Reactivity of α-arylidene benzoheteracyclanone dibromides toward azide ion: An effective approach to 3-(α-substituted-benzyl)chromones and -1-thiochromones

Article abstract of DOI:10.1016/S0040-4020(01)00142-9

Treatment of dibromides of 3-arylidenechromanones and -1-thiochromanones with sodium azide resulted in the formation of 3-(α-azidobenzyl)chromones and -1-thiochromones whereas dibromides having no antiperiplanar vicinal hydrogen in the ring such as flavanone, 1-thioflavanone and benzosuberone derivatives afforded only the parent enones by bromine elimination. Evidence supported the intermediacy of 3-(α-bromobenzyl)chromones and -1-thiochromones in this reaction. These postulated intermediates were prepared in an independent way and transformed into azides in high yield.

Full text of DOI:10.1016/S0040-4020(01)00142-9

TETRAHEDRON
Pergamon
Tetrahedron 57 (2001) 2895±2907
Reactivity of a-arylidene benzoheteracyclanone
dibromides toward azide ion: an effective approach
to 3-(a-substituted-benzyl)chromones and -1-thiochromones
p
Tamas Patonay, Zoltan Dinya, Albert Levai and Denes Molnar
Â
Â
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Department of Organic Chemistry, University of Debrecen, P.O. Box 20, H-4010 Debrecen, Hungary
 Â
Dedicated to Professor Miklos Hollosi on the occasion of his 60th birthday
Received 23 November 2000; revised 8 January 2001; accepted 25 January 2001
AbstractÐTreatment of dibromides of 3-arylidenechromanones and -1-thiochromanones with sodium azide resulted in the formation of
3-(a-azidobenzyl)chromones and -1-thiochromones whereas dibromides having no antiperiplanar vicinal hydrogen in the ring such as
¯avanone, 1-thio¯avanone and benzosuberone derivatives afforded only the parent enones by bromine elimination. Evidence supported
the intermediacy of 3-(a-bromobenzyl)chromones and -1-thiochromones in this reaction. These postulated intermediates were prepared in an
independent way and transformed into azides in high yield. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
related derivatives with sodium azide which gives
a-azido-20-hydroxychalcones 1 and several secondary
products derived from the unstable regioisomeric b-azido-
20-hydroxychalcones 2. The ratio of azide 1 and the
products from azide 2, i.e. the participation of the competing
pathways, was highly dependent on the substituent G13,14
(Scheme 1).
Vinyl azides are valuable synthetic building blocks and have
attracted considerable interest because of their manifold
transformations.1±6 Important subclasses of vinyl azides,
namely a- and b-azidovinyl ketones, have also been studied
thoroughly. The most effective methods for the synthesis
of these latter compounds are the iodine azide addition to
a,b-unsaturated ketones5±9 and the eliminative azidation of
a,b-dibromo ketones and esters.2,5,6,10,11 Very recently, a
CAN-mediated addition of azide leading to a-azidocinna-
mates and a-azido-a,b-unsaturated ketones via a-azido-b-
nitrato esters and ketones was reported.12 We have reported
on the reaction of 20-hydroxychalcone dibromides and
As a part of our interest in the synthetic applications of azido
ketones, we have examined the analogous azidation reaction
of dibromides 3 derived from exocyclic a,b-unsaturated
ketones. In these substrates the lack of an a-hydrogen
excludes the formation of any a-azidovinyl ketones.
Consequently, they may serve as possible precursors of
Scheme 1.
Keywords: azides; chromones; dehalogenation; elimination reaction.
Corresponding author. Tel.: 136-52-512-900; fax: 136-52-453-836; e-mail: tpatonay@tigris.klte.hu
p
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(01)00142-9

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T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
Scheme 2.
the tricyclic oxazoles 4 and spiroazirines 5 (Scheme 1).
Herein, we summarize the results of our study.
derivative, which was the major product in the 2-unsubsti-
tuted chromanone series, was isolated in only one case,
reaction of dibromide 13a afforded a small amount (2.4%)
of azide 17a. The low yield indicates that this pathway is not
preferred for these substrates.
2. Results and discussion
In addition to the major product Z-16e, its diastereomer
E-16e was also isolated from the reaction mixture of di-
bromide 14e, and E diastereomers were detected by TLC
in other cases as well. The appearance of these thermo-
dynamically less stable diastereomers in the products
could be rationalized in terms of either incomplete dia-
stereoselectivity in the debromination step or a subsequent
photoisomerization of the a,b-enones E-15, Z-16 during
column chromatography. Similar isomerization has already
been observed in the ®eld of aurones.15
Treatment of (3Rp,aSp)-3-bromo-3-(a-bromobenzyl)chroma-
²
nones 6a±c and (3Rp,aRp)-3-bromo-3-(a-bromobenzyl)-1-
thiochromanones 7a,c,d with 3.3 equiv. of sodium azide in
²
DMF solution led to the formation of 3-(a-azido-4-substi-
tuted-benzyl)chromones 8a±c and 3-(a-azido-4-substi-
tuted-benzyl)-1-thiochromones 9a,c,d in good yields (75±
92%). A small amount (0.7±3.6%) of the parent 3-aryl-
idenechromanones E-10 and 3-arylidene-1-thiochroma-
nones Z-11 were also isolated but no formation of any
expected 3-(a-azidoarylidene)benzoheteracyclanones 12
could be detected (Scheme 2).
As in the chromanone series, no a-azidoarylidene inter-
mediate 19 was detected or isolated in any case of
¯avanone derivatives 13,14 but two interesting by-products
were obtained from dibromide 9c. The ®rst, which was
obtained in 7.5% yield, proved to be 20-(4-chlorophenyl)-
2-phenyl-spiro[chroman-3,30-azirine]-4-one (20). The most
characteristic NMR evidences for its structure were the
¯avanone-type 2-H at dˆ5.90 ppm and C-2 signal at
dˆ81.9 ppm, the presence of a quaternary C(CO) type
signal at dˆ43.8 ppm and the appearance of a new
quaternary CvN signal (dˆ159.3 ppm) in place of the
benzylic Ca signal which had disappeared from the
spectrum. An IR band at 1762 cm21 is characteristic for
1-azirines16 and the loss of 4-chlorobenzonitrile identi®ed
in the MS spectrum furnished additional support for the
constitution of the molecule. The other minor product
obtained in 6.4% yield was identi®ed as trans-3-[1-(4-
chlorophenyl)-5-tetrazolyl]¯avanone (21) on the basis of
the following structural evidence. Doublets at dˆ5.39 and
6.11 ppm with a large coupling constant (3Jˆ12.1 Hz) in
the 1H NMR spectrum together with the signals of
two tertiary carbon signals at dˆ65.3 and 81.8 ppm in the
13C NMR spectrum, and the characteristic m/zˆ120
fragment in MS proved the presence of a trans-3-substi-
tuted ¯avanone moiety. The slight up®eld shift of the
20 0,60 0-H signals in relation to the parent ¯avanone indi-
cated the presence of an electron-donating substituent in
the 3-position. The disappearance of the benzylic Ca
signal and the appearance of a new quaternary carbon
at dˆ155.7 ppm, as well as the strong up®eld shift of
The position of the double bond in products 8 and 9 was
unequivocally proven by the CvO bonds, located at rela-
tively low wavenumbers (1610±1640 cm21) in their IR
spectra which is characteristic for the highly conjugated
chromone-type systems. The appearance of 2-H and a-H
signals at low ®eld (7.90±8.00 and ca. 6.00 ppm) in the
1H NMR spectra, and the tertiary carbon Ca signal at 60±
63 ppm in 13C NMR spectra also supported the chromone
structure. Finally, a small but characteristic long-range
coupling (4J~1 Hz) between protons 2-H and Ha was also
observed in both series, which provided an additional proof
for the allylic structure. In contrast with the similar reaction
of chalcone dibromides, no marked effect of substituent R
on the product ratio was observed.
Incorporation of a phenyl substituent into the 2-position of
the (thio)chromanone skeleton resulted in a dramatic change
in the product distribution. When (2Rp,3Rp,aSp)-3-bromo-3-
(a-bromobenzyl)¯avanones 13a,c and (2Rp,3Sp,aSp)-3-
bromo-3-(a-bromo-4-¯uorobenzyl)¯avanones 14e were
similarly reacted with sodium azide, the debrominated
parent compounds E-15a,c and Z-16e were isolated as
major products (71±76%) as well as some minor compo-
nents (Scheme 3). The 3-(a-azidobenzyl)chromone-type
²
Dibromides 3,9 with oxygen atom and derivatives 4,10 with sulfur atom
in position 1 possess the same relative con®guration, the difference in
nomenclature is due to the change in the priority of the substituents at C-3
with the oxygen/sulfur change.

T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
2897
Scheme 3.
C-3 signal in relation to that of ¯avanone, also
supported the structure. In spite of their low percentage
yields, these compounds are of high importance since
both of them should be derived from an intermediate
vinyl azide 19b (Scheme 4).
The formation of 1-azirines from either a-azidocinna-
mates17,18 or b-azidovinyl aldehydes, ketones and
esters,1,2,4,5,19±22 and b-azido-a,b-unsaturated phosphorus
derivatives23 is well-documented. Tetrazole 21 may result
from a keteneimine 26 by 1,3-dipolar cycloaddition and a
Scheme 4.

