Synthesis of 5-(arylselanyl)-2-(arylsulfanyl)benzoates by [3+3] cyclocondensation of 3-(arylsulfanyl)-1-(silyloxy)buta-1,3-dienes with 2-(arylselanyl)-3-(silyloxy)alk-2-en-1-ones

Article abstract of DOI:10.1002/hlca.201000110

Functionalized 5-(arylselanyl)-2-(arylsulfanyl)benzoates were prepared by [3+3] cyclocondensation of 3-(arylsulfanyl)-1-(silyloxy)buta-1,3-dienes with 2-(arylselanyl)-3-(silyloxy)-alk-2-en-1-ones.

Full text of DOI:10.1002/hlca.201000110

Helvetica Chimica Acta – Vol. 93 (2010)
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Synthesis of 5-(Arylselanyl)-2-(arylsulfanyl)benzoates by [3 þ 3]
Cyclocondensation of 3-(Arylsulfanyl)-1-(silyloxy)buta-1,3-dienes with
2-(Arylselanyl)-3-(silyloxy)alk-2-en-1-ones
by Inam Iqbala), Muhammad Imrana), and Peter Langer*a)b)
a) Institut fꢀr Chemie, Universitꢁt Rostock, Albert-Einstein-Strasse 3a, D-18059 Rostock
(fax: þ 49-381-4986412; e-mail: peter.langer@uni-rostock.de)
b) Leibniz-Institut fꢀr Katalyse e.V. an der Universitꢁt Rostock, Albert-Einstein-Strasse 29a,
D-18059 Rostock
Functionalized 5-(arylselanyl)-2-(arylsulfanyl)benzoates were prepared by [3 þ 3] cyclocondensa-
tion of 3-(arylsulfanyl)-1-(silyloxy)buta-1,3-dienes with 2-(arylselanyl)-3-(silyloxy)-alk-2-en-1-ones.
Introduction. – Diaryl selenides possess interesting biological properties such as
antimicrobial, antitumor, and antioxidant activities. In addition, they have been used in
the field of material sciences (e.g., as conductive and supraconductive organic
molecules) [1]. Due to the unstable nature of organoselenium compounds, their
synthesis is considerably more difficult than the synthesis of the corresponding S
analogs. In fact, most of the methods developed for the synthesis of organosulfur
compounds cannot be easily adapted to the synthesis of organoselenium derivatives.
Aliphatic organoselenium compounds have been prepared by reaction of selenolates
with various electrophiles (e.g., organic halides, acyl chlorides, epoxides, and enones)
[2]. Diaryl selenides are, in general, more difficult to prepare than aliphatic selenides,
because nucleophilic substitution reactions cannot be applied. Unsymmetrical diaryl
selenides are more difficult to prepare than symmetrical ones. Diaryl selenides have
been prepared by reaction of selenolates with aryl halides [3] and by reaction of
organometallic reagents (e.g., organolithium compounds, Grignard reagents, or
cuprates) with diaryl diselenides or arylselenyl bromides [4]. Despite their great
utility, there are several drawbacks such as low regioselectivity, harsh reaction
conditions (high temperature), reduction, and formation of diselenides. An additional
problem lies in the synthesis of the required starting materials, as highly functionalized
or sterically encumbered halogenated arenes are not readily available, and their
synthesis can be a very difficult and tedious task. As a result, highly substituted or
functionalized diaryl selenides are not readily available by the methods known to date
for the formation of CꢀSe bonds.
