones thereby requiring longer
reaction times. For example, cyclohexanone (1a) pro-
Table 1 Thioacetalization of Aliphatic Aldehydes and Ketones
Thioaetalization of aromatic aldehydes 3a–j are signifi-
cantly faster than those for the ketones 5a–g. Presence of
an electron-donating group on the benzene ring help the
thioacetalization reaction proceeds faster. On the other
hand, an electron-withdrawing group on the benzene ring
slows the rate of the reaction. Also, comparison of the data
clearly indicates that the aromatic aldehydes are more re-
active towards the thioacetalization reaction than their ali-
phatic counterparts. Significant rate differences between
the thioacetalization of aldehydes and ketones under het-
erogeneous reaction conditions encouraged us to investi-
gate the possibility for the selective protection of
aldehydes in the presence of ketones. Such selective pro-
tection has been previously reported in homogeneous re-
action media.5,13
Entry
Aldehyde/Ketone 1
Reaction
time (h)
Yield (%) of
thioacetal 2a
a
6
5
15
98
93b
77c
b
25
94
c
7.5
8
78
75b
d
3.5
77
We carried out a number of competitive thioacetalization
reactions using equimolar mixture of various aldehydes
and ketones with 1,2-ethanedithiol (Scheme 2). These re-
actions produced thioacetals of the aldehydes and the ke-
tones remained unchanged. Thioacetalization of
compound 7 possessing an aldehyde and a ketone func-
tional group produced compound 8. The results of this
study are presented in Table 4. These results clearly dem-
onstrate that selective protection of aldehyde in the pres-
ence of ketone is possible using the procedure reported in
this communication.
e
f
3.5
8
88
71c
24
86
g
27
4
94
97
h
Acyclic thioacetals are produced in excellent yields when
1,2-ethanedithiol is replaced with alkanethiols in our pro-
cedure. Reactions of vanillin (3c) with two equivalents of
ethanethiol and butanethiol produced thioacetals 9 and 10,
respectively, in excellent yields (Table 5).
i
12
6
91
87
j
k
6
81
a Chromatographically isolated product.
b Hexanes used as the reaction media.
c Reaction carried out in the absence of silica gel.
Scheme 2
Synthesis 2005, No. 8, 1326–1332 © Thieme Stuttgart · New York

1328
M. H. Ali, M. Goretti Gomes
PAPER
Table 2 Thioacetalization of Aromatic Aldehydes
Table 3 Thioacetalization of Aromatic Ketones
Entry
Aldehyde 3
Reaction
time (h)
Yield (%) of
Entry
Ketone 5
Reaction
time (h)
Yield (%) of
thioacetal 4a
thioacetal 6a
a
3
4.5
10
ca. 100
93b
a
26
27
97
76c
b
c
4.5
98
b
c
96
1.5
ca. 100
72
98
(71% conver-
sion)b
d
e
f
1.5
2.5
ca. 100
91b
d
12.5
81b
1.5
3
90
97
85
e
f
22
27
80b
95
g
3
g
22
91
h
i
0.75
6.5
94
88c
6
97
71
a Chromatographically isolated product.
b Remaining unreacted ketones recovered.
j
0.25
Table 4 Competitive Thioacetalization of Aromatic Aldehydes/Ke-
tones with 1,2-Ethanedithiol
Entry Aldehyde + Ketone Product
Reaction- Yield
time (h) (%)a
a Chromatographically isolated product.
b Hexanes used as the reaction media.
1
2
3a + 5a
4a
4i
3
4
ca. 100
98
c Reaction carried out in the absence of silica gel.
3i + p-nitroaceto-
phenone
3
4
5
6
3b + 5f
3d + 5b
3e + 5d
4b
4d
4e
2
96
Since the silica gel used in this procedure is slightly acid-
ic, we wanted to examine the role silica gel play promot-
ing this reaction. We carried out thioacetalizations of
piperonal (3h) with 1,2-ethanedithiol in the presence and
in the absence of p-toluenesulfonic acid. Silica gel was
present in both of these reactions.
1.5
1
ca. 100
95
3
97
Data presented in Scheme 3 indicate that both silica gel
and p-toluenesulfonic acids are capable of promoting
thioacetalization reactions. However, the role p-toluene-
sulfonic acid play in promoting this reaction is far greater
than that of silica gel. In the presence of p-toluenesulfonic
7
8
a Chromatographically isolated product.
