Synthesis of 3-bromotetronamides via amination of 3,4-dibromofuran-2(5H)- one

Article abstract of DOI:10.1590/S0103-50532011000300026

This work describes the direct synthesis of 3-bromotetronamides in good yields through the reaction of 3,4-dibromofuran-2(5H)-one, obtained from furfural, with primary and secondary amines. Aromatic amines were more tolerated than aliphatic and heteroaromatic ones. The X-ray structures of five derivatives are described.

Full text of DOI:10.1590/S0103-50532011000300026

J. Braz. Chem. Soc., Vol. 22, No. 3, 598-603, 2011.
Printed in Brazil - ©2011 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Short Report
S
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
Silvio Cunha,*,a,c Caio C. Oliveiraa,c and José R. Sabinob
aInstituto de Química and cInstituto Nacional de Ciência e Tecnologia - INCT em Energia e
Ambiente, Universidade Federal da Bahia, Campus de Ondina, 40170-290 Salvador-BA, Brazil
bInstituto de Física, Universidade Federal de Goiás, CP 131, 74001-970 Goiânia-GO, Brazil
Este trabalho descreve a síntese de dez tetronamidas em bons rendimentos através da reação
da 4-dibromofuran-2(5H)-ona, obtida do furfural, com aminas primárias e secundárias.As aminas
aromáticas foram mais toleradas que as alifáticas e as heteroaromáticas. Foram determinadas as
estruturas cristalinas de cinco derivados.
This work describes the direct synthesis of 3-bromotetronamides in good yields through the
reaction of 3,4-dibromofuran-2(5H)-one, obtained from furfural, with primary and secondary
amines. Aromatic amines were more tolerated than aliphatic and heteroaromatic ones. The X-ray
structures of five derivatives are described.
Keywords: enaminones, tetronamides, butenolides
Introduction
to 3-bromotetronamides (4-amino-3-bromo-2(5H)
furanones), which are a special class of cyclic compound
because they present both aspects mentioned above, i.e.,
the embedded enaminone moiety, and the bromide atom
at the alpha position. Besides, this study represents
an approach to 3-bromotetronamides from furfural, an
attractive starting material obtained from renewable
biomass. In this way, the furfural derivative of choice
was the 3,4-dibromofuran-2(5H)-one 1, which is easily
prepared in 70% overall yield by the reaction of furfural
with bromine in water, affording mucobromic acid
(commercially available also).8 This late was reduced
affording 1 in 87-96% yield, Scheme 1, employing
a recently described method by Bellina and Rossi.9
It should be pointed out that the reactions where 1 is
employed as electrophile is scarcely described, being
limited to palladium cross-coupling reactions,10 or only to
morpholine as nucleophile and expensive base (Cs2CO3).11
The synthesis of functionalized tetronamides is a theme
of ongoing research activity, and this interest is due to
the synthetic applications of such compounds, mainly in
heterocyclic synthesis.1 A particular class of synthetically
useful tetronamides are the 3-halo derivatives. However,
most of the available protocols for the synthesis of
3-halotetronamides are based on the direct halogenation
of a preformed enaminone, employing halogenation’s
reagents such as ICl, NBS, Br2, I2, I(py)2BF4 and benzyl-
trimetylammonium dichloroiodate (BTMA.ICl2).2
Cyclic enaminones are especially attractive in the
formation of bicyclic compounds.3 In this context,
tetronamides have embedded in their structure the
N-C=C-C=O enaminone moiety, and recently they have
emerged as a latent acyclic enaminone in the formal aza-
[3+3] cycloaddition reaction.4 However, the synthesis of
3-halotetronamides unsubstituted at position 5 is scarcely
described, being limited to the reaction of α-halotetronic
acid with an amine5 or by direct halogenation of
tetranamides.6 Thus, practical synthetic approaches to this
class of compound would be beneficial.
Results and Discussion
The amination of 1 has proved to be a difficult task
due to its propensity to forming polymeric material,
probably thought the corresponding homoenolate,
even in the presence of weak bases. Thus, complex
mixtures were formed with pyrrolidine, piperidine,
pyridine, 2-aminopyridine, 2-aminothiazol, benzylamine,
In our ongoing investigation on the chemistry
of enaminones,7 we envisioned herein a direct route
*e-mail: silviodc@ufba.br

