Synthesis and reactions of enantiomerically pure dialkyl diselenides from the p-menthane group

Article abstract of DOI:10.1016/j.tetasy.2008.04.027

A convenient route for the synthesis of optically active dialkyl diselenides from the p-menthane system utilizing a reaction of alkyl tosylates and chlorides with sodium diselenide is reported. The diselenides obtained have been used for asymmetric methoxyselenenylation of styrene. Quantum chemical calculations of the chair conformers stability of the terpeneselenenyl bromides from the p-menthane group have also been carried out using density functional theory (DFT, at the B3LYP/6-311G(d) level). The influence of the diselenides structure on the stereoselectivity in the methoxyselenenylation reaction is also discussed.

Full text of DOI:10.1016/j.tetasy.2008.04.027

Tetrahedron: Asymmetry 19 (2008) 1237–1244
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Tetrahedron: Asymmetry
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Synthesis and reactions of enantiomerically pure dialkyl diselenides from the
p-menthane group
*
´
´
Zbigniew Rafinski, Jacek Scianowski
Department of Chemistry, Nicolaus Copernicus University, 7 Gagarin Street, 87-100 Torun, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
A convenient route for the synthesis of optically active dialkyl diselenides from the p-menthane system
utilizing a reaction of alkyl tosylates and chlorides with sodium diselenide is reported. The diselenides
obtained have been used for asymmetric methoxyselenenylation of styrene. Quantum chemical calcula-
tions of the chair conformers stability of the terpeneselenenyl bromides from the p-menthane group have
also been carried out using density functional theory (DFT, at the B3LYP/6-311G(d) level). The influence
of the diselenides structure on the stereoselectivity in the methoxyselenenylation reaction is also
discussed.
Received 1 April 2008
Accepted 24 April 2008
Available online 26 May 2008
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
Herein, we report the results of our investigations concerning
the synthesis of the dialkyl diselenides from the p-menthane group
In recent years, organoselenium compounds have played an
important role in organic synthesis. The discovery of the selenox-
ide elimination in early 1970s was a major breakthrough for the
development of organoselenium chemistry.1–3 Oxidation of sele-
nides to the corresponding selenoxides or selenones and subse-
quent elimination or substitution, reductive deselenenylation,
transformations into carboanions, and participation in radical cou-
pling processes make the organoselenium derivatives versatile
building blocks.4–7 In 1958 it was discovered that electrophilic
selenium compounds can add stereospecifically to alkenes.8 In this
context chiral organic selenium compounds, particulary optically
active diselenides, are frequently used as convenient reagents for
introducing various asymmetric functional groups to carbon–car-
bon double bonds and for constructing heterocyclic compounds
via ring-closure processes.9–13 Organoselenium compounds fre-
quently posseses unique biological activities.14–16
In previous papers, we have described a convenient method for
the synthesis of optically active terpene alkyl diselenides. As a re-
sult of the reaction between sodium diselenide with the respective
tosylates or chlorides, we obtained dialkyl diselenides derived
from (ꢀ)-menthol, (ꢀ)-trans-4-caranol, (ꢀ)-isopinocampheol, (ꢀ)-
myrtanol, and (ꢀ)-borneol.17,18 The resulting diselenides has been
employed in the asymmetric selenenylation of olefins,18 and sele-
nocyclization of the unsaturated alcohols and carboxylic acids.19
The investigation concerning the helicity of the diselenide chromo-
fore via the use of the above diselenides have also been
described.20
as well as the results of the asymmetric methoxyselenenylation of
styrene with their use. Our attention was focused on determining
the influence of the structure of the obtained diselenides on their
stereoselectivity in the addition reactions to a carbon–carbon
bond.
Herein, we report a synthesis of two diselenides from the
p-menthane group, namely (+)-dineomenthyl diselenide 3 and
(ꢀ)-dimenthyl diselenide 5, which we obtained as a result of the
reaction of menthyl tosylate 2 and neomenthyl chloride 4 with
sodium diselenide (Scheme 1).18 The tosylate 2 and chloride 4
were obtained from the commercially available (ꢀ)-menthol 1.
We decided to use this methodology for the synthesis of the
epimeric diselenides derived from (+)-isomenthol 6, (+)-carvomen-
thol 13, and (ꢀ)-neoisocarvomenthol 14.
2. Result and discussion
We started our investigations with the synthesis of diselenides
derived from (+)-isomenthol 6. We obtained (+)-isomenthyl tosyl-
ate 7 from the commercially available (+)-isomenthol 6 via reac-
tion with tosyl chloride in pyridine. The subsequent reaction
with carbon tetrachloride and triphenylphosphine led to (+)-neo-
isomenthyl chloride 9. Under the influence of sodium diselenide
generated in situ (Se, NaOH, N2H4 ꢁ H2O)18 on tosylate 7 and chlo-
ride 9, we received (ꢀ)-dineoisomenthyl diselenide 8 and (ꢀ)-
diisomenthyl diselenide 10, respectively. The reaction with sodium
diselenide was carried out at 100 °C in DMF for 1 h for the tosylate
and 2 h for the chloride (Scheme 2).
Further investigations regarding the synthesis of diselenides de-
rived from (+)-carvomenthol 13 and (ꢀ)-neoisocarvomenthol 14
* Corresponding author. Tel.: +48 56 611 4532; fax: +48 56 654 2477.
E-mail address: jsch@chem.uni.torun.pl (J. Scianowski).
´
0957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.04.027

´
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Z. Rafinski, J. Scianowski / Tetrahedron: Asymmetry 19 (2008) 1237–1244
1238
Na2Se2
p-TsCl, pyridine
DMF, 1 h, 100 ºC
24 h, 0 ºC
OTs
Se)2
OH
2
75%
3
90%
1
CCl4, PPh3
24 h, reflux
Na2Se2
DMF, 2 h, 100 ºC
Cl
Se)2
4
44%
5
34%
Scheme 1. Synthesis of (+)-dineomenthyl diselenide 3 and (ꢀ)-dimenthyl diselenide 5.