Synthesis 2005, No. 8, 1326–1332 © Thieme Stuttgart · New York

PAPER
Thioacetalization of Aldehydes and Ketones
1329
Table 5 Thioacetalization of Vanillin with Ethanethiol and Butane- time) of these reactions in hexanes and in dichlo-
thiol
romethane is very similar. It is clearly evident that hex-
anes can be utilized as a reaction media in this
Entry Aldehyde 3c
Product
Reaction Yield
time (h)
heterogeneous thioacetalization procedure. Replacing a
halogenated solvent with a non-halogenated solvent is a
big plus for this procedure. Poor solubility of some carbo-
nyl compounds and/or products in hexanes are the only
disadvantages we anticipate in using hexanes as the reac-
tion media. Currently we are investigating thioacetaliza-
tion of various carbonyl compounds in several non-
halogenated solvents including hexanes. These results
will be published in due course.
(%)a
1
2.5
96
9
2
3
93
In summary, we have developed a simple and highly effi-
cient heterogeneous procedure for thioacetalization of al-
dehydes and ketones. Other notable advantages of the
procedure presented here include selective protection of
an aldehyde in the presence of a ketone, high product
yield, clean reaction, easy workup and smaller amounts of
waste. This procedure is equally efficient for generating
cyclic as well as acyclic thioacetals. In addition, this pro-
cedure holds promise in replacing dichloromethane with
non-halogenated solvents without sacrificing the efficien-
cy.
10
a Chromatographically isolated product.
acid thioacetalization reaction of piperonal (3h) took 45
minutes to complete. In the absence of p-toluenesulfonic
acid no significant amount of thioacetal 4h was detected
during the same reaction period. However, when the later
reaction was allowed to continue for 24 hours, 35% of the
piperonal (3h) was converted to the corresponding thioac-
etal 4h and the remaining piperonal (3h) was recovered
unchanged.
All reaction mixtures were stirred using Teflon coated magnetic
stirring bars. All reagents and solvents were used as they were re-
ceived from the suppliers without further purification. All products
were identified by NMR and IR data. The silica gel, used as solid
support, was MN-Kieselgel 60 (0.04–0.063 mm mesh size) supplied
1
by Fisher Scientific. H NMR spectra were recorded on a Bruker
DPX-300 NMR instrument. Samples for NMR were dissolved in
CDCl3. Proton chemical shifts are expressed in ppm relative to tet-
ramethylsilane. IR spectra were recorded on a Perkin-Elmer Spec-
trum 1000 FT-IR instrument and are reported in wave numbers
(cm–1). Chromatographic separations were carried out by prepara-
tive centrifugal TLC with silica gel (Merck #7749) on a Chroma-
totron Model 7924T. Analytical TLC was done on pre-coated silica
gel plates with 254 nm fluorescent indicator (Merck # 5715) and de-
veloped in EtOAc–hexanes mixed solvent systems. Compounds
were visualized by a UV lamp and/or by staining either with p-anis-
aldehyde/H2SO4 or phosphomolybdic acid.
Scheme 3
Thioacetalization of Aldehydes and Ketones; General Proce-
dure
In the presence of silica gel thioacetalization reactions
proceed faster and produce higher yield of the products
compared to the reactions carried out in the absence of sil-
ica gel (Table 1, entries a and e and Table 2, entries a and
h). Various amounts of the starting materials were isolat-
ed along with the products in the silica gel free reactions.
A 100 mL round-bottom flask fitted with a condenser was charged
with silica gel (4 g), CH2Cl2 or hexane (20 mL), an aldehyde or a
ketone (2.5 mmol), 1,2-ethanedithiol (2.75 mmol or 5.50 mmol of
an alkylthiol), and p-toluenesulfonic acid (10–15 mg). The hetero-
geneous mixture was refluxed under stirring with a magnetic stirrer.
Progress of the reaction was monitored either by TLC analysis or IR
spectroscopy. After complete disappearance of the starting carbonyl
compound, the reaction mixture was filtered through a sintered-
glass funnel. The solid residue was washed with CH2Cl2 (ca. 75
mL), or with EtOAc (ca. 75 mL) when hexane was used as the reac-
tion media. The solvent was evaporated under vacuum to isolate the
product. In most of the cases the isolated crude product was found
to be pure as indicated by NMR and IR spectra. However, the im-
pure products were purified utilizing flash column or radial chroma-
tography using a mixture of EtOAc and hexane. Several
thioacetalization reactions were scaled up to 100 mmol of carbonyl
compounds. Yields of these large scale reactions were comparable
to the yields reported in Tables 1–5.
