Thermal rearrangement of {[2-(arylmethylene)cyclopropyl]methyl}(phenyl) sulfanes and selanes

Article abstract of DOI:10.1021/jo7021636

(Chemical Equation Presented) {[2-(Arylmethylene)cyclopropyl]methyl} (phenyl)sulfanes and {[2-(arylmethylene)cyclopropyl]methyl}-(phenyl)selanes, generated in situ from 2-(arylmethylene)cyclopropylcarbinols with sodium benzenethiolate and sodium benzenese

Full text of DOI:10.1021/jo7021636

Thermal Rearrangement of
{[2-(Arylmethylene)cyclopropyl]methyl}(phenyl)sulfanes and Selanes
Guo-Qiang Tian, Jia Li, and Min Shi*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese
Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China
mshi@mail.sioc.ac.cn
ReceiVed October 4, 2007
{[2-(Arylmethylene)cyclopropyl]methyl}(phenyl)sulfanes and {[2-(arylmethylene)cyclopropyl]methyl}-
(phenyl)selanes, generated in situ from 2-(arylmethylene)cyclopropylcarbinols with sodium benzenethiolate
and sodium benzeneselenolate, could undergo rearrangement upon heating to afford (2-arylmethylidenebut-
3-enyl)(phenyl)sulfanes and (2-arylmethylidenebut-3-enyl)(phenyl)selanes, in good to excellent yields
as mixtures of E- and Z-isomers, respectively. A radical rearrangement was proposed on the basis of
control experiments for this process.
Introduction
1, methylenecyclopropanes bearing an additional hydroxymethyl
group, could undergo different reactions from MCPs under mild
conditions as demonstrated by our group.4 Herein, we wish to
report a radical rearrangement of {[2-(arylmethylene)cyclopropyl]-
methyl}(phenyl)sulfanes 2 and {[2-(arylmethylene)cyclopropyl]-
methyl}(phenyl)selanes 4, derived from the reaction of mesy-
lated1withsodiumbenzenethiolateandsodiumbenzeneselenolate,
affording (2-arylmethylidenebut-3-enyl)(phenyl)sulfanes 3 and
(2-arylmethylidenebut-3-enyl)(phenyl) selanes 5 in good to
excellent yields, respectively.
Methylenecyclopropanes (MCPs) are highly strained but
readily accessible and stable molecules that serve as useful
building blocks in organic synthesis. MCPs undergo a variety
of ring-opening reactions because the relief of ring strain
provides a potent thermodynamic driving force.1 In the past
decade, transition-metal (such as Pd, Rh, Ru, and Pt)-catalyzed
reactions of MCPs with various reactants have been studied
systematically by chemists.2 Recently, we and others found that
Lewis acid was also powerful catalyst for MCPs to undergo
ring-opening and cycloaddition reactions with heteroatom-
containing molecules.3 2-(Arylmethylene)cyclopropylcarbinols
Results and Discussion
At the beginning of our investigation, we attempted to prepare
(E)-[(2-benzylidenecyclopropyl)methyl](phenyl)sulfane 2a from
(E)-2-(phenylmethylene)cyclopropylcarbinol 1a via a substitu-
tion of its mesylated product with sodium benzenethiolate at
(1) For recent reviews, see: (a) Nakamura, I.; Yamamoto, Y. AdV. Synth.
Catal. 2002, 344, 111. (b) Brandi, A.; Cicchi, S.; Cordero, F. M.; Goti, A.
Chem. ReV. 2003, 103, 1213. (c) Nakamura, E.; Yamago, S. Acc. Chem.
Res. 2002, 35, 867.
10.1021/jo7021636 CCC: $40.75 © 2008 American Chemical Society
Published on Web 12/23/2007
J. Org. Chem. 2008, 73, 673-677
673

Tian et al.