2898
T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
Scheme 5.
subsequent hydrogen migration. Formation of keteneimines
from vinylazides including b-azidovinyl ketones and b-azido-
a,b-unsaturated esters under photolytic or thermolytic con-
ditions have been reported.4,5,16,24 Recently, we observed
the formation of 1-aryl-5-(2-chromonylmethyl)tetrazoles
as by-products from E- and Z-2-a-bromostyrylchromones
and sodium azide in hot DMF which could also be explained
by an azide addition to an intermediate keteneimine.25
Figure 1. Optimized geometry of (3Rp,aSp)-3-bromo-3-(a-bromobenzyl)chromanone (3a), (2Rp,3Rp,aSp)-3-bromo-3-(a-bromobenzyl)¯avanone (9a) and
(2Rp,aSp)-2-bromo-2-(a-bromobenzyl)-1-benzosuberone (17).

T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
2899
Scheme 6.
Our assumption that a-azidoarylidene derivatives 19 could
be minor products in the reactions of dibromides 13,14 with
azide ion, was also supported by the treatment of (2Rp,aSp)-
2-bromo-2-(a-bromobenzyl)-1-benzosuberone (22) with
sodium azide. In this case, the major product (74%) parent
a,b-enone (E-23) was accompanied by a smaller amount
(14%) of E-2-(a-azidobenzylidene)-1-benzosuberone (24).
The exocyclic double bond was unequivocally demostrated
improbable in the light of literature data.38±43 The observed
lack of any marked substituent effect on the product ratio
contradicts route A since its ®rst SN step should be sensitive
to the electron-donating/withdrawing character of the
substituent of the benzyl group. The intermediate 29 in
route B with a doubly activated (allylic and benzylic) center
at Ca is expected to be highly reactive and, therefore, to be
less dependent on the electronic effects. At the same time,
both routes A and B involve an HBr elimination step which
requires an antiperiplanar44 position of bromine and hydro-
gen atoms in the (hetero)ring to give the endocyclic double
bond. The optimized45 geometry of substrates 6,7,13,14 and
22 was determined and some selected results are shown in
Fig. 1.
by the three adjacent CH2 signals observed in the 1H and 13
C
NMR spectra. Relative con®guration of azide 24 was deter-
1
mined by H±{1H} NOE experiments. Irradiation of 5-H
gave a marked difference in the signals of both 6-H and
4-H while irradiation of 3-H gave an effect on 4-H only
indicating a long distance between 3-H and the hydrogens
of 2-phenyl group (Scheme 3). This relative con®guration is
in accordance with the reported5,17,26 higher thermal stability
of trans-b-azidovinyl ketones and esters in relation to their
cis diastereomers.
These calculations indicated antiperiplanar hydrogen and
bromine atoms only in chromanones 6 and 7. On the other
hand, dibromides 13,14 and 22 contain nearly antiperiplanar
bromine atoms as exempli®ed by substrates 13a and 22. As
a consequence, dibromides 6 and 7 should afford 3-substi-
tuted chromones by HBr elimination whereas Br2 elimi-
nation should be preferred for dibromides 13,14 and 22, a
reactivity pattern that ®ts well with the experimental facts.
On the basis of their products and product ratios, dibromides
3 could be divided into two subclasses. In the ®rst group, the
major products are a-azidobenzyl derivatives 8,9 while in
the second, the debromination leading to formation of the
parent enones 15,16,23 dominates. Elimination of Br2 from
vic-dibromides is a well-documented procedure. Variously
substituted chalcone dibromides have been reported to give
chalcones in the presence of soft nucleophiles such as
iodides,27 thiourea,28,29 thiocarbanilide,30 sodium hydrogen
sul®de,31 sodium hydrogen selenide,32 and also with potas-
sium ¯uoride±alumina under microwave irradiation33 or
tin(II)chloride,34 hot pyridine35 or even hot DMF.36,37
Previously, we have also observed the formation of
20-hydroxy-4-methoxychalcone among other products in
the reaction of 2-hydroxy-4-methoxychalcone dibromide
and sodium azide in DMF at room temperature.14 It is
very likely that the azide ion and not the DMF itself acts
as nucleophile in the reaction of dibromides 3 since only an
extremely slow conversion was observed for 3a in pure
DMF solution and the completion of the Br2 elimination
in the absence of azide ion required 7 weeks at room
temperature.
To obtain more indirect proof for the intermediacy of
bromide 29, we decided to synthesize 3-(a-bromobenzyl)-
chromones 35 and their thio analogues 37 and to study their
reactivity. Since our attempts to obtain chromones 35 from
dibromides 6 upon treatment with non-nuclophilic bases
such as DABCO or DBU failed to give a single product,
we explored another approach based on the bromination of
the corresponding 3-benzyl derivatives 33,34. Substrates
33b,f with electron-withdrawing substituents in their benzyl
group were prepared by a one-pot procedure41 from chro-
manone (32) whereas chromones 33a and 34a were synthe-
sized by the base-induced rearrangement of enones E-10a
and Z-11a reported ®rst by Donnelly et al.38 (Scheme 6).
Treatment of 3-benzylchromones 33a,b,f and 34a with
N-bromosuccinimide (NBS) furnished the corresponding
bromides 35a,b,f and 37a but only products 35b,f with elec-
tron-poor benzyl groups were suf®ciently stable to be
isolated in moderate (55±60%) yields (Scheme 7).
The origin of 3-(a-azidobenzyl)-chromones 8,9 and -1-thio-
chromones 17,18 is a much more intriguing question, the
possible routes leading to these derivatives are shown in
Scheme 5.
The presence of 35a in the reaction mixture was supported
by TLC but it disappeared during chromatography and only
3-(a-hydroxybenzyl)chromone (36a) was isolated as a
product of hydrolysis. The solvolytic origin of 36a was
demonstrated by an experiment where thiochromone 34a
was brominated and the reaction mixture was directly
We can exclude route C since neither intermediate 30 nor 31
could be detected or isolated in any case and a
12!8,9,17,18 rearrangement at room temperature is very

2900
T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
Scheme 7.
treated with excess of ethanol yielding 3-(a-ethoxybenzyl)-
1-thiochromone (38a) and a small amount of alcohol 39a.
This is in accordance with the expected high reactivity of
the bromides 35,37 which can be decreased by electron-
withdrawing groups. It is noteworthy that Mallik and co-
workers46 have reported the formation of 3-(a-hydroxy-
benzyl)¯avones in the reaction of 3-arylidene¯avanones
and NBS without any mechanistic details. Treatment of
these alcohols with NaN3 in TFA solution resulted in rear-
ranged products, 3-(a-azidobenzyl)¯avone was obtained
only in a single case when the corresponding carbocation
was destabilized by a nitro group.47
sodium azide in DMF, the azides 8b,f and 9a were obtained
in excellent (77±85%) yields. This result offers another easy
entry to azides 8 and 9 starting from chromanones. The
observed high reactivity of bromides 35,37 in conjunction
with the above-mentioned lack of substituent effect on the
product ratio in the azidolysis of dibromides 6 and 7 prompt
us to favor route B (Scheme 5) over the route A.
3-(a-Azidobenzyl)chromones and thiochromones 8,9 are
considered compounds of great synthetic value. Although
no systematic studies have been conducted in this ®eld, as a
demonstration we transformed compounds 8a,9a into imino-
phosphoranes 40a,41a in excellent (86±89%) yields, the
usefulness of iminophosphoranes is well-documented and
reviewed.48±53 Selective reduction of the azide functionality
When bromides 35b,f,36a (either in their isolated form or as
a reaction mixture containing them) were reacted with
Scheme 8.