Vol. 22, No. 3, 2011
Cunha et al.
599
of them, but some ortho substituted ones (entries 6, 8 and
10). Mechanistically, formation of all 3-bromotetronamides
3a-f is a nucleophilic substitution by an addition-elimination
pathway.
The use of 2 equiv. of amines can be a serious drawback
when expensive or no commercial amines are necessary. To
circumvent this limitation, one can imagine the use of one
equiv. of a trivial weak base to act as HBr scavenger. Due
to the decomposition of butenolide 1 in basic medium, we
investigated its stability in methanolic solution of equimolar
amounts of 1 and Et3N, Na2CO3 and NaHCO3. Compound 1
was completely decomposed after 4 h to the two first bases,
and after 24 h to the late. Because reaction of 1 and aromatic
amines is a slow one, we choose NaHCO3 as additive.
Fortunately, the amount of amines 2 could be reduced
to 1 equiv. and comparable yields of 3 were obtained when
the reaction was carried out in the presence of 1 equiv. of
NaHCO3 (entries 1, 3, 5, 7, Table 1). In general, anilines
with para substituents afforded better yields and shorter
reaction time than ortho substituted ones for both electron
releasing and electron withdrawing groups (compare entries
3-8). Hence, a diversity of 3-bromotetronamides could be
prepared, but the methodology presents some limitations,
because no reaction was observed with 4-nitroaniline,
diphenylaniline, 2,4-dichloroaniline and glycine, being
furanone 1 quantitatively recovered.
Scheme 1.
dibenzylamine, piperazine, cyclohexylamine and ethyl
3-aminocrotonate.
To test the possibility of a direct synthesis of
3-bromotetronamides, equimolar amounts of 1 and
morpholinewerereactedindiversesolventsandtemperatures,
but the starting material 1 was always detected by TLC.
Employing 2 equiv. of morpholine in diethyl ether (24 h) or
acetone (2.5 h) at room temperature complex mixture was
formed, but in acetone at low temperature (0 °C) tetronamide
3a could be obtained in modest 35% yield. However, when
the reaction was carried out in methanol at room temperature,
excellent yield was obtained (Table 1, entry 1). With this
optimal condition in hand, it was extended to a representative
spectrum of aromatic amines, and yields were good to all
1
Curiously, in the H NMR spectrum of 3c, the signal
of the aromatic hydrogens show up as a singlet integrated
Table 1. Isolated 3-bromotetronamide yields
Amine 2
R1 / R2
Yield / (%)
time / h
entry
Compound
Condition A (and B)a
1
2
3
4
5
6
7
8
9
10
3a
3b
3c
3d
3e
3f
CH2CH2OCH2CH2
H / Ph
92 (65)
89
24 (88)
22
H / p-CH3Ph
H / o-CH3Ph
H / p-CH3OPh
H / o-CH3OPh
H / p-ClPh
80 (87)
72
14 (200)
288
82 (78)
61
5 (6)
216
3g
3h
3i
78 (87)
23
73 (44)
120
H / o-ClPh
H / o-NH2Ph
H / α-naphthyl
75
14
3j
57
168
aCondition A: 2 equiv. of 2; Condition B: 1 equiv. of 2 and 1 equiv. of NaHCO3.

600
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
J. Braz. Chem. Soc.
to four hydrogens, and not as the typical pair of doublets
expected for para substituted aromatic rings. The
structure of 3c was unambiguously confirmed by X-rays
crystallography. Compounds 3a, 3e and 3g also afforded
single-crystals whose X-rays structures are shown in
Figure 1.
During the investigation on the reactivity of butenolide
1 with benzaldehyde in Knoevenagel condition, compound
3a and 5 were obtained, and the structure of the later
was corroborated by X-rays crystallography, as shown in
Figure 2. Mechanistically, the formation of 3a follows the
same addition-elimination pathway above mentioned, and
the formation of 5 represents a three component reaction.
In a control experiment, tetronamide 3a and benzaldehyde
were left in the same Knoevenagel reaction condition, but
the reagents were quantitatively recovered. Additionally,
butenolide 1 and benzaldehyde were tentatively reacted in
Knoevenagel condition with other no nucleophilic bases,
Figure 1. Ortep12 representations of 3a (top left), 3c (bottom left), 3e (top right), and 3g (bottom right). Displacement ellipsoids are drawn at the 30%
probability level and H atoms are shown as spheres of arbitrary radius.
Figure 2. Tricomponent reaction and Ortep12 representation of 5. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown
as spheres of arbitrary radius.

