| Popis: |
The reaction in situ of sodium borohydride with 2-methoxyethanol in THF generates NaBH2(OCH2CH2OCH3)2, which is a stronger dehalogenating agent than tetraethylene glycol (TEG)/KOH or TEG/ KOH/NaBH4 for chlorinated compounds. NaBH2(OCH2CH2OCH3)2 in THF at 68 °C dechlorinated γ-Lindane to benzene in 99% yield in 0.5 hour and α-chlorotoluene to toluene in 91% yield in 2 hours. Addition of NiCl2 greatly enhances the reactivity of NaBH2(OCH2CH2OCH3)2. Thus, NiCl2/NaBH2(OCH2-CH2OCH3), in THF at 68 °C readily dechlorinates γ-Lindane to benzene in 100% yield in 0.25 hour and α-chlorotoluene to toluene in 100% yield in one hour. This reactive dechlorination appears to be stoichiometric in NiCl2 and approaches 1:1 stoichiometry when NiCl2 was slowly added in increments or continuously added to the reaction mixture. Catalytic amounts of Bu3SnH/AIBN, also, promote the rates of these two dehalogenations. |