Na2Se2
p-TsCl, pyridine
DMF, 1 h, 100 ºC
24 h, 0 ºC
OTs
Se)2
OH
7
8
6
85%
72%
CCl4, PPh3
24 h, reflux
Na2Se2
DMF, 2 h, 100 ºC
Cl
Se)2
9
41%
10
40%
Scheme 2. Synthesis of (ꢀ)-dineoisomenthyl diselenide 8 and (+)-diisomenthyl diselenide 10.
were carried out. We obtained a mixture of alcohols 13 and 14 in a
40:60 ratio from (+)-carvone 11 after reduction with LiAlH4 to give
(+)-cis-carveol 12, and then hydrogenation on the platinum cata-
lyst. The enantiomerically pure (+)-carvomenthol 13 and (ꢀ)-neo-
isocarvomenthol 14 were separated by means of the fractional
distillation using FisherÒ Spaltrohr concentric tube column (90
theoretical plates) and then used for the synthesis of carvomenthyl
15 and neoisocarvomenthyl 19 tosylates as well as neocarvomen-
thyl 16 and isocarvomenthyl 20 chlorides. The obtained tosylates
15 and 19 and chlorides 16 and 20 in the reaction with sodium
diselenide gave (ꢀ)-dineocarvomenthyl diselenide 17, (+)-dicarvo-
menthyl diselenide 18, (ꢀ)-diisocarvomenthyl diselenide 21 and
(+)-dineoisocarvomenthyl diselenide 22 (Scheme 3).
The enantiomerically pure diselenides were used for the asym-
metric methoxyselenenylation of styrene (Scheme 4), to give the
following bromides: neomenthylselenenyl 3a, menthylselenenyl
5a, neoisomenthylselenenyl 8a, isomenthylselenenyl 10a, neocar-
vomenthylselenenyl 17a, carvomenthylselenenyl 18a, isocarvom-
enthylselenenyl 21a, and neoisocarvomenthylselenenyl 22a, after
the addition of bromine to diselenides 3, 5, 8, 10, 17, 18, 21, and
22. The reaction was then treated with silver triflate in methanol
followed by styrene to give the methoxyselenenylation products
23–30.
The yields of the methoxyselenenylation reaction and the dia-
stereomeric ratio of adducts are presented in Table 1. The best
results (70:30) were obtained for (+)-dineomenthyl diselenide 3
and (ꢀ)-diisomenthyl diselenide 10.
In order to determine the influence of the structure of the disel-
enides on the diastereoselectivity in the methoxyselenenylation
reactions, we conducted the optimization of the chair conformers
geometry of the terpeneselenenyl bromides from the p-menthyl
group at the B3LYP/6-311G(d) level. The optimized structures of
the chair conformers of terpeneselenenyl bromides and their dif-
ferences in energy have been presented in Figure 1.
On the basis of the optimized structures of terpeneselenenyl
bromides and the results of the addition reaction from Table 1, it
can be concluded that in the case of bromides 3a, 5a, 8a, and 10a
derived from (ꢀ)-menthol 1 and (+)-isomenthol 6, the stabilization
of the structure via an equatorial position of the isopropyl group
favors an increase in the diastereoselectivity. For bromide 8a, the
very low degree of selectivity can be explained by the axial posi-
tion of the isopropyl group in the dominating chair conformation
what arouse from the calculations. The position of the isopropyl
group for the neoisomenthyl structure was also postulated by
Härtner et al.21 and Senda et al.22 We assume that for bromides
17a, 18a, 21a and 22a derived from (+)-carvomenthol and (ꢀ)-neo-

´
´
1239
Z. Rafinski, J. Scianowski / Tetrahedron: Asymmetry 19 (2008) 1237–1244
O
OH
OH
OH
H2, Pt2O
AcOH
LiAlH4
Et2O, 0 ºC
+
12
11
13
40 : 60
14
77%
90%
TsCl, py
24 h, 0 ºC
TsCl, py
24 h, 0 ºC
CCl4, PPh3
24 h, reflux
CCl4, PPh3
24 h, reflux
OTs
Cl
OTs
Cl
20
16
15
19
61%
55%
30%
68%
Na2Se2
DMF, 2 h, 100 ºC
Na2Se2
DMF, 1 h, 100 ºC
Na2Se2
DMF, 1 h, 100 ºC
Na2Se2
DMF, 2 h, 100 ºC
Se)2
Se)2
Se)2
Se)2
21
56%
22
36%
17
69%
18
42%
Scheme 3. Synthesis of diselenides derived from (+)-carvomenthol 13 and (ꢀ)-neoisocarvomenthol 14.
OMe
*
1. AgOTf, MeOH
2. Styrene
CH2Cl2, —78 ºC
1M Br2, CCl4
CH2Cl2, —78 ºC
Ter Se
Ter Se)2
Ter SeBr
Ter – terpene moiety
Scheme 4. Asymmetric methoxyselenenylation reaction with the use of diselenides from the p-menthane group.
isocarvomenthol, the position of the group with selenium in the
vicinity of a methyl group but not the isopropyl one, causes a
decrease in the stereoselectivity of the addition products. Better
diastereomeric ratios have been observed for bromides 17a and
18a, whose structures are stabilized by the diequatorial position
of the alkyl groups. By comparing the calculated energies of the
more stable conformers for terpeneselenenyl bromides 5a and 8a
(D = 16.57 kJ/mol), 17a and 21a (D = 1.31 kJ/mol) as well as 18a
and 22a (D = 4.16 kJ/mol), which differed only by the stereochem-
istry of the isopropyl or methyl group, we were able to demon-
strate that the bromides 5a, 17a, and 18a are more energetically
stable. In all cases, a greater stability of the compared bromides
correlated with an increase of a stereoselectivity of the selenenyla-
tion products of styrene. For bromides 3a and 10a (D = 5.27 kJ/mol)
in spite of the greater stability of the bromide 10a no addition to
styrene was observed, probably due to an increase in stereoselec-
tivity caused by an isopropyl group at the equatorial position as
evidenced on the basis of calculations, thus can influence the struc-
tures of the selenenyl bromides 3a and 10a.
synthesis of the dialkyl diselenide from p-menthane group. The
best diastereomeric ratio for methoxyselenenylation of styrene
was obtained for (+)-dineomenthyl diselenide 3 and (ꢀ)-diisomen-
thyl diselenide 10, when the reaction was carried out at ꢀ78 °C. On
the basis of the experimental results of the methoxyselenenylation
reaction and theoretical calculations by the DFT method of the sta-
bility of the selenenyl electrophiles conformers from the p-men-
thane system, we assume that the stiffering of the selenium
electrophile structure by an equatorial arrangement of the alkyl
groups can considerably influence the diastereomeric ratio of the
methoxyselenenylation products.
4. Experimental
Melting points were measured with a Büchi Tottoli SPM-20
heating unit and are uncorrected. NMR spectra were recorded on
Bruker AM-300 at 300 MHz or Varian 200 at 200 MHz for 1H and
75.5 MHz or 50.3 MHz for 13C. Chemical shifts are expressed in
parts per million (ppm) relative to TMS. 77Se NMR spectra were
recorded on Varian 200 with diphenyl diselenide as an external
standard. Elemental analyses were performed on a Vario MACRO
CHN analyzer. TLC was conducted on precoated silica gel plates
(Merck 60F254) and the spots were visualized under UV light.
