Suggested Improved Method for the Ing-Manske and Related Reactions for the Second Step of Gabriel Synthesis of Primary Amines

摘要

This work demonstrates an improvement in the Ing-Manske and related procedures by the increase of pH of the reaction mixture after the complete disappearance of N-substituted phthalimide.Hydrazinolysis of N-phenylphthalimide (la) gave 80% of the desired primary amines after 5.3h in the absence of added NaOH.The reaction time was reduced to 1.6 h and 1.2 h when 1 eq.and 5 eq.of NaOH were added to the reaction mixture after the complete disappearance of la.Hydroxyami-nolysis of N-(4-ethylphenyl)phthalimide (1b) gave 80% of the desired primary amines after 7.5 h of reaction time (at added [NaOH]=0).When 10eq. and 20eq. of NaOH were added to the reaction mixture after the disappearance of 1b,the reaction time was reduced to 4h and 2h,respectively.Methylaminolysis of N-(2-ethylphenyl)phthalimide (1c) gave 80% of the desired primary amines after 1.7h (at added [NaOH]=0).The reaction time was reduced to 1 h and 0.7h when 1 eq.and 25 eq.of NaOH were added to the reaction mixture after the complete disappearance of 1c.