TABLE 1. Screening of the Reaction Conditions of 1a to Afford
room temperature. However, we found that besides the desired
product 2a, a ring-opening concomitant, (2-benzylidenebut-3-
enyl)(phenyl)sulfane 3a, was also observed. This interesting
observation stimulated us to examine this transformation in
detail. These examinations using (E)-2-(phenylmethylene)-
cyclopropylcarbinol (E)-1a as the substrate by converting (E)-
1a to its mesylated intermediate through treatment with meth-
anesulfonyl chloride and followed by the addition of sodium
benzenethiolate as an nucleophile in a one-pot manner in a
variety of solvents and under various conditions were aimed at
determining the optimal conditions, and the results of these
experiments are summarized in Table 1. We found that the in
situ generated mesylated intermediate of 1a reacted with sodium
benzenethiolate in tetrahydrofuran (THF) at room temperature
for 48 h to produce 2a and 3a (mixtures of E- and Z-isomers,
E/Z ) 3/1) in 41% and 25% yields, respectively (Table 1, entry
1). Upon heating under reflux in THF, the yield of 3a was
improved to 67% along with 11% of 2a (Table 1, entry 2).
Benzenethiol was not a suitable nucleophile for the formation
of 2a and 3a (Table 1, entry 3). Products 2a and 3a could also
be formed in good total yields in dichloromethane (DCM) and
1,2-dichloroethane (DCE) under reflux, but in lower selectivities
(Table 1, entries 4-6). Using acetonitrile as a solvent gave lower
total yields of 2a and 3a even upon heating under reflux (Table
1, entry 7). In refluxing toluene, 3a was obtained exclusively
in 41% yield within 6 h (Table 1, entry 8). The addition of
water and sodium borohydride in THF dramatically increased
the efficiency of the conversion of mesylated intermediate of
1a to 2a and 3a at room temperature (20 °C), presumably
because sodium borohydride could transform 1,2-diphenyldis-
ulfane (PhSSPh), derived from the oxidation of sodium ben-
zenethiolate during the reaction, to sodium benzenethiolate
again5 and water could increase the solubility of sodium
benzenethiolate in the reaction mixture (Table 1, entry 9). It
should be noted that in this case, 2a was obtained as a major
product. In addition, under these reaction conditions, 2.0 equiv
of sodium benzenethiolate could give 2a and 3a in 50% and
6% yields, respectively (Table 1, entry 10).
2a and 3a
yieldb (%)
3a (E/Z)
entrya
solvent
temp (°C)
time (h)
2a
41
11
trace
51
21
25
19
1
THF
THF
THF
DCE
DCE
DCM
MeCN
PhMe
THF
20
70
20
20
90
50
90
120
20
20
48
24
24
20
14
12
24
6
25 (3:1)
67 (3:1)
trace
<10 (3:1)
53 (3:1)
43 (3:1)
34 (3:1)
41 (3:1)
10 (3:1)
6 (3:1)
2
3c
4
5
6
7
8
9d
10d,e
1
10
85
50
THF
a All reactions were carried out with 1a (0.30 mmol), MsCl (0.36 mmol),
Et3N (0.36 mmol), and PhSNa (0.90 mmol) in 2.0 mL of solvent under
argon atmosphere except otherwise specified. b Isolated yields based on 1a.
c PhSH was used as the nucleophile. d Run with 20 equiv of H2O and 2
equiv of NaBH4 added. e Run with 2.0 equiv of PhSNa added.
SCHEME 1. Thermal-Induced Quantitative Transformation
of 2a to 3a
Sequential investigation revealed that compound 2a isolated
as pure form by preparative TLC plates could be transformed
quantitatively to the ring-opening product 3a under reflux in
THF for 4 h, indicating that compound 3a was derived from
product 2a via a rearrangement rather than the attack of sodium
benzenethiolate to the mesylated intermediate (Scheme 1).
Therefore, the preparation of 3a can be simplified by heating
mixtures of 2a and 3a, synthesized under the conditions shown
in entry 9 of Table 1, under reflux in THF within 4 h, affording
3a as the sole product.