Column chromatography was carried out on column using Silica
3. Conclusions
It has been demonstrated that the reaction of sodium diselenide
with alkyl tosylates and chlorides is a convenient method for the

´
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Z. Rafinski, J. Scianowski / Tetrahedron: Asymmetry 19 (2008) 1237–1244
1240
(c 5.14, CHCl3); 1H NMR (300 MHz, CDCl3): d = 1.43–1.46 (m, 1H),
1.50 (dt, JH,H = 12.0, 9.6 Hz, 1H), 1.73–1.79 (m, 6H), 1.89–2.01 (m,
1H), 2.03–2.08 (m, 1H), 2.10–2.20 (m, 1H), 2.22–2.32 (m, 1H),
4.15–4.25 (m, 1H), 4.73 (m, 2H), 5.50 (m, 1H) ppm; 13C NMR
(50.3 MHz, CDCl3): d = 18.9 (CH3), 20.6 (CH3), 31.0 (CH2), 38.0
(CH2), 40.4 (CH), 70.8 (CH), 109.1 (@CH2), 123.8 (@CH), 136.2
Table 1
Methoxyselenenylation of styrene with the use of diselenides from the p-menthane
group
Entry
1
Diselenide
Product
dra
Yield (%)
86b
70:30b
(C@), 148.9 (C@) ppm. Elemental Anal. Calcd for
C10H16O
(152.23): C, 78.90; H, 10.59. Found: C, 78.88; H, 10.34.
*
Se)2
Se
OMe
23
3
4.2. (+)-(1S,2S,5S)-Carvomenthol 13
20
Yield 58%; colorless oil; ½aꢂD ¼ þ25:6 (c 5.36, CHCl3); 1H NMR
(300 MHz, CDCl3): d = 0.86 (s, 3H; CH3), 0.88 (s, 3H; CH3), 0.90–
0.99 (m, 2H), 1.00 (d, JH,H = 6.6 Hz, 3H; CH3), 1.08–1.28 (m, 3H),
1.38–1.51 (m, 2H), 1.57–1.64 (m, 1H), 1.69–1.76 (m, 1H), 1.91–
1.98 (m, 1H), 3.08–3.16 (m, 1H) ppm; 13C NMR (75.5 MHz, CDCl3):
d = 18.3 (CH3), 19.7 (CH3), 19.8 (CH3), 29.0 (CH2), 32.5 (CH), 33.2
(CH2), 38.8 (CH2), 40.2 (CH), 43.1 (CH), 76.6 (CH) ppm. Elemental
Anal. Calcd for C10H20O (156.27): C, 76.86; H, 12.90. Found: C,
76.80; H, 12.78.
2
3
62:38b
52:48
79b
*
Se
Se
)
2
OMe
24
5
42
*
Se
Se)
2
OMe
25
8
4.3. (ꢀ)-(1S,2R,5S)-Neoisocarvomenthol 14
24
Yield 70%; colorless oil; ½aꢂD ¼ ꢀ37:3 (c 15.7, CHCl3); 1H NMR
4
5
70:30
72
79
*
Se
)
Se
2
2
(200 MHz, CDCl3): d = 0.86 (s, 3H; CH3), 0.88 (s, 3H; CH3), 0.90 (d,
JH,H = 7.0 Hz, 3H; CH3), 1.06–1.28 (m, 4H), 1.31–1.54 (m, 3H),
1.60–1.69 (m, 2H), 2.02–2.08 (m, 1H), 3.74 (m, 1H) ppm; 13C
NMR (50.3 MHz, CDCl3): d = 10.5 (CH3), 19.7 (CH3), 19.8 (CH3),
22.5 (CH2), 30.6 (CH2), 32.3 (CH2), 32.6 (CH), 33.8 (CH), 43.1 (CH),
72.9 (CH) ppm. Elemental Anal. Calcd for C10H20O (156.27): C,
76.86; H, 12.90. Found: C, 76.85; H, 12.93.
OMe
10
26
OMe
*
Se)
Se
64:36
17
27
4.4. Preparation of tosylates: general procedure
OMe
*
Se)
2
Se
Tosyl chloride (110 mmol) was added in one portion to a solu-
tion of the terpene alcohol (100 mmol) in pyridine (125 mL) at 0 °C.
The reaction mixture was stirred for 1 h at the same temperature
and then for 24 h at room temperature, after which it was poured
to water (100 mL). The resulting precipitate was filtered off and
dried under vacuum. The crude product was purified by the crys-
tallization from petroleum ether.
6
7
65:35
52:48
75
51
18
28
OMe
*
Se
)
2
Se
4.4.1. (+)-(1S,2R,5R)-Isomenthyl tosylate 7
21
25
29
Yield 72%; white crystals; mp 83–84 °C; ½aꢂD ¼ þ10:1 (c 10.90,
CHCl3); 1H NMR (200 MHz, CDCl3): d = 0.75 (d, JH,H = 6.8 Hz, 3H;
CH3), 0.79 (d, JH,H = 6.8 Hz, 3H; CH3), 0.85 (d, JH,H = 6.8 Hz, 3H;
CH3), 0.99–1.77 (m, 8H), 1.78–1.96 (m, 1H), 2.48 (s, 3H; CH3),
4.71 (dt, JH,H = 5.8, 3.2 Hz, 1H; CH), 7.34 (d, JH, H = 7.8 Hz, 2H;
2 ꢁ CHar), 7.78 (d, JH,H = 7.8 Hz, 2H; 2 ꢁ CHar) ppm; 13C NMR
(50.3 MHz, CDCl3): d = 19.1 (CH3), 20.7 (CH2), 20.8 (2 ꢁ CH3), 21.5
(CH3), 25.9 (CH), 27.0 (CH), 29.2 (CH2), 36.1 (CH2), 45.7 (CH), 81.9
(CH), 127.7 (2 ꢁ CHar), 129.6 (2 ꢁ CHar), 134.8 (Car), 144.2 (Car)
ppm. Elemental Anal. Calcd for C17H26O3S (310.45): C, 65.77; H,
8.44. Found: C, 65.66; H, 8.32.
OMe
*
Se)
2
Se
8
56:44
41
22
30
Diastereomeric ratios were established on the basis of 1H and 77Se NMR spectra.
Ref. 10.
a
b
4.4.2. (+)-(1S,2S,5S)-Carvomenthyl tosylate 15
Gel 60 Merck (70–230 mesh). Methanol was distilled from magne-
sium turnings. Dichloromethane was distilled from calcium
hydride and restored under molecular sieves 4 Å. All reactions
requiring anhydrous conditions were conducted in flame-dried
apparatus.
