Chemicals and apparatus
All chemicals were commercial products. FT-IR spectra were run on a Bruker, Equinox 55 spectrometer. A Bruker (DRX-400 Avance) NMR was used to record the 1H and 13C NMR spectra. The morphology of the particles was observed by scanning electron microscopy (SEM) under acceleration voltage of 120 kV. The XRD pattern was obtained on a Philips Xpert MPD diffractometer (Cu Ka, radiation, k¼ 0.154056 nm). Energy dispersive spectroscopy (EDS) was obtained using a Phenom pro X instrument. Thermal gravimetric analysis (TGA) was conducted using STA 504 instrument.
Preparation of NEST
Firstly, the egg shell was heated in a boiling water for 30 minutes, dried in oven 150 °C and powdered. Then, 1 g of prepared nano-egg shell powder was stirred for 30 minutes in 10 mL of dried CH2Cl2. Titanium tetrachloride (4.36 mL) was slowly added dropwise to the mixture. After stirring at room temperature for 30 minutes, the resulting product filtered and washed with dichloromethane three times. Finally, the obtained NEST was dried at room temperature for 3 hours.
General procedure for the synthesis of DHPPs
In a 100 ml round bottom flask, a mixture of aldehyde (1 mmol), malononitrile (1 mmol), hydrazine hydrate (2 mmol), ethyl acetoacetate (1 mmol) and NEST (0.06 g) was stirred at room temperature. Progress of the reaction was monitored by TLC (n-hexane: EtOAc, 4:1). After completion of the reaction, the mixture was dissolved in acetone. Then, the catalyst was filtered off and the obtained solution was poured into cold water. The obtained solid product was filtered and purified by re-crystallization from ethanol and water (5:1). The obtained NEST catalyst was then washed with EtOH, dried and reused directly for four times in other fresh reactions with negligible decreasing of the yield.
Spectroscopic data for some products
6-Amino-3-methyl-4-(3-nitrophenyl)-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (Table 2, entry 3)
White solid. M.P. 210-211 °C. FT-IR (ATR)/ ῡ (cm-1): 3484, 3231, 3120, 2190, 1645, 1597, 1519, 1491, 1410, 1351, 733. 1H NMR (400 MHz, DMSO-d6)/ δ (ppm): 1.82 (s, 3H), 4.89 (s, 1H), 7.08 (s, 2H), 7.64 -7.70 (m, 2H), 8.04 (s, 1H), 8.13-8.15 (d, J = 8 Hz, 1H), 12.23 (s, 1H).; 13C NMR (100 MHz, DMSO-d6)/δ ppm: 161.63, 155.17, 148.36, 147.32, 136.38, 134.88, 130.47, 122.33, 121.01, 97.15, 56.59, 36.11, 10.25.
6-Amino-3-methyl-4-(4-nitrophenyl)-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (Table 2, entry 5)
White solid. M.P. 239-242 °C. FT-IR (ATR)/ ῡ(cm-1): 3475, 3227, 3106, 2195, 1646, 1592, 1513, 1399, 1348, 1163, 1109, 810, 744.; 1H NMR(400 MHz, Acetone-d6)/ δ ppm: 2 (s, 3H), 4.88 (s, 1H), 6.30 (br s, 2H), 7.55 (d, J = 8 Hz, 2H), 8.23 (d, J = 8 Hz, 2H), 11.43 (s, 1H). 13C NMR (100 MHz, DMSO-d6)/δ ppm: 161.62, 155.15, 152.59, 146.85, 136.36, 132.19, 129.32, 124.38, 120.98, 97.04, 56.37, 36.36, 10.22.
6-Amino-4-(4-hydroxyphenyl)-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (Table 2, entry 9)
White solid. M.p. 222-224 °C. FT-IR (ATR)/ ῡ(cm-1): 3372, 3304, 3127, 2173, 1645, 1594, 1510, 1489, 1441, 1404, 1189, 1166, 1041, 809. 1H NMR (400 MHz, Acetone-d6)/ δ(ppm): 1.74 (s, 3H), 4.44 (s, 1H), 6.65 (dd, J=7.5 Hz, J=3.7 Hz, 2H), 6.76 (br s, 2H), 6.91 (dd, J=7.5 Hz, J=3.7 Hz, 2H), 9.27 (s, 1H), 12.02 (s, 1H).; 13C NMR (100 MHz, DMSO-d6)/δ ppm: 161.10, 156.49, 155.22, 135.98, 135.24, 128.92, 121.40, 115.58, 98.54, 58.21, 35.95, 10.24.
6-Amino-4-(2,4-dichlorophenyl)-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (Table 2, entry 11)
Pale yellow solid. M.P. 223-225 °C. FT-IR (ATR)/ ῡ(cm-1): 3482, 3243, 3115, 2186, 1638, 1587, 1491, 1408, 1100, 1052, 866, 741.; 1H NMR (400 MHz, DMSO-d6)/δ ppm: 1.85 (s, 3H), 5.13 (s, 1H), 7.07 (s, 2H), 7.29 (d, J = 8 Hz, 1H), 7.47 (dd, J = 8.4 Hz, J = 2 Hz, 1H), 7.65 (d, J = 2.4 Hz, 1H), 12.23 (s, 1H).; 13C NMR (100 MHz, DMSO-d6)/δ ppm: 161.30, 154.88, 140.07, 135.44, 132.81, 132.10, 128.83, 128.02, 120.25, 96.32, 55.21, 33.07, 9.53.