Reduction of three α-(o-nitrophenylthio)ketones with sodium borohydride and palladium–charcoal gave mainly α-(o-nitrophenylthio)alcohols and, as minor products, α-(o-aminophenylthio)alcohols. Only two benzothiazines were formed. Bis[2-(3-phenyl-2H-1,4-benzothiazine)] was a minor product of the catalyzed reduction of ω-(o-nitrophenylthio)acetophenone whereas 1-(3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzothiazin-2-yl)benzyl alcohol was the main product of the catalyzed reduction of α-benzoyl-α-(o-nitrophenylthio)acetate.
Treatment of (3,4-dihydro-4-hydroxy-3-oxo-2H-l,4-benzothiazin-2-yl)acetic acid ( l a ) with sodium hydroxide yields the corresponding lactam, i.e. (3,4-dihydro-3-oxo-2H-l,4-benzothiazin-2-yl)acetic acid, together with the a,D-unsaturated acid, 3,4-d1hydro-3-oxo-2H-1,4-benzoth1az1ne-A~~~-acetic acid. The 6-methyl-and 6-bronio-derivatives of In behaved similarly when reacted with sodium hydroxide but when 3,4-dihydro-4-hydroxy-3-oxo-2H-1,4-benzoth1azine was so treated a more complex reaction occurred.Methyl (6-bromo-3,4-dihydro-4-hydroxy-3-oxo-2H-I ,4-benzothiazin-2-yl)acetate was also treated with hydrochloric acid. The two products isolated were (6-bromo-3,4-d1hydro-3-oxo-2H-1,4-benzothiazin-2-yl)acetic acid and (6-bromo-7-chloro-3,4-dihydro-3-oxo-2H-1,4-benzoth1azin-2-yl)acet1c acid.The action of hydrochloric acid on 3,4-dihydro-4-hydroxy-7-methyl-3-oxo-2H-1,4-benzoth1azine also gave two products. One was the corresponding lactam; the other was unexpected and has been tentatively identified as bis[2-(3,4-dihydro-7-n1ethyl-3-0~0-2H-1,4-benzothiazine].
Die Einwirkung von NaOH auf die N‐Hydroxy‐dihydrobenzothiazinone (I) führt zur Bildung der Lactame (II) und (III); analoge Behandlung der unsubstituierten N‐Hydroxy‐Verbindung (IV) liefert die Produkte (V)‐ (VII).
Bei der Reduktion des Ketons (I) mit Na‐B‐hydrid entstehen in Abwesenheit eines Katalysators der Nitroalkohol (IIa) und in Gegenwart von Pd‐Kohle neben (IIa) geringe Mengen des Aminoalkohols (IIb).
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