T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
2901
to give the highly unstable allylic amines 43a,44a was
performed by treatment with SnCl2/methanol.54 Surpris-
ingly, transfer hydrogenation of azide 8a resulted in a
complete reductive elimination of the azide functionality
and 3-benzylchromanone (42a) was obtained as a sole
product in poor yield (Scheme 8).
220 (10), 207 (4), 191 (3), 172 (33), 165 (6), 146 (100,
chromone skeleton), 128 (8), 120 (55, C7H4O2), 118 (26),
104 (86), 92 (26), 90(30), 77 (30), 76 (16). Anal. calcd for
C16H11N3O2 (277.28): C, 69.31; H, 4.00; N, 15.15%. Found:
C, 69.14; H, 3.87; N, 15.33%.
3.1.2. Reaction of (3Rp,aSp)-3-bromo-3-(a-bromo-4-
chlorobenzyl)chromanone (6b) with sodium azide.
(3Rp,aSp)-3-Bromo-3-(a-bromo-4-chlorobenzyl)chromanone
(6b) (2.150 g, 4.994 mmol) was reacted as given for dibro-
mide 6a. Work-up and column chromatography afforded
10 mg (0.7%) of E-3-(4-chlorobenzylidene)chromanone40
(E-10b) and 1.324 g (85%) of 3-(a-azido-4-chlorobenzyl)-
chromone (8b). 8b. Colourless needles. Mp 82±848C
(methanol). IR: 2102 (N3), 1640 (CvO), 1622 (CvC),
1612, 1490, 1466, 1400, 1356, 1320, 1242, 1164, 1088
In conclusion, we have devised two simple, ef®cient and
convenient methods for the synthesis of 3-(a-azidobenzyl)-
chromones and -1-thiochromones 8,9. Synthesis starting
from dibromides 6,7 requires an antiperiplanar 2-H in the
heteroring otherwise Br2 elimination leading to the parent
exocyclic a,b-enones occurs. Evidence supports the inter-
mediacy of 3-(a-bromobenzyl)chromones and -1-thio-
chromones 35,37 in this approach. Bromides 35,37 were
prepared in an independent way and transformed into azides
8,9 in high yields.
1
(Ar±Cl), 800, 768, 756 cm21. H NMR: 5.99 (s, 1H, a-H),
7.37 (m, 5H, 6,200,300,500,600-H), 7.45 (d, Jˆ8.3 Hz, 1H, 8-H),
7.69 (ddd, Jˆ8.8, 8.5, 1.5 Hz, 1H, 7-H), 7.97 (d, Jˆ1.0 Hz,
1H, 2-H), 8.18 (dd, Jˆ7.9, 1.4 Hz, 1H, 5-H). 13C NMR: 59.9
(Ca), 118.1 (C-8), 123.9 (C-3, C-4a), 125.4 (C-6), 126.0
(C-5), 128.7 (C-200,600), 129.0 (C-300,500), 133.9 (C-7),
134.4 (C-100), 136.4 (C-400), 153.9 (C-2), 156.3 (C-8a),
175.6 (C-4). MS: 283 (17, M1z2N2)1285 (6, isotope
peak), 269 (6), 172 (14), 149 (11), 146 (100, chromone
skeleton), 120 (23, C7H4O2), 111 (9), 104 (28), 92 (19),
89 (14), 79 (10), 77 (14), 76 (10). Anal. calcd for
C16H10ClN3O2 (311.73): C, 61.65; H, 3.23; N, 13.48%.
Found: C, 61.75; H, 3.16; N, 13.22%.
3. Experimental
3.1. General
Melting points were determined on a Boetius hot-stage
apparatus and are uncorrected. IR spectra were recorded
with a Perkin±Elmer 16 PC FT-IR instrument in KBr pellets
1
unless otherwise speci®ed. H NMR (200 MHz) and 13C
NMR (50 MHz) spectra were recorded with a Bruker WP
200 SY, 1H NMR (360 MHz) spectra were measured with a
Bruker AM 360 instrument in CDCl3 solution (internal
standard TMS, dˆ0 ppm) unless otherwise stated.13C
NMR assignments were supported by J-echo technique.
MS spectra were recorded with a VG 7035 GC-MS-DS
system or VG Trio-2 (EI, 70 eV). Elemental analyses
were performed in-house with a Carlo Erba 1106 EA instru-
ment. MgSO4 was used as drying agent, column chroma-
tography was performed on Silica 60 (0.063±0.2 mm).
Thin-layer chromatography (TLC) was performed on
Kieselgel 60 F254 (Merck) sheets using toluene±ethyl
acetate (4:1, v/v) or hexane±ethyl acetate (6:1, v/v) as
developing systems. Dibromides 3,4,9,10 and 19 were
prepared as described.55
3.1.3. Reaction of (3Rp,aSp)-3-bromo-3-(a-bromo-4-
methylbenzyl)chromanone (6c) with sodium azide.
(3Rp,aSp)-3-Bromo-3-(a-bromo-4-methylbenzyl)chromanone
(3c) (2.050 g, 4.999 mmol) was reacted as given for dibro-
mide 6a. Work-up and column chromatography afforded
46 mg (3.6%) of E-3-(4-methylbenzylidene)chromanone40
(E-10c) and 1.137 g (78%) of 3-(a-azido-4-methylbenzyl)-
chromone (8c). 8c. Colourless needles. Mp 126±1288C
(hexane±ethyl acetate). IR: 3034, 2098 (N3), 1640
(CvO), 1622 (CvC), 1468, 1400, 1358, 1164, 762 cm21
.
1H NMR: 2.32 (s, 3H, 400-Me), 5.98 (brs, 1H, a-H), 7.17 (d,
Jˆ8.0 Hz, 2H, 300,500-H), 7.32 (d, Jˆ8.0 Hz, 2H, 200,600-H),
7.36 (m, 1H, 6-H), 7.42 (d, Jˆ8.6 Hz, 1H, 8-H), 7.63 (m,
1H, 7-H), 7.94 (d, Jˆ1.0 Hz, 2-H), 8.17 (dd, Jˆ7.9, 1.4 Hz,
3.1.1. Reaction of (3Rp,aSp)-3-bromo-3-(a-bromo-
benzyl)chromanone (6a) with sodium azide. A solution
of (3Rp,aSp)-3-bromo-3-(a-bromobenzyl)chromanone (6a)
(1.980 g, 4.999 mmol) and NaN3 (1.076 g, 16.55 mmol) in
abs. N,N-dimethylformamide (DMF) (20 mL) was stirred
for 2 h at room temperature. The mixture was poured into
crushed ice, the precipitation was ®ltered off and submitted
to column chromatography (hexane±ethyl acetate (6:1,
v/v)) to yield 9 mg (0.8%) of E-3-benzylidenechromanone40
(E-10a) and 1.275 g (92%) of 3-(a-azidobenzyl)chromone
(8a). 8a. Colourless platelets. Mp 113±1158C (methanol).
IR: 2102 (N3), 1643 (CvO), 1624 (CvC), 1613, 1470,
13
1H, 5-H). C NMR: 21.0 (400-Me), 60.3 (Ca), 118.0 (C-8),
123.9 (C-4a), 124.2 (C-3), 125.2 (C-6), 126.0 (C-5), 127.2
(C-200,600), 129.4 (C-300,500), 133.7 (C-7), 134.6 (C-100), 138.2
(C-400), 154.0 (C-2), 156.3 (C-8a), 175.7 (C-4). MS: 263 (53,
M1z2N2), 262 (14), 249 (17, M1z2N3), 248 (12), 234 (10),
220 (4), 172 (20), 146 (100, chromone skeleton), 129 (23),
120 (35, C7H4O2), 118 (13), 104 (57), 92 (20), 91 (24), 90
(20), 77 (9), 76 (8). Anal. calcd for C17H13N3O2 (291.31): C,
70.09; H, 4.50; N, 14.42%. Found: C, 70.43; H, 4.47; N,
14.46%.
3.1.4. Reaction of (3Rp,aRp)-3-bromo-3-(a-bromo-
benzyl)-1-thiochromanone (7a) with sodium azide.
(3Rp,aRp)-3-Bromo-3-(a-bromobenzyl)-1-thiochromanone
(7a) (2.060 g, 4.998 mmol) was reacted as given for di-
bromide 6a. Work-up and column chromatography afforded
40 mg (3.2%) of Z-3-benzylidene-1-thiochromanone40
(Z-11a) and 1.221 g (83%) of 3-(a-azidobenzyl)-1-thio-
chromone (9a). 9a. Off-white prisms. Mp 85±87.58C
1398, 1356, 1163, 760 cm21 1H NMR: 6.03 (brs, 1H,
.
a-H), 7.30±7.45 (m, 7H, 6,8-H1Ph), 7.65 (ddd, Jˆ8.0,
7.8, 1.9 Hz, 1H, 7-H), 7.91 (d, Jˆ1.0 Hz, 1H, 2-H), 8.18
(dd, Jˆ8.6, 1.9 Hz, 1H, 5-H). 13C NMR: 60.4 (Ca), 118.1
(C-8), 123.7 (C-4a), 123.9 (C-3), 125.3 (C-6), 125.9 (C-5),
127.3 (C-200,600), 128.4 (C-400), 128.8 (C-3,500), 133.7 (C-100),
133.8 (C-7), 154.2 (C-2), 156.3 (C-8a), 175.8 (C-4). MS:
249 (76, M1z2N2), 248 (20, M1z2N3), 235 (15), 221 (8),

