Synthesis of enantiomerically pure perhydrofuro[3,4-b]pyrans and perhydrofuro[3,4-b]furans

Article abstract of DOI:10.1016/j.tetasy.2004.05.009

Olefinic diols, prepared from (R)-(+)-2,2-dimethyl-1,3-dioxolane-4- carboxaldehyde via olefination and hydrolysis, were converted into enantiomerically pure hydroxy substituted tetrahydrofuran derivatives by cyclization using N-phenylselenophthalimide and BF₃. The PhSe group in the C-4 position of these tetrahydrofurans was then substituted by an allyl group using allyltributylstannane in the presence of AIBN. The selenium promoted cyclizations of the allyl tetrahydrofurans in which the OH and the allyl groups are trans to each other formed the enantiopure perhydrofuro[3,4-b]pyrans, while the cyclization of the allyl tetrahydrofurans in which the OH and the allyl groups are cis gave rise to the perhydrofuro[3,4-b]furans. These bicyclic products were finally deselenenylated with triphenyltin hydride and AIBN.

Full text of DOI:10.1016/j.tetasy.2004.05.009

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 15 (2004) 1949–1955
Synthesis of enantiomerically pure perhydrofuro[3,4-b]pyrans
and perhydrofuro[3,4-b]furans
Marcello Tiecco,* Lorenzo Testaferri, Luana Bagnoli, Raffaella Terlizzi,
Andrea Temperini, Francesca Marini, Claudio Santi and Catalina Scarponi
Dipartimento di Chimica e Tecnologia del Farmaco, Sezione di Chimica Organica, Universitꢀa di Perugia, I-06123 Perugia, Italy
Received 21 April 2004; accepted 7 May 2004
Abstract—Olefinic diols, prepared from (R)-(þ)-2,2-dimethyl-1,3-dioxolane-4-carboxaldehyde via olefination and hydrolysis, were
converted into enantiomerically pure hydroxy substituted tetrahydrofuran derivatives by cyclization using N-phenylselenophthal-
imide and BF3. The PhSe group in the C-4 position of these tetrahydrofurans was then substituted by an allyl group using allyl-
tributylstannane in the presence of AIBN. The selenium promoted cyclizations of the allyl tetrahydrofurans in which the OH and the
allyl groups are trans to each other formed the enantiopure perhydrofuro[3,4-b]pyrans, while the cyclization of the allyl tetra-
hydrofurans in which the OH and the allyl groups are cis gave rise to the perhydrofuro[3,4-b]furans. These bicyclic products were
finally deselenenylated with triphenyltin hydride and AIBN.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
SePh
OH
O
Ph
OH
Ph
The synthesis of heterocyclic compounds in an enan-
tiomerically enriched or pure form has recently assumed
a great importance and several research groups are
deeply involved in this problem. Among the various
ways in which an heterocyclic compound can be con-
structed, a very convenient procedure involves the use of
the readily available and very versatile organoselenium
reagents. In fact, selenium promoted cyclizations of
alkenes containing internal nucleophiles in an appro-
priate position provide an easy access to a wide variety
of heterocycles.1–3 In order to effect the asymmetric
synthesis of heterocyclic compounds these cyclization
reactions were promoted by electrophilic reagents gen-
erated from several types of enantiomerically pure di-
selenides.4–13 Using this procedure we have recently
reported the synthesis of several heterocycles using two
extremely efficient sulfur containing chiral nonracemic
diselenides.14–18 We have also described an alternative
approach using achiral phenylselenium reagents and
enantiomerically pure substrates.19;20 In Scheme 1 the
reaction sequence employed to effect the synthesis of
enantiopure substituted tetrahydrofurans starting from
Ph
Ph
Ph
O
O
O
O
SePh
Ph
OH
Ph
Ph
SePh
Scheme 1.
commercially available epoxides is reported.21 The
reaction of epoxides with phenylselenolate anions
afforded hydroxyalkyl phenyl selenides. The PhSe group
was then substituted by an allyl group and the reaction
of these allyl derivatives with electrophilic phenylsele-
nium reagents afforded two enantiomerically pure tet-
rahydrofurans, which were separated and finally
subjected to reductive deselenylation.
This general procedure can find other interesting syn-
thetic applications and it can be employed to effect the
synthesis of more complex molecules. We report in this
paper that, starting from (R)-(þ)-2,2-dimethyl-1,3-di-
oxolane-4-carboxaldehyde, by means of very simple
conversions and of two electrophilic selenium promoted
* Corresponding author. Tel.: +39-075-5855100; fax: +39-075-58551-
16; e-mail: tiecco@unipg.it
0957-4166/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.05.009

1950
M. Tiecco et al. / Tetrahedron: Asymmetry 15 (2004) 1949–1955
cyclizations the two bicyclic furan derivatives, tetrahy-
drofuro[3,4-b]pyrans and tetrahydrofuro[3,4-b]furans
can be easily obtained as pure enantiomers.
obtained in an enantiomerically pure form. Phenylse-
lenenyl chloride promoted 5-endo-trig cyclization of the
racemic allyl alcohol 5 has already been described by
Landais et al.24;25 A mixture of 8 and 9, in the ratio of
28:72, was obtained.
The proposed stereochemistry of these tetrahydrofurans
was confirmed by the results of NOESY experiments.
The configuration of the carbon atoms in the 3-positions
was obviously unchanged with respect to those of the
starting diols 4 and 5. As far as the absolute configu-
ration of the carbon atoms in position 5 is concerned, it
was observed that it presented strong dipolar interac-
tions with the proton in position 3 in the cases of
compounds 6 and 8 and with the proton of the OH
groups in compounds 7 and 9. Thus, the OH and the Ph
groups are cis in 6 and 8 and trans in compounds 7 and
9. In all the four tetrahydrofurans, the configurations of
the carbons in the 4-positions can be assigned on the
basis of the fact that the ring closure reaction is a ste-
reospecific trans-addition. These attributions were also
confirmed by the NOESY experiments. These stereo-
chemical assignments were also unambiguously con-
firmed by the structures of the compounds obtained by
the reductive deselenenylation reactions indicated in
Scheme 4. In fact, under standard conditions (Ph3SnH
and AIBN), the same deselenenylated product 10 was
obtained from both the tetrahydrofurans 6 and 8, while
the tetrahydrofurans 7 and 9 gave the deselenenylated
product 11. As demonstrated by GC–MS analysis on
chiral column, both 10 and 11 were obviously enantio-
merically pure compounds. Compounds 1024;25 and 1125
have already been obtained by Landais et al.
