Supplementary data
Efficient, rapid avenue for synthesis of highly substituted piperidines using polystyrene sulphonic acid
Abhijeet Mulik,a* Pravin Hegade,a Dayanand Patil,b Ganpatrao Mulika, Suresh Salunkhe,a Madhukar Deshmukhb
a - PG Department of Chemistry, Balwant College Vita, Dist-Sangli, Maharashtra, India
b - Department of Chemistry, Shivaji University, Kolhapur, India.
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Experimental:
General:
All chemicals were obtained from Sigma Aldrich and used as received. Progress of reaction was monitored by TLC (Silica gel 60 F254). 1H and 13C spectra of isolated compound were reported by using CDCl3 solvent on Brucker 300MHz spectrometer with TMS as an internal standard.
Typical procedure for the synthesis of piperidine derivatives using PSSA.
A mixture of β-ketoester (1 mmol), aryl amine (2 mmol) and 30% PSSA (0.2 mL), in 5ml ethanol was stirred at RT for 20 min, then aryl aldehyde (2 mmol) was added and stirred continuously at 70°C till the completion of reaction monitored by TLC. Then reaction mass gradually cooled to RT when a solid precipitated out. It was then filtered and washed with cold ethanol. All the products obtained were recrystallized with ethanol and preceded for analysis.
Spectral data of some representative Piperidine derivatives:
Entry 1:- White crystal, MP – 185-186 oC, IR (KBr) (νmax/cm-1): 3238 (NH), 1648 (C= O); 1H NMR (300 MHz, CDCl3): δ 1.45 (t, 3H, OCH2CH3), 2.17 (s, 3H, Ar-CH3), 2.23 (s, 3H, Ar-CH3), 2.71 (m, 2H, H-5), 4.30-4.51 (dq, 2H, OCHaCHb), 5.14 (s, 1H, H-6), 6.14 (s, 1H, H-2), 6.17-7.36 (m, 18H, Ar-H), 10.23 (bs, 1H, -NH); 13C NMR (75 MHz, CDCl3): δ 14.8, 20.1, 20.8, 55.1, 58.2, 59.5, 97.6, 112.8, 125.0, 125.9, 128.1, 135.2, 135.5, 143.0, 144.3, 144.8, 156.4, 168.2.
Entry 2:- White Crystal, MP - 160-161 oC, IR (KBr) (νmax/cm-1): 1649 (C= O); 1.46 (3H, t, OCH2CH3), 1H NMR (300 MHz, CDCl3): δ 2.23 (s, 3H, Ar-CH3), 2.33 (s, 3H, Ar-CH3) 2.75 (q, 2H, H-5), 4.31-4.52 (dq, 2H, OCHaCHb), 5.10 (s, 1H, H-6), 6.35 (s, 1H, H-2), 6.38-7.39 (m, 16H, Ar-H), 10.23 (bs, 1H, -NH); 13C NMR (75 MHz, CDCl3): δ 14.8, 20.1, 20.9, 33.4, 55.1, 57.5, 59.7, 96.9, 113.0, 124.6, 125.8, 129.4, 134.2, 136.0, 144.2, 146.6, 156.1, 167.9.
Entry 3:- White Crystal, MP - 174-175 oC, IR (KBr) (νmax/cm-1): 3245 (NH), 1656 (C= O); 1H NMR (300 MHz, CDCl3): δ 2.18 (s, 3H, NH-Ar-CH3), 2.29 (s, 3H, N-Ar-CH3), 2.75 (q, 2H, H-5) 3.80 (s, 6H, Ar-OCH3), 3.92 (s, 3H, COOCH3), 5.07 (s, 1H, H-6), 6.25 (s, 1H, H-2), 6.23 (m, 2H, Ar-H), 6.33-7.28 (m, 14H, Ar-H), 10.21 (bs, 1H, -NH); 13C NMR (75 MHz, CDCl3): δ 20.1, 20.9, 33.6, 50.9, 54.6, 57.5, 60.7, 97.5, 112.9, 115.5, 124.0, 124.9, 125.9, 127.1, 128.0, 129.2, 132.0, 134.9, 144.8, 156.7, 158.0, 158.6, 168.6.
Scanned Spectra of representative compounds:
Entry 1:
IR
1H NMR
13C NMR
Entry 2:
IR
1H NMR
13C NMR
Entry 3:
IR
1H NMR
13C NMR