A sulfur-containing diselenide as an efficient chiral reagent in asymmetric selenocyclization reactions

Article abstract of DOI:10.1016/S0957-4166(01)00248-8

Treatment of the di-2-[(1S)-1-(methylthio)ethyl]phenyl diselenide with bromine and silver triflate afforded the corresponding selenyl triflate which was used in situ as a strongly electrophilic selenium reagent to effect the asymmetric synthesis of oxygen- or nitrogen-containing heterocycles. Cyclic ethers, lactones, lactams or N-protected pyrrolidines have been prepared in good yield with complete regioselectivity and high diastereoselectivity.

Full text of DOI:10.1016/S0957-4166(01)00248-8

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 12 (2001) 1493–1502
A sulfur-containing diselenide as an efficient chiral reagent in
asymmetric selenocyclization reactions
Marcello Tiecco,* Lorenzo Testaferri, Francesca Marini, Silvia Sternativo, Luana Bagnoli,
Claudio Santi and Andrea Temperini
Dipartimento di Chimica e Tecnologia del Farmaco, Sezione di Chimica Organica, Universita` di Perugia, I-06123 Perugia, Italy
Received 12 May 2001; accepted 29 May 2001
Abstract—Treatment of the di-2-[(1S)-1-(methylthio)ethyl]phenyl diselenide with bromine and silver triflate afforded the corre-
sponding selenyl triflate which was used in situ as a strongly electrophilic selenium reagent to effect the asymmetric synthesis of
oxygen- or nitrogen-containing heterocycles. Cyclic ethers, lactones, lactams or N-protected pyrrolidines have been prepared in
good yield with complete regioselectivity and high diastereoselectivity. © 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
the chirality transfer. In an attempt to make this inter-
action more efficient and hence to increase the
diastereoselectivity of the asymmetric addition reac-
tions, we have recently introduced the new diselenide 16
where sulfur takes the place of the oxygen or nitrogen
atom (Scheme 1). Treatment of 1 with bromine and
silver triflate afforded the corresponding selenyl triflate
2, which was employed to effect very efficient asymmet-
ric selenomethoxylations and selenohydroxylations of
alkenes.6 The addition of 2 to an alkene gives rise to a
mixture of two diastereomeric seleniranium intermedi-
ates 3 which are trapped by the nucleophile to afford a
mixture of the two enantiomerically pure diastereo-
meric addition products 4. The reaction is a stereo-
specific anti addition and the alkoxy- and hydroxy-
In recent years the introduction of a large number of
chiral non-racemic diselenides1–3 has greatly renewed
interest in organoselenium chemistry. Optically active
diselenides could in fact be easily converted into elec-
trophilic reagents which were successfully employed to
effect efficient asymmetric addition reactions to alkenes.
On the basis of much experimental evidence it has been
proposed3–5 that the high stereoselectivity observed
with these reagents is due to a non-bonded interaction,
which occurs between the selenium atom and an oxygen
or nitrogen atom positioned in close proximity. Such an
interaction forces the stereogenic center to approach
the reaction center during the addition, thus improving
Scheme 1.
* Corresponding author: Tel.: +39 075 5855100; fax: +39 075 5855116; e-mail: tiecco@unipg.it
0957-4166/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(01)00248-8

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M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
selenides 4 (Scheme 1) are formed in high chemical
yields and in diastereomeric ratios which are con-
siderably higher than those observed starting from
the corresponding oxygen- and nitrogen-containing
diselenides.1–3
depending on the relative positions of the double bond
and the nucleophilic group, the reaction products can
be the result of an exo or an endo cyclization reaction.
We report herein that the electrophilic reagent 2 can
also be employed with similarly good results to pro-
mote the ring closure reactions of alkenes bearing a
suitably positioned oxygen- or nitrogen-containing
nucleophilic group, according to the general reaction
sequence indicated in Scheme 2. This represents a con-
venient method to produce enantiomerically enriched
heterocyclic compounds. Cyclic ethers, lactones, lac-
tams and N-protected pyrrolidines can be prepared in
good chemical yield, with complete regioselectivity and
high diastereoselectivity. As indicated in Scheme 2,
2. Results and discussion
The first experiments were performed starting from the
alkenols 5a–g, which by cyclization afforded the cyclic
selenoethers 6a–g. The selenylating agent 2 was pre-
pared by treating a solution of the diselenide 1 in
dichloromethane at −78°C with bromine and then with
silver triflate. After 20 min the alkenol was added and
the mixture was stirred for 2 h. The reaction tempera-
ture was allowed to increase gradually while the pro-
gress of the reaction was monitored by TLC and/or
Scheme 2.
Table 1. Cyclization of alkenols 5a–g promoted by Ar*SeOTf 2 in CH2Cl2 at −78°C

M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
1495
GC–MS. After the usual work-up the crude reaction
mixture was examined by proton NMR to determine the
diastereomeric ratio. The pure products were obtained
after silica gel column chromatography. The
diastereomeric ratios measured on the purified products
were identical to those observed in the crude mixtures.
Reaction times, chemical yields and diastereomeric ratios
are reported in Table 1. The cyclizations of the alkenoic
acids 7a–e into the selenolactones 8a–e were carried out
in a very similar way. The only differences were that the
selenylating agent 2 was prepared in tetrahydrofuran at
−50°C. The alkenoic acids were then added at this
temperature. The results of these experiments are col-
lected in Table 2.
selenoetherification reaction, the 1,1- or 1,2-disubstituted
alkenes gave better diastereomeric ratios than the mono-
substituted alkenes, particularly if a phenyl group was
present.
The results confirm the efficiency of the sulfur-containing
selenylating agent 2. The diastereomeric ratios obtained
are in fact generally better than those observed with the
selenylating agents containing an oxygen or a nitrogen
moiety.1–3 As it has been already pointed out7 the
cyclizations of a,a-disubstituted alkenes, like 5e and 7e,
are interesting since they give rise to the formation of
quaternary stereogenic carbon atoms which are not
readily accessible by other methods.
Complete regioselectivity and high chemical yields were
observed in both types of cyclization reaction. In no case
could the two diastereoisomeric selenoethers or seleno-
lactones be separated. Good diastereoselectivities were
observed in almost every case. Preliminary experiments
indicated that a low initial temperature was necessary to
obtain good diastereoselectivities. In the case of the
In Table 2 the absolute configurations of the major
isomers of the selenolactones 8a, 8c, 8d, 8e are indicated.
