Cycloaddition Reactions of 1-Phenylseleno-2-(p-toluenesulfonyl)ethyne

Article abstract of DOI:10.1021/jo990730t

1-Phenylseleno-2-(p-toluenesulfonyl)ethyne (1) is an effective dienophile and dipolarophile. It underwent facile Diels-Alder reactions with a variety of dienes to afford vicinal sulfone- and selenide-functionalized 1,4-cyclohexadienes. Unexpected regiochemistry that is the opposite of what is obtained with simple acetylenic sulfones was observed with several unsymmetrical dienes containing methyl or methoxy substituents at the 1- or 2-position. Acetylene 1 reacted with (trimethylsilyl)methyl azide, diazomethane, and 2,4,6-trimethylbenzonitrile N-oxide via 1,3-dipolar cycloadditions to afford the corresponding triazole, 1,2-diazole, and isoxazole products. It also underwent an ene reaction with β-pinene that showed anomalous regiochemistry compared to other acetylenic sulfones. The Diels-Alder cycloadducts obtained from the reaction of 1 with 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene were readily converted into the corresponding β-keto sulfones and ketones, thus rendering 1 as the synthetic equivalent of p-toluenesulfonylketene and ketene, respectively. Base-catalyzed elimination of TsOH from the Diels-Alder cycloadduct obtained with 2,3-dimethyl-1,3-butadiene afforded the corresponding aryl phenyl selenide, while the adduct from piperylene underwent oxidation to its selenoxide, followed by a Pummerer-type reaction to produce 2-(phenylseleno)-3-(p-toluenesulfonyl)toluene. The reaction of the bicyclic Diels-Alder product obtained from 1,3-cyclohexadiene with MeCu(SePh)Li resulted in substitution of the phenylseleno moiety by a methyl group, whereas similar treatment of the monocyclic adduct derived from piperylene effected elimination of PhSeH and aromatization.

Full text of DOI:10.1021/jo990730t

7426
J . Org. Chem. 1999, 64, 7426-7432
Cycloa d d ition Rea ction s of
1-P h en ylselen o-2-(p-tolu en esu lfon yl)eth yn e
Thomas G. Back,* Richard J . Bethell, Masood Parvez, J erry A. Taylor, and Daniel Wehrli
Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N 1N4
Received May 3, 1999
1-Phenylseleno-2-(p-toluenesulfonyl)ethyne (1) is an effective dienophile and dipolarophile. It
underwent facile Diels-Alder reactions with a variety of dienes to afford vicinal sulfone- and
selenide-functionalized 1,4-cyclohexadienes. Unexpected regiochemistry that is the opposite of what
is obtained with simple acetylenic sulfones was observed with several unsymmetrical dienes
containing methyl or methoxy substituents at the 1- or 2-position. Acetylene 1 reacted with
(trimethylsilyl)methyl azide, diazomethane, and 2,4,6-trimethylbenzonitrile N-oxide via 1,3-dipolar
cycloadditions to afford the corresponding triazole, 1,2-diazole, and isoxazole products. It also
underwent an ene reaction with â-pinene that showed anomalous regiochemistry compared to other
acetylenic sulfones. The Diels-Alder cycloadducts obtained from the reaction of 1 with 2,3-dimethyl-
1,3-butadiene and 1,3-cyclohexadiene were readily converted into the corresponding â-keto sulfones
and ketones, thus rendering 1 as the synthetic equivalent of p-toluenesulfonylketene and ketene,
respectively. Base-catalyzed elimination of TsOH from the Diels-Alder cycloadduct obtained with
2,3-dimethyl-1,3-butadiene afforded the corresponding aryl phenyl selenide, while the adduct from
piperylene underwent oxidation to its selenoxide, followed by a Pummerer-type reaction to produce
2-(phenylseleno)-3-(p-toluenesulfonyl)toluene. The reaction of the bicyclic Diels-Alder product
obtained from 1,3-cyclohexadiene with MeCu(SePh)Li resulted in substitution of the phenylseleno
moiety by a methyl group, whereas similar treatment of the monocyclic adduct derived from
piperylene effected elimination of PhSeH and aromatization.
Acetylenic and other types of unsaturated sulfones
their selenium substituents have, to our knowledge, not
yet been investigated. We recently reported the prepara-
tion of the title compound 15 (Scheme 1), and demon-
strated that it undergoes conjugate addition reactions
with organocopper reagents and various heteroatom
nucleophiles. Of particular interest was the observation
that hard nucleophiles, such as amines and alkoxides,
attack 1 R to the sulfone group, leading to preferential
or exclusive formation of the corresponding anti-Michael
(with respect to the sulfone moiety) regioisomers. This
suggests that the selenide substituent shows an unex-
pectedly powerful effect with respect to the regiocontrol
of such additions. We now report that 1 also acts as an
effective dienophile6 and dipolarophile, affording cycload-
ducts containing sulfone and selenide functionalities that
provide opportunities for further synthetic transforma-
tions. Moreover, we note that, as with the anti-Michael
conjugate additions, the cycloadditions of 1 again display
unexpected regiochemistry in several of the examples
studied.
have many synthetic applications,1 including their use
as dienophiles in Diels-Alder reactions.2 The electron-
withdrawing sulfone group has the effect of both activat-
ing the dienophile and of controlling the regiochemistry
of cycloadditions, as well as providing a useful functional
group for further transformations. Removal of the sulfone
moiety after the completion of the procedure by reductive
desulfonylation provides access to sulfur-free products.3
Acetylenic selenides are also known,4 but their cycload-
dition chemistry and the activating/directing abilities of
* To whom correspondence should be addressed. Phone: (403) 220-
6256. Fax: (403) 289-9488. E-mail: tgback@ucalgary.ca.
(1) (a) Simpkins, N. S. Sulphones in Organic Synthesis; Pergamon
Press: Oxford, 1993. (b) Fuchs, P. L.; Braish, T. F. Chem. Rev. 1986,
86, 903. (c) Trost, B. M. Bull. Chem. Soc. J pn. 1988, 61, 107. (d)
Simpkins, N. S. Tetrahedron 1990, 46, 6951. (e) Tanaka, K.; Kaji, A.
In The Chemistry of Sulphones and Sulphoxides; Patai, S., Rappoport,
Z., Stirling, C. J . M., Eds.; Wiley: Chichester, 1988; Chapter 15.
(2) For examples, see ref 1a, Chapters 2 and 6. Also see: (a) De
Lucchi, O.; Pasquato, L. Tetrahedron 1988, 44, 6755. (b) Paquette, L.
A.; Williams, R. V. Tetrahedron Lett. 1981, 22, 4643. (c) Williams, R.
V.; Chauhan, K.; Gadgil, V. R. J . Chem. Soc., Chem. Commun. 1994,
1739. (d) Hickey, E. R.; Paquette, L. A. J . Am. Chem. Soc. 1995, 117,
163. (e) Pasquato, L.; De Lucchi, O.; Krotz, L. Tetrahedron Lett. 1991,
32, 2177. (f) Corey, E. J .; Da Silva J ardine, P.; Mohri, T. Tetrahedron
Lett. 1988, 29, 6409. (g) Kotian, P. L.; Carroll, F. I. Synth. Commun.
1995, 25, 63. (h) Davis, A. P.; Whitham, G. H. J . Chem. Soc., Chem.
Commun. 1980, 639. (i) Huang, D. F.; Shen, T. Y. Tetrahedron Lett.
1993, 34, 4477. (j) J ones, C. D.; Simpkins, N. S.; Giblin, G. M. P.
Tetrahedron Lett. 1998, 39, 1021 and 1023. (k) Clasby, M. C.; Craig,
D.; Marsh, A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1444. (l) Virgili,
M.; Belloch, J .; Moyano, A.; Perica`s, M. A.; Riera, A. Tetrahedron Lett.
