Reactions of 2,3-dihydro-1H-cyclohepta[b]pyrazines with acyl halides

2 When3-dihydro-1H-cycloheptab]pyrazine ( 3 ) was treated with acetyl chloride under the Friedel-Crafts conditions, its pyrazine ring opened to afford 2-N'-acetyl-(2-aminoethyl)amino]tropone. Reactions with propionyl and butyryl chloride also gave similarly ring-opened products. On the other hand, aromatic benzoyl chlorides reacted with compound 3 to afford N-benzoyl-substituted 2,3-dihydro-1H-cycloheptab]pyrazines, in addition to ring-opened compounds.