The first isolation and characterization of sulfonylbuta-1,3-diynes

Article abstract of DOI:10.1039/b203913n

We have isolated the sulfonylbuta-1,3-diynes 3 and 5 as colorless prisms, which demonstrate unprecedented dimerization. Furthermore, the reactions of 3 and 5 with alkoxides or buta-1,3-dienes were examined and the products obtained were either sulfonyl-β-alkoxybut-1-en-3-ynes 16a-e, β-alkoxybut-3-en-1-ynes 17a-d or the cycloadducts 23 and 24a,b.

Full text of DOI:10.1039/b203913n

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The first isolation and characterization of sulfonylbuta-1,3-diynes
Mitsuhiro Yoshimatsu,*a Kasumi Oh-Ishi,a Genzoh Tanabeb and Osamu Muraokab
a Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1,
Gifu 501-1193, Japan
1
b School of Pharmacy, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502, Japan
Received (in Cambridge, UK) 22nd April 2002, Accepted 7th May 2002
First published as an Advance Article on the web 22nd May 2002
We have isolated the sulfonylbuta-1,3-diynes 3 and 5
as colorless prisms, which demonstrate unprecedented
dimerization. Furthermore, the reactions of 3 and 5 with
alkoxides or buta-1,3-dienes were examined and the pro-
ducts obtained were either sulfonyl-ꢀ-alkoxybut-1-en-
3-ynes 16a–e, ꢀ-alkoxybut-3-en-1-ynes 17a–d or the
cycloadducts 23 and 24a,b.
find any evidence of the conjugated system. The structure of 7a
was elucidated by single crystal X-ray analysis as shown in
Fig. 1.7,8 The sulfone 3 was heated at 50 ЊC without a solvent to
Acetylenic sulfones are extremely useful as Michael acceptors
with suitable heteroatom nucleophiles such as alcohols, amines
and thiols. Their reactions provide β-heteroatom-substituted
vinylic sulfones, some of which are easily transformed into a
wide variety of heterocycles, natural products and bioactive
compounds.1 Furthermore, acetylenic sulfones can undergo
cycloaddition reactions, including [4ϩ2], [2ϩ2] and [3ϩ2] pro-
cesses to give many types of cyclic compounds. On the other
hand, sulfonylbuta-1,3-diynes, which have a longer conjugated
system, have received little attention in synthetic organic chem-
istry. Several reports concerning the preparation and reactions
of sulfonylbuta-1,3-diynes have been published: one reports
that buta-1,3-diynyl phenyl sulfone reacts to form a poly-
acetylene,2 while another describes the 1,4-bis(perfluoro-
alkylsulfonyl)buta-1,3-diynes, formed in situ, reacting with
cyclopentadiene to afford the 4 ϩ 2 cycloadducts.3 To our
knowledge sulfonylbuta-1,3-diynes have not been previously
isolated. However, if they could be isolated, the sulfonylbuta-
1,3-diynes would be expected to undergo transformations into
other useful compounds via regioselective Michael addition
reactions with nucleophiles, or cycloaddition reactions with
buta-1,3-dienes. We have succeeded in isolating and characteris-
ing the sulfonylbuta-1,3-diynes 3 and 5 and observed an
unprecedented dimerization of these sulfonylbuta-1,3-diynes.
We report herein these results.
Fig. 1 ORTEP drawing of 7a.
First, we prepared the buta-1,3-diynes as shown in Scheme 1.
