2316
A. A. Grigor’ev et al.
Letter
Synlett
to delocalization of the negative charge around the dicy-
anomethylene fragment. Electron-donating R substituents
destabilize the carbanion D which leads to a decrease in
yield of 3 or completely inhibits the pathway. Nucleophilic
substitution on the sulfur atom in intermediate B is very
unlikely, because the dianion C formed in this case is not
resonance-stabilized. The presence of base prevents the
protonation of intermediate B, and the reduction does not
occur. This leads to the formation of [2-(5-amino-4-cyano-
2-(2-hydroxyethylthio)-2-arylfuran-3(2H)-ylidene]malo-
nonitriles 4 when using triethylamine as base (Table 3).
(5) Maruoka, H.; Tomioka, Y.; Yamazaki, M. J. Heterocycl. Chem.
2002, 39, 743.
(6) Wamhoff, H.; Thiemig, H. A. Chem. Ber. 1986, 119, 1070.
(7) Testa, M. G.; Perrini, G.; Chiacchio, U.; Corsaro, A. Phosphorus,
Sulfur Silicon Relat. Elem. 1994, 86, 75.
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1993, 302.
(9) Wamhoff, H.; Thiemig, H. A.; Puff, H.; Friedrichs, E. Chem. Ber.
1985, 118, 4782.
(10) Moiseeva, I. G.; Nasakin, O. E.; Lukin, P. M.; Romanov, V. N.;
Tafeenko, V. A. Chem. Heterocycl. Compd. 1990, 277, 828.
(11) Yamagata, K.; Akizuki, K.; Yamazaki, M. J. Prakt. Chem. 1998,
340, 627.
(12) Ji, Y.; Qian, Y.; Lu, W. J. Mater. Chem. 2012, 22, 12375.
(13) He, M.; Leslie, T. M.; Sinicropi, J. A. Chem. Mater. 2002, 14, 4662.
(14) Liu, S.; Haller, H. Ma.; Dalton, L. R.; Jang, S.-H.; Jen, A. K.-Y. Adv.
Mater. 2003, 15, 603.
Table 3 Substituents and Yields of Dihydrofurans 4b–f via the Reac-
tion of Propenides 1 with Mercaptoethanol in the Presence of Triethyl-
amine
(15) Vannini, L.; Ndagijimana, M.; Saracino, P.; Vernocchi, P.;
Corsetti, A.; Vallicelli, M.; Cappa, F.; Cocconcelli, P. S.; Guerzoni,
M. E. Int. J. Food Microbiol. 2007, 120, 25.
(16) Lönn-Stensrud, J.; Petersen, F. C.; Benneche, T.; Scheie, A. A. Oral
Microbiol. Immunol. 2007, 22, 340.
(17) Witsø, I. L.; Benneche, T.; Vestby, L. K.; Nesse, L. L.; Lönn-Sten-
srud, J.; Scheie, A. A. Pathog. Dis. 2014, 70, 297.
(18) Castillo, S.; Heredia, N.; García, S. Folia Microbiol. (Praha, Czech.
Repub.) 2015, 60, 89.
Entry
Compd 4
R
Yield (%)
1
2
3
4
5
4b
4c
4d
4e
4f
Ph
86
82
73
71
81
4-MeC6H4
2,5-(MeO)2C6H3
1-naphthyl
4-PhC6H4
(19) Kayukov, Y. S.; Karpov, S. V.; Bardasov, I. N.; Kayukovа, O. V.;
Ershov, O. V.; Nasakin, O. E. Russ. J. Org. Chem. 2012, 48, 1107.
(20) Figure 2 shows the atom numbering in 3a. Displacement ellip-
soids are drawn at the 50% probability levels. Cell parameters
(3a): a = 13.9259(5), b = 8.8709(4), c = 10.5576(6) Å, β = 90°, β =
In conclusion, sodium borohydride is a universal re-
agent for reducing heterocyclization of propenides 1 to di-
hydrofurans 3.21 Mercaptoethanol is a more convenient re-
agent in order to synthesize dihydrofurans 322 with non-
electron-rich aryl substituents at position 2. Reacting
propenides 1 with mercaptoethanol in the presence of tri-
ethylamine results in reaction stopping at the stage of
sulfinyl-substituted furans 4.