26
Yield 61%; white crystals; mp 55–56 °C; ½aꢂD ¼ þ48:5 (c 10.11,
CHCl3); 1H NMR (300 MHz, CDCl3): d = 0.76 (d, JH,H = 6.8 Hz, 3H;
CH3), 0.77 (d, JH,H = 6.8 Hz, 3H; CH3), 0.80 (d, JH,H = 6.6 Hz, 3H;
CH3), 0.84–1.22 (m, 3H), 1.36–1.63 (m, 4H), 1.70–1.81 (m, 1H),
1.93–2.01 (m, 1H), 2.43 (s, 3H; CH3), 4.11 (m, 1H), 7.33 (d,
JH,H = 8.2 Hz, 2H; 2 ꢁ CHar), 7.79 (d, JH,H = 8.2 Hz, 2H; 2 ꢁ CHar)
ppm; 13C NMR (75.5 MHz, CDCl3): d = 18.3 (CH3), 19.5 (CH3), 19.6
(CH3), 21.6 (CH3), 28.2 (CH2), 32.2 (CH), 33.1 (CH2), 36.4 (CH2),
37.7 (CH), 42.9 (CH), 88.5 (CH), 127.7 (2 ꢁ CHar), 129.8 (2 ꢁ CHar),
4.1. (+)-cis-Carveol 12
The product was isolated by the distillation under reduced pres-
23
sure 65–66 °C/0.4 mmHg. Yield 77%; colorless liquid; ½aꢂD ¼ þ44:1

´
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Z. Rafinski, J. Scianowski / Tetrahedron: Asymmetry 19 (2008) 1237–1244
Δ = 30.60 kJ/mol
Δ = 23.55 kJ/mol
More stable
conformer
3a
More stable
conformer
5a
Δ = 6.09 kJ/mol
Δ = 1.33 kJ/mol
8a
More stable
conformer
More stable
conformer
10a
Δ = 12.01 kJ/mol
Δ = 20.06 kJ/mol
More stable
conformer
17a
More stable
conformer
18a
Δ = 2.46 kJ/mol
Δ = 13.03 kJ/mol
21a
More stable
conformer
More stable
conformer
22a
Figure 1. Optimized structures of the terpeneselenenyl bromides from p-menthane group.
134.8 (Car), 144.3 (Car) ppm. Elemental Anal. Calcd for C17H26O3S
(310.45): C, 65.77; H, 8.44. Found: C, 65.70; H, 8.35.
(300 mL) was added. The precipitate formed was filtered off under
vacuum, and the filtrate was concentrated and evaporated by
means of a rotary evaporator.
4.4.3. (ꢀ)-(1S,2R,5S)-Neoisocarvomenthyl tosylate 19
26
Yield 55%; white crystals; mp 62–63 °C; ½aꢂD ¼ ꢀ5:5 (c 4.90,
4.5.1. (+)-(1R,2R,4R)-Neoisomenthyl chloride 9
CHCl3); 1H NMR (200 MHz, CDCl3): d = 0.80 (d, JH,H = 6.8 Hz, 3H;
CH3), 0.82 (d, JH,H = 6.8 Hz, 3H; CH3), 0.90 (d, JH,H = 7.0 Hz, 3H;
CH3), 1.00–1.18 (m, 2H), 1.21–1.70 (m, 6H), 2.01–2.19 (m, 1H),
2.44 (s, 3H; CH3), 4.58 (dt, JH,H = 11.4, 4.8 Hz, 1H; CH), 7.32 (d,
JH,H = 8.4 Hz, 2H; 2 ꢁ CHar), 7.80 (d, JH,H = 8.4 Hz, 2H; 2 ꢁ CHar)
ppm; 13C NMR (50.3 MHz, CDCl3): d = 11.2 (CH3), 19.6 (2 ꢁ CH3),
21.5 (CH2), 21.9 (CH3), 29.9 (CH2), 30.3 (CH2), 32.1 (CH), 32.3
(CH), 43.1 (CH), 85.0 (CH), 127.5 (2 ꢁ CHar), 129.6 (2 ꢁ CHar),
135.0 (Car), 144.2 (Car) ppm. Elemental Anal. Calcd for C17H26O3S
(310.45): C, 65.77; H, 8.44. Found: C, 65.70; H, 8.37.
Purification by the crystallization from petroleum ether. Yield
25
41%; white crystals; mp 81–82 °C; ½aꢂD ¼ þ23:9 (c 5.10, CHCl3);
1H NMR (200 MHz, CDCl3): d = 0.85 (d, JH,H = 7.0 Hz, 3H; CH3),
0.90 (s, 3H; CH3), 0.94 (s, 3H; CH3), 1.08–1.64 (m, 7H) 1.86–2.03
(m, 2H), 3.77 (dt, JH,H = 7.8, 4.0 Hz, 1H; CH) ppm; 13C NMR
(50.3 MHz, CDCl3): d = 18.1 (CH3), 19.6 (CH2), 19.9 (CH3), 21.0
(CH3), 26.0 (CH), 27.5 (CH), 30.5 (CH2), 40.0 (CH2), 49.6 (CH), 67.8
(CH) ppm. Elemental Anal. Calcd for C10H19Cl (174.71): C, 68.75;
H, 10.96. Found: C, 68.70; H, 10.92.
4.5.2. (ꢀ)-(1S,2R,4S)-Neocarvomenthyl chloride 16
4.5. Preparation of chlorides: general procedure
Purification by column chromatography on silica gel with
petroleum ether/ethyl acetate, 95:5. Yield 68%; colorless liquid;
25
A solution of the terpene alcohol (100 mmol) and triphenyl-
phosphine (110 mmol) in carbon tetrachloride (240 mL) was re-
fluxed for 24 h, after which it was cooled and petroleum ether
½aꢂD ¼ ꢀ38:1 (c 5.70, CHCl3); 1H NMR (200 MHz, CDCl3): d = 0.86
(d, JH,H = 6.6 Hz, 3H; CH3), 0.87 (d, JH,H = 6.6 Hz, 3H; CH3), 0.99 (d,
JH,H = 6.6 Hz, 3H; CH3), 1.02–1.15 (m, 1H), 1.38–1.79 (m, 7H),

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Z. Rafinski, J. Scianowski / Tetrahedron: Asymmetry 19 (2008) 1237–1244
1242
2.02–2.13 (m, 1H), 4.36 (m, 1H) ppm; 13C NMR (50.3 MHz, CDCl3):
d = 19.5 (CH3), 19.7 (CH3), 19.8 (CH3), 28.0 (CH2), 28.9 (CH2), 32.1
(CH), 36.2 (CH), 37.2 (CH), 38.1 (CH2), 67.2 (CH) ppm. Elemental
Anal. Calcd for C10H19Cl (174.71): C, 68.75; H, 10.96. Found: C,
68.62; H, 10.78.