These were determined after conversion into the known
butenolides 9a and 9b or g-lactones 10a and 10b by syn
elimination of the corresponding selenoxides or by reduc-
tion with Ph3SnH in the presence of catalytic amounts
of AIBN, respectively (Scheme 3). The enantiomeric
Table 2. Cyclization of alkenoic acids 7a–e promoted by Ar*SeOTf 2 in THF at −50°C
Scheme 3.

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M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
excesses were determined by proton NMR in the pres-
ence of a chiral shift reagent and/or by GC–MS using a
chiral column and were, as expected, identical to the
diastereomeric excesses of the starting products.
results of these experiments are shown in Scheme 4 and
collected in Table 3. The g-phenyl hydroxamic acid 13a
gave the N-hydroxy-g-lactam 15a, whereas the g-ethyl
hydroxamic acid 13c afforded the cyclic N-hydroxy
imidate 16. During work-up this compound was par-
tially transformed into the corresponding lactone 8c.
Compound 13b, like 13a, gave the corresponding N-
hydroxy-g-lactam 15b.
We then turned our attention to the selenocyclization
reactions leading to nitrogen-containing heterocyclic
compounds. These kinds of reaction have recently
found wider application2 since they allow the produc-
tion of a wide variety of structures starting from alke-
nes containing internal nitrogen nucleophiles. Despite
the numerous examples of cyclization reactions
reported in the literature only few asymmetric syntheses
of nitrogen-containing heterocyclic compounds from
chiral diselenides have been described.7–11 It therefore
seemed of some interest to test the efficiency of the
electrophilic reagent 2 to promote such cyclization reac-
tions. We report here the results obtained starting from
N-alkenyl acetamides 11a and 11b or from b,g-unsatu-
rated hydroxamic acids 13a–c. Under the reaction con-
ditions described above 11a and 11b afforded the
N-acetyl pyrrolidines 12a and 12b, respectively, with
good diastereomeric ratios (Table 3).
The difference in behavior observed between the phenyl
and the ethyl substituted derivatives is due to the
bidentate nature of the nucleophilic group of the
hydroxamic acids, such that the intramolecular capture
of the seleniranium ions 14 can be effected either by the
oxygen or by the nitrogen atom. In a previous work,12
using phenylselenyl sulfate as the electrophilic reagent,
we observed that the reaction products can originate
under kinetic or thermodynamic control of the reaction.
The trapping of the seleniranium intermediate by the
oxygen atom, leading to the imidate product, is faster
than trapping by nitrogen (which leads to lactam prod-
ucts). However, under the conditions employed, the
formation of the cyclic N-hydroximidate is reversible
and under appropriate reaction conditions N-hydroxy-
g-lactams can be separated as the sole reaction prod-
Interesting results were obtained in the cyclization reac-
tions of the b,g-unsaturated hydroxamic acids. The
Table 3. Cyclization of N-alkenyl acetamides 11a and 11b and of b,g-unsaturated hydroxamic acids 13a–c

M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
1497
Scheme 4.
ucts. It was also observed that the reactions of the
g-phenyl hydroxamic acids are faster than those of
g-alkyl hydroxamic acids. In contrast, under the present
reaction conditions, using the electrophilic reagent 2,
the formation of the imidate 16, deriving from the
g-ethyl hydroxamic acid 13c, is not reversible. Any
attempt to convert 16 into the corresponding lactam, by
using longer reaction times or higher temperature, even
in the presence of acid, were in fact unsuccessful.
and the 6-phenyl-(5E)-hexen-2-one,17 respectively, with
a 3 M solution of MeMgBr in diethyl ether.18
Physical and spectral data of 5a, 5e, 7b, 7e and 11b are
identical to those reported in the literature. Physical
and spectral data of all new compounds are reported
below. In the cases of hydroxamic acids the NH and
OH protons gave exchange with the solvent and were
not observed.
The results of the selenium mediated cyclization reac-
tions reported in this paper confirm that the chiral
sulfur-containing diselenide 1 is particularly efficient in
promoting asymmetric electrophilic functionalizations.
The diastereoselectivities observed are comparable or
better than those obtained with the most efficient but
less available diselenides which have been described so
far in the literature.7–11,13–15 The asymmetric synthesis
of other nitrogen-containing heterocycles promoted by
the diselenide 1 is currently under investigation.
3.1. (4E)-2-Methyl-5-phenylpent-4-en-2-ol 5b
1
Oil; H NMR: l 7.5–7.45 (m, 2H), 7.45–7.35 (m, 2H),
7.35–7.2 (m, 1H), 6.50 (dt, 1H, J=1.2, 15.8 Hz), 6.34 (dt,
1H, J=7.5, 15.8 Hz), 2.42 (dd, 2H, J=1.2, 7.5 Hz), 1.8
(br s, 1H), 1.3 (s, 6H); 13C NMR: l 137.9, 133.9, 129.0
(two carbons), 127.7, 126.6 (two carbons), 126.5, 71.4,
47.9, 29.7 (two carbons). Anal. calcd for C12H16O: C,
81.77; H, 9.15. Found: C, 81.75; H, 9.18%.
3.2. (5E)-2-Methyl-6-phenylhex-5-en-2-ol 5c
Oil; 1H NMR: l 7.5–7.2 (m, 5H), 6.5 (d, 1H, J=15.8 Hz),
6.31 (dt, 1H, J=6.9, 15.8 Hz), 2.5–2.3 (m, 2H), 2.0 (br
s, 1H), 1.8–1.7 (m, 2H), 1.38 (s, 6H); MS m/z (rel. int.):
190 (2), 172 (47), 157 (53), 143 (16), 129 (100), 117 (65),
115 (40), 104 (8), 91 (32), 77 (7), 65 (4), 59 (31), 51 (4).
Anal. calcd for C13H18O: C, 82.06; H, 9.53. Found: C,
82.26; H, 9.47%.
3. Experimental
New compounds were characterized by MS, 1H and 13
C
NMR spectroscopy. GLC analyses and MS spectra
were carried out with an HP 6890 gas chromatograph
(25 m dimethyl silicone capillary column or 25 m
Chirasil-DEX column) equipped with an HP 5973 mass
selective detector; for the ions containing selenium only
the peaks arising from the selenium-80 isotope are
3.3. N-[(3E)-4-Phenylbut-3-enyl]acetamide 11a
1
1
given. H and 13C NMR spectra were recorded at 400
Oil; H NMR: l 7.4–7.1 (m, 5H), 6.44 (dt, 1H, J=1.3,
and 100.62 MHz, respectively, on a Bruker DRX 400
instrument; unless otherwise specified, CDCl3 was used
as solvent and TMS as standard. Optical rotations were
measured with a Jasco DIP-1000 digital polarimeter.