Scheme 2 Conditions: i, neat, rt–50 ЊC.
give the dimer 7a in 47% yield (Scheme 2). The rate of trans-
formation of the sulfonylocta-1,3-diyne 4 to the corresponding
dimer 7b was fast and the yield was high. In order to isolate the
sulfonylbuta-1,3-diynes as stable crystals, we prepared 2,4,6-
trimethylphenyl-5,5-dimethylhexa-1,3-diynyl sulfone 5 by the
same method. Sulfonylbuta-1,3-diyne 5 was isolated in the form
of stable crystalline prisms (mp 70–72 ЊC).9 Furthermore, we
attempted the preparation of the n-butyl derivative 6. The rate
of dimerization of the sulfonylbuta-1,3-diyne 6 is slower than
that of 4; however, 6 transformed into the dimer 7d at room
temperature. In order to clarify the mechanism of this unique
dimerization of the sulfonylbuta-1,3-diynes, we carried out the
dimerization reaction of 3 with a galvinoxyl radical.† The
dimer 7a was formed in low yield and the other products 8 and
Scheme 1 Reagents and conditions: i, EtMgBr, 0 ЊC, RCCCHO;
ii, PCC, CH2Cl2: iii, EtN(iPr)2, (CF3SO2)2O, Ϫ78 ЊC.
Aryl methyl sulfone was treated with EtMgBr and prop-2-ynals,
and the following oxidation with PCC afforded the ynones 2a–d
in moderate yields. Treatment of 2a with Tf2O–Hunig’s base4
gave the corresponding sulfonylbuta-1,3-diyne 3 in 75% yield.5
However, this sulfone is labile at room temperature and
gradually changes to the dimer 7a. The proposed structure of
7a was based upon its spectral data and the molecular formula
C28H28O2S.6 The 1H NMR spectrum shows two tert-butyl
groups at δ 1.23 and 1.33 ppm. The 13C NMR spectrum exhibits
six singlets at δ 64.25, 69.97, 78.34, 89.02, 94.60 and 98.82 ppm
which are due to the acetylenic carbons. However, we could not
DOI: 10.1039/b203913n
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radical 14. Tandem reactions with 12 provides the polyacetyl-
ene. Two possible routes to the dimer 17 exist. One is via a direct
1,2-migration of the ethynyl group of 14 and successive dearyl-
sulfonylation. Next, the aryl radical forms by the direct loss of
sulfur dioxide from the arylsulfonyl radical. However, it is
unusual for the arylsulfonyl radical to afford an aryl radical
under the mild reaction conditions used here. Therefore an
alternative path is predicted in which the alkylidene carbene 16
is formed from 14 with the formation of the aryl radical
and then loss of sulfur dioxide. The final 1,2-migation provides
the product 17 and the aryl radical thus formed further reacts
with 12.
In order to characterize the new sulfonylbuta-1,3-diynes we
conducted reactions between the sulfones and various nucleo-
philes. The reaction of 3 with NaOMe at 0 ЊC gave 2-methoxy-
5,5-dimethyl-1-(phenylsulfonyl)hex-1-en-3-yne (18a)13 (32%)
and 4-methoxy-5,5-dimethyl-1-(phenylsulfonyl)hex-3-en-1-yne
(19a)14 (13%), respectively. The regioselectivities of the prod-
ucts were elucidated by NOE enhancements (Fig. 3). Irradiation
Fig. 2
9 were trapped by the galvinoxyl radical (Fig. 2).10 Sulfone 3 was
found to be more stable in CHCl3, rather than in the pure form
and the rate of the dimerization was distinctly repressed. We
performed a crossover experiment as shown in Scheme 3. A
Fig. 3 NOE enhancement of 11a and 12a.
of the olefinic protons of 18a at δ 6.30 ppm increased the inten-
sity of the tert-butyl protons (2%) but not that of the methoxy
protons. NOE enhancements of the product 19a were observed
between the methoxy protons and the tert-butyl protons (4%);
between the methoxy protons and the olefinic protons (14%).
These results show that the addition of alkoxides to sulfonyl-4-
tert-butylbuta-1,3-diynes mainly occurs at the β-position to
the sulfonyl group. Reactions of 3 with other alkoxides also
provided two kinds of adducts 18b–e and 19b–d (Scheme 5).