To address these problems associated with the synthesis of diaryl selenides, we have
envisaged the application of a building-block strategy which relies on the use of
appropriate Se-containing molecules in cyclization reactions. Applications of this
approach to the synthesis of carbacyclic molecules have only scarcely been reported so
far. Six-membered rings were prepared by [4 þ 2] cycloaddition of 2-(phenylselanyl)-
ꢂ 2010 Verlag Helvetica Chimica Acta AG, Zꢀrich

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Helvetica Chimica Acta – Vol. 93 (2010)
buta-1,3-dienes with alkenes and alkynes [5]. Recently, we have reported [6] the
synthesis of 5-(phenylselanyl)salicylates by formal [3 þ 3] cyclizations [7] of 1,3-
bis(silyloxy)buta-1,3-dienes [8] with 2-(arylselanyl)-3-(silyloxy)alk-2-en-1-ones. Here,
we report, for the first time, the cyclization of 2-(arylselanyl)-3-(silyloxy)-2-en-1-ones
with 3-(arylsulfanyl)-1-(silyloxy)buta-1,3-dienes. These transformations allow a con-
venient synthesis of novel 5-(arylselenyl)-2-(arylsulfanyl)benzoates which can be
regarded as mixed diaryl sulfides and diaryl selenides. The synthesis of this type of
highly substituted and functionalized products has not been previously reported. It can
be anticipated that the products are not readily available by other methods.
Results and Discussion. – The reaction of acetylacetone (1) with SeO2 and diphenyl
diselenide, in the presence of catalytic amounts of H2SO4, afforded the 2-(phenyl-
selanyl)-1,3-dione 2 (Scheme 1) [9]. The silylation of 2 with Me3SiCl afforded the novel
3-(silyloxy)-2-en-1-one 3. The known 3-(arylsulfanyl)-1-(trimethylsilyloxy)buta-1,3-
dienes 4a – 4k were prepared from methyl acetoacetate, methyl 3-oxopentanoate, and
various thiophenols in two steps [10].
Scheme 1. Synthesis of 3
The TiCl4-mediated cyclization of 3 with dienes 4a – 4k afforded the novel 2-
(arylsulfanyl)-5-(phenylselanyl)benzoates 5a – 5k in 43 – 67% yield (Scheme 2 and
Table). Products 5a – 5k contain a diaryl sulfide and a diaryl selenide moiety. The yields
of products 5d and 5j, derived from dienes containing no terminal substituent, were
higher than the yields of products 5f and 5k, respectively. The yields of the products
derived from dienes 4b and 4c, containing an electron-withdrawing Cl-atom attached to
Table. Synthesis of 5a – 5k
4 and 5
R
Ar
Yield of 5 [%]a)
a
b
c
d
e
f
g
h
i
H
Me
H
H
H
Me
H
H
H
H
Ph
67
43
51
61
60
47
63
64
45
59
47
4-ClꢀC6H4
3-ClꢀC6H4
4-MeꢀC6H4
3-MeꢀC6H4
4-MeꢀC6H4
3-MeOꢀC6H4
4-MeOꢀC6H4
Naphthalen-2-yl
4-EtꢀC6H4
4-EtꢀC6H4
j
k
Me
a) Yields of isolated products.

Helvetica Chimica Acta – Vol. 93 (2010)
1781
the aryl group, were lower than the yields of those products which are derived from
dienes containing more electron-rich aryl groups. This can be explained by the
decreased nucleophilicity of dienes 4b and 4c. The yield of product 5i is relatively low,
which might be explained by steric hindrance of the naphthyl group.
Scheme 2. Synthesis of 5a – 5k
In conclusion, we have reported the first synthesis of 5-(arylselanyl)-2-(arylsulfa-
nyl)benzoates, mixed diaryl sulfides and selenides, by [3 þ 3] cyclocondensation of 3-
(arylsulfanyl)-1-(silyloxy)buta-1,3-dienes with 2-(arylselanyl)-3-(silyloxy)alk-2-en-1-
ones.
Experimental Part
General. All solvents were dried by standard methods, and all reactions were carried out under an
inert atmosphere. M.p.: Microheating table HMK 67/1825 Kuestner (Bꢀchi apparatus); uncorrected.
Column chromatography (CC): silica gel 60 (SiO2; 0.063 – 0.200 mm, 70 – 230 mesh). IR Spectra: Nicolet
.