Elemental analyses were carried out on a Carlo Erba
1106 elemental analyzer.
15.9 Hz), 6.12 (dt, 1H, J=7.0, 15.9 Hz), 5.7 (d, 1H,
J=7.0 Hz), 3.37 (q, 2H, J=7.0 Hz), 2.4 (dq, 2H, J=1.3,
7.0 Hz), 1.94 (s, 3H); MS m/z (rel. int.): 189 (5), 130 (100),
115 (36), 91 (10), 72 (7), 65 (2), 51 (2). Anal. calcd for
C12H15NO: C, 76.16; H, 7.99, N, 7.40. Found: C, 76.23;
H, 8.01, N, 7.26%.
Compounds 5d, 5f, 5g, 7a, 7c and 7d were commercially
available. Alkenols 5a and 5e,7 alkenoic acids 7b16 and
7e7, alkenamides 11a and 11b7 and hydroxamic acids
13a–c12 were synthesized according to the procedures
reported in the literature.
3.4. (3E)-4-Phenyl-3-butenoic hydroxamic acid 13a
Mp 135–137°C; 1H NMR (CD3OD): l 7.4–7.13 (m, 5H),
6.52 (d, 1H, J=15.8 Hz), 6.24 (dt, 1H, J=6.9, 15.8 Hz),
3.07 (d, 2H, J=6.9 Hz); 13C NMR: l 168.9, 136.5, 133.5,
128.1 (two carbons), 127.1, 125.8 (two carbons), 121.5,
36.7. Anal. calcd for C10H11NO2: C, 67.78; H, 6.26; N,
7.9. Found: C, 67.58; H, 6.12; N, 7.7%.
Compounds 5b and 5c were prepared treating the com-
mercially available methyl (3E)-4-phenyl-3-butenoate

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M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
3.5. (3E)-2,2-Dimethyl-4-phenyl-3-butenoic hydroxamic
acid 13b
6.0, 7.7 Hz), 1.89 (s, 3H), 1.52 (d, 3H, J=7.02 Hz); 13C
NMR: l 20.4, 13.7.
1
Mp 141–143°C; H NMR (CD3OD): l 7.42–7.16 (m,
3.9. 2,2-Dimethyl-4-({2-[(1S)-1-(methylthio)ethyl]-
5H), 6.52 (d, 1H, J=16.3 Hz), 6.31 (d, 1H, J=16.3
Hz), 1.42 (s, 6H); 13C NMR: l 174.2, 136.2, 132.9,
129.4, 128.4 (two carbons), 127.5, 126.1 (two carbons),
43.1, 24.7 (two carbons). Anal. calcd for C12H15NO2: C,
70.22; H, 7.37; N, 6.82. Found: C, 70.45; H, 7.32; N,
6.89%.
phenyl}seleno)-5-phenyltetrahydrofuran 6b
1
Oil; Major diastereoisomer: H NMR: l 7.32–7.22 (m,
3H), 7.19–7.06 (m, 5H), 6.85 (dt, 1H, J=1.5, 7.6 Hz),
4.76 (d, 1H, J=9.5 Hz), 4.38 (q, 1H, J=7.0 Hz), 3.43
(ddd, 1H, J=8.0, 9.5, 10.0 Hz), 2.33 (dd, 1H, J=8.0,
12.8 Hz), 2.0 (dd, 1H, J=10.0, 12.8 Hz), 1.82 (s, 3H),
1.31 (d, 3H, J=7.0 Hz), 1.10 (s, 6H); 13C NMR: l
145.5, 139.9, 138.1, 130.0, 128.3 (two carbons), 128.1,
127.8, 127.1, 126.8, 126.6 (two carbons), 86.1, 80.5,
48.7, 47.9, 43.9, 29.3, 28.7, 21.4, 14.0; MS m/z (rel.
int.): 406 (1), 231 (24), 183 (58), 175 (68), 174 (100), 115
(13), 105 (36), 91 (19), 77 (13). Anal. calcd for
C21H26OSSe: C, 62.22; H, 6.46. Found: C, 62.09; H,
6.59%.
3.6. (3E)-3-Hexenoic hydroxamic acid 13c
1
Mp 75–77°C; H NMR (CD3OD): l 5.75–5.38 (m, 2H),
2.88 (d, 2H, J=7.0 Hz), 1.98 (quint., 2H, J=7.1 Hz),
0.9 (t, 3H, J=7.3 Hz); 13C NMR: l 169.7, 137.3, 120.3,
36.8, 25.3, 13.1. Anal. calcd for C6H11NO2: C, 55.80; H,
8.58; N, 10.84. Found: C, 55.50; H, 8.45; N, 10.67%.
3.7. General procedure for selenocyclization reactions
1
Minor diastereoisomer (distinct signals): H NMR: l
Ar*SeOTf 2 was prepared at −78°C in dichloromethane
or at −50°C in tetrahydrofuran (see Tables 1–3) as
indicated below. The diselenide 1 (0.6 mmol), dissolved
in dichloromethane or in tetrahydrofuran (3 mL), was
treated under nitrogen with a 1 M solution of Br2 in
carbon tetrachloride (0.6 mmol). After 15 min silver
trifluoromethanesulfonate (1.3 mmol) was added and
the mixture was stirred for 20 min. The alkene (1
mmol) was added and the mixture was stirred for 2 h at
the indicated temperature. The reaction temperature
was allowed to increase gradually while the progress of
the reaction was monitored by TLC and/or GC–MS.
Reaction times are reported in Tables 1–3. The reaction
mixture was poured into an aqueous solution of 10%
NaHCO3 and extracted with dichloromethane. The
organic layer was dried over Na2SO4, filtered and evap-
orated. Reaction products were obtained in a pure form
after column chromatography of the residue on silica
gel. Reaction yields and diastereomeric ratios are
reported in Tables 1–3. Physical and spectral data of
the reaction products are described below.
6.86 (dt, 1H, J=1.5, 7.6 Hz), 4.79 (d, 1H, J=9.5 Hz),
4.40 (q, 1H, J=7.0 Hz), 3.51 (ddd, 1H, J=8.0, 9.5, 10.0
Hz), 2.27 (dd, 1H, J=8.0, 12.8 Hz), 2.01 (dd, 3H,
J=9.5, 12.4 Hz), 1.75 (s, 3H), 1.40 (d, 3H, J=7.0 Hz),
1.29 (s, 3H); 13C NMR: l 140.2, 85.6, 48.5, 48.3, 44.1,
21.5.
