Bromination and azidation reactions of 2-styrylchromones. New syntheses of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles

Article abstract of DOI:10.1007/s00706-003-0125-y

The bromination of 2-styrylchromones, bearing electron neutral substituents, with two molar equivalents of piridinium tribromide gave 2-(2-aryl-1,2-dibromoethyl)chromones and 3-bromo-2-(2-aryl-1,2-dibromoethyl) chromones. The presence of electron-donating substituents on their B ring led to a mixture of compounds due to the higher reactivity of their C(2)=C(3) and C_α=C_β double bonds, whereas the strongly electron-withdrawing group hindered the bromination. The dehydrobromination of 2-(2-aryl-1,2-dibromoethyl)chromones with triethylamine gave a diastereomeric mixture of (E)- and (Z)-2-(α-bromostyryl)chromones. Some novel 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles have been obtained from the reactions of 2-(2-aryl-1,2-dibromoethyl)chromones, 2-(α-bromostyryl) chromones, and 2-styrylchromones with sodium azide. The reactions of 2-styrylchromones with sodium azide are more efficient, general, and constitute a one-pot synthetic method of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles allowing the preparation of 1,2,3-triazoles bearing either electron-donating or electron-withdrawing substituents in their aryl ring. The structure of all new compounds was established by extensive NMR spectroscopic studies. Springer-Verlag 2003.

Full text of DOI:10.1007/s00706-003-0125-y

Monatshefte f€ur Chemie 135, 293–308 (2004)
DOI 10.1007/s00706-003-0125-y
Bromination and Azidation Reactions of
2-Styrylchromones. New Syntheses of
4(5)-Aryl-5(4)-(2-chromonyl)-1,2,3-triazoles
1
1
Artur M. S. Silva1;ꢀ, Judite S. Vieira , Cristela M. Brito , Jose A. S.
´
3
1
2;ꢀ
2
´ ´ ´
Cavaleiro , Tamas Patonay , Albert Levai , and Jose Elguero
1
Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal
2
Department of Chemistry, University of Debrecen, P.O. Box 20, H-4010 Debrecen, Hungary
3
´
Instituto de Quımica Medica, c=Juan de la Cierva 3, 28006 Madrid, Spain
ꢀ
Received October 2, 2003; accepted October 9, 2003
Published online January 27, 2004 # Springer-Verlag 2003
Summary. The bromination of 2-styrylchromones, bearing electron neutral substituents, with two
molar equivalents of piridinium tribromide gave 2-(2-aryl-1,2-dibromoethyl)chromones and 3-
bromo-2-(2-aryl-1,2-dibromoethyl)chromones. The presence of electron-donating substituents on their
B ring led to a mixture of compounds due to the higher reactivity of their C(2)¼C(3) and Cꢀ¼Cꢁ
double bonds, whereas the strongly electron-withdrawing group hindered the bromination. The dehy-
drobromination of 2-(2-aryl-1,2-dibromoethyl)chromones with triethylamine gave a diastereomeric
mixture of (E)- and (Z)-2-(ꢀ-bromostyryl)chromones. Some novel 4(5)-aryl-5(4)-(2-chromonyl)-
1,2,3-triazoles have been obtained from the reactions of 2-(2-aryl-1,2-dibromoethyl)chromones,
2-(ꢀ-bromostyryl)chromones, and 2-styrylchromones with sodium azide. The reactions of 2-styryl-
chromones with sodium azide are more efficient, general, and constitute a one-pot synthetic method of
4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles allowing the preparation of 1,2,3-triazoles bearing either
electron-donating or electron-withdrawing substituents in their aryl ring. The structure of all new
compounds was established by extensive NMR spectroscopic studies.
Keywords. 2-Styrylchromones; Bromination; Dehydrobromination; Azidation; 1,2,3-Triazoles.
Introduction
1,2,3-Triazoles are widely studied nitrogen heterocycles [1] with numerous appli-
cations in organic synthesis and with extensive biological and agrochemical activ-
ities [1, 2]. However, very little is known about the synthesis and chemical and
biological properties of compounds having both chromone and 1,2,3-triazole moi-
eties. To our best knowledge, only a limited number of reports have been published
on the synthesis of 2-chromone-1,2,3-triazoles. The reaction of 2-cyanochromones
ꢀ
Corresponding authors. E-mail: arturs@dq.ua.pt and tpatonay@tigris.klte.hu

294
A. M. S. Silva et al.
with diazomethane has resulted in the formation of mixtures of isomeric deriva-
tives with the predominance of 2-methyl-4-(2-chromonyl)-1,2,3-triazoles [3–5].
French authors reported on anti-inflammatory, anticonvulsive, neurotoxic, and
anti-allergic effects of these compounds [5]. Recently Liu et al. published on the
synthesis of 2-phenyl-4-(substituted 2-chromonyl)-1,2,3-triazoles by the Baker-
Venkataraman rearrangement of 1,3-diketones obtained from 20-hydroxyacetophe-
nones and 2-phenyl-1,2,3-triazole-4-carboxylic acid [6].
Synthetic methods affording 1,2,3-triazoles are well documented and reviewed [1, 7]. A widely
used approach is based on one bond formation between nitrogen atoms, e.g., the reaction of ꢀ-
diazoketones with amines gives 1-substituted 1,2,3-triazoles while oxidative ring-closure of osa-
zone-type compounds results in the formation of 1-amino-1,2,3-triazole derivatives. The base-catalysed
condensation of compounds with activated methylene groups and azides provides another route.
However, the most popular method undoubtedly consists of the 1,3-dipolar cycloaddition of azide
to alkynes which is usually exploited to prepare 1-alkylated or arylated derivatives [1, 7–9]. Synthesis
of 1H-1,2,3-triazoles requires the addition of hydrazoic acid what is somewhat dangerous and needs an
activation by an electron-withdrawing group. Using benzyl, trimethylsilyl, or tributyltin azide and
deprotecting the formed intermediate can avoid this drawback. The addition of azide ion as anionic
dipole to alkynes may also offer a safer approach. Oxidative aromatisation of 1,2,3-triazolines also
leads to 1,2,3-triazoles but the formation of 1,2,3-triazolines by 1,3-dipolar cycloaddition of azides to
alkenes is usually a very slow reaction unless electron-withdrawing group or ring strain activates the
double bond. Alternatively, addition of azides to enol ethers or enamines followed by the elimination of
alcohols or secondary amines also provides an entry to 1,2,3-triazoles. A further version utilising the
addition of aryl and vinyl azides to ꢀ-keto phosphorus ylides and an immediate elimination of
triphenylphosphine oxide from the triazoline intermediates was published by L’abbꢀe et al. [10].
Several papers reported on the intramolecular dipolar cyloaddition in an
electron-deficient vinyl azide [11]. Based on the fact the chromone nucleus acts
asastronglyelectron-withdrawingmoietyandthatwehavedemonstratedthecapabil-
ity of the styryl double bond of 2-stryrylchromones 1 to react with diazomethane in
a 1,3-dipolar cycloaddition [12], the intramolecular ring-closure of 2-(ꢀ- or ꢁ-
azidostyryl)chromones seemed to be a promising way to prepare the hitherto
unknown 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles. In accordance with our ear-
lier studies [13] we deemed the needed azides available from various brominated
species of 2-stryrylchromones 1. In this paper we wish to report our results in the
field of bromination and azidation of 2-stryrylchromones [14].
Results and Discussion
Synthesis
Our first synthetic approach to synthesise 1,2,3-triazoles 7 was based on the reac-
tion of 2-(ꢀ-bromostyryl)chromones 5 and 6 with sodium azide. To prepare the
desired starting materials, 2-styrylchromone 1a was treated with pyridinium
tribromide (PTB) (1 equiv.) in acetic acid at room temperature (Scheme 1).
Preparative TLC of the obtained mixture afforded 3-bromo-2-styrylchromone
(4a), 2-(1,2-dibromo-2-phenylethyl)chromone (2a), and 3-bromo-2-(1,2-dibromo-
2-phenylethyl)chromone (3a) in low yields and with poor mass balance (ꢁ40%)
(Table 1, Entry 1). Using two molar equivalents of PTB followed by silica gel

Bromination and Azidation Reactions of 2-Styrylchromones
295
Scheme 1
Table 1. Conditions and yields of the bromination of 2-styrylchromones 1a–1f
ꢀ
Entry
Starting
material
Temp.
ꢂC
PTB
equiv.
Yield =%
2
3
4
5
1
2
3
4
5
6
7
1a
1a
1b
1c
1d
RT
RT
RT
RT
RT
RT
70
1
2
2
2
2
2
2
10
44
41
33
–
15
41
24
42
15
–
16
–
–
–
–
–
–
–
10
15
–
32
–
ꢀꢀ
1e
–
1e
30
16
26
ꢀ
ꢀꢀ
Yields refer to pure isolated material;
70% of 1e was recovered
column chromatography only the two brominated products 2a (44%) and 3a (41%)
were obtained (Table 1, Entry 2). When this procedure was applied to 2-styryl-
chromones 1b and 1c the dibrominated chromones 2b and 2c and tribrominated
compounds 3b and 3c were obtained again in good yields (Table 1, Entries 3, 4).
These results demonstrate that the reactivity of double bonds C(2)¼C(3) and