380 FT-IR spectrometer; ˜n in cmꢀ1 1H- and 13C-NMR spectra: Bruker AVANCE 300 II and Bruker
AVANCE 250 II spectrometer in CDCl3; d in ppm rel. to Me4Si as internal standard, J in Hz. EI-MS and
HR-EI-MS: Finnigan MAT 95-XP mass spectrometer at 70 eV; in m/z.
4-(Phenylselanyl)heptane-3,5-dione. To a CH2Cl2 suspension (35 ml) of SeO2 (1.11 g, 10.0 mmol),
diphenyl diselenide (6.24 g, 20.0 mmol) and a cat. amount of conc. H2SO4 (0.1 ml, 2.0 mmol) was added
heptane-3,5-dione (2.3 ml, 17.0 mmol), at 108. The mixture was stirred for 14 h at 208. The mixture was
poured into CH2Cl2 (100 ml), and the aq. and the org. layer were separated. The latter was washed with a
sat. aq. soln. of NaHCO3 (20 ml), dried (Na2SO4), and filtered, and the filtrate was concentrated in
vacuo. The residue was purified by CC (SiO2; AcOEt, heptanes) to give the title compound (1.33 g,
47%). Yellowish oil. IR (neat): 3069w, 2976w, 2937w, 2877w, 1695m, 1575m, 1557m, 1475m, 1458m,
1436m, 1401m, 1375m, 1337m, 1296m, 1240m, 1187m, 1156m, 1099m, 1064m, 1019m, 997m, 886w, 847m,
805m, 731s, 688s, 666m, 614w. 1H-NMR (300 MHz): 1.02 (t, 3J ¼ 7.4, 2 Me); 2.71 (q, 3J ¼ 7.6, 2 CH2); 3.61
(s, CH); 7.07 – 7.12 (m, 2 arom. H); 7.13 – 7.20 (m, 3 arom. H). 13C-NMR (75 MHz): 13.7, 13.9 (Me); 31.2,
31.3 (CH2); 61.4 (CH); 125.0 (arom. CH); 126.6, 128.3 (2 arom. CH); 130.5 (arom. C); 197.0, 200.0
(C¼O). GC/MS: 284 (43, Mþ), 282 (10), 280 (22), 255 (14), 254 (11), 253 (13), 230 (23), 228 (21), 226
(14), 225 (13), 224 (14), 172 (11). HR-EI-MS: 284.03100 (Mþ, C13H16O2Seþ; calc. 284.03155).
General Procedure for the Synthesis of the Benzoates 5a – 5k. To a CH2Cl2 soln. (6 ml/mmol of 3) of
4a – 4k (1.5 mmol) and of 3 (1.5 mmol) was added TiCl4 (2.25 mmol) at ꢀ 788. The soln. was allowed to
warm to 208 within 20 h. To the soln. was added NH4Cl (20 ml). The org. and the aq. layer were separated,
and the latter was extracted with CH2Cl2 (3 ꢁ 20 ml). The combined org. layers were dried (MgSO4),
filtered, and the filtrate was concentrated in vacuo, and the residue was purified by CC (SiO2; AcOEt/
heptane 1:9): 5a – 5k, all as highly viscous oils.

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Helvetica Chimica Acta – Vol. 93 (2010)
Methyl 2,4-Dimethyl-3-(phenylselanyl)-6-(phenylsulfanyl)benzoate (5a). Yield: 429 mg (67%). IR
(KBr): 3056w, 2992w, 2949w, 2922w, 2850w, 2664w, 1083m, 1738m, 1710s, 1650m, 1571m, 1473m, 1438s,
1303m, 1247m, 1195s, 1153s, 1099s, 1067m, 1022s, 1000m, 886m, 844m, 803m, 745s, 703s, 688s, 608m.
1H-NMR (250 MHz): 2.32 (s, Me); 2.34 (s, Me); 3.54 (s, MeO); 7.13 – 7.30 (m, 11 arom. H). 13C-NMR
(63 MHz): 18.9 (Me); 25.1 (Me); 49.8 (MeO); 110.2, 125.0 (arom. CH); 126.3 (arom. C); 127.5 (arom.