3.10. 2,2-Dimethyl-5-({2-[(1S)-1-(methylthio)ethyl]-
phenyl}seleno)-6-phenyltetrahydro-2H-pyran 6c
1
Oil; Major diastereoisomer: H NMR: l 7.29–7.25 (m,
3H), 7.24 (dd, 1H, J=1.3, 7.7 Hz), 7.19–7.10 (m, 4H),
6.91 (dt, 1H, J=1.6, 7.5 Hz), 4.54 (d, 1H, J=10.8 Hz),
4.23 (q, 1H, J=7.0 Hz), 3.17 (ddd, 1H, J=4.4, 10.8,
12.4 Hz), 2.02 (ddt, 1H, J=3.2, 4.4, 13.6 Hz), 1.91 (ddt,
1H, J=4.4, 12.4, 13.6 Hz), 1.81 (s, 3H), 1.63 (ddd, 1H,
J=4.4, 12.4, 13.4 Hz), 1.55 (ddd, 1H, J=3.2, 4.4, 13.4
Hz), 1.36 (d, 3H, J=7.0 Hz), 1.3 (s, 3H), 1.2 (s, 3H);
13C NMR: l 146.1, 140.8, 136.3, 129.9, 128.1, 128.0
(three carbons), 127.7 (two carbons), 126.8, 126.6, 78.4,
72.5, 47.9, 43.8, 38.1, 31.5, 29.2, 21.7, 21.5, 14.0; MS
m/z (rel. int.): 420 (8), 231 (90), 183 (100), 171 (9), 129
(13), 115 (11), 105 (20), 91 (69), 81 (11), 77 (15), 69 (12).
Anal. calcd for C22H28OSSe: C, 63.00; H, 6.73. Found:
C, 63.26; H, 6.85%.
3.8. 3-({2-[(1S)-1-(Methylthio)ethyl]phenyl}seleno)-2-
phenyltetrahydrofuran 6a
1
Oil; Major diastereoisomer: H NMR: l 7.48 (dd, 1H,
1
J=1.4, 7.7 Hz), 7.46 (dd, 1H, J=1.4, 7.7 Hz), 7.32–
7.22 (m, 6H), 7.06 (dt, 1H, J=1.4, 7.7 Hz), 4.86 (d, 1H,
J=6.0 Hz), 4.56 (q, 1H, J=7.0 Hz), 4.18 (ddd, 1H,
J=5.2, 7.7, 15.6 Hz), 4.12 (dt, 1H, J=7.2, 15.6 Hz),
3.58 (ddd, 1H, J=5.2, 6.0, 7.7 Hz), 2.50 (ddt, 1H,
J=7.2, 7.7, 13.0 Hz), 2.13 (ddt, 1H, J=5.2, 7.2, 13.0
Hz), 1.93 (s, 3H), 1.51 (d, 3H, J=7.0 Hz); 13C NMR: l
145.7, 141.2, 135.2, 130.3 (three carbons), 128.2, 127.6,
127.3, 127.0, 125.8 (two carbons), 86.2, 67.9, 48.3, 43.9,
34.0, 21.4, 14.0; MS m/z (rel. int.): 378 (1), 231 (43), 183
(91), 147 (100), 115 (14), 105 (40), 104 (12), 103 (11),
102 (10), 91 (39), 77 (24). Anal. calcd for C19H22OSSe:
C, 60.48; H, 5.88. Found: C, 60.56; H, 5.99%.
Minor diastereoisomer (distinct signals): H NMR: l
6.97 (dt, 1H, J=1.6, 7.5 Hz), 4.47 (q, 1H, J=7.0 Hz),
3.23 (dt, 1H, J=5.4, 10.7 Hz), 1.82 (s, 3H), 1.45 (d, 3H,
J=7.0 Hz); 13C NMR: l 147.0, 141.0, 136.7, 77.6, 72.6,
47.2, 44.2, 14.2.
3.11. 2-Ethyl-3-({2-[(1S)-1-(methylthio)ethyl]phenyl}-
seleno)tetrahydrofuran 6d
1
Oil; Major diastereoisomer: H NMR: l 7.51 (dd, 1H,
J=1.3, 7.8 Hz), 7.44 (dd, 1H, J=1.4, 7.8 Hz), 7.22 (dt,
1H, J=1.4, 7.8 Hz), 7.06 (dt, 1H, J=1.3, 7.8 Hz), 4.52
(q, 1H, J=7.0 Hz), 3.86–3.74 (m, 2H), 3.66 (ddd, 1H,
J=4.5, 6.2, 7.2 Hz), 3.34 (dt, 1H, J=6.2, 8.1 Hz),
2.36–2.25 (m, 1H), 1.98–1.90 (m, 1H), 1.81 (s, 3H),
1.52–1.3 (m, 2H), 1.49 (d, 3H, J=7.0 Hz), 0.84 (t, 3H,
1
Minor diastereoisomer (distinct signals): H NMR: l
4.10 (dt, 1H, J=7.2, 15.6 Hz), 3.63 (ddd, 1H, J=5.2,

M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
1499
J=7.4 Hz); 13C NMR: l 145.6, 134.9, 130.4, 128.1, 127.2,
127.0, 86.0, 66.6, 44.3, 43.9, 34.3, 27.2, 21.6, 14.0, 10.1;
MS m/z (rel. int.): 330 (5), 231 (68), 183 (100), 135 (3),
104 (10), 99 (9), 91 (8), 77 (7), 57 (9). Anal. calcd for
C15H22OSSe: C, 54.71; H, 6.73. Found: C, 54.89; H,
6.75%.
J=1.5, 7.7 Hz), 7.45 (dd, 1H, J=1.5, 7.7 Hz), 7.22 (dt,
1H, J=1.5, 7.7 Hz), 7.09–7.01 (m, 3H), 6.78 (t, 1H, J=7.3
Hz), 6.77 (d, 1H, J=8.0 Hz), 4.92–4.82 (m, 1H), 4.53 (q,
1H, J=7.0 Hz), 3.30 (dd, 1H, J=9.0, 15.7 Hz), 3.23 (dd,
1H, J=5.6, 12.3 Hz), 3.07 (dd, 1H, J=7.4, 12.3 Hz), 2.98
(dd, 1H, J=6.8, 15.7 Hz), 1.9 (s, 3H), 1.52 (d, 3H, J=7.0
Hz); 13C NMR: l 159.0, 145.2, 133.8, 130.3, 127.9, 127.8,
127.4, 127.0, 125.9, 124.8, 120.4, 109.3, 81.5, 43.9, 35.4,
33.2, 21.5, 14.0; MS m/z (rel. int.): 364 (17), 231 (67), 211
(3), 199 (5), 183 (100), 131 (21), 116 (4), 105 (15), 91 (14),
77 (14). Anal. calcd for C18H20OSSe: C, 59.51; H, 5.55.