Following the simplified procedure, we next carried out the
reactions with various 2-(arylmethylene)cyclopropylcarbinols 1
to examine the generality of this transformation. The results
are summarized in Table 2. As can be seen from Table 2, for
2-(arylmethylene)cyclopropylcarbinols (E)-1c, (E)-1e, and (E)-
1h having electron-donating groups on the benzene ring, the
corresponding ring-opening products 3c, 3e, and 3h were
obtained in good to excellent yields (75-91%) as mixtures of
E- and Z-isomers (Table 2, entries 3, 5, and 8). As for (E)-1h
(2) (a) Camacho, D. H.; Nakamura, I.; Saito, S.; Yamamoto, Y. Angew.
Chem., Int. Ed. 1999, 38, 3365. (b) Camacho, D. H.; Nakamura, I.; Saito,
S.; Yamamoto, Y. J. Org. Chem. 2001, 66, 270. (c) Nakamura, I.; Itagaki,
H.; Yamamoto, Y. J. Org. Chem. 1998, 63, 6458. (d) Nu¨ske, H.; Notlemeyer,
M.; de Meijere, A. Angew. Chem., Int. Ed. 2001, 40, 3411. (e) Bra¨se, S.;
de Meijere, A. Angew. Chem., Int. Ed. 1995, 34, 2545. (f) Tsukada, N.;
Hibuya, A.; Nakamura, I.; Yamamoto, Y. J. Am. Chem. Soc. 1997, 119,
8123. (g) Inoue, Y.; Hibi, T.; Sataka, H.; Hashimoto, H. Chem. Commun.
1979, 982. (h) Binger, P.; Germer, A. Chem. Ber. 1981, 114, 3325. (i)
Nakamura, I.; Oh, B. H.; Saito, S.; Yamamoto, Y. Angew. Chem., Int. Ed.
2001, 40, 1298. (j) Oh, B. H.; Nakamura, I.; Saito, S.; Yamamoto, Y.
Tetrahedron Lett. 2001, 42, 6203. (k) Bessmertnykh, A. G.; Blinov, K. A.;
Grishin, Y. K.; Donskaya, N. A.; Tveritinova, E. V.; Yur’eva, N. M.;
Beletskaya, I. P. J. Org. Chem. 1997, 62, 6069. (l) Lautens, M.; Meyer, C.;
Lorenz, A. J. Am. Chem. Soc. 1996, 118, 10676. (m) Ishiyama, T.; Momota,
S.; Miyaura, N. Synlett 1999, 1790. (n) Suginome, M.; Matsuda, T.; Ito, Y.
J. Am. Chem. Soc. 2000, 122, 11015. (o) Chatani, N.; Takaya, H.; Hanafusa,
T. Tetrahedron Lett. 1988, 29, 3979. (p) Ma, S.-M.; Zhang, J.-L. J. Am.
Chem. Soc. 2003, 125, 12386. (q) Shi, M.; Wang, B.-Y.; Huang, J.-W. J.
Org. Chem. 2005, 70, 5606. (r) Shi, M.; Liu, L.-P.; Tang, J. J. Am. Chem.
Soc. 2006, 128, 7430. (s) Nakamura, I.; Nemoto, T.; Yamamoto, Y.; de
Meijere, A. Angew. Chem., Int. Ed. 2006, 45, 5176. For the metal-catalyzed
cocyclization reactions of MCPs with unsaturated carbon bonds, please see
the reviews: (t) Lautens, M.; Klute, W.; Tam, W. Chem. ReV. 1996, 96,
49. (u) Ohta, T.; Takaya, H. In ComprehensiVe Organic Chemistry; Trost,
B. M., Fleming, I., Paquette, L. A., Eds.; Pergamon Press: Oxford, England,
1991; Vol 5, pp 1185. (v) Binger, P.; Schmidt, T. In Methods of Organic
Chemistry, (Houben-Weyl); de Meijere, A., Ed.; Thieme, Stuttgart, Germany,
1997; Vol. E 17c, pp 2217. (w) Binger, P.; Buch, H. M. Top. Curr. Chem.