296
A. M. S. Silva et al.
Cꢀ¼Cꢁ is quite similar and their bromine addition takes place competitively leading
to dibromides 2 and A. However, dibromides A lose HBr very smoothly, presumably
in a reaction of E1 mechanism due to the evolvement of the highly stabilized carboca-
tion B. This elimination results in the formation of the 3-brominated product 4. Tri-
brominated chromone 3 may arise from either dibromide 2 or 3-bromochromone 4.
The 3JH-1 -H-2 values in bromides 2 and 3 verified their erythro relative configuration.
On the contrary, the bromination of 40-methoxy-2-styrylchromone 1d failed to
give any expected dibrominated product 2d, but 3-bromo-40-methoxy-2-styrylchro-
mone (4d, 10%), (Z)-40-methoxy-2-(ꢀ-bromostyryl)chromone (5d, 32%) together
with 3-bromo-2-[1,2-dibromo-2-(4-methoxyphenyl)ethyl]chromone (3d, 15%) were
obtained instead (Table 1, Entry 5). Other tested bromination methods (Br2 in
CCl4; NBS and benzoyl peroxide in CCl4) gave similar results. This data indicate
that in the presence of an electron-donating substituent in the B ring of 2-styryl-
chromones both C(2)¼C(3) and Cꢀ¼Cꢁ double bonds became more reactive.
Moreover, the enhanced cation-stabilizing capability of the methoxy substituent
facilitates the HBr elimination from intermediate 2d.
0
0
The bromination of 40-nitro-2-styrylchromone (1e) with two molar equivalents
of PTB at room temperature for 10 days gave 3-bromo-40-nitro-2-styrylchromone
(4e) in 15% yield only while 70% of the unreacted starting material 1e was recov-
ered (Table 1, Entry 6). This indicates that C(2)¼C(3) and Cꢀ¼Cꢁ double bonds of
2-styrylchromones bearing electron-withdrawing substituents in their B ring
became less reactive in consequence of the decreased ꢂ-electron density. When
the bromination of 1e was repeated at 70ꢂC for 7 hours 2-[1,2-dibromo-2-(4-nitro-
phenyl)ethyl]chromone (2e, 30%), 3-bromo-2-[1,2-dibromo-2-(4-nitrophenyl)
ethyl]chromone (3e, 16%), and (Z)-40-nitro-2-(ꢀ-bromostyryl)chromone (5e,
26%) were obtained (Table 1, Entry 7).
The attempted bromination of 5-benzyloxy-2-styrylchromone (1f) with two
molar equivalents of PTB at room temperature for 9 days gave a mixture of bro-
minated 2-styrylchromone derivatives (vide Experimental). The benzyloxy group
was cleaved probably by the HBr formed in the elimination reaction and the posi-
tions 6 and=or 8 activated by the hydroxy group have been brominated. Similar
nuclear bromination of an activated ring A is well-documented [15].
The next step in our first approach to 1,2,3-triazoles 7 was the dehydrobromi-
nation of 2-(2-aryl-1,2-dibromoethyl)chromones 2. The treatment of 2a–2c with a
high excess of triethylamine in refluxing toluene gave both (Z)-2-(ꢀ-bromostyryl)
chromones 5a–5c and (E)-2-(ꢀ-bromostyryl)chromones 6a–6c, the more stable
(Z)-isomers being the major products (65–89%) in each case (Scheme 2). The
formation of both diastereomers in such elimination is not an unprecedented reac-
tion, elimination from compounds with analogous structure such as erythro-chal-
cone dibromides [16], methyl erythro-2,3-dibromo-3-phenylpropanoate [17], or
2-bromo-3-methoxy-1,3-diphenylpropan-1-ones [18] led to a similar E=Z mixture
via a likely E1cB mechanism.
In the third step the treatment of (Z)-2-(ꢀ-bromostyryl)chromones 5a–5c with
an excess of sodium azide in DMF at 120ꢂC followed by acidic work-up afforded
the expected 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles 7a–7c (61–83%)
(Scheme 2). 1,2,3-Triazole 7a was also obtained from the diastereomeric (E)-2-
(ꢀ-bromostyryl)chromone (6a) under the same conditions.

Bromination and Azidation Reactions of 2-Styrylchromones
297
Scheme 2
This synthetic protocol to prepare 1,2,3-triazoles 7a–7c constitutes an improve-
ment to the previous one disclosed in our preliminary communication where the
treatment of bromides 5 with sodium azide in refluxing DMF was reported to give
1,2,3-triazoles 7 in poorer (38–40%) yields and contaminated with tetrazole deri-
vatives (10–12%) [14]. By decreasing the reaction temperature (153ꢂC ! 120ꢂC)
and increasing the excess of sodium azide (from 2 to 5 molar equivalents) the
formation of by-products was completely eliminated and the desired 1,2,3-triazoles
7a–7c are now available in better yields. The formation of these compounds must
involve the transformation of bromides 5 into ꢀ- and ꢁ-azidovinyl compounds, by
the well-documented addition-substitution-elimination pathway [19], which may
cyclize to the obtained triazoles 7a–7c. Our attempts to detect some intermedia-
tes, by performing the synthesis of triazole 7a at lower temperatures, were
unsuccessful.
Taking into account the nucleophilic character of the azide ion, the mechanism
of the dehydrobromination and also the problems arising from the formation of
both (E)- and (Z)-diastereomers in these reactions we tried to react 2-(2-aryl-1,2-
dibromoethyl)chromones 2a–2c with sodium azide in DMF at 120ꢂC. These reac-
tions followed by an acidic work-up yielded the expected triazoles 7a–7c in good
yields (54–73%) as well, which was comparable with those of the treatment of ꢀ-
bromostyryl compounds 5. Treatment of 2-(1,2-dibromo-2-phenylethyl)chromone
2a with sodium azide in DMF at lower temperature (ꢁ60ꢂC) gave mainly (Z)-2-(ꢀ-
bromostyryl)chromone 5a. This indicates that the reaction involves the transforma-
tion of dibromo derivatives 2 into ꢀ-bromostyryl compounds 5, by the elimination

298
A. M. S. Silva et al.
of hydrogen bromide assisted by azide ion, which are transformed in the obtained
1,2,3-triazoles 7 by the reaction with sodium azide (vide supra).
Due to the mesomeric effect of the carbonyl group Cꢀ¼Cꢁ double bond of 2-
styrylchromones could be considered as an ‘‘activated’’ double bond to participate
in a cycloaddition reaction as a dipolarophile [1]. It was also pointed out that
sluggish addition of azide to alkenes could be greatly improved by using protic
or dipolar aprotic media [9]. Moreover, cycloadditions with participation of anionic
dipoles were found to be greatly influenced by the polarity of the solvent. The
increased reactivity of the anions poorly solvated in dipolar aprotic media consid-
erably accelerates the cycloadditions [9]. Keeping these facts in mind, we essayed
the reaction of 2-styrylchromones 1a–1e with sodium azide in DMF at 120ꢂC
followed by treatment with acid. We found that these reactions gave directly
4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles 7a–7e in good yields (47–65%), i.e.
not only 1,3-dipolar cycloaddition but spontaneous oxidation of the triazoline
intermediate took place in a one-pot reaction (Scheme 2). This procedure renders
possible to prepare 1,2,3-triazoles 7a–7e bearing either electron-withdrawing or
electron-donating substituents in the aryl ring of their styryl unit in one step. By
comparing the yields of products 7, this direct approach seems to be more effective
in the case of chromones with electron-withdrawing groups in position 40. The
reaction of 2-styrylchromone 1a with sodium azide in DMF at lower temperatures
(60–80ꢂC) also gave 1,2,3-triazole 7a but in lower yields, no intermediates were
detected.
When 5-benzyloxy-2-styrylchromone 1f was reacted with sodium azide in DMF
at 120ꢂC followed by treatment with hydrochloric acid 1,2,3-triazoles 7f (21%) and
7g (25%) were obtained (Scheme 3). The formation of 7g can be explained in terms
of the cleavage of the benzyloxy group by hydrochloric acid during work-up.
NMR Spectroscopy
2-Styrylchromones and Intermediates
The main features of the NMR spectra of 2-(2-aryl-1,2-dibromoethyl)chromone
2a–2c are the proton and carbon resonances of their ethylenic bridge. C-10 and
C-20 resonances were assigned by 1D selective INEPT [20]: upon irradiation of H-
3 (a singlet at ꢃ ¼ 6.51 ppm) the resonances of C-10 (ꢃ ¼ 123.9–124.0 ppm), C-2
(ꢃ ¼ 162.3–162.7 ppm), and C-20 (ꢃ ¼ 50.4–50.6 ppm) were observed. The reso-
Scheme 3