2. Results and discussion
The alkenes necessary for the ring closure reactions were
prepared by reacting the phosphorus ylide deriving from
triphenyl benzyl phosphonium bromide with the com-
mercially available (R)-(þ)-2,2-dimethyl-1,3-dioxolane-
4-carboxaldehyde 1. A mixture of the two geometrical
isomers 2 and 3 was obtained from this reaction
(Scheme 2). The two cis- and trans-isomers were easily
separated by column chromatography and separately
treated with 1 N hydrochloric acid and THF. The two
olefinic diols 4 and 5 were thus obtained.22 The absolute
configuration of the trans-isomer 5 was confirmed by
comparison of its specific rotation with that reported in
the literature.23
Ph
O
O
O
-
+ .
P CH Ph Br
2
+
Ph
3
Ph
H
O
O
O
n-BuLi, THF
T = 0°C, 2h
2 (50%)
3 (20%)
1
O
1N HCl
THF
1N HCl
THF
HO
HO
Ph
Ph
OH
OH
4 (99%)
5 (98%)
Scheme 2.
SePh
Ph
HO
SePh
Ph
HO
HO
Ph3SnH, AIBN
Ph3SnH, AIBN
Both the olefinic diols 4 and 5 were converted into a
mixture of two enantiomerically pure tetrahydrofurans
using N-phenylselenophthalimide, as the electrophilic
selenenylating reagent, in the presence of BF3 as cata-
lyst.19;20 As indicated in Scheme 3 all the products derive
from an endo-cyclization reaction and are the result of a
stereospecific anti-addition. The reaction carried out on
the cis-olefin 4 gave a mixture of the two tetrahydrofu-
rans 6 and 7, whereas a mixture of the tetrahydrofurans
8 and 9 was obtained starting from the trans-olefin 5.
Compounds 6 and 7, as well as compounds 8 and 9 were
separated by column chromatography. Thus, all of the
four isomeric trisubstituted tetrahydrofurans could be
C6H6, 80°C, 1h
(75%)
C6H6, 80°C, 1h
(95%)
Ph
Ph
O
O
O
6
8
10
SePh
Ph
HO
SePh
Ph
HO
HO
Ph3SnH, AIBN
Ph3SnH, AIBN
C6H6, 80°C, 1h
(95%)
C6H6, 80°C, 1h
(85%)
O
O
O
7
11
9
Scheme 4.
Compounds 6–9 can be further functionalized by
replacing the PhSe group. By treatment with allyltribu-
tyltin and AIBN an allyl chain can be introduced in
position 4. As indicated in Scheme 5, in the case of the
tetrahydrofurans 6 or 8 this radical reaction afforded the
allyl derivative 12 as the sole reaction product. This
result can be explained assuming that in these com-
pounds the phenyl group in C-5 and hydroxyl group in
C-3, which are cis to each other, efficiently direct the
incoming allyl group towards the opposite face of the
molecule. Compound 12, in the racemic form, has been
already described by Landais et al.26
SePh
Ph
HO
SePh
Ph
HO
HO
3
.
N-PSP, BF Et
3
3
O
2
5
+
5
Ph
OH
CH Cl , 0°C, 1h
O
O
2
2
6 (10%)
4
7 (75%)
SePh
HO
SePh
HO
HO
Ph
N-PSP, BF Et
.
O
3
3
2
3
5
5
+
Ph
CH Cl , 0°C, 1h
Ph
2
2
O
O
OH
8 (28%)
9 (49%)
5
On the contrary, a mixture of the two diastereomeric
allyl derivatives 13 and 14 was obtained starting from
Scheme 3.

M. Tiecco et al. / Tetrahedron: Asymmetry 15 (2004) 1949–1955
1951
equatorial position, as reported in Scheme 7. On the
contrary, in the case of compound 14, in which the OH
group and the allyl chain are in cis, a 5-exo trig cycli-
zation took place and the reaction product was the
perhydrofuro[3,4-b]furan 17 (Scheme 7). This was
obtained as a 65:35 mixture of two diastereoisomers,
which could not be separated by column chromatogra-
phy. The bicyclic compounds 15, 16 and 17 were finally
submitted to reductive deselenenylation. As reported in
Scheme 7 these reactions gave the phenyl derivative 18,
19 and 20 in excellent yields.
SePh
Ph
HO
HO
4
O
6
HO
SnBu3
4
or
4
Ph
AIBN, C6H6, 80°C
O
SePh
Ph
12 (65% from 6)
(70% from 8)
O
8
Scheme 5.
the tetrahydrofuran 7; a mixture of the same two com-
pounds was also obtained starting from 9 (Scheme 6).
These two compounds were separated by column chro-
matography, and were therefore obtained as pure
enantiomers. The structures of the allyl tetrahydrofu-
rans 13 and 14 indicated in Scheme 6 were assigned on
the basis of the results of NOESY experiments. In
compound 13 a strong dipolar interaction was observed
between the proton in the 4-position and the proton in
the 5-position, indicating that the allyl and the phenyl
groups have a cis relationship. In compound 14 the
strong dipolar interaction was observed between the
protons in the 4- and in the 3-positions, indicating that
the allyl and the OH group have a cis relationship.
SePh
3
HO
HO
O
O
O
O
Ph3SnH, AIBN
C6H6, 80°C, 1h
N-PSP, BF3, Et2O
Ph CH Cl , 0°C, 1h
2
2
Ph
18 (80%)
O
O
Ph
15 (75%)
SePh
O
12
3
Ph3SnH, AIBN
C6H6, 80°C, 1h
N-PSP, BF3, Et2O
PhCH Cl , 0°C, 1h
2
2
O
Ph
O
Ph
16 (91%)
O
13
19 (86%)
SePh
Me
HO
O
O
Ph3SnH, AIBN
C6H6, 80°C, 1h
N-PSP, BF3, Et2O
SePh
Ph
HO
Ph CH Cl , 0°C, 1h
2
2
4
O
Ph
Ph
17 (82%)
O
O
O
7
or
HO
HO
14
20 (75%)
SnBu3
3
3
4
4
+
5
5
Ph
Ph
AIBN, C6H6, 80°C
Scheme 7.
