Synthesis of α-phenylchalcogeno acetic acids, ethyl-α-phenylchalcogeno acetates and ethyl-α-halo-α-phenylchalcogeno acetates

Abstract

Reaction of phenyltellurolate or phenylselenolate anion with α-bromoacetic acid under phase transfer conditions using a liquid—solid system affords the α-phenyltelluro acetic acid and the α-phenylseleno acetic acid in 44 and 50% yields respectively. Under similar reaction conditions, phenyl chalcogenate anions react with ethyl α-bromoacetate to give the corresponding ethyl-α-phenyltelluro acetate in 52% and ethyl-α-phenylseleno acetate in 47% yield. Reaction of phenylselenenyl chloride with ethyl diazoacetate in THF at 0°C yields exclusively the ethyl-α-chloro-α-phenylseleno acetate in 88% yield. Similar reactions performed by addition of phenylselenenyl bromide in THF or benzene to the ethyl diazoacetate at different temperatures result in mixtures of ethyl-α-bromo-α-phenylseleno acetate and ethyl-α,α-bis(phenylseleno) acetate in different ratios. However, when the ethyl diazoacetate was slowly added to a solution of phenylselenenyl bromide in benzene under reflux, the ethyl-α-bromo-α-phenylseleno acetate was obtained in 84% yield as the only product. Reaction of ethyl diazoacetate with phenyltellurenyl bromide in benzene at room temperature results in formation of ethyl-α-bromo-α-phenyltelluro acetate that decomposes rapidly into the corresponding tellurone. Addition of ethyl diazoacetate to a mixture of diphenyldiselenide and copper sulfate in benzene under reflux results in a mixture of ethyl-α-phenylseleno acetate: ethyl-α,α-bis(phenylseleno) acetate (10:1). Using an alternative route, the ethyl-α-phenylseleno acetate was obtained in 74% yield by esterification of α-phenylseleno acetic acid in benzene with ethanol / sulfuric acid. The ethyl-α-phenylseleno acetate was transformed into the ethyl-bromo-α-phenylseleno acetate in 41% yield by treatment with N-bromosuccinimide. On the other hand, the copper-catalyzed thermal reaction of ethyl diazoacetate with diphenyl ditelluride in benzene afforded the corresponding ethyl-α-phenyltelluro acetate as the only product.