The Hetero-Diels-Alder Addition of Sulfur Dioxide: The Pseudo-Chair Conformation of a 4,5-Dialkylsultine

Article abstract of DOI:10.1002/chem.200304932

Even unsubstituted butadiene adds to sulfur dioxide in the hetero-Diels-Alder mode more rapidly than in the chelotropic mode. The sultine can be observed in equilibrium with the diene and the sulfur dioxide only at low temperature and in the presence of CF₃COOH. Crystals of 4,5-dialkyl-sultine resulting from the SO₂ addition to 1,2-dimethylidenecyclohexane have been obtained at -100°C and analyzed by X-ray diffraction. Quantum chemical calculations have shown that hyperconjugative interactions within the sulfinyl moiety are responsible for the anomeric effects observed in sultines that prefer pseudo-chair conformations with pseudo-axial S=O bonds.

Full text of DOI:10.1002/chem.200304932

FULL PAPER
The Hetero-Diels ± Alder Addition of Sulfur Dioxide: The Pseudo-Chair
Conformation of a 4,5-Dialkylsultine
[
a]
[a]
[a]
[a]
[b]
Dean Markovic, Elena Roversi, Rosario Scoppelliti, Pierre Vogel,* Rub e¬ n Meana,
[
b]
and Jos e¬ A. Sordo*
Abstract: Even unsubstituted butadiene adds to sulfur dioxide in the hetero-Diels ±
Alder mode more rapidly than in the chelotropic mode. The sultine can be observed
in equilibrium with the diene and the sulfur dioxide only at low temperature and in
the presence of CF COOH. Crystals of 4,5-dialkyl-sultine resulting from the SO
addition to 1,2-dimethylidenecyclohexane have been obtained at À1008C and
analyzed by X-ray diffraction. Quantum chemical calculations have shown that
hyperconjugative interactions within the sulfinyl moiety are responsible for the
anomeric effects observed in sultines that prefer pseudo-chair conformations with
pseudo-axial SˆO bonds.
Keywords: ab initio calculations ¥
3
2
conformation
cycloadditions
sulfur
analysis
heterocycles
¥
¥
¥
Introduction
sultines in the solution were inferred from their NMR
data.[
1, 3 , 4, 7]
For the first time we have been able to recrystal-
Mono- and 2,3-dialkylbuta-1,3-dienes, which can adopt a s-cis-
conformation, add to sulfur dioxide below À508C giving the
corresponding [1,2]oxathiin-3-oxides (sultines) that are un-
stable above À408C. The hetero-Diels ± Alder additions are
lize sultine 2 at À1008C (Scheme 1). We report now the first
[1±3]
faster than expected chelotropic additions.
Except for 1,2-
dimethylidenecycloalkanes,[
3, 4]
the reaction requires promo-
Scheme 1.
tion by a protic or Lewis acid. With (Z)- and (E)-1-fluoro-
methylidene)-2-methylidene-3,4-dihydronaphthalene, the
X-ray analysis of a non-fluorinated sultine. We also report a
detailed computational analysis of the conformations which
can be adopted by this sultine. The conformation observed for
the crystalline sultine 2 was in fact found to be the most stable.
We have now established that:
corresponding 6-fluorosultines have been recrystallized at
À1008C and X-ray crystallography has shown sofa confor-
mations with oxygen of the ring lying in average plane of the
four carbon atoms and the SˆO bond being either in a pseudo-
equatorial[ or a pseudo-axial position. For simple non-
fluorinated sultines, quantum chemical calculations predicted
pseudo-chair conformations with the SˆO bond preferring
5]
[6]
1
) the pseudo-chair is the more stable conformation of 1,2-
dialkylsultine 2,
2
3
) the S O bond prefers a pseudo-axial position,
) pseudo-chair conformation of the sultine ™communicates∫
with the pseudo chair of the cyclohexene unit in 2,
) anomeric effects are analyzed in terms of hyperconjugative
interactions.