Vol. 22, No. 3, 2011
Cunha et al.
601
being the reagents recovered or the decomposition of 1
observed. These facts ruled out 3a as the intermediate in
the formation of 5, suggesting a homoaldol reaction of 1
and 4 followed by an addition-elimination and a last step
of water elimination to afford 5.
In contrast of the amines’ behavior with butenolide 1,
which afforded tetronamides 3a-j in good yields, no reaction
was observed with phenol. To gain more insight into the
potential of 3-bromotetronamides 3a-j as building block,
compound 3b was submitted to diverse intramolecular
Mizoroki-Heck reaction conditions, but the substrate was
recovered unchanged. The unique observed transformation
undertheseconditionwasthedebrominationofthebutenolide
ringwhendioxanewasemployedassolventwithcompounds
3b,e, affording the two known tetronamides 6a,b,13 which
represents a palladium catalyzed dehalogenation without
a formal hydride donor font, Scheme 2. A proposed
mechanism of the palladium-catalyzed dehalogenation
reaction is indicated in Figure 3, which was inspired in
a previously described formal hydride-free donor one,14
where DMF was employed as solvent and act as a hydride
source. Thus, the intermediate formed by the insertion of
Scheme 2.
Figure 3. Proposed mechanism of Pd-catalyzed dehalogenation.

602
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
J. Braz. Chem. Soc.
palladium (0) into the C-Br bond would react with dioxane
in the presence of triethylamine to yield the specie that
should suffer a beta-H elimination, followed by reductive
elimination of Pd0 from the resulting hydridopalladium
complex to give C-H, Figure 3.
In conclusion, we developed a practical synthesis
of 3-bromotetronamides in good yields, describing for
the first time that 3,4-dibromofuran-2(5H)-one 1 can
be conveniently employed as electrophile in reactions
with aromatic amines, amplifying the scope of such
transformation.11 Efforts are underway on the application
of these α-bromoenaminones in the synthesis of natural
and unnatural bioactive compounds.
stirring at room temperature. After 16 h the solvent was
evaporated and the crude residue purificated by column
chromatography (hexane:ethyl acetate 4:1), affording
0.162 g (19% yield) of 5 as a yellow solid, and 0.210 g
(34% yield) of yellow solid 3a after recrystallization in
ethyl acetate.
Compound 3a
mp 128-129 °C; IR (KBr) νmax/cm-1: 1766, 1029, 990;
1H NMR (CDCl3) d 3.63-3.66 (m, 4H), 3.78-3.81 (m, 5H),
4.71 (s, 2H); 13C NMR (CDCl3) d 171.41, 159.26, 72.80,
67.52, 66.17, 47.10.
Compound 5
Experimental
mp 149-154 °C; IR (KBr) νmax/cm-1: 2867, 1742, 1727,
1621, 1450; 1H NMR (CDCl3) d 3.69-3.72 (t, 4H, J 9.3 Hz),
3.85-3.88 (t, 4H, J 9.3 Hz), 6.13 (s, 1H), 7.32-7.41 (m, 3H),
7.71-7.44 (m, 2H); 13C NMR (CDCl3) d 50.85, 67.07, 85.33,
111.10, 128.80, 129.18, 130.54, 132.17, 157.11, 165.43.
Melting points were determined on a Microquímica
MQAPF 301 hot plate apparatus and are uncorrected.
Infrared spectra were recorded as KBr discs on a FT-IR
BOMEM MB100 instrument. NMR spectra were obtained
for 1H at 300 MHz and for 13C at 75 MHz using a Varian
Gemini 300 spectrometer. Chemical shifts are reported in
ppm units downfield from reference (internal TMS).
Synthesis of 6a,b
A suspension of 3b,e (0.5 mmol), PdCl2(PPh3)2
(0.035 g, 0.05 mmol) and triethylamine (0.15 g, 1.5 mmol)
in dry, degassed dioxane was refluxed until total substrate
consume (15 and 68 h for 3b and 3e, respectively). The
solvent was evaporated and the crude residue purificated
by column chromatography (ethyl acetate:hexane 7:3).
General synthetic condition A
To a solution of 1.0 mmol of 1 in 10 mL of CH3OH
was added 2.0 mmol of amine 2. The solution was left at
room temperature at the indicated time in Table 1. After
this time, the solvent was evaporated and 20 mL of CHCl3
was added, extracted with water (3 × 5 mL), and the organic
layer was dried over anhydrous Na2SO4, filtrated and the
solvent evaporated. The crude residue was recrystallized
from CHCl3/hexane affording a solid.
Compound 6a
Pale brown solid, mp 201-203 C (lit.13 220-221 C);
1H NMR (DMSO-D6) d 4.92 (s, 2H), 5.30 (s, 1H), 7.05
(t, 1H, J 7 Hz); 7.19 (d, 2H, J 7 Hz), 7.38 (t, 2H, J 7 Hz),
9.68 (s, 1H).
o
o
General synthetic condition B
Compound 6b
1
Pale brown solid; H NMR (CDCl3) d 4.94 (s, 2H),
To a solution of 1.0 mmol of 1 in 10 mL of CH3OH were
added 1.0 mmol of NaHCO3 and 1.0 mmol of amine 2. The
solution was left at room temperature at the indicated time
in Table 1. After this time, the solvent was evaporated and
20 mL of CHCl3 was added, extracted with water (3 × 5 mL),
and the organic layer was dried over anhydrous Na2SO4,
filtrated and the solvent evaporated. The crude residue was
recrystallized from CHCl3/hexane affording a solid.
5.19 (s, 1H), 7.05 (d, 2H, J 10 Hz); 7.21 (d, 2H, J 10 Hz),
9.60 (s, 1H).
X-ray analysis
Single-crystals of the compounds 3a, 3c and 3g were
mounted on a Bruker KappaCCD diffractometer, using
graphite filtered Mo-Kα, single-crystals the compounds
3e and 5 were mounted on an Enraf-Nonius CAD-4
diffractometer,15 using graphite filtered Cu-Kα radiation,
all using room temperature. The structure solutions were
obtained by Direct Methods using ShelxS97.16 Non
hydrogen atoms were refined with anisotropic displacement
parameters and hydrogen atoms were refined isotropic with
Synthesis of 3a and 5
Toasolutionof1(0.613g, 2.54mmol)andbenzaldehyde
(0.531 g, 5 mmol) in 20 mL of methanol, was added
0.356 mL of morpholine (0.349 g, 4 mmol) under magnetic