CH); 127.9 (arom. C); 128.3, 128.6, 128.9, 129.0, 129.7 (arom. CH); 130.2, 130.4, 131.2 (arom. C); 132.4,
133.4, 134.0 (arom. CH); 157.9, 164.5 (arom. C); 196.7 (C). EI-MS: 428 (18), 427 (100, [M ꢀ H]þ), 411
(12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10), 184 (17). HR-EI-MS:
427.09715 ([M ꢀ H]þ, C22H19O2SSeþ; calc. 427.02710).
Methyl 2-[(4-Chlorophenyl)sulfanyl]-3,4,6-trimethyl-5-(phenylselanyl)benzoate (5b). Yield: 306 mg
(43%). IR (KBr): 3055w, 2991w, 2948w, 2923w, 2850w, 2664w, 1082m, 1738m, 1710s, 1650m, 1572m,
1473m, 1437s, 1303m, 1247m, 1195s, 1153s, 1098s, 1067m, 1022s, 1000m, 886m, 844m, 803m, 745s, 703s,
688s, 608m. 1H-NMR (250 MHz): 2.12 (s, Me); 2.23 (s, Me); 2.34 (s, Me); 3.75 (s, MeO); 7.13 – 7.50 (m, 9
arom. H). 13C-NMR (63 MHz): 18.9 (Me); 20.1 (Me); 25.1 (Me); 51.0 (MeO); 110.2, 123.8, 124.1, 124.3
(arom. CH); 126.3 (arom. C); 127.4 (2 arom. CH); 127.9, 128.0, 128.2 (arom. CH); 128.5, 130.1, 130.5,
130.9, 131.0, 132.3, 138.6, 144.3 (arom. C); 167.1 (C). EI-MS: 477 (39), 475 (100, [M ꢀ H]þ), 411 (12), 271
(61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10), 184 (17). HR-EI-MS: 475.03207
([M ꢀ H]þ, C23H20ClO2SSeþ; calc. 475.00378).
Methyl 6-[(3-Chlorophenyl)sulfanyl]-2,4-dimethyl-3-(phenylselanyl)benzoate (5c). Yield: 253 mg
(51%). IR (KBr): 3056w, 2992w, 2948w, 2921w, 2850w, 2666w, 1083m, 1739m, 1710s, 1571m, 1473m,
1438s, 1303m, 1248m, 1195s, 1153s, 1099s, 1067m, 1022s, 1000m, 887m, 845m, 803m, 746s, 703s, 689s, 608m.
1H-NMR (250 MHz): 2.32 (s, Me); 2.34 (s, Me); 3.56 (s, MeO); 7.10 – 7.80 (m, 10 arom. H). 13C-NMR
(63 MHz): 20.1 (Me); 21.1 (Me); 51.1 (MeO); 110.2 (arom. CH); 126.3 (arom. C); 127.5 (arom. CH);
127.9 (arom. C); 128.3, 128.6, 128.9, 129.0, 129.7 (arom. CH); 130.2, 130.4, 131.2 (arom. C); 132.4, 133.4,
134.0 (arom. CH); 157.9, 160.2, 164.5 (arom. C); 170.7 (C). EI-MS: 463 (38), 461 (100, [M ꢀ H]þ), 411
(12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10), 184 (17). HR-EI-MS:
461.03207 ([M ꢀ H]þ, C22H18ClO2SSeþ; calc. 460.98813).
Methyl 2,4-Dimethyl-6-[(4-methylphenyl)sulfanyl]-3-(phenylselanyl)benzoate (5d). Yield: 403 mg
(61%). IR (KBr): 3056w, 2992w, 2948w, 2921w, 2850w, 2665w, 1083m, 1738m, 1710s, 1571m, 1473m, 1438s,
1303m, 1248m, 1195s, 1153s, 1099s, 1067m, 1022s, 1000m, 886m, 844m, 803m, 745s, 703s, 688s, 608m.