2902
T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
(hexane±ethyl
(CvO1CvC), 1590, 1451, 1439, 1377, 1258, 1239, 748,
acetate).
IR:
2107
(N3),
1613
oil. IR (neat): 3062, 3030, 2098 (N3), 1644 (CvO), 1622
(CvC), 1568, 1494, 1464, 1384, 1304, 1222, 1148, 1110,
1028, 760, 730, 698 cm21. H NMR: 5.90 (s, 1H, a-H),
710 cm21. H NMR: 6.19 (brs, 1H, a-H), 7.33 (m, 1H, 400-
1
1
H), 7.30±7.51 (m, 5H, 6,7,8,300,500-H), 7.57 (m, 2H, 200,600-
H), 7.97 (d, Jˆ0.8 Hz, 1H, 2-H), 8.52 (dd, Jˆ7.8, 1.9 Hz,
1H, 5-H). 13C NMR: 63.6 (Ca), 126.5, 127.8, 128.3, 129.0
(C-5,6,8,400), 127.4, 128.7 (C-200,300,500,600), 131.4 (C-7),
131.6 (C-4a), 134.6 (C-3), 135.6 (C-2), 136.7 (C-8a),
137.8 (C-100), 177.6 (C-4). MS: 265 (37, M1z2N2), 264 (6,
M1z2N2±H), 251 (4), 237 (7), 236 (6), 188 (12, M1z2N2±
Ph), 162 (100, 1-thiochromone skeleton), 149 (3), 136 (15),
134 (67, 1-thiochromone±CO), 108 (14), 104 (41), 89 (17),
77 (17). Anal. calcd for C16H11N3OS (293.35): C, 65.51; H,
3.78; N, 14.32%. Found: C, 65.77; H, 3.65; N, 14.44%.
7.25±7.49 (m, 12H, 6,8-H12xPh), 7.69 (ddd, Jˆ8.6, 8.0,
1.6 Hz, 1H, 7-H), 8.26 (dd, Jˆ7.9, 1.6 Hz, 1H, 5-H). 13C
NMR: 61.0 (Ca), 117.9 (C-8), 119.7 (C-3), 123.5 (C-4a),
125.4 (C-6), 126.2 (C-5), 126.4, 128.2, 128.5, 128.7
(C-20,30,50,60,200,300,500,600), 127.3 (C-400), 130.8 (C-40),
132.2 (C-100), 134.0 (C-7), 137.9 (C-10), 156.0 (C-8a,
C-2),165.4 (C-2), 176.9 (C-4). MS: 325 (34, M1z2N2),
324 (100), 312 (19), 311 (16), 248 (18), 233 (15), 222
(10), 221 (17), 207 (5), 194 (8), 191 (21), 165 (21), 121
(36, 2-HOC6H4CO%), 120 (28, C7H4O2), 115 (5), 105 (6),
92 (20), 84 (13), 77 (11). Anal. calcd for C22H15N3O2
(353.38): C, 74.78; H, 4.28; N, 11.89%. Found: C, 74.51;
H, 4.39; N, 11.65%.
3.1.5. Reaction of (3Rp,aRp)-3-bromo-3-(a-bromo-4-
methylbenzyl)-1-thiochromanone (7c) with sodium
azide. (3Rp,aRp)-3-Bromo-3-(a-bromo-4-methylbenzyl)-
1-thiochromanone (7c) (2.130 g, 4.998 mmol) was reacted
as given for dibromide 6a. Work-up and column chroma-
tography afforded 10 mg (0.8%) of Z-3-(4-methylbenzyl-
idene)-1-thiochromanone40 (Z-11c) and 1.190 g (78%) of
3-(a-azido-4-methylbenzyl)-1-thiochromone (9c). 9c.
Yellowish oil. IR (neat): 3028, 2922, 2104 (N3), 1614
(CvO1CvC), 1590, 1550, 1512, 1438, 1372, 1302,
3.1.8. Reaction of (2Rp,3Rp,aSp)-3-bromo-3-(a-bromo-4-
chlorobenzyl)¯avanone (13c) with sodium azide.
(2Rp,3Rp,aSp)-3-Bromo-3-(a-bromo-4-chlorobenzyl)¯ava-
none (13c) (2.000 g, 3.948 mmol) was reacted for 2 h as
given for dibromide 6a. Work-up and column chroma-
tography (hexane±ethyl acetate (4:1, v/v)) afforded
967 mg (71%) of E-3-(4-chlorobenzylidene)¯avanone57
(E-15c), 107 mg (7.5%) of 20-(4-chlorophenyl)-2-phenyl-
spiro[chroman-3,30-azirine]-4-one (20) and 102 mg (6.4%)
of trans-3-[1-(4-chlorophenyl)-5-tetrazolyl]¯avanone (21).
1
1238, 1180, 1144, 1114, 820, 762, 746 cm21. H NMR:
2.31 (s, 3H, 400-Me), 6.15 (s, 1H, Ha), 7.16 (d, Jˆ8.0 Hz,
2H, 300,500-H), 7.30 (d, Jˆ8.0 Hz, 2H, 200,600-H), 7.45±7.62
(m, 3H, 6,7,8-H), 7.98 (s, 1H, 2-H), 8.51 (dd, Jˆ7.5, 1.5 Hz,
1H, 5-H). MS: 279 (23, M1z2N2), 265 (3), 188 (5,
M1z2N2±Bn), 162 (100, 1-thiochromone skeleton), 134
(26, 1-thiochromone±CO), 108 (10), 104 (18), 89 (15).
Anal. calcd for C17H13N3OS (307.36): C, 66.43; H, 4.26;
N, 13.67%. Found: C, 66.78; H, 4.07; N, 13.64%.
20. White crystal powder. Mp 182±1878C (hexane±ethyl
acetate). IR: 1762 (CvN), 1684 (CvO), 1606, 1594,
1486, 1472, 1462, 1454, 1314, 1300, 1222 (C±O±C),
1
1100, 1018, 764, 700 cm21. H NMR: 5.90 (s, 1H, 2-H),
7.07±7.21 (m, 2H, 6,8-H), 7.26 (m, 3H, 300 0,400 0,500 0-H),
7.33 (m, 2H, 200 0,600 0-H), 7.50 (d, Jˆ8.5 Hz, 2H, 200,600-H),
7.57 (m, 1H, 7-H), 7.71 (d, Jˆ8.5 Hz, 2H, 300,500-H), 7.95
(dd, Jˆ7.8, 1.5 Hz, 1H, 5-H). 13C NMR: 43.8 (C-3), 81.9
(C-2), 118.7 (C-8), 120.6, 122.7 (C-4a, C-400 0), 122.1 (C-6),
127.2 (C-5), 127.5, 128.5 (C-200,300,500,600), 128.7 (C-400),
129.8 (C-200 0,600 0), 131.4 (C-300 0,500 0), 134.8 (C-100), 136.5
(C-7), 140.1 (C-100 0), 159.3 (C-20), 161.2 (C-8a). MS: 359
(45, M1z)1361 (16, isotope peak), 358 (84)1360 (34), 282
(39, M1z2Ph)1284 (15), 238 (8), 221 (100, M1z2124-
ClC6H4CN), 194 (8), 165 (14), 150 (7), 137 (57,
4-ClC6H4CN1z)1139 (22), 121 (13, 2-HOC6H4CO%), 120
(25, C7H4O2), 102 (51), 92 (25), 76 (22). Anal. calcd for
C22H14ClNO2 (359.81): C, 73.44; H, 3.92; N, 3.89%. Found:
C, 73.12; H, 4.02; N, 3.97%.
3.1.6. Reaction of (3Rp,aRp)-3-bromo-3-(a-bromo-4-
methoxybenzyl)-1-thiochromanone (7d) with sodium
azide. (3Rp,aRp)-3-Bromo-3-(a-bromo-4-methoxybenzyl)-
1-thiochromanone (7d) (2.210 g, 4.998 mmol) was reacted
as given for dibromide 6a. Work-up and column chroma-
tography afforded 48 mg (3.4%) of Z-3-(4-methoxybenzyl-
idene)-1-thiochromanone40 (Z-11d) and 1.217 g (75%) of
3-(a-azido-4-methoxybenzyl)-1-thiochromone (9d). 9d.
Yellowish oil. IR (neat): 3034, 2956, 2836, 2104 (N3),
1614 (CvO1CvC), 1590, 1550, 1512, 1462, 1438,
1372, 1304, 1250 (C±O±C), 1176, 1112, 1034 (C±O±C),
834, 748 cm21. 1H NMR: 3.78 (s, 3H, 400-OMe), 6.13 (s, 1H,
Ha), 6.90 (d, Jˆ8.7 Hz, 2H, 300,500-H), 7.34 (d, Jˆ8.7 Hz,
2H, 200,600-H), 7.47±7.60 (m, 3H, 6,7,8-H), 8.01 (s, 1H,
H-2), 8.51 (dd, Jˆ7.8, 1.2 Hz, 1H, 5-H). MS: 295 (35,
M1z2N2), 281 (7), 188 (5, M1z2N2±MeOC6H4), 162
(100, 1-thiochromone skeleton), 134 (30, 1-thiochromone±
CO), 108 (10), 104 (18), 89 (16). Anal. calcd for
C17H13N3O2S (323.36): C, 63.14; H, 4.05; N, 12.99%.
Found: C, 63.36; H, 3.92; N, 13.12%.
21. White needles. Mp 168±1718C (hexane±ethyl acetate).
IR: 3064, 2898, 1702 (CvO), 1608, 1430, 1326, 1300,
1
1228, 1110, 1092, 1024, 840, 760, 700 cm21. H NMR:
5.39 (d, Jˆ12.1 Hz, 1H, 3-H), 6.11 (d, Jˆ12.1 Hz, 1H,
2-H), 6.93 (d, Jˆ7.1 Hz, 2H, 200,600-H), 7.01±7.32 (m, 7H,
6,8-H1Ph), 7.65 (m, 1H, 7-H), 8.04 (d, 1H, Jˆ7.8 Hz, 1H,
5-H). 13C NMR: 65.3 (C-3), 81.8 (C-2), 118.4 (C-8), 119.4
(C-400), 121.3 (C-4a), 123.0 (C-6), 126.5 (C-200,600), 128.0
(C-5), 129.0, 129.5, 130.1 (C-20,30,50,60,30,60), 129.9 (C-400),
134.4 (C-10), 137.7 (C-7), 137.9 (C-100), 155.7 (tetrazole C),
161.2 (C-8a), 185.1 (C-4). MS: 402 (32, M1z)1404 (11,
isotope peak), 374 (11, M1z2CO), 373 (13), 332 (83,
M1z2CO±N3)1334 (32), 253 (72)1255 (24), 222 (77,
¯avone skeleton), 209 (21), 181 (66), 152 (11), 121
(66, 2-HOC6H4CO%), 120 (100, C7H4O2), 117 (28), 93
3.1.7. Reaction of (2Rp,3Rp,aSp)-3-bromo-3-(a-bromo-
benzyl)¯avanone (13a) with sodium azide. (2Rp,3Rp,aSp)-
3-Bromo-3-(a-bromobenzyl)¯avanone (13a) (2.360 g,
4.998 mmol) was reacted for 30 h as given for dibromide
6a. Work-up and column chromatography afforded 1.186 g
(76%) of E-3-benzylidene¯avanone56,57 (E-15a) and 41 mg
(2.3%) of 3-(a-azidobenzyl)¯avone (17a). 17a. Colourless