4.6.4. (+)-(1S,2S,5S,10S,20S,50S)-Dicarvomenthyl diselenide 18
20
Yield 42%; yellow oil; ½aꢂD ¼ þ256:7 (c 0.60, CHCl3); 1H NMR
(300 MHz, CDCl3): d = 0.88 (d, JH,H = 6.8 Hz, 3H; CH3), 0.87 (d,
JH,H = 6.8 Hz, 3H; CH3), 0.94–1.18 (m, 3H), 1.09 (d, JH,H = 6.6 Hz,
3H; CH3), 1.23–1.53 (m, 3H), 1.64–1.73 (m, 1H), 1.78–1.88 (m,
1H), 2.16–2.28 (m, 1H), 2.51–2.67 (m, 1H) ppm; 13C NMR
(50.3 MHz, CDCl3): d = 19.7 (CH3), 19.8 (CH3), 22.2 (CH3), 29.3
(CH2), 32.7 (CH), 36.0 (CH2), 38.6 (CH), 39.8 (CH2), 45.5 (CH), 52.2
(CH) ppm; 77Se NMR (38.1 MHz, CDCl3): d = 352.2 ppm. Elemental
Anal. Calcd for C20H38Se2 (436.44): C, 55.04; H, 8.77. Found: C,
54.94; H, 8.75.
4.5.3. (ꢀ)-(1R,2R,4S)-Isocarvomenthyl chloride 20
The product was isolated by the distillation under reduced pres-
22
sure 30–31 °C/0.1 mmHg. Yield 30%; colorless liquid; ½aꢂD ¼ ꢀ43:8
(c 3.15, CHCl3); 1H NMR (200 MHz, CDCl3): d = 0.86 (d, JH,H = 6.0 Hz,
3H; CH3), 0.89 (d, JH,H = 6.0 Hz, 3H; CH3), 1.04 (d, JH,H = 7.4 Hz, 3H;
CH3), 1.20–1.39 (m, 1H), 1.40–1.57 (m, 4H), 1.68–2.03 (m, 4H),
3.95–4.03 (m, 1H) ppm; 13C NMR (50.3 MHz, CDCl3): d = 18.8
(CH3), 20.2 (CH3), 20.4 (CH3), 24.9 (CH2), 27.6 (CH2), 29.6 (CH),
35.4 (CH2), 38.2 (CH), 39.4 (CH), 64.9 (CH) ppm. Elemental Anal.
Calcd for C10H19Cl (174.71): C, 68.75; H, 10.96. Found: C, 68.72;
H, 10.92.
4.6.5. (ꢀ)-(1R,2R,5S,10S,20R,50S)-Diisocarvomenthyl diselenide
21
20
Yield 56%; yellow oil; ½aꢂD ¼ ꢀ66:6 (c 10.64, CHCl3); 1H NMR
(200 MHz, CDCl3): d = 0.87 (d, JH,H = 6.6 Hz, 3H; CH3), 0.88 (d,
JH,H = 6.6 Hz, 3H; CH3), 1.06 (d, JH,H = 6.8 Hz, 3H; CH3), 1.22–1.59
(m, 6H), 1.69–2.00 (m, 3H), 3.14 (m, 1H) ppm; 13C NMR
(50.3 MHz, CDCl3,): d = 20.2 (CH3), 20.3 (CH3), 20.4 (CH3), 25.3
(CH2), 28.7 (CH2), 29.9 (CH), 33.2 (CH2), 35.3 (CH), 40.4 (CH), 49.6
(CH) ppm; 77Se NMR (38.1 MHz, CDCl3): d = 366.1 ppm. Elemental
Anal. Calcd for C20H38Se2 (436.44): C, 55.04; H, 8.77. Found: C,
55.01; H, 8.72.
4.6. Preparation of diselenides: general procedure
The standard synthesis of diselenides was conducted under
argon, by dropping hydrazine hydrate (0.6 mL) into a mixture of
selenium (22 mmol) and sodium hydroxide (33 mmol) in DMF
(20 mL). After heating at 100 °C for 15 min, the reaction mixture
was cooled to ambient temperature and the respective tosylate
(22 mmol) or chloride (22 mmol) was added. The solution was
heated again at 100 °C for 1 h (2 h for chlorides). The reaction mix-
ture was cooled, poured into water (100 mL), and extracted with
petroleum ether (3 ꢁ 100 mL). The combined ether layers were
washed with water (100 mL), dried over anhydrous MgSO4, and
evaporated. The product was purified by column chromatography
(petroleum ether, silica gel).
4.6.6. (+)-(1S,2R,5S,10S,20R,50S)-Dineoisocarvomenthyl
diselenide 22
25
Yield 36%; yellow oil; ½aꢂD ¼ þ80:4 (c 0.95, CHCl3); 1H NMR
(300 MHz, CDCl3): d = 0.88 (d, JH,H = 6.9 Hz, 3H; CH3), 0.87 (d,
JH,H = 6.9 Hz, 3H; CH3), 0.97 (d, JH,H = 7.2 Hz, 3H; CH3), 1.09–1.26
(m, 3H), 1.36–1.52 (m, 3H), 1.68–1.76 (m, 1H), 1.92–2.00 (m,
1H), 2.20–2.34 (m, 1H), 3.32 (dt, JH,H = 13.2, 3.9 Hz, 1H) ppm; 13C
NMR (50.3 MHz, CDCl3): d = 13.2 (CH3), 19.7 (2 ꢁ CH3), 22.6
(CH2), 31.9 (CH2), 32.7 (CH), 32.9 (CH), 33.4 (CH2), 46.1 (CH), 50.7
(CH) ppm; 77Se NMR (38.1 MHz, CDCl3): d = 353.8 ppm. Elemental
Anal. Calcd for C20H38Se2 (436.44): C, 55.04; H, 8.77. Found: C,
55.00; H, 8.56.
