Rearrangement of substituted 2,4,4,6-tetraaryl-4H-thiopyrans to triaryl-3aH-benzo[3,4]cyclopenta[1,2-b]thiophene

Article abstract of DOI:10.1135/cccc20041631

An intensive bromination of 2,6-diaryl-4,4-diphenyl-4H-thiopyrans can lead through 3,5-dibromo derivatives to unexpected 2,8-diaryl-3-bromo- and 2,8-diaryl-3,5-dibromo-3a-phenyl-3aH-benzo[3,4]cyclopenta[1,2-b]thiophene as demonstrated on examples where the respective aryl groups are phenyl or 4-fluorophenyl. On the other hand, analogous spiro-[fluorene-9,4′- thiopyran]s do not exhibit the rearrangement evidently due to a rigid conformation of the fluorene moiety. The reaction mechanism for the rearrangement is proposed.

Full text of DOI:10.1135/cccc20041631

Rearrangement of Substituted 2,4,4,6-Tetraaryl-4H-thiopyrans
1631
REARRANGEMENT OF SUBSTITUTED
2,4,4,6-TETRAARYL-4H-THIOPYRANS TO
TRIARYL-3aH-BENZO[3,4]CYCLOPENTA[1,2-b]THIOPHENE
c
d
Jiří KROULÍKa1,*, Jan ČEJKAb1, Petr SEDMERA , Alexandr JEGOROV ,
b2
a
Bohumil KRATOCHVÍL and Josef KUTHAN
a
Department of Organic Chemistry, Institute of Chemical Technology, Prague,
166 28 Prague 6, Czech Republic; e-mail: kroulimek@seznam.cz
Department of Solid State Chemistry, Institute of Chemical Technology, Prague,
166 28 Prague 6, Czech Republic; e-mail: jan.cejka@vscht.cz, bohumil.kratochvil@vscht.cz
Institute of Microbiology, Academy of Sciences of the Czech Republic,
142 20 Prague 4, Czech Republic; e-mail: sedmera@biomed.cas.cz
IVAX-CR., Research Unit, Branišovská 31, 370 05 České Budějovice, Czech Republic;
e-mail: alexandr_jegorov@ivax-cr.com
1
b
c
1
2
d
Received Jan uary 28, 2003
Accepted February 23, 2004
An in ten sive brom in ation of 2,6-diaryl-4,4-diph en yl-4H-th iopyran s can lead th rough
3,5-dibrom o derivatives to un expected 2,8-diaryl-3-brom o- an d 2,8-diaryl-3,5-dibrom o-
3a-ph en yl-3aH-ben zo[3,4]cyclopen ta[1,2-b]th ioph en e as dem on strated on exam ples wh ere
th e respective aryl groups are ph en yl or 4-fluoroph en yl. On th e oth er h an d, an alogous spiro-
[fluoren e-9,4′-th iopyran ]s do n ot exh ibit th e rearran gem en t eviden tly due to a rigid con for-
m ation of th e fluoren e m oiety. Th e reaction m ech an ism for th e rearran gem en t is proposed.
Keyw ord s: Th iopyran s; Brom in ation ; Ben zo[3,4]cyclopen ta[1,2-b]th ioph en e; Th iapen talen e;
Rearran gem en ts; Sulfur h eterocycles.
Th e 2,4,4,6-tetraaryl-4H-th iopyran s are in terestin g substan ces capable to
un dergo color ch an ges caused by illum in ation in th e solid state1. An alter-
n ative way h ow to m odify th e paren t 2,4,4,6-tetraph en yl-4H-th iopyran
skeleton is in troduction of substituen ts to position s 3 an d 5. A h igh reacti-
vity of th e h eterocycle towards electroph ilic agen ts2,3 m ay result in un usual
rin g tran sform ation s affordin g products of un expected structures. Th us, a
rearran gem en t of 2,4,4,6-tetraaryl-4H-th iopyran s th rough a 3,5-dich loro
derivative in term ediate to trich loro bicycles h as been observed4 after pro-
lon ged ch lorin ation at room tem perature (Sch em e 1). Alth ough a sim ilar
3,5-brom in ation h as also been reported3, n o an alogous tan dem rearran ge-
m en t h as yet been in vestigated. In th is paper we presen t n ew results sh ow-
in g th at a prolon ged in ten sive brom in ation of 2,6-diaryl-4,4-diph en yl-
Collect. Czech. Chem. Commun. (Vol. 69) (2004)
doi:10.1135/cccc20041631

1632
Kroulík et. al.:
4H-th iopyran s 1 an d 2 leads to rearran ged products th e structures of wh ich
sign ifican tly differ from th ose of th e aforem en tion ed ch lorin ation 4 se-
quen ce. In addition , it is also dem on strated th at spirocyclic 4H-th iopyran 3
beh aves differen tly affordin g n o rearran ged products durin g brom in ation .