T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
2903
(23), 90 (36). Anal. calcd for C22H14ClNO2 (402.84): C,
65.59; H, 3.75; N, 13.91%. Found: C, 65.23; H, 3.72; N,
13.57%.
102 mg (14%) of E-2-(a-azidobenzylidene)-1-benzo-
suberone (24). 24. Yellowish oil. IR (neat): 3060, 2942,
2860, 2106 (N3), 1668 (CvO), 1596, 1448, 1304, 1266,
1
1246, 972, 958, 766 cm21. H NMR: 2.13 (m, 2H, 4-H),
3.1.9. Reaction of (2Rp,3Sp,aSp)-3-bromo-3-(a-bromo-4-
¯uorobenzyl)-1-thio¯avanone (14e) with sodium azide. A
mixture of (2Rp,3Sp,aSp)-3-bromo-3-(a-bromo-4-¯uoro-
benzyl)-1-thio¯avanone (14e) (1.518 g, 2.999 mmol),
NaN3 (646 mg, 9.933 mmol) and abs. DMF (12 mL) was
stirred at room temperature for 3 h, a slightly exothermic
reaction and some gas evolution was observed in the ®rst
10 min. The mixture was poured on water, the precipitate
was ®ltered off and crystallized from methanol to give
778 mg (75%) of Z-3-(4-¯uorobenzylidene)-1-thiochroma-
none56 (Z-16e). The evaporated mother liquor was
submitted to column chromatography (eluent: toluene) and
two fractions were collected. The more polar fraction was
re-chromatographed on silica gel (eluent: hexane±acetone
(4:1, v/v)) to give 14 mg (1.2%) of 3-(a-azido-4-¯uoro-
benzyl)-1-thio¯avone (18e). 18e. Pale yellow oil. IR
(neat): 3062, 2924, 2096 (N3), 1626 (CvO), 1614
(CvC), 1592, 1538, 1510, 1436, 1338, 1226, 1158, 830,
2.74 (t, 2H, 3-H), 3.06 (t, 2H, 5-H), 7.23±7.39 (m, 7H,
7,9-H1Ph), 7.47 (m, 1H, 8-H), 7.80 (dd, Jˆ7.7, 1.4 Hz,
1H, 9-H). 13C NMR: 23.5 (C-4), 30.8, 32.1 (C-3,5), 127.0
(C-8), 128.1, 128.5 (C-200,300,500,600), 128.7, 129.6, 130.1 (C-
6,9,400), 133.3 (C-7), 133.8 (C-100), 136.5 (C-9a), 140.6,
141.0, 141.6 (C-2,5a, Ca), 193.5 (C-1). Anal. calcd for
C18H15N3O (289.33): C, 74.72; H, 5.23; N, 14.52%.
Found: C, 74.29; H, 5.21; N, 14.77%.
3.1.11. N,N-Dimethylformamide-induced elimination of
(3Rp,aSp)-3-bromo-3-(a-bromo-benzyl)chromanone (6a).
A
solution of (3Rp,aSp)-3-bromo-3-(a-bromobenzyl)-
chromanone (6a) (800 mg, 2.020 mmol) in abs. DMF
(15 mL) allowed to stand at room temperature. The reaction
was monitored by TLC for the disappearence of starting
material. After 7 weeks, the mixture was poured into 0.5%
Na2SO3 solution (100 mL) and extracted with dichloro-
methane (3£20 mL). The dried solution was concentrated
in vacuo and submitted to column chromatography (eluent:
toluene±ethyl acetate (4:1, v/v)) to give 203 mg (43%) of E-
3-benzylidenechromanone56 (E-10a) and 153 mg (30%) of
3-(a-hydroxybenzyl)chromone (36a). 36a. Mp 121±1238C
(hexane±ethyl acetate), lit.59 mp 1208C. IR: 3420 (OH),
1636 (CvO), 1618, 1606, 1570, 1466, 1420, 1402, 1350,
1
746, 700 cm21. H NMR: 5.96 (s, 1H, a-H), 6.90 (m, 2H,
6,8-H), 7.14±7.65 (m, 10H, 7-H1200,300,500,600-H1Ph), 8.54
(dd, Jˆ7.9, 2.0 Hz, 1H, 5-H). 13C NMR: 61.6 (Ca), 114.9 (d,
JC±F, orthoˆ21.4 Hz, C-300,500), 125.5, 128.0, 129.4 (C-5,6,8),
127.7 (d, JC±F,
ˆ8.1 Hz, C-200,600), 128.5, 128.7
meta
(C-20,30,50,60), 130.0 (C-40), 131.2, 131.5 (C-4a,10), 131.9
1
(C-7), 134.3 (C-100), 135.1, 136.9 (C-3,8a), 154.8 (C-2),
161.7 (d, JC±F,
calcd for C22H14FN3OS (387.43): C, 68.20; H, 3.64; N,
10.85%. Found: C, 68.43; H, 3.39; N, 10.59%.
1318, 1158, 1142, 1036, 862, 762, 742, 728, 704 cm21. H
ˆ246 Hz, C-400), 178.7 (C-4). Anal.
NMR: 3.01 (brs, 1H, a-OH), 5.93 (s, 1H, a-H), 7.32±7.50
(m, 7H, 6,8-H1Ph), 7.64 (s, 1H, 2-H), 7.66 (m, 1H, 7-H),
8.21 (dd, Jˆ8.1, 1.6 Hz, 5-H). 13C NMR: 70.4 (Ca), 118.1
(C-8), 123.8, 126.4 (C-3,4a), 125.3, 125.7 (C-5,6), 126.6
(C-400), 127.9, 128.5 (C-200,300,500,600), 134.0 (C-7), 140.6
(C-100), 153.7 (C-2), 156.0 (C-8a), 178.2 (C-4). MS: 252
(100, M1z), 251 (29, M1z21), 234 (17, M1z2H2O), 233
(16, M1z212H2O), 222 (24, M1z2CH2O), 221 (28,
M1z2CH2O21), 205 (37, M1z212H2O±CO), 173 (48,
M1z212PhH), 146 (22. chromone skeleton), 121 (41,
2-HOC6H4CO%), 105 (24, PhCO%), 92 (20), 90 (20), 77
(69). Anal. calcd for C16H12O3 (252.26): C, 76.18; H,
4.79%. Found: C, 76.33; H, 4.77%.
ipso
The less polar fraction was re-chromatographed on silica gel
(eluent: toluene-1,2-dichloroethane (2:1, v/v)) to afford
50 mg (4.8%) of E-3-(4-¯uorobenzylidene)-1-thiochroma-
none56 (E-16e) and 45 mg (4.3%) of Z-isomer (Z-16e).
E-16e. Yellow oil. IR (neat): 3060, 2926, 1660 (CvO),
1614 (CvC), 1600, 1504, 1434, 1294, 1224, 1158, 1072,
970, 834, 742, 728 cm21. 1H NMR: 5.26 (s, 1H, 2-H), 6.71
(s, 1H, a-H), 6.97 (m, 2H, 6,8-H), 7.15±7.62 (m, 10H,
7-H1200,300,500,600-H1Ph), 8.10 (d, Jˆ8.0 Hz, 5-H).
13
C
NMR: 45.4 (C-2), 116.0 (d, JC±F, orthoˆ21.4 Hz, C-300,500),
126.0 (C-6), 127.7, 128.6 (C-20,30,50,60), 128.2 (d, JC±F, meta
ˆ
3.1.12. 3-Benzylchromone (33a). A mixture of E-3-benzyl-
idenechromanone56 (E-10a) (1.665 g, 7.047 mmol), anh.
K2CO3 (1.665 g, 12.048 mmol) and abs. DMF (85 mL)
was re¯uxed for 5 h, then poured into brine and extracted
with ethyl acetate (5£50 mL). After drying, the solvent was
removed under reduced pressure and the residue was
submitted to column chromatography (eluent: toluene±
ethyl acetate (8:1, v/v)) to afford 808 mg (49%) of pure
33a as brownish prisms, Mp 110±1118C (methanol), lit.60
mp 109±1118C. IR: 1646 (CvO), 1611 (CvC), 1466,
4.5 Hz, C-300,500), 129.6, 131.2, 131.4 (C-5,8,40), 130.9
(C-4a), 132.1 (C-3)p, 135.0 (C-100 0), 136.7 (C-1')p, 137.3
(Ca), 139.4 (C-8a), 163.0 (d, JC±F,
ˆ252 Hz, C-400),
ipso
186.0 (C-4). pInterchangeable signals. MS: 346 (100,
M1z), 345 (17, M1z21), 332 (12), 317 (7, M1z2HCO),
282 (9), 237 (12, M1z2FC6H4CH%), 210 (45, RDA
fragment), 209 (52, RDA fragment-1), 183 (14), 137
(26, 2-HSC6H4CO%), 136 (24, C7H4OS), 108 (19,
C7H4OS±CO), 83 (91, FC5H4%). Anal. calcd for
C22H15FOS (346.41): C, 76.28; H, 4.36%. Found: C,
76.02; H, 4.40%.
1
1398, 1355, 1318, 1143, 762, 758 cm21. H NMR: 3.82
(d, Jˆ0.8 Hz, 2H, a-H), 7.25 (m, 1H, 6-H), 7.31 (s, 1H,
Ph), 7.40 (d, Jˆ7.1 Hz, 1H, 8-H), 7.61 (d, Jˆ0.8 Hz, 1H,
2-H), 7.63 (m, 1H, 7-H), 4.54 (dd, Jˆ7.8, 1.5 Hz, 1H, 5-H).
13C NMR: 31.5 (Ca), 118.1 (C-8), 124.0, 124.7 (C-3,4a),
125.0, 126.1 (C-5,6), 126.6 (C-400), 128.7, 129.1
(C-200,300,500,600), 133.5 (C-7), 138.77 (C-100), 153.3 (C-2),
156.6 (C-8a), 177.6 (C-4). Anal. calcd for C16H12O2
(236.27): C, 81.34; H, 5.12%. Found: C, 81.09; H,
4.97%.
3.1.10. Reaction of (2Rp,aSp)-2-bromo-2-(a-bromo-
benzyl)-1-benzosuberone (22) with sodium azide.
(2Rp,aSp)-2-Bromo-2-(a-bromobenzyl)-1-benzosuberone
(22) (1.020 g, 2.499 mmol) was reacted as given for dibro-
mide 6a. Work-up and column chromatography (eluent:
1,2-dichloroethane±toluene (3:1, v/v)) afforded 462 mg
(74%) of E-2-benzylidene-1-benzosuberone58 (E-23) and