4.6.1. (ꢀ)-(1R,2R,5R,10R,20R,50R)-Dineoisomenthyl diselenide 8
25
Yield 85%; yellow liquid; ½aꢂD ¼ ꢀ232:5 (c 6.70, CHCl3); 1H NMR
(200 MHz, CDCl3): d = 0.95 (d, JH,H = 6.6 Hz, 3H; CH3), 1.00 (d,
JH,H = 6.6 Hz, 3H; CH3), 1.03 (d, JH,H = 6.6 Hz, 3H; CH3), 1.17–1.35
(m, 1H), 1.40–1.58 (m, 3H), 1.60–1.98 (m, 4H), 2.05–2.18 (m,
1H), 3.47–3.56 (m, 1H) ppm; 13C NMR (50.3 MHz, CDCl3):
d = 21.7 (CH3), 22.1 (CH3), 22.9 (CH3), 26.8 (CH2), 28.7 (CH), 30.7
(CH2), 32.4 (CH), 39.3 (CH2), 46.8 (CH), 52.0 (CH) ppm; 77Se NMR
(38.1 MHz, CDCl3): d = 395.8 ppm. Elemental Anal. Calcd for
C20H38Se2 (436.44): C, 55.04; H, 8.77. Found: C, 54.92; H, 8.89.
4.7. General procedure for asymmetric methoxyselenenylation
A typical experimental procedure for the asymmetric methox-
yselenenylation of styrene is as follows. To a CH2Cl2 solution
(14.0 mL) of diselenide (210 mg, 0.48 mmol) at ꢀ78 °C was slowly
added a CCl4 (0.48 mL) solution of bromine (77 mg, 0.48 mmol)
under an argon atmosphere. After 15 min, a solution of silver
triflate (270 mg, 1.05 mmol) in methanol (0.74 mL) was added.
The resulting heterogeneous mixture was stirred at ꢀ78 °C for
20 min. Next styrene (250 mg, 2.40 mmol) was added to the solu-
tion and stirred for 2 h at the same temperature. The mixture was
treated with an aqueous solution of 10% NaHCO3, extracted with
CH2Cl2 (3 ꢁ 20 mL), after which the combined organic phases were
dried over MgSO4. The solvent was removed under reduced pres-
sure, and the residue was purified by chromatography on silica
gel, yielding the addition products as yellow oils. The diastereo-
meric excess was determined by 1H and 77Se NMR spectra.
4.6.2. (+)-(1S,2R,5R,10S,20R,50R)-Diisomenthyl diselenide 10
22
Yield 40%; yellow liquid; ½aꢂD ¼ þ27:6 (c 0.90, CHCl3); 1H NMR
(200 MHz, CDCl3): d = 0.88 (d, JH,H = 6.6 Hz, 3H; CH3), 0.90 (d,
JH,H = 6.6 Hz, 3H; CH3), 0.92 (d, JH,H = 6.6 Hz, 3H; CH3), 1.08–1.33
(m, 3H), 1.38–2.06 (m, 6H), 3.47–3.54 (m, 1H) ppm; 13C NMR
(75.5 MHz, CDCl3): d = 19.3 (CH3), 20.8 (CH3), 21.2 (CH3), 22.1
(CH2), 27.8 (CH), 28.6 (CH), 30.4 (CH2), 38.0 (CH2), 46.8 (CH), 47.2
(CH) ppm; 77Se NMR (38.1 MHz, CDCl3): d = 375.4 ppm. Elemental
Anal. Calcd for C20H38Se2 (436.44): C 55.04, H 8.77; found: C, 54.83;
H, 8.53.
4.6.3. (ꢀ)-(1R,2S,5S,10R,20S,50S)-Dineocarvomenthyl diselenide
4.7.1. ((1R,2R,5R)-2-Isopropyl-5-methylcyclohexyl)(2-methoxy-
2-phenylethyl)selane 25
17
20
Yield 69%; yellow oil; ½aꢂD ¼ ꢀ195:5 (c 3.36, CHCl3); 1H NMR
Purification by column chromatography on silica gel with
petroleum ether/ethyl acetate, 95:5. Yield 42%; yellowish oil; 1H
NMR (300 MHz, CDCl3): major diastereomer d = 0.82–1.04 (m,
10H), 1.12–1.98 (m, 9H), 2.73 (dd, JH,H = 12.2, 5.4 Hz, 1H; CH2Se),
2.99 (dd, JH,H = 12.2, 8.4 Hz, 1H; CH2Se), 3.24 (s, 3H; OCH3), 4.33
(dd, JH,H = 8.4, 5.4 Hz, 1H; CH), 7.34 (m, 5H; 5 ꢁ CHar) ppm; minor
diastereomer—only separated signals: 2.68 (dd, JH,H = 12.2, 5.4 Hz,
1H; CH2Se) ppm; 13C NMR (50.3 MHz, CDCl3): major diastereomer
d = 21.7 (CH3), 22.0 (CH3), 22.9 (CH3), 27.0 (CH2), 28.5 (CH), 30.6
(200 MHz, CDCl3): d = 0.86 (d, JH,H = 6.4 Hz, 3H; CH3), 0.87 (d,
JH,H = 6.4 Hz, 3H; CH3), 1.04 (d, JH,H = 6.6 Hz, 3H; CH3), 1.16–1.40
(m, 2H), 1.41–1.60 (m, 5H), 1.64–1.74 (m, 1H), 2.26–2.34 (m,
1H), 3.55 (m, 1H) ppm; 13C NMR (50.3 MHz, CDCl3): d = 19.7
(CH3), 19.9 (CH3), 21.9 (CH3), 29.4 (CH2), 30.9 (CH2), 32.4 (CH),
37.3 (CH2), 37.4 (CH), 38.6 (CH), 57.6 (CH) ppm; 77Se NMR
(38.1 MHz, CDCl3): d = 306.1 ppm. Elemental Anal. Calcd for
C20H38Se2 (436.44): C, 55.04; H, 8.77. Found: C, 55.08; H, 8.82.

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Z. Rafinski, J. Scianowski / Tetrahedron: Asymmetry 19 (2008) 1237–1244
(CH2), 32.1 (CH2), 32.7 (CH), 39.1 (CH2), 44.9 (CH), 45.7 (CH), 56.8
(OCH3), 84.5 (CH), 126.6 (2 ꢁ CHar), 127.8 (CHar), 128.3 (2 ꢁ CHar),
141.5 (Car) ppm; minor diastereomer—only separated signals: 27.2
(CH2), 28.3 (CH), 30.5 (CH2), 32.0 (CH2), 32.5 (CH), 56.7 (OCH3),
126.7 (2 ꢁ CHar) ppm; 77Se NMR (38.1 MHz, CDCl3): major diaste-
reomer d = 231.1 ppm; minor diastereomer: 233.1 ppm. Elemental
Anal. Calcd for C19H30OSe (353.4): C, 64.57; H, 8.56. Found: C,
64.40; H, 8.52.
