It seems the Pd/C hydrogenation is the best of all. Try higher pressure and larger vessel. It helps often for my works.
>From: Maringanti Krishna <email@example.com>
>Subject: ORGLIST:Nitrogroup reduction
>Date: Thu, 6 May 2004 05:49:53 -0700 (PDT)
>I need to reduce an aromatic nitro group to -NH2. It is a large molecule and I have an Acetal and t-BOC protections elsewhere. I have tried the following methods.
>1. Raney Nickel, Hydrogenation: Several spots on TLC (after complete disappearance of starting material, and after 48 hours)
>2. Pd/C Hydrogenation...very low yield after 48 hours
>3. Pd/C hydrazine hydrate. Reaction is OK but, the yield is verylow. Difficult to get pure product. Also, acetal deprotection
>4. Electrolytic iron/ ammonium acetate and ammonium chloride. Acetal deprotection is occuring. At rt. reaction is extremely sluggish. At reflux, acetal deprotection is taking place.
>Can someone suggest an alternative method?
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