ˆ
pseudo-axial positions.[ Structures and conformations of the
7]
[
a] Prof. Dr. P. Vogel, D. Markovic, Dr. E. Roversi, Dr. R. Scoppelliti
Institute of Molecular and Biological Chemistry
Swiss Institute of Technology, BCH
4
1
015 Lausanne-Dorigny (Switzerland)
We report also for the first time that
Fax : (‡41)21-693-93-75
5
) butadiene itself adds slowly to SO in the presence of
2
E-mail: pierre.vogel@epfl.ch
CF COOH equilibrating with the parent sultine 3 at
3
[
b] Prof. Dr. J. A. Sordo, R. Meana
À408C.
Laboratorio de QuÌmica Computacional
Departamento de QuÌmica FÌsica y AnalÌtica
Universidad de Oviedo, Oviedo, Principado de Asturias (Spain)
Fax : (‡34)98-523-78-50
Theoretical Methods
E-mail: jasg@correo.uniovi.es
Supporting information for this article is available on the WWW under
http://www.chemeurj.org or from the author. Tables S4 ± S17, Fig-
ures S3± S6; X-ray analysis and calculations details.
The potential energy surface for the hetero-Diels ± Alder
addition of sulfur dioxide to 2,3-dialkylbuta-1,3-dienes was
Chem. Eur. J. 2003, 9, 4911 ± 4915
DOI: 10.1002/chem.200304932
¹ 2003Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4911

P. Vogel, J. A. Sordo et al.
FULL PAPER
explored at the B3LYP/6-31G(d) level of theory,[8] which has
been shown to provide reliable results on this type of
systems.[
Results and Discussion
3, 9]
Homochiral crystals of 2 ¥ SO were obtained by reaction of
2
diene 1[ in a 1:3.3 mixture of SO /MeOH at À788C and
16]
The location of the minima on the potential energy surface
was performed by means of standard algorithms as imple-
mented in the GAUSSIAN 98 package of programs.[ All
stationary points located were characterized by computing the
Hessian matrix and by checking the sign of the corresponding
eigenvalues. This allowed us to perform the thermochemistry
analysis using the ideal gas, rigid rotor, and harmonic
oscillator approximations.[
2
[17]
cooling to À1008C. X-ray diffraction at 140 K (Figure 1)
showed that 2 exhibits a pseudo-chair conformation for the
10]
11]
The solvation effects were estimated by performing single-
point B3LYP/6-31G(d) calculations with the self-consistent
reaction field (SCFR) Onsager model, in which the solvent is
[
12, 13]
represented by a dielectric constant.
To obtain results
applicable at the experimental concentration,[ we computed
the Gibbs free energies choosing the standard state in
accordance with the condensed phase experimental condi-
tions (p ˆ 272).
14]
In order to estimate the importance of hyperconjugative
interactions on the stabilization of structures, the natural bond
orbital (NBO)[ analysis was used. In the NBO method, the
atomic orbital basis set is orthogonalized and the canonical
delocalized Hartree ± Fock (HF) molecular orbitals are trans-
formed into localized hybrids (NBOs). The filled NBOs
describe covalency effects in molecules while unoccupied
NBOs are used to describe noncovalency effects. Among the
latter, the most important are the antibonds. Small occupan-
cies of these antibonds correspond, in HF theory, to irredu-
cible departures from the idealized Lewis picture and thus to
small noncovalent corrections to the picture of localized
covalent bonds. The energy associated with the antibonds can
be numerically assessed by deleting these orbitals from the
basis set and recalculating the total energy to determine the
associated variational energy lowering. For a X-Y-Z system,
the NBO deletion procedure allows one to compute the
energy (EXYZ) after zeroing the off-diagonal Fock matrix
elements connecting the lone pairs n on X with the YÀZ s*
Figure 1. Ball and stick representation of (S)-1,4,5,6,7,8-hexahydro-
benzo[d][1,2]oxathiin-3-oxide in 2 ¥ SO .
