Alkoxy- and halogeno-selenocyanation of olefins with copper(II) chloride or bromide and potassium selenocyanate

Abstract

Treatment of olefinic hydrocarbons with copper(II) chloride or bromide and potassium selenocyanate in alcohols readily affords the corresponding vicinal alkoxyselenocyanatoalkanes (A) in good yields, while in acetonitrile vicinal halogenoselenocyanatoalkanes (B) are formed in satisfactory yields. In the cases of cyclohexene and octenes, the formation of (B) together with (A) was observed in alcohol when the reaction was stopped after a short time, (B) being converted into (A) by prolonging the reaction. The reaction proceeds through oxidation of selenocyanate anion to the corresponding cation and its electrophilic attack on the olefin, followed by competitive addition of alcohol and complexed halide anion, such as Cu₂X_3^–. The route of the substitution of halogen in (B) by an alkoxy group giving (A) has also been elucidated. The conversion of (B) obtained from cyclohexene into (A) occurs with complete retention of configuration (trans→trans), suggesting the intervention of an episelenonium ion intermediate.