1991, 32, 4583. (m) Djeghaba, Z.; J ousseaume, B.; Ratier, M.; Dubou-
din, J .-G. J . Organomet. Chem. 1986, 304, 115.
Resu lts a n d Discu ssion
The Diels-Alder reactions of 1 with a series of dienes
are shown in Table 1. Entries 1-5 are with symmetrical
dienes and indicate that the cycloadditions proceed under
mild conditions and in excellent yield, without the need
(5) (a) Back, T. G.; Wehrli, D. Tetrahedron Lett. 1995, 36, 4737. (b)
Back, T. G.; Bethell, R. J .; Parvez, M.; Wehrli, D. J . Org. Chem. 1998,
63, 7908. (c) Compound 1 was also recently reported as an intermediate
in the reaction of tosylalkynyliodonium triflate with benzeneseleno-
late: Stang, P. J .; Murch, P. Synthesis 1997, 1378.
(6) Preliminary communication: Back, T. G.; Wehrli, D. Synlett
1995, 1123. This work is largely based on the Ph.D. Thesis of D. Wehrli
(University of Calgary, 1997).
(3) Reference 1a, Chapter 9 and references therein.
(4) For a recent review, see: Stang, P. J .; Zhdankin, V. V. In
Comprehensive Organic Functional Group Transformations; Katritzky,
A. R., Meth-Cohn, O., Rees, C. W., Eds.; Elsevier: Oxford, 1995; Vol.
2, Chapter 2.21.
10.1021/jo990730t CCC: $18.00 © 1999 American Chemical Society
Published on Web 09/10/1999

Reactions of 1-Phenylseleno-2-(p-toluenesulfonyl)ethyne
J . Org. Chem., Vol. 64, No. 20, 1999 7427
Sch em e 1
Sch em e 2
Ta ble 1. Diels-Ald er Cycloa d d ition s of 1
entries 6 and 9 preferentially afforded the regioisomers
where the electron-withdrawing sulfone group is oriented
1,3 with respect to the diene substituent (7 and 11,
respectively). Similarly, when the methyl or methoxy
group was located in the 2-position of the diene, the
corresponding 1,3-isomers 8 and 12 either were formed
in an amount equal to that of the expected 1,4-regioiso-
mer 9 (entry 7) or were the sole isolated product (entry
10). The cycloadduct obtained from 1-acetoxy-1,3-buta-
diene spontaneously eliminated acetic acid to produce 10
under the conditions of the experiment, thereby preclud-
ing determination of the regiochemistry. The assignment
of regiochemistry to adducts 7 and 11 and 12 was made
on the basis of NOE experiments (see the Experimental
Section). That of 7 was confirmed by further chemical
transformation (vide infra). Unequivocal assignment of
regiochemistry could not be made for 8 and 9, which were
formed in equal amounts (NMR integration) and could
not be separated. If one assumes that the above reac-
tions are concerted and involve interaction of the
diene HOMO with the LUMO of 1, then the regiochem-
istry of these examples is anomalous, since the effect of
the selenide group appears to outweigh that of the
strongly electron-withdrawing sulfone moiety. While a
clear explanation for these results is lacking, they are
consistent with the observed regiochemistry in certain
conjugate additions of 1, as noted earlier.8 It is also
interesting to note that an acetylenic sulfone containing
a â-silyl substituent has been reported to react with
1-methoxy-1,3-cyclohexadiene to afford the corresponding
anomalous 1,3-cycloadduct (with respect to the sulfone
and methoxy groups),2c whereas a related â-stannyl
acetylenic sulfone afforded the normal 1,2-cycloadduct
with 1-methoxy-1,3-butadiene.2m Finally, acrolein af-
forded the adduct 13 in modest yield (Table 1, entry 11)
via a hetero-Diels-Alder reaction.9,10
(7) Fleming, I. Frontier Orbitals and Organic Chemical Reactions;
Wiley: Chichester, 1976.
(8) If 1 acts as the dienophile in a Diels-Alder cycloaddition with
normal electron demand, then the frontier orbital interaction that
determines the regiochemistry is between the LUMO of 1 and the
HOMO of the diene. We noted earlier (ref 5b) that the LUMO of 1 is
distributed roughly evenly over the two acetylenic carbon atoms, in
contrast to what is expected in a simple acetylenic sulfone, where the
â-carbon atom of the LUMO normally possesses the larger coefficient.
Thus, it appears that the selenide substituent significantly affects the
LUMO of 1 and therefore plays a major role in determining the
regiochemistry of the cycloadditions and conjugate additons of 1.
(9) It has been pointed out that hetero-Diels-Alder reactions
between an R,â-unsaturated aldehyde and an electron-rich dienophile
can proceed with inverse electron demand: (a) Carruthers, W. Cy-
cloaddition Reactions in Organic Synthesis; Pergamon Press: Oxford,
1990; pp 40-45. (b) Desimoni, G.; Tacconi, G. Chem. Rev. 1975, 75,
651.
a
RT ) room temperature; ∆ ) 60-65 °C.
for Lewis acid catalysts. Entries 6-10 involve unsym-
metrical dienes, resulting in the possible formation of two
regioisomers. In general, dienes with an electron-donat-
ing substituent at the 1-position are expected to react
with dienophiles containing an electron-withdrawing
substituent to afford the corresponding 1,2-regioisomers
preferentially. On the other hand, when the donor group
is at the 2-position of the diene, the 1,4-regioisomer is
favored (Scheme 2).7 It is therefore interesting to note
that the 1-methyl- and 1-methoxy-substituted dienes in

7428 J . Org. Chem., Vol. 64, No. 20, 1999
Back et al.
Sch em e 3
Sch em e 4
tautomer 18) was isolated in 81% yield when the reaction
was performed rapidly. However, upon exposure to excess
diazomethane for a longer period, the cycloaddition was
followed by N-methylation and the two isomers 19 and
20 were isolated in yields of 69% and 11%, respectively.
Both products were also obtained when pure 17 (or 18)
was treated with diazomethane, indicating that 20 is not
derived from the unidentified minor regioisomer of 17
(or 18) formed in the initial cycloaddition step. The nitrile
N-oxide 2117 afforded the single isolable regioisomer 22.
The structures of the major isomer 19 from the diazo-
methane cycloaddition and that of 22 were established
unequivocally by X-ray crystallography (see the Support-
ing Information).