1H-NMR (250 MHz): 2.0 (s, Me); 2.32 (s, Me); 2.34 (s, Me); 3.49 (s, MeO); 7.10 – 7.42 (m, 10 arom. H).
13C-NMR (63 MHz): 18.9 (Me); 20.1 (Me); 21.1 (Me); 51.1 (MeO); 110.2 (arom. CH); 126.3 (arom. C);
127.5 (arom. CH); 127.9 (arom. C); 128.3, 128.6, 128.8, 129.0, 129.4 (arom. CH); 130.2, 130.4, 131.1 (arom.
C); 132.6, 133.5, 134.0 (arom. CH); 157.9, 160.2, 164.5 (arom. C); 170.7 (C). EI-MS: 442 (18), 441 (100,
[M ꢀ H]þ), 414 (12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10), 184
(17). HR-EI-MS: 441.09715 ([M ꢀ H]þ, C23H21O2SSeþ; calc. 441.04275).
Methyl 2,4-Dimethyl-6-[(3-methylphenyl)sulfanyl]-3-(phenylselanyl)benzoate (5e). Yield: 403 mg
(61%). IR (KBr): 3055w, 2992w, 2948w, 2931w, 2850w, 2665w, 1083m, 1738m, 1710s, 1571m, 1473m, 1438s,
1
1303m, 1195s, 1154s, 1099s, 1067m, 1021s, 1000m, 885m, 843m, 803m, 745s, 704s, 688s, 608m. H-NMR
(250 MHz): 2.10 (s, Me); 2.31 (s, Me); 2.33 (s, Me); 3.49 (s, MeO); 7.10 – 7.40 (m, 10 arom. H). 13C-NMR
(63 MHz): 18.8 (Me); 20.1 (Me); 21.1 (Me); 51.1 (MeO); 110.2 (arom. CH); 126.3 (arom. C); 127.5
(arom. CH); 127.9 (arom. C); 128.3, 128.6, 128.8, 129.0, 129.4 (arom. CH); 130.2, 130.4, 131.1 (arom. C);
132.6, 133.5, 134.0 (arom. CH); 157.9, 160.2, 164.5 (arom. C); 170.7 (C). EI-MS: 442 (18), 441 (100, [M ꢀ
H]þ), 414 (12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10), 184 (17).
HR-EI-MS: 441.09716 ([M ꢀ H]þ, C23H21O2SSeþ; calc. 441.04275).
Methyl 2,4,5-Trimethyl-6-[(4-methylphenyl)sulfanyl]-3-(phenylselanyl)benzoate (5f). Yield: 331 mg
(47%). IR (KBr): 3056w, 2992w, 2949w, 2931w, 2850w, 2666w, 1083m, 1738m, 1710s, 1571m, 1473m, 1438s,
1
1303m, 1196s, 1153s, 1099s, 1067m, 1023s, 1000m, 885m, 844m, 804m, 745s, 703s, 687s, 608m. H-NMR
(250 MHz): 2.12 (s, Me); 2.23 (s, Me); 2.31 (s, Me); 2.33 (s, Me); 3.50 (s, MeO); 7.10 – 7.48 (m, 9 arom. H).
13C-NMR (63 MHz): 18.8 (Me); 20.0 (Me); 20.1 (Me); 21.1 (Me); 51.1 (MeO); 110.2 (arom. CH); 126.3,
126.9 (arom. C); 127.5 (arom. CH); 127.9 (arom. C); 128.3, 128.8, 129.0, 129.4 (arom. CH); 130.2, 130.4,
131.1 (arom. C); 132.6, 133.5, 134.0 (arom. CH); 157.9, 160.2, 164.5 (arom. C); 170.7 (C). EI-MS: 456

Helvetica Chimica Acta – Vol. 93 (2010)
1783
(18), 455 (100, [M ꢀ H]þ), 410 (12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13),
185 (10), 184 (17). HR-EI-MS: 455.09716 ([M ꢀ H]þ, C24H23O2SSeþ; calc. 455.05840).