1987, 135, 77.
(3) Selected recent articles about Lewis acid-mediated reactions of
MCPs: (a) Shi, M.; Xu, B.; Huang, J.-W. Org. Lett. 2004, 6, 1175. (b)
Shi, M.; Shao, L.-X.; Xu, B. Org. Lett. 2003, 5, 579. (c) Shao, L.-X.; Xu,
B.; Huang, J.-W.; Shi, M. Chem. Eur. J. 2006, 12, 510. (d) Huang, J.-W.;
Shi, M. Synlett 2004, 2343. (e) Patient, L.; Berry, M. B.; Kilburn, J. D.
Tetrahedron Lett. 2003, 44, 1015. (f) Shi, M.; Xu, B. Org. Lett. 2002, 4,
2145. (g) Xu, B.; Shi, M. Org. Lett. 2003, 5, 1415. (h) Huang, X.; Zhou,
H.-W. Org. Lett. 2002, 4, 4419. (i) Huang, J.-W.; Shi, M. Tetrahedron
Lett. 2003, 44, 9343 and references cited therein.
(4) (a) Shao, L.-X.; Li, Y.-X.; Shi, M. Chem. Eur. J. 2007, 13, 862. (b)
Wang, B.-Y.; Huang, J.-W.; Liu, L.-P.; Shi, M. Synlett 2005, 421. (c) Shi,
M.; Wang, B.-Y. Synlett 2006, 3158. (d) Shi, M.; Tian, G.-Q. Tetrahedron
Lett. 2006, 47, 8059. (e) Tian, G.-Q.; Shi, M. Org. Lett. 2007, 9, 2405.
(5) Knapp, S.; Gibson, F. S. J. Org. Chem. 1992, 57, 4902.
674 J. Org. Chem., Vol. 73, No. 2, 2008

Thermal Rearrangement of Sulfanes and Selanes
TABLE 2. Transformation of 1 to the Ring-Opening Sulfanes 3
TABLE 3. Transformation of 1 to the Ring-Opening Selanes 5
yieldb (%)
yieldb (%)
entrya
R1/R2
C6H5/H, 1a
4-BrC6H4/H, 1b
4-MeC6H4/H, 1c
4-CIC6H4/H, 1d
4-MeOC6H4/H, 1e
4-FC6H4/H, 1f
time (h)
2
3 (E/Z)
entrya
R1/R2
C6H5/H, 1a
4-BrC6H4/H, 1b
4-MeC6H4/H, 1c
4-ClC6H4/H, 1d
4-MeOC6H4/H, 1e
4-FC6H4/H, 1f
time (h)
4
5 (E/Z)
1
2
3
4
5
6
7
8
9
4
3
7
20
8
15
4
3a, 96 (3:1)
3b, 92 (5:1)
3c, 75 (3:1)
3d, 53 (4;1)
3e, 81 (3:1)
3f, 37 (3:1)
3g, 93 (5:1)
3h, 91 (2:1)
3a, 94 (3:1)
1
2
3
4
5
6
7
8
9
1
3
2
2
2
12
2
0
1.5
2
5a, 97 (3:1)
5b, 74 (5:1)
5c, 92 (3:1)
5d, 99 (2;1)
5e, 96 (2:1)
5f, 89 (2:1)
5g, 88 (3:1)
5h, 87 (2:1)
5a, 75 (3:1)
5e, 96 (2:1)
2d, 42
2f, 61
2,4-Cl2C6H3/H, 1g
3,4,5-(MeO)3C6H2/H, 1h
H/C6H5, 1i
2,4-Cl2C6H3/H, 1g
3,4,5-(MeO)3C6H2/H, 1h
H/C6H5, 1i
c
8
a All reactions were carried out with 1 (0.30 mmol), MsCl (0.36 mmol),
and Et3N (0.36 mmol) in 2.0 mL of THF under argon atmosphere, then
PhSNa (0.90 mmol), H2O (6.00 mmol), and NaBH4 (0.90 mmol) were added
after the mixture was stirred for 20 min at room temperature. b Isolated
yields based on 1. c At room temperature.