Acetylenic sulfones are also known to undergo Lewis
acid-catalyzed ene reactions.2m,18 We observed that the
treatment of â-pinene with 1 afforded the ene reaction
product 23 in the absence of a Lewis acid, as shown in
Scheme 4. Only the one regioisomer, tentatively identi-
fied by NOE experiments and by the chemical shift of
the olefinic proton of the â-(phenylseleno)vinyl sulfone
moiety,19 was isolated. Furthermore, deselenization of the
product with nickel boride20 afforded a mixture of satu-
rated and partly unsaturated and isomerized products
24a and 24b in the ratio of 57:43, each formed as a
mixture of epimers. The regiochemistry of the ene reac-
tion was confirmed by decoupling experiments involving
the TsCH-CH3 moiety of the reduced products (see the
Experimental Section). Attempts to improve the yield
with various Lewis acids were unsuccessful because of
the decomposition of 1 in their presence. The regiochem-
istry of this reaction is again anomalous compared to ene
reactions with other acetylenic sulfones.2m,18
Only a few reactions of acetylenic sulfones with 1,3-
dipoles have been previously reported.11 Although frontier
molecular orbital interactions in 1,3-dipolar cycloaddi-
tions12 have been previously investigated,7,13,14 the regio-
chemistry of such processes with acetylenic dipolarophiles
is generally more difficult to predict than that of the
corresponding Diels-Alder reactions. The reactions of 1
with three representative dipoles were investigated, and
the results are shown in Scheme 3. The azide 1415
produced cycloadducts 15 and 16 in yields of 58% and
18%, respectively. The assignment of the major isomer
as 15 was established by means of an NOE experiment
(Experimental Section). Azide 14 reacts with acetylenic
esters and ketones to afford predominantly the regioiso-
mers derived from attack of its terminal nitrogen atom
R to the carbonyl group of the acetylene.15b On the other
hand, in the principal regioisomer 15, obtained from 1
and 14, the terminal nitrogen atom is attached R to the
selenide moiety, and not R to the more strongly electron-
withdrawing sulfone group. When diazomethane16 was
used as the dipole, only one regioisomer 17 (or its
Some further transformations of the Diels-Alder cy-
cloadducts were then studied. First of all, we investigated
(10) It is possible that 1 is capable of cycloadditions with either
normal or inverse electron demand, depending upon whether the other
reactant is electron-rich or electron-poor. It is interesting to note that
2-sulfonyl-1,3-dienes also display dual electron demand in cycloaddi-
tions and thus react with both electron-rich and electron-deficient
alkenes: Ba¨ckvall, J .-E.; J untunen, S. K. J . Am. Chem. Soc. 1987, 109,
6393.
(11) Croce, P. D.; La Rosa, C.; Zecchi, G. J . Chem. Soc., Perkin Trans.
1 1985, 2621.
(12) For a general review of 1,3-dipolar cycloadditions, see: 1,3-
Dipolar Cycloaddition Chemistry; Padwa, A., Ed.; Wiley: New York,
1984; Vols. 1 and 2.
(13) See ref 9a, Chapter 6.
(14) Rauk, A. Orbital Interaction Theory of Organic Chemistry;
Wiley: New York, 1994; pp 194-197.
(15) For 1,3-dipolar cycloadditions of azides, see: (a) Sheradsky, T.
In The Chemistry of the Azido Group; Patai, S., Ed.; Wiley: London,
1971; Chapter 6. For other 1,3-dipolar cycloadditions of 14, see: (b)
Tsuge, O.; Kanemasa, S.; Matsuda, K. Chem Lett. 1983, 1131.
(16) For 1,3-dipolar cycloadditions of diazo compounds, see: Wulf-
man, D. S.; Linstrumelle, G.; Cooper, C. F. In The Chemistry of
Diazonium and Diazo Groups; Patai, S., Ed.; Wiley: Chichester, 1978;
Part 2, Chapter 18.
(17) For 1,3-dipolar cycloadditions of nitrile oxides, see: Torsell, K.
B. G. Nitrile Oxides, Nitrones and Nitronates in Organic Synthesis;
VCH: Weinheim, 1988.
(18) Snider, B. B.; Kirk, T. C.; Roush, D. M.; Gonzalez, D. J . Org.
Chem. 1980, 45, 5015.
(19) Numerous â-(phenylseleno)vinyl sulfones of regiochemistry
opposite that of product 24 [i.e., R(PhSe)CdCHTs] have been prepared
by the selenosulfonation of terminal acetylenes. The olefinic protons
of these compounds have NMR signals at significantly higher field (ca.
δ 6 ppm) than 24 (δ 7.20 ppm), thereby supporting the structure
assignment of the latter product. See: Back, T. G.; Collins, S.; Kerr,
R. G. J . Org. Chem. 1983, 48, 3077.
(20) Back, T. G.; Birss, V. I.; Edwards, M.; Krishna, M. V. J . Org.
Chem. 1988, 53, 3815.

Reactions of 1-Phenylseleno-2-(p-toluenesulfonyl)ethyne
J . Org. Chem., Vol. 64, No. 20, 1999 7429
Sch em e 5
Sch em e 7
Sch em e 8
base than sodium methoxide. The aromatized product 32
was isolated in excellent yield, and was presumably
formed via a Pummerer-type mechanism, as shown in
Scheme 7. Deselenization of 32 with nickel boride20
afforded only m-tolyl p-tolyl sulfone 33, and not the o-tolyl
p-tolyl isomer. This confirms the indicated regiochemistry
of both 32 and the original cycloadduct 7. Finally,
â-(phenylseleno)vinyl sulfones are known to undergo
substitution of the selenide moiety by organocopper
reagents of general structure RCu(SePh)Li.5b,24 A similar
substitution was observed with the bicyclic compound 4,
whereas elimination of the selenol moiety, with ac-
companying aromatization, occurred in the case of the
monocyclic adduct 7 (Scheme 8).
These experiments indicate that the acetylene 1 is an
efficient dienophile and dipolarophile. It therefore pro-
vides access to 1,4-cyclohexadienes and various hetero-
cycles (namely, 1,2,3-triazoles, 1,2-diazoles, and isox-
azoles) containing the useful sulfone and selenide
functionalities. Further transformations of the cyload-
ducts indicate that 1 can be used as a ketene equivalent
and in certain elimination and substitution reactions. The
unexpected regiochemistry of cycloadditions of 1 with
unsymmetrical dienes is under further study.
Sch em e 6
the possibility that 1 could be employed as a ketene
equivalent in Diels-Alder reactions, as shown by the two
representative examples in Scheme 5. The instability of
ketenes, as well their tendency to undergo [2+2] instead
of [4+2] cycloadditions,21 has prompted efforts to design
suitable synthetic equivalents for use in the latter
reactions.22,23 Both the monocyclic and bicyclic adducts
3 and 4 were converted into the enol ethers 25 and 28,
respectively, by oxidation and addition-elimination with
sodium methoxide. Hydrolysis of the latter products to
26 and 29, followed by reductive desulfonylation, then
afforded the corresponding ketones 27 and 30, respec-
tively. Direct hydrolysis of the intermediate selenoxides
was less effective in producing the desired ketones. Thus,
1 acts as the synthetic equivalent of ketene or p-
(toluenesulfonyl)ketene in these transformations.
Three other types of transformations of representative
cycloadducts were also investigated. First, the treatment
of cycloadduct 3 with potassium tert-butoxide without
prior oxidation resulted in elimination of p-toluenesulfinic
acid to produce the corresponding aryl phenyl selenide
31 (Scheme 6). Second, adduct 7 was oxidized to its
selenoxide and then treated with triethylamine, a milder
Exp er im en ta l Section
The following compounds were prepared by literature
methods: acetylene 1,5a,b 2-methoxy-1,3-butadiene,25 (tri-
methylsilyl)methyl azide (14),26 2,4,6-trimethylbenzonitrile
N-oxide,27 and cuprous benzeneselenolate.24 Dienes were dis-
tilled prior to use. Chromatography refers to flash chroma-
tography performed on silica gel (230-400 mesh), unless
otherwise indicated. NMR spectra were recorded in deuterio-
chloroform with TMS or residual chloroform as the internal
standard.
(21) See: (a) Reference 9a, Chapter 7. (b) Tidwell, T. T. Ketenes;
Wiley: New York, 1995; Chapter 5. (c) Brady, W. T. In The Chemistry
of Ketenes, Allenes and Related Compounds; Patai, S., Ed.; Wiley:
Chichester, 1980; Part 1, Chapter 8.
(22) For a review of ketene equivalents, see: Ranganathan, S.;
Ranganathan, D.; Mehrotra, A. K. Synthesis 1977, 289.
(24) Back, T. G.; Collins, S.; Krishna, M. V.; Law, K.-W. J . Org.
Chem. 1987, 52, 4258.
(25) Dolby, L. J .; Marshall, K. S. Org. Prep. Proced. Int. 1969, 1,
229.
