F
R. Panwar et al.
Letter
Synlett
dine-6-carbonitriles in moderate to good yields. Interest-
ingly, we have also demonstrated that 2-(imidazolidin-2-
ylidene)-1-arylethanones can act as nucleophiles as well as
electrophiles, depending on the counter-precursor used,
and [3+3] annulation can be replaced by [4+2] annulation.
We have also investigated the mechanistic pathway and
have found experimental evidence, in the form of isolated
intermediates, to support the proposed path of the reac-
tion.
(10) (a) Jones, R. C. F.; Patel, P.; Hirst, S. C. Tetrahedron Lett. 1989, 30,
5361. (b) Zhang, J.-H.; Wang, M.-X.; Huang, Z.-T. Tetrahedron
Lett. 1998, 39, 9237. (c) Zhang, J.-H.; Wang, M.-X.; Huang, Z.-T.
J. Chem. Soc., Perkin Trans. 1 1999, 2087.
(11) (a) Huang, Z.-T.; Liu, Z.-R. Chem. Ber. 1989, 122, 95. (b) Wang, L.-
B.; Yu, C.-Y.; Huang, Z.-T. Synthesis 1994, 1441.
(12) Zhang, J.-H.; Wang, M.-X.; Huang, Z.-T. J. Chem. Soc. Perkin Trans.
1 1999, 321.
(13) Jones, R. C. F.; Patel, P.; Hirst, S. C.; Turner, I. Tetrahedron 1997,
53, 11781.
(14) Pratap, R.; Sharon, A.; Maulik, P. R.; Ram, V. J. Tetrahedron Lett.
2005, 46, 85.
(15) Sharon, A.; Pratap, R.; Maulik, P. R.; Ram, V. J. Tetrahedron 2005,
61, 3781.
Acknowledgment
(16) Liao, J.-P.; Zhang, T.; Yu, C.-Y.; Huang, Z.-T. Synlett 2007, 761.
(17) (a) Singh, S.; Yadav, P.; Sahu, S. N.; Althagafi, I.; Kumar, A.;
Kumar, B.; Ram, V. J.; Pratap, R. Org. Biomol. Chem. 2014, 12,
4730. (b) Singh, S.; Althagafi, I.; Yadav, P.; Panwar, R.; Kumar, A.;
Pratap, R. Tetrahedron 2014, 70, 8879.
R.P. thanks the Department of Science and Technology (DST, New
Delhi) [DST-DU purse grant] and the University of Delhi, Delhi [R & D
Grant] for financial support. S.S. and R.S. thank the Council of Scien-
tific and Industrial Research (CSIR, New Delhi), and R.P., P.Y., and S.
thank the University Grants Commission (UGC, New Delhi) for Re-
search Fellowships. A.K. is grateful to DST, New Delhi for funding
within the project SB/FT/CS-018/2012. R.P. also thanks the University
of Delhi for study leave, and JSPS for providing an invitation fellow-
ship. The authors thank the University of Delhi for providing research
funding and instrumentation facilities.
(18) 7-Aryl-6-(2-cyanophenyl)-5-oxo-2,3,5,6-tetrahydroimid-
azo[1,2-a]pyridine-6-carbonitriles 5a–i; General Procedure
A
mixture of the appropriate 1-aryl-2-(imidazolidin-2-
ylidene)ethanone 3 (0.5 mmol), 2-[1-cyano-2,2-bis(methylsul-
fanyl)vinyl]benzonitrile (4; 0.6 mmol), H2O (0.6 mmol), and
NaH (1.0 mmol) in DMSO (3.0 mL) was stirred at r.t. for 8 h.
When the reaction was complete, the crude mixture was
poured slowly onto ice–water with constant stirring. The
mixture was then neutralized with 10% aq HCl. The resulting
precipitate was collected by filtration, washed with H2O, and
dried. Products were purified by column chromatography
(silica gel, EtOAc).
Supporting Information
Supporting information for this article is available online at
S
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ortioInfgrmoaitn
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6-(2-Cyanophenyl)-5-oxo-7-phenyl-2,3,5,6-tetrahydroimid-
azo[1,2-a]pyridine-6-carbonitrile (5a)
References
Brown solid; yield: 112 mg (66%); mp 130–132 °C. IR (KBr):
(1) (a) Pan, L.; Bi, X.; Liu, Q. Chem. Soc. Rev. 2013, 42, 1251. (b) Pan,
L.; Liu, Q. Synlett 2011, 1073.
2924, 2225, 1606 cm–1 1H NMR (400 MHz, CDCI3): δ = 4.05–
.
