Mendeleev Commun., 2007, 17, 301–302
diones 2 easily react with alkyl halides in DMF with the use of
(3.520 Å) corresponds to a normal van der Waals contact. This
points to the fact that in a crystal state the structure of 3b
possesses all features of photochromic compounds.
K2CO3 as a base. The reaction of 2b leads to alkyl-substituted
cyclopentenediones 3a,b in high yields (91–94%).†
The molecular and crystal structures of 3b were proved by
X-ray data (Figure 1).‡ The molecule has an anti-parallel con-
formation. Dihedral angles between thienyl rings and the plane
cyclopentene fragment [C(2)C(3)C(4)C(5)] are 49.92° and 42.98°.
This is close to classical angles for photochromic dihetaryl-
ethenes (47° for a disubstituted maleic anhydride2). The C(3)–C(4)
bond length (1.350 Å) a little exceeds the standard double bond
length C=C (1.33 Å).5 The intramolecular distance C(2')···C(2'')
Thus, we have developed a convenient general approach to
the synthesis of new dihetarylethenes with the cyclopentene-
dione bridge fragment. Synthesised compounds 2 and 3 possess
photochromic properties (lA = 370–400 nm, lB = 500–540 nm).
This study was supported by the Russian Foundation for
Basic Research (grant no. 07-03-00381-a).
References
†
The 1H NMR spectra were recorded on Bruker AM-300 (300 MHz)
1 M. Irie, Chem. Rev., 2000, 100, 1685.
2 H. Miyasaka, T. Nobuto, M. Murakami, A. Itaya, N. Tamai and M. Irie,
J. Phys. Chem. A, 2002, 106, 8096.
3 K. Uchida, Y. Kido, T. Yamaguchi and M. Irie, Bull. Chem. Soc. Jpn.,
1998, 71, 1101.
4 M. M. Krayushkin, D. V. Pashchenko, B. V. Lichitskii, T. M. Valova,
Yu. P. Strokach and V. A. Barachevskii, Zh. Org. Khim., 2006, 42, 1827
(Russ. J. Org. Chem., 2006, 42, 1816).
5 H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and
R. Taylor, J. Chem. Soc., Perkin Trans. 2, 1987, S1.
6 Siemens. P3 and XDISK. Release 4.1, Siemens AXS, Madison, Wisconsin,
USA, 1989.
and Bruker WM-250 (250 MHz) instruments in [2H6]DMSO. Melting
points were measured on a Boetius hot stage and not corrected. The reaction
mixtures were analysed and the purity of the products was checked by
TLC on Merck Silica gel 60 F254 plates using AcOEt–hexane (1:3) for
elution.
4,5-Bis(2,5-dimethyl-3-thienyl)-2-phenylcyclopent-4-ene-1,3-dione 2a.
Sodium (12 mg, 0.5 mmol) was dissolved in 2 ml of abs. MeOH, and
corresponding arylidene 1a (196 mg, 0.5 mmol) was added to the solu-
tion. The reaction mixture was refluxed for 3 h; then, water (5 ml) and acetic
acid (40 µl) were added. The precipitate was filtered off, rinsed with water
and recrystallised from ethanol. Yield, 170 mg (86%); mp 112–114 °C.
1H NMR ([2H6]DMSO) d: 1.87 (s, 6H, Me), 2.33 (s, 6H, Me), 4.58
(s, 1H, CH), 6.60 (s, 2H, HHet), 7.10–7.40 (m, 5H, HAr). Found (%):
C, 70.54; H, 5.31; S, 16.23. Calc. for C23H20O2S2 (392.54) (%): C, 70.38;
H, 5.14; S, 16.34.
7 G. M. Sheldrik, SHELXTL v. 5.10, Structure Determination Software
Suite, Bruker AXS, Madison, Wisconsin, USA, 1998.