2904
T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
3.1.13. 3-(4-Chlorobenzyl)chromone (33b). A mixture of
4-chromanone (32) (7.400 g, 49.946 mmol), 4-chloro-
benzaldehyde (7.025 g, 49.976 mmol) and piperidine
(3.0 mL, 34.281 mmol) was heated at 1508C for 5 h. The
solidi®ed residue was treated with methanol, ®ltered off and
recrystallized to give 6.768 g (50%) of pure chromone 33b
as colourless needles. Mp 140.5±141.58C (methanol), lit.61
mp 1408C. IR: 1643 (CvO), 1608 (CvC), 1490, 1463,
peroxide (60 mg, 0.248 mmol) in carbon tetrachloride
(50 mL) was re¯uxed for 2 h and 30 min. The precipitated
succinimide was ®ltered off, the ®ltrate was washed with
satd NaHCO3 solution and water, and dried. The solvent was
removed under reduced pressure and residue was crystal-
lized from hexane±ethyl acetate (1:1, v/v) to give 1.023 g
(58%) of chromone 35b as colourless platelets. Mp 151±
1538C. IR: 1644 (CvO), 1620 (CvC), 1466, 1398, 1354,
1
1
1399, 1362, 1318, 1148, 1087, 1014, 764, 758 cm21. H
1318, 1142, 1090, 762, 756 cm21. H NMR: 6.40 (s, 1H,
NMR: 3.78 (s, 2H, a-H), 7.25 (s, 4H, 200,300,500,600-H),
7.36±7.43 (overlapping m's, 2H, 6,8-H), 7.65 (m, 1H,
7-H), 7.66 (s, 1H, 2-H), 8.22 (d, Jˆ8.0, 1.8 Hz, 1H, 5-H).
13C NMR: 31.1 (Ca), 118.0 (C-8), 123.8, 124.1 (C-3,4a),
125.0, 125.9 (C-5,6), 128.6 (C-200,600), 130.2 (C-300,500),
132.3 (C-400), 133.5 (C-7), 137.2 (C-400), 152.9 (C-2),
156.4 (C-8a), 177.3 (C-4).
a-H), 7.33 (d, Jˆ8.7 Hz, 2H, 200,600), 7.34 (m, 1H, 6-H), 7.45
(overlapping d and dd, 3H, 8,300,500-H), 7.70 (m, 1H, 7-H),
8.14 (d, Jˆ0.8 Hz, 1H, 2-H), 8.22 (dd, Jˆ8.1, 1.8 Hz, 1H,
5-H). 13C NMR: 44.5 (Ca), 118.1 (C-8), 123.5 (C-4a), 125.1
(C-3), 125.6, 126.1 (C-5,6), 128.9, 129.5 (C-200,300,500,600),
134.1 (C-7), 134.3 (C-400), 137.8 (C-100), 156.2 (C-8a), 156.3
(C-2), 174.9 (C-4). MS: 269 (100, M1z2Br)1271 (36, Cl
isotope peak), 234 (14, M1z2Br±Cl), 205 (5), 178 (7), 176
(5), 149 (65, M1z2Br±RDA fragment [C7H4O2]), 121 (13,
2-HOC6H4CO%), 117 (15), 114 (10), 92 (11). Anal.calcd for
C16H10BrClO2 (349.61): C, 54.97; H, 2.88%. Found: C,
54.58; H, 2.95%.
3.1.14. 3-(4-Bromobenzyl)chromone (33f). 4-Chromanone
(32) (3.702 g, 24.986 mmol) and 4-bromobenzaldehyde
(4.630 g, 25.023 mmol) were reacted as given for chromone
33b to afford 4.253 g (54%) of product 33f as off-white
prisms. Mp 152±1548C (methanol), lit.43 mp 155.0±
156.98C. IR: 1641 (CvC), 1609 (CvC), 1571, 1488,
3.1.18. 3-(a,4-Dibromobenzyl)chromone (35f). 3-(4-
Bromobenzyl)chromone (33f) (2.835 g, 8.995 mmol) was
reacted as given for chromone 35b. Work-up and crystal-
lization from hexane±ethyl acetate (1:1, v/v) afforded
1.949 g (55%) of chromone 35f as colourless needles. Mp
139±1418C. IR: 1640 (CvO), 1609 (CvC), 1466, 1401,
1
1463, 1398, 1351, 1310, 1147, 1010, 764, 757 cm21. H
NMR: 3.76 (s, 2H, a-H), 7.19 (d, Jˆ8.4 Hz, 2H, 200,600-H),
7.40 (overlapping d and m's, 4H, 6,8,300,500-H), 7.65 (m, 1H,
7-H), 7.66 (s, 1H, 2-H), 8.22 (dd, Jˆ8.0, 1.7 Hz, 1H, 5-H).
13C NMR: 31.1 (Ca), 118.1 (C-8), 120.5 (C-400), 124.0,
124.2 (C-3,4a), 125.2, 126.1 (C-5,6), 130.8 (C-200,600),
131.8 (C-300,500), 133.7 (C-7), 137.9 (C-100), 153.2 (C-2),
156.7 (C-8a), 177.5 (C-4). Anal. calcd for C16H11BrO2
(315.16): C, 60.98; H, 3.52%. Found: C, 61.21; H, 3.37%.
1
1356, 1165, 1105, 766, 740, 707 cm21. H NMR: 6.38 (s,
1H, a-H), 7.40±7.52 (m, 6H, 6,8,200,300,500,600-H), 7.70 (m,
1H, 7-H), 8.14 (d, Jˆ1.0 Hz, 1H, 2-H), 8.22 (dd, Jˆ8.2,
1.9 Hz, 1H, 5-H). 13C NMR: 44.5 (Ca), 118.0 (C-8), 122.4
(C-400), 123.4, 125.0 (C-3,4a), 125.5, 126.0 (C-5,6), 129.7
(C-200,600), 129.7 (C-200,600), 131.8 (C-300,500), 134.0 (C-7),
138.3 (C-100), 156.2 (C-8a), 156.3 (C-2), 175.0 (C-4).
Anal. calcd for C16H10Br2O2 (394.06): C, 48.77; H,
2.56%. Found: C, 48.98; H, 2.43%.
3.1.15. 3-Benzyl-1-thiochromone (34a). Z-3-Benzylidene-
1-thiochromanone40 (Z-11a) (3.500 g, 13.871 mmol) was
reacted as given for chromone 33a (reaction period: 2 h)
to afford 2.017 g (58%) of thiochromone 34a as off-white
prisms. Mp 59±618C (diisopropyl ether). IR: 1614
(CvO1CvC), 1588, 1546, 1436, 1374, 1262, 1074, 948,
752, 744, 704 cm21. 1H NMR: 4.00 (s, 2H, a-H), 7.19±7.39
(m, 7H, 6,8-H1Ph), 7.52 (m, 1H, 7-H), 7.54 (s, 1H, 2-H),
8.60 (dd, Jˆ7.5, 1.3 Hz, 1H, 5-H). 13C NMR: 37.7 (Ca),
126.4, 126.5 (C-6,400), 127.4 (C-2), 128.6, 129.5
(C,200,300,500,600), 129.0, 131.0 (C-5,8), 131.6 (C-4a), 134.1
(C-7), 136.7, 137.2 (C-3,8a), 138.7 (C-100), 179.0 (C-4).
Anal. calcd for C16H12OS (252.33): C, 76.16; H, 4.79%.
Found: C, 76.35; H, 4.59%.
3.1.19. 3-(a-Ethoxybenzyl)-1-thiochromone (38a) and
3-(a-hydroxybenzyl)-1-thiochromone (39a). 3-Benzyl-1-
thiochromone (34a) (566 mg, 2.243 mmol), NBS (480 mg,
2.697 mmol), dibenzoyl peroxide (33 mg, 0.136 mmol) in
carbon tetrachloride (20 mL) was re¯uxed for 105 min. The
precipitated succinimide was ®ltered off, the ®ltrate was
washed with satd NaHCO3 solution and water, and dried.
After removal of the solvent under reduced pressure, abs.
ethanol (5 mL) was added and the mixture was re¯uxed for
1 h, then concentrated and submitted to column chroma-
tography (eluent: toluene±ethyl acetate (8:1, v/v)) to afford
330 mg (50%) of 3-(a-ethoxybenzyl)-1-thiochromone (38a)
and 140 mg (23%) 3-(a-hydroxybenzyl)-1-thiochromone
(39a).
3.1.16. NBS Bromination of 3-benzylchromone (33a). A
solution of 3-benzylchromone (33a) (808 mg, 3.420 mmol),
N-bromosuccinimide (NBS) (730 mg, 4.101 mmol) and
dibenzoyl peroxide (50 mg, 0.206 mmol) in carbon tetra-
chloride (30 mL) was re¯uxed for 6 h. The precipitated
succinimide was ®ltered off, the ®ltrate was washed with
satd NaHCO3 solution and water, and dried. The solvent was
removed under reduced pressure and residue was submitted
to column chromatography (eluent: toluene±ethyl acetate
(8:1, v/v)) to afford 203 mg (24%) of 3-(a-hydroxybenzyl)-
chromone (36a). Mp 122±1238C.
38a. Off-white prisms. Mp 96±97.58C (hexane±ethyl
acetate). IR: 3056, 2973, 2892, 1584, 1566, 1456, 1437,
1
1382, 1093, 1072, 745, 707 cm21. H NMR: 1.20 (t, Jˆ
7.2 Hz, 3H, CH2CH3), 3.49 (q, Jˆ7.2 Hz, 2H, CH2CH3),
5.74 (s, 1H, a-H), 7.16±7.53 (m, 8H, 6,7,8-H1Ph), 8.09
(d, Jˆ0.6 Hz, 1H, 2-H), 8.45 (dd, Jˆ9.1, 1.1 Hz, 1H,
5-H). 13C NMR: 15.3 (CH2CH3), 64.6 (CH2CH3), 77.7
(Ca), 126.4 (C-6), 127.2 (C-200,600), 127.5 (C-400), 128.2
(C-300,500), 128.9, 131.1 (C-5,8), 131.9 (C-4a), 137.0, 137.3
(C-3,8a), 140.7 (C-100), 177.9 (C-4). MS: 267 (100,
3.1.17. 3-(a-Bromo-4-chlorobenzyl)chromone (35b). A
solution of 3-(4-chlorobenzyl)chromone (33b) (1.360 g,
5.024 mmol), NBS (1.070 g, 6.012 mmol) and benzoyl