We believe that the observed rate enhancement is due to
the spreading of the acid catalysts over a large surface area
provided by the silica gel. However other factor(s) may
also be responsible for the observed rate enhancement.
We then examined hexanes as the reaction media in thio-
acetalization of cyclohexanone (1a), heptan-4-one (1c),
benzaldehyde (3a), and p-tolualdehyde (3d) with 1,2-
ethanedithiol. These reactions proceeded smoothly to pro-
duce excellent yields of the corresponding thioacetals
(Tables 1 and 2). Efficiency (product yield and reaction
Synthesis 2005, No. 8, 1326–1332 © Thieme Stuttgart · New York

1330
2a4
M. H. Ali, M. Goretti Gomes
PAPER
2i
IR (neat): 2929, 2853, 1446, 1275, 1014 cm–1.
IR (neat): 732, 908, 963, 1014, 1275, 1455, 2853, 2925 cm–1.
1H NMR: d = 1.60 (m, 8 H), 2.20 (m, 4 H), 3.28 (m, 4 H).
13C NMR: d = 25.60, 28.60, 38.90, 46.10, 71.90.
1H NMR: d = 1.30–1.40 (m, 2 H), 1.53–1.65 (m, 4 H), 1.90–1.98 (m,
4 H), 3.22 (s, 4 H)
13C NMR: d = 24.98, 26.2 (2 CH2), 28.7, 38.3, 42.9 (2 CH2), 68.82.
2j
2b4
IR (neat): 806, 852, 971, 1026, 1083, 1135, 1234, 1276, 1376, 1427,
IR (neat): 2927, 1466 cm–1.
1440, 1455, 2848, 2918 cm–1.
1H NMR: d = 1.25–1.54 (m, 18 H), 1.98–2.07 (m, 4 H), 3.28 (s, 4
1H NMR: d = 0.90 (d, J = 6.5 Hz, 3 H), 1.2–1.40 (m, 3 H), 1.67–1.72
H).
(m, 2 H), 1.85–1.96 (m, 2 H), 2.07–2.12 (m, 2 H), 3.22–3.29 (m, 4
H).
13C NMR: d = 22.42, 22.60, 22.65, 25.91, 26.37, 38.61 (2 CH2),
38.88, 71.12.
13C NMR: d = 21.90, 31.10, 34.50 (2 CH2), 37.90, 38.70, 42.30 (2
CH2), 68.30.
2c
IR (neat): 2958, 2931, 2871, 1731, 1463, 1377, 1276, 1139, 853,
2k25
767 cm–1.
IR (neat): 686, 733, 852, 972, 1056, 1139, 1276, 1374, 1448, 2859,
2927, 2957 cm–1.
1H NMR: d = 0.85–1.00 (t, J = 7.3 Hz, 6 H), 1.4–1.55 (m, 4 H), 1.8–
1.93 (t, J = 6.8 Hz, 4 H), 3.25 (s, 4 H).
13C NMR: d = 14.25, 20.18, 28.73, 39.40 (2 CH2), 45.75.
1H NMR: d = 0.92 (t, J = 7.1 Hz, 3 H), 1.30–1.38 (m, 2 H), 1.43–
1.54 (m, 2 H), 1.75 (s, 3 H), 1.90–1.95 (m, 2 H), 3.30 (m, 4 H).
13C NMR: d = 14.00, 22.90, 29.50, 32.30, 40.00 (2 CH2), 45.80,
66.80.
2d
IR (neat): 2961, 2873, 1707, 1459, 1380, 1275 cm–1.
4a4
1H NMR: d = 0.87–0.93 (t, J = 7.3 Hz, 6 H), 1.35–1.63 (m, 4 H),
2.73–2.76 (m, 1 H), 3.13–3.23 (m, 4 H), 4.62–4.65 (d, J = 6.2 Hz, 1
H).
13C NMR: d = 10.91 (2 CH3), 23.94 (2 CH2), 28.72, 38.42 (2 CH2),
58.22.
IR (neat): 3429, 3060, 3026, 2922, 1690, 1661, 1600, 1494, 1451,
1422, 1276 cm–1.
1H NMR: d = 3.23–3.46 (m, 4 H), 5.61 (s, 1 H), 7.19–7.30 (m, 3 H),
7.49 (d, J = 7.10 Hz, 2 H).
13C NMR: d = 40.81 (2 CH2), 56.82, 128.52, 128.56, 129.02,
140.94.