Vol. 22, No. 3, 2011
Cunha et al.
603
riding constraints to their parent atoms using ShelxL97.16
Refinement using Full-matrix least-squares on F2.
V.; Trends Heterocycl. Chem. 2005, 10, 73; Cheng, Y.; Huang,
Z. T.; Wang, M.-X.; Curr. Org. Chem. 2004, 8, 325; Ferraz, H.
M. C.; Pereira, F. L. C.; Quim. Nova 2004, 27, 89; Negri, G;
Kascheres, C; Kascheres, A. J.; J. Heterocyclic. Chem. 2004,
41, 461; Kascheres, C. M.; J. Braz. Chem. Soc. 2003, 14, 945;
Elassar, A.-Z. A.; El-Khair, A. A.; Tetrahedron 2003, 59, 8463.
4. Sydorenko, N.; Hsung, R. P.; Vera, E. L.; Org. Lett. 2006, 8,
2611; Sydorenko, N.; Hsung, R. P.; Darwish, O. S.; Hanh, J.
M.; Liu, J.; J. Org. Chem. 2004, 69, 6732.
Supplementary Information
CCDC 767789 (compound 5), CCDC 767791 (3g),
CCDC 767790 (3e), CCDC 643308 (3c) and CCDC
643307 (3a) contains the supplementary crystallographic
data for this paper. It can be obtained free of charge via
www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Supplementary data is available free of charge at
http://jbcs.sbq.org.br, as PDF file.
5. Kumler, W. D.; J. Am. Chem. Soc. 1940, 62, 2560; Albers, H.;
Mohler, W; Chem. Ber. 1963, 96, 357.
6. Schlessinger, R. H.; Petus, T. R. R.; J. Org. Chem. 1994, 59,
3246; Schlessinger, R.; Bergstrom, C. P.; J. Org. Chem. 1995,
60, 16; Schlessinger, R.; Bergstrom, C. P.; Tetrahedron Lett.
1996, 37, 2133.
7. Cunha, S.; Damasceno, F; Ferrari, J.; Tetrahedron Lett. 2007,
48, 5795; Cunha, S.; Bastos, R. M.; Silva, P. O.; Costa, G. A.
N.; Vencato, I., Lariucci, C.; Napolitano, H. B.; Oliveira, C.
M. A.; Kato, L.; Silva, C. C.; Menezes, D.; Vannier-Santos,
M. A.; Monatsh. Chem. 2007, 138, 111; Cunha S.; Silva, V.
C.; Napolitano, H. B.; Lariucci, C.; Vencato, I.; J. Braz. Chem.
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Acknowledgments
We acknowledge the financial support of Conselho
Nacional de Desenvolvimento Científico e Tecnológico/
CNPq, Fundação de Amparo à Pesquisa do Estado da
Bahia/FAPESB, and IFSC/USP and IF/UFF for the access
to the KappaCCD. We also thank CNPQ for fellowship to
C. C. O., and research fellowship to S. C.
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Submitted: July 22, 2010
Published online: October 26, 2010