Found: C, 59.42; H, 5.39%.
Minor diastereoisomer (distinct signals): 1H NMR: l 7.45
(dd, 1H, J=1.5, 7.8 Hz), 3.36 (dt, 1H, J=6.2, 8.1 Hz),
1.88 (s, 3H), 1.48 (d, 3H, J=7.0 Hz), 0.88 (t, 3H, J=7.4
Hz); 13C NMR: l 135.0, 130.2, 128.2, 85.6, 44.0, 34.5,
27.3, 21.7, 14.1, 10.2.
3.12. 2-[({2-[(1S)-1-(Methylthio)ethyl]phenyl}seleno)-
Minor diastereoisomer (distinct signals): 1H NMR: l 6.69
(d, 1H, J=8.0 Hz), 4.54 (q, 1H, J=7.0 Hz), 3.28 (dd, 1H,
J=5.5, 12.3 Hz), 3.02 (dd, 1H, J=7.8, 12.3 Hz), 3.0 (dd,
1H, J=6.7, 15.7 Hz), 1.53 (d, 3H, J=7.0 Hz); 13C NMR:
l 133.7, 130.2, 81.4, 33.1.
methyl]-2-phenyltetrahydrofuran 6e
1
Oil; Major diastereoisomer: H NMR: l 7.50–7.44 (m,
4H), 7.37–7.32 (m, 2H), 7.29–7.21 (m, 2H), 7.09 (dt, 1H,
J=1.4, 7.8 Hz), 4.59 (q, 1H, J=7.0 Hz), 4.07 (q, 1H,
J=7.6 Hz), 3.94 (dt, 1H, J=5.7, 7.8 Hz), 3.46 (d, 1H,
J=11.8 Hz), 3.35 (d, 1H, J=11.8 Hz), 2.42 (dt, 1H,
J=8.2, 12.8 Hz), 2.30 (ddd, 1H, J=5.1, 7.8, 12.8 Hz),
2.11–2.01 (m, 1H), 1.91 (s, 3H), 1.91–1.8 (m, 1H), 1.56
(d, 3H, J=7.0 Hz); 13C NMR: l 146.2, 145.4, 134.0, 132.8,
128.6 (two carbons), 127.8, 127.7, 127.4, 127.2, 125.6 (two
carbons), 86.5, 68.7, 44.3, 42.7, 38.1, 26.4, 22.2, 14.6; MS
m/z (rel. int.): 392 (9), 231 (8), 183 (20), 147 (100), 105
(23), 91 (19), 77 (10). Anal. calcd for C20H24OSSe: C,
61.38; H, 6.18. Found: C, 61.46; H, 6.36%.
3.15. 4-({2-[(1S)-1-(Methylthio)ethyl]phenyl}seleno)-
5-phenyldihydrofuran-2(3H)-one 8a
1
Oil; Major diastereoisomer: H NMR: l 7.48 (dd, 1H,
J=1.5, 7.8 Hz), 7.45–7.22 (m, 7H), 7.12 (dt, 1H, J=
1.5, 7.8 Hz), 5.42 (d, 1H, J=6.2 Hz), 4.52 (q, 1H,
J=7.0 Hz), 3.82 (ddd, 1H, J=6.2, 7.4, 8.2 Hz), 3.09
(dd, 1H, J=8.2, 18.0 Hz), 2.71 (dd, 1H, J=7.4, 18.0
Hz), 1.96 (s, 3H), 1.52 (d, 3H, J=7.0 Hz); 13C NMR: l
174.5, 146.4, 137.2, 136.3, 129.2, 128.7 (two carbons),
128.6, 128.4, 127.6, 127.3 125.5 (two carbons), 86.1,
43.9, 42.9, 35.7, 20.9, 13.8; MS m/z (rel. int.): 392 (1),
231 (72), 183 (100), 160 (14), 131 (3), 115 (16), 105 (16),
91 (20), 77 (23). Anal. calcd for C19H20O2SSe: C, 58.32;
H, 5.15. Found: C, 58.55; H, 5.45%.
Minor diastereoisomer (distinct signals): 1H NMR: l 4.54
(q, 1H, J=7.0 Hz), 4.08 (q, 1H, J=7.6 Hz), 3.95 (dt, 1H,
J=5.7, 7.8 Hz), 2.43 (dt, 1H, J=8.2, 12.8 Hz), 1.95 (s,
3H), 1.52 (d, 3H, J=7.0 Hz); 13C NMR: l 134.3, 132.7,
128.5, 127.9, 127.3, 127.1, 42.9, 38.2, 22.1.
1
3.13. 2-[({2-[(1S)-1-(Methylthio)ethyl]phenyl}seleno)-
Minor diastereoisomer (distinct signals): H NMR: l
methyl]tetrahydrofuran 6f
5.45 (d, 1H, J=6.2 Hz), 4.54 (q, 1H, J=7.0 Hz), 3.84
(ddd, 1H, J=6.2, 7.4, 8.2 Hz), 3.08 (dd, 1H, J=8.2,
18.0 Hz), 2.72 (dd, 1H, J=7.4, 18.0 Hz), 1.9 (s, 3H),
1.56 (d, 3H, J=7.0 Hz); 13C NMR: l 146.5, 137.4,
136.1, 85.7, 44.1, 42.7, 36.3, 21.2, 14.0.
1
Oil; Major diastereoisomer: H NMR: l 7.46 (dd, 1H,
J=1.3, 7.8 Hz), 7.4 (dd, 1H, J=1.5, 7.8 Hz), 7.16 (dt,
1H, J=1.3, 7.8 Hz), 7.03 (dt, 1H, J=1.5, 7.8 Hz), 4.5 (q,
1H, J=7.0 Hz), 3.98 (quint., 1H, J=6.7 Hz), 3.81 (dt,
1H, J=6.9, 8.0 Hz), 3.66 (dt, 1H, J=6.4, 8.0 Hz), 2.99
(dd, 1H, J=5.9, 11.9 Hz), 2.88 (dd, 1H, J=6.7, 11.9 Hz),
2.05–1.9 (m, 1H), 1.9–1.78 (m, 2H), 1.86 (s, 3H), 1.6–1.5
(m, 1H), 1.48 (d, 3H, J=7.0 Hz); 13C NMR: l 144.9,
133.2, 131.1, 127.4, 127.3, 126.9, 78.1, 68.2, 43.8, 33.5,
31.5, 25.8, 21.6, 14.1; MS m/z (rel. int.): 316 (22), 231 (59),
183 (100), 157 (3), 135 (3), 116 (3), 115 (3), 104 (11), 103
(11), 102 (12), 91 (11), 77 (8), 61 (4). Anal. calcd for
C14H20OSSe: C, 53.34; H, 6.39. Found: C, 53.55; H,
6.18%.
