K. C. Majumdar et al. / Tetrahedron Letters 51 (2010) 3372–3375
3375
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then with 5% aqueous NaOH (2 Â 20 mL). The organic layer was dried (Na2SO4)
and the solvent was evaporated under reduced pressure. The residue was
purified by column chromatography over silica-gel using pet. ether–
ethylacetate (9:1) as an eluent. Compound 2a: Gummy, yield = 75%, IR (KBr):
7. Illuminati, G.; Mandolini, L. Acc. Chem. Res. 1981, 14, 95.
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9. (a) Majumdar, K. C.; Samanta, S.; Chattopadhyay, B. Tetrahedron Lett. 2009, 50,
4866–4869; (b) Majumdar, K. C.; Chattopadhyay, B.; Samanta, S. Tetrahedron
Lett. 2009, 50, 3178–3181.
2216, 1662, 1592. cmÀ1 1H NMR (400 MHz, CDCl3): dH = 7.72 (d, 1H, J = 7.6 Hz),
,
7.65–7.66 (m, 1H), 7.52–7.53 (m, 2H), 7.36–7.39 (m, 4H), 7.16–7.26 (m, 4H),
6.83 (t, 1H, J = 7.2 Hz), 3.98–4.06 (m, 1H), 3.69–3.78 (m, 1H), 3.61 (d, 1H,
J = 16.4 Hz), 3.55 (d, 1H, J = 16.4 Hz), 1.17 (t, 3H, J = 7.2 Hz). Anal. Calcd for
C24H20INO: C, 61.95; H, 4.33; N, 3.01. Found: C, 61.86; H, 4.18; N, 2.83.
General procedure for the reductive Mizoroki–Heck cyclization of compound 2a:
10. Donets, P. A.; Eycken, E. V. V. Org. Lett. 2007, 9, 3017–3020.
11. (a) Majumdar, K. C.; Chattopadhyay, B.; Ray, K. Tetrahedron Lett. 2007, 48,
7633–7636; (b) Majumdar, K. C.; Chattopadhyay, B.; Sinha, B. Tetrahedron Lett.
2008, 49, 1319–1322; (c) Majumdar, K. C.; Chattopadhyay, B. Synlett 2008,
979–982; (d) Majumdar, K. C.; Debnath, P. Tetrahedron 2008, 64, 9799–9820;
(e) Majumdar, K. C.; Chakravorty, S.; Ghosh, T.; Sridhar, B. Synlett 2009, 3127–
3130; (f) Majumdar, K. C.; Chakravorty, S.; De, N. Tetrahedron Lett. 2008, 49,
3419–3422; (g) Majumdar, K. C.; Chakravorty, S.; Ray, K. Synthesis 2008, 2991–
2995; (h) Majumdar, K. C.; Chakravorty, S.; Shyam, P. K.; Taher, A. Synthesis
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Tetrahedron 2009, 65, 2751–2756.
A
mixture of the compound 2a (100 mg, 0.21 mmol), HCOONa (21.9 mg,
0.32 mmol), Pd(PPh3)4 (7.4 mg, 6.4 Â 10À3 mmol) in DMF/H2O (10 mL, 7:3) was
heated with continuous stirring at 100 °C for 30 min. After completion of the
reaction as monitored by TLC, the reaction mixture was cooled and water
(5 mL) was added. This was then extracted with CHCl3 (3 Â 15 mL). The CHCl3
extract was washed with water (2 Â 10 mL) followed by brine (10 mL). The
organic layer was dried (Na2SO4). Evaporation of CHCl3 furnished a crude mass.
This was purified by column chromatography over silica-gel. Elution of the
column with pet. ether–ethyl acetate (9:1) afforded the product 3a. Compound
12. General procedure for the preparation of the amide 2a:
3a: White solid, yield = 65%, mp 126–128 °C, IR (KBr): 1651, 1592 cmÀ1 1H
,
A mixture of 2’-iodophenylacetic acid (500 mg, 1.9 mmol) and SOCl2 (5 ml) was
stirred at 100 °C for 3 h. After evaporation, the residue was dissolved in CHCl3
(20 mL). A solution of amine 1a (421 mg, 1.9 mmol) in CHCl3 (20 mL) and
tetrabutylammonium hydrogensulfate (catalytic amount) were added to the
stirred solution of the acid chloride. To this reaction mixture an aqueous
solution of K2CO3 (526 mg, 3.8 mmol) was added slowly. After stirring for 4.5 h
at room temperature, the solution was washed with 5% HCl (2 Â 20 mL) and
NMR (400 MHz, CDCl3): dH = 7.54 (dd, 1H, J = 1.2 Hz, 7.6 Hz), 7.35–7.48 (m, 3H),
7.27–7.34 (m, 3H), 7.04–7.23 (m, 4H), 6.78–6.81 (m, 2H), 6.78 (s, 1H), 3.61–
3.65 (m, 1H), 3.53 (d, 1H, J = 14.0 Hz), 3.35 (d, 1H, J = 14.0 Hz), 3.02–3.11 (m,
1H), 0.93 (t, 3H, J = 7.2 Hz). 13C NMR (125 MHz, CDCl3): dC = 169.5, 142.0, 141.0,
139.3, 136.4, 135.4, 133.6, 131.1, 131.2, 130.9, 129.1, 129.0, 128.5, 128.3, 128.2,
128.1, 127.6, 127.5, 125.1, 43.7, 42.6, 14.1. MS (EI): m/z = 339 [M+]. Anal. Calcd
for C24H21NO: C, 82.92; H, 6.24; N, 4.13. Found: C, 82.74; H, 6.18; N, 4.06.