2
15]
cyclohexane and the sultine units. Both pseudo-chairs have
the pseudo P chirality with respect to the pseudo C axis.
2
Importantly, the SˆO bond resides in a pseudo-axial position.
Bond lengths involving sulfur atom are SÀC 1.847(5) ä, SˆO
1.520(4) ä and SÀO 1.655(4) ä. Typical distorsion from
tetrahedral geometry may be reflected by the O1ÀSÀC4 bond
angle of 98.1(2)8. The distances reflect an electronic delocal-
isation occurring in the OÀSˆO system. The crystal packing
shows CÀH ¥¥¥ O hydrogen bonds (C ¥¥¥ O 3.486(7) ä, CÀH ¥¥¥
O 1578). An important feature of the crystal packing is the
weak interaction between the exocyclic SˆO group and the
SO molecules. Each oxygen atom interacts with two sulfur
2
atoms (O ¥¥¥ S 2.841(4), 2.850(4) ä). These interactions are
below the sum of the van der Waals radii for these two atoms
(3.32 ä)[ and form an infinite one-dimensional chain along
the base vector [100] (see Supporting Information).
18]
antibonds. The difference E À E
is the energy corre-
total
XYZ
15]
[
sponding to the n ! s* interactions.
The six minima conformations of 1,2-dialkylsultine 2
located on the potential energy hypersurface are collected
in Figure 2. Such structures correspond to the three con-
formers C2, B2, S2 and their ™diastereomeric species∫ C2',
B2', S2', in which the sultine adopts a pseudo-chair (C)
conformation with pseudo-axial SˆO bond, a boat conforma-
tion (B) with pseudo-axial SˆO bond, and another pseudo-
chair conformation (S) with pseudo-equatorial SˆO bond (see
Abstract in French: Pour la premiõre fois on montre que le
dioxyde de soufre et le butadiõne s×ÿquilibrent avec le 2-oxyde
de [1,2]oxathiine (sultine 3 non-substituÿe) en prÿsence de
CF COOH. Les calculs quantiques B3LYP/6-31G(d) prÿ-
3
voient qu×une sultine non-fluorÿe adopte une conformation
pseudo-chaise avec la liaison exocyclique SˆO en position
further details of the calculations in the Supporting Informa-
tion).
pseudo-axiale. Ce conformõre est estimÿe√tre plus stable que les
conformõres bateaux ou pseudo-chaises avec la liaison SˆO
In all these conformers the cyclohexene moiety adopts
pseudo-chair conformations. Table 1 gives the most represen-
tative geometrical parameters for C2 as computed at the
B3LYP/6-31G(d) level. Comparison with the corresponding
experimental values shows the reliability of the level of theory
employed. The calculated relative (to reactants) enthalpies
pseudo-equatioriale. Les interactions n(S) ! s*(O-C) et
n(O) ! s*(SˆO) jouent un r o√ le dÿcisif dans la stabilitÿ du
conformõre pseudo-chaise avec SˆO exocyclique en position
pseudo-axiale. Ces prÿdictions sont verifiÿes par la structure
crystalline ‡ À1008C du 3-oxyde de (S)-1,4,5,6,7,8-hexahydro-
benzo[d]-[1,2]oxathiine (sultine 2 rÿsultant de l×addition
hetero-Diels ± Alder du 1,2-dimethylidenecyclohexane) ‡ basse
tempÿrature. C×est la premiõre fois qu×une sultine non-fluorÿe a
ÿtÿ crystallisÿe et caractÿrisÿe par diffraction des rayons X.
for the reaction 1‡SO > 2 are given in Table 2. They show
2
that conformer C2, which corresponds to that found in the
crystalline state with 2 ¥ SO , is the most stable. The calcu-
2
À1
lations predict that C2' is 0.6 kcalmol less stable than C2,
4912
¹ 2003Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 4911 ± 4915

Hetero-Diels ± Alder Addition
4911±4915
stable than the pseudo-chair
conformers C2 and C2' with
pseudo-axial SˆO bonds. Inter-
estingly, the boat conformers
B2 and B2' with pseudo-axial
SˆO bond are only 1 ± 2
À1
kcalmol less stable than C2
and C2'. Applying the natural
bond orbital (NBO)[ analysis
we obtain the different hyper-
15]
conjugative
contributions
shown in Table 3.