SCHEME 1
Ch lorin e-in duced isom erization of 2,4,4,6-tetraaryl-4H-th iopyran s4
RESULTS AND DISCUSSION
Preparation of com poun ds1c 1–3 as well as brom in ation 3 of 1 givin g 4 h ave
been described previously. It h as been establish ed th at fluoro derivative 2
an d th e spiro-4H-th iopyran 3 can be con verted to th e correspon din g
3,5-dibrom o derivatives 5 an d 6 un der sim ilar con dition s (3 equivalen ts of
Br2, startin g at 0 °C). However, if th e brom in ation s were carried out with a
large excess of brom in e (8 equivalen ts of Br2) in substan tially sm aller
am oun ts of carbon disulfide at 20 °C, 4H-th iopyran 1 gave a m ixture con -
tain in g two substan ces in addition to m in or am oun ts of 3,5-dibrom o deriv-
ative 4. An alogous brom in ation of 4H-th iopyran 2 led to a m ixture com -
posed of two products (1:1, HPLC) an d a m in or am oun t of 3,5-dibrom o de-
rivative 5. Fin ally, by m ore in ten sive brom in ation (10 equivalen ts of Br2),
4H-th iopyran 2 gave a h igh yield of sin gle com poun d (67% yield, after sep-
aration ), wh ich was en tirely differen t from 3,5-dibrom o derivative 5. Fur-
th erm ore, com parative brom in ation experim en ts on an alytical scale
(HPLC) with dibrom o derivative 4 sh owed th at th e sam e substan ces were
form ed. NMR in vestigation s in dicated th at n ew com poun ds obtain ed by in -
ten sive brom in ation exh ibit th e sam e skeleton of a lower m olecular sym -
m etry in com parison with 3,5-dibrom o derivatives 4 an d 5.
Th e X-ray structure of un expected product given in Fig. 1 revealed th at
th e in vestigated crystallin e substan ce was in fact 3,5-dibrom o-2,3a,8-tri-
ph en yl-3aH-ben zo[3,4]cyclopen ta[1,2-b]th ioph en e (7) (Sch em e 2). Hen ce, it
could be con cluded th at th e secon d com poun d presen t in th e reaction m ix-
ture wh ich was isolated by preparative TLC from m oth er liquors (see Exper-
im en tal) possesses th e form ula 8. An alogously, form ula 9 can be assign ed to
rearran ged product from 4H-th iopyran 2. Con sequen tly, it was obvious th at
th e first brom in ation of fluoro derivative 2 (8 equivalen ts of Br2) afforded
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Rearrangement of Substituted 2,4,4,6-Tetraaryl-4H-thiopyrans
1633
m ixture of 9 an d plausible in term ediate 10 (vide supra), but th e com poun d
10 was n ot isolated. NMR data of com poun ds 7–9 agree with th ese struc-
tures. Detailed an alysis of 9 in wh ich ph en yls attach ed to C-2 an d C-6 were
labeled by fluorin e clearly revealed th e fate of all ph en yl groups. Th is con -
clusion was furth er supported by partial catalytic h ydrogen ation of
3,5-dibrom o derivative 7 on a Pd catalyst affordin g 3-brom o derivative 8
un der h ydrogen olysis of th e less sterically h in dered brom in e in position 5
(Sch em e 2).
It is easily recogn izable th at h ydrogen brom ide elim in ation took place
durin g th e rearran gem en ts 4 to 8 an d 5 to 10, respectively, an d th en subse-
quen t brom in ation s 8 to 7 an d 10 to 9 com pleted th e reaction path s. Th e
regiospecificity in th e fin al brom in ation (at C-5) can be explain ed by
vin ylogous sulfide-like π-electron sh ifts in appropriate tran sition states as
sh own for brom in ation 8 to 7 in th e proposed m ech an ism , discussed below
(Sch em e 3).
FIG. 1
ORTEP 6 view of structure of dibrom o com poun d 7
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1634
Kroulík et. al.:
SCHEME 2
Brom in e-in duced isom erization of 2,4,4,6-tetraph en yl-4H-th iopyran s
SCHEME 3
Proposed altern ative m ech an ism of brom in e-in duced isom erization
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Rearrangement of Substituted 2,4,4,6-Tetraaryl-4H-thiopyrans
1635
On th e con trary, n o rearran ged products h ave been observed in th e an al-
ogous in ten sive brom in ation of spirocyclic 4H-th iopyran 3. On ly
3′,5′-dibrom o (6), 2,3′,5′-tribrom o (11) an d 2,3′,5′,7-tetrabrom o (12), deriv-
atives of 2′,6′-diph en ylspiro[fluoren e-9,4′-th iopyran ] (3), h ave been de-
tected an d isolated (Sch em e 4). Disubstitution of th e th iopyran rin g was de-
1
duced from th e absen ce of H-3′ an d H-5′ sin glets in all H NMR spectra. Th e
couplin g pattern of th e fluoren e proton s (an ABC system ) in com poun ds 11
an d 12 was con sisten t eith er with 6- or 7-substitution . Th e X-ray diffraction
an alysis of com poun d 11 (Fig. 2) resolved th is problem in favour of th e lat-
ter altern ative. Con sequen tly, structure 12 was assign ed to th e tetrabrom o
derivative. Both com poun ds 6 an d 12 exh ibited th e expected sym m etry in
th eir 1H an d 13C NMR spectra. Th e regioselectivity in brom in ation of th e
fluoren e m oiety (2,7) m igh t be som ewh at surprisin g but it is apparen tly
con trolled by a biph en yl-like π-electron structure an d is n ot an effect of th e
sp3-carbon (C-9).
