Mild and Efficient Method for Synthesis of Eaminones Using Ytterbium Triflate as Catalyst

Formation of 3-Aminophenols from Cyclohexane-1,3-diones

meta-Aminophenols are formed by the action of DBU on 3-amino-2-chlorocyclohex-2-en-1-ones at room temperature in MeCN. The chloro compounds are generated by treating 3-aminocyclohex-2-en-1-ones with the easily prepared halogenating agent BnNMe₃·ICl₂ in MeOH-CH₂Cl₂. The amino group must carry two substituents, either two aryl, one aryl and one alkyl, or two alkyl groups; 3-aminocyclohex-2-en-1-ones of this type are readily made from cyclohex-2-en-1-one and a primary or secondary amine.

Autocatalyzed three-component cyclization of polyfluoroalkyl-3-oxo esters, methyl ketones and alkyl amines: a novel approach to 3-alkylamino-5-hydroxy-5-polyfluoroalkylcyclohex-2-en-1-ones

A new one-pot reaction between polyfluoroalkylated 3-oxo esters, methyl ketones and primary or secondary alkyl amines is reported as an efficient approach to 3-alkylamino-5-hydroxy-5-polyfluoroalkylcyclohex-2-en-1-ones. The scope of three-component cyclization and its plausible mechanism are discussed. The described protocol makes it possible to vary the functional substituents in 2, 3 and 5 positions of carbocycles. Anhydrous conditions are necessary for the productive synthesis of aminocyclohexenones, whereas in the presence of water the competitive formation of alkyl ammonium salts of keto hydroxy carboxylates is observed. Dehydration of the aminocyclohexenones was effectively used for the synthesis of 3-alkylamino-5-trifluoromethylphenols, some of which exhibited moderate antifungal activities against eight pathogenic fungal strains.

[6π] Photocyclization to cis-Hexahydrocarbazol-4-ones: Substrate Modification, Mechanism, and Scope

Upon irradiation at λ = 366 nm, tertiary N-alkoxycarbonyl-N-aryl-β-enaminones furnished exclusively the trans-hexahydrocarbazol-4-ones by a conrotatory [6π] photocyclization but epimerized on silica to cis-hexahydrocarbazol-4-ones (14 examples, 44–98% yield). The acceptor substitution on the nitrogen atom enhanced the stability of the cyclized products compared to N-alkyl-N-aryl-β-enaminones reported previously. The mechanism of the [6π] photocyclization was investigated by quenching experiments, deuterium-labeling experiments, and DFT calculations, suggesting a triplet pathway for the conrotatory ring closure followed by a suprafacial [1,4] hydrogen migration.