2e23
IR (neat): 2955, 2926, 2854, 1735, 1465, 1377, 1275, 851, 725 cm–1.
4b4
1H NMR: d = 0.87 (t, J = 7.2 Hz, 3 H), 1.1–1.47 (m, 8 H), 1.79 (br
s, 2 H), 3.18 (br s, 4 H), 4.35–4.45 (m, 1 H).
13C NMR: d = 14.07, 22.57, 28.89, 29.10, 31.47, 38.34 (2 CH2),
39.41, 53.81.
IR (neat): 3006, 2903, 1486, 1404, 1085, 1012, 754 cm–1.
1H NMR: d = 3.20–3.70 (m, 4 H), 5.58 (s, 1 H), 7.31 (d, J = 8.4 Hz,
2 H), 7.41 (d, J = 8.4 Hz, 2 H).
13C NMR: d = 40.27 (2 CH2), 55.44, 128.57, 129.30, 133.61,
139.02.
2f23
IR (thin film): 2989, 2955, 1743, 1660, 1606, 1482, 1454, 1419,
1389, 1370, 1304, 1275 cm–1.
4c26
IR (thin film): 3434 (br), 2996, 2918, 1607, 1596, 1509, 1464, 1449,
1H NMR: d = 0.84 (s, 3 H), 0.91 (s, 3 H), 0.96 (s, 3 H), 1.30–1.44
(m, 2 H), 1.65–1.97 (m, 6 H), 2.11 (m, 1 H), 2.30–2.40 (m, 1 H),
2.75 (m, 1 H).
13C NMR: d = 9.25, 19.14, 19.77, 27.04, 28.70, 29.89, 31.19, 40.32,
43.02, 43.28, 46.77, 57.67.
1427, 1266, 1227, 1145, 1118, 1026 cm–1.
1H NMR: d = 3.29–3.53 (m, 4 H), 3.88 (s, 3 H), 5.69 (s, 1 H), 6.81
(d, J = 8.1 Hz, 1 H), 6.90–7.00 (dd, J = 8.1, 1.69 Hz, 1 H), 7.09 (s,
1 H).
13C NMR: d = 40.14 (2 CH2), 55.91, 56.69, 110.26, 113.97, 121.07,
131.22, 145.54, 146.47.
2g
IR (neat): 3083, 3060, 3027, 2959, 2919, 2856, 1602, 1494, 1452,
1372, 1276, 1083, 752, 698 cm–1.
4d26
IR (neat): 3004, 1510, 1437, 1411, 1277, 1177, 1165, 830, 777 cm–1.
1H NMR: d = 2.32 (s, 3 H), 3.29–3.52 (m, 4 H), 5.62 (s, 1 H), 7.10
(d, J = 6.5 Hz, 2 H), 7.40 (d, J = 6.5 Hz, 2 H).
13C NMR: d = 21.11, 40.20 (2 CH2), 56.12, 127.80, 129.15, 137.10,
137.84.
1H NMR: d = 1.71 (s, 3 H), 3.00–3.32 (m, 6 H), 7.15–7.36 (m, 5 H).
13C NMR: d = 31.78, 39.72 (2 CH2), 51.41, 66.59, 126.68, 127.66,
130.69, 137.74.
2h24
IR (neat): 3083, 3057, 3028, 2963, 2924, 1599, 1576, 1497, 1447,
1434, 1421, 968, 763, 687cm–1.
4e26
IR (neat): 3188 (br), 2919, 1595, 1509, 1448, 1237, 1173, 838 cm–1.
1H NMR: d = 3.30–3.51 (m, 4 H), 5.00 (s, 1 H), 5.62 (s, 1 H), 6.73–
6.79 (m, 2 H), 7.37–7.43 (m, 2 H).
1H NMR: d = 3.24–3.37 (m, 4 H), 5.21 (d, J = 9.1 Hz, 1 H), 6.16–
6.25 (dd, J = 9.1, 15.5 Hz, 1 H), 6.49 (d, J = 15.5 Hz, 1 H), 7.22–
7.38 (m, 5 H).
13C NMR: d = 39.59 (2 CH2), 54.47, 126.60, 127.81, 128.53,
129.02, 130.14, 136.04.
13C NMR: 40.20 (2 CH2), 56.01, 115.31, 129.41, 131.99, 155.31.
Synthesis 2005, No. 8, 1326–1332 © Thieme Stuttgart · New York

PAPER
Thioacetalization of Aldehydes and Ketones
1331
4f
1H NMR: d = 2.31 (s, 3 H), 3.39 (m, 4 H), 7.08 (d, J = 8.1 Hz, 2 H),
7.23–7.27 (m, 3 H), 7.48 (d, J = 8 Hz, 2 H), 7.60 (m, 2 H).