SCHEME 4
Brom in ation of 2′,6′-diph en ylspiro[fluoren e-9,4′-th iopyran ] (3)
Th e above described h eterocyclic rearran gem en ts 4 to 7 an d 5 to 9 an d
th eir absen ce in th e case of spiroh eterocycle 6 m ade possible to propose an
altern ate m ultistep reaction m ech an ism given in Sch em e 3. To support th e
path it h as been establish ed th at in teraction of dry h ydrogen brom ide with
4H-th iopyran 4 does n ot lead to an observable ch an ge of th e startin g com -
poun d. Hen ce, brom in e h as to assist in th e proton ation of substrate 4, per-
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1636
Kroulík et. al.:
FIG. 2
ORTEP 6 view of structure of tribrom ospiro[fluoren e-9,4′-th iopyran ] 11
FIG. 3
ORTEP 6 view of structure of dibrom oth iopyran 4
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Rearrangement of Substituted 2,4,4,6-Tetraaryl-4H-thiopyrans
1637
→
h aps via an equilibrium like Br2 + HBr
HBr3, in wh ich th e resultin g h y-
←
drogen tribrom ide5 acts as a m ore powerful proton atin g agen t in com pari-
son with sim ple h ydrogen brom ide. A sim ilar but less efficien t in fluen ce
h as been detected (HPLC) in attem pts to ach ieve th e rearran gem en t 4 to 7
by brom in ation in th e presen ce of trifluoroacetic acid.
Th e absen ce of rearran ged brom in ation products from spiroh eterocycles
3 or 6 can be ration alized. An alysis of th e plausible geom etry of in term edi-
ate ion 13 (Sch em e 4) suggests th at th e side ch ain bearin g th e positive
ch arge is n ot able to approach an y on e of th e ben zen oid rin gs because of
th e rigidity of th e fused biph en yl-like m oiety. On th e oth er h an d, a h igh er
con form ation al flexibility of th e ph en yl groups in position 4 m akes th e ap-
proach possible an d, con sequen tly, th e secon d five-m em bered rin g closure
can take place (Sch em e 3).
In addition , we exten d th e crystal structure set of com poun ds 7 an d 11
(Table I) with dibrom o derivative 4 (Fig. 3), th e structure of wh ich is un am -
biguous; th is com poun d is th e in term ediate of th e presen ted isom erization .
Furth erm ore, differen t ph otoch em ical beh aviour of th is com poun d in th e
crystallin e state is rem arkable3, because th e in troduction of a substituen t
in to position s 3 an d 5 probably causes dram atic ch an ges in th e ph otoch em -
ical system . It sh ould be n oted th at n o X-ray data of related 3 an d/or 5 (di)-
substituted 2,4,4,6-tetraph en yl-4H-th iopyran s h ave been publish ed so far.
In con clusion , th e un preceden ted brom in e-in duced isom erization of
2,4,4,6-tetraph en yl-4H-th iopyran in to 3,5-dibrom o-2,3a,8-triph en yl-3aH-
ben zo[3,4]cyclopen ta[1,2-b]th ioph en e derivatives h as been described toge-
th er with m ech an istic con sideration s explain in g th e process. Th is un ex-
pected reaction is m ost likely catalyzed by h ydrogen tribrom ide or perbro-
m ide, form ed in th e reaction of excessive brom in e with h ydrogen brom ide
from 3,5-dibrom in ation of th e startin g th iopyran .
EXPERIMENTAL
Tem perature data are un corrected. Meltin g poin ts were determ in ed usin g a Boetius appara-
tus. Th e reaction s were m on itored by reverse-ph ase HPLC usin g an Ecom LCP 4000 pum p
on Separon SGX C18 colum n (3 × 150 m m , particle size 5 µm , Tessek, Czech Republic;
m eth an ol–water 9:1; UV detection at 254 n m ), an d TLC on Silufol UV254 (Kavalier Sázava,
Czech Republic). Preparative colum n ch rom atograph y: silica gel (Aldrich 130–270 m esh ),
an d preparative TLC (plates 20 × 20 × 0.05 cm , silica gel 5–25 µm , Aldrich ; UV detection at
254 n m ). Sam ples for elem en tal an alysis were repeatedly crystallized, un til a con stan t m elt-
in g poin t was obtain ed an d th en dried in vacuo (150 Pa) over paraffin an d P4O10 at 110 °C
or at room tem perature. Startin g th iopyran s 1–3 were prepared as described elsewh ere1c
.
