Über die gemeinsame Einwirkung von elementarem Schwefel und gasförmigem Ammoniak auf Ketone, XXXIV. Dihydro‐1.4‐thiazine und Thiazolo[2.3‐c]‐1.4‐thiazine aus α‐Mercaptoketonen und Äthylenimin

Abstract

Durch Umsetzung von primären, sekundären und tertiären α‐Mercaptoketonen mit Äthylenimin erhält man je nach Wahl der Reaktionstemperatur und des Molverhältnisses der Reaktionskomponenten Dihydro‐1.4‐thiazine oder Thiazolo[2.3‐c]‐1.4‐thiazine; letztere können auch aus Dihydro‐1.4‐thiazinen mit α‐Mercaptoketonen gewonnen werden. Sowohl Dihydro‐1.4‐thiazine als auch Thiazolo[2.3‐c]‐1.4‐thiazine lassen sich durch Erhitzen mit Ameisensäure zu den entsprechenden Thiomorpholinen bzw. zu Perhydro‐thiazolothiazinen reduzieren.

Enantioselective Synthesis of Thiomorpholines through Biocatalytic Reduction of 3,6-Dihydro-2H-1,4-thiazines Using Imine Reductases

“…Since 3,6-dihydro-1,4-thiazines with only one substituent in 6-position are known to undergo tautomerization and, thus, furnish the resulting endo -cyclic enamine structure as a favored product, we investigated if also the 6,6-disubstituted analogues 1a–e synthesized in our studies shows a similar tautomerization effect. This study was done via 1 H NMR spectroscopy using the 3,6-dihydro-2 H -1,4-thiazine 1a as a model substrate.…”

“…The aim of this work was to investigate and realize an IRED-catalyzed reduction of 3,6-dihydro-2 H -1,4-thiazines. Toward this end, first, various prochiral and chiral 1,4-thiazines, which then serves as substrates for the biotransformations, were synthesized according to a procedure developed already decades ago by the Asinger group . The desired 1,4-thiazines 1a–e were obtained in moderate to good yields from their corresponding α-chloroketones and cysteamine or cysteine methyl ester (Scheme ).…”

“…By storing 1a in deuterated methanol, a hydrogen-deuterium exchange at the methyl group in 5-position was observed, which leads to a disappearance of the methyl group in the 1 H NMR spectra. Thus, there is an equilibrium between the imine and the exo -cyclic enamine structure, which is in accordance with the earlier findings of Asinger with the formation of the endo -cyclic enamines …”

Imines, Cyclic

“…The di-or tetrahydro-1,4-thiazine skeleton is obtained if mercaptans which have a carbonyl group in the β-position react with ethyleneimine (120)(121)(122)(123)(124) The reaction of thioethers with ethyleneimine in the presence of acid yields sulfonium compounds. The reaction is reversible under alkaline conditions (125).…”