O
O
SePh
Ph
HO
14 (28% from 7)
13 (25% from 7)
(20% from 9)
4
(23% from 9)
O
3. Conclusions
9
Starting from the commercially available (R)-(þ)-2,2-
dimethyl-1,3-dioxolane-4-carboxaldehyde 1, and using
very simple conversions promoted by organoselenium
reagents, the two bicyclic compounds perhydrofuro[3,4-b]-
pyrans and perhydrofuro[3,4-b]furans were synthesized.
All the steps of the synthetic sequence occurred easily
and with good chemical yields. The two furopyran
derivatives were isolated in an enantiomerically pure
form, whereas in the case of furofurans a mixture of two
enantiomerically pure diastereoisomers was obtained.
The two types of bicyclic compounds, which have been
described in this paper are present in several molecules
having interesting biological properties.27–29
Scheme 6.
In this way we have obtained three enantiomerically
pure 4-allyl-3-hydroxy-5-phenyl tetrahydrofurans, 12–
14, which are alkenes containing a nucleophilic OH
group in an appropriate position to give rise to elec-
trophilic selenium promoted cyclization reaction. These
ring closure reactions were effected in the usual way by
treatment with N-phenylselenophthalimide and BF3. As
indicated in Scheme 7, compounds 12 and 13, in which
the hydroxy group and the allyl chain are trans to each
other, gave rise to a 6-endo trig cyclization and the
enantiomerically pure perhydrofuro[3,4-b]pyrans 15 and
16, respectively, were obtained as single diastereoiso-
mers and in high yields. Because of the relative geometry
of the allyl and the OH groups the addition reaction was
forced to take place with an anti-Markovnikov orien-
tation. In compounds 15 and 16 the absolute configu-
rations of C-3 were assigned on the basis of their proton
NMR spectra. In both cases the proton in C-3 appeared
as a triplet of triplets with coupling constants of 11.7
and 4.5 Hz for compound 15 and of 11.7 and 3.9 Hz for
compound 16. The presence of the large coupling con-
stant clearly indicates that in both compounds the pro-
ton is axial and hence the PhSe group occupies an
4. Experimental
1
All new compounds were characterized by MS, H and
13C NMR spectroscopy. GC analyses and MS spectra
were carried out with an HP 6890 gas chromatograph
(25 m dimethyl silicone capillary column) equipped with
an HP 5973 Mass Selective Detector; for the ions con-
taining selenium only the peaks arising from the sele-
nium-80 isotope are given. GC chiral analyses and MS

1952
M. Tiecco et al. / Tetrahedron: Asymmetry 15 (2004) 1949–1955
spectra were carried out with an HP 5890 gas chro-
matograph (25 m Chirasildex capillary column) equip-
ped with an HP 5971 Mass Selective Detector. H and
136.2, 133.3, 128.5 (two carbons), 127.9, 126.7, 126.6
(two carbons), 109.4, 77.2, 69.5, 26.7, 25.9; MS m=z (rel
int.): 204 (26), 146 (20), 129 (63), 115 (65), 104 (100), 91
(17), 77 (12), 72 (57). Anal. Calcd for C13H16O2: C,
76.44; H, 7.90. Found: C, 76.40; H, 7.85.
1
13C NMR spectra were recorded at 400 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.
4.3. Hydrolysis of the protected diols22,23
To a solution of compounds 2 or 3 in THF a 1 N
solution of HCl was added and the reaction mixtures
were stirred for 30 min below 10 °C. The reaction mix-
tures were poured into a 10% solution of NaOH and
extracted with diethyl ether. The combined organic
layers were dried over sodium sulfate, filtered and
evaporated. Reaction yields of compounds 4 and 5 are
reported in Scheme 2. Physical and spectral data are
reported below.
4.1. Starting products
(R)-(þ)-2,2-Dimethyl-1,3-dioxolane-4-carboxaldehyde 1,
N-phenylselenophthalimide, triphenyltin hydride and
allyltributyltin were commercial products and were used
without further purification.
4.2. Conversion of the (R)-(+)-2,2-dimethyl-1,3-dioxo-
lane-4-carboxaldehyde into the olefinic protected diols 2
and 322
4.3.1. (2S,3Z)-4-Phenylbut-3-ene-1,2-diol, 4. Mp 70–
22
D
1
75 °C; ½aꢁ ¼ þ13:0 (c 1.39, CHCl3). H NMR: d 7.38–
7.15 (m, 5H), 6.60 (d, 1H, J ¼ 11:7 Hz), 5.61 (dd, 1H,
J ¼ 9:1, 11.7 Hz), 4.70–4.60 (m, 1H), 3.72–3.62 (m, 1H),
3.55 (dd, 1H, J ¼ 7:7, 11.4 Hz), 3.20 (br s, 2H); 13C
NMR: d 136.3, 133.0, 129.7, 128.7 (two carbons), 128.4
(two carbons), 127.5, 68.7, 66.1; MS m=z (rel int.): 146
(Mþꢀ18, 44), 131 (46), 117 (100), 103 (21), 91 (35), 77
(15), 65 (11), 51 (16). Anal. Calcd for C10H12O2: C,
73.15; H, 7.37. Found: C, 73.10; H, 7.44.
The white suspension of the Ph3(PhCH2)PþBrꢀ
(1.1 mmol) in THF (10 mL) became orange when n-BuLi
(1.1 mmol) was added dropwise at 0 °C. The tempera-
ture was allowed to raise to room temperature over a
30 min period and then (R)-(þ)-2,2-dimethyl-1,3-dioxo-
lane-4-carboxaldehyde was added. The suspension
immediately became yellow. The progress of the reac-
tion was monitored by TLC and GC–MS and stirring
was continued for 2 h. The reaction mixture was then
poured into water and extracted with diethyl ether. The
organic layer was dried over Na2SO4 and evaporated.
The isomers 2 and 3 were obtained as a 70:30 mixture of
Z- and E-isomers. These were isolated in a pure form
after column chromatography of the residue on silica gel
using a 1:9 mixture of diethyl ether and light petroleum
as eluent. The products obtained and the reaction yields
are reported in Scheme 2. Physical and spectral data are
reported below.