Bromination and Azidation Reactions of 2-Styrylchromones
299
nance at ꢃ ¼ 50.6–50.7 ppm was then attributed to C-10. The analysis of the HET-
COR spectra allowed the assignment of H-10 and H-20 at ꢃ ¼ 5.20–5.25 and 5.53–
5.56 ppm.
1
The H NMR spectra of 2-(2-aryl-1,2-dibromoethyl)-3-bromochromones 3a–
3e present two doublets at ꢃ ¼ 6.03–6.10 and 5.58–5.67 ppm, corresponding to H-
10 and H-20. Comparing the spectra of 3a–3e with those of 2a–2c one can conclude
on the bromination at C-3, since their typical H-3 singlet is absent. The confirma-
tion of the H-10 and H-20 resonances and the assignments of some quaternary
carbons were also made by 1D selective INEPT [20]: upon irradiation of H-10
the signals of C-100, C-3, and C-20 were observed, whereas the irradiation of H-
20 led to the appearance of C-2, C-100, and C-200,600.
The NMR spectra of both 2-(ꢀ-bromostyryl)chromone diastereomers 5a–5c
and 6a–6c are similar, but there are some important differences in the chemical
shifts of Hꢁ and Cꢁ. In the case of the (E)-isomers 6a–6c ring B and chromone
moiety are not coplanar anymore due to steric hindrance. As a consequence of this
there is no (or only limited) conjugation between the ꢀ,ꢁ,ꢄ,ꢃ-unsaturated system
and ring B, hence the resonance of their Cꢁ atoms appear at higher frequency
values (ꢃ ¼ 138.7–140.1 ppm) than those of the (Z) diastereomers 5a–5c
(ꢃ ¼ 132.8–135.2 ppm). Due to the referred non-coplanarity both Hꢁ (ꢃ ¼ 7.40–
7.46 ppm) and H-3 (ꢃ ¼ 6.42–6.44 ppm) of (E)-isomers 6a–6c appear at lower
frequency values than those of the (Z)-isomers 5a–5c (Hꢁ, ꢃ ¼ 8.05–8.12 ppm;
H-3, ꢃ ¼ 6.98–7.01 ppm).
The assignments of the other 2-styrylchromone derivatives proton and carbon
resonances were based on the analysis of HSQC (or HETCOR in some cases) and
HMBC spectra and also on our experience with the structural characterisation of
this type of compounds [22].
1,2,3-Triazole Derivatives
The NMR spectra of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles 7a–7e were
recorded in DMSO-d6 with some drops of trifluoroacetic acid in order to accelerate
the prototropy. In the absence of acid these spectra showed a mixture of tautomers.
Comparing the NMR spectra of 1,2,3-triazoles 7a–7e with those of the 2-styryl-
chromone precursors it was possible to observe the disappearance of their vinylic
protons, whereas H-30 resonance still appeared as a singlet at ꢃ ¼ 6.60–6.84 ppm.
The assignments of the carbon atoms of the 1,2,3-triazole ring of 7a–7e were based
on the analysis of their HMBC spectra; there is correlation between H-30 and the
signals of C-4 (ꢃ ¼ 134.7–136.8 ppm) and also between H-200,600 and C-5
(ꢃ ¼ 141.6–149.6 ppm).
Conclusion
The bromination of 2-styrylchromones with PTB was studied and revealed to be
quite sensitive to the substituents of their A and B rings. The presence of electron-
donating substituents on their B ring led to a mixture of compounds due to the
higher reactivity of their C(2)¼C(3) and Cꢀ¼Cꢁ double bonds, whereas the
strongly electron-withdrawing group hindered the bromination.

300
A. M. S. Silva et al.
The reactions of 2-(2-aryl-1,2-dibromoethyl)chromones 2a–2c, 2-(ꢀ-bromo-
styryl)chromones 5a–5c and 6a–6c with sodium azide were found to give some
novel 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles 7a–7c. However, the reaction of
2-styrylchromones 1a–1f with sodium azide proved to be the more efficient, gen-
eral, and one-pot synthetic method of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles
7a–7g allowing the preparation of 1,2,3-triazoles bearing either electron-donating
or electron-withdrawing substituents in their aryl ring.
Experimental
Melting points were determined on a Reichert Thermovar apparatus fitted with a microscope and are
uncorrected. NMR spectra were recorded on Bruker DRX 300 spectrometer (300.13 MHz for 1H and
1
75.47 MHz for 13C), with CDCl3 as solvent if not stated otherwise; internal standard was TMS. H
Assignments were made using 2D gCOSY and NOESY (mixing time of 800ms) experiments, while
13C assignments were made using 2D gHSQC (or HETCOR) and gHMBC experiments (long range
C=H coupling constants were optimised to 7 Hz). Mass spectra (EI, 70 eV) were measured on VG
Autospec Q and M mass spectrometers. Elemental analyses were obtained with a LECO 932 CHN
analyser; the results were in accord with the calculated values, as well as the high resolution MS.
Preparative thin layer chromatography was carried out with Riedel silica gel 60 DGF254, and column
chromatography using Merck silica gel 60, 70–230 mesh.
Halogenation of 2-Styrylchromones 1a–1f
Method A. 5.15g of PTB (16.1 mmol) were added to a solution of the appropriate 2-styrylchromone
1a–1f [12, 21] (8.06 mmol) in 500 cm3 of acetic acid. The mixture was stirred at room temperature
(1a–1c: 32 h, 1d: 1 wk, 1e: 10 d, 1f: 9 d) then poured into 200 cm3 of H2O and 100 g of ice. The
obtained solid was filtered off and taken up in 100 cm3 of CHCl3. The organic layer was washed with
H2O (2ꢃ 200 cm3), dried (Na2SO4), and evaporated.
When starting with chromones 1a–1c the obtained residue was purified by silica gel column
chromatography (using a 1:9 mixture of light petroleum:CH2Cl2 as eluent). The first compound eluted
was 2-(2-aryl-1,2-dibromoethyl)-3-bromochromone 3a–3c (24–42%) followed by 2-(2-aryl-1,2-dibro-
moethyl)chromone 2a–2c (33–44%).
When starting with 1d the obtained residue was purified by preparative thin layer chromatography
(using a 1:1 mixture of light petroleum:CH2Cl2 as eluent). After several elutions, four very close spots
were collected; the first one was 3d (15%), followed by 4d (10%), and 5d (32%). After removal of the
solvent each residue was recrystallised from ethanol.
When starting with 1e the obtained crude product was purified by column chromatography (using
CH2Cl2 as eluent). The compound eluted first was the starting material 1e (70%), followed by 4e
(15%). After removal of the solvent each residue was recrystallised from ethanol.
When starting with 1f, the obtained residue was purified by preparative thin layer chromatography
(using a 1:1 mixture of light petroleum:CH2Cl2 as eluent). After several elutions, four very close spots
were collected; the first one was 6,8-dibromo-5-hydroxy-2-styrylchromone (59%), followed by 8-
bromo-5-hydroxy-2-styrylchromone (4%), 6-bromo-5-hydroxy-2-styrylchromone (2%), and 3,8-
dibromo-2-(1,2-dibromo-2-phenylethyl)-5-hydroxychromone (10%). After removal of the solvent each
residue was recrystallised from ethanol.
Method B – (only for 40-nitro-2-styrylchromone 1e). 0.68 g of PTB (2.13mmol) were added to a
solution of 0.31 g of 1e (1.07 mmol) in 200cm3 of acetic acid. The mixture was heated (70ꢂC) for 7
hours and then poured into 200 cm3 of H2O and 100 g of ice. The obtained solid was filtered off and
taken up in 100 cm3 of chloroform. The organic layer was washed with H2O (2ꢃ 200 cm3), dried
(Na2SO4), and then evaporated. The obtained residue was purified by thin layer chromatography (using