Methyl 6-[(3-Methoxyphenyl)sulfanyl]-2,4-dimethyl-3-(phenylselanyl)benzoate (5g). Yield: 432 mg
(63%). IR (KBr): 3056w, 2992w, 2948w, 2931w, 2850w, 2665w, 1083m, 1737m, 1710s, 1571m, 1472m, 1438s,
1
1303m, 1194s, 1153s, 1099s, 1068m, 1022s, 1000m, 885m, 844m, 804m, 745s, 703s, 688s, 608m. H-NMR
(250 MHz): 2.13 (s, Me); 2.31 (s, Me); 3.49 (s, MeO); 3.51 (s, MeO); 7.24 – 7.55 (m, 10 arom. H).
13C-NMR (63 MHz): 20.8 (Me); 21.1 (Me); 50.4 (MeO); 51.1 (MeO); 110.2 (arom. CH); 126.3 (arom.
C); 127.5 (arom. CH); 127.9 (arom. C); 128.3, 128.6, 128.8, 129.0, 129.4 (arom. CH); 130.2, 130.4, 131.1
(arom. C); 132.6, 133.5, 134.0 (arom. CH); 157.9, 160.2, 164.5 (arom. C); 170.7 (C). EI-MS: 458 (11), 457
(100, [M ꢀ H]þ), 414 (12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10),
184 (17). HR-EI-MS: 457.09716 ([M ꢀ H]þ, C23H21O3SSeþ; calc. 457.03766).
Methyl 6-[(4-Methoxyphenyl)sulfanyl]-2,4-dimethyl-3-(phenylselanyl)benzoate (5h). Yield: 439 mg
(64%). IR (KBr): 3056w, 2992w, 2948w, 2931w, 2851w, 2665w, 1083m, 1739m, 1710s, 1571m, 1473m, 1438s,
1
1303m, 1195s, 1153s, 1099s, 1068m, 1022s, 1000m, 885m, 845m, 803m, 745s, 703s, 688s, 608m. H-NMR
(250 MHz): 2.13 (s, Me); 2.32 (s, Me); 3.50 (s, MeO); 3.52 (s, MeO); 7.24 – 7.55 (m, 10 arom. H).
13C-NMR (63 MHz): 20.8 (Me); 21.1 (Me); 50.4 (MeO); 51.1 (MeO); 110.2 (arom. CH); 126.3 (arom.
C); 127.5 (arom. CH); 127.9 (arom. C); 128.4, 128.6, 128.8, 129.0, 129.4 (arom. CH); 130.2, 130.4, 131.1
(arom. C); 132.6, 133.5, 134.0 (arom. CH); 157.9, 160.2, 164.5 (arom. C); 170.7 (C). EI-MS: 458 (11), 457
(100, [M ꢀ H]þ), 414 (12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10),
184 (17). HR-EI-MS: 457.09716 ([M ꢀ H]þ, C23H21O3SSeþ; calc. 457.03766).
Methyl 2,4-Dimethyl-6-[(naphthalen-2-yl)sulfanyl]-3-(phenylselanyl)benzoate (5i). Yield: 322 mg
(45%). IR (KBr): 3056w, 2992w, 2948w, 2931w, 2851w, 2665w, 1083m, 1738m, 1712s, 1571m, 1473m, 1437s,
1303m, 1270m, 1195s, 1153s, 1099s, 1067m, 1021s, 1000m, 885m, 846m, 803m, 745s, 704s, 688s, 608m.
1H-NMR (250 MHz): 2.25 (s, Me); 2.43 (s, Me); 3.80 (s, MeO); 6.98 – 7.84 (m, 13 arom. H). 13C-NMR
(63 MHz): 20.8 (Me); 23.7 (Me); 51.3 (MeO); 124.9, 125.4, 125.6, 126.5, 126.7 (arom. CH); 126.9 (arom.