4.3.2. (2S,3E)-4-Phenylbut-3-ene-1,2-diol, 5. Mp 55–
32
D
57 °C; ½aꢁ ¼ þ33:7 (c 0.95, CHCl3).23 1H NMR: d 7.48–
7.18 (m, 5H), 6.72 (d, 1H, J ¼ 16:0 Hz), 6.21 (dd, 1H,
J ¼ 6:3, 16.0 Hz), 4.50–4.30 (m, 1H), 3.78 (dd, 1H,
J ¼ 3:5, 11.2 Hz), 3.63 (dd, 1H, J ¼ 7:4, 11.2 Hz), 2.98
(br s, 1H), 2.78 (br s, 1H); 13C NMR: d 136.3, 131.8,
128.5 (two carbons), 127.8, 127.6, 126.4 (two carbons),
73.2, 66.4; MS m=z (rel int.): 146 (Mþꢀ18, 49), 131 (50),
117 (100), 103 (24), 91 (40), 77 (22), 65 (14), 51 (18).
Anal. Calcd for C10H12O2: C, 73.15; H, 7.37. Found: C,
73.19; H, 7.40.
4.2.1. (4S)-2,2-Dimethyl-4-[(Z)-phenylethenyl]-1,3-dioxo-
30
D
1
lane, 2. Oil, ½aꢁ ¼ ꢀ41:6 (c 2.15, CHCl3). H NMR: d
4.4. General procedure for the cyclofunctionalization
reactions: synthesis of tetrahydrofurans, perhydro-
furo[3,4-b]pyrans and perhydrofuro[3,4-b]furans
7.40–7.20 (m, 5H), 6.72 (d, 1H, J ¼ 11:5 Hz), 5.70 (dd,
1H, J ¼ 8:9, 11.5 Hz), 4.92 (dddd, 1H, J ¼ 1:0, 6.1, 8.0,
8.9 Hz), 4.15 (dd, 1H, J ¼ 6:1, 8.1 Hz), 3.68 (dd, 1H,
J ¼ 8:0, 8.1 Hz), 1.50 (s, 3H), 1.41 (s, 3H); 13C NMR: d
136.1, 133.8, 129.3, 128.7 (two carbons), 128.3 (two
carbons), 127.5, 109.3, 72.4, 69.7, 26.9, 25.9; MS m=z (rel
int.): 204 (18), 174 (13), 146 (30), 129 (80), 115 (72), 104
(100), 91 (19), 77 (12), 72 (56). Anal. Calcd for
C13H16O2: C, 76.44; H, 7.90. Found: C, 76.39; H, 7.84.
To a solution of N-phenylselenophthalimide (1 mmol) in
dichloromethane (6 mL) compounds 4, 5, 12, 13 or 14
(1 mmol) were added at 0 °C. A catalytic amount of
BF3ÆEt2O was added dropwise. The temperature was
allowed to raise to room temperature over a 1 h period
and the progress of the reaction was monitored by TLC
and GC–MS. The reaction mixture was then poured
into a 5% aqueous solution of NaOH and extracted with
dichloromethane. The organic layer was dried over so-
dium sulfate, filtered and evaporated. The tetra-
hydrofurans 6, 7 and 8, 9 were separated by medium
pressure chromatography on a silica gel column (Merck,
LiChroprepâ Si60, 40–63 lm) using a 1:1 mixture of
diethyl ether and light petroleum as eluent. After col-
4.2.2. (4S)-2,2-Dimethyl-4-[(E)-phenylethenyl]-1,3-dioxo-
20
D
1
lane, 3. Oil, ½aꢁ ¼ þ53; 5 (c 1.45, CHCl3). H NMR: d
7.47–7.20 (m, 5H), 6.65 (d, 1H, J ¼ 15:8 Hz), 6.15 (dd,
1H, J ¼ 7:5, 15.8 Hz), 4.68 (dddd, 1H, J ¼ 0:9, 6.1, 7.5,
8.0 Hz), 4.16 (dd, 1H, J ¼ 6:1, 8.2 Hz), 3.69 (dd, 1H,
J ¼ 8:0, 8.2 Hz), 1.48 (s, 3H), 1.44 (s, 3H); 13C NMR: d

M. Tiecco et al. / Tetrahedron: Asymmetry 15 (2004) 1949–1955
1953
umn chromatography of the residue on silica gel using a
3:8 mixture of diethyl ether and light petroleum as elu-
ent, the perhydrofuro[3,4-b]pyrans 15 and 16 were ob-
tained in pure form, while the perhydrofuro[3,4-b]furans
17 were obtained as a 65:35 mixture of two diastereo-
isomers. The products obtained and the reaction yields
are reported in Schemes 3 and 7. Physical and spectral
data, including those of 8 and 9,24;25 are reported below.
105 (36), 91 (34), 77 (59), 51 (17). Anal. Calcd for
C16H16O2Se: C, 60.19; H, 5.05. Found: C, 60,21; H, 5.07.
4.4.5. (3R,4aR,5S,7aS)-5-Phenyl-3-(phenylseleno)hexa-
hydro-2H-furo[3,4-b]pyran,
15.
Mp
88–89 °C;
24
D
½aꢁ ¼ þ20:9 (c 2.91, CHCl3). 1H NMR: d 7.57–7.52 (m,
2H), 7.39–7.24 (m, 8H), 4.53 (d, 1H, J ¼ 10:5 Hz), 4.18
(t, 1H, J ¼ 7:1 Hz), 4.15 (ddd, 1H, J ¼ 1:5, 4.5,
11.7 Hz), 3.78 (dd, 1H, J ¼ 7:1, 9.7 Hz), 3.69 (ddd, 1H,
J ¼ 7:1, 9.7, 10.0 Hz), 3.60 (t, 1H, J ¼ 11:7 Hz), 3.19 (tt,
1H, J ¼ 4:5, 11.7 Hz), 2.34 (dddd, 1H, J ¼ 1:5, 3.3, 4.5,
12.0 Hz), 1.89 (dddd, 1H, J ¼ 3:3, 10.0, 10.5, 12.0 Hz),
1.60 (dt, 1H, J ¼ 11:7, 12.1 Hz); 13C NMR: d 140.6,
135.0 (two carbons), 129.1 (two carbons), 128.5 (two
carbons), 128.0, 127.8, 127.2, 125.6 (two carbons), 82.0,
80.9, 73.3, 68.6, 52.9, 38.4, 32.5; MS m=z (rel int.): 360
(49), 207 (58), 159 (41), 143 (33), 129 (45), 115 (32), 105
(47), 91 (100), 77 (56), 67 (26), 51 (21). Anal. Calcd for
C19H20O2Se: C, 63.51; H, 5.61. Found: C, 63.43; H, 5.68.