IR spectra (ν, cm –1; CHCl3) were taken on a FTIR spectrom eter Nicolet 740. NMR spectra
(δ, ppm ; J, Hz) were m easured on a Varian VXR-400 or In ova-400 at 400 an d 100 MHz for
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1638
Kroulík et. al.:
TABLE I
Crystal structure determ in ation of 4, 7, an d 11
Com poun d
4
7
11
Form ula
Mr
C29H20Br2S
560.35
C29H18Br2S
558.34
C29H17Br3S·C2H6O
683.27
Space group
a, Å
P-1
P21
P21/c
11.063(3)
11.264(2)
12.110(7)
96.29(3)
117.12(3)
110.60(2)
2; 1189.5(10)
1.564
7.548(3)
13.129(3)
11.868(3)
11.959(2)
13.339(2)
17.513(3)
b, Å
c, Å
α, °
β, °
105.03(2)
92.14(1)
γ, °
Z; V, Å3
2; 1135.8(6)
1.632
4; 2791.7(8)
1.626
ρ
calc, g cm –3
µ, m m
5.244
5.492
6.292
F(000)
560.0
556.0
1352.0
Crystal dim en sion s, m m
0.14 × 0.46 × 0.56 0.21 × 0.25 × 0.53 0.14 × 0.28 × 0.46
Diffractom eter an d
En raf–Non ius CAD4; 1.54184
radiation used λ, Å
Scan tech n ique
Tem perature, K
ω/2θ-scan
293
293
293
No. an d θ ran ge of reflection s for
lattice param eter refin em en t, °
20, 48–50
20, 38–40
20, 48–50
Ran ge of h, k, an d l
–11→11,
–11→11, –12→12
0→9, –16→16,
–14→14
–14→14, 0→16,
0→21
Total n um ber of reflection s m easured
2θ ran ge, °
5941
8–110
5040
8–150
10 688
8–136
No. of observed un ique reflection s
Criterion for observed reflection s
Fun ction m in im ized
5800
4650
4563
I > 1.96 Io
w (| F | − | F | )2
o
c
∑
Weigh tin g sch em e
Ch ebych ev polyn om ial
Param eters refin ed
370
308
335
Value of R, wR, an d S
0.0566, 0.0677,
1.1438
0.0443, 0.0401,
1.0934
0.0736, 0.0782,
1.1092
Ratio of th e m axim um least-squares
sh ift to e.s.d. in th e last cycle
0.002
0.0004
0.001
Maxim um an d m in im um h eigh ts
–1.40, 1.46
–1.34, 1.35
–0.99, 0.90
in fin al ∆ρ m ap, e Å–3
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Rearrangement of Substituted 2,4,4,6-Tetraaryl-4H-thiopyrans
1639
1H an d 13C NMR, respectively, in CDCl3 solution s at 25 or 30 °C. Th e reported assign m en ts
are based on COSY, COSY optim ized for th e detection of sm all couplin gs, HETCOR,
HETCOR optim ized for th e observation of gem in al an d vicin al couplin gs, HMQC, HMBC,
an d 1D-TOCSY.
X-ray Structure Determ in ation s
Th e crystal data an d experim en tal con dition s for com poun ds 4, 7, an d 11 are sum m arized
in Table I. Th ree stan dard reflection s were m on itored durin g data collection , sh owin g lower
th an 3.5% in ten sity fluctuation . Decay correction an d th e ψ-scan 7 em pirical absorption pro-
8
cedure were applied. Th e structures were solved usin g SIR92 direct m eth ods. Th e h ydrogen
atom s were set an d kept fixed in th e ideal geom etry for 7 an d 11 or located from ∆ρ-m ap for
4. In th is particular case th e position al an d Uiso th erm al param eters of h ydrogen atom s were
refin ed. Th e least-squares refin em en ts were perform ed in CRYSTALS 9 com putin g system by
m in im izin g th e fun ction ∑w(|Fo| – |Fc|)2, wh erein w represen ts Ch ebysh ev’s polyn om ial
weigh tin g sch em e10. CCDC 196172 (for 4), 196173 (for 7) an d 196174 (for 11) con tain th e
supplem en tary crystallograph ic data for th is paper. Th ese data can be obtain ed free of
ch arge via www.ccdc.cam .ac.uk/con ts/retrievin g.h tm l (or from th e Cam bridge Crystallo-
graph ic Data Cen tre, 12, Un ion Road, Cam bridge, CB2 1EZ, UK; fax: +44 1223 336033; or
deposit@ccdc.cam .ac.uk).