35.9 (CH2), 38.8 (CH), 39.4 (CH2), 45.4 (CH), 48.1 (CH), 56.9
(OCH3), 84.6 (CH), 126.7 (2 ꢁ CHar), 127.9 (CHar), 128.4 (2 ꢁ CHar),
141.4 (Car) ppm; minor diastereomer—only separated signals: 22.0
(CH3), 29.3 (CH2), 38.6 (CH), 39.3 (CH2), 45.3 (CH), 84.5 (CH), 126.8
(2 ꢁ CHar) ppm; 77Se NMR (38.1 MHz, CDCl3): major diastereomer
d = 212.4 ppm; minor diastereomer: 214.2 ppm. Elemental Anal.
Calcd for C19H30OSe (353.4): C, 64.57; H, 8.56. Found: C, 64.48;
H, 8.49.
4.7.2. ((1S,2R,5R)-2-Isopropyl-5-methylcyclohexyl)(2-methoxy-
2-phenylethyl)selane 26
4.7.5. ((1R,2R,5S)-5-Isopropyl-2-methylcyclohexyl)(2-methoxy-
2-phenylethyl)selane 29
Purification by column chromatography on silica gel with
petroleum ether/ethyl acetate, 95:5. Yield 72%; yellowish oil; 1H
NMR (300 MHz, CDCl3): major diastereomer d = 0.80–0.94 (m,
9H), 1.04–1.94 (m, 10H), 2.70 (dd, JH,H = 12.4, 5.6 Hz, 1H; CH2Se),
2.97 (dd, JH,H = 12.4, 8.0 Hz, 1H; CH2Se), 3.24 (s, 3H; OCH3), 4.32
(dd, JH,H = 8.0, 5.6 Hz, 1H; CH), 7.34 (m, 5H; 5 ꢁ CHar) ppm; minor
diastereomer—only separated signals: 2.65 (dd, JH,H = 12.4, 5.6 Hz,
1H; CH2Se) ppm; 13C NMR (50.3 MHz, CDCl3): major diastereomer
d = 19.5 (CH3), 21.0 (CH3), 21.3 (CH3), 22.4 (CH2), 27.5 (CH),
28.7 (CH), 30.2 (CH2), 31.0 (CH2), 37.9 (CH2), 42.0 (CH), 47.2 (CH),
56.9 (OCH3), 84.7 (CH), 126.7 (2 ꢁ CHar), 127.9 (CHar), 128.4
(2 ꢁ CHar), 141.5 (Car) ppm; minor diastereomer—only separated
signals: 19.4 (CH3), 20.9 (CH3), 22.3 (CH2), 41.8 (CH), 84.4 (CH)
ppm; 77Se NMR (38.1 MHz, CDCl3): d = 238.2 ppm. Elemental Anal.
Calcd for C19H30OSe (353.4): C, 64.32; H, 8.56. Found: C, 64.40; H,
8.35.
Purification by column chromatography on silica gel with
petroleum ether/ethyl acetate, 95:5. Yield 51%; yellowish oil; 1H
NMR (300 MHz, CDCl3): major diastereomer d = 0.83 (d,
JH,H = 6.6 Hz, 3H; CH3), 0.86 (d, JH,H = 6.6 Hz, 3H; CH3), 0.99 (d,
JH,H = 7.0 Hz, 3H; CH3), 1.22–1.48 (m, 5H), 1.54–1.92 (m, 4H),
2.75 (dd, JH,H = 12.3, 5.8 Hz, 1H; CH2Se), 2.80–2.90 (m, 1H), 2.98
(dd, JH,H = 12.3, 7.8 Hz, 1H; CH2Se), 3.24 (s, 3H; OCH3), 4.32 (dd,
JH,H = 7.8, 5.8 Hz, 1H; CH), 7.34 (m, 5H; 5 ꢁ CHar) ppm; minor dia-
stereomer—only separated signals: 0.84 (d, JH,H = 6.6 Hz, 3H; CH3),
0.87 (d, JH,H = 6.6 Hz, 3H; CH3), 1.01 (d, JH,H = 7.0 Hz, 3H; CH3), 4.30
(dd, JH,H = 7.8, 5.8 Hz, 1H; CH) ppm; 13C NMR (75.5 MHz, CDCl3):
major diastereomer d = 19.9 (CH3), 20.1 (CH3), 20.3 (CH3), 24.9
(CH2), 28.7 (CH2), 30.2 (CH), 30.9 (CH2), 32.8 (CH2), 35.5 (CH),
40.3 (CH), 45.2 (CH), 56.9 (OCH3), 84.5 (CH), 126.6 (2 ꢁ CHar),
127.9 (CHar), 128.4 (2 ꢁ CHar), 141.4 (Car) ppm; minor diastereo-
mer—only separated signals: 20.0 (CH3), 20.2 (CH3), 28.6 (CH3),
30.1 (CH), 32.7 (CH2), 35.4 (CH), 40.4 (CH), 45.1 (CH), 128.5
(2 ꢁ CHar) ppm; 77Se NMR (38.1 MHz, CDCl3): major diastereomer
d = 238.3 ppm; minor diastereomer: 238.7 ppm. Elemental Anal.
Calcd for C19H30OSe (353.4): C, 64.57; H, 8.56. Found: C, 64.41;
H, 8.52.
4.7.3. ((1R,2S,5S)-5-Isopropyl-2-methylcyclohexyl)(2-methoxy-
2-phenylethyl)selane 27
Purification by column chromatography on silica gel with
petroleum ether/ethyl acetate, 95:5. Yield 79%; yellowish oil; 1H
NMR (300 MHz, CDCl3): major diastereomer d = 0.84 (d,
JH,H = 6.6 Hz, 3H; CH3), 0.85 (d, JH,H = 6.6 Hz, 3H; CH3), 0.97 (d,
JH,H = 6.6 Hz, 3H; CH3), 1.17–1.56 (m, 7H), 1.61–1.67 (m, 1H),
1.96–2.08 (m, 1H), 2.68 (dd, JH,H = 12.0, 5.4 Hz, 1H; CH2Se), 2.99
(dd, JH,H = 12.0, 8.4 Hz, 1H; CH2Se), 3.08–3.18 (m, 1H), 3.24 (s,
3H; OCH3), 4.32 (dd, JH,H = 8.4, 5.4 Hz, 1H; CH), 7.34 (m, 5H;
5 ꢁ CHar) ppm; minor diastereomer—only separated signals: 2.72
(dd, JH,H = 12.0, 5.4 Hz, 1H; CH2Se), 2.95 (dd, JH,H = 12.0, 8.4 Hz,
1H; CH2Se), 4.35 (dd, JH,H = 8.4, 5.4 Hz, 1H; CH) ppm; 13C NMR
(50.3 MHz, CDCl3): major diastereomer d = 19.6 (CH3), 19.9 (CH3),
21.6 (CH3), 29.2 (CH2), 30.8 (CH2), 32.2 (CH2), 32.4 (CH), 37.4
(CH), 37.6 (CH2), 38.9 (CH), 50.8 (CH), 56.8 (OCH3), 84.8 (CH),
126.7 (2 ꢁ CHar), 127.8 (CHar), 128.5 (2 ꢁ CHar), 141.5 (Car) ppm;
minor diastereomer—only separated signals: 21.5 (CH3), 32.0
(CH2), 84.6 (CH) ppm; 77Se NMR (38.1 MHz, CDCl3): major diaste-
reomer d = 146.9 ppm; minor diastereomer: 146.0 ppm. Elemental
Anal. Calcd for C19H30OSe (353.4): C, 64.57; H, 8.56. Found: C,
64.60; H, 8.59.