4,5-Bis(2,5-dimethyl-3-thienyl)-2-(4-methoxyphenyl)cyclopent-4-ene-
1,3-dione 2b. Yield, 201 mg (95%); mp 168–170 °C. 1H NMR ([2H6]DMSO)
d: 1.90 (s, 6H, Me), 2.35 (s, 6H, Me), 3.75 (s, 3H, OMe), 4.50 (s, 1H,
CH), 6.65 (s, 2H, HHet), 6.95 (d, 2H, HAr, J 7 Hz), 7.10 (d, 2H, HAr, J 7 Hz).
Found (%): C, 68.38; H, 5.31; S, 15.62. Calc. for C24H22O3S2 (422.57)
(%): C, 68.22; H, 5.25; S, 15.78.
General procedure for the alkylation of diketones 2. Diketone 2b
(0.125 mmol, 50 mg) was dissolved in 2 ml of DMF; potassium carbonate
(0.720 mmol, 100 mg) and a corresponding alkylating agent (0.150 mmol)
were added. The reaction mixture was stirred for 2 h at room tempe-
rature (TLC control; eluent, ethyl acetate–hexane, 1:3) and then poured
into water. The precipitated solid was filtered off, rinsed with water and
recrystallised from ethanol.
4,5-Bis(2,5-dimethyl-3-thienyl)-2-(4-methoxyphenyl)-2-methylcyclopent-
4-ene-1,3-dione 3a. Yield, 58 mg (94%); mp 106–108 °C. 1H NMR
([2H6]DMSO) d: 1.60 (s, 3H, MeR1), 1.87 (s, 6H, MeHet), 2.37 (s, 6H,
MeHet), 3.75 (s, 3H, OMe), 6.65 (s, 2H, HHet), 6.95 (d, 2H, HAr, J 7 Hz),
7.20 (d, 2H, HAr, J 7 Hz). Found (%): C, 68.89; H, 5.71; S, 14.53. Calc.
for C25H24O3S2 (436.60) (%): C, 68.78; H, 5.54; S, 14.69.
[3,4-Bis(2,5-dimethyl-3-thienyl)-1-(4-methoxyphenyl)-2,5-dioxocyclo-
pent-3-enyl]acetic acid ethyl ester 3b. Yield 58 mg (91%); mp 139–141 °C.
1H NMR ([2H6]DMSO) d: 1.10 (t, 3H, MeCH2O, J 8 Hz), 1.83 (s, 6H,
Me), 2.35 (s, 6H, Me), 3.35 (s, 2H, CH2CO2Et), 3.70 (s, 3H, OMe), 4.00
(q, 2H, CH2Me, J 8 Hz), 6.60 (s, 2H, HHet), 6.95 (d, 2H, HAr, J 7 Hz),
7.23 (d, 2H, HAr, J 7 Hz). Found (%): C, 66.35; H, 5.61; S, 12.79. Calc.
for C28H28O5S2 (508.66) (%): C, 66.12; H, 5.55; S, 12.61.
Received: 5th December 2006; Com. 06/2837
‡
Crystallographic data for 3b: at 290 K crystals of C28H28O5S2 are
monoclinic, space group Cc, a = 12.402(4), b = 19.926(5), c = 11.372(4) Å,
b = 110.61(2)°, V = 2630.3(14) Å3, Z = 4, dcalc = 1.284 g cm–3, M = 508.62.
The unit cell parameters and the intensities of 2665 independent reflec-
tions were measured on a Syntex P21 diffractometer (MoKα, graphite
monochromator, q/2q-scan mode in the 2.03 £ q £ 26.06° range). The
structure was solved by the direct method, which revealed all non-
hydrogen atoms, and refined by the full-matrix least-squares method in
the anisotropic approximation for non-hydrogen atoms. The hydrogen
atoms were revealed by difference electron density synthesis and refined
isotropically by the least-squares calculations. The final R-factors for
2070 deflections with I > 2s(I): R1 = 0.046, wR2 = 0.111. For all the
independent deflections R1 = 0.081, wR2 = 0.125. The Siemens P3/PC6
and SHELXTL PLUS 57 programs were used for calculations.
CCDC 658786 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
For details, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 2007.
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