However, the regioselectivities were found to be higher than
that for the reaction with NaOMe. On the other hand, the reac-
tion of the n-butyl derivative 6 with NaOMe gave two kinds of
products: one is the δ-adduct 20 and another is β-methoxy-
α,β-unsaturated ketone 21, which results from the hydration of
the β,δ-dimethoxybuta-1,3-diene. These results show that the
reactions of buta-1,3-diyne with nucleophiles first occur at
the β-position to the sulfonyl group. The reactions of 3 with
amides also afforded the β-adducts 22a,b (Scheme 6).
Scheme 3 Conditions: i, neat, 50 ЊC, 30 min.
mixture of diynes 3 and 5 were heated at 50 ЊC and mainly
formed the dimers 10 or 11 (which have a molecular ion peak at
m/z 470) and 7c.11 These results show that the dimerization
proceeds via a bimolecular mechanism. Thus, we propose a
possible mechanism for the dimerization of the sulfonylbuta-
1,3-diynes as shown in Scheme 4.12 First, the initiator adds to 12
at the β-position to the sulfonyl group to provide the vinyl rad-
ical 13a,b, which subsequently adds to 12 to afford the dienyl
Scheme 4
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Scheme 5 Reagents and conditions: i, RONa, ROH, 0 ЊC.
ArH); 13C NMR δ 28.75 (s), 29.38 (s), 30.29 (q × 3), 30.49 (q × 3),
64.25 (s), 69.97 (s), 78.34 (s), 89.02 (s), 94.60 (s), 98.82 (s), 122.36 (s),
128.25 (d × 2), 128.37 (d × 2), 128.95 (d × 2), 129.08 (d × 2), 130.39
(d), 133.66 (d), 137.58 (s), 140.73 (s), 140.87 (s); MS m/z 428 (Mϩ).
Anal. calcd for C28H28O2S: C, 78.47; H, 6.59. Found: C, 78.14; H,
6.51%.
7 Crystal data for 7a: C28H28O2S,
M = 428.59, monoclinic,
Scheme 6 Reagents and conditions: i, R1R2NLi, THF, 0 ЊC.
a = 15.837(3) Å, b = 10.389(2) Å, c = 15.924(3) Å, β = 104.02(1)Њ,
V = 2541.9(8) Å3, T = 296 K, space group P21/a, Z = 4, µ(Mo-Kα) =
1.47 cmϪ1, DC = 1.120 mg mϪ3, 6395 reflections collected (Rigaku
AFC5R diffractometer) of which 6180 were unique (Rint = 0.031)
and 2219 were observed [I > 3.00σ(I )]. Solved by direct methods
(ORIENT) (see ref. 3) and refined by full-matrix least squares
(teXsan) on F of all unique data to give R = 0.054, Rw = 0.064.
CCDC reference number 179796. See http://www.rsc.org/suppdata/
p1/b2/b203913n/ for crystallographic files in .cif or other electronic
format.
8 R. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman,
S. Garcia-Granda, R. O. Gould, J. M. M. Smits and C. Smykalla,
The DIRDIF program system, Technical Report of the Crystal-
lography Laboratory, University of Nijmengen, The Netherlands,
1992.
9 Data for 5: colorless prisms, mp 70–72 ЊC (dec.); IR νmax/cmϪ1 2210
(acetylene), 1330, 1160 (SO2); 1H NMR δ 1.17 (9H, s, Me × 3), 2.31
(3H, s, Me), 2.70 (6H, s, Me × 2), 6.97 (2H, s, ArH); 13C NMR
δ 21.21 (q), 22.54 (q × 2), 28.44 (s), 28.55 (q × 3), 61.66 (s), 71.88 (s),
75.98 (s), 99.23 (s), 132.30 (d × 2), 135.33 (s), 140.11 (s × 2), 144.36
(s); MS m/z 288 (Mϩ). Anal. calcd for C17H20O2S: C, 70.80; H, 6.99.
Found: C, 71.00; H, 7.19%.
Scheme 7 Reagents and conditions: i, cyclohexa-1,3-diene, sealed tube,
100 ЊC, 1 h; ii, furan, sealed tube, 100 ЊC, 30 min.