3,5-Dibrom o-2,6-bis(4-fluoroph en yl)-4,4-diph en yl-4H-th iopyran (5)
Brom in e (0.55 g, 3.42 m m ol) was added dropwise at 0 °C un der stirrin g to a solution of
th iopyran 2 (0.5 g, 1.14 m m ol) in carbon disulfide (15 m l). Th e reaction m ixture was kept at
th e sam e tem perature for 1 h an d th en at room tem perature overn igh t. Th e reaction m ix-
ture was decom posed with a saturated aqueous solution of sodium sulfite, treated with di-
ch lorom eth an e an d th e collected organ ic extracts were dried over an h ydrous m agn esium
sulfate. Evaporation of th e solven t in vacuo an d crystallization of th e residue from ben zen e–
eth an ol afforded 0.474 g (70%) of colorless crystals of dibrom o derivative 5, m .p. 216–218 °C.
For C29H18Br2F2S (596.3) calculated: 58.41% C, 3.04% H, 26.80% Br, 5.38% S; foun d:
58.01% C, 3.48% H, 26.33% Br, 5.66% S. IR: 1599. 1H NMR: 7.04–7.13 (4 H, m , o-C6H4F);
7.34–7.44 (6 H, m , 4-Ph , m-, p-); 7.45–7.52 (4 H, m , 4-Ph , o-); 7.76–7.01 (4 H, m , m-C6H4F).
13C NMR: 64.79 (C-4); 115.67 d (m-C6H4F, J(C,F) = 21.8); 116.64 (C-3, C-5); 127.40 (2 C,
4-Ph , p-); 127.61 (4 C, 4-Ph , o-); 129.38 (C-2, C-6); 130.45 (4 C, 4-Ph , m-); 131.06 d (4 C,
o-C6H4F, J(C,F) = 8.0); 133.80 d (i-C6H4F, J(C,F) = 3.4); 141.83 (2 C, 4-Ph , i-); 162.75 d
(p-C6H4F, J(C,F) = 249.1).
3′,5′-Dibrom o-2′,6′-diph en ylspiro[fluoren e-9,4′-th iopyran ] (6)
Th e sam e procedure with brom in e (0.599 g, 3.75 m m ol) an d spiroth iopyran 3 (0.5 g,
1.25 m m ol) in carbon disulfide (15 m l) an d recrystallization from ben zen e–eth an ol afforded
0.454 g (71%) of colorless crystals of dibrom o derivative 6, m .p. 224–225 °C. For C29H18Br2S
(558.3) calculated: 62.39% C, 3.25% H, 28.62% Br, 5.74% S; foun d: 61.32% C, 3.22% H,
28.62% Br, 6.04% S. IR: 1604, 1577. 1H NMR: 7.39 (2 H, m , 2 × p-); 7.40 (4 H, m , 4 × o-);
7.44 (4 H, m , 4 × m-); 7.51 (2 H, m , H-3, H-6); 7.52 (2 H, m , H-2, H-7); 7.79 (2 H, m , H-1,
H-8); 7.90 (2 H, m , H-4, H-5). 13C NMR: 65.55 (C-9 ≡ C-4′); 112.40 (C-3′, C-5′); 119.88 (C-1,
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1640
Kroulík et. al.:
C-8); 124.82 (C-4, C-5); 128.26 (C-2, C-7); 128.51 (C-3, C-6); 128.87 (4 × o-); 128.91 (2 × p-);
129.08 (4 × m-); 130.92 (C-2′, C-6′); 137.47 (2 × i-); 140.79 (C-4a, C-4b); 151.30 (C-8a, C-9a).
3,5-Dibrom o-2,3a,8-triph en yl-3aH-ben zo[3,4]cyclopen ta[1,2-b]th ioph en e (7)
Brom in e (6.25 g, 39.1 m m ol) was added at room tem perature un der stirrin g to a solution of
th iopyran 1 (2 g, 4.97 m m ol) in carbon disulfide (12.5 m l) an d th e reaction was allowed to
con tin ue at room tem perature overn igh t. Th e dich lorom eth an e (100 m l) an d saturated aque-
ous solution of sodium sulfite (200 m l) were added an d th e stirrin g con tin ued for 3 h . An
an alogous work-up procedure to th at described above an d rem oval of th e solven t afforded
th e crude product. Th e residue crystallized with petroleum –eth er:dich lorom eth an e (1:1).
Recrystallization from ben zen e–eth an ol yielded yellowish crystals (1.50 g, 54%) of th e title
com poun d 7, m .p. 216–219 °C. For C29H18Br2S (558.3) calculated: 62.39% C, 3.25% H,
28.62% Br, 5.74% S; foun d: 62.49% C, 3.24% H, 28.29% Br, 5.49% S. IR: 1595, 1566.