10
H/4-MeOC6H4, 1j
a All reactions were carried out with 1 (0.30 mmol), MsCl (0.36 mmol),
and Et3N (0.36 mmol) in 2 mL of THF under argon atmosphere, then
(PhSe)2 (0.60 equiv), CH3OH (3.00 mmol) and NaBH4 (0.90 mmol) were
added after the mixture was stirred for 20 min at room temperature. b Total
isolated yields
bearing three strongly electron-donating groups on the benzene
ring, the reaction directly produced compound 3h in 91% yield
and the second step upon heating in THF is not required (Table
2, entry 8). As for 2-(arylmethylene)cyclopropylcarbinols (E)-
1d and (E)-1f having moderately electron-withdrawing groups
on the benzene ring, the corresponding ring-opening products
3d and 3f were obtained in lower yields (53% and 37%,
respectively) as mixtures of E- and Z-isomers along with
precursors 2d and 2f in moderate yields (42% and 61%),
respectively, even under prolonged reaction time (Table 2,
entries 4 and 6). These results indicate that electron-donating
groups on the benzene ring favor this rearrangement. As for
unsubstituted E-1a, p-bromosubstituted (E)-1b, and dichloro-
substituted (E)-1g, these substrates could undergo substitution
and rearrangement smoothly to afford products 3a, 3b, and 3g
in excellent yields (96%, 92%, and 93%) as mixtures of E- and
Z-isomers, respectively (Table 2, entries 1, 2, and 7). For (Z)-
2-(phenylmethylene)cyclopropylcarbinol, this reaction could also
take place smoothly to furnish the same product 3a as that from
(E)-1a as mixtures of E- and Z-isomers (Table 2, entry 9).
Similarly, the in situ generated selenides 4, which were
prepared via a substitution of mesylated intermediates of 1 by
sodium benzeneselenolate derived from 1,2-diphenyldiselane
with sodium borohyride and methanol,5 could also undergo the
same type of rearrangement to give the corresponding ring-
opening products 5 in good yields. The results are summarized
in Table 3. As can be seen from Table 3, the reactions proceeded
more smoothly than those of sulfides. As for 2-(arylmethylene)-
cyclopropylcarbinols 1, whether having electron-donating groups
or electron-withdrawing ones on the benzene ring, the ring-
opening products (2-arylmethylidenebut-3-enyl)(phenyl)selanes
5 were obtained in good to excellent yields within shorter
reaction time (Table 3, entries 1-7).6 As for 3,4,5-trimethoxy
groups substituted 1h, the substitution of mesylated intermediate
of 1h by sodium benzeneselenolate took place immediately to
produce product 5h in good yield at room temperature (20 °C),
TABLE 4. Effects of Heating Halide Derivatives from 1
entrya
Nu
time (h)
yieldb (%)
6
7
1
2
3
NaCl
LiBr
Nal
24
12
12
6i, 94
6j, 77
6m, 81c
7m, 14
a All reactions were carried out with 1a (0.30 mmol), MsCl (0.36 mmol),
Et3N (0.36 mmol), nucleophiles(0.90 mmol) and 2.0 mL of solvent under
argon atmosphere. b Isolated yields. c Mixtures of Z- and E-isomers (1:1).
and therefore the heating in THF was not required, suggesting
again that electron-donating groups on the benzene ring favor
this rearrangement (Table 3, entry 8). Z-2-(Arylmethylene)-
cyclopropylcarbinols could also produce the corresponding
rearrangement products in high yields (Table 3, entries 9 and
10).