(26) Nishiyama, K.; Tanaka, N. J . Chem. Soc., Chem. Commun.
1983, 1322.
(27) Grundmann, C.; Richter, R. J . Org. Chem. 1968, 33, 476.
(23) For some previous examples of synthetic equivalents of ketene,
see: (a) Corey, E. J .; Ravindranathan, T.; Terashima, S. J . Am. Chem.
Soc. 1971, 93, 4326. (b) Trost, B. M.; Tamaru, Y. J . Am. Chem. Soc.
1975, 97, 3528. (c) Evans, D. A.; Scott, W. L.; Truesdale, L. K.
Tetrahedron Lett. 1972, 121. (d) Bartlett, P. A.; Green, F. R., III; Webb,
T. R. Tetrahedron Lett. 1977, 331.

7430 J . Org. Chem., Vol. 64, No. 20, 1999
Back et al.
Diels-Ald er Cycloa d d ition s of 1-P h en ylselen o-2-(p-
tolu en esu lfon yl)eth yn e (1). Typ ica l P r oced u r e (En tr y 1,
Ta ble 1). A 1 mL thick-walled reaction vial with a Teflon-
lined cap containing acetylene 1 (210 mg, 0.626 mmol) was
cooled to -78 °C, and excess 1,3-butadiene was condensed into
the vial from a lecture bottle. The sealed vial was warmed to
room temperature, and stirring was continued for 4 days. The
excess butadiene was then allowed to evaporate, and the oily
residue was chromatographed (elution with 5% ethyl acetate-
hexanes) to afford 199 mg (81%) of 1-phenylseleno-2-(p-
toluenesulfonyl)-1,4-cyclohexadiene (2) as a colorless oil; IR
(neat) 1300, 1148 cm-1; 1H NMR (200 MHz) δ 8.00 (d, J ) 8.3
Hz, 2 H), 7.60 (dd, J ) 8.0 Hz, 1.5 Hz, 2 H), 7.46-7.28 (m, 5
H), 5.66 (m, 1 H), 5.36 (m, 1 H), 3.06 (m, 2 H), 2.63 (m, 2 H),
2.47 (s, 3 H); 13C NMR (100 MHz) δ 144.4, 143.2, 137.7, 137.3,
129.8, 129.6, 129.4, 129.1, 127.7, 127.2, 122.4, 122.2, 35.3, 29.0,
21.6; MS m/z (relative intensity, %) 390 (44, M+), 233 (33), 157
(54), 91 (100); exact mass calcd for C19H18O2SSe 390.0196,
found 390.0194.
The other products listed in Table 1 were prepared similarly,
by heating the diene with 1 in a sealed vial under the
conditions indicated in Table 1. In general, a 5-10-fold excess
of the diene was employed, and the yields in Table 1 are based
on the acetylene 1.
4,5-Dim eth yl-1-p h en ylselen o-2-(p-tolu en esu lfon yl)-1,4-
cycloh exa d ien e (3) (En tr y 2): mp 180-182 °C (from chlo-
roform-ethanol); IR (CH2Cl2) 1310, 1157 cm-1; 1H NMR (200
MHz) δ 8.00 (d, J ) 8.1 Hz, 2 H), 7.58 (dd, J ) 6.5, 0.5 Hz, 2
H), 7.41-7.28 (m, 5 H), 2.97 (t, J ) 7.2 Hz, 2 H),28 2.53 (t, J )
7.1 Hz, 2 H),28 2.46 (s, 3 H), 1.58 (s, 3 H), 1.35 (s, 3 H); 13C
NMR (50 MHz) δ 144.3, 143.0, 137.53, 137.50, 130.4, 129.6,
129.3, 129.1, 127.6, 127.3, 121.9, 121.7, 41.7, 35.3, 21.6, 17.7,
17.3; MS m/z (relative intensity, %) 418 (7, M+), 182 (23), 105
(27), 91 (100); exact mass calcd for C21H22O2SSe 418.0505,
found 418.0533.
2.74 (m, 1 H), 2.46 (s, 3 H), 1.08 (d, J ) 6.8 Hz, 3 H); an NOE
was observed for δ 7.49 (ortho-protons of PhSe) when δ 2.74
(H-3) was irradiated and vice versa; MS m/z (relative intensity,
%) 404 (20, M+), 155 (28), 91 (100). Anal. Calcd for C20H20O2-
SSe: C, 59.55; H, 5.00. Found: C, 59.60; H, 4.69.
4-Meth yl-1-p h en ylselen o-2-(p-tolu en esu lfon yl)-1,4-cy-
cloh exa d ien e (8) a n d 4-Meth yl-2-p h en ylselen o-1-(p-tolu -
en esu lfon yl)-1,4-cycloh exa d ien e (9) (En tr y 7). The un-
separated mixture, containing equal amounts of 8 and 9, was
obtained as a colorless oil: IR (CH2Cl2) 1311, 1302, 1146, 1085
cm-1; 1H NMR (200 MHz) δ 8.00 (two superimposed d, total 4
H, both isomers), 7.6 (two superimposed dd, total 4 H, both
isomers), 7.41-7.28 (m, total 10 H, both isomers), 5.35 (m, 1
H, one isomer), δ 5.05 (m, 1 H, one isomer; the reported ratio
is based on the integration of this signal and that at δ 5.35),
3.10 (m, 2 H, one isomer), 2.91 (t, J ) 7.6 Hz, 2 H, one
isomer),28 2.64 (m, 2 H, one isomer), 2.51 (t, J ) 7.7 Hz, 2 H,
one isomer),28 2.47 (s, total 6 H, both isomers), 1.62 (d, J )
0.8 Hz, 3 H, one isomer), δ 1.41 (d, J ) 0.9 Hz, 3 H, one isomer);
MS m/z (relative intensity, %) 404 (35, M+), 168 (60), 91 (100).
Anal. Calcd for C20H20O2SSe: C, 59.55; H, 5.00. Found: C,
59.47; H, 4.51.
1-P h en ylselen o-2-(p-tolu en esu lfon yl)ben zen e (10) (En -
tr y 8): mp 141-144 °C (from ethanol); IR (CH2Cl2) 1315, 1304,
1
1154 cm-1; H NMR (200 MHz) δ 8.18 (dd, J ) 7.7, 1.7 Hz, 1
H), 7.99 (d, J ) 8.4 Hz, 2 H), 7.49-7.17 (m, 9 H), 6.99 (dd, J
) 7.5, 1.7 Hz, 1 H), 2.43 (s, 3 H); MS m/z (relative intensity,
%) 388 (100, M+), 323 (84), 91 (31). Anal. Calcd for C19H16O2-
SSe: C, 58.91; H, 4.16. Found: C, 58.89; H, 3.94.
3-Met h oxy-2-p h en ylselen o-1-(p -t olu en esu lfon yl)-1,4-
cycloh exa d ien e (11) (En tr y 9): colorless oil; IR (CH2Cl2)
1304, 1150 cm-1; 1H NMR (400 MHz) δ 8.04 (d, J ) 8.3 Hz, 2
H), 7.59 (dd, J ) 6.9, 1.4 Hz, 2 H), 7.38-7.28 (m, 5 H), 6.08
(dt, J ) 9.9, 3.5 Hz, 1 H), 5.55 (m, 1 H) 4.29 (dd, J ) 9.5, 4.7
Hz, 1 H), 3.26 (d of quintets, J ) 23.6, 2.7 Hz, 1 H), 3.06 (dm,
J ) 23.6 Hz, 1 H), 2.93 (s, 3 H), 2.47 (s, 3 H); an NOE was
observed for δ 7.59 (ortho-protons of PhSe) when δ 4.29 (H-3)
was irradiated and vice versa; 13C NMR (100 MHz) δ 144.8,
143.6, 137.5, 137.1, 136.7, 129.7, 129.2, 128.9, 128.2, 127.9,
127.2, 122.7, 70.8, 50.9, 30.4, 21.7; MS m/z (relative intensity,
%) 420 (15, M+), 388 (100); exact mass calcd for C20H20O3SSe
420.0338, found 420.0343.