1H NMR: 7.36 (2 H, m , 3a-Ph , m-); 7.36 (1 H, m , 3a-Ph , p-); 7.36 (2 H, m , 3a-Ph , o-); 7.38
(1 H, m , 2-Ph , p-); 7.44 (2 H, m , 2-Ph , m-); 7.48 (1 H, m , 8-Ph , p-); 7.48 (1 H, d, J = 8.2, H-7);
7.52 (2 H, m , 8-Ph , m-); 7.52 (2 H, m , 8-Ph , o-); 7.56 (1 H, dd, J = 8.2, 1.9, H-6); 7.69 (2 H,
m , 2-Ph , o-); 7.83 (1 H, d, J = 1.9, H-4). 13C NMR: 77.31 (C-3a); 108.80 (C-3); 119.82 (C-5);
121.69 (C-7); 126.51 (2 C, 3a-Ph , m-); 127.87 (3a-Ph , p-); 128.17 (2 C, 8-Ph , o-); 128.36
(2-Ph , p-); 128.47 (2 C, 2-Ph , m-); 128.78 (C-4); 128.82 (2 C, 8-Ph , m-); 128.85 (8-Ph , p-);
128.88 (2 C, 3a-Ph , o-); 129.42 (2-Ph , p-); 131.13 (C-6); 132.45 (8-Ph , i-); 133.23 (2-Ph , i-);
138.54 (3a-Ph , i-); 141.28 (C-8); 143.52 (C-7a); 144.74 (C-2); 147.20 (C-8a); 150.54 (C-3b).
3-Brom o-2,3a,8-triph en yl-3aH-ben zo[3,4]cyclopen ta[1,2-b]th ioph en e (8)
Preparation from compound 7. In a solution of com poun d 7 (1.5 g, 2.69 m m ol) an d trieth yl
am in e (4 m l) in ben zen e (200 m l) purged with argon was suspen ded 0.20 g of Pd/C (10%;
Aldrich ) an d th e m ixture was stirred un der h ydrogen at room tem perature for 2 days. Th e
resultin g m ixture of th e startin g dibrom o derivative 7 an d product 8 (1:1, HPLC) was filtered
an d evaporated in vacuo. Colum n ch rom atograph y (100 g, gradien t elution with petroleum
eth er–dich lorom eth an e 30:1–25:1) afforded 0.387 g (30%) of m on obrom o derivative 8 (m .p.
207–209 °C, ben zen e–EtOH).
Preparation from thiopyran 1. Th e m oth er liquors after crystallization of com poun d 7 were
com bin ed an d subjected to colum n ch rom atograph y (150 g, elution with petroleum eth er–
dich lorom eth an e 15:1–3:1). Fraction 1 afforded 0.054 g (2%) of th e com poun d, wh ich was
iden tical with 3,5-dibrom o derivative 4 (m .p. 210–212 °C, h eptan e; lit.3a m .p. 211–212 °C).
Fraction 2 afforded 0.018 g (0.8%) of com poun d 8, wh ich was crystallized from h eptan e,
m .p. 206–209 °C. For C29H19BrS (479.4) calculated: 72.80% C, 4.01% H, 16.51% Br, 6.69% S;
foun d: 72.83% C, 4.27% H, 16.60% Br, 6.37% S. IR: 1595. 1H NMR: 7.23 (1 H, ddd, J = 7.5,
7.5, 1.2, H-5); 7.26 (2 H, m , 3a-Ph , m-); 7.26 (1 H, m , 3a-Ph , p-); 7.27 (2 H, m , 3a-Ph , o-);
7.35 (1 H, m , 2-Ph , p-); 7.35 (2 H, m , 2-Ph , m-); 7.37 (1 H, m , 8-Ph , p-); 7.38 (1 H, ddd, J =
7.7, 7.5, 1.3, H-6); 7.45 (2 H, m , 8-Ph , m-); 7.50 (2 H, m , 8-Ph , o-); 7.58 (1 H, ddd, J = 7.7,
1.2, 0.5, H-7); 7.62 (2 H, m , 2-Ph , o-); 7.66 (1 H, ddd, J = 7.5, 1.3, 0.5, H-4). 13C NMR: 77.47
(C-3a); 109.60 (C-3); 120.67 (C-7); 125.61 (C-4); 125.93 (C-5); 126.60 (2 C, 3a-Ph , m-);
127.60 (3a-Ph , p-); 128.06 (8-Ph , p-); 128.28 (2 C, 8-Ph , o-); 128.39 (2 C, 2-Ph , o-); 128.41
(2 C, 2-Ph , m-); 128.62 (C-6); 128.71 (4 C, 3a-Ph , o-; 8-Ph , m-); 129.26 (2-Ph , p-); 132.93
(8-Ph , i-); 133.46 (2-Ph , i-); 139.31 (3a-Ph , i-); 142.11 (C-8); 144.51 (C-2); 146.69 (C-8a);
148.73 (C-3b).
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Rearrangement of Substituted 2,4,4,6-Tetraaryl-4H-thiopyrans
1641
Brom o Derivatives of 2′,6′-Diph en ylspiro[fluoren e-9,4′-th iopyran ] 6, 11, an d 12
Brom in e (3.13 g, 19.6 m m ol) was added at room tem perature un der stirrin g to a solution of
spiroth iopyran 3 (1 g, 2.50 m m ol) in carbon disulfide (6 m l), th e reaction was allowed to
con tin ue at room tem perature overn igh t. Th e sam e work-up procedure as in th e case of
com poun d 7 afforded a m ixture, th e h alf of wh ich was subjected to colum n ch rom atogra-
ph y on silica gel (200 g, cycloh exan e–ch loroform 8:1).