Bromination and Azidation Reactions of 2-Styrylchromones
301
CH2Cl2 as eluent). After several elutions, three very close spots were collected; the first one 3e
(181 mg, 16%), followed by 5e (206 mg, 26%), and 2e (290 mg, 30%). After removal of the solvent
each residue was recrystallised from ethanol.
2-(1,2-Dibromo-2-phenylethyl)chromone (2a, C17H12Br2O2)
1
Yield: 1.45 g (44%); mp 159–161ꢂC (EtOH); H NMR: ꢃ ¼ 5.25 (d, J ¼ 11.6Hz, H-10), 5.56 (d,
J ¼ 11.6Hz, H-20), 6.51 (s, H-3), 7.40–7.54 (m, H-6 and H-200,300,400,500,600), 7.61 (d, J ¼ 7.8 Hz, H-
8), 7.76 (dt, J ¼ 1.7 and 7.8 Hz, H-7), 8.23 (dd, J ¼ 1.7 and 7.8 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 50.4 (C-
20), 50.6 (C-10), 111.6 (C-3), 118.2 (C-8), 123.9 (C-10), 125.7 (C-6), 125.8 (C-5), 127.9 (C-200,600),
129.5 (C-300,500), 129.0 (C-400), 134.3 (C-7), 138.1 (C-100), 156.2 (C-9), 162.6 (C-2), 178.0 (C-4) ppm;
EI-MS: m=z (%) ¼ [410 (1), 408 (3), 406 (1), Mþꢄ], 329 (74), 327 (78), 326 (77), 325 (65), 311 (29),
247 (100), 218 (21), 189 (24), 127 (35), 121 (36), 109 (17), 92 (36), 77 (28).
3-Bromo-2-(1,2-dibromo-2-phenylethyl)chromone (3a, C17H11Br3O2)
1
Yield: 1.61 g (41%); mp 200–202ꢂC (EtOH); H NMR: ꢃ ¼ 5.61 (d, J ¼ 11.6 Hz, H-20), 6.10 (d,
J ¼ 11.6Hz, H-10), 7.42–7.53 (m, H-6 and H-300,400,500), 7.56 (dd, J ¼ 1.8 and 8.0 Hz, H-200,600), 7.64
(d, J ¼ 8.0 Hz, H-8), 7.80 (dt, J ¼ 1.6 and 8.0 Hz, H-7), 8.28(dd, J ¼ 1.6 and 8.0Hz, H-5) ppm; 13C NMR:
ꢃ ¼ 49.1 (C-10), 50.1 (C-20), 110.9 (C-3), 117.9 (C-8), 121.9 (C-10), 126.2 (C-6), 126.6 (C-5), 128.0 (C-
200,600), 129.1 (C-300,500), 129.6 (C-400), 134.7 (C-7), 137.7 (C-100), 155.1 (C-9), 159.8 (C-2), 172.4 (C-4)
ppm; EI-MS: m=z (%) ¼ [490 (3), 488 (7), 486 (7), 484 (3), Mþꢄ], 409 (28), 407 (38), 405 (27), 328 (30),
326 (30), 247 (93), 218 (18), 189 (23), 169 (19), 127 (34), 109 (17), 92 (20), 77 (19), 63 (21).
2-[1,2-Dibromo-2-(4-chlorophenyl)ethyl]chromone (2b, C17H11Br2ClO2)
1
Yield: 1.47 g (41%); mp 161–162ꢂC (EtOH); H NMR: ꢃ ¼ 5.20 (d, J ¼ 11.6Hz, H-10), 5.53 (d,
J ¼ 11.6Hz, H-20), 6.51 (s, H-3), 7.40–7.49 (m, H-6 and H-200,300,500,600), 7.59 (d, J ¼ 8.1 Hz, H-8),
7.75 (ddd, J ¼ 1.6, 7.8, and 8.1 Hz, H-7), 8.23 (dd, J ¼ 1.6 and 7.9 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 50.4
(C-20), 50.6 (C-10), 111.7 (C-3), 118.1 (C-8), 124.0 (C-10), 125.8 (C-6), 125.9 (C-5), 129.31 and
129.34 (C-200,600 and C-300,500), 134.3 (C-7), 135.4 (C-100), 136.7 (C-400), 156.2 (C-9), 162.3 (C-2), 177.9
(C-4) ppm; EI-MS: m=z (%) ¼ [446 (1), 444 (5), 442 (8), 440 (3), Mþꢄ], 365 (43), 363 (79), 361 (73),
283 (71), 281 (100), 265 (73), 247 (53), 218 (31), 189 (38), 162 (66), 127 (67), 109 (62), 92 (59), 75
(26), 63 (37).
3-Bromo-2-[1,2-dibromo-2-(4-chlorophenyl)ethyl]chromone (3b, C17H10Br3ClO2)
1
Yield: 1.01 g (24%); mp 190–192ꢂC (EtOH); H NMR: ꢃ ¼ 5.58 (d, J ¼ 11.6Hz, H-20), 6.03 (d,
J ¼ 11.6Hz, H-10), 7.42–7.53 (m, H-6 and H-200,300,500,600), 7.62 (d, J ¼ 8.1Hz, H-8), 7.80 (dt,
13
J ¼ 1.6 and 8.1 Hz, H-7), 8.28 (dd, J ¼ 1.6 and 8.0 Hz, H-5) ppm; C NMR: ꢃ ¼ 49.0 (C-10), 49.1
(C-20), 111.0 (C-3), 117.8 (C-8), 121.9 (C-10), 126.3 (C-6), 126.6 (C-5), 129.3 (C-300,500), 129.4 (C-
200,600), 134.7 (C-7), 135.5 (C-400), 136.3 (C-100), 155.1 (C-9), 159.4 (C-2), 172.3 (C-4) ppm; EI-MS:
m=z (%) ¼ [526 (1), 524 (5), 522 (9), 520 (8), 518 (3), Mþꢄ], 445 (17), 443 (57), 441 (63), 439 (40),
364 (23), 362 (62), 360 (55), 283 (60), 281 (100), 245 (51), 218 (37), 205 (29), 189 (37), 161 (28), 126
(52), 109 (40), 92 (36), 75 (25), 63 (29).
2-[1,2-Dibromo-2-(4-methylphenyl)ethyl]chromone (2c, C18H14Br2O2)
1
Yield: 1.13 g (33%); mp 155–157ꢂC (EtOH); H NMR: ꢃ ¼ 2.40 (s, 400-CH3), 5.25 (d, J ¼ 11.6Hz,
H-10), 5.55 (d, J ¼ 11.6Hz, H-20), 6.51 (s, H-3), 7.25 (d, J ¼ 7.7 Hz, H-300,500), 7.41 (d, J ¼ 7.7 Hz,