J. Braz. Chem. Soc., Vol. 22, No. 3, S1-S11, 2011.
Printed in Brazil - ©2011 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Supplementary Information
SI
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
Silvio Cunha,*,a,c Caio C. Oliveiraa,c and José R. Sabinob
aInstituto de Química and cInstituto Nacional de Ciência e Tecnologia - INCT em Energia e
Ambiente, Universidade Federal da Bahia, Campus de Ondina, 40170-290 Salvador-BA, Brazil
bInstituto de Física, Universidade Federal de Goiás, CP 131, 74001-970 Goiânia-GO, Brazil
General information
Melting points were determined on a Microquímica MQAPF 301 hot plate apparatus and are uncorrected. Infrared
1
spectra were recorded as KBr discs on a FT-IR BOMEM MB100 instrument. NMR spectra were obtained for H at
300 MHz and for 13C at 75 MHz using a Varian Gemini 300 spectrometer. Chemical shifts are reported in ppm units
downfield from reference (internal TMS).
Table S1. Physical data for compounds 3a-j
o
o
3a: yellow solid, mp 128-129 C; IR (KBr)
n
3f: brown solid, mp 100-105 C; IR (KBr)
n
max/cm-1: 3300, 3072, 1727, 1632 1050;
max/cm-1: 2360, 1766, 1029, 990; H NMR
1
(CDCl3) d 3.63-3.66 (m, 4H), 3.78-3.81
(m, 5H), 4.71 (s, 2H); 13C NMR (CDCl3) d
171.41, 159.26, 72.80, 67.52, 66.17, 47.10.
1H NMR (CDCl3) d 3.82 (s, 3H) 4.88 (s,
2H), 6.81-6.88 (m, 3H), 7.03-7.08 (m, 2H)
7.13 (sl, 1H); 13C NMR (CDCl3) d 169.50,
160.01, 150.30, 126.95, 126.06, 121.29,
119.42, 111.61, 78.41, 67.70, 56.14.
3b: yellow solid, mp 165-167 oC; IR (KBr)
n
max/cm-1: 3204, 1745, 1637, 1179; 1H NMR
o
3g: green solid, mp 152-154 C (Condition
(DMSO-d6) 4.97 (s, 1H), 7.09 (t, J 7.2 Hz,
1H), 7.17 (d, J 7.2 Hz, 2H) 7.28 (t, J 7.2 Hz,
2H), 9.47 (s, 1H), 13C NMR (CDCl3) d
170.22, 162.16, 138.73, 129.85, 125.74,
123.05, 74.66, 67.99.
o
A), or yellow solid, 135-138 C (Condition
B); IR (KBr) nmax/cm-1: 3191, 3088, 2928,
1728, 1620, 1050; 1H NMR (CDCl3) d 6.79
(s, 1H) 4.86 (s, 2H), 6.97 (d, J 8.7 Hz, 2H),
7.30 (d, J 8.7 Hz, 2H), 7.13 (s, 1H); 13C NMR
(DMSO-d6/CDCl3) d 170.17, 161.09, 137.25,
130.26, 129.48, 124.44, 75.74, 67.84.
o
3c: brown solid, mp 146-148 C; IR (KBr)
n
max/cm-1: 3229, 3072, 1730, 1627, 1049;
1H NMR (DMSO-d6) d 2.19 (s, 3H) 4.91 (s,
2H), 7.07 (s, 4H), 9.36 (s, 1H); 13C NMR
(DMSO-d6) d 170.23, 162.37, 136.10,
135.22, 130.25, 123.41, 73.98, 67.83, 21.04.
o
3h: green solid, mp 149-151 C; IR (KBr)
n
max/cm-1: 3214, 3038, 1731, 1626, 1045;
1H NMR (DMSO-D6) d 4.82 (s, 2H), 7.25-
7.47 (m, 3H), 7.56-7.59 (m, 1H), 9.53 (s,
1H);13C NMR (DMSO-d6) d 169.95, 161.314,
134.33, 130.17, 129.88, 129.22, 128.53,
127.87, 73.49, 67.30.
o
3d: brown solid, mp 166-167 C; IR (KBr)
n
max/cm-1: 3227, 3042, 2933; 2836, 1713,
1611, 1036; 1H NMR (DMSO-d6) d 2.15 (s,
3H) 4.65 (s, 2H), 7.11-7.22 (m, 4H), 9.16 (s,
1H); 13C NMR (DMSO-d6) d 170.69, 162.91,
136.48, 135.23, 131.30, 127.92, 127.36,
127.17, 72.40, 67.57, 18.12.
o
3i: yellow solid, mp 166-169 C; IR (KBr)
n
max/cm-1: 3456, 3360, 3230, 3028, 1701,
1616, 1042; 1H NMR (CDCl3) 3.90 (sl, 2H),
4.67 (s, 2 H), 6.30 (sl, 1H), 6.77-6.85 (m, 2H),
7.05-7.08 (m, 1H), 7.16-7.21 (m, 1H); 13C
NMR (DMSO-d6) d 170.86, 163.82, 154.24,
128.90, 128.45, 122.44, 116.75, 116.22,
72.27, 67.62.
o
3e: green solid, mp 135-138 C; IR (KBr)
n
max/cm-1: 3175, 3067, 1723, 1631, 1025;
1H NMR (CDCl3) d 3.72 (s, 3H) 4.65 (s, 2H),
6.82 (d, J 10 Hz 2H), 6.85 (sl, 1H), 7.00 (d,
J 10 Hz 2H); 13C NMR (CDCl3) d 170.17,
161.74, 158.58, 129.73, 125.40, 115.16,
76.00, 67.18, 55.75.
o
3j: brown solid, mp 151-155 C; IR (KBr)
n
max/cm-1:3441,3218,1741,1609,1396,1030;
1H NMR (DMSO-d6) d 4.84 (s, 2H),7.51-7.63
(m, 4H), 7.89-7.92 (dd, J 6.9 Hz and J
2.7 Hz,1H), 7.98-8.02 (m, 2H); 13C NMR
(DMSO-d6) d 170.18, 162.49, 133.80,
133.17, 129.43, 128.20, 127.32, 126.70,
126.63, 125.55, 123.76, 122.83, 72.65, 67.19.
*e-mail: silviodc@ufba.br