Halide ions have been considered as good nucleophiles for
mesylated intermediate of 1. However, we found that the
corresponding chlorinated and brominated compounds 6i and
6j were formed without formation of the corresponding ring-
opening products 7 under the standard conditions (Table 3,
entries 1 and 2). As for sodium iodide, the expected iodide 7m
was obtained in 14% yield along with iodinated product 6m as
a major product, suggesting that the halogenated products 6
cannot undergo such rearrangement efficiently (Table 4, entries
1-3).
To ascertain the pathway of this rearrangement, compound
9 was synthesized by addition of methylmagnesium bromide
to compound 8 to label the hydroxylated carbon. Under the
optimal reaction conditions, compound 9 could be transformed
to the ring-opening product 10 with the newly formed carbon-
carbon double bond positioned on the labeled carbon (Scheme
2).
(6) Since compound 4 can be easily converted to product 5, we did not
isolate any compound 4 as pure form.
J. Org. Chem, Vol. 73, No. 2, 2008 675

Tian et al.
SCHEME 2. Transformation with Secondary Alcohol
SCHEME 5. Crossover Experiment Using 2a and 4d under
the Standard Conditions
SCHEME 6. A Radical Rearrangement Mechanism
Proposed for the Ring-Opening Transformation
SCHEME 3. Formation of 5a via a Radical Process
According to above results, a radical pair rearrangement
mechanism is outlined in Scheme 6. First, compound 2 or 4
undergoes thermal homolysis to produce radical pair A, which
delivers allylic radical pair B via a cyclopropane ring-opening
process.9 At this moment, (Z)-3 or (Z)-5 could be produced by
the recombination of radical pair B. On the other hands, allylic
radical pair C can be formed from radical pair B through allylic
rearrangement, which gives another allylic radical pair D via
rotation across the single bond. Subsequent similar allylic
rearrangement produces allylic radical pair E, which furnishes
the favored isomers (E)-3 or (E)-5 through recombination. The
selectivity may simply come from the more thermodynamically
stable E-isomers than Z-isomers owing to the steric factors. On
the other hand, an ionic process could also account for this
transformation and we could not exclude this mechanism at
present stage.
In conclusion, we have developed an interesting procedure
for the preparation of (2-arylmethylidenebut-3-enyl)(phenyl)-
sulfanes 3 and (2-arylmethylidenebut-3-enyl)(phenyl) selanes
5 from the reaction of 2-(arylmethylene)cyclopropylcarbinols
1 with sodium benzenethiolate and sodium benzeneselenolate
in good to excellent yields via simple operation under mild
conditions. A radical pair rearrangement mechanism accounting
for the cyclopropane ring-opening and allylic isomerization has
been proposed. Further studies regarding the mechanistic details
and scope of this process are in progress.
SCHEME 4. Control Experiment for This Radical
Transformation
Moreover, to further clarify the reaction mechanism, we
synthesized dithiocarbonic acid O-(2-benzylidene-cyclopropy-
lmethyl) ester S-methyl ester 11 for a control experiment since
this compound could readily undergo deoxygenation to form a
radical 12 initiated by 2,2′-azobisisobutyronitrile (AIBN) upon
heating (Scheme 3).7 Indeed, it was found that compound 5a
was produced in 30% yield as mixtures of E- and Z-isomers
when compound 11 was treated with 1,2-diphenyldiselane (3.0
equiv) and AIBN (5.0 mol %) under reflux in benzene for 2
days (Scheme 3). This result indicated that the transformation
of 2 or 4 to 3 or 5 might proceed via a radical process.8 It should
be noted here that the control experiment has confirmed that
this intramolecular radical rearrangement under the optimized
conditions was unaffected by the addition of the radical
inhibitors such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)
and 2,6-di-tert-butyl-4-methylphenol (BHT) (20 mol %), pre-
sumably because these radical inhibitors are unable to affect
such rapid intramolecular radical rearrangement (Scheme 4).
Another crossover experiment was performed using 2a and 4d
under the standard conditions. The result is presented in Scheme
5. It was found that the scrambling products were not formed
under the reaction conditions, suggesting again that this in-
tramolecular radical pair rearrangement is very fast.