3.16. 3,3-Dimethyl-4-({2-[(1S)-1-(methylthio)ethyl]-
phenyl}seleno)-5-phenyldihydrofuran-2(3H)-one 8b
1
Oil; Major diastereoisomer: H NMR: l 7.5–7.25 (m,
6H), 7.16 (dt, 1H, J=1.2, 7.7 Hz), 7.10 (dd, 1H, J=1.2,
7.7 Hz), 6.87 (dt, 1H, J=1.2, 7.7 Hz), 5.31 (d, 1H,
J=10.6 Hz), 4.28 (q, 1H, J=7.0 Hz), 3.48 (d, 1H,
J=10.6 Hz), 1.89 (s, 3H), 1.42 (s, 3H), 1.39 (s, 3H),
1.32 (d, 3H, J=7.0 Hz); 13C NMR: l 179.0, 145.4,
136.3, 135.8, 129.0, 128.6, 128.3 (two carbons), 127.3,
127.1, 127.0 (two carbons), 126.7, 84.2, 59.8, 43.6, 29.6,
22.9, 21.4, 20.8, 13.6. Anal. calcd for C21H24O2SSe: C,
60.14; H, 5.77. Found: C, 60.36; H, 5.99%.
Minor diastereoisomer (distinct signals): 1H NMR: l 4.49
(q, 1H, J=7.0 Hz), 3.97 (quint., 1H, J=6.5 Hz), 3.01 (dd,
1H, J=5.8, 11.8 Hz), 2.86 (dd, 1H, J=6.8, 11.8 Hz); 13
NMR: l 144.8, 133.1, 78.0, 33.4.
C
1
Minor diastereoisomer (distinct signals): H NMR: l
3.14. 2-[({2-[(1S)-1-(Methylthio)ethyl]phenyl}seleno)-
7.18 (dt, 1H, J=1.3, 7.8 Hz), 6.79 (dt, 1H, J=1.3, 7.8
Hz), 6.69 (dd, 1H, J=1.3, 7.8 Hz), 4.49 (q, 1H, J=7.0
Hz), 3.44 (d, 1H, J=10.6 Hz), 1.82 (s, 3H), 1.52 (d, 3H,
J=7.0 Hz); 13C NMR: l 83.5, 60.1, 43.8, 21.6, 21.1.
methyl]-2,3-dihydro-1-benzofuran 6g
1
Oil; Major diastereoisomer: H NMR: l 7.53 (dd, 1H,

1500
M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
1
3.17. 5-Ethyl-4-({2-[(1S)-1-(methylthio)ethyl]phenyl}-
seleno)dihydrofuran-2(3H)-one 8c
Minor diastereoisomer (distinct signals): H NMR: l
7.46 (dd, 1H, J=1.4, 7.8 Hz), 7.27 (dt, 1H, J=1.3, 7.8
Hz), 7.11 (dt, 1H, J=1.4, 7.8 Hz), 4.48 (q, 1H, J=7.0
Hz), 3.51 (d, 1H, J=12.8 Hz), 3.46 (d, 1H, J=12.8 Hz),
1.96 (s, 3H), 1.55 (d, 3H, J=7.0 Hz); 13C NMR: l
134.3, 128.6, 128.1, 127.9, 127.5, 126.8, 41.4, 33.8, 29.7,
21.3.
1
Oil; Major diastereoisomer: H NMR: l 7.58 (dd, 1H,
J=1.4, 7.8 Hz), 7.52 (dd, 1H, J=1.4, 7.8 Hz), 7.4 (dt,
1H, J=1.4, 7.8 Hz), 7.19 (dt, 1H, J=1.4, 7.8 Hz), 4.57
(q, 1H, J=6.9 Hz), 4.38 (ddd, 1H, J=4.3, 6.7, 7.7 Hz),
3.63 (ddd, 1H, J=6.7, 8.0, 8.5 Hz), 2.99 (dd, 1H,
J=8.5, 18.1 Hz), 2.62 (dd, 1H, J=8.0, 18.1 Hz), 1.99
(s, 3H), 1.8–1.61 (m, 2H), 1.60 (d, 3H, J=6.9 Hz), 0.98
(t, 3H, J=7.4 Hz); 13C NMR: l 174.6, 146.6, 136.3,
129.4, 128.3, 127.8, 127.5, 87.4, 44.1, 39.2, 36.3, 27.1,
21.3, 14.0, 9.7; MS m/z (rel. int.): 344 (1), 231 (62), 183
(100), 104 (11), 91 (9), 77 (7). Anal. calcd for
C15H20O2SSe: C, 52.48; H, 5.87. Found: C, 52.47; H,
5.95%.
3.20. 1-Acetyl-3-({2-[(1S)-1-(methylthio)ethyl]phenyl}-
seleno)-2-phenylpyrrolidine 12a
1
Oil; Major diastereoisomer: H NMR: l 7.62 (dd, 1H,
J=1.4, 7.7 Hz), 7.54 (dt, 1H, J=1.5, 7.7 Hz), 7.4–7.18
(m, 5H), 7.15–7.0 (m, 2H), 4.43–4.38 (m, 1H), 4.30 (q,
1H, J=7.0 Hz), 4.03–3.77 (m, 3H), 2.4–2.23 (m, 1H),
2.1–1.9 (m, 1H), 1.98 (s, 3H), 1.80 (s, 3H), 1.58 (d, 3H,
J=7.0 Hz); 13C NMR: l 170.6, 146.9, 141.7, 136.3,
130.5, 129.4 (two carbons), 129.0, 128.2, 128.1, 127.8,
125.8 (two carbons), 68.9, 50.5, 46.4, 44.6, 28.5, 22.9,
21.8, 14.5. Anal. calcd for C21H25NOSSe: C, 60.29; H,
6.02; N, 3.35. Found: C, 60.15; H, 5.98; N, 3.36%.
1
Minor diastereoisomer (distinct signals): H NMR: l
7.55 (dd, 1H, J=1.4, 7.8 Hz), 7.53 (dd, 1H, J=1.4, 7.8
Hz), 3.65 (ddd, 1H, J=6.7, 8.0, 8.5 Hz), 2.95 (dd, 1H,
J=8.5, 18.1 Hz), 1.59 (d, 3H, J=6.9 Hz), 1.01 (t, 3H,
J=7.4 Hz); 13C NMR: l 86.8, 36.7, 21.4.
