J. S. Yadav et al. / Tetrahedron Letters 50 (2009) 2470–2473
2473
13. Yadav, J. S.; Reddy, B. V. S.; Basak, A. K.; Visali, B.; Narsaiah, A. V.; Nagaiah, K.
Eur. J. Org. Chem. 2004, 546–551.
1.2 equiv of aldehyde followed by 20 mol % of NbCl5. The reaction mixture
was stirred at rt against the time mentioned in the table. The reaction was
quenched by the addition of saturated aq NaHCO3 solution and the product
was extracted with ethylacetate. The product was purified by column
chromatography using EtOAc/Hexane as an eluent. As per the comment
raised by the referee, a reaction was attempted on 10 mmol scale. Compound
5a was prepared on 10 mmol scale in 1.5 h with 83% yield using 20 mol %
catalyst.
14. Suzuki, K.; Hashimoto, T.; Maeta, H.; Matsumoto, T. Synlett 1992, 125–128.
15. Howarth, J.; Gillespie, K. Tetrahedron Lett. 1996, 37, 6011–6012.
16. (a) Andrade, C. K. Z.; Azevedo, N. R. Tetrahedron Lett. 2001, 42, 6473–6476; (b)
Andrade, C. K. Z.; Azevedo, N. R.; Oliveira, G. R. Synthesis 2002, 928–936; (c)
Andrade, C. K. Z.; Oliveira, G. R. Tetrahedron Lett. 2002, 43, 1935–1937.
17. (a) Howarth, J.; Gillespie, K. Tetrahedron Lett. 1996, 37, 6011–6012. For other
NbCl5 catalyzed reactions, see:; (b) Hernandez, H.; Bernes, S.; Quintero, L.;
Sansinenea, E.; Ortiz, A. Tetrahedron Lett. 2006, 47, 1153–1156; (c) Wang, R.; Li,
B.-G.; Huang, T.-H.; Shi, L.; Lu, X.-X. Tetrahedron Lett. 2007, 48, 2071–2073; (d)
Kleber, C.; Andrade, Z.; Alexandre, R.; Matos, F. Synlett 2003, 1189–1191.
18. Yadav, J. S.; Reddy, B. V. S.; Gupta, M. K.; Biswas, S. K. Synthesis 2004, 2711–
2715.
19. (a) Yadav, J. S.; Reddy, B. V. S.; Eeshwaraiah, B.; Reddy, P. N. Tetrahedron 2005,
61, 875–878; (b) Yadav, J. S.; Narsaiah, A. V.; Reddy, B. V. S.; Basak, A. K.;
Nagaiah, K. J. Mol. Catal. A 2005, 230, 107–111.
20. Yadav, J. S.; Reddy, B. V. S.; Jaishri Naidu, J.; Sadashiv, K. Chem. Lett. 2004, 33,
926–927.
24. Data of representative examples: (E)-Methyl 2-(4-chlorobenzylidene)-3-
oxobutanoate (3a): Reddish solid, mp = 80 °C. 1H NMR (300 MHz, CDCl3): d
1.16 (s, 3H), 2.58 (s, 3H), 6.11–6.12 (m, 4H), 6.27 (s, 1H). 13C NMR (75 MHz,
CDCl3): d 26.5, 52.6, 129.1, 130.6, 136.8, 134.5, 140.0, 169.7, 194.3. IR (KBr):
821, 1088, 1250, 1618, 1654, 1733, 2362, 2855, 2932 cmÀ1. ESIMS: m/z 261
(M++Na): HRMS calcd for C12H11O3NaCl, 261.0294. Found 261.0289. 3-
Benzylidenepentane-2, 4-dione (5a): Yellow liquid. 1H NMR (200 MHz, CDCl3):
d 2.24 (s, 3 H), 2.38 (s, 3H), 7.36 (m, 5H), 7.44 (s, 1H): 13C NMR (75 MHz, CDCl3):
d 26.2, 31.3, 128.7, 129.4, 130.4, 132.6, 139.6, 142.5, 196.4, 205.3. IR (neat):
760, 1174, 1245, 1614, 1658, 1708, 2923, 3002 cmÀ1
: ESIMS: m/z
211 (M++Na). HRMS calcd for C12H12O2Na, 211.0734. Found 211.0735. 3-(4-
Methoxybenzylidene)pentane-2, 4-dione (7a): Yellow liquid. 1H NMR (300 MHz,
CDCl3): d 2.28 (s, 3H), 2.26 (s, 3H), 3.83 (s, 3H), 6.87 (d, J = 9.0 Hz, 2H), 7.31 (d,
J = 9.0 Hz, 2H), 7.37 (s, 1H): 13C NMR (75 MHz, CDCl3): d 26.2, 31.6, 55.3, 114.5,
125.2, 131.6, 139.7, 140.6, 161.6, 196.4, 206.1. IR (neat): 831, 1108, 1174, 1258,
21. Yadav, J. S.; Bhunia, D. C.; VamshiKrishna, K.; Srihari, P. Tetrahedron Lett. 2007,
48, 8306–8310.
22. Bartoli, G.; Bosco, M.; Carlone, A.; Dalpozzo, R.; Galzerano, P.; Melchiorre, P.;
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23. General procedure for condensation reaction:
A
1,3-dicarbonyl compound
1258, 1513, 1599, 1653, 1706, 2844, 2926, 3004 cmÀ1
.
ESIMS: m/z 241
(1 mmol) was taken in round-bottomed flask and to this was added
a
(M++Na). HRMS calcd for C13H14O3Na, 241.0840. Found 241.0833.