C); 127.9 (2 arom. CH); 128.0, 128.1 (arom. CH); 128.3 (2 arom. CH); 129.7 (arom. C); 129.8, 130.0
(arom. CH); 130.7, 131.2, 131.5, 132.6, 133.6, 139.9, 144.8 (arom. C); 167.9 (C). EI-MS: 478 (11), 477 (100,
[M ꢀ H]þ), 414 (12), 271 (61), 270 (21), 269 (86), 256 (18), 255 (49), 228 (17), 227 (13), 185 (10), 184
(16). HR-EI-MS: 477.09715 ([M ꢀ H]þ, C26H21O2SSeþ; calc. 477.04275).
Methyl 6-[(4-Ethylphenyl)sulfanyl]-2,4-dimethyl-3-(phenylselanyl)benzoate (5j). Yield: 403 mg
(59%). IR (neat): 3016w, 2963w, 2948w, 2928w, 2871w, 1729s, 1596m, 1491m, 1433m, 1404w, 1383w,
1285s, 1242m, 1223m, 1187m, 1142s, 1119m, 1087m, 1052m, 1014m, 1004m, 821s, 789m, 751w, 721m.
1H-NMR (250 MHz): 1.09 (t, J ¼ 7.2, Me); 2.16 (s, Me); 2.18 (s, Me); 2.47 (q, J ¼ 7.2, CH2); 3.74 (s, MeO);
6.93 – 7.17 (m, 10 arom. H). 13C-NMR (75 MHz): 15.4 (Me); 16.9 (Me); 28.3 (CH2); 52.0 (MeO); 127.6 (2
arom. CH); 128.4 (2 arom. CH); 128.5, 131.9 (arom. C); 132.8, 133.0, 133.4, 133.7, 134.0, 134.9 (arom.
CH); 134.1, 138.7, 139.0, 139.2, 139.8, 141.6 (arom. C); 169.7 (C). GC/EI-MS: 456 (18), 455 (100, [M ꢀ
H]þ), 284 (5), 283 (26), 182 (10), 281 (27), 267 (7), 254 (20), 253 (97), 239 (7), 225 (15), 178 (5), 134 (4),
121 (19). HR-EI-MS: 455.13346 ([M ꢀ H]þ, C24H23O2SSeþ; calc. 455.05840).
Methyl 2-[(4-Ethylphenyl)sulfanyl]-3,4,6-trimethyl-5-(phenylselanyl)benzoate (5k). Yield: 331 mg
(47%). IR (neat): 3016w, 2963w, 2948w, 2928w, 2871w, 1729s, 1596m, 1491m, 1433m, 1404w, 1383w, 1285s,
1
1242m, 1223m, 1187m, 1142s, 1118m, 1087m, 1052m, 1014m, 1004m, 821s, 789m, 751w, 721m. H-NMR
(250 MHz): 1.09 (t, J ¼ 7.2, Me); 2.16 (s, Me); 2.18 (s, Me); 2.19 (s, Me); 2.48 (q, J ¼ 7.2, CH2); 3.76 (s,
MeO); 6.93 – 7.42 (m, 9 arom. H). 13C-NMR (75 MHz): 15.4 (Me); 16.9 (Me); 18.1 (Me); 28.3 (CH2);
52.0 (MeO); 127.6 (2 arom. CH); 128.4 (2 arom. CH); 128.5, 131.9 (arom. C); 132.8, 133.0, 133.4, 134.0,
134.9 (arom. CH); 134.1, 138.7, 139.0, 139.2, 139.8, 141.6, 141.9 (arom. C); 169.7 (C). GC/EI-MS: 470
(18), 469 (100, [M ꢀ H]þ), 284 (5), 283 (26), 182 (10), 281 (27), 267 (7), 254 (20), 253 (97), 239 (7), 225
(15), 178 (5), 134 (4), 121 (19). HR-EI-MS: 469.13346 ([M ꢀ H]þ, C25H25O2SSeþ; calc. 469.07405).
Financial support by the State of Pakistan (H.E.C. scholarship for I. I.) and by the State of
Mecklenburg-Vorpommern (scholarship for M. I.) is gratefully acknowledged.

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Helvetica Chimica Acta – Vol. 93 (2010)
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Received March 18, 2010