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H-200,600), 7.46 (ddd, J ¼ 1.0, 7.6, and 7.8Hz, 6-H), 7.60 (d, J ¼ 7.9 Hz, 8-H), 7.75 (ddd, J ¼ 1.7, 7.6,
and 7.9 Hz, H-7), 8.23 (dd, J ¼ 1.7 and 7.8 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 21.4 (400-CH3), 50.6 (C-20),
50.7 (C-10), 111.6 (C-3), 118.2 (C-8), 124.0 (C-10), 125.7 (C-6), 125.9 (C-5), 127.8 (C-200,600), 129.8
(C-300,500), 134.3 (C-7), 135.2 (C-100), 139.7 (C-400), 156.2 (C-9), 162.7 (C-2), 178.0 (C-4) ppm; EI-MS:
m=z (%) ¼ [424 (5), 422 (10), 420 (5), Mþꢄ], 343 (61), 341 (62), 261 (100), 245 (44), 218 (21), 169
(21), 142 (44), 127 (5), 115 (35), 92 (25), 63 (25).
3-Bromo-2-[1,2-dibromo-2-(4-methylphenyl)ethyl]chromone (3c, C18H13Br3O2)
Yield: 1.70 g (42%); mp 193–195ꢂC (EtOH); 1H NMR: ꢃ ¼ 2.40 (s, 400-CH3), 5.61 (d, J ¼ 11.6Hz, H-
20), 6.10 (d, J ¼ 11.6Hz, H-10), 7.27 (d, J ¼ 8.0 Hz, H-300,500), 7.44 (d, J ¼ 8.0 Hz, H-200,600), 7.50 (t,
J ¼ 7.8 Hz, H-6), 7.63 (d, J ¼ 8.1 Hz, H-8), 7.79 (ddd, J ¼ 1.4, 7.8, and 8.1Hz, H-7), 8.28 (dd, J ¼ 1.4
and 7.8 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 21.4 (400-CH3), 49.3 (C-10), 50.3 (C-20), 110.8 (C-3), 117.9 (C-8),
121.9 (C-10), 126.2 (C-6), 126.6 (C-5), 127.9 (C-200,600), 129.8 (C-300,500), 134.69 (C-7), 134.74 (C-100),
139.8 (C-400), 155.1 (C-9), 159.9 (C-2), 172.4 (C-4) ppm; EI-MS: m=z (%) ¼ [502 (1), 500 (1), Mþꢄ],
342 (45), 340 (46), 261 (100), 246 (19), 218 (21), 189 (10), 139 (16), 115 (28), 92 (11), 63 (15).
3-Bromo-2-[1,2-dibromo-2-(4-methoxyphenyl)ethyl]chromone (3d, C18H13Br3O3)
Yield: 469 mg (15%); mp 173–175ꢂC (EtOH); 1H NMR: ꢃ ¼ 3.86 (s, 400-OCH3), 5.61 (d, J ¼ 11.6Hz,
H-20), 6.09 (d, J ¼ 11.6Hz, H-10), 6.98 (d, J ¼ 8.8 Hz, H-300,500), 7.48 (d, J ¼ 8.8 Hz, H-200,600), 7.50
(ddd, J ¼ 1.1, 7.8, and 8.2 Hz, H-6), 7.63 (d, J ¼ 8.1 Hz, H-8), 7.79 (ddd, J ¼ 1.6, 7.8, and 8.1 Hz, H-7),
8.28 (dd, J ¼ 1.6 and 8.2 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 49.5 (C-10), 50.5 (C-20), 55.4 (400-OCH3), 110.8
(C-3), 114.4 (C-300,500), 117.9 (C-8), 121.9 (C-10), 126.2 (C-6), 126.6 (C-5), 129.4 (C-200,600), 129.7 (C-
100), 134.7 (C-7), 155.1 (C-9), 159.9 (C-2), 160.4 (C-400), 172.4 (C-4) ppm; FABþ-MS: m=z (%) ¼ [518
(1), 516 (1), Mþꢄ], 460 (100), 443 (21), 357 (29), 348 (13).
3-Bromo-40-methoxy-2-styrylchromone (4d, C18H13BrO3)
Yield 287.7mg (71%); mp 168–169ꢂC (EtOH); 1H NMR: ꢃ ¼ 3.87 (s, 40-OCH3), 6.96 (d, J ¼ 8.8 Hz, H-
30,50), 7.35 (d, J ¼ 16.1Hz, H-ꢀ), 7.41 (ddd, J ¼ 0.9, 7.5, and 7.8 Hz, H-6), 7.53 (d, J ¼ 8.0Hz, H-8), 7.61
(d, J ¼ 8.8Hz, H-20,60), 7.68 (d, J ¼ 16.1Hz, H-ꢁ), 7.70 (ddd, J ¼ 1.7, 7.5, and 8.0 Hz, H-7), 8.23 (dd,
J ¼ 1.7 and 7.8 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 55.5 (40-OCH3), 109.0 (C-3), 114.6 (C-30,50), 116.8 (C-ꢀ),
117.5 (C-8), 122.1 (C-10), 125.3 (C-6), 126.4 (C-5), 127.7 (C-10), 129.8 (C-20,60), 134.0 (C-7), 139.4 (C-
ꢁ), 154.9 (C-9), 158.9 (C-2), 161.5 (C-40), 172.8 (C-4) ppm; EI-MS: m=z (%) ¼ [358 (51), 356 (50),
M
þꢄ], 277 (100), 262 (39), 234 (50), 205 (34), 193 (16), 178 (15), 127 (9), 114 (32), 92 (19), 63 (26).
(Z)-40-Methoxy-2-(ꢀ-bromostyryl)chromone (5d, C18H13BrO3)
Yield: 921 mg (32%); mp 147–149ꢂC (EtOH); 1H NMR: ꢃ ¼ 3.88 (s, 40-OCH3), 6.98 (s, H-3), 6.99 (d,
J ¼ 8.8 Hz, H-30,50), 7.42 (ddd, J ¼ 0.9, 7.4, and 8.0 Hz, H-6), 7.54 (dd, J ¼ 0.9 and 8.1 Hz, H-8), 7.71
(ddd, J ¼ 1.7, 7.4, and 8.1 Hz, H-7), 7.90 (d, J ¼ 8.8Hz, H-20,60), 8.05 (s, H-ꢁ), 8.21 (dd, J ¼ 1.7 and
8.0 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 55.4 (40-OCH3), 110.8 (C-ꢀ), 110.9 (C-3), 114.0 (C-30,50), 117.8 (C-8),
123.6 (C-10), 125.3 (C-6), 125.8 (C-5), 126.8 (C-10), 132.2 (C-20,60), 134.1 (C-7), 134.7 (C-ꢁ), 156.0 (C-
9), 160.7 (C-2), 160.9 (C-40), 178.8 (C-4) ppm; EI-MS: m=z (%) ¼ [358 (23), 356 (23), Mþꢄ], 318 (100),
293 (15), 277 (71), 262 (23), 249 (17), 234 (36), 137 (89), 121 (72), 109 (34), 92 (40), 77 (59), 63 (33).
2-[1,2-Dibromo-2-(4-nitrophenyl)ethyl]chromone (2e, C17H11Br2NO4)
1
Yield: 290 mg (30%); mp 216–218ꢂC (EtOH); H NMR: ꢃ ¼ 5.23 (d, J ¼ 11.6Hz, H-10), 5.62 (d,
J ¼ 11.6Hz, H-20), 6.54 (s, H-3), 7.48 (ddd, J ¼ 0.9, 7.6, and 7.8 Hz, H-6), 7.60 (d, J ¼ 7.9 Hz, H-8),

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303
7.72 (d, J ¼ 8.8 Hz, H-200,600), 7.77 (ddd, J ¼ 1.7, 7.6, and 7.9 Hz, H-7), 8.24 (dd, J ¼ 1.7 and 7.8 Hz, H-
5), 8.32 (d, J ¼ 8.8Hz, H-300,500) ppm; 13C NMR: ꢃ ¼ 48.0 (C-20), 49.6 (C-10), 111.9 (C-3), 118.1 (C-8),
123.9 (C-10), 124.3 (C-300,500), 125.86 (C-6), 125.91 (C-5), 129.1 (C-200,600), 134.4 (C-7), 144.9 (C-100),
148.2 (C-400), 156.1 (C-9), 161.6 (C-2), 177.7 (C-4) ppm; EI-MS: m=z (%) ¼ [455 (8), 453 (14), 451
(8), Mþꢄ], 374 (43), 372 (47), 356 (15), 292 (100), 276 (43), 246 (62), 218 (31), 189 (33), 121 (51),
92 (60).
3-Bromo-2-[1,2-dibromo-2-(4-nitrophenyl)ethyl]chromone (3e, C17H10Br3NO4)
1
Yield: 181 g (16%); mp 220–224ꢂC (EtOH); H NMR: ꢃ ¼ 5.67 (d, J ¼ 11.6Hz, H-20), 6.06 (d,
J ¼ 11.6Hz, H-10), 7.53 (ddd, J ¼ 1.0, 7.4, and 8.1Hz, H-6), 7.64 (d, J ¼ 8.1 Hz, H-8), 7.75 (d,
J ¼ 8.8 Hz, H-200,600), 7.82 (ddd, J ¼ 1.7, 7.4, and 8.1 Hz, H-7), 8.29 (dd, J ¼ 1.7 and 8.1 Hz, H-5),
13
8.34 (d, J ¼ 8.8 Hz, H-300,500) ppm; C NMR: ꢃ ¼ 47.7 (C-10), 48.3 (C-20), 111.3 (C-3), 117.8 (C-8),
121.9 (C-10), 124.3 (C-300,500), 126.4 (C-6), 126.7 (C-5), 129.2 (C-200,600), 134.8 (C-7), 144.5 (C-100),
148.3 (C-400), 155.1 (C-9), 158.8 (C-2), 172.1 (C-4) ppm; EI-MS: m=z (%) ¼ [535 (2), 533 (6), 531 (6),
529 (2), Mþꢄ], 452 (16), 454 (10), 450 (10), 373 (59), 371 (59), 292 (73), 245 (100), 218 (40), 189 (44),
126 (33), 109 (12), 92 (41).
3-Bromo-40-nitro-2-styrylchromone (4e, C17H10BrNO4)
1
Yield: 59.7mg (15%); mp 260–262ꢂC (EtOH); H NMR (35ꢂC): ꢃ ¼ 7.47 (ddd, J ¼ 0.9, 7.2, and
8.0 Hz, H-6), 7.58 (d, J ¼ 8.0 Hz, H-8), 7.65 (d, J ¼ 15.9Hz, H-ꢀ), 7.76 (ddd, J ¼ 1.6, 7.2 and 8.0Hz,
H-7), 7.77 (d, J ¼ 15.9Hz, H-ꢁ), 7.81 (d, J ¼ 8.8 Hz, H-20,60), 8.27 (dd, J ¼ 1.6 and 8.0Hz, H-5), 8.32
(d, J ¼ 8.8 Hz, H-30,50) ppm; 13C NMR (35ꢂC): ꢃ ¼ 112.4 (C-3), 117.6 (C-8), 122.1 (C-10), 123.6 (C-
ꢀ), 124.4 (C-30,50), 125.7 (C-6), 126.6 (C-5), 128.5 (C-20,60), 134.4 (C-7), 136.4 (C-ꢁ), 141.0 (C-10),
148.5 (C-40), 154.9 (C-9), 157.2 (C-2), 172.6 (C-4) ppm; EI-MS: m=z (%) ¼ [373 (55), 371 (55), Mþꢄ],
292 (73), 245 (100), 234 (15), 218 (41), 205 (15), 189 (40), 126 (34), 109 (9), 92 (41), 63 (18).
(Z)-40-Nitro-2-(ꢀ-bromostyryl)chromone (5e, C17H10BrNO4)
Yield: 206 mg (26%); mp 228–230ꢂC (EtOH); 1H NMR (35ꢂC): ꢃ ¼ 7.01 (s, H-3), 7.44 (ddd, J ¼ 1.0,
7.7, and 7.8 Hz, H-6), 7.54 (d, J ¼ 7.8Hz, H-8), 7.73 (ddd, J ¼ 1.7, 7.7, and 7.8 Hz, H-7), 7.94 (d,
J ¼ 9.0 Hz, H-20,60), 8.12 (s, H-ꢁ), 8.22 (dd, J ¼ 1.7 and 7.8 Hz, H-5), 8.31 (d, J ¼ 9.0 Hz, H-30,50) ppm;
13C NMR (35ꢂC): ꢃ ¼ 112.5 (C-3), 117.7 (C-ꢀ), 117.8 (C-8), 123.7 (C-10), 123.7 (C-30,50), 125.7 (C-
5), 125.9 (C-6), 130.6 (C-20,60), 132.8 (C-ꢁ), 134.4 (C-7), 140.8 (C-100), 148.0 (C-40), 156.0 (C-9),
159.3 (C-2), 178.3 (C-4) ppm; EI-MS: m=z (%) ¼ [373 (14), 371 (14), Mþꢄ], 354 (27), 292 (100), 246
(66), 218 (22), 189 (33), 121 (41), 92 (44).
6,8-Dibromo-5-hydroxy-2-styrylchromone
Yield: 2.01 g (59%); mp 241–243ꢂC (Ref. [15] 241–243ꢂC).
8-Bromo-5-hydroxy-2-styrylchromone
Yield: 110.6 mg (4%); mp 175–177ꢂC (Ref. [15] 175–178ꢂC).
6-Bromo-5-hydroxy-2-styrylchromone
Yield: 56mg (2%); mp 222–225ꢂC (Ref. [15] 223–225ꢂC).