Interestingly, the total contri-
bution (n ! s*) is higher in the
boat conformers B2 and B2'
than in the pseudo-chair con-
formers C2 and C2'; this sug-
gests that the latter result from
competition between stabiliz-
ing anomeric effects and avoid-
ed eclipsing interactions (steric
effect). The calculations show
that pseudo-chairs S2 and S2'
cannot enjoy hyperconjugative
interactions as much as C2 and
C2'. The n(S1) ! s*(O1-C1) in-
teraction as well as the
n(O1) ! s*(S ! O) are playing
decisive roles.
Butadiene is much less reac-
tive than 2,3-dialkylbuta-1,3-di-
Figure 2. Different conformations of 2 as computed at the B3LYP/6-31G(d) level.
Table 1. Some representative bond lengths [ä] and angles [8] for
enes toward SO (Figure 3) and
2
up to now the parent sultine 3
had never been observed.
À1
À3
When a 2.5 mol dm solution of butadiene in SO /CD Cl /
2
2
2
1
,4,5,6,7,8-hexahydro-2,3-benzoxathiin-3-oxide (2).
CF COOH was left at À408C, equilibrium with 3 was
3
Parameter
B3LYP/6-31G(d)
Exptl
1.520(4)
1.655(4)
1.847(5)
1.461(6)
107.6(2)
105.9(2)
98.1(2)
observed after a week (K(butadiene‡SO > 3)  4.4 Â
2
À3
À1
À3
S1
ÀO2
1.492
1.687
1.844
1.439
110.1
106.6
94.0
10 mol dm at À408C (CH CN as internal reference).
3
À1
À1
S1ÀO1
S1ÀC4
O1ÀC1
Using an entropy of reaction of À42 calK mol for this
[7]
cycloaddition, one estimates K(butadiene‡SO > 3) ˆ
2
3
À1
0
.02 dm mol at À608C to be compared with K(isopre-
O2-S1-O1
3
À1
ne‡SO > 4-methylsultine) ˆ 0.03dm mol at the same
O2-S1-C4
O1-S1-C4
2
[
7]
1
temperature. The H NMR spectrum of 3 is consistent with a
pseudo-chair conformation as for 2 (Figure 4).
C1-O1-S1
O1-C1-C2
114.2
115.1
43.7
114.9(3)
115.5(4)
48.2(4)
O2-S1-O1-C1
C4-S1-O1-C1
S1-O1-C1-C2
O1-C1-C2-C3
O2-S1-C4-C3
O1-S1-C4-C347.4
Table 2. Thermodynamic data[a] (relative to reactants) as computed at
213.15 K for the different conformers of the 1,4,5,6,7,8-hexahydro-2,3-
À 65.7
À 61.4(4)
55.6
52.5(5)
À1
À1 À1
À 15.4
À 65.0
À 14.0(7)
À 68.8(4)
benzoxathiin-3-oxide. DE, DH and DG in kcalmol , DS in calmol K .
DG[b]
Structure
DE
DH
DS
42.1(4)
C2
C2'
B2
B2'
S2
À 8.5
À 7.5
À 6.5
À 6.3
À 5.0
À 5.6
À 9.4
À 8.8
À 7.3
À 7.1
À 5.8
À 6.5
À 45.2
À 44.6
À 43.5
À 43.5
À 44.9
À 45.2
À 2.1
À 1.7
À 0.4
À 0.2
1.4
indicating that the pseudo-chairs of the sultine and cyclo-
hexene moiety ™communicate∫ with each other.