13C NMR: d = 20.96, 40.12 (2 CH2), 127.10, 127.73, 127.97,
128.17, 128.64, 136.95, 141.47, 144.77.
IR (neat): 3068, 3001, 2959, 2922, 2834, 1597, 1585, 1486, 1462,
1437, 1285, 1249, 1102, 1048, 1027, 848, 753 cm–1.
1H NMR: d = 3.24–3.42 (m, 4 H), 3.83 (s, 3 H), 6.06 (s, 1 H), 6.81
(d, J = 8.2 Hz, 1 H), 6.92 (m, 1 H), 7.20 (m, 1 H), 7.71 (d, J = 7.65
Hz, 1 H).
6d
IR (neat): 687, 738, 831, 844, 1074, 1180, 1230, 1273, 1375, 1442,
13C NMR: d = 39.33 (2 CH2), 48.99, 55.57, 110.39, 120.52, 128.04,
1508, 1596, 1608, 2876, 2929, 2969, 3225 (br) cm–1.
128.74, 129.16, 156.46.
1H NMR: d = 2.13 (s, 3 H), 3.35–3.51 (m, 4 H), 5.60 (br s, 1 H), 6.75
(d, J = 7.7 Hz, 2 H), 7.63 (d, J = 7.7 Hz, 2 H).
4g
IR (neat): 3038, 2999, 2923, 2833, 1597, 1488, 1464, 1434, 1316,
13C NMR: d = 33.91, 40.35 (2 CH2), 68.22, 114.71, 128.33, 137.73,
1263, 1149, 1047, 862, 779, 749, 693 cm–1.
154.64.
1H NMR: d = 3.10–3.45 (m, 4 H), 3.73 (s, 3 H), 5.58 (s, 1 H), 6.76
(d, J = 7.32 Hz, 1 H), 7.05–7.21 (m, 3 H).
6e
IR (thin film): 3061, 3015, 2924, 2960, 1580, 1474, 1447, 1418,
13C NMR: d = 40.04 (2 CH2), 55.08, 56.04, 113.34 (2 C), 120.14,
1277, 741 cm–1.
129.32, 141.91, 159.45.
1H NMR: d = 3.73 (br s, 4 H), 7.28–7.34 (m, 4 H), 7.58–7.69 (m, 4
H).
4h27
IR (neat): 3068, 2921, 2777, 1609, 1500, 1487, 1443, 1370, 1249,
13C NMR: d = 28.65, 42.24 (2 CH2), 119.76, 125.09, 128.25,
1183, 1096, 1038, 927, 866, 750 cm–1.
128.51, 138.35, 150.36.
1H NMR: d = 3.25–3.53 (m, 4 H), 5.60 (s, 1 H), 5.94 (s, 2 H), 6.69
(d, J = 8 Hz, 1 H), 6.91–6.95 (dd, J = 8, 1.7 Hz, 1 H), 7.10 (d,
J = 1.7 Hz, 1 H).
13C NMR: d = 40.24 (2 CH2), 56.35, 101.20, 107.73, 108.32,
121.35, 133.88, 147.46, 147.85.
6f
IR (neat): 734, 830, 1011, 1069, 1093, 1275, 1372, 1396, 1422,
1444, 1489, 1570, 1591, 2860, 2922, 2966, 3059 cm–1.
1H NMR: d = 2.1 (s, 3 H), 3.30–3.45 (m, 4 H), 7.26 (d, J = 6.4 Hz,
2 H), 7.68 (d, J = 6.4 Hz, 2 H).
13C NMR: d = 33.46, 40.31 (2 CH2), 67.82, 127.87, 128.24, 132.70,
144.55.
4i26
IR (neat): 3102, 2923, 2853, 1932, 1605, 1594, 1518, 1350, 1108,
867, 727 cm–1.
1H NMR: d = 3.4–3.65 (m, 4 H), 5.65 (s, 1 H), 7.67 (d, J = 8.3 Hz,
2 H), 8.15 (d, J = 8.3 Hz, 2 H).
13C NMR: d = 40.47 (2 CH2), 54.86, 123.71, 128.81, 147.34,
148.63.
6g
IR (neat): 731, 827, 1007, 1077, 1275, 1391, 1486, 1583, 2858,
2922, 2965, 3061 cm–1.