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3,8-Dibromo-2-(1,2-dibromo-2-phenylethyl)-5-hydroxychromone (C17H10Br4O3)
1
Yield: 469 mg (44%); mp 155–157ꢂC (EtOH); H NMR: ꢃ ¼ 5.67 (d, J ¼ 11.5Hz, H-20), 6.00
(d, J ¼ 11.5 Hz, H-10), 6.87 (d, J ¼ 8.8 Hz, H-6), 7.43–7.50 (m, H-30,40,50), 7.56 (dd, J ¼ 1.6 and
13
7.7 Hz, H-20,60), 7.84 (d, J ¼ 8.8 Hz, H-7), 11.95 (s, 5-OH) ppm; C NMR: ꢃ ¼ 48.4 (C-10), 50.1
(C-20), 98.3 (C-8), 108.5 (C-3), 110.4 (C-10), 113.6 (C-6), 128.2 (C-20,60), 129.1 (C-30,50), 129.8 (C-
40), 137.3 (C-10), 139.3 (C-7), 151.2 (C-9), 159.8 (C-5), 161.4 (C-2), 177.3 (C-4) ppm; EI-MS:
m=z (%) ¼ [586 (3), 584 (4), 582 (4), 580 (4), 578 (4)], 502 (8), 422 (100), 343 (60), 263 (36), 234
(11), 205 (13), 171 (14), 127 (55), 77 (23).
Dehydrobromination of 2-(2-aryl-1,2-dibromoethyl)chromone 2a–2c
Triethylamine (25.9 cm3, 0.187 mol) was added to a solution of the appropriate 2-(2-aryl-1,2-dibro-
moethyl)chromone 2a–2c (3.98 mmol) in 50 cm3 of toluene and the resulting mixture was stirred at
reflux, for 2 h. After cooling to room temperature the formed solid triethylammonium bromide was
filtered off and the filtrate was taken up in 150 cm3 of CHCl3. The organic layer was washed with H2O
(2ꢃ 150 cm3), dried (Na2SO4) and then evaporated. The residue in each case was recrystallised from
ethanol allowing the separation of the solid (Z)-2-(ꢀ-bromostyryl)chromones 5a–5c from the oil of
(E)-2-(ꢀ-bromostyryl)chromones 6a–6c.
(Z)-2-(ꢀ-Bromostyryl)chromone (5a, C17H11BrO2)
Yield: 846 mg (65%); mp 117–120ꢂC (EtOH); 1H NMR: ꢃ ¼ 7.00 (s, H-3), 7.40–7.50 (m, H-6 and H-
30,40,50), 7.55 (d, J ¼ 8.2 Hz, H-8), 7.72 (ddd, J ¼ 1.6, 7.8, and 8.2Hz, H-7), 7.84 (dd, J ¼ 1.9 and 7.6Hz,
H-20,60), 8.10 (s, H-ꢁ), 8.21 (dd, J ¼ 1.6 and 8.0 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 111.5 (C-3), 113.5 (C-ꢀ),
117.8 (C-8), 123.5 (C-10), 125.4 (C-6), 125.7 (C-5), 128.5 (C-30,50), 130.1 (C-20,60), 129.8 (C-40), 134.2
(C-7), 134.3 (C-10), 135.2 (C-ꢁ), 156.0 (C-9), 160.3 (C-2), 178.7 (C-4) ppm; EI-MS: m=z (%) ¼ [328
(19), 326 (18), Mþꢄ], 311 (17), 247 (100), 218 (13), 189 (13), 127 (19), 92 (15), 77 (12).
(E)-2-(ꢀ-Bromostyryl)chromone (6a, C17H11BrO2)
Yield: 417 mg (32%); yellowish oil; 1H NMR: ꢃ ¼ 6.46 (s, H-3), 7.17–7.29 (m, H-8 and H-
20,30,40,50,60), 7.40 (ddd, J ¼ 1.0, 7.7, and 8.1Hz, H-6), 7.46 (s, H-ꢁ), 7.64 (ddd, J ¼ 1.7, 7.6, and
8.1 Hz, H-7), 8.16 (dd, J ¼ 1.7 and 7.7 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 112.1 (C-ꢀ), 112.9 (C-3), 118.1
(C-8), 123.7 (C-10), 125.4 (C-6), 125.5 (C-5), 128.2 (C-30,50), 128.5 (C-20,60), 128.9 (C-40), 134.0 (C-
7), 134.8 (C-10), 140.1 (C-ꢁ), 155.9 (C-9), 160.8 (C-2), 177.9 (C-4) ppm; EI-MS: m=z (%) ¼ [328 (9),
326 (9), Mþꢄ], 309 (12), 247 (100), 218 (12), 189 (13), 127 (23), 92 (17), 77 (15).
(Z)-40-Chloro-2-(ꢀ-bromostyryl)chromone (5b, C17H10BrClO2)
Yield: 1.28g (89%); mp 181–182ꢂC (EtOH); 1H NMR: ꢃ ¼ 6.99 (s, H-3), 7.41 (dt, J ¼ 7.9 and 8.1Hz,
H-6), 7.44 (d, J ¼ 8.5 Hz, H-30,50), 7.54 (d, J ¼ 8.1Hz, H-8), 7.72 (dt, J ¼ 1.5 and 8.1 Hz, H-7), 7.79 (d,
J ¼ 8.5 Hz, H-20,60), 8.05 (s, H-ꢁ), 8.21 (dd, J ¼ 1.5 and 7.9 Hz, H-5) ppm; 13C NMR: ꢃ ¼ 111.7 (C-3),
114.3 (C-ꢀ), 117.8 (C-8), 123.6 (C-10), 125.5 (C-6), 125.8 (C-5), 128.8 (C-30,50), 131.3 (C-20,60), 132.8
(C-10), 133.9 (C-ꢁ), 134.3 (C-7), 135.8 (C-40), 156.0 (C-9), 160.0 (C-2), 178.6 (C-4) ppm; EI-MS:
m=z (%) ¼ [364 (9), 362 (21), 360 (18), Mþꢄ], 345 (26), 281 (100), 246 (26), 218 (25), 189 (15), 121
(29), 109 (26), 92 (29), 63 (20).
(E)-40-Chloro-2-(ꢀ-bromostyryl)chromone (6b, C17H10BrClO2)
1
Yield: 58mg (4%); yellowish oil; H NMR: ꢃ ¼ 6.47 (s, H-3), 7.13 (d, J ¼ 8.5Hz, H-30,50), 7.24 (d,
J ¼ 8.5 Hz, H-20,60), 7.26 (dd, J ¼ 1.0 and 8.1Hz, H-8), 7.40 (s, H-ꢁ), 7.42 (ddd, J ¼ 1.0, 7.6, and

