Preparation
Obtained by chlorination of uracil. Add uracil, phosphorus trichloride, and xylene amine into the reaction pot, heat to 130 ℃, reflux for about 45min, slightly cool, put in crushed ice, that is, the precipitation of purple solid, filtered while hot and not dissolved, washed with ice water, vacuum drying, a kind of purple crude, decolorized with petroleum ether (boiling range of 60-90 ℃), recrystallized, obtained 2,4-dichloropyrimidine.
Reactivity Profile
The reaction of N-substituted cyclic amines with 2,4-dichloroquinazoline and 2,4-dichloro-5-methyl-pyrimidine afforded 2-amino-4-chloroquinazolines and 2-amino-4-chloro-5-methylpyrimidines, respectively—the reaction of these amines with 2,4-dichloropyrimidine 3a afforded not only 2-amino-4-chloropyrimidines but also the isomeric 4-amino-2-chloropyrimidines. An effective one-pot, regioselective double Suzuki coupling of 2,4-dichloropyrimidine has been developed. This method enables the quick and efficient synthesis of diarylated pyrimidines. The choice of solvent proved critical to the success of this reaction sequence, with alcoholic solvent mixtures affording much greater reactivity and correspondingly lower temperatures than polar aprotic solvents[5-6].
Synthesis
The general procedure for the synthesis of 2,4-dichloropyrimidine from pyrimidine-2,4(1H,3H)-dione is as follows: in a 500 mL two-necked round-bottomed flask equipped with a condenser tube, pyrimidine-2,4(1H,3H)-dione (100 g, 0.82 mol) was dissolved in phosphoryl chloride (400 mL). The reaction mixture was refluxed with stirring at 110°C for 3.5 hours. Upon completion of the reaction, unreacted phosphoryl chloride was removed by distillation at 50°C under reduced pressure. The reaction was quenched by slowly pouring the residue into 50 g of ice, followed by extraction with chloroform (3 x 50 mL). The organic phases were combined, washed with dilute sodium carbonate solution and dried with anhydrous sodium sulfate. Finally, the solvent was removed by distillation under reduced pressure to give the target product 2,4-dichloropyrimidine.
References
[1] DR. AGNES FIZIA. Cyclopalladation in the Periphery of a NHC Ligand as the Crucial Step in the Synthesis of Highly Active Suzuki–Miyaura Cross-Coupling Catalysts[J]. Chemistry - A European Journal, 2017. DOI:
10.1002/chem.201702877.
[2] FABIAN BRUENING Lucie E L. Highly Regioselective Organocatalytic SNAr Amination of 2,4-Dichloropyrimidine and Related Heteroaryl Chlorides[J]. European Journal of Organic Chemistry, 2017. DOI:
10.1002/ejoc.201700459.
[3] ANDERSONSAMANTHA C HandyScott T. One-pot Double Suzuki Couplings of Dichloropyrimidines.[J]. Synthesis-Stuttgart, 2010. DOI:
10.1055/s-0030-1258150.
[4] TOMá? KUBELKA. Synthesis of 2,4-Disubstituted Pyrimidin-5-yl C-2′-Deoxyribonucleosides by Sequential Regioselective Reactions of 2,4-Dichloropyrimidine Nucleosides[J]. European Journal of Organic Chemistry, 2010. DOI:
10.1002/ejoc.201000164.