1
Minor diastereoisomer (distinct signals): H NMR: l
5.23–5.19 (m, 1H), 4.31 (q, 1H, J=7.0 Hz), 2.2 (s, 3H),
1.97 (s, 3H); 13C NMR: l 169.8, 146.6, 141.6, 136.0,
129.2, 127.6, 125.7, 67.0, 48.8, 47.7, 44.5, 29.9, 23.0,
21.9, 14.4.
3.18. 5-Methyl-4-({2-[(1S)-1-(methylthio)ethyl]phenyl}-
seleno)dihydrofuran-2(3H)-one 8d
1
Oil; Major diastereoisomer: H NMR: l 7.59 (dd, 1H,
J=1.3, 7.7 Hz), 7.52 (dd, 1H, J=1.3, 7.7 Hz), 7.38 (dt,
1H, J=1.3, 7.6 Hz), 7.19 (dt, 1H, J=1.3, 7.6 Hz),
4.6–4.5 (m, 2H), 3.55 (ddd, 1H, J=7.3, 8.3, 9.1 Hz), 3.0
(dd, 1H, J=8.3, 17.9 Hz), 2.61 (dd, 1H, J=9.1, 17.9
Hz), 1.99 (s, 3H), 1.6 (d, 3H, J=7.0 Hz), 1.36 (d, 3H,
J=6.3 Hz); 13C NMR: l 174.5, 146.5, 136.4, 129.4,
128.3, 127.8, 127.5, 82.6, 44.1, 41.5, 36.4, 21.3, 19.6,
14.0; MS m/z (rel. int.): 330 (1), 231 (61), 183 (100), 104
(11), 103 (10), 91 (9), 77 (7). Anal. calcd for
C14H18O2SSe: C, 51.07; H, 5.51. Found: C, 49.99; H,
5.41%.
3.21. 1-Acetyl-2-[({2-[(1S)-1-(methylthio)ethyl]phenyl}-
seleno)methyl]-2-phenylpyrrolidine 12b
1
Oil; Major diastereoisomer: H NMR: l 7.58 (dd, 1H,
J=1.4, 7.8 Hz), 7.42 (dd, 1H, J=1.6, 7.8 Hz), 7.25–
7.08 (m, 6H), 7.06 (dt, 1H, J=1.6, 7.8 Hz), 4.58 (q, 1H,
J=7.0 Hz), 4.45 (d, 1H, J=11.4 Hz), 3.73–3.67 (m,
1H), 3.60 (ddd, 1H, J=6.6, 9.9, 10.8 Hz), 3.58 (d, 1H,
J=11.4 Hz), 2.50 (dt, 1H, J=6.8, 12.4 Hz), 2.11 (s,
3H), 2.0–1.9 (m, 1H), 1.88 (s, 3H), 1.8–1.6 (m, 2H), 1.51
(d, 3H, J=7.0 Hz); 13C NMR: l 169.9, 145.7, 144.6,
134.7, 132.3, 128.8 (two carbons), 128.1, 127.9, 127.4,
127.1, 125.6 (two carbons), 71.2, 51.3, 44.4, 40.7, 39.7,
24.5, 22.2, 22.0, 14.6. Anal. calcd for C22H27NOSSe: C,
61.11; H, 6.29; N, 3.24. Found: C, 61.23; H, 6.33; N,
3.11%.
1
Minor diastereoisomer (distinct signals): H NMR: l
7.58 (dd, 1H, J=1.3, 7.7 Hz), 7.53 (dd, 1H, J=1.4, 7.8
Hz), 3.56 (ddd, 1H, J=7.3, 8.3, 9.1 Hz), 2.95 (dd, 1H,
J=8.1, 18.0 Hz), 2.65 (dd, 1H, J=8.9, 18.0), 1.98 (s,
3H), 1.59 (d, 3H, J=7.0 Hz), 1.43 (d, 3H, J=6.3 Hz);
13C NMR: l 82.0, 36.8, 21.5, 14.1.
1
Minor diastereoisomer (distinct signals): H NMR: l
7.55 (dd, 1H, J=1.4, 7.8 Hz), 7.43 (dd, 1H, J=1.6, 7.8
Hz), 4.44 (d, 1H, J=11.2 Hz), 3.54 (d, 1H, J=11.2 Hz),
2.57 (dt, 1H, J=6.7, 12.3 Hz), 2.1 (s, 3H), 1.9 (s, 3H),
1.50 (d, 3H, J=7.0 Hz); 13C NMR: l 144.5, 134.4,
129.2, 128.0, 125.5, 71.0, 50.6, 44.2, 40.8, 39.8, 24.4,
22.3, 22.1.
3.19. 5-[({2-[(1S)-1-(Methylthio)ethyl]phenyl}seleno)-
methyl]-5-phenyldihydrofuran-2(3H)-one 8e
1
Oil; Major diastereoisomer: H NMR: l 7.5 (dd, 1H,
J=1.3, 7.8 Hz), 7.45 (dd, 1H, J=1.4, 7.8 Hz), 7.44–7.3
(m, 5H), 7.28 (dt, 1H, J=1.3, 7.8 Hz), 7.12 (dt, 1H,
J=1.4, 7.8 Hz), 4.53 (q, 1H, J=7.0 Hz), 3.5 (d, 1H,
J=12.8 Hz), 3.45 (d, 1H, J=12.8 Hz), 2.75–2.6 (m,
2H), 2.6–2.4 (m, 2H), 1.94 (s, 3H), 1.58 (d, 3H, J=7.0
Hz); 13C NMR: l 175.7, 145.1, 142.2, 134.1, 131.2,
128.6 (two carbons), 128.2, 128.0, 127.6, 127.0, 124.7
(two carbons), 88.1, 44.0, 41.2, 33.6, 28.9, 21.4, 14.0;
MS m/z (rel. int.): 406 (1), 231 (72), 183 (100), 161 (15),
115 (8), 105 (17), 104 (9), 103 (11), 102 (11), 91 (34), 77
(17). Anal. calcd for C20H22O2SSe: C, 59.26; H, 5.47.
Found: C, 59.45; H, 5.55%.