4.7.6. ((1S,2R,5S)-5-Isopropyl-2-methylcyclohexyl)(2-methoxy-
2-phenylethyl)selane 30
Purification by column chromatography on silica gel with
petroleum ether/ethyl acetate, 95:5. Yield 41%; yellowish oil; 1H
NMR (200 MHz, CDCl3): major diastereomer d = 0.82 (d, JH,H
=
6.6 Hz, 3H; CH3), 0.86 (d, JH,H = 6.6 Hz, 3H; CH3), 1.22 (d,
JH,H = 7.0 Hz, 3H; CH3), 1.23–1.62 (m, 6H), 1.63–1.76 (m, 2H),
1.80–2.20 (m, 2H), 2.76 (dd, JH,H = 12.0, 5.8 Hz, 1H; CH2Se), 2.97
(dd, JH,H = 12.0, 8.4 Hz, 1H; CH2Se), 3.24 (s, 3H; OCH3), 4.33 (dd,
JH,H = 8.4, 5.8 Hz, 1H; CH), 7.34 (m, 5H; 5 ꢁ CHar) ppm; minor dia-
stereomer—only separated signals: 2.72 (dd, JH,H = 12.0, 5.8 Hz, 1H;
CH2Se), 2.92 (dd, JH,H = 12.0, 8.4 Hz, 1H; CH2Se), 4.30 (dd, JH,H = 8.4,
5.8 Hz, 1H; CH) ppm; 13C NMR (50.3 MHz, CDCl3): major diastereo-
mer d = 19.8 (CH3), 21.1 (CH3), 22.6 (CH3), 24.4 (CH2), 28.8 (CH2),
30.7 (CH), 31.9 (CH2), 34.1 (CH2), 36.6 (CH), 42.2 (CH), 46.0 (CH),
56.7 (OCH3), 84.4 (CH), 126.7 (2 ꢁ CHar), 127.9 (CHar), 128.4
(2 ꢁ CHar), 143.2 (Car) ppm; minor diastereomer—only separated
signals: 19.7 (CH3), 22.5 (CH3), 24.3 (CH2), 28.7 (CH2), 31.8 (CH2),
42.1 (CH), 45.9 (CH), 56.6 (OCH3), 84.3 (CH) ppm; 77Se NMR
(38.1 MHz, CDCl3): major diastereomer d = 226.1 ppm; minor dia-
4.7.4. ((1S,2S,5S)-5-Isopropyl-2-methylcyclohexyl)(2-methoxy-
2-phenylethyl)selane 28
Purification by column chromatography on silica gel with
petroleum ether/ethyl acetate, 95:5. Yield 75%; yellowish oil; 1H
NMR (200 MHz, CDCl3): major diastereomer d = 0.84 (d,
JH,H = 6.6 Hz, 3H; CH3), 0.85 (d, JH,H = 6.6 Hz, 3H; CH3), 0.97 (d,
JH,H = 7.0 Hz, 3H; CH3), 1.01–1.12 (m, 4H), 1.15–1.47 (m, 2H),
1.55–1.92 (m, 2H), 2.02–2.41 (m, 2H) 2.79 (dd, JH,H = 12.2, 5.4 Hz,
1H; CH2Se), 3.00 (dd, JH,H = 12.2, 8.0 Hz, 1H; CH2Se), 3.24 (s, 3H;
OCH3), 4.32 (dd, JH,H = 8.0, 5.4 Hz, 1H; CH), 7.34 (m, 5H; 5 ꢁ CHar)
ppm; minor diastereomer—only separated signals: 2.75 (dd,
JH,H = 12.2, 5.4 Hz, 1H; CH2Se), 2.93 (dd, JH,H = 12.2, 8.0 Hz, 1H;
CH2Se), 3.25 (s, 3H; OCH3), 4.30 (dd, JH,H = 8.0, 5.4 Hz, 1H; CH)
ppm; 13C NMR (75.5 MHz, CDCl3): major diastereomer d = 19.6
(CH3), 19.8 (CH3), 22.1 (CH3), 29.2 (CH2), 29.6 (CH2), 32.6 (CH),
stereomer: 229.3 ppm. Elemental Anal. Calcd for
(353.4): C, 64.57; H, 8.56. Found: C, 64.45; H, 8.42.
C19H30OSe
4.8. Computational methods
All theoretical calculations were carried out by using the
GAUSSIAN 03 program.23 The hybrid Berke 3-Lee–Yang–Parr (B3LYP)
exchange–correlation functional24,25 was applied to DFT calcula-
tions. Geometries were fully optimized at the B3LYP/6-311G(d)
level of theory. For all stable conformers, the nature as a potential
energy minimum was established at the B3LYP/6-311G(d) level by
verifying that all vibrations frequencies were real.

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Z. Rafinski, J. Scianowski / Tetrahedron: Asymmetry 19 (2008) 1237–1244
14. Selenium in Biology and Human Health; Burk, R. F., Ed.; Springer: New York,
Acknowledgments
1994.
15. Mugesh, G.; Singh, H. B. Chem. Soc. Rev. 2000, 29, 347–357.
16. Mugesh, G.; du Mont, W.-W.; Sies, H. Chem. Rev. 2001, 101, 2125–2179.
This work was financially supported by the European Social
Fund and state budget under the project of Self-government of
the Voivodeship ‘Step in the future’—scholarships for PhD students.
´
17. Scianowski, J. Tetrahedron Lett. 2005, 46, 3331–3334.
´
18. Scianowski, J.; Rafin´ ski, Z.; Wojtczak, A. Eur. J. Org. Chem. 2006, 14, 3216–3225.
´
´
19. Rafinski, Z.; Scianowski, J.; Wojtczak, A. Tetrahedron: Asymmetry 2008, 19, 223–
230.
´
´
20. Skowronek, P.; Gawronski, J.; Scianowski, J. Tetrahedron: Asymmetry 2006, 17,
2408–2412.
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