2,3′,5′,7-Tetrabromo-2′,6′-diphenylspiro[fluorene-9,4′-thiopyran] (12). Fraction 1 afforded
0.167 g (9.3%) of com poun d 12, wh ich was recrystallized from eth an ol–cycloh exan e, m .p.
284–286 °C (subl.). For C29H16Br4S (716.1) calculated: 48.64% C, 2.25% H, 44.63% Br,
4.48% S; foun d: 48.29% C, 2.54% H, 44.54% Br, 4.42% S. IR: 1599, 1576. 1H NMR: 7.39
(2 H, m , 2 × p-); 7.42 (4 H, 4 × o-); 7.43 (4 H, 4 × m-); 7.57 (2 H, d, J = 8.1, H-4, H-5); 7.62
(2 H, dd, J = 8.1, 1.8, H-3, H-6); 7.94 (2 H, d, J = 1.8, H-1, H-8). 13C NMR: 65.75 (C-4′);
110.48 (C-3′, C-5′); 121.30 (C-4, C-5); 122.40 (C-2, C-7); 128.05 (C-1, C-8); 128.61 (4 × o-);
129.02 (4 × m-); 129.13 (2 × p-); 132.12 (C-2′, C-6′); 132.35 (C-3, C-6); 136.95 (C-4a, C-4b);
138.82 (2 × i-); 152.85 (C-8a, C-9a).
2,3′,5′-Tribromo-2′,6′-diphenylspiro[fluorene-9,4′-thiopyran] (11). Fraction 2 afforded 0.502 g
(32%) of com poun d 11, wh ich was recrystallized from eth an ol–cycloh exan e, m .p. 233–235 °C.
For C29H17Br3S (637.2) calculated: 54.66% C, 2.69% H, 37.62% Br, 5.03% S; foun d: 54.08% C,
2.84% H, 37.53% Br, 5.10% S. IR: 1609, 1577. 1H NMR: 7.39 (2 H, m , 2 × p-); 7.42 (4 H, m ,
4 × o-); 7.46 (4 H, m , 4 × m-); 7.52 (1 H, m , H-7); 7.54 (1 H, m , H-6); 7.63 (1 H, d, J = 8.1,
H-4); 7.65 (1 H, dd, J = 8.1, 1.4, H-3); 7.75 (1 H, m , H-8); 7.88 (1 H, m , H-5); 8.00 (1 H, d,
J = 1.4, H-1). 13C NMR: 65.66 (C-4′); 111.43 (C-3′, C-5′); 119.93 (C-8); 121.25 (C-4); 121.90
(C-2); 124.78 (C-4); 128.05 (C-1); 128.55 (4 × o-); 128.70 (C-7); 128.98 (2 × p-); 129.03 (4 ×
m-); 129.09 (C-6); 131.50 (C-2′, C-6′); 132.12 (C-3); 137.19 (2 × i-); 139.66 (C-4b); 139.91
(C-4a); 151.11 (C-8a); 153.04 (C-9a).
3′,5′-Dibromo-2′,6′-diphenylspiro[fluorene-9,4′-thiopyran] (6) Fraction 3 afforded 0.102 g
(7.3%) of com poun d, recrystallized from ben zen e–eth an ol, m .p. 223–225 °C, wh ich was
iden tical with com poun d 6.
3,5-Dibrom o-2,8-bis(4-fluoroph en yl)-3a-ph en yl-3aH-ben zo[3,4]cyclopen ta-
[1,2-b]th ioph en e (9)
Brom in e (3.64 g, 22.8 m m ol) was added at room tem perature un der stirrin g to a solution of
th iopyran 2 (1 g, 2.28 m m ol) in carbon disulfide (2.5 m l) an d th e reaction was allowed to
con tin ue at room tem perature overn igh t. Th e sam e work-up as in th e case of com poun d 7
an d recrystallization of th e crude product from ben zen e–eth an ol yielded yellowish crystals
of 9 (0.908 g, 67%), m .p. 215–217 °C. For C29H16Br2F2S (594.3) calculated: 58.61% C, 2.71% H,
26.89% Br, 5.39% S; foun d: 58.61% C, 3.25% H, 26.40% Br, 5.37% S. IR: 1600, 1585. 1H NMR:
7.12 (2 H, AA′BB′X, ∑J = 8.9, JH,F = 8.6, 2-Ph , m-); 7.20 (2 H, AA′BB′X, ∑J = 8.9, JH,F = 8.6,
8-Ph , m-); 7.35 (2 H, m , 3a-Ph , m-); 7.35 (1 H, m , 3a-Ph , p-); 7.36 (2 H, m , 3a-Ph , o-); 7.43
(1 H, d, J = 8.2, H-7); 7.48 (2 H, AA′BB′X, ∑J = 8.9, JH,F = 5.3, 2-Ph , o-); 7.58 (1 H, dd, J = 8.2,
1.9, H-6); 7.66 (2 H, AA′BB′X, ∑J = 8.9, JH,F = 5.3, 2-Ph , o-); 7.85 (1 H, d, J = 1.9, H-4).