4.4.1. (3R,4R,5R)-5-Phenyl-4-(phenylseleno)tetrahydro-
29
D
furan-3-ol, 6. Oil, ½aꢁ ¼ þ4:8 (c 0.82, CHCl3). 1H
NMR: d 7.55–7.40 (m, 4H), 7.35–7.18 (m, 6H), 5.34 (d,
1H, J ¼ 8:7 Hz), 4.40 (dd, 1H, J ¼ 1:7, 9.8 Hz), 4.28–
4.23 (m, 1H), 4.21 (ddd, 1H, J ¼ 1:4, 4.5, 8.7 Hz), 3.98
(ddd, 1H, J ¼ 1:4, 3.5, 9.8 Hz), 2.89 (br s, 1H); 13C
NMR: d 140.2, 134.4 (two carbons), 129.8 (two car-
bons), 129.1, 128.5 (two carbons), 128.3 (two carbons),
127.7 (two carbons), 82.4, 74.2, 71.5, 57.0; MS m=z (rel
int.): 320 (30), 214 (13), 158 (100), 145 (62), 115 (26), 105
(31), 91 (34), 77 (55), 57 (18). Anal. Calcd for
C16H16O2Se: C, 60.19; H, 5.05. Found: C, 60.14; H, 4.98.
4.4.6. (3R,4aR,5R,7aS)-5-Phenyl-3-(phenylseleno)hexa-
21
D
hydro-2H-furo[3,4-b]pyran, 16. Oil, ½aꢁ ¼ ꢀ62:4 (c
1
1.03, CHCl3). H NMR: d 7.55–7.45 (m, 2H), 7.36–7.20
4.4.2. (3R,4S,5S)-5-Phenyl-4-(phenylseleno)tetrahydro-
(m, 6H), 7.20–7.10 (m, 2H) 5.20 (d, 1H, J ¼ 8:2 Hz),
4.34 (dd, 1H, J ¼ 6:9, 7.4 Hz), 4.07–4.03 (m, 1H), 3.71
(dd, 1H, J ¼ 7:4, 9.2 Hz), 3.62 (ddd, 1H, J ¼ 6:9, 9.2,
9.9 Hz), 3.37 (t, 1H, J ¼ 11:7 Hz), 3.32 (tt, 1H, J ¼ 3:9,
11.7 Hz), 2.37–2.29 (m, 2H), 1.10–0.85 (m, 1H); 13C
NMR: d 140.3, 134.5 (two carbons), 129.0 (two car-
bons), 128.1 (two carbons), 127.8, 127.7, 127.2, 125.2
(two carbons), 80.5, 77.9, 72.9, 69.0, 47.9, 39.0, 32.4; MS
m=z (rel int.): 360 (35), 254 (10), 159 (62), 141 (33), 129
(46), 115 (29), 97 (67), 91 (100), 77 (51), 67 (23), 51 (16).
Anal. Calcd for C19H20O2Se: C, 63.51; H, 5.61. Found:
C, 63.58; H, 5.65.
22
D
furan-3-ol, 7. Oil, ½aꢁ ¼ þ3:9 (c 1.07, CHCl3). 1H
NMR: d 7.49–7.30 (m, 8H), 7.28–7.18 (m, 2H), 5.53 (d,
1H, J ¼ 5:1 Hz), 4.64 (dd, 1H, J ¼ 4:5, 9.8 Hz), 4.59–
4.51 (m, 1H), 4.02 (d, 1H, J ¼ 5:1 Hz), 3.93 (dd, 1H,
J ¼ 1:7, 9.8 Hz), 2.01 (br s, 1H); 13C NMR: d 139.2 (two
carbons), 134.4 (two carbons), 129.6 (two carbons),
128.5 (two carbons), 128.3, 128.0, 126.4 (two carbons),
81.6, 78.8, 74.6, 53.4; MS m=z (rel int.): 320 (32), 214
(13), 184 (20), 163 (29), 158 (100), 145 (63), 128 (10), 115
(23), 105 (36), 91 (42), 77 (56), 57 (16). Anal. Calcd for
C16H16O2Se: C, 60.19; H, 5.05. Found: C, 60.07; H, 5.10.
4.4.3. (3R,4S,5R)-5-Phenyl-4-(phenylseleno)tetrahydro-
4.4.7. (3aS,4R,6aS)-4-Phenyl-2-[(phenylseleno)methyl]-
hexahydrofuro[3,4-b]furan, 17. Oil; Major diastereoiso-
mer: H NMR: d 7.55–7.50 (m, 2H), 7.23–7.09 (m, 8H),
31
D
furan-3-ol, 8. Oil, ½aꢁ ¼ þ6:5 (c 2.46, CHCl3). 1H
1
NMR: d 7.52–7.25 (m, 10H), 4.79 (d, 1H, J ¼ 7:0 Hz),
4.51–4.46 (m, 1H), 4.09 (dd, 1H, J ¼ 4:4, 9.8 Hz), 4.05
(ddd, 1H, J ¼ 1:0, 2.9, 9.8 Hz), 3.49 (ddd, 1H, J ¼ 1:0,
3.4, 7.0 Hz), 2.08 (d, 1H, J ¼ 5:7 Hz); 13C NMR: d 140.1
(two carbons), 134.9 (two carbons), 129.7 (two carbons),
128.9 (two carbons), 128.5 (two carbons), 126.5 (two
carbons), 86.0, 79.3, 74.5, 55.7; MS m=z (rel int.): 320
(27), 207 (18), 163 (28), 158 (100), 145 (83), 115 (28), 105
(35), 91 (34), 77 (56), 51 (22). Anal. Calcd for
C16H16O2Se: C, 60.19; H, 5.05. Found: C, 60.23; H, 5.08.
4.87 (ddd, 1H, J ¼ 3:0, 5.3, 7.0 Hz), 4.63 (d, 1H,
J ¼ 6:6 Hz), 4.48 (dddd, 1H, J ¼ 1:1, 5.6, 6.7, 9.3 Hz),
4.21 (dd, 1H, J ¼ 5:3, 10.2 Hz), 3.89 (dd, 1H, J ¼ 3:0,
10.2 Hz), 3.21 (dd, 1H, J ¼ 5:6, 12.3 Hz), 3.09 (dd, 1H,
J ¼ 6:7, 12.3 Hz), 2.95–2.87 (m, 1H), 2.18 (ddd, 1H
J ¼ 1:1, 5.2, 12.7 Hz), 1.88 (ddd, 1H, J ¼ 7:9, 9.3,
12.7 Hz); 13C NMR: d 141.1 (two carbons), 132.7 (two
carbons), 129.1 (two carbons), 128.5 (two carbons),
127.6, 127.0, 125.6 (two carbons), 85.9, 84.5, 78.3, 74.2,
52.6, 36.7, 32.1; MS m=z (rel int.): 360 (51), 203 (60), 189
(57), 173 (27), 157 (31), 143 (61), 129 (38), 117 (31), 115
(31), 105 (67), 91 (100), 77 (47). Anal. Calcd for
C19H20O2Se: C, 63.51; H, 5.61. Found: C, 63.53; H, 5.63.
