Synthesis
GENERAL METHOD: A mixture of cyclohexanone (1 mmol), malononitrile (1 mmol), elemental sulfur (1 mmol) and BSA (20 mg) was dissolved in 1 mL of DMF. The reaction was carried out at 50 °C and 200 rpm. Upon completion of the reaction, BSA was removed by filtration to terminate the reaction. For high yield products, the reaction mixture was poured into water to precipitate the solid product, which was subsequently filtered and dried. For low yield products, the crude product was purified by rapid column chromatography on silica gel with the eluent being a mixed petroleum ether/ethyl acetate solvent. The structure of the product was confirmed by IR, 1H NMR and 13C NMR spectra.1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were recorded on a Bruker Avance 400 spectrometer using CDCl3 as the solvent and TMS as the internal standard.IR spectra were obtained by a Nicolet Nexus 470 FT-IR spectrophotometer. HPLC analyses were performed using an Agilent 1100 series system equipped with an Agilent TC-C18 column (for 3a, 3c, 3e, 3g, 3i, 3k: methanol/water = 60/40 at a flow rate of 1.0 mL/min with a detection wavelength of 220 nm; for 3b, 3d, 3f, 3h, 3j, 3l: methanol/water = 60/40 at a flow rate of 1.0 mL/min). (1.0 mL/min, detection wavelength 229 nm). All solvents used for column chromatography were distilled and purified before use.2.2.1. 2-Amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile (3a) is a yellow solid with a melting point of 140-142 °C (literature values 144-146 °C).IR (KBr): 3447, 3329, 2198 cm-1.1H NMR (400 MHz, CDCl3): δ 4.62 (broad peak, 2H), 2.53-2.46 (multiple peaks, 4H), 1.85-1.73 (multiple peaks, 4H).13C NMR (100 MHz, CDCl3): δ 159.9, 132.4, 120.7, 115.5, 88.8, 24.5, 24.1, 23.4, 22.1.
References
[1] Journal of Molecular Catalysis B: Enzymatic, 2013, vol. 95, p. 29 - 35
[2] Synlett, 2010, # 9, p. 1351 - 1354
[3] Synthetic Communications, 2010, vol. 40, # 14, p. 2067 - 2074
[4] Applied Organometallic Chemistry, 2018, vol. 32, # 5,
[5] Patent: WO2005/44008, 2005, A2. Location in patent: Page/Page column 91