2-P h en ylselen o-3-(p-tolu en esu lfon yl)-2,5-bicyclo[2.2.2]-
octa d ien e (4) (En tr y 3): mp 128-130 °C (from ethanol); IR
1
(CH2Cl2) 1318, 1299, 1147, 1088 cm-1; H NMR (400 MHz) δ
7.86 (d, J ) 8.3 Hz, 2 H), 7.55 (dd, J ) 8.0, 1.2 Hz, 2 H), 7.45-
7.32 (m, 5 H), 6.24 (ddd, J ) 6.2, 6.0, 1.2 Hz, 1 H), 6.00 (ddd,
J ) 6.3, 6.1, 1.2 Hz, 1 H), 4.10-4.07 (m, 1 H), 3.51-3.48 (m,
1 H), 2.44 (s, 3 H); 1.37-1.20 (m, 4 H); MS m/z (relative
intensity, %) 416 (45, M+), 388 (87), 323 (100). Anal. Calcd for
4-Met h oxy-1-p h en ylselen o-2-(p -t olu en esu lfon yl)-1,4-
cycloh exa d ien e (12) (En tr y 10). Chromatography was
performed on alumina: colorless oil; IR (CH2Cl2) 1301, 1147
C
21H20O2SSe: C, 60.72; H, 4.85. Found: C, 60.27; H, 4.88.
2-P h en ylselen o-3-(p-tolu en esu lfon yl)-2,5-bicyclo[2.2.1]-
cm-1 1H NMR (400 MHz) δ 7.99 (d, J ) 8.2 Hz, 2 H), 7.62
;
h ep ta d ien e (5) (En tr y 4): mp 137-138.5 °C (from hexanes);
IR (CH2Cl2) 1310, 1299, 1138 cm-1; 1H NMR (400 MHz) δ 7.79
(d, J ) 8.3 Hz, 2 H), 7.61 (dd, J ) 8.3, 1.3 Hz, 2 H), 7.47-7.36
(m, 3 H), 7.33 (d, J ) 8.1 Hz, 2 H), 6.46 (dd, J ) 5.0, 2.9 Hz,
1 H), 6.35 (dd, J ) 5.0, 3.3 Hz, 1 H), 3.81 (m, 1 H), 3.32 (m, 1
H), 2.45 (s, 3 H), 2.12 (ddd, J ) 6.7, 1.5, 1.5 Hz, 1 H), 1.83
(ddd, J ) 6.8, 1.6, 1.6 Hz, 1 H); MS m/z (relative intensity, %)
402 (90, M+), 245 (43), 165 (100). Anal. Calcd for C20H18O2-
SSe: C, 59.85; H, 4.52. Found: C, 59.58; H, 4.50.
(dd, J ) 8.0, 1.0 Hz, 2 H), 7.38-7.28 (m, 5 H), 4.30 (br t, J )
3.6 Hz, 1 H), 3.44 (s, 3 H), 3.06 (dt, J ) 7.3, 0.7 Hz, 2 H),28
2.75 (dt, J ) 7.3, 3.6 Hz, 2 H),28 2.47 (s, 3 H); an NOE was
observed for δ 7.99 (ortho-protons of Ts) when δ 3.06 (H-3)
was irradiated and vice versa; when δ 3.06 was irradiated,
the signal at δ 3.44 (OMe) was also enhanced; 13C NMR (100
MHz) δ 151.4, 144.5, 143.5, 137.8, 137.1, 136.3, 129.7, 129.4,
129.1, 127.7, 127.3, 89.3, 54.2, 35.8, 30.9, 21.7; MS m/z (relative
intensity, %) 420 (25, M+), 157 (55), 91 (100); exact mass calcd
for C20H20O3SSe 420.0338, found 420.0302.
7-Oxa-2-ph en ylselen o-3-(p-tolu en esu lfon yl)-2,5-bicyclo-
[2.2.1]h ep ta d ien e (6) (En tr y 5): mp 135-138 °C (from
1
ethanol); IR (CH2Cl2) 1312, 1302, 1270, 1149 cm-1; H NMR
1-Oxa -3-p h en ylselen o-2-(p-tolu en esu lfon yl)-2,5-cyclo-
h exa d ien e (13) (En tr y 11). Chromatography was performed
(400 MHz) δ 7.83 (d, J ) 8.3 Hz, 2 H), 7.65 (dd, J ) 8.3, 1.4
Hz, 2 H), 7.51-7.36 (m, 5 H), 6.91 (dd, J ) 5.3, 1.7 Hz, 1 H),
6.79 (dd, J ) 5.3, 1.9 Hz, 1 H), 5.46 (dd, J ) 1.5, 1.5 Hz, 1 H),
4.90 (dd, J ) 1.6, 1.6 Hz, 1 H), 2.47 (s, 3 H); MS m/z (relative
intensity, %) 404 (20, M+), 336 (100). Anal. Calcd for C19H16O3-
SSe: C, 56.58; H, 4.00. Found: C, 56.55; H, 4.14.
3-Meth yl-2-p h en ylselen o-1-(p-tolu en esu lfon yl)-1,4-cy-
cloh exa d ien e (7) (En tr y 6): mp 125-130 °C (from ethanol);
IR (CH2Cl2) 1301, 1150 cm-1; 1H NMR (400 MHz) δ 8.03 (d, J
) 8.2 Hz, 2 H), 7.49 (dd, J ) 8.1, 1.0 Hz, 2 H), 7.40-7.28 (m,
5 H), 5.68-5.64 (m, 1 H), 5.49-5.45 (m, 1 H), 3.18 (ddt, J )
22.1, 2.7, 0.4 Hz, 1 H), 3.05 (ddt, J ) 22.1, 4.4, 0.9 Hz, 1 H),
on alumina: colorless oil; IR (CH2Cl2) 1303, 1139 cm-1 1H
;
NMR (200 MHz) δ 7.94 (d, J ) 8.3 Hz, 2 H), 7.58 (dd, J ) 8.1,
1.5 Hz, 2 H), 7.39-7.23 (m, 5 H), 5.98 (dt, J ) 6.0, 1.9 Hz, 1
H), 4.96 (dt, J ) 6.0, 3.6 Hz, 1 H), 2.95 (m, 2 H), 2.47 (s, 3 H);
an NOE was observed for δ 7.58 (ortho-protons of PhSe) when
δ 2.95 (H-4) was irradiated and vice versa; 13C NMR (50 MHz)
δ 144.4, 139.9, 136.8, 136.5, 130.4, 129.7, 129.0, 128.8, 127.9,
127.4, 110.9, 102.7, 29.7, 21.7; MS m/z (relative intensity, %)
392 (6, M+), 91 (48), 57 (100); exact mass calcd for C18H16O3-
SSe 391.9888, found 391.9990.
Cycloa d d ition of Acetylen e 1 w ith (Tr im eth ylsilyl)-
m eth yl Azid e (14). Acetylene 1 (85 mg, 0.25 mmol) and 300
µL of (trimethylsilyl)methyl azide were stirred in 5 mL of ether
for 2 days at room temperature. Volatile material was then
evaporated in vacuo, and the crude mixture was separated by
chromatography (elution with hexanes-ethyl acetate, 5:1) to
afford 68 mg (58%) of 15 and 21 mg (18%) of 16.
