Synthesis of 3,4-Dihydrophthalazin-1(2H)-one by Zinc Reduction of Phthalazin-1(2H)-one |
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Authors: | E Bellasio |
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Institution: | Research Laboratories of “Gruppo Lepetit” , S.p.A. Via Durando, 38 - Milano, (Italy) |
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Abstract: | 3,4-Dihydrophthalazin-1(2H)-one (II) was first prepared by H.Sund 1), by electrochemical reduction of phthalazin-1(2H)-one (I) (phthalazone). In the recent years we have described new syntheses of II, through easily hydrolyzable mono- or diacetyl- derivatives, namely condensation of 2-bromomethylbenzoylchloride with N,N'-diacetylhydrazine 2) catalytic reduction of I in acetic acid 2) or of 2-acetylphthalazone in acetic anhydride 3) The reduction of I with zinc is known to proceed with ring contraction and formation of N-aminophthalimidine (III)4) (zinc and sodium hydroxide at about 100ddot]C) or of phthalimidine (IV) 5) (zinc and hydrochloric acid under unspecified conditions). Having observed that II is transformed into N-aminophthalimidine when heated with hydrazine hydrate 6) or sodium hydroxide 2), the zinc reduction of I was reinvestigated with the aim to find out in which cases the intermediate formation of II can be dem-onstratedo |
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