2,5-Dichloropyrimidine

Uses

2,5-Dichloropyrimidine acid is employed as a important raw material and intermediate used in organic synthesis agrochemical, pharmaceutical and dyestuff field.

Preparation

2,5-Dichloropyrimidine was synthesised from 2-hydroxypyrimidine hydrochloride by treatment with aqueous chlorine solution. Reaction of the product with phosphoryl chloride in the presence of N,N-dimethylaniline gave the desired product in 40% yield. The sample was then purified by sublimation.

Synthesis

Step 2: Synthesis of 2,5-dichloropyrimidine To a stirred mixed solution of (2-chloropyrimidin-5-yl)boronic acid (0.5 g, 3.164 mmol) and cuprous chloride (CuCl, 0.569 g, 6.329 mmol) in acetonitrile (MeCN, 20 mL), N-chlorosuccinimide (NCS, 0.084 g, 6.329 mmol) was slowly added. The reaction mixture was heated and refluxed at 80 °C for 16 h, during which the progress of the reaction was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the mixture was cooled to room temperature and the pH was adjusted with saturated sodium bicarbonate (NaHCO3) solution to 8. Subsequently, the reaction mixture was extracted with diethyl ether to separate the organic layer. The organic layer was washed sequentially with water and saturated saline and dried over anhydrous sodium sulfate (Na2SO4). The organic phase was concentrated under reduced pressure to give light yellow solid 2,5-dichloropyrimidine (0.2 g, 75% yield). Mass spectrometry (MS) analysis showed a molecular ion peak m/z 148.9 [M++1].

storage

Store in cool, dry place in tightly closed container. With adequate ventilation. Store away from oxidizing agent.

structure and hydrogen bonding

C₄H₂Cl₂N₂, M=148.98 monoclinic, space group P2_1/m with a=6.077(3), b=19.771(8), c=7.399(3) , β=101.23(6)°, U=872 ³ [from 2θ values of 29 reflections measured at±ω, 25 ≤2θ ≤ 38°, λ = 0.710 73, T=150.0 K], D_calc=1.702 g cm^-3, Z=6, μ =0.993 mm-1[1].

References

[1] Blake A, et al. Structure Analysis Restrained by ab Initio Calculations: The Molecular Structure of 2,5-Dichloropyrimidine in Gaseous and Crystalline Phases. The Journal of Physical Chemistry, 1996; 100: 12280–12287.