Synthesis Of Aryl Carboxylic Ester,Quinoxaline And N-Substituted-4-Methylene Oxazolidinone

The palladium catalyzed sulfur ylide reaction is an important means of the construction of carbon-carbon and carbon-heteroatom bond,it is an important application in the synthesis and preparation of drugs,bioactive intermediates,natural products and functional organic materials.Based on their unique chemical reactivity,Study on the sulfur ylides with different ketene and o-phenylenediamine,reaction of propargyl alcohol compounds with p-toluenesulfonyl isocyanate,Extended reaction substrate range,obtained the precursor compound of synthetic drugs of aryl carboxylic ester,quinoxaline and oxazolidinone alkyl ketones.The structures of the synthesized compounds were characterized by nuclear magnetic resonance spectroscopy and mass spectrometry,individual compounds that hard to determine its structure were verified by X-single crystal diffraction.Based on the experimental results and analysis the data,the catalytic mechanism of the reaction was proposed.(1)Palladium catalyzed synthesis of aryl carboxylic acid esters by reaction of sulfur ylides with ketene.Under conditions of 60 ?,the sulfur ylides with ketene as the substrate,using Pd(PPh3)4 as catalyst,THF as reaction solvent,reaction time is 24 h,obtainded 9 aryl carboxylic ester compounds,the isolated yiled was from 64%to 85%,and determined its structure.Experimental results show that the absorption rate is higher when the benzene ring of ylieds and ketene has an electron withdrawing group,and the reaction is easier to occur.the reaction mechanism of palladium catalyzed synthesis of aryl carboxylic acid ester is proposed.Palladium catalyst is one of the key factors that induce the enol formation of intermediates,which is beneficial to the formation of products.(2)Palladium catalyzed the synthesis of quinoxaline thought cyclizing of bromo sulfide and o-phenylenediamine.With the bromo sulfide and o-phenylenediamine as substrate.Pd(PPh3)4 as catalyst,PPh3 as ligand,K2CO3 as base,THF as solvent,reaction time is 18 hours,obtained 12 quinoxaline compounds.The isolte yield was from 55%to 90%,and determined its structure.Experimental results show that if there are electron withdrawing group on the benzene ring of bromo sulfide,the yield is high,which is favorable for the reaction.Put forward the mechanism of palladium catalyzed cyclization reaction.Palladium catalyst promoted the binding of the intermediate enol form and the o-phenylenediamine,alkali plays an auxiliary role,which is favorable to the occurrence of nucleophilic reaction,generate the target products by cyclization.(3)Alkali catalyzed the synthesis of N-substituted-4-methylene-oxazolidinone compounds by cyclization of propargyl alcohol with p-toluene sulfonyl isocyanate.Using NEt3 as base catalyst,using toluene as solvent,the reaction temperature is 125 ?,reaction time is 8 hours,obtained 12 oxazolidinone compounds,the isolated yield is from 42%to 99%.Determined its structure.The results showed that both aryl propargyl alcohol and alkyl propargyl alcohol could react smoothly.The substituent groups on the aromatic ring had little effect on the reaction.Put forward the coupling cyclization mechanism of alkali catalyzed,the key factor of the alkali catalyzed cyclization is that the base can easily obtain protons,the nucleophilic addition-elimination reaction results in the formation of target products.Aryl carboxylic acid ester structure units exist in many natural products and active substances,the aryl carboxylic acid esters can be used for the synthesis of dyes,leather agents,perfumes,and pesticides that containing structural units of the aromatic carboxylic acid ester.Quinoxaline compounds are an important alkaloids that containing the nitrogen,which can be used for the synthesis of intermediates of antibacterial and antiviral,anti-inflammatory and anti-cancer drugs.For example the synthesis of the pyrazinamide class of anti tuberculosis drug.N-substituted-4-methylene-oxazolidinone heterocyclic compounds containing oxygen and nitrogen,it is widely used in the fields of fine chemicals,composite materials,pesticides,fibers,anti rust agents,reactive dyes,lubricants and pharmaceuticals.The results of this study provide a more simple and efficient method for the synthesis of these important compounds.