We further investigated the cycloadditions of 3 or 4 with
various dienes as shown in Scheme 7. First we examined the
reaction of 3 with hexa-1,3-diene in a sealed tube at 100 ЊC.
The cycloadduct 23 was exclusively obtained in good yield.15
The reaction with furan gave the bicyclic compound 24a,
accompanied by the dimer 7a. The mesityl sulfone 4 also
afforded the adduct 24c.
1
10 Data for 8: a brown oil, IR νmax/cmϪ1 1360, 1160 (SO2); H NMR
δ 1.32 (9H, s, Me × 3), 1.34 (9H, s, Me × 3), 1.38 (18H, s, Me × 6),
7.03–7.05 (1H, m, ArH), 7.18 (1H, s, olefinic H), 7.41 (2H, s, ArH),
7.49–7.50 (1H, m, ArH), 7.55–7.59 (2H, m, ArH), 7.66–7.71 (1H,
m, ArH), 7.88–7.91 (2H, m, ArH); 13C NMR δ 29.74 (q × 3), 29.88
(q × 3), 32.94 (q × 6), 35.75 (s), 37.33 (s × 2), 127.89 (d), 128.67
(d × 2), 129.34 (d × 2), 130.40 (d × 2), 132.08 (s), 133.39 (s), 134.28
(d), 135.43 (d), 136.83 (s), 142.44 (d), 145.96 (s), 147.98 (s), 149.76
(s), 186.75 (s); high-resolution mass calcd for C35H42O4S: 558.2803,
found m/z 558.2825. Data for 9: a brown oil, IR νmax/cmϪ1 2200
(acetylene), 1320, 1140 (SO2); 1H NMR δ 1.16 (18H, s, Me × 6), 1.24
(9H, s, Me × 3), 1.30 (9H, s, Me × 3), 1.47 (9H, s, Me × 3), 5.87 (2H,
s, ArH), 5.91 (1H, s, olefinic H), 6.60–6.67 (1H, m, ArH), 7.04–7.05
(1H, m, ArH), 7.51–7.55 (2H, m, ArH), 7.62–7.66 (1H, m, ArH),
7.99–8.02 (2H, m, ArH); MS m/z 772 (Mϩ).
Acknowledgements
Support by the Ministry of Education, Science and Culture,
Japan, for part of this work is gratefully acknowledged.
References
† The IUPAC name for galvinoxyl is 2,6-di-tert-butyl-α-(3,5-di-tert-
butyl-4-oxocyclohexa-2,5-dien-1-ylidene)-p-tolyloxyl.
11 Data for 10 or 11: a colorless oil, IR νmax/cmϪ1 2220 (acetylene),
1340, 1160 (SO2); 1H NMR δ 1.18 (9H, s, Me × 3), 1.26 (9H, s,
Me × 3), 2.03 (6H, s, Me × 2), 2.25 (3H, s, Me), 6.80 (2H, s, ArH),
7.53–7.57 (2H, m, ArH), 7.62–7.66 (1H, m, ArH), 8.07–8.11 (2H, m,
ArH); MS m/z 470 (Mϩ).
12 J. Grong and P. L. Fuchs, J. Am. Chem. Soc., 1996, 118, 4486.
13 Data for 18a: mp 58–63 ЊC, colorless prisms; IR νmax/cmϪ1 2200
(acetylene), 1330, 1160 (SO2); 1H NMR δ 1.24 (9H, s, Me × 3), 4.00
(3H, s, OMe), 6.30 (1H, s, olefinic H), 7.52–7.56 (2H, m, ArH), 7.61–
7.65 (1H, m, ArH), 7.90–7.92 (2H, m, ArH); 13C NMR δ 28.66 (s),
30.51 (q × 3), 61.95 (q), 71.59 (s), 99.40 (d), 111.08 (s), 128.72
(d × 2), 129.25 (d × 2), 133.98 (d), 138.23 (s), 160.68 (s); HRMS
calcd for C15H18O3S: 278.0977; found m/z 278.0948.
