organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
disubstituted product, but an oily compound in which one of
either the 2- or 3-methyl groups had been replaced by an
±SCH3 substituent (see scheme). Since an ipso-substitution of
ISSN 0108-2701
2,5-Bis(methylthio)-1,4-benzoquinone
and 2-methyl-3-(methylsulfonyl)-
benzo[b]thiophene
Masood Parvez,* Shaun T. Mesher and Peter D. Clark
Department of Chemistry, The University of Calgary, 2500 University Drive NW,
Calgary, Alberta, Canada T2N 1N4
Received 11 October 1999
Accepted 25 January 2000
The structure of 2,5-bis(methylthio)-1,4-benzoquinone, C8H8-
O2S2, is composed of an essentially planar centrosymmetric
benzoquinone substituted with two methylthio groups. The
important bond distances are SÐCsp3 1.788 (2) and SÐCsp2
2
2
this type is quite rare and because other spectroscopic
methods could not differentiate whether substitution had
occurred at the 2- or 3- positions, the product was oxidized to
its crystalline sulfonyl derivative using a literature procedure
(Aitken et al., 1994) and was subjected to X-ray crystal-
lographic analysis. This analysis showed that the 3-thiomethyl
derivative, (IV), had been produced, suggesting that a sulfur-
assisted ipso-substitution had taken place.
Ê
1.724 (2) A, and the two Csp ÐCsp distances are 1.447 (3)
Ê
and 1.504 (3) A, which differ signi®cantly. There are short
2
Ê
SÁ Á ÁS interactions of 3.430 (1) A and Csp ÐHÁ Á ÁO-type
contacts forming a dimeric motif with graph set R22(8). The
structure of 2-methyl-3-(methylsulfonyl)benzo[b]thiophene,
C10H10O2S2, is composed of an essentially planar benzothio-
phene moiety substituted with methyl and methylsulfonyl
groups. The mean values of the important bond distances are
endocyclic SÐCsp2 1.734 (3), S O 1.434 (4) and CÐCaromatic
The structure of (I) is composed of centrosymmetric mol-
ecules which are essentially planar [maximum deviation
Ê
0.026 (2) A for C3]. The bond distances agree well with the
2
3
Ê
1.389 (10) A. The exocyclic SÐCsp and SÐCsp distances are
Ê
1.759 (4) and 1.763 (5) A, respectively.
corresponding values reported for bis-, tris- and tetrakis-
(thiophenyl)benzoquinones (Cambridge Structural Database;
Allen & Kennard, 1993). The SÐCsp3 and SÐCsp2 bond
Comment
Recently, 2,5-bis(methylthio)-1,4-benzoquinone, (I), has been
used to prepare sulfur-quinone polyurethane coatings which
are applied to protect iron surfaces. Surprisingly, the synthesis
of (I) was not reported until 1998 and then was obtained in
only 15% yield by reaction of 1,4-benzoquinone with sodium
thiomethoxide (Hu & Nikles, 1998). Using a clay-catalyzed
one-step thioalkylation procedure developed in our labora-
tories (Clark et al., 1996), we have been able to make
compound (I) in good yield and on a large scale. Conveniently,
one half of the quinone reagent re-oxidizes the intermediate
Ê
distances of 1.788 (2) and 1.724 (2) A, respectively, differ
Ê
signi®cantly. The bonds C3 O1 [1.227 (3) A] and C1 C2
2
[1.353 (3) A] are double bonds. The Csp ÐCsp bonds, C1Ð
2
Ê
i
C3 [1.504 (3) A; symmetry code: (i) x, y, 1 z] and C2Ð
Ê
Ê
C3 [1.447 (3) A], are in excellent agreement with the values
1
product to yield the product, (I) (see scheme). H NMR
analysis of (I), which is obtained from ethanol as brilliant red
crystals, does not allow differentiation of (I) from its 2,3-
bis(methylthio) isomer. X-ray analysis showed, however, that
the clay-catalyzed synthesis reported herein yielded the 2,5-
isomer as the sole product.
A one-step thioalkylation procedure developed in our
laboratory allows addition of ±SR groups to aromatics and
heteroaromatics (Clark et al., 1996). However, it was clear that
reaction of 2,3-methylbenzo[b]thiophene, (III), with dimethyl
disul®de over a clay catalyst did not yield the expected 5,6-
Figure 1
ORTEPII (Johnson, 1976) drawing of (I) with the atomic numbering
scheme. Displacement ellipsoids have been plotted at the 50%
probability level and H atoms assigned arbitrary radii [symmetry code:
(i) x, y, 1 z].
ꢀ
574 # 2000 International Union of Crystallography
Printed in Great Britain ± all rights reserved
Acta Cryst. (2000). C56, 574±576
Parvez, Masood