Experimental Section
General Procedure for the Preparation of (2-Arylmeth-
ylidenebut-3-enyl)(phenyl)sulfanes. To a solution of (E)- or (Z)-
2-(arylmethylene)cyclopropylcarbinols 1 (0.30 mmol in 1.0 mL of
(7) Barton, D. H. R.; McCombie, S. W. J. Chem. Soc., Perkin Trans. 1
1975, 1574.
(8) (a) Zimmerman, H. E.; Heydinger, J. A. J. Org. Chem. 1991, 56,
1747. (b) Zimmerman, H. E.; Kamath, A. P. J. Am. Chem. Soc. 1988, 110,
900. (c) Padwa, A.; Kennedy, G. D. J. Org. Chem. 1984, 49, 4344. (d)
Chapuisat, X.; Jean, Y. J. Am. Chem. Soc. 1975, 97, 6325. (e) Lubitz, W.;
Lendzian, F.; Bittl, R. Acc. Chem. Res. 2002, 35, 313. (f) Pincock, J. A.
Acc. Chem. Res. 1997, 30, 43 and references cited therein.
(9) (a) Kochi, J. K.; Krusic, P. J.; Eaton, D. R. J. Am. Chem. Soc. 1969,
91, 1877. (b) Gajewski, J. J. J. Am. Chem. Soc. 1968, 90, 7178. (c) Chesick,
J. P. J. Am. Chem. Soc. 1963, 85, 2720. (d) Gilbert, J. C.; Butler, J. R. J.
Am. Chem. Soc. 1969, 91, 2169.
676 J. Org. Chem., Vol. 73, No. 2, 2008

Thermal Rearrangement of Sulfanes and Selanes
tetrahydrofuran) were added triethylamine (0.36 mmol) and meth-
anesulfonyl chloride (0.36 mmol) under argon atmosphere. The
reaction mixtures were stirred at room temperature for 20 min, then
sodium benzenethiolate (0.90 mmol), sodium borohydride (0.60
mmol), and water (6.00 mmol) were added. Then, the mixtures of
2 and 3 were heated under reflux in tetrahydrofuran (THF). After
the transformation was completed on the basis of TLC plates, the
solvent was removed under reduced pressure and the residue was
purified by silica gel column chromatograph to afford the pure
products 3.
General Procedure for the Preparation of (2-Arylmeth-
ylidenebut-3-enyl)(phenyl)selanes. To a solution of 2-(arylmeth-
ylene)cyclopropylcarbinols 1 (0.30 mmol in 1.0 mL of tetrahydro-
furan) were added triethylamine (0.36 mmol) and methanesulfonyl
chloride (0.36 mmol) under argon atmosphere. The mixtures were
stirred at room temperature for 20 min, then 1,2-diphenyldiselane
(0.60 mmol) and sodium borohydride (0.90 mmol) were added.
After stirring for a given time, mixtures of {[(2-arylmethylene)-
cyclopropyl]methyl}(phenyl)selanes 4 or (2-arylmethylidenebut-
3-enyl)(phenyl)selanes 5 were isolated. Then, the mixtures of 4 and
5 were heated under reflux in tetrahydrofuran. After the transforma-
tion completed on the basis of TLC plates, the solvent was removed
under reduced pressure and the residue was purified by silica gel
column chromatograph to afford the pure products 5.
Acknowledgment. We thank the Shanghai Municipal Com-
mittee of Science and Technology (04JC14083, 06XD14005),
Chinese Academy of Sciences (KGCX2-210-01), and the
National Natural Science Foundation of China for financial
support (Grants 20472096, 203900502, 20672127, and 20732008).
Supporting Information Available: The spectroscopic data of
the new compounds and the detailed description of experimental
procedures. This material is available free of charge via the Internet
at http://pubs.acs.org.
JO7021636
J. Org. Chem, Vol. 73, No. 2, 2008 677