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8.0 Hz, H-6), 7.67 (ddd, J ¼ 1.6, 7.6, and 8.1 Hz, H-7), 8.17 (dd, J ¼ 1.6 and 8.0Hz, H-5) ppm; 13C
NMR: ꢃ ¼ 112.9 (C-ꢀ), 113.1 (C-3), 118.1 (C-8), 123.8 (C-10), 125.6 (C-5), 125.6 (C-6), 128.9 (C-
20,60), 129.6 (C-30,50), 133.3 (C-10), 134.3 (C-7), 134.9 (C-40), 138.7 (C-ꢁ), 156.0 (C-9), 160.5 (C-2),
177.9 (C-4) ppm; EI-MS: m=z (%) ¼ [364 (7), 362 (22), 360 (18), Mþꢄ] 345 (28), 281 (100), 246 (28),
218 (27), 189 (21), 161 (17), 126 (38), 121 (43), 109 (22), 92 (35), 75 (18), 63 (20).
(Z)-40-Methyl-2-(ꢀ-bromostyryl)chromone (5c, C18H13BrO2)
Yield: 964 mg (71%); mp 124–126ꢂC (EtOH); 1H NMR: ꢃ ¼ 2.41 (s, 40-CH3), 6.99 (s, H-3), 7.28 (d,
J ¼ 8.3 Hz, H-30,50), 7.43 (ddd, J ¼ 1.1, 7.6, and 7.8 Hz, H-6), 7.55 (d, J ¼ 7.8 Hz, H-8), 7.72 (ddd,
J ¼ 1.7, 7.6, and 7.8 Hz, H-7), 7.78 (d, J ¼ 8.3 Hz, H-20,60), 8.08 (s, H-ꢁ), 8.21 (dd, J ¼ 1.7 and 7.8Hz,
13
H-5) ppm; C NMR: ꢃ ¼ 21.6 (40-CH3), 111.3 (C-3), 112.5 (C-ꢀ), 117.9 (C-8), 123.6 (C-10), 125.4
(C-6), 125.8 (C-5), 129.3 (C-30,50), 130.2 (C-20,60), 131.5 (C-10), 134.1 (C-7), 135.2 (C-ꢁ), 140.4 (C-
40), 156.0 (C-9), 160.5 (C-2), 178.8 (C-4) ppm; EI-MS: m=z (%) ¼ [342 (15), 340 (15), Mþꢄ], 325 (21),
261 (100), 246 (15), 218 (19), 141 (19), 115 (23), 92 (16), 63 (18).
(E)-40-Methyl-2-(ꢀ-bromostyryl)chromone (6c, C18H13BrO2)
1
Yield: 41 mg (3%); yellowish oil; H NMR: ꢃ ¼ 2.30 (s, 40-CH3), 6.44 (s, H-3), 7.04–7.10 (m, H-
20,30,50,60), 7.34 (d, J ¼ 7.9 Hz, H-8), 7.42 (s, H-ꢁ), 7.42 (ddd, J ¼ 0.9, 7.6, and 7.9 Hz, H-6), 7.68 (ddd,
13
J ¼ 1.7, 7.6, and 7.9Hz, H-7), 8.18 (dd, J ¼ 1.7 and 7.9 Hz, H-5) ppm; C NMR: ꢃ ¼ 21.3 (40-CH3),
111.1 (C-ꢀ), 112.9 (C-3), 118.3 (C-8), 123.9 (C-10), 125.5 (C-6), 125.6 (C-5), 128.3 (C-20,60), 129.4
(C-30,50), 131.9 (C-10), 134.1 (C-7), 139.3 (C-40), 140.1 (C-ꢁ), 156.2 (C-9), 161.2 (C-2), 178.1 (C-4)
ppm; EI-MS: m=z (%) ¼ [342 (11), 340 (11), Mþꢄ], 325 (20), 261 (100), 246 (14), 218 (18), 189 (8),
139 (14), 115 (23), 97 (21).
Syntheses of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles 7a–7e
Method A – From (Z)-2-(ꢀ-bromostyryl)chromones 5a–5c. 0.293 g of NaN3 (4.51 mmol) were added to
a solution of the appropriate (Z)–2-(ꢀ-bromostyryl)chromone 5a–5c (0.902mmol) in 25 cm3 of dry
DMF. The reaction mixture was heated (120ꢂC) with stirring for 24h then poured into 200cm3 of H2O,
ice (100g), and HCl (pH adjusted to 3). The obtained solid was filtered, washed with water, and taken
up in 100 cm3 of acetone. The organic layer was dried (Na2SO4) and then evaporated. The residue in
each case was recrystallised from a mixture of dichloromethane:methanol¼ 9:1 giving the correspond-
ing 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles (7a, 80%, 209 mg), (7b, 83%, 243 mg), and (7c, 61%,
167 mg).
Method B – From 2-(2-aryl-1,2-dibromoethyl)chromones 2a–2c. When 2-(2-aryl-1,2-dibro-
moethyl)chromones 2a–2c were treated with NaN3 and worked up according to the experimental
procedure of Method A 4(5)-aryl-(4)-(2-chromonyl)-1,2,3-triazoles (7a, 73%, 191 mg), (7b, 69%,
201 mg), and (7c, 54%, 148 mg) were obtained.
Method C – From 2-styrylchromones 1a–1e. The reaction of 2-styrylchromones 1a–1e with NaN3
according to the experimental procedure of Method A resulted in the corresponding 4(5)-aryl-(4)-(2-
chromonyl)-1,2,3-triazoles (7a, 55%, 144 mg), (7b, 59%, 172 mg), (7c, 48%, 131 mg), (7d, 47%,
135 mg), and (7e, 65%, 196 mg).
5(4)-(2-Chromonyl)-4(5)-phenyl-1,2,3-triazole (7a, C17H11N3O2)
1
Mp 233–235ꢂC (EtOH). H NMR (DMSO-d6 þ TFA): ꢃ ¼ 6.78 (s, H-30), 7.17 (d, J ¼ 8.4 Hz, H-80),
7.45 (t, J ¼ 7.7 Hz, H-60), 7.52–7.54 (m, H-300,400,500), 7.68–7.76 (m, H-70 and H-200,600), 8.03 (dd,
J ¼ 1.3 and 7.7Hz, H-50) ppm; 13C NMR (DMSO-d6 þ TFA): ꢃ ¼ 108.4 (C-30), 118.1 (C-80), 124.0 (C-

