| 摘要 |
PURPOSE: To obtain pyrazines useful as an intermediate for perfumes, medicines and agrochemicals by multi-stage vapor-phase catalytic reaction using a diamine and a diol as raw materials without feeding hydrogen during the reaction. CONSTITUTION: (A) A diamine of formula I (R<1> and R<2> are each H or a lower alkyl) and (B) a diol of formula II (R<3> and R<4> are each H or a lower alkyl) are subjected to cyclodehydration in a vapor phase and further partially dehydrogenated. Then, the prepared gas formed by the reaction is brought into contact with (C) a noble metal (except copper)-containing catalyst (preferably one obtained by supporting a noble metal on at least one carrier selected from among alumina, zirconia and silicon carbide) to give (D) a pyrazine of formula III. The noble metal of the component C is preferably treated with hydrogen and is preferably silver. The component C is preferably obtained by supporting the alkaline (earth) metal, zinc, etc., together with the noble metal component on the carrier. |