14 Data for 19a: mp 66–69 ЊC, E : Z = 83 : 17, colorless prisms; IR
νmax/cmϪ1 2200 (acetylene), 1300, 1140 (SO2); 1H NMR δ 1.25 (s,
(Z)-Me), 1.31 (s, (E)-Me), 3.67 (s, (E)-OMe), 3.76 (s, (Z)-OMe),
5.82 (s, (Z)-olefinic H), 5.98 (s, (E)-olefinic H), 7.49–7.52 (m, ArH),
7.56–7.59 (m, ArH), 7.96–7.99 (m, ArH); 13C NMR of (E)-19a
δ 28.49 (s), 30.06 (q × 3), 56.97 (q), 70.76 (s), 110.83 (d), 111.23 (s),
1 Review for acetylenic sulfone: T. G. Back, Tetrahedron, 2001, 57,
5263.
2 K. Aratani, Y. Tomioka, S. Komura and I. Ueno, (Jpn. Kokai
Tokkyo Koho) JP 11218763, 1999 (Chem. Abstr., 1999, 131, 163–455).
3 F. Massa, M. Hanack and L. R. Subramanian, J. Fluorine Chem.,
1982, 19, 601.
4 M. C. Clasby and D. Craig, Synlett, 1992, 825.
5 Data for 3: colorless oil, IR νmax/cmϪ1 2210 (acetylene), 1330, 1160
1
(SO2); H NMR δ 1.23 (9H, s, Me × 3), 7.31–7.74 (3H, m, ArH),
7.96–8.02 (2H, m, ArH); 13C NMR δ 28.51 (s), 29.77 (q × 3), 61.44
(s), 70.67 (s), 100.26 (s), 111.08 (s), 127.53 (d × 2), 129.59 (d × 2),
133.71 (s), 134.61 (d), 141.37 (s); MS m/z 246 (Mϩ). Anal. calcd for
C14H14O2S: C, 68.27; H, 5.73. Found: C, 68.12; H, 5.78%.
6 Data for 7a: colorless needles, mp 168–171 ЊC; IR νmax/cmϪ1 2210
(acetylene), 1330, 1160 (SO2); 1H NMR δ 1.23 (9H, s, Me × 3), 1.33
(9H, s, Me × 3), 7.26–7.37 (3H, m, ArH), 7.52–7.56 (2H, m, ArH),
7.61–7.65 (1H, m, ArH), 7.72–7.75 (2H, m, ArH), 8.06–8.09 (2H, m,
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127.28 (d × 2), 128.96 (d × 2), 132.92 (d), 143.34 (s), 152.15 (s); MS
m/z 278 (Mϩ). Anal. calcd for C15H18O3S: C, 64.72; H, 6.51. Found:
C, 64.52; H, 6.51%.
6.27 (2H, m, olefinic H), 7.47–7.51 (2H, m, ArH), 7.55–7.60 (1H, m,
ArH), 7.89–7.93 (2H, m, ArH); 13C NMR δ 23.91 (t), 25.80 (t), 28.61
(s), 30.54 (q × 3), 38.18 (d), 46.69 (d), 75.03 (s), 112.75 (s), 127.19 (d
× 2), 128.92 (d × 2), 132.95 (d), 133.08 (d), 133.54 (d), 139.04 (s),
141.68 (s), 144.95 (s); MS m/z 326 (Mϩ). Anal. calcd for C20H22O2S:
C, 73.58; H, 6.79. Found: C, 73.26; H, 6.75%.
15 Data for 23: colorless prisms, mp 82–84 ЊC, IR νmax/cmϪ1 2220
(acetylene), 1310, 1140 (SO2); 1H NMR δ 1.30 (9H, s, Me × 3), 1.31–
1.47 (4H, m, CH2), 3.73 (1H, br s, CH), 4.23 (1H, br s, CH), 6.23–
1416
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