S2'
0.8
Contrary to what has been found for 6-fluorosultines[
sofa conformers of the sultines with intra-ring oxygen atom
lying in the plane of four carbon atoms of the sultine are not
energy minima. Conformers S2 and S2' with pseudo-equato-
5, 6]
[a] Solvation energy as estimated by means of the Onsager model is
included. [b] DG includes the correction factor for changing the standard
state function from 1 atm to 272 atm [passing from gas phase to condensed
phase; see R. L. Martin, P. J. Hay, L. R. Pratt, J. Phys. Chem. A 1998, 102,
À1
rial SˆO bonds are calculated to be about 2 ± 3kcalmol less
3
565].
Chem. Eur. J. 2003, 9, 4911 ± 4915
www.chemeurj.org
¹ 2003Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4913

P. Vogel, J. A. Sordo et al.
FULL PAPER
Table 3. Different hyperconjugative contributions (DE/kcalmol )[a] calculated at the B3LYP/6-31G(d)
level of theory for the electron transfers from lone pair (n) to empty s* and p* orbitals in the conformers of
sultine.
À1
4H); 13C NMR (100.6 MHz, CD
2
2 2
Cl /SO ,
1
294 K): d ˆ 22.7 (t, J(C,H) ˆ 129 Hz), 26.4
1
1
(t, J(C,H) ˆ 127 Hz), 60.3(t,
J(C,H) ˆ
1
42 Hz), 128.9 (s, C(1), C(5)).
Structure n(O1) ! s*(S1,O2) n(O2) ! s*(S1,O1) n(O2) ! s*(S1,C4) n(S1) ! s*(O1,C1) DEtotal
Crystal
of
2
2 ¥ SO :
orthorhombic,
C2
C2'
B2
B2'
S2
7.17
7.29
10.6
10.7
2.84
2.69
43.0
43.1
42.2
42.322.1
42.2
21.8
22.1
22.1
4.58
4.70
4.95
80.0
1.37
76.5
77.3
79.9
a ˆ 8.294(2), b ˆ 8.4181(2), c ˆ 16.066(4) ä,
3
a ˆ 90, b ˆ 90, g ˆ 908, Vˆ 12121.7(5) ä ,
À3
1
ˆ 1.399 Mgm
,
data/restraints/parame-
4.92
22.1
1.3 68.2
terˆ 1945/0/127, ab 140(2) K.
CCDC-198362 (2 ¥ SO and -198363
1,3,4,5,6,7-hexahydrobenzo[c]thiophene
68.6
2
)
S2'
42.321.8
6
(
2
,2-dioxide) contain the supplementary
[
a] See Figure 2 for notation.
crystallographic data for this paper. These
data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crys-
tallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK; (fax:
(
‡44)1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk).
,6-Dihydro-1,2-oxathiin 2-oxide (3): A 1:1 mixture of butadiene and
CF COOH (80 mg) in CDCl (0.15 mL) containing 2% CH CN (internal
3
Figure 3.
3
3
3
reference) was placed in a 5 mm pyrex NMR tube and degassed (freeze/
thaw cycles) on the vacuum line. Sulfur dioxide (0.3mL) dried as above was
transferred to this mixture (liq. N ). The NMR tube was sealed off from the
2
vacuum line and immersed in a EtOH bath maintained at À408C for 7 d
1
until equilibrium was reached (control by H NMR). An equilibrium
À3
À3
3
constant K  4.4  10 mol dm was evaluated at À408C for butadie-
1
ne‡SO
2
>
sultine 3.
H
NMR (400 MHz, CD
2
Cl
2
/SO
2
/CF
3
COOH,
3
CH
3
CN, 233 K): d ˆ 5.88 (dm, J(H-4,H-5) ˆ 11.6 Hz, H-5), 5.66 (ddddd,
3
3
3
4
J(H-4,H-5) ˆ 11.6, J(H
e
-3,H-4) ˆ 6.4, J(H
a
2
-3,H-4) ˆ 2.2, J(H-4,H
e
4
-6) ˆ
Figure 4.
