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H syn-Aldoxime (2) reagieren glatt mit 3-Chlor-1.2-benzisothiazol-S.S-dioxid (1) zu [I .2-Benzisothiazolyl-(3)-oximino]-aIkan-S.S-dioxiden (31, deren Beckmann-Umlagerung mit der Nitrilbildung (Beckmann-Fragmentierung) konkurriert. -Die Nitrilbildung ist cine Reaktion erster Ordiiung, dcren Gcschwindigkeitskonstante vom Losungsmittel abhangt. Auch in Substanz gelingt die praparative Nitrildarstellung. ~ Bei der lichtinduzierten Beckmrinn-Fragmentierung in fester Phase treten Radikale auf. ~-Eine thermische Umlagerung in Acetonitril fiihrt zu 2-[4-Dialkylamino-phenyIiminomethyl]-saccharin (8). Rearrangement and Elimination Reactions with Products from Condensing J-Chloro-1,2-benzisothiazole S,S-Dioxides with Aldoximessyn-Aldoximes (2) react smoothly with 3-chIoro-1,Z-benzisothiazole S,S-dioxide (1) to yield [ 1,2-benzisothiazol-3-yloximino]-alkane S,S-dioxides (3), whose Beckmann-rearrangeinent is i n competition with nitrilc formation (Berlo72ann-fragmentation). -Nitrilc formation is a first order reaction, the velocity constant depending on the solvent. In the solid state, too, nitriles can so be prepared in a preparative way. ~~ Light induced Beckmnnn-fragmentation in the solid state is accompanied by radical formation. ~ A thermal rearrangement in acetonitrile produces 2-(4-dialkylaminophenylirninomethyl)saccharin (8).
H syn-Aldoxime (2) reagieren glatt mit 3-Chlor-1.2-benzisothiazol-S.S-dioxid (1) zu [I .2-Benzisothiazolyl-(3)-oximino]-aIkan-S.S-dioxiden (31, deren Beckmann-Umlagerung mit der Nitrilbildung (Beckmann-Fragmentierung) konkurriert. -Die Nitrilbildung ist cine Reaktion erster Ordiiung, dcren Gcschwindigkeitskonstante vom Losungsmittel abhangt. Auch in Substanz gelingt die praparative Nitrildarstellung. ~ Bei der lichtinduzierten Beckmrinn-Fragmentierung in fester Phase treten Radikale auf. ~-Eine thermische Umlagerung in Acetonitril fiihrt zu 2-[4-Dialkylamino-phenyIiminomethyl]-saccharin (8). Rearrangement and Elimination Reactions with Products from Condensing J-Chloro-1,2-benzisothiazole S,S-Dioxides with Aldoximessyn-Aldoximes (2) react smoothly with 3-chIoro-1,Z-benzisothiazole S,S-dioxide (1) to yield [ 1,2-benzisothiazol-3-yloximino]-alkane S,S-dioxides (3), whose Beckmann-rearrangeinent is i n competition with nitrilc formation (Berlo72ann-fragmentation). -Nitrilc formation is a first order reaction, the velocity constant depending on the solvent. In the solid state, too, nitriles can so be prepared in a preparative way. ~~ Light induced Beckmnnn-fragmentation in the solid state is accompanied by radical formation. ~ A thermal rearrangement in acetonitrile produces 2-(4-dialkylaminophenylirninomethyl)saccharin (8).
The 2-halo imidoyl chlorides 7 are obtained from the amide 5 and the 2-halo amides 6 by the action of phosphorus pentachloride and thionyl chloride, respectively. Non-racemic (S)-6a is converted into 7a which is racemic, however. The reaction of Lawesson's reagent with 6a furnishes the diastereomeric 1,3.2-thiazaphospholidine derivatives 15. Treatment of (S)-6a (98% eel with methyl triflate affords 2-chloro imidate 8 (95% eel which reacts with methanamine in the presence of methanammonium chloride to yield the 2-chloro amidine (S)-9a (90% eel. The 2-halo imidoyl halides 7a and b react with methanamine to produce the 2-halo amidines 9a and b. -Strong bases, e.g. potassium tert-butoxide or sodium hydride in the presence of catalytic amounts of tertbutyl alcohol, eliminate hydrogen chloride or bromide from the 2-halo amidines 9a and band (S)-9a to yield mixtures of Recently, we demonstrated that the formation of the chiral non-racemic aziridinone (R)-2 from the a-chloro amide (5)-1 by base-promoted dehydrochlorination[2) as well as the nucleophilic cleavage of the N-C(3) bond of (R)_2 [3,4) occur with inversion of configuration, thus excluding the intervention of achiral (acyclic) intermediates. In the temperature range of lOO-170°C, however, slow racemization accompanies the thermolysis of (R)-2 and indicates the existence of an achiral or a racemic transient, e. g. (M)-3 + (P)-3. Indeed, high-level quantum-chemical calculations reveal that an activation energy of (170 ± 25) kJmol-1 is required for the unimolecular ring opening of the parent aziridinone which affords a species of high diradical character[41. Subsequently, the unstable N-phenylaziridinone invoked in the decomposition of the (5)-2-bromopropananilide anion was shown to react with tert-butylamine or dimethylformamide with inversion of configuration at C(3)[5 1 . Thus, the stereochemical evidence in the series of 3-alkylaziridinones excludes achiral (acyclic) aziridinone isomers as intermediates at low tempera tures [6J. Similar stereochemical studies are still missing in the related series of iminoaziridines. Therefore, we report on the synthesis and thermolysis of the diastereomeric chiral racemic (E)-and (Z)-(4)[71 and non-racemic iminoaziridines (E,R)-and (Z,R)-4. Racemic Iminoaziridines (E)-and (Z)-4Though a photochemical route to the iminoaziridines (E)-and (Z)-4 has been devised more recently, i. e. the pho- ..
The reaction of diphenylacetothioanilide with diethyl azodicarboxylate and triphenylphosphine gave rise to the formation of diphenylketene(N-phenyl)imine. Similarly, the reaction of N-(p-tolyl)diphenylacetothioamide gave diphenylketene(N-p-tolyl)imine. On treatment with diethyl azodicarboxylate in the presence of sodium ethoxide, diphenylacetothioanilide afforded bis(N-phenylbenzalimidoyl) disulfide in a good yield. The intermediate of the formation of the ketenimines is also discussed.
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