3.22. 1-Hydroxy-4-({2-[(1S)-1-(methylthio)ethyl]phenyl}-
seleno)-5-phenylpyrrolidin-2-one 15a
1
Oil; Major diastereoisomer: H NMR: l 7.48–7.36 (m,
2H), 7.35–7.24 (m, 5H), 7.15–7.0 (m, 3H), 4.73 (d, 1H,
J=5.1 Hz), 4.47 (q, 1H, J=7.0 Hz), 3.51 (ddd, 1H,
J=5.1, 5.8, 8.7 Hz), 2.98 (dd, 1H, J=8.7, 17.6 Hz),
2.55 (dd, 1H, J=5.8, 17.6 Hz), 1.84 (s, 3H), 1.49 (d,
3H, J=7.0 Hz); 13C NMR: l 169.4, 146.3, 137.6, 136.1,
129.5, 129.3, 128.8 (two carbons), 128.5, 127.6, 127.3,

M. Tiecco et al. / Tetrahedron: Asymmetry 12 (2001) 1493–1502
1501
126.4 (two carbons), 70.6, 43.9, 39.2, 35.4, 21.2, 13.8.
3.26. (5R)-5-Ethylfuran-2(5H)-one 9a
Anal. calcd for C19H21NO2SSe: C, 56.16; H, 5.21; N,
3.45. Found: C, 56.09; H, 5.14; N, 3.31%.
E.e.=78%; [h]2D9=−70.0 (c 2.26, CH2Cl2).
1
Minor diastereoisomer (distinct signals): H NMR: l
3.27. (5R)-5-Methylfuran-2(5H)-one 9b
E.e.=52%; [h]2D6=−61.2 (c 0.7, CHCl3).
4.77 (d, 1H, J=5.2 Hz), 3.55 (ddd, 1H, J=5.2, 5.8, 8.7
Hz), 2.53 (dd, 1H, J=5.8, 17.6 Hz), 1.82 (s, 3H), 1.46
(d, 3H, J=7.0 Hz); 13C NMR: l 70.2, 44.2, 38.7, 35.5,
21.5, 14.1.
3.28. Deselenylation by reductive cleavage of
selenolactones 8a and 8e
3.23. 1-Hydroxy-3,3-dimethyl-4-({2-[(1S)-1-(methylthio)-
ethyl]phenyl}seleno)-5-phenylpyrrolidin-2-one 15b
A catalytic amount of AIBN and triphenyltin hydride
(0.9 mmol) were added to a solution of the selenolac-
tone 8a or 8e (0.3 mmol) in refluxing benzene under
nitrogen. The reaction was stirred under reflux for 2 h
and, after removal of the solvent under reduced pres-
sure, the residue was purified by chromatography on
silica gel (CH2Cl2:petroleum ether=4:1 for 10a and
CH2Cl2 for 10b). Physical and spectral data of 10a8 and
10b7,21 are in good agreement with those already
described in the literature. Specific rotations are
reported below.
1
Oil; Major diastereoisomer: H NMR: l 9.5 (br s, 1H),
7.4–7.2 (m, 6H), 7.15 (dt, 1H, J=1.3, 7.8 Hz), 7.06 (dd,
1H, J=1.3, 7.8 Hz), 6.85 (dt, 1H, J=1.3, 7.8 Hz), 4.74
(d, 1H, J=9.5 Hz), 4.3 (q, 1H, J=7.0 Hz), 3.24 (d, 1H,
J=9.5 Hz), 1.88 (s, 3H), 1.36 (d, 3H, J=7.0 Hz), 1.34
(s, 3H), 1.29 (s, 3H); 13C NMR: l 174.7, 145.6, 135.9,
135.4, 129.9, 128.7, 128.6, 128.5 (two carbons), 127.6
(two carbons), 127.3, 126.8, 68.9, 58.3, 43.8, 38.5, 23.7,
21.8, 21.2, 13.9. Anal. calcd for C21H25NO2SSe: C,
58.07; H, 5.80; N, 3.22. Found: C, 58.00; H, 5.67; N,
3.02%.
3.29. (5S)-5-Phenyldihydrofuran-2(3H)-one 10a
E.e.=90%; [h]2D9=−24.8 (c 1.0, CHCl3).
1
Minor diastereoisomer (distinct signals): H NMR: l
4.75 (d, 1H, J=9.5 Hz); 13C NMR: l 145.3, 136.3, 68.4,
43.2, 21.9, 21.5.
3.30. (5R)-5-Methylphenyldihydrofuran-2(3H)-one 10b
E.e.=78%; [h]2D9=+32.4 (c 0.25, CHCl3).
3.24. 5-Ethyl-4-({2-[(1S)-1-(methylthio)ethyl]phenyl}-
seleno)dihydrofuran-2(3H)-one oxime 16
1
Oil; Major diastereoisomer: H NMR: l 8.5 (br s, 1H),
7.55 (dd, 1H, J=1.4, 7.7 Hz), 7.49 (dd, 1H, J=1.4, 7.7
Hz), 7.33 (dt, 1H, J=1.4, 7.7 Hz), 7.14 (dd, 1H, J=1.4,
7.7 Hz), 4.56 (q, 1H, J=7.0 Hz), 4.38–4.30 (m, 1H),
3.54–3.46 (m, 1H), 3.08 (dd, 1H, J=7.9, 16.7 Hz), 2.69
(dd, 1H, J=8.2, 16.7 Hz), 1.9 (s, 3H), 1.85–1.45 (m,
2H), 1.55 (d, 3H, J=7.0 Hz), 0.95 (t, 3H, J=7.4 Hz);
13C NMR: l 157.8, 146.4, 136.2, 129.2, 128.9, 127.6,
127.3, 90.3, 44.1, 40.0, 34.2, 26.5, 21.4, 14.0, 9.7. Anal.
calcd for C15H21NO2SSe: C, 50.27; H, 5.91; N, 3.91.
Found: C, 50.17; H, 5.89; N, 3.90%.
Acknowledgements
Financial support from MURST, National Project
‘Stereoselezione in Sintesi Organica. Metodologie ed
Applicazioni’, the University of Perugia, Progetti di
Ateneo, and CNR, Rome, is gratefully acknowledged.
References
1
Minor diastereoisomer (distinct signals): H NMR: l
8.1 (br s, 1H), 4.23–4.18 (m, 1H), 3.02 (dd, 1H, J=7.8,
16.8 Hz), 2.78 (dd, 1H, J=8.2, 16.8 Hz); 13C NMR: l
146.3, 136.0, 129.1, 128.4, 127.4, 89.8, 34.7, 26.6, 21.5.
1. Wirth, T. Tetrahedron 1999, 55, 1–28.
2. Tiecco, M. In Topics in Current Chemistry: Organosele-
nium Chemistry: Modern Developments in Organic Syn-
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