3.90 (m, 2 H, CH2), 4.10–4.27 (m, 2 H, CH2), 6.83 (s, 1 H, ArH),
7.13–7.22 (m, 5 H, ArH), 7.33 (t, J = 7.6 Hz, 1 H, ArH), 7.50–7.55
(m, 2 H, ArH), 7.81 (d, J = 7.6 Hz, 1 H, ArH). 13C NMR (100 MHz,
CDCl3): δ = 43.5, 54.2, 54.8, 110.1, 115.3, 115.6, 120.1, 127.8,
128.5, 129.4, 129.7, 130.8, 133.3, 134.8, 134.9, 136.5, 144.2,
152.4, 158.7. HRMS (ESI): m/z [M + H]+ calcd for C21H15N4O:
339.1240; found: 339.1238.
(2) (a) Dieter, R. K. Tetrahedron 1986, 42, 3029. (b) Junjappa, H.; Ila,
H.; Asokan, C. V. Tetrahedron 1990, 46, 5423; and reference
cited therein. (c) Kolb, M. Synthesis 1990, 171. (d) Ila, H.;
Junjappa, H.; Barun, O. J. Organomet. Chem. 2001, 624, 34.
(3) (a) Tominaga, Y.; Ushirogochi, A.; Matsuda, Y. J. Heterocycl.
Chem. 1987, 24, 1557. (b) Sommen, G. L.; Comel, A.; Kirsch, G.
Synth. Commun. 2005, 35, 693.
(4) For reviews, see: (a) Huang, Z.-T.; Wang, M.-X. Heterocycles
1994, 37, 1233. (b) Huang, Z.-T.; Wang, M.-X. Prog. Nat. Sci.
2002, 12, 249. (c) Yu, C.-Y.; Yang, P.-H.; Zhao, M.-X.; Huang, Z.-T.
Synlett 2006, 1835.
(5) Huang, Z.-T.; Wang, M.-X. J. Org. Chem. 1992, 57, 184; and refer-
ences cited therein.
(6) (a) Huang, Z.-T.; Wang, M.-X. Synth. Commun. 1991, 21, 1167.
(b) Huang, Z.-T.; Wang, M.-X. Synth. Commun. 1991, 21, 1909.
(7) Liu, B.; Wang, M.-X.; Huang, Z.-T. Tetrahedron Lett. 1999, 40,
7399.
(19) CCDC 1501042 and 1501043 contain the supplementary crys-
tallographic data for compounds 5b and 8b, respectively. The
data can be obtained free of charge from The Cambridge Crys-
tures.
5b: C21H13FN4O, M = 356.35, triclinic, P-1, a = 8.1557(9) Å, b =
8.6242(8) Å, c = 13.0701(13) Å, α = 109.147(9)°, β= 95.496(8)°,
γ = 100.594(8)°, V = 841.50(16) Å3, Z = 2, Dcalc = 1.406 mg/m3,
F(000) = 368, crystal size 0.p220 × 0.200 × 0.180 mm, reflec-
tions collected 6662, independent reflections 3844 [R(int)
=
0.0198], Final indices [I> 2σ(I)] R1 = 0.0519, wR2 = 0.0997, R
indices (all data) R1 = 0.0854, wR2 = 0.1188, GoF 1.038, Largest
difference peak and hole 0.168 and –0.220 e Å–3.
(8) Wang, M.-X.; Liang, J.-M.; Huang, Z.-T. J. Chem. Res., Synop. 1994,
166; J. Chem. Res., Miniprint 1994, 1001.
(9) (a) Huang, Z.-T.; Tzai, L.-H. Chem. Ber. 1986, 119, 2208.
(b) Huang, Z.-T.; Liu, Z.-R. Heterocycles 1986, 24, 2247.
(c) Huang, Z.-T.; Wang, M.-X. J. Chem. Soc., Perkin Trans. 1 1993,
1085; and references cited therein. (d) Jones, R. C. F.; Patel, P.;
Hirst, S. C.; Smallridge, M. J. Tetrahedron 1998, 54, 6191; and
references cited therein.
8b: C21H17N3O2, M = 343.38, monoclinic, P21/c, a = 9.9517(10) Å,
b = 23.171(2) Å, c = 7.5232(7) Å, β = 105.529(10)°, V = 1671.4(3)
Å3, Z = 4, Dcalc = 1.365 mg/m3, F(000) = 720, crystal size 0.210 ×
0.200 × 0.170 mm, reflections collected 13503, independent
reflections 3912 [R(int) = 0.0663], Final indices [I> 2σ(I)] R1 =
0.0668, wR2 = 0.1530, R indices (all data) R1 = 0.0924, wR2 =
0.1741, GoF 1.078, Largest difference peak and hole 0.368 and
–0.248 e Å–3.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F