4
3
J(H
a
-6,H-4) ˆ 2.2 Hz, H-4), 4.53(ddddd, J ˆ 16.7, J(H-5,H
a
-6) ˆ J(H-
5
5
4
,H
a
-6) ˆ 2.2, J(Ha-3,H
a
-6) ˆ 4.6, J(H
e
-3,H
-6) ˆ 2.2, J(H
a
-6) ˆ 2.9 Hz, H
a
-6), 4.38 (dddd,
-6) ˆ 2.7 Hz, H
2
3
4
5
J ˆ 16.7, J(H-5,H
e
-6) ˆ 2.7, J(H-4,H
e
a
-3,H
e
e
-
2
2
3
6
), 3.43 (dm, J ˆ 17.1 Hz, H
a
-3), 3.07 (ddd, J ˆ 17.1, J(H
e
-3,H-4) ˆ 6.4,
Conclusion
5
13
J(H
e
-3,H
a
-6) ˆ 2.9 Hz,
H
e
-3);
C
NMR (100.6 MHz, CD
2
Cl
2
/SO
2
/
1
CF
3
COOH, CH
3
CN, 233 K): d ˆ 124.3((d, J(C,H) ˆ 163Hz, C-5), 113.8
1
1
Butadiene and alkylsubstituted derivatives undergo hetero-
Diels ± Alder additions with SO2 activated with protic or
Lewis acid below À408C, a reaction that is faster than the
(d, J(C,H) ˆ 170 Hz, C-4) 59.1 (t, J(C,H) ˆ 153Hz, C-6), 45.3 (t,
1
J(C,H) ˆ 141 Hz, C-3).
[19]
well-known chelotropic addition of SO . X-ray diffraction
2
Acknowledgement
data confirm predictions of quantum chemical calculations
that the non-fluorinated sultine prefer pseudo-chair confor-
mations with pseudo-axial SˆO bonds. The sulfinate moiety of
This work was supported by the Swiss National Science Foundation, the
Centro Svizzero di Calcolo Scientifico (Manno), the SOCRATES (Oviedo/
Lausanne) program, the Office F e¬ d e¬ ral de l×Enseignement et de la Science
(Bern, European COST D13/010/01 action), and by DGI (BQU 2001-3600-
CO2-01, Madrid, Spain).
the non-fluorinated sultine manifests a conformational
anomeric effect that our computational approach shows is
due to hyperconjugative interactions.
[
[
1] B. Deguin, P. Vogel, J. Am. Chem. Soc. 1992, 114, 9210.
2] a) D. Su a¬ rez, T. L. Sordo, J. A. Sordo, J. Am. Chem. Soc. 1994, 116,
Experimental Section
7
63; b) D. Su a¬ rez, T. L. Sordo, J. A. Sordo, J. Org. Chem. 1995, 60,
For general methods, see ref. [6].
2
848.
1
,4,5,6,7,8-Hexahydro-2,3-benzoxathiin-3-oxide (2): On the vacuum line,
dry SO (1.4 mL) was transferred to a frozen (liq. N ) solution of 1,2-
dimethylidenecyclohexane (1) (436 mg, 4.03 mmol) in anhydrous meth-
anol (5 mL). Dry SO was obtained by degassing SO and filtering (gas)
[
[
3] a) T. Fern a¬ ndez, J. A. Sordo, F. Monnat, B. Deguin, P. Vogel, J. Am.
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Acta 2002, 85, 733; E. Roversi, P. Vogel, Helv. Chim. Acta 2002, 85,
2
2
[16]
2
2
through a column of alkaline aluminium oxide 90 (act. I, Merck). It was
then mixed with quinoline and iodine and distilled from that mixture on the
7
61; E. Roversi, F. Monnat, K. Schenk, P. Vogel, P. Bra nƒ a, J. A. Sordo,
vacuum line. The mixture of 1‡SO
slowly to À788C and was kept at this temperature for 5 d. The crystals of 2 ¥
SO
2
and MeOH was allowed to warm
Chem. Eur. J. 2000, 6, 1858.