(28) The large coupling constant of ca. J ) 7 Hz is assigned to the
5-bond coupling of the methylene protons at the 3-position with those
at the 6-position. Similar large couplings have been reported for other
1,4-cyclohexadienes: Durham, L. J .; Studebaker, J .; Perkins, M. J . J .
Chem. Soc., Chem. Commun. 1965, 456.

Reactions of 1-Phenylseleno-2-(p-toluenesulfonyl)ethyne
J . Org. Chem., Vol. 64, No. 20, 1999 7431
Com p ou n d 15: Rf 0.38; mp 103-108 °C; IR (film) 1335,
1304, 1293, 1162, 1151 cm-1; 1H NMR (200 MHz) δ 7.92 (d, J
) 8.4 Hz, 2 H), 7.65-7.59 (m, 2 H), 7.39-7.30 (m, 5 H), 4.01
(s, 2 H), 2.45 (s, 3 H), 0.13 (s, 9 H); an NOE was observed for
δ 7.92 (ortho-protons of Ts) when δ 4.01 (CH2Si) was irradiated
and vice versa; 13C NMR (50 MHz) δ 145.9, 137.3, 134.9, 130.1,
129.3, 129.1, 128.8, 128.6, 127.4, 126.5, 41.8, 21.7, -2.0; MS
m/z (relative intensity, %) 465 (19, M+), 73 (100); exact mass
calcd for C19H23N3O2SSeSi 465.0455, found 465.0431.
En e Rea ction of Acetylen e 1 w ith â-P in en e. Acetylene
1 (156 mg, 0.465 mmol) was dissolved in (1S)-â-pinene (1.0
mL, 6.3 mmol) in a sealed 5 mL reaction vial fitted with a
Teflon-lined cap. The solution was heated at 60 °C for 4 days.
The excess pinene was then evaporated in vacuo to yield a
brown oil which was chromatographed (elution with 5% ethyl
acetate-hexanes) to afford 23 (68.5 mg, 31%) as a colorless
oil along with recovered 1 (72 mg, 46%).
1
Com p ou n d 23: IR (neat) 1306, 1141 cm-1; H NMR (200
1
Com p ou n d 16: Rf 0.24; oil; IR (film) 1335, 1157 cm-1; H
MHz) δ 7.88 (d, J ) 8.3 Hz, 2 H), 7.58 (dd, J ) 7.3, 2.1 Hz, 2
H), 7.38-7.32 (m, 5 H), 7.20 (s, 1 H), 5.22 (m, 1 H), 2.92 (m, 2
H), 2.47 (s, 3 H), 2.25 (m, 1 H), 2.13 (m, 2 H), 1.99 (m, 2 H),
1.71 (m, 1 H), 1.16 (s, 3 H), 0.67 (s, 3 H); an NOE was observed
for δ 2.92 (bisallylic CH2) and δ 7.58 (ortho-protons of PhSe)
when the signal at δ 7.88 (ortho-protons of Ts) was irradiated;
irradiation of δ 7.20 (vinylic H gem to PhSe) produced an NOE
at δ 2.92 and 7.58; no NOE was observed between signals at
δ 7.58 and 2.92; 13C NMR (50 MHz) δ 144.6, 143.1, 140.2,
137.2, 134.4, 133.4, 132.4, 129.7, 129.3, 128.3, 127.6, 121.0,
44.9, 40.3, 39.4, 37.8, 31.8, 31.3, 26.0, 21.6, 20.8; MS m/z
(relative intensity, %) 472 (2, M+), 91 (56), 41 (100); exact mass
calcd for C25H28O2SSe 472.0979, found 472.0974.
Deselen iza tion of Cycloa d d u ct 23. Compound 23 (131
mg, 0.28 mmol) and NiCl2‚6H2O (198 mg, 0.83 mmol) were
stirred in 7 mL of methanol-THF (85:15) and cooled to 0 °C.
Sodium borohydride (150 mg, 3.97 mmol) was added in
portions over 5 min. (Caution: vigorous reaction with evolution
of hydrogen!) After 15 min the black suspension was filtered
through Celite, which was washed repeatedly with ether. The
combined ether fractions were washed with water and dried
(MgSO4), and the solvent was evaporated. Chromatography
of the residue (elution with hexanes-ethyl acetate, 20:1)
afforded 65 mg of the crude mixture of deselenized products
24a and 24b, produced in the ratio of 57:43, showing 1H NMR
signals attributed to 24a [δ 3.01 (m, CHTs) and 1.25 (d, J )
6.7 Hz, CH3CHTs)] and 24b [δ 4.99 (d, J ) 10.3 Hz, CdCH;
major stereoisomer) and 4.83 (d, J ) 10.2 Hz, CdCH; minor
stereoisomer), 3.82 (m, CHTs) and 1.42 (d, J ) 6.8 Hz, CH3-
CHTs)]. Double irradiation at δ 3.01 collapsed the doublet at
δ 1.25 to a singlet; irradiation at δ 1.25 collapsed the multiplet
at δ 3.01 to a crude triplet. Double irradiation at δ 3.82
collapsed the doublets at δ 4.99, 4.83 and 1.42 to singlets;
irradiation at δ 1.42 collapsed the multiplet at δ 3.82 to two
doublets at δ 3.86 and 3.81 (minor and major stereoisomers,
respectively, each with J ) 10.3 Hz).
NMR (200 MHz) δ 7.95 (d, J ) 8.4 Hz, 2 H), 7.28-7.18 (m, 7
H), 3.70 (s, 2 H), 2.40 (s, 3 H), 0.04 (s, 9 H); 13C NMR (50 MHz)
δ 144.8, 137.5, 131.9, 129.9, 129.7, 129.6, 128.9, 128.4, 128.3,
127.6, 41.0, 21.6, -2.2; MS m/z (relative intensity, %) 465 (11,
M+), 91 (73), 73 (100); exact mass calcd for C19H23N3O2SSeSi
465.0455, found 465.0495.
Cycloa d d ition of Acetylen e 1 w ith Dia zom eth a n e.
Acetylene 1 (37 mg, 0.11 mmol) was dissolved in 5 mL of ether,
and diazomethane was added dropwise until a yellow color
persisted. After 5 min, volatile material was evaporated and
the residue was purified by chromatography (elution with 33%
ethyl acetate-hexane) to afford 34 mg (81%) of homogeneous
cycloadduct 17 (or 18): mp 112-116 °C; IR (film) 3259, 3135,
1316, 1302, 1148 cm-1; 1H NMR (200 MHz) δ 7.95-7.86 (m, 3
H), 7.54-7.49 (m, 2 H), 7.40-7.28 (m, 5 H), 2.41 (s, 3 H); 13C
NMR (50 MHz) δ 144.1, 138.9, 137.8, 134.5, 129.8, 129.64,
129.55, 129.47, 129.0, 127.2, 125.9, 21.5; MS m/z (relative
intensity, %) 378 (100, M+), 91 (64); exact mass calcd for
C
16H14N2O2SSe 377.9944, found 377.9914.
When the reaction was repeated with excess diazomethane
for 3 h at room temperature, chromatography (elution with
33% ethyl acetate-hexane) afforded 69% of the major N-
methylated regioisomer 19 and 11% of the minor regioisomer
20.