4.4.4. (3R,4R,5S)-5-Phenyl-4-(phenylseleno)tetrahydro-
20
D
furan-3-ol, 9. Mp 65–66 °C; ½aꢁ ¼ þ70:1 (c 1.69,
1
CHCl3). H NMR: d 7.50–7.20 (m, 10H), 4.88 (d, 1H,
J ¼ 10:2 Hz), 4.45–4.39 (m, 1H), 4.32 (ddd, 1H, J ¼ 1:2,
4.3, 9.8 Hz), 4.08 (ddd, 1H, J ¼ 1:2, 1.8, 9.8 Hz), 3.48
(dd, 1H, J ¼ 4:7, 10.2 Hz), 2.91–2.88 (m, 1H); 13C
NMR: d 139.6 (two carbons), 133.8 (two carbons), 129.1
(two carbons), 128.3 (two carbons), 128.1, 127.8, 126.5
(two carbons), 83.1, 74.2, 72.0, 59.0; MS m=z (rel int.):
320 (27), 207 (14), 163 (30), 158 (100), 145 (85), 115 (30),
Minor diastereoisomer (distinct signals): 1H NMR: d
4.81 (d, 1H, J ¼ 5:8 Hz), 4.68 (ddd, 1H, J ¼ 2:1, 5.0,
7.0 Hz), 4.26 (dddd, 1H, J ¼ 5:8, 6.5, 8.7, 8.9 Hz), 4.12
(dd, 1H, J ¼ 5:0, 10.3 Hz), 4.04 (dd, 1H, J ¼ 2:1,
10.3 Hz), 3.28 (dd, 1H, J ¼ 5:8, 12.3 Hz), 3.19 (dd, 1H,
J ¼ 6:5, 12.3 Hz), 2.40 (ddd, 1H, J ¼ 6:4, 8.9, 12.7 Hz),
1.76 (ddd, 1H, J ¼ 5:3, 8.7, 12.7 Hz); 13C NMR: d 141.0,

1954
M. Tiecco et al. / Tetrahedron: Asymmetry 15 (2004) 1949–1955
128.4 (two carbons), 127.5, 126.9, 125.7 (two carbons),
86.5, 85.5, 81.6, 73.1, 52.5, 36.6; MS m=z (rel int.): 360
(30), 203 (100), 189 (20), 173 (42), 157 (29), 143 (74), 128
(32), 115 (32), 105 (77), 91 (93), 77 (43), 51 (14).
7.15 (m, 2H) 5.22 (d, 1H, J ¼ 8:5 Hz), 4.34 (dd, 1H,
J ¼ 6:8, 7.4 Hz), 3.98 (ddt, 1H, J ¼ 1:2, 4.9, 11.5 Hz),
3.74 (dd, 1H, J ¼ 7:4, 9.7 Hz), 3.55 (ddd, 1H, J ¼ 6:8,
9.7, 10.5 Hz), 3.32 (ddd, 1H, J ¼ 2:8, 11.5, 12.0 Hz), 2.18
(dddd, 1H, J ¼ 3:3, 8.5, 10.5, 12.4 Hz), 1.93–1.86 (m,
1H), 1.72–1.60 (m, 1H), 1.58–1.51 (m, 1H), 0.84 (dq, 1H,
J ¼ 4:2, 12.4 Hz); 13C NMR: d 141.0, 128.0 (two car-
bons), 127.0, 125.4 (two carbons), 81.1, 78.3, 69.3, 68.2,
46.2, 25.5, 25.0; MS m=z (rel int.): 204 (69), 173 (11), 159
(25), 145 (79), 129 (11), 119 (29), 105 (39), 98 (41), 91
(47), 83 (100), 77 (32), 69 (19), 55 (19). Anal. Calcd for
C13H16O2: C, 76.44; H, 7.90. Found: C, 77.36; H, 7.81.
4.5. Reductive deselenenylation. General procedure
Triphenyltin hydride (0.5 mmol) and a catalytic amount
of AIBN were added to a solution of compounds 6, 7, 8,
9, 15, 16 or 17 (0.3 mmol) in dry benzene (3 mL) and the
mixture was stirred and refluxed for 1 h. The solvent was
then removed under reduced pressure. The tetra-
hydrofurans 10 and 11 were obtained in a pure form
after column chromatography of the residue on a silica
gel column using a 4:6 mixture of diethyl ether and light
petroleum as eluent. The perhydrofuro[3,4-b]pyrans 18
and 19, which were present as single enantiomers, and
the perhydrofuro[3,4-b]furans 20, which was a mixture
of two diastereoisomers, were purified by column
chromatography on silica gel using a 2:8 mixture of
diethyl ether and light petroleum as eluent. The reaction
yields are reported in Schemes 4 and 7. Physical and
spectral data of racemic form of the compound 10 are
reported in the literature,26 physical and spectral data of
the other compounds are reported below.
4.5.5.
(3aS,4R,6aS)-2-Methyl-4-phenylhexahydrofuro-
1
[3,4-b]furan, 20. Oil; major diastereoisomer: H NMR:
d 7.40–7.20 (m, 5H), 4.85 (ddd, 1H, J ¼ 3:5, 5.6, 7.3 Hz),
4.64 (d, 1H, J ¼ 6:8 Hz), 4.36 (ddq, 1H, J ¼ 4:9, 5.9,
9.9 Hz), 4.22 (dd, 1H, J ¼ 5:6, 10.1 Hz), 3.86 (dd, 1H,
J ¼ 3:5, 10.1 Hz), 2.93–2.87 (m, 1H), 2.08 (ddd, 1H,
J ¼ 1:2, 4.9, 12.6 Hz), 1.70 (ddd, 1H, J ¼ 7:8, 9.9,
12.6 Hz), 1.34 (d, 3H, J ¼ 5:9 Hz); 13C NMR: d 141.9,
128.9 (two carbons), 128.0, 126.1 (two carbons), 86.5,
84.3, 75.0, 74.7, 53.3, 39.0, 20.5; MS m/z (rel int.): 204
(35), 203 (21), 174 (18), 162 (65), 145 (38), 131 (100), 115
(31), 105 (53), 91 (56), 83 (34), 77 (43), 69 (33), 54 (35).