306
A. M. S. Silva et al.
100), 125.2 (C-50), 125.9 (C-60), 128.5 (C-100), 128.7 (C-300,500), 129.5 (C-200,600), 129.8 (C-400), 134.6 (C-
70), 135.4 (C-4), 142.1 (C-5), 155.7 (C-90), 157.8 (C-20), 176.8 (C-40) ppm; EI-MS: m=z(%) ¼ 289 (37)
[Mþꢄ], 288 (100) [M-H]þ, 272 (8), 169 (10), 121 (28), 92 (26).
4(5)-(4-Chlorophenyl)-5(4)-(2-chromonyl)-1,2,3-triazole (7b, C17H10ClN3O2)
1
Mp 299–301ꢂC (EtOH); H NMR (DMSO-d6 þ TFA): ꢃ ¼ 6.78 (s, H-30), 7.22 (d, J ¼ 8.0 Hz, H-80),
7.45 (ddd, J ¼ 0.7, 7.6, and 7.8 Hz, H-60), 7.59 (d, J ¼ 8.5 Hz, H-300,500), 7.63 (d, J ¼ 8.5Hz, H-200,600),
7.74 (ddd, J ¼ 1.6, 7.6, and 8.0 Hz, H-70), 8.03 (dd, J ¼ 1.6 and 7.8 Hz, H-50) ppm; 13C NMR (DMSO-
d6 þ TFA): ꢃ ¼ 108.6 (C-30), 118.3 (C-80), 124.0 (C-100), 125.2. (C-50), 125.9 (C-60), 127.7 (C-100),
128.8 (C-300,500), 131.3 (C-200,600), 134.7 (C-70 and C-4), 135.6 (C-400), 141.6 (C-5), 155.7 (C-90), 157.8
(C-20), 176.8 (C-40) ppm; EI-MS: m=z (%) ¼ [325 (4), 323 (16), Mþꢄ], 322 (41), 161 (34), 131 (100),
121 (24), 103 (36), 92 (24).
5(4)-(2-Chromonyl)-4(5)-(4-methylphenyl)-1,2,3-triazole (7c, C18H13N3O2)
1
Mp 258–260ꢂC (EtOH); H NMR (DMSO-d6 þ TFA): ꢃ ¼ 2.39 (s, 400-CH3), 6.76 (s, H-30), 7.24 (d,
J ¼ 8.1 Hz, H-80), 7.35 (d, J ¼ 8.0 Hz, H-300,500), 7.46 (t, J ¼ 7.7 Hz, H-60), 7.59 (d, J ¼ 8.0 Hz, H-200,600),
7.75 (ddd, J ¼ 1.6, 7.7, and 8.1 Hz, H-70), 8.03 (dd, J ¼ 1.6 and 7.7 Hz, H-50) ppm; 13C NMR (DMSO-
d6 þ TFA): ꢃ ¼ 21.0 (400-CH3), 108.2 (C-30), 118.1 (C-80), 120.9 (C-100), 123.9 (C-100), 125.1 (C-50),
125.8 (C-60), 129.2 (C-200,600 and C-300,500), 134.5 (C-70), 135.0 (C-4), 139.4 (C-400), 141.6 (C-5), 155.6
(C-90), 157.8 (C-20), 176.6 (C-40) ppm; EI-MS: m=z (%) ¼ 303 (52) [Mþꢄ], 302 (100) [M-H]þ, 275 (9),
247 (11), 121 (33), 103 (9), 92 (22).
5(4)-(2-Chromonyl)-4(5)-(4-methoxyphenyl)-1,2,3-triazole (7d, C18H13N3O3)
1
Mp 261–263ꢂC (EtOH); H NMR (DMSO-d6 þ TFA): ꢃ ¼ 3.85 (s, 400-OCH3), 6.77 (s, H-30), 7.12 (d,
J ¼ 8.8 Hz, H-300,500), 7.30 (d, J ¼ 8.4 Hz, H-80), 7.49 (t, J ¼ 7.6 Hz, H-60), 7.67 (d, J ¼ 8.8 Hz, H-200,600),
7.79 (ddd, J ¼ 1.6, 7.6, and 8.4 Hz, H-70), 8.05 (dd, J ¼ 1.6 and 7.6 Hz, H-50) ppm; 13C NMR (DMSO-
d6 þ TFA): ꢃ ¼ 55.9 (400-OCH3), 108.9 (C-30), 114.8 (C-300,500), 118.6 (C-80), 121.1 (C-100), 124.9 (C-
100), 126.0 (C-50), 126.4 (C-60), 131.7 (C-200,600), 135.1 (C-70), 135.7 (C-4), 142.2 (C-5), 156.6 (C-90),
159.0 (C-20), 161.5 (C-400), 177.8 (C-40) ppm; EI-MS: m=z(%) ¼ 319 (43) [Mþꢄ], 318 (39) [M-H]þ,
161 (59), 131 (100), 121 (23), 103 (35), 92 (18), 78 (41), 63 (62).
5(4)-(2-Chromonyl)-4(5)-(4-nitrophenyl)-1,2,3-triazole (7e, C17H10N4O4)
Mp>300ꢂC (EtOH); 1H NMR (DMSO-d6 þ TFA): ꢃ ¼ 6.84 (s, H-30), 7.29 (d, J ¼ 8.0 Hz, H-80) 7.51 (t,
J ¼ 7.7 Hz, H-60), 7.78 (dt, J ¼ 1.6 and 8.0Hz, H-70), 8.04 (d, J ¼ 8.7 Hz, H-200,600), 8.04 (dd, J ¼ 1.6 and
7.7 Hz, H-50), 8.39 (d, J ¼ 8.7 Hz, H-300,500) ppm; 13C NMR (DMSO-d6 þ TFA): ꢃ ¼ 109.5 (C-30), 118.7
(C-80), 124.2 (C-300,5), 124.6 (C-100), 125.7 (C-50), 126.3 (C-60), 131.1 (C-200,600), 135.0 (C-70), 136.6
(C-100), 136.8 (C-4), 142.5 (C-5), 148.6 (C-400), 156.3 (C-90), 157.6 (C-20), 177.4 (C-40) ppm;
EI-MS: m=z (%) ¼ 334 (36) [Mþꢄ], 333 (100) [M-H]þ, 317 (10), 287 (7), 259 (7), 205 (8), 120 (25),
92 (41).
Synthesis of 5(4)-[5-(benzyloxy and hydroxy)-2-chromonyl]-4(5)-phenyl-1,2,3-
triazoles 7f, 7g
NaN3 (14 g, 02.11 mmol) was added to a solution of 0.15 g of 5-benzyloxy-2-styrylchromone 1f
(0.42 mmol) in 25cm3 of dry DMF. The reaction mixture was heated with stirring at 120ꢂC under
N2 for 5 days then poured into a mixture of 200 cm3 of H2O, ice (100g), and HCl (pH adjusted to 3).

Bromination and Azidation Reactions of 2-Styrylchromones
307
The obtained solid was filtered off, washed with water, and taken up in 100cm3 of CH2Cl2. The
organic layer was washed with H2O (2ꢃ 100 cm3), dried (Na2SO4), and evaporated. The obtained
residue was purified by TLC (using a 9:1 mixture of CH2Cl2:ethyl acetate as eluent). After several
elutions, two spots were collected. The fraction of higher Rf value was 7g followed by 7f. After
removal of the solvent, each residue was recrystallised from ethanol.
5(4)-(5-Benzyloxy-2-chromonyl)-4(5)-phenyl-1,2,3-triazole (7f, C24H17N3O3)
Yield: 34mg (21%); mp 210–211ꢂC (EtOH); 1H NMR (DMSO-d6 þ TFA): ꢃ ¼ 5.25 (s, 50-OCH2C6H5),
6.60 (s, H-30), 6.70 (d, J ¼ 8.2 Hz, H-60), 7.07 (d, J ¼ 8.2 Hz, H-80), 7.29–7.43 (m, H-3,4,5 of 50-
OCH2C6H5), 7.52–7.56 (m, H-300,400,500), 7.60–7.63 (m, H-70 and H-2,6 of 50-OCH2C6H5), 7.69 (dd,
13
J ¼ 2.2 and 7.5 Hz, H-200,600) ppm; C NMR (DMSO-d6 þ TFA): ꢃ ¼ 70.4 (50-OCH2C6H5), 109.2 (C-
80), 110.2 (C-30), 110.2 (C-60), 115.0 (C-100), 127.3 (C-2,6 of 50-OCH2C6H5), 127.9 (C-4 of 50-
OCH2C6H5), 128.7 (C-3,5 of 50-OCH2C6H5), 128.8 (C-300,500), 129.6 (C-200,600 and C-100), 129.8
(C-400), 134.7 (C-70), 135.3 (C-4), 137.3 (C-1 of 50-OCH2C6H5), 142.1 (C-5), 155.7 (C-90), 157.9
(C-50), 158.5 (C-20), 176.4 (C-40) ppm; EI-MS: m=z (%) ¼ 395 (18) [Mþꢄ], 305 (100), 289 (7), 276
(9), 196 (9), 170 (10), 137 (29), 108 (25), 84 (69).
5(4)-(5-Hydroxy-2-chromonyl)-4(5)-phenyl-1,2,3-triazole (7g, C17H11N3O3)
Yield: 32mg (25%); mp 217–219ꢂC (EtOH); 1H NMR (DMSO-d6 þ TFA): ꢃ ¼ 6.60 (d, J ¼ 8.3 Hz, H-
60), 6.81 (d, J ¼ 8.3Hz, H-80), 6.81 (s, H-30), 7.53–7.57 (m, H-300,400,500), 7.61 (t, J ¼ 8.3 Hz, H-70), 7.71
(dd, J ¼ 2.3 and 7.5 Hz, H-200,600), 12.64 (s, 50-OH) ppm; 13C NMR (DMSO-d6 þ TFA): ꢃ ¼ 106.7 (C-
80), 107.3 (C-60), 111.5 (C-30), 110.7 (C-100), 128.1 (C-100), 128.7 (C-300,500), 129.6 (C-200,600), 129.9 (C-
400), 135.0 (C-4), 136.2 (C-70), 149.6 (C-5), 155.8 (C-90), 159.3 (C-50), 160.2 (C-20), 182.9 (C-40) ppm;
EI-MS: m=z (%) ¼ 305 (100) [Mþꢄ], 276 (6), 196 (11), 170 (11), 137 (33), 108 (27), 91 (12), 84 (24),
66 (32).
Acknowledgements
~ ^
Thanks are due to the University of Aveiro, ‘‘Fundac°ao para a Ciencia e Tecnologia’’ and FEDER for
funding the Organic Chemistry Research Unit and the project POCTI=QUI=38394=2001, to the
Portuguese-Hungarian Intergovernmental Science and Technology Cooperation Programme (Project
ꢀ
4.1.1 ICCTI=OMBF and TeT P-2=01) and also to the Hungarian National Research Foundation (Grant
OTKA T 34123).
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