Ma jor Isom er 19: Rf 0.37; mp 104-107 °C; IR (film) 1316,
1302, 1168, 1148 cm-1 1H NMR (400 MHz) δ 8.07 (s, 1 H),
;
7.90 (d, J ) 8.3 Hz, 2 H), 7.21-7.19 (m, 3 H), 7.14-7.10 (m, 2
H), 6.95 (d, J ) 7.7 Hz, 2 H), 3.76 (s, 3 H), 2.35 (s, 3 H); 13C
NMR (100 MHz) δ 144.0, 140.3, 139.1, 131.0, 129.7, 129.5,
129.3, 128.4, 128.3, 127.8, 127.7, 38.7, 21.5; MS m/z (relative
intensity, %) 392 (95, M+), 91 (75), 84 (100); exact mass calcd
for C17H16N2O2SSe 392.0102, found 392.0058. For the X-ray
crystal structure of 19, see the Supporting Information.
Min or Isom er 20: Rf 0.13; mp 116-119 °C; IR (film) 1348,
1314, 1302, 1153 cm-1 1H NMR (200 MHz) δ 7.95 (s, 1 H),
;
P r ep a r a tion of 3,4-Dim eth yl-3-cycloh exen on e (27). Cy-
cloadduct 3 (967 mg, 2.32 mmol) was dissolved in chloroform
(3 mL), m-CPBA (406 mg, 2.35 mmol) was added, and the
solution was stirred at room temperature for 20 min. The
reaction mixture was washed with K2CO3 and dried (MgSO4),
and the solvent was evaporated to give a colorless oil (997 mg),
which was suspended in methanol (2 mL). Sodium methoxide
in methanol (2.3 mL, 1 M) was added. The mixture was stored
at -20 °C for 24 h, and the resulting mixture containing 25
was poured into ether (10 mL), extracted with 10% hydrochlo-
ric acid, and washed with water. The organic layer was dried
(MgSO4), the solvent was evaporated, and the resulting yellow
oil was chromatographed (elution with hexanes and then 10%
ethyl acetate-hexanes) to give 26 (499 mg, 78%) as a colorless
oil that was used directly in the next step.
Compound 26 (472 mg, 1.70 mmol) was desulfonylated with
5% sodium amalgam (2.35 g, 5.11 mmol of Na) in the presence
of Na2HPO4 (965 mg, 6.80 mmol) in dry methanol-THF (7 mL,
1:1) by the procedure of Trost et al.30 to afford the known23a
compound 27 (156 mg, 74%) as an oil.
P r ep a r a tion of 5-Bicyclo[2.2.2]octen -2-on e (30). Cy-
cloadduct 4 (208 mg, 0.501 mmol) was dissolved in chloroform
(1 mL), and m-CPBA (104 mg, 0.603 mmol) was added. The
solution was stirred at room temperature for 20 min. The
reaction mixture was washed with K2CO3 solution and dried
(MgSO4), and the solvent was evaporated to give the corre-
7.86 (d, J ) 8.2 Hz, 2 H), 7.35-7.15 (m, 7 H), 3.89 (s, 3 H),
2.37 (s, 3 H); an NOE was observed for δ 7.95 (diazole ring
CH) when δ 3.89 (NMe) was irradiated and vice versa; 13C
NMR (50 MHz) δ 143.9, 138.8, 134.7, 132.8, 132.7, 129.4, 129.0,
128.9, 128.8, 127.6, 127.4, 39.8, 21.5; MS m/z (relative inten-
sity, %) 392 (100, M+), 157 (47), 91 (35); exact mass calcd for
C
17H16N2O2SSe 392.0102, found 392.0057.
Cycloa d d ition of Acetylen e 1 w ith 2,4,6-Tr im eth yl-
ben zon itr ile N-Oxid e (21). Acetylene 1 (275 mg, 0.820 mmol)
and N-oxide 21 (132 mg, 0.820 mmol) were stirred in 25 mL
of ether at room temperature for 24 h. The mixture was
concentrated in vacuo, and the crude product was separated
by chromatography (elution with hexanes-ethyl acetate, 5:1)
to afford 254 mg (63%) of the corresponding cycloadduct 22,29
which was recrystallized from ethyl acetate-hexane: Rf 0.48;
mp 120-124 °C; IR (film) 1323, 1304, 1159, 1135 cm-1 1H
;
NMR (200 MHz) δ 7.83 (dd, J ) 7.8, 1.8 Hz, 2 H), 7.48-7.40
(m, 3 H), 7.38 (d, J ) 8.4 Hz, 2 H), 7.16 (d, J ) 8.6 Hz, 2 H),
6.83 (s, 2 H), 2.42 (s, 3 H), 2.34 (s, 3 H), 1.72 (s, 6 H); 13C NMR
(50 MHz) δ 168.1, 160.3, 144.8, 139.8, 138.0, 137.7, 136.8,
130.1, 129.7, 129.4, 128.0, 127.6, 122.4, 122.2, 119.1, 21.6, 21.3,
19.6; MS m/z (relative intensity, %) 340 (64, M+ - PhSe), 157
(98), 155 (91), 91 (100), 77 (99); exact mass calcd for C19H18
-
NO3S (M+ - PhSe) 340.1007, found 340.1005. For the X-ray
crystal structure of 22, see the Supporting Information.
(29) The mother liquor contained a minor product that could not be
isolated in pure form, but that may be the other regioisomer: 1H NMR
(200 MHz) δ 8.08 (d, J ) 8.4 Hz), 6.71 (s), 2.49 (s), 2.26 (s), 1.72 (s).
(30) (a) Trost, B. M.; Verhoeven, T. R. J . Am. Chem. Soc. 1980, 102,
4743. (b) Trost, B. M.; Arndt, H. C.; Strege, P. E.; Verhoeven, T. R.
Tetrahedron Lett. 1976, 3477.

7432 J . Org. Chem., Vol. 64, No. 20, 1999
Back et al.
sponding selenoxide (216 mg, 100%) as a mixture of diaster-
eomers, obtained as white crystals. The latter product was
suspended in methanol (0.5 mL), and a solution of sodium
methoxide in methanol (500 µL, 1 M) was added. The mixture
was then refluxed for 30 min, poured into ether (10 mL), and
washed with water. The organic layer was dried (MgSO4), and
the solvent was evaporated in vacuo. The residual oil was
chromatographed (elution with 10% ethyl acetate-hexanes)
to afford 28 (132 mg, 91%) as white crystals: mp 125-127 °C
mmol) was added in portions over 5 min. (Caution: vigorous
reaction with evolution of hydrogen!) After 15 min the black
suspension was filtered through Celite, which was washed
repeatedly with ether. The combined ether fractions were
washed with water and dried (MgSO4), and the solvent was
evaporated. Chromatography of the residue (elution with 10%
ether-hexanes) afforded 47 mg (78%) of m-tolyl p-tolyl sulfone
(33) as white crystals: mp 114-115 °C (from ethanol) (lit.31
mp 116 °C); IR (CH2Cl2) 1301, 1150, 1103 cm-1; 1H NMR (200
MHz) δ 7.83 (d, J ) 8.4 Hz, 2 H), 7.75-7.72 (m, 2 H), δ 7.38-
7.28 (m, 4 H), δ 2.40 (s, 6 H); MS m/z (relative intensity, %)
246 (20, M+), 139 (100), 91 (32).