Anal. Calcd for C13H16O2: C, 76.44; H, 7.90. Found: C,
76.43; H, 7.95.
4.5.1. (3S,5S)-5-Phenyltetrahydrofuran-3-ol, 10.26 Oil,
22
D
½aꢁ ¼ ꢀ15:0 (c 0.26, CHCl3).
Minor diastereoisomer (distinct signals): 1H NMR: d
4.78 (d, 1H, J ¼ 5:7 Hz), 4.63 (ddd, 1H, J ¼ 2:1, 4.9,
7.4 Hz), 4.14 (dd, 1H, J ¼ 4:9, 10.2 Hz), 4.10 (dquint,
1H, J ¼ 6:0, 9.3 Hz), 4.04 (dd, 1H, J ¼ 2:1, 10.2 Hz),
2.34 (ddd, 1H, J ¼ 6:0, 8.9, 12.4 Hz), 1.55 (ddd, 1H,
J ¼ 5:8, 9.3, 12.4 Hz), 1.33 (d, 1H, J ¼ 6:0 Hz); 13C
NMR: d 141.5, 128.8 (two carbons), 127.9, 126.2 (two
carbons), 87.4, 85.6, 79.1, 73.5, 53.4, 39.2, 20.9; MS m=z
(rel int.): 204 (18), 203 (22), 162 (100), 145 (30), 131 (52),
115 (16), 105 (35), 91 (28), 83 (20), 77 (24), 69 (16), 54
(20).
4.5.2. (3S,5R)-5-Phenyltetrahydrofuran-3-ol, 11. Oil,
21
D
½aꢁ ¼ þ34:6 (c 2.04, CHCl3). 1H NMR: d 7.45–7.20 (m,
5H), 5.18 (dd, 1H, J ¼ 5:7, 10.1 Hz), 4.63–4.58 (m, 1H),
4.24 (dd, 1H, J ¼ 4:3, 9.8 Hz), 3.91 (ddd, 1H, J ¼ 1:1,
1.8, 9.8 Hz), 2.46 (br s, 1H), 2.34 (ddt, 1H, J ¼ 1:2, 5.7,
13.3 Hz), 1.96 (ddd, 1H, J ¼ 5:2, 10.1, 13.3 Hz); 13C
NMR: d 142.1, 128.4 (two carbons), 127.4, 125.6 (two
carbons), 79.5, 76.2, 72.6, 44.4; MS m=z (rel int.): 164
(74), 163 (90), 146 (15), 120 (34), 115 (16), 105 (100), 92
(64), 91 (51), 79 (43), 77 (44), 51 (16). Anal. Calcd for
C10H12O2: C, 73.15; H, 7.37. Found: C, 73.12; H, 7.40.
4.6. Radical allylation. General procedure
Allyltributylstannane (7 mmol) and a catalytic amount
of AIBN were added to a solution of the tetrahydrofu-
rans 6, 7, 8 or 9 (1 mmol) in refluxing dry benzene (8 mL)
under nitrogen. The progress of the reaction was mon-
itored by TLC and 1H NMR. After 1 h a second portion
of allyltributylstannane (7 mmol) and a catalytic amount
of AIBN were then added. The reaction mixtures were
stirred for 3 h and then directly evaporated under vac-
uum. Starting from compounds 6 or 8 the single com-
pound 12 was obtained in a pure form after column
chromatography of the residue on a silica gel column
using a 6:4 mixture of diethyl ether and light petroleum
as eluent. Starting from compound 7 and 9, compounds
13 and 14, respectively, were obtained. Their purifica-
tion required a first column chromatography on silica
gel using a 6:4 mixture of diethyl ether and light petro-
leum as eluent and a second medium pressure chroma-
tography on a silica gel column (Merck, LiChroprepâ
Si60, 40–63 lm) using a 6:4 mixture of diethyl ether and
4.5.3. (4aR,5S,7aS)-5-Phenyl-hexahydro-2H-furo[3,4-b]-
25
D
pyran, 18. Oil, ½aꢁ ¼ ꢀ5:0 (c 1.11, CHCl3). 1H NMR: d
7.41–7.27 (m, 5H), 4.55 (d, 1H, J ¼ 10:2 Hz), 4.22 (t,
1H, J ¼ 7:1 Hz), 4.11 (ddt, 1H, J ¼ 1:3, 4.5, 11.5 Hz),
3.84 (dd, 1H, J ¼ 7:1, 9.7 Hz), 3.69 (dt, 1H, J ¼ 7:1,
9.7 Hz), 3.59 (dt, 1H, J ¼ 3:1, 11.5 Hz), 2.10–1.99 (m,
1H), 1.80–1.45 (m, 4H); 13C NMR: d 141.7, 128.8 (two
carbons), 128.1, 126.1 (two carbons), 83.2, 81.9, 69.3,
69.2, 51.9, 25.6, 25.4; MS m=z (rel int.): 204 (100), 173
(12), 159 (25), 145 (83), 131 (12), 119 (23), 115 (26), 105
(34), 98 (32), 91 (35), 83 (76), 77 (20), 69 (12), 55 (12).
Anal. Calcd for C13H16O2: C, 76.44; H, 7.90. Found: C,
77.38; H, 7.87.
4.5.4. (4aR,5R,7aS)-5-Phenyl-hexahydro-2H-furo[3,4-b]-
23
D
pyran, 19. Mp 69–71 °C; ½aꢁ ¼ ꢀ31:9 (c 2.97, CHCl3).
1H NMR: d 7.38–7.32 (m, 2H), 7.29–7.24 (m, 1H), 7.20–

M. Tiecco et al. / Tetrahedron: Asymmetry 15 (2004) 1949–1955
1955
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5. Deziel, R.; Malenfant, E. J. Org. Chem. 1995, 60, 4660–
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light petroleum as eluent. Reaction yields are reported in
Schemes 5 and 6. Physical and spectral data of the
racemic form of compound 12 are reported in the lit-
erature,26 physical and spectral data of other com-
pounds are reported below.