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9] F. Monnat, P. Vogel, V. M. Ray o¬ n, J. A. Sordo, J. Org. Chem. 2000, 67,
2
1
were collected at this temperature and measured at À1008C. Data for
2
: H NMR (400 MHz, CD
2
Cl
2
/SO
2
/CFCl
3
, 193K): d ˆ 1.56 (m, 2H), 1.79
2
(
4
SO
1
m, 2H), 1.86 (m, 2H), 1.91 (m, 2H), 2.75/3.39 (2d, J ˆ 17.3, 2H, H
2
C(5)),
2
Cl /
2
13
.14/4.25 (2d, J ˆ 15.9 Hz, 2H, H
2
1
C(2)); C NMR (100.6 MHz, CD
J(C,H) ˆ 129 Hz), 22.1 (t, J(C,H) ˆ
2
1
2
/CFCl
3
, 193K): d ˆ 21.3(t,
31 Hz), 24.7 (t, 1J(C,H) ˆ 126 Hz), 29.0 (t, J(C,H) ˆ 128 Hz), 49.3(t,
1
[
[
1
1
J(C,H) ˆ 138 Hz, C(5)), 60.0 (t, J(C,H) ˆ 150 Hz, C(2)), 117.8 (s, C(6)),
1
25.9 (s, C(1)).
1
882.
The same mixture allowed to stand at À408C for 5 d gave crystalline
[10] Gaussian 98, Revision A.6, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A.
Montgomery, Jr., R. E. Stratmann, J. C. Burant, S. Dapprich, J. M.
1
1
,3,4,5,6,7-hexahydrobenzo[c]thiophene 2,2-dioxide, white solid. H NMR
(
400 MHz, CD
2
Cl
2
/SO
2
, 294 K): d ˆ 1.78 (m, 4H), 2.10 (m, 4H), 3.68 (m,
4914
¹ 2003Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 4911 ± 4915

Hetero-Diels ± Alder Addition
4911±4915
Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J. Tomasi,
V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo,
S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K.
Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B.
Foresman, J. Cioslowski, J. V. Ortiz, B. B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L. Martin,
D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, C.
Gonzalez, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W.
Wong, J. L. Andres, C. Gonzalez, M. Head-Gordon, E. S. Replogle,
and J. A. Pople, Gaussian, Inc., Pittsburgh PA, 1998.
[15] A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988, 88, 899.
[16] N. A. Le, M. Jones, Jr., F. Bickelhaupt, W. H. de Wolf, J. Am. Chem.
Soc. 1989, 111, 8491.
[17] The corresponding crystalline sulfolene (1,3,4,5,6,7-hexahydroben-
zo[c]-thiophen 2,2-oxide) was obtained when the reaction was carried
out at À508C. X-ray data of this compound are given in the
Supporting Information.
[18] A. Bondi, J. Phys. Chem. 1964, 68, 441.
[19] Durst and co-workers had shown that sultines undergo elimination of
2
SO faster than corresponding sulfolenes: F. Jung, M. Molin, R.
[
11] D. A. McQuarrie, Statistical Thermodynamics, University Science
Books, Mill Valley, CA, 1997.
Van der Elzen, T. Durst, J. Am. Chem. Soc. 1974, 96, 935; they also
showed that o-quinodimethanes undergo hetero-Diels ± Alder reac-
[
[
[
12] M. W. Wong, M. J. Frisch, K. B. Wiberg, J. Am. Chem. Soc. 1991, 113,
tions with SO
Durst, L. Tetreault-Ryan, Tetrahedron Lett. 1978, 2353.
2
faster than corresponding chelotropic additions: T.
4
776.
13] M. W. Wong, K. B. Wiberg, M. J. Frisch, J. Am. Chem. Soc. 1992, 114,
23.
14] R. L. Martin, P. J. Hay, L. R. Pratt, J. Phys. Chem. A 1998, 102, 3565.
5
Received: March 10, 2003[F49 23 ]
Chem. Eur. J. 2003, 9, 4911 ± 4915
www.chemeurj.org
¹ 2003Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4915