T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
2905
M1z2HCO), 252 (10, M1z2C2H4O), 221 (8,, M1z2HCO±
EtOH), 189 (87, M1z2HCO±PhH), 133 (12, C8H5S%), 115
(22), 89 (18), 77 (33). MS (Thermospray): 297 (36, M11),
283 (7), 251 (100, M112EtOH), 223 (19). Anal. calcd for
C18H16O2S (296.38): C, 72.95; H, 5.44%. Found: C, 73.12;
H, 5.40%.
chromone (40a). A solution of 3-(a-azidobenzyl)chromone
(8a) (416 mg, 1.500 mmol) and triphenylphosphine (500
mg, 1.906 mmol) in diisopropyl ether (15 mL) was re¯uxed
for 90 min and gave 608 mg (89%) of phosphimine 40a as
colourless plates on cooling. Mp 147±1488C (diisopropyl
ether±ethyl acetate), IR: 3054, 1630 (CvO), 1608, 1465,
1436 (P±Ph), 1392, 1344, 1312, 1286, 1214 (NvP), 1136,
1
39a. Off-white needles. Mp 130±1338C (hexane±diiso-
propyl ether). IR: 3446 (OH), 1610 (CvO1CvC), 1588,
1438, 1410, 1018, 864, 752, 714 cm21. 1H NMR: 4.05 (brs,
1H, a-OH), 5.94 (s, 1H, a-H), 7.12±7.56 (m, 8H, 5,6,7-
H1Ph), 7.64 (s, 1H, 2-H), 8.49 (dd, Jˆ7.7, 0.9 Hz, 1H,
1028, 1108, 760, 720 cm21. H NMR (DMSO-d6): 5.48 (d,
3JP±Haˆ20.8 Hz, 1H, a-H), 7.05±7.17 (m, 2H, 6,8-H),
7.37±7.61 (m, 20H, Ph), 7.73 (m, 1H, 7-H), 7.90 (dd, Jˆ
7.9, 1.4 Hz, 1H, 5-H), 8.66 (brs, 1H, 2-H). Anal. calcd for
C34H26NO2P (511.55): C, 79.83; H, 5.12; N, 2.74%. Found:
C, 79.55; H, 4.83; N, 2.57%.
13
5-H). C NMR: 73.3 (Ca), 126.4 (C-6), 126.8 (C-200,600),
127.7 (C-400), 128.4 (C-300,500), 128.8, 131.4 (C-5,8), 131.6
(C-4a), 135.5 (C-7), 137.1, 137.7 (C-3,8a), 141.0 (C-100),
179.5 (C-4). Anal. calcd for C16H12O2S (268.33): C,
71.62; H, 4.51%. Found: C, 71.59; H, 4.78%.
3.1.24. 3-[a-[(Triphenylphosphoranylidene)amino]benzyl]-
1-thiochromone (41a). 3-(a-Azidobenzyl)-1-thiochromone
(9a) (880 mg, 3.000 mmol) was reacted for 3 h as given for
40a to afford 1.355 g (86%) of phosphimine 41a as white
microcrystalline powder. Mp 144±146.58C (diisopropyl
ether±ethyl acetate). IR: 3054, 3022, 1608 (CvO), 1588,
1546, 1482, 1436 (P±Ph), 1346, 1208 (NvP), 1180, 1108,
3.1.20. 3-(a-Azido-4-chlorobenzyl)chromone (8b). A
solution of 3-(a-bromo-4-chlorobenzyl)chromone (35b)
(524 mg, 1.499 mmol) and NaN3 (293 mg, 4.507 mmol) in
abs. DMF (20 mL) was stirred for 3 and 30 min, poured into
water, extracted with dichloromethane (3£50 mL), the
combined organic phases were washed with water (2£
50 mL) and dried (CaCl2). The solvent was removed under
reduced pressure and the residues were crystallized from
hexane to give 390 mg (77%) of azide 8b. Mp 83±848C.
744, 722, 712 cm21 1H NMR (DMSO-d6): 5.67 (d,
.
3JP±Haˆ21.2 Hz, 1H, a-H), 7.01±7.15 (m, 2H, 6,8-H),
7.33±7.82 (m, 20H, Ph), 7.65 (m, 1H, 7-H), 8.22 (dd, Jˆ
8.0, 1.4 Hz, 1H, 5-H), 8.93 (s, 1H, 2-H). Anal. calcd for
C34H26NOPS (527.62): C, 77.40; H, 4.97; N, 2.65%.
Found: C, 77.41; H, 4.64; N, 2.43%.
3.1.21. 3-(a-Azido-4-bromobenzyl)chromone (8f). 3-(a,4-
Dibromobenzyl)chromone (35f) (394 mg, 1.000 mmol) was
reacted as given for 35b. Work-up and crystallization from
hexane afforded 304 mg (85%) of azide 8f as colourless
prisms. Mp 96±97.58C. IR: 2102 (N3), 1640 (CvC), 1622
(CvC), 1468, 1400, 1358, 1320, 1274, 1240, 1164, 1072,
1012, 856, 798, 766 cm21. 1H NMR: 6.00 (s, 1H, a-H), 7.36
(d, Jˆ8.7 Hz, 2H, 200,600-H), 7.40 (m, 1H, 6-H), 7.45 (m, 1H,
8-H), 7.53 (d, Jˆ8.7 Hz, 2H, 300,500-H), 7.71 (ddd, Jˆ8.6,
7.1, 1.5 Hz, 7-H), 7.98 (d, Jˆ0.9 Hz, 1H, 2-H), 8.20 (dd,
Jˆ8.0, 1.8 Hz, 1H, 5-H). 13C NMR: 59.8 (Ca), 118.1 (C-8),
122.5 (C-400), 123.5, 123.6 (C-3,4a), 125.4, 125.8 (C-5,6),
129.0 (C-200,600), 131.9 (C-300,500), 134.0 (C-7), 136.6 (C-100),
153.8 (C-2), 156.2 (C-8a), 175.8 (C-4). Anal. calcd for
C16H10BrN3O2 (356.17): C, 53.95; H, 2.83; N, 11.80%.
Found: C, 54.11; H, 2.66; N, 11.59%.
3.1.25. 3-Benzylchromanone (42a). A mixture of 3-(a-
azidobenzyl)chromone (8a) (372 mg, 1.342 mmol), ammo-
nium formate (315 mg), palladium on charcoal (50 mg) and
methanol (15 mL) was re¯uxed and the reaction was
monitored by TLC (hexane-acetone (6:1, v/v)). After 2
and 5 h, new batches of ammonium formate (400 mg
each) were added and the heating was continued until the
completion of the reduction (7 h and 30 min). The catalyst
was ®ltered off, washed with methanol, the combined
®ltrates were concentrated and submitted to column
chromatography (eluent: hexane±acetone (6:1, v/v)) to
give chromanone 42a (59 mg, 18%) as the sole product.
Colourless needles, Mp 55±578C, lit.62 mp 588C. IR
(neat): 2924, 1714, 1690 (CvO), 1604, 1478, 1454, 1324,
1302, 1220, 754 cm21. 1H NMR: 2.70 (dd, Jˆ13.5, 10.3 Hz,
1H, one of CH2Ph), 2.93 (m, 1H, 3-H), 3.29 (dd, Jˆ13.5,
3.9 Hz, 1H, other of CH2Ph), 4.16 (dd, Jˆ11.3, 8.0 Hz, 1H,
2-Hax), 4.37 (dd, Jˆ11.3, 4.5 Hz, 1H, 2-Heq), 6.94±7.06 (m,
2H, 6,8-H), 7.22±7.32 (m, 5H, Ph), 7.47 (ddd, Jˆ8.7, 8.4,
1.8 Hz, 1H, 7-H), 7.94 (dd, Jˆ8.1, 1.8 Hz, 1H, 5-H). 13C
NMR: 32.3 (Ca), 47.6 (C-3), 69.3 (C-2), 117.8 (C-8),
120.5 (C-4a), 121.4 (C-6), 126.6, 127.5, 128.7, 129.1
(C-5,200,300,400,500,600), 135.9 (C-7), 138.2 (C-100), 161.6
(C-8a), 193.7 (C-4).
3.1.22. 3-(a-Azidobenzyl)-1-thiochromone (9a) and 3-(a-
hydroxybenzyl)-1-thiochromone (39a). 3-Benzyl-1-thio-
chromone (34a) (505 mg, 2.001 mmol), NBS (428 mg,
2.405 mmol), dibenzoyl peroxide (30 mg, 0.124 mmol) in
carbon tetrachloride (18 mL) was re¯uxed for 1 and
45 min. The precipitated succinimide was ®ltered off, the
®ltrate was washed with satd NaHCO3 solution and water,
then dried and concentrated. The residue was dissolved in
abs. DMF (25 mL), NaN3 (391 mg, 6.013 mmol) was added
and the mixture was stirred for 3 h and 30 min at room
temperature, then poured into water and extracted with
dichloromethane (3£50 mL). After drying and evaporation,
the oily residue was submitted to column chromatography
(eluent: toluene±ethyl acetate (8:1, v/v)) to afford 487 mg
(82%) of azide 9a, mp 79.5±808C (hexane) and 37 mg
(6.9%) of alcohol 39a, mp 131±132.58C (hexane).
3.1.26. 3-(a-Aminobenzyl)chromone hydrochloride
(43a). A mixture of 3-(a-azidobenzyl)chromone (8a)
(416 mg, 1.500 mmol), tin(II)-chloride monohydrate (762
mg, 3.670 mmol) and methanol (17 mL) was stirred for 5
days at room temperature, then poured into 4% NaOH
solution and extracted with chloroform. The solvent was
removed under reduced pressure, the residue was dissolved
in abs. diethyl ether and satd solution of hydrogen chloride in
abs. diethyl ether was added dropwise. The yellowish pre-
cipitate was ®ltered off and crystallized from hexane±abs.
3.1.23. 3-[a-[(Triphenylphosphoranylidene)amino]benzyl]-