13C NMR: 77.26 (C-3a); 109.22 (C-3); 115.69 d (2-Ph , 2 × m-, JC,F = 30.9); 115.90 d (8-Ph ,
2 × m-, JC,F = 30.9); 120.04 (C-5); 121.50 (C-7); 126.39 (3a-Ph , 2 × m-); 127.94 (3a-Ph , p-);
128.50 d (8-Ph , i-, JC,F = 3.0); 128.87 (C-4); 128.94 (3a-Ph , 2 × o-); 129.21 d (2-Ph , i-, JC,F
=
3.0), 129.93 d (3a-Ph , 2 × o-, JC,F = 8.1); 130.45 d (2-Ph , 2 × o-, JC,F = 8.4); 131.24 (C-6);
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1642
Kroulík et. al.:
138.33 (3a-Ph , i-); 140.52 (C-8); 143.27 (C-7a); 143.47 (C-2); 146.70 (C-8a); 150.38 (C-3b);
162.93 d (8-Ph , p-, JC,F = 249.5); 162.98 d (2-Ph , p-, JC,F = 250.8).
REFERENCES
1. a) Mori Y., Maeda K.: J. Chem. Soc., Perkin Trans. 2 1991, 2061; b) Pirelahi H.,
Parchamazad I., Abaii M. S., Sheikhebrahimi S.: Phosphorus, Sulfur Silicon Relat. Elem.
1991, 59, 251; c) Šebek P., Nešpůrek S., Hrabal R., Adamec M., Kuthan J.: J. Chem. Soc.,
Perkin Trans. 2 1992, 1301; d) Vojtěchovský J., Hašek J., Nešpůrek S., Adamec M.: Collect.
Czech. Chem. Commun. 1992, 57, 1326; e) Pirelahi H., Hashtroodi M. S., Abaii M. S.,
Shariati Y. R.: J. Photochem. Photobiol. A: Chem. 1994, 81, 21; f) Pirelahi H., Rahmani H.,
Mouradzadegun A., Fathi A., Moudjoodi A.: J. Photochem. Photobiol. A: Chem. 1996, 101,
33; g) Böhm S., Šebek P., Nešpůrek S., Kuthan J.: Collect. Czech. Chem. Commun. 1994,
59, 1115.
2. a) Kuthan J., Šebek P., Böhm S.: Adv. Heterocycl. Chem. 1994, 59, 179; b) Kuthan J.: Adv.
Heterocycl. Chem. 1983, 34, 145.
3. a) Schwarz M., Šebek P., Kuthan J.: Collect. Czech. Chem. Commun. 1992, 57, 546;
b) Kroulík J., Chadim M., Polášek M., Nešpůrek S., Kuthan J.: Collect. Czech. Chem.
Commun. 1998, 63, 662.
4. a) Šebek P., Sedmera P., Hušák M., Novotný J., Kuthan J.: Mendeleev Commun. 1992, 102;
b) Šebek P., Kroulík J., Sedmera P., Havlíček V., Kuthan J.: Collect. Czech. Chem. Commun.
1994, 59, 2269.
5. To our best knowledge, the existence of this compound is not verified. For recent
interesting Raman spectral study on this topic, see: a) Milne J.: Spectrochim. Acta, Part A
1992, 48, 533. Corresponding tribromide salts are well known, see e.g.: b) Kessat A.,
Babadjamian A., Iraqi A.: Eur. Polym. J. 2000, 37, 131; c) Shchori E., Jagur-Grodzinski J.:
J. Am. Chem. Soc. 1972, 94, 7957; d) Boeyens J. C. A., Denner L., Howard A. S., Michael
J. P.: S. Afr. J. Chem. 1986, 39, 217.
6. Farrugia L. J.: J. Appl. Crystallogr. 1997, 30, 565.
7. North A. C. T., Phillips D. C., Mathews F. S.: Acta Crystallogr., Sect. A: Cryst. Phys., Diffr.,
Theor. Gen. Crystallogr. 1968, 24, 351.
8. Altomare A., Cascarano G., Giacovazzo G., Guagliardi A., Burla M. C., Polidori G.,
Camalli M.: J. Appl. Crystallogr. 1994, 27, 435.
9. Watkin D. J., Prout C. K., Carruthers J. R., Betteridge P. W.: CRYSTALS, Issue 10.
Chemical Crystallography Laboratory, Oxford 1996.
10. Carruthers J. R., Watkin D. J.: Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen.
Crystallogr. 1979, 35, 698.
Collect. Czech. Chem. Commun. (Vol. 69) (2004)