S2
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
J. Braz. Chem. Soc.
Figure S1. Full1H NMR spectrum of compound 3a (CDCl3).
Figure S2. Full13C NMR spectrum of compound 3a (CDCl3).

Vol. 22, No. 3, 2011
Cunha et al.
S3
Figure S3. Full1H NMR spectrum of compound 3b (DMSO-d6).
Figure S4. Full13C NMR spectrum of compound 3b (DMSO-d6).

S4
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
J. Braz. Chem. Soc.
Figure S5. Full1H NMR spectrum of compound 3c (DMSO-d6).
Figure S6. Full13C NMR spectrum of compound 3c (DMSO-d6).

Vol. 22, No. 3, 2011
Cunha et al.
S5
Figure S7.Full1H NMR spectrum of compound 3d (DMSO-d6).
Figure S8. Full13C NMR spectrum of compound 3d (DMSO-d6).

S6
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
J. Braz. Chem. Soc.
Figure S9. Full1H NMR spectrum of compound 3e (CDCl3).
Figure S10. Full13C NMR spectrum of compound 3e (CDCl3).

Vol. 22, No. 3, 2011
Cunha et al.
S7
Figure S11. Full1H NMR spectrum of compound 3f (CDCl3).
Figure S12. Full13C NMR spectrum of compound 3f (CDCl3).

S8
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
J. Braz. Chem. Soc.
Figure S13. Full1H NMR spectrum of compound 3g (CDCl3).
Figure S14. Full13C NMR spectrum of compound 3g (CDCl3 /DMSO-d6).

Vol. 22, No. 3, 2011
Cunha et al.
S9
Figure S15. Full1H NMR spectrum of compound 3h (CDCl3).
Figure S16. Full13C NMR spectrum of compound 3h (CDCl3).

S10
Synthesis of 3-Bromotetronamides via Amination of 3,4-Dibromofuran-2(5H)-one
J. Braz. Chem. Soc.
Figure S17. Full1H NMR spectrum of compound 3i (CDCl3).
Figure S18. Full13C NMR spectrum of compound 3i (DMSO-d6).

Vol. 22, No. 3, 2011
Cunha et al.
S11
Figure S19. Full1H NMR spectrum of compound 3j (CDCl3).
Figure S20. Full13C NMR spectrum of compound 3j (CDCl3).