1H NMR: d = 2.07 (s, 3 H), 3.30–3.45 (m, 4 H), 7.38 (d, J = 6.8 Hz,
2 H), 7.60 (d, J = 6.8 Hz, 2 H).
13C NMR: d = 34.10, 41.01 (2 CH2), 68.50, 114.03, 129.60, 131.50,
145.76.
4j24
IR (neat): 757, 824, 949, 1069, 1171, 1230, 1247, 1359, 1443, 1482,
1523, 1609, 2807, 2904, 3054 cm–1.
1H NMR: d = 2.95 (s, 6 H), 3.32–3.36 (m, 2 H), 3.48–3.54 (m, 2 H),
5.65 (s, 1 H), 6.81 (d, J = 6.8 Hz, 2 H), 7.42 (d, J = 6.8 Hz, 2 H).
13C NMR: d = 40.09 (2 CH3), 40.80 (2 CH2), 56.40, 112.60, 125.90,
128.77, 149.88.
810
IR (neat): 760, 861, 960, 1017, 1111, 1271, 1355, 1414, 1574, 1605,
1677, 2876, 2918, 2952, 3086 cm–1.
1H NMR: d = 2.59 (s, 3 H), 3.36–3.53 (m, 4 H), 5.65 (s, 1 H), 7.60
(d, J = 8 Hz, 2 H), 7.91 (d, J = 8 Hz, 2 H).
13C NMR: d = 26.64, 40.33 (2 CH2), 55.41, 128.08, 128.54, 136.57,
146.19, 197.45.
6a24
IR (neat): 3061, 2924, 1684, 1599, 1582, 1449, 1359, 1266, 760,
690, 588 cm–1.
1H NMR: d = 2.14 (s, 3 H), 3.33–3.47 (m, 4 H), 7.20–7.30 (m, 3 H),
9
7.73–7.76 (m, 2 H).
IR (neat): 3413 (br), 2966, 1674, 1595, 1512, 1463, 1431, 1269,
1206, 1120, 1031, 730 cm–1.
13C NMR: d = 33.89, 40.27 (2 CH2), 68.63, 126.75, 127.03, 127.96,
145.96.
1H NMR: d = 1.19–1.24 (t, J = 7.4 Hz, 6 H), 2.48–2.62 (q, J = 7.4
Hz, 4 H), 3.87 (s, 3 H), 4.89 (s, 1 H), 5.93 (br s, 1 H), 6.80–7.04 (m,
3 H).
6b
IR (neat): 731, 819, 1018, 1072, 1126, 1185, 1275, 1371, 1443,
13C NMR: d = 14.32 (2 CH3), 26.33 (2 CH2), 52.28, 55.93, 110.01,
1508, 1610, 1654, 2861, 2921, 2965, 3022 cm–1.
113.88, 120.73, 132.25, 145.29, 146.78.
1H NMR: d = 2.14 (s, 3 H), 2.32 (s, 3 H), 3.30–3.52 (m, 4 H), 7.11
(d, J = 8 Hz, 2 H), 7.63 (d, J = 8 Hz, 2 H).
10
IR (neat): 3436 (br), 2956, 1601, 1512, 1463, 1377, 1268, 1119,
13C NMR: d = 20.89, 33.87, 40.29 (2 CH2), 68.39, 126.67, 128.64,
1033 cm–1.
136.74, 142.87.
1H NMR: d = 0.85–0.90 (t, J = 6.8 Hz, 6 H), 1.33–1.40 m, 4 H),
1.48–1.56 (m, 4 H), 2.47–2.60 (m, 4 H), 3.86 (s, 3 H), 4.84 (s, 1 H),
5.87 (s, 1 H), 6.80–6.90 (m, 2 H), 7.05 (s, 1 H).
6c
IR (thin film): 696, 741, 1032, 1186, 1275, 1443, 1506, 1594, 2874,
2921, 3022, 3056 cm–1.
Synthesis 2005, No. 8, 1326–1332 © Thieme Stuttgart · New York

1332
M. H. Ali, M. Goretti Gomes
PAPER
13C NMR: d = 13.66 (2 CH3), 21.77 (2 CH2), 31.27 (2 CH2), 32.06
(2 CH2), 53.07, 55.92, 110.01, 113.86, 120.78, 132.43, 145.29,
147.77.
(14) Choudary, B. M.; Sudha, Y. Synth. Commun. 1996, 26, 767.
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Synthesis 2005, No. 8, 1326–1332 © Thieme Stuttgart · New York