Preparation of 3-pyridyl isothiocyanate_industrial additives

Preparation background and overview of 3-pyridyl isothiocyanate

3-Pyridylisothiocyanate is an organic intermediate that can be used to prepare thiourea. 3-Pyridyl isothiocyanate can be prepared from 3-aminopyridine and phenoxysulfonyl chloride or carbon disulfide.

Preparation of 3-pyridyl isothiocyanate

Preparation Report 1 of 3-pyridyl isothiocyanate,

Step 1: Weigh phenoxysulfonyl chloride (2mmol) and 3-aminopyridine (4mmol), add them to a single-necked flask containing dichloromethane (10 mL), and stir the reaction at 25°C. 2 hours. Stop the reaction, add 1M dilute hydrochloric acid (10mL) and dichloromethane (10mL), extract and separate the organic phase, wash with water and dry over anhydrous sodium sulfate, and evaporate the solvent under reduced pressure to obtain N‑(3‑pyridyl)‑O‑phenyl. Thioamide intermediate, yield 72%.

Step 2: Weigh the above N‑(3‑pyridyl)‑O‑phenylthioamide intermediate (1mmol) and sodium hydroxide (1.2mmol), and add them to dichloromethane (5mL) respectively. ) in a single-necked flask with rhodium tetrafluoroborate and stir for 1 hour at 25°C. Stop the reaction, add water (10 mL) and dichloromethane (15 mL), extract and separate the organic phase, extract the aqueous phase with dichloromethane (15 mL), combine the organic phases, wash with saturated brine (15 mL), and anhydrous sodium sulfate. dry. After column chromatography separation (ethyl acetate: petroleum ether = 1:5), 3-pyridine isothiocyanate was obtained with a yield of 85%. ¹HNMR(300MHz, CDCl₃)δ8.55(d,J＝2.1Hz,1H),8.51(dd,J＝4.8,1.5Hz,1H), 7.55-7.51(m,1H),7.34-7.30(m,1H);¹³CNMR(75MHz, CDCl₃)δ147.6,147.1,139.2,132.4, 129.6, 124.0;MS(EI):m/z136(M+,100).

Preparation report 2 of 3-pyridyl isothiocyanate,

Add 152mg (2mmol) CS₂ dropwise to 188mg (2mmol) 3-aminopyridine and 606mg (6mmol) N-methylmorpholine in dichloromethane that has been cooled to -5°C. (10 mL) solution, after the dropwise addition is completed, raise the temperature to room temperature, react for 2 hours, then cool to -5°C, add 368 mg (2 mmol) neopentyl glycol phosphoryl chloride, complete the addition, naturally rise to room temperature, and react for 2 hours. Add 10 mL of water to the reaction solution, separate the layers, extract the water phase twice with dichloromethane, combine the organic phases, dry over Na₂SO₄, filter, concentrate, and column layer After analytical purification, 3-pyridyl isothiocyanate was obtained with a yield of 91%. IR (ATR): 2177 (NCS), 2037 (NCS), 1511 cm^–1. ¹H NMR( MHz, CDCl₃): δ = 8.71 (s, 1H, CHPy), 8.66-8.69 (m, 1H, CHPy), 7.56–7.61( m,2H,CHPy).

References

[1] [China invention, China invention authorization] CN201310012619.X A two-step method for synthesizing isothiocyanate

[2] [Chinese invention] CN201910083019.X A joint preparation method of isothiocyanate and phosphorus, nitrogen, and sulfur dimethyl sulfoxide flame retardant