4.6.1. (3S,4S,5S)-4-Allyl-5-phenyltetrahydrofuran-3-ol,
24
D
12.26 Oil, ½aꢁ ¼ þ4:3 (c 1.51, CHCl3).
4.6.2. (3S,4S,5R)-4-Allyl-5-phenyltetrahydrofuran-3-ol,
24
D
13. Oil, ½aꢁ ¼ þ83:8 (c 0.97, CHCl3). 1H NMR: d
7.43–7.15 (m, 5H), 5.65 (dddd, 1H, J ¼ 5:4, 8.4, 10.2,
17.0 Hz), 5.34 (d, 1H, J ¼ 5:5 Hz), 5.02–4.78 (m, 2H),
4.38 (ddd, 1H, J ¼ 1:8, 2.1, 4.9 Hz), 4.34 (dd, 1H,
J ¼ 4:9, 9.7 Hz), 3.86 (dd, 1H, J ¼ 2:1, 9.7 Hz), 2.36–
2.29 (m, 1H), 2.06 (br s, 1H), 1.74–1.67 (m, 1H), 1.61–
1.51 (m, 1H); 13C NMR: d 139.2, 136.3, 128.1 (two
carbons), 127.0, 126.0 (two carbons), 116.4, 81.7, 75.8,
74.2, 51.5, 31.7; MS m=z (rel int.): 204 (5), 203 (6), 187
(7), 175 (56), 162 (69), 145 (50), 133 (8), 128 (10), 115
(15), 107 (100), 91 (24), 79 (40), 77 (22), 57 (15). Anal.
Calcd for C13H16O2: C, 76.44; H, 7.90. Found: C, 76.39;
H, 7.88.
8. Takada, H.; Nishibayashi, Y.; Uemura, S. J. Chem. Soc.,
Perkin Trans. 1 1999, 1511–1516.
9. Fujita, K.; Murata, K.; Iwaoka, M.; Tomoda, S. J. Chem.
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10. Fujita, K.; Murata, K.; Iwaoka, M.; Tomoda, S. Tetra-
hedron 1997, 53, 2029–2048.
11. Deziel, R.; Malenfant, E.; Thibault, C.; Frechette, S.;
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13. Wirth, T. Angew. Chem., Int. Ed. 2000, 39, 3740–3749.
14. Tiecco, M.; Testaferri, L.; Bagnoli, L.; Marini, F.;
Temperini, A.; Tomassini, C.; Santi, C. Tetrahedron Lett.
2000, 41, 3241–3245.
15. Tiecco, M.; Testaferri, L.; Santi, C.; Tomassini, C.;
Marini, F.; Bagnoli, L.; Temperini, A. Chem. Eur. J.
2002, 8, 1118–1124.
16. Tiecco, M.; Testaferri, L.; Marini, F.; Sternativo, S.;
Bagnoli, L.; Santi, C.; Temperini, A. Tetrahedron: Asym-
metry 2001, 12, 1493–1502.
17. Tiecco, M.; Testaferri, L.; Marini, F.; Sternativo, S.;
Bagnoli, L.; Santi, C.; Temperini, A. Tetrahedron: Asym-
metry 2001, 12, 3053–3059.
18. Tiecco, M.; Testaferri, L.; Bagnoli, L.; Purgatorio, V.;
Temperini, A.; Marini, F.; Santi, C. Tetrahedron: Asym-
metry 2001, 12, 3297–3304.
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C.; Bagnoli, L.; Temperini, A. Tetrahedron: Asymmetry
2003, 14, 1095–1102.
20. Tiecco, M.; Testaferri, L.; Marini, F.; Sternativo, S.; Santi,
C.; Bagnoli, L.; Temperini, A. Tetrahedron: Asymmetry
2003, 14, 2651–2657.
4.6.3. (3S,4R,5R)-4-Allyl-5-phenyltetrahydrofuran-3-ol,
24
D
14. Oil, ½aꢁ ¼ ꢀ36:1 (c 0.77, CHCl3). 1H NMR d
7.48–7.10 (m, 5H), 5.78 (dddd, 1H, J ¼ 5:7, 7.9, 10.1,
17.1 Hz), 5.20–4.99 (m, 2H), 4.63 (d, 1H, J ¼ 10:0 Hz),
4.48 (ddd, 1H, J ¼ 1:2, 4.1, 4.5 Hz), 4.32 (dd, 1H,
J ¼ 4:1, 10.0 Hz), 3.96 (dd, 1H, J ¼ 1:2, 10.0 Hz), 2.42–
2.30 (m, 1H), 2.16–2.08 (m, 1H), 2.07–1.99 (m, 1H), 1.92
(br s, 1H); 13C NMR: d 141.1, 136.3, 128.4 (two car-
bons), 127.8, 126.3 (two carbons), 116.2, 83.9, 75.8, 72.9,
52.8, 29.0; MS m=z (rel int.): 204 (4), 203 (4), 175 (55),
162 (67), 145 (52), 128 (12), 115 (19), 107 (100), 105 (27),
91 (27) 79 (44), 77 (24), 57 (16). Anal. Calcd for
C13H16O2: C, 76.44; H, 7.90. Found: C, 76.51; H, 7.96.
21. Tiecco, M.; Testaferri, L.; Bagnoli, L.; Purgatorio, V.;
Temperini, A.; Marini, F.; Santi, C. Tetrahedron: Asym-
metry 2004, 15, 405–412.
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1999, 40, 3581–3582.
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26. Andrey, O.; Ducry, L.; Landais, Y.; Planchenault, D.;
Weber, V. Tetrahedron 1997, 53, 4339–4352.
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2781.
Acknowledgements
Financial support from MIUR, National Project ‘Ste-
reoselezione in Sintesi Organica. Metodologie ed Ap-
plicazioni’
and
FIRB
Project
‘Progettazione,
Preparazione e Valutazione Biologica e Farmacologica
di Nuove Molecole Organiche Quali Potenziali Farmaci
Innovativi’, from Consorzio CINMPIS and from the
University of Perugia, Progetti di Ateneo, is gratefully
acknowledged.
References and notes
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Perkin Trans. 1 2000, 3706–3713.
1. Tiecco, M. Electrophilic Selenium, Selenocyclizations. In
Topics in Current Chemistry: Organoselenium Chemistry:
29. Sharma, G. W. M.; Gopinath, T. Tetrahedron 2003, 59,
6521–6530.