2906
T. Patonay et al. / Tetrahedron 57 (2001) 2895±2907
12. Nair, V.; George, T. G. Tetrahedron Lett. 2000, 41, 3199±
3201.
Â
13. Litkei, G.; Mester, T.; Patonay, T.; Bognar, R. Liebigs Ann.
Chem. 1979, 174±180.
ethanol (3:1, v/v) mixture to give 58 mg (13%) of pure salt
43a as white microcrystalline powder. Mp 191±1968C
(dec.). IR: 2868 (br, NH3%), 1644 (CvO), 1610 (CvC),
1506, 1466, 1355, 1112, 762, 697 cm21
.
1H NMR
(DMSO-d6): 5.60 (s, 1H, Ha), 7.39±7.58, 7.64±7.74 (m,
Â
14. Patonay, T.; Bognar, R.; Litkei, G. Tetrahedron 1984, 40,
2555±2562.
15. Patonay, T.; Litkei, Gy.; Bognar, R. Acta Chim. Acad. Sci.
7H, 6,8-H1Ph), 7.88 (ddd, Jˆ8.6, 8.4, 1.6 Hz, 1H, 7-H),
8.07 (dd, Jˆ7.9, 1.4 Hz, 1H, 5-H), 9.26 (brs, 3H, NH3%). 13
C
Â
Hung. 1981, 108, 135±145.
16. Harvey, G. R.; Ratts, K. W. J. Org. Chem. 1966, 31, 3907±
3910.
NMR (DMSO-d6): 56.0 (Ca), 118.8 (C-8), 121.3 (C-3),
123.2 (C-4a), 125.2 (C-6), 126.2 (C-5), 127.7, 128.8
(C-200,300,500,600), 128.6 (C-400), 135.1, 136.5 (C-7,100),
156.0, 156.2 (C-2,8), 175.4 (C-4). Anal. calcd for
C16H14ClNO2 (287.74): C, 66.79; H, 4.90; N, 4.87. Found:
C, 66.95; H, 5.10; N, 4.59.
17. Henn, A.; Hickey, D. M. B.; Moody, C. J.; Rees, C. W.
J. Chem. Soc., Perkin Trans 1 1984, 2189±2196.
18. Knittel, D. Synthesis 1985, 186±188.
Â
19. L'Abbe, G.; Dekerk, J. P.; Van Stappen, P. Bull. Soc. Chim.
Belg. 1981, 90, 1073±1074.
3.1.27. 3-(a-Aminobenzyl)-1-thiochromone hydrochloride
(44a). 3-(Azidobenzyl)-1-thiochromone (9a) (293 mg,
0.999 mmol) was treated with SnCl2´H2O as given for 43a
to yield 126 mg (42%) of pure salt 44a as white prisms. Mp
198±2038C. IR: 2832 (br, NH3%), 1607 (CvO1CvC),
20. Hemetsberger, H.; Knittel, D.; Neidmann, H. Monatsh. Chem.
1970, 101, 161±165.
21. Hemetsberger, H.; Knittel, D.; Neidmann, H. Monatsh. Chem.
1972, 103, 194±204.
1590, 1438, 1384, 1093, 928, 771, 741, 705 cm21
.
1H
22. Kanomata, N.; Nakata, T. Heterocycles 1998, 48, 2551±2558.
23. Palacios, F.; Ochoa de Retana, A. M.; Gil, J. I.; Ezpeleta, J. M.
J. Org. Chem. 2000, 65, 3213±3217.
NMR (DMSO-d6): 5.79 (s, 1H, Ha), 7.36±7.48 (m, 3H,
300,400,500-H), 7.61±7.84 (m, 3H, 6,200,600-H), 7.97 (d,
Jˆ7.0 Hz, 1H, 7-H), 8.40 (dd, Jˆ7.9, 1.3 Hz, 1H, 5-H),
8.91 (s, 1H, 2-H), 9.24 (brs, 1H, NH3%). 13C NMR
(DMSO-d6): 53.8 (Ca), 127.6, 127.8, 128.6, 128.7
(C-5,6,8,400), 128.3, 128.8 (C-200,300,500,600), 130.9 (C-4a),
132.1, 132.5 (C-3,7), 136.6 (C-2), 136.8 (C-8a), 139.7
(C-100), 177.2 (C-4). Anal. calcd for C16H14ClNOS
(303.80): C, 63.26; H, 4.64; N, 4.61. Found: C, 61.99; H,
4.66; N, 4.52.
24. Smolinsky, G. J. Org. Chem. 1962, 27, 3557±3559.
25. Silva, A. M. S.; Vieira, J. S.; Cavaleiro, J. A. S.; Patonay, T.;
Â
Levai, A. Heterocycles 1999, 51, 481±488.
26. Rybinskaya, M. I.; Nesmeyanov, A. N.; Kochetkov, N. K.
Usp. Khim. 1969, 38, 961±1008.
27. Raghavan, R. S.; Velayutham, K.; Rajendran, V. Indian J.
Chem. 1984, 23A, 466±469.
28. Sharma, T. C.; Bokadia, M. M. Indian J. Chem. 1976, 14B,
65±66.
29. Reddy, N. J.; Sharma, T. C. Indian J. Chem. 1979, 17B, 645±
646.
Acknowledgements
30. Balasubramanian, A.; Selvanayagam, D. S. Acta Cienc.
Indica, Chem. 1988, 14, 99±100 (Chem. Abstr., 1990, 112,
178229a).
This work was ®nancially supported by Hungarian Scien-
ti®c Research Found (OTKA T22290). Special thanks are
due to Mrs E. Riman and Mrs M. Nagy for their precise and
innovative technical help.
31. Doshi, A. G.; Ghiya, B. J. Indian J. Chem. Soc. 1986, 63, 404±
405.
Â
Â
32. Raja, T. K. Indian J. Chem. 1980, 19B, 812±813.
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39, 4035±4038.
34. Soni, P. A.; Ghiya, B. J. Curr. Sci. 1972, 41, 137.
35. Reddy, N. J.; Bokadia, M. M.; Sharma, T. C.; Donnelly, J. A.
J. Org. Chem. 1981, 46, 638±641.
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