2-Me t h y l-3-(p -t o lu e n e s u lfo n y l)-2,5-b ic y c lo [2.2.2]-
octa d ien e (34). MeLi (357 µL, 1.38 M, 0.493 mmol) was added
to a suspension of cuprous benzeneselenolate (110 mg, 0.501
mmol) in dry THF (2 mL) at 0 °C under argon, and the solution
was stirred for 20 min at 0 °C. The mixture was cooled to -78
°C, and a solution of 4 (208 mg, 0.501 mmol) in dry THF (1
mL) was added dropwise over a period of 5 min. The mixture
was warmed to 0 °C and stirred for 2.5 h. The reaction was
quenched with 2 mL of NH4Cl solution and was stirred for an
additional 30 min. The suspension was poured into ether (15
mL), washed with NH4Cl solution, dried (MgSO4), and evapo-
rated. Chromatography of the residue (elution with 10% ethyl
acetate-hexanes) afforded 119 mg (87%) of 34 as a yellow oil:
IR (neat) 1292, 1147 cm-1; 1H NMR (200 MHz) δ 7.70 (d, J )
8.3 Hz, 2 H), 7.25 (d, J ) 8.4 Hz, 2 H), 6.25-6.21 (m, 2 H),
3.95-3.90 (m, 1 H), 3.51-3.47 (m, 1 H), 2.41 (s, 3 H), 2.32 (s,
3 H), 1.39-1.21 (m, 4 H); 13C NMR (200 MHz) δ 156.4, 143.5,
139.0, 136.7, 134.4, 132.5, 129.6, 126.9, 46.8, 38.6, 25.8, 23.8,
21.5, 17.7; MS m/z (relative intensity, %) 274 (5, M+), 246 (72),
91 (100); exact mass calcd for C16H18O2S 274.1028, found
274.1026.
(from ethanol); IR (CH2Cl2) 1299, 1141 cm-1 1H NMR (200
;
MHz) 7.75 (d, J ) 8.3 Hz, 2 H), 7.25 (d, J ) 8.4 Hz, 2 H), 6.46
(ddd, J ) 7.3, 6.1, 1.2 Hz, 1 H), 6.17 (ddd, J ) 7.4, 6.0, 1.6 Hz,
1 H), 4.17 (m, 1 H), 3.89 (m, 1 H), 3.78 (s, 3 H), 2.41 (s, 3 H),
1.51-1.36 (m, 4 H); 13C NMR (50 MHz) δ 169.2, 142.9, 140.7,
137.2, 130.9, 129.4, 129.2, 126.8, 56.8, 37.3, 37.2, 25.5, 24.6,
21.5; MS m/z (relative intensity, %) 290 (51, M+), 262 (85), 105
(100), 91 (74); exact mass calcd for C16H18O3S 290.0977, found
290.0995.
Compound 28 (160 mg, 0.551 mmol) was dissolved in THF
(1 mL), and 10% hydrochloric acid (1 mL) was added. The
mixture was stirred at room temperature for 1 h and was then
neutralized (Na2CO3), poured into ether (10 mL), and washed
with water and brine. The organic phase was dried (MgSO4)
and evaporated to give 29 (145 mg, 95%) as white crystals
consisting of a 1.4:1 mixture of diastereomers (NMR integra-
tion). The product was used in the next step without further
purification or attempts at separating the two diastereomers.
â-Keto sulfone 29 (207 mg, 0.749 mmol) was desulfonylated
as in the case of 26 to afford 69 mg (75%) of the known23b
compound 30 as an oil.
1,2-Dim eth yl-4-(p h en ylselen o)ben zen e (31). Cycload-
duct 3 (156 mg, 0.374 mmol) and potassium tert-butoxide (46
mg, 0.41 mmol) were refluxed for 4 h in 5 mL of tert-butyl
alcohol. The mixture was poured into ether (20 mL) and
washed with water, and the organic phase was dried (MgSO4)
and evaporated in vacuo. The brown residue was chromato-
graphed (elution with hexanes) to afford 84 mg (87%) of 31 as
a colorless oil: IR (CH2Cl2) 1576, 812, 746 cm-1; 1H NMR (200
MHz) δ 7.35-7.31 (m, 2 H), 7.25 (d, J ) 1.0 Hz, 1 H), 7.19-
7.13 (m, 4 H), 6.98 (d, J ) 7.8 Hz, 1 H), 2.17 (s, 3 H), 2.15 (s,
3 H); 13C NMR (50 MHz) δ 137.9, 136.4, 135.1, 132.3, 131.9,
131.6, 130.6, 129.2, 126.8, 126.7, 19.6, 19.5; MS m/z (relative
intensity, %) 262 (71, M+), 182 (100); exact mass calcd for
Rea ction of 7 w ith MeCu (SeP h )Li. MeLi (214 µL, 1.38
M, 0.295 mmol) was added to a suspension of cuprous
benzeneselenolate (65 mg, 0.30 mmol) in dry THF (2 mL) at 0
°C under argon, and the solution was stirred for 20 min. The
mixture was cooled to -78 °C, and a solution of 7 (121 mg,
0.300 mmol) in dry THF (1 mL) was added dropwise over a
period of 5 min. The mixture was warmed to 0 °C and stirred
for 2.5 h. The reaction was worked up as in the preceding
experiment to give a yellow oil, which was chromatographed
(elution with 10% ethyl acetate-hexanes) to afford 56 mg
(78%) of 33 as white crystals with mp 112-114.5 °C (from
C
14H14Se 262.0261, found 262.0243.
1
ethanol) (lit.31 mp 116 °C), identical (TLC and IR and H NMR
P r ep a r a tion a n d Deselen iza tion of 2-P h en ylselen o-3-
(p-tolu en esu lfon yl)tolu en e (32). Cycloadduct 7 (202 mg,
0.501 mmol) was dissolved in chloroform (1 mL), and m-CPBA
(104 mg, 0.603 mmol) was added. The solution was stirred
at room temperature for 20 min and was then washed with
K2CO3 solution and dried (MgSO4), and the solvent was
evaporated to give a white residue. It was dissolved in THF
(1 mL) containing triethylamine (70 µL, 0.50 mmol) and
refluxed for 12 h. The solution was poured into ether (20 mL),
washed with water, and dried (MgSO4), and the solvent was
evaporated. Chromatography (elution with 5% ethyl acetate-
hexanes) afforded 189 mg (94%) of 32: IR (CH2Cl2) 1312, 1303,
spectra) with the sample prepared from the deselenization of
32.
Ack n ow led gm en t. We thank the Natural Sciences
and Engineering Research Council of Canada (NSERC)
for financial support, and Dr. R. Yamdagni, Ms. D. Fox,
and Ms. Q. Wu for mass spectra and elemental analyses.
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra of new compounds not having combustion analyses,
ORTEP diagrams of compounds 19 and 22, and tables of
crystal data, bond lengths and angles, atomic coordinates, and
anisotropic thermal parameters. This material is available free
of charge via the Internet at http://pubs.acs.org.
1
1151 cm-1; H NMR (200 MHz) δ 8.37 (m, 1 H), 7.84 (d, J )
8.3 Hz, 2 H), 7.53-7.49 (m, 2 H), 7.10 (d, J ) 8.4 Hz, 2 H),
7.05-6.93 (m, 3 H), 6.62 (dd, J ) 8.0, 1.5 Hz, 2 H), 2.27 (s, 6
H); 13C NMR (50 MHz) δ 146.5, 145.8, 143.5, 137.7, 135.5,
132.3, 129.5, 129.0, 128.94, 128.90, 128.9, 128.8, 128.2, 126.1,
23.6, 21.4; MS m/z (relative intensity, %) 402 (27, M+), 165
(100), 91 (94); exact mass calcd for C20H18O2SSe 402.0196,
found 402.0204.
Compound 32 (100 mg, 0.249 mmol) and NiCl2‚6H2O (416
mg, 1.75 mmol) were dissolved in 2.5 mL of methanol and THF
(85:15) and cooled to 0 °C. Sodium borohydride (199 mg, 5.25
J O990730T
(31) Dictionary of Organic Compounds, 6th ed.; Cadogan, J . I. G.,
Ley, S. V., Pattenden, G., Raphael, R. A., Rees, C. W., Eds.; Chapman
and Hall: London, 1996; Vol. 3, entry D-0-09403. The mp of the o-tolyl
p-tolyl sulfone isomer of 33 is 60 °C and therefore considerably lower;
see entry D-0-0941.