Deoxygenation of Nitrobenzene by Tributylphosphine in the Presence of Alcohols. Synthesis of 2-Alkoxy-3H-azepines

Abstract Deoxygenative reduction of nitrobenzene by tributylphosphine in the presence of primary or secondary alcohols gave 2-alkoxy-3H-azepines in good yields. The use of acidic hydroxylic compounds, such as phenol or acetylacetone, in place of the alcohols did not lead to ring enlargement. Triphenylphosphine could be used as a reducing agent, but the yields of the azepines were relatively low. 2-Alkoxy-3H-azepines were converted into 2-amino-3H-azepine in good yields by the reaction with ammonium carbonate. 2,3-Dihydro-1H-azepin-2-one was prepared by the hydrolysis of 2-butoxy-3H-azepine or 2-amino-3H-azepine.