98.44(0)°, γ = 90°; V = 1290.12(10) Å3, Z = 4, Dcalc = 1.278 g cm–3
The crystal is monoclinic and the space group is P1 21/c1.
.
CCDC 912663 for 3a contains the supplementary crystallo-
graphic data for this Letter. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
(21) Typical Procedure for the Preparation of 2-[5-Amino-2-aryl-
4-cyanofuran-3(2H)-ylidene]malononitriles 3a–j via the
Reaction of Propenides 1 with Sodium Borohydride
Acknowledgment
NaBH4 (0.56 g, 15 mmol) was added to a solution of potassium
2-acyl-1,1,3,3-tetracyanopropenide 1 (10 mmol) in H2O (20
mL), and the mixture was stirred at r.t. until the reaction
became colorless. The resulting solution was filtered and then
neutralized by addition of aq 5% H2SO4. The white precipitate
was filtered, recrystallized from AcOH, and dried in vacuo.
Compound 3a: yield 82% (2.03 g; via reaction with mercap-
toethanol) or 86% (2.13 g; via reaction with NaBH4), white solid,
mp 262–263 °С (dec.). 1H NMR (500.13 MHz, DMSO-d6): δ =
6.81 (1 H, s, CH), 7.41–7.52 (5 H, m, Ph), 10.07 (2 H, s, NH2). IR
(mineral oil): 3318, 3115 (NH2), 2223, 2212 (CN), 1663 (C=C)
cm–1. MS (EI, 70 eV): m/z (%) = 248 [M]+ (53), 221 [M – HCN]+
(7), 205 [M – HNCO]+ (33), 178 [M – HNCO – HCN]+ (100).
2-[5-Amino-4-cyano-2-methylfuran-3(2H)-ylidene]malono-
nitrile (3k)
This work was supported by a Scholarship from the President of the
Russian Federation for Young Scientists and Graduate Students СП-
3725.2015.4. The X-ray study was supported in part by M. V. Lo-
monosov Moscow State University Program of Development.
Supporting Information
Supporting information for this article is available online at
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References and Notes
NaBH4 (0.56 g, 15 mmol) was added to a solution of potassium
2-acetyl-1,1,3,3-tetracyanopropenide 1 (10 mmol) in H2O (20
mL), and the mixture was stirred at r.t. until the reaction
became colorless. The resulting solution was filtered, then neu-
tralized by addition of aq 5% H2SO4 and subsequently extracted
with EtOAc (3 × 10 mL). The combined organic layers were dried
(CaCl2), filtered, and concentrated in vacuo. The resulting
residue was purified by flash chromatography (SiO2, EtOAc),
(1) Karpov, S. V.; Kayukov, Y. S.; Bardasov, I. N.; Kayukovа, O. V.;
Ershov, O. V.; Nasakin, O. E. Russ. J. Org. Chem. 2011, 47, 405.
(2) Bardasov, I. N.; Kayukovа, O. V.; Kayukov, Y. S.; Ershov, O. V.;
Nasakin, O. E.; Tafeenko, V. A. Russ. J. Org. Chem. 2009, 45, 1325.
(3) Karpov, S. V.; Kayukov, Y. S.; Bardasov, I. N.; Ershov, O. V.;
Nasakin, O. E.; Tafeenko, V. A. Russ. J. Org. Chem. 2011, 47, 1161.
(4) Karpov, S. V.; Kayukov, Y. S.; Bardasov, I. N.; Kayukovа, O. V.;
Lipin, K. V.; Nasakin, O. E. Russ. J. Org. Chem. 2011, 47, 1492.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 2313–2317