Hydroxynitrilium ions as intermediates in the reaction of nitroderivatives with aromatics

Cyclization of Nitroacetamide Derivatives with a Tethered Phenyl Ring in Triflic Acid

“…4 The configuration of the oxime is indirect evidence of the existence of a reactive transient species with a CN triple bond. 5 The protonation/dehydration of N,S-or S,S-nitroketene aminals 3 in triflic acid initially affords cations 4, then the stable hydroxyiminium cations 5 that have been characterized by 1 H NMR and 13 C NMR spectroscopy at low temperature.…”

“…In triflic acid or in HF-SbF 5 , ethyl 2-nitroacetate (1) undergoes protonation and the loss of a molecule of water to afford a transient reactive hydroxynitrilium ion (protonated nitrile oxide) able to react with aromatics to form, for instance, ethyl (2E)-2-hydroxyimmino-2-phenylacetate (2, Ar = Ph; Scheme 1). 4 The configuration of the oxime is indirect evidence of the existence of a reactive transient species with a CN triple bond. 5 The protonation/dehydration of N,S-or S,S-nitroketene aminals 3 in triflic acid initially affords cations 4, then the stable hydroxyiminium cations 5 that have been characterized by 1 H NMR and 13 C NMR spectroscopy at low temperature.…”

Superacid and thiol-ene reactions for access to psammaplin analogues with HDAC inhibition activities

“…The final oxime can exist as an E/Z mixture. 38 SAR studies on psammaplins showed that the aromatic ring can be substituted with no more than two groups. The scope of our strategy was determined with various activating (hydroxy, alkyloxy, alkyl) or deactivating (halogen, nitro) substituents.…”

“…Transamidation with basic monoamine (allyl-or benzylamine) under heating gave the expected amides 9a,b in moderate to good yields and the reaction times were shortened under microwaves irradiations as expected (1 h at 100 C under 300 W). In their reported work, Ferroud et al 38 used ethyl acetate as a model for amidation and with benzylamine, the corresponding amide was obtained with a yield of 72%, at 200 C and 200 W for 2.5 min. For vinylacetate, 1 h was required.…”

α‐Electrophilic Reactivity of Nitronates

“…Better yields were achieved with moderate (e. g. R′=H) to good electron‐donating aromatics (e. g. R′=Me, OMe) and EWG‐substituted nitro compounds 36 (R=CO 2 Et, ArC(O)). Proposed mechanism involves generation of hydroxy‐nitrilium cation D followed by Friedel‐Crafts type reaction . Thus, electron‐accepting substituents R are desired to enhance electrophilicity of D .…”