Decarboxylation-triggered homo-Nazarov cyclization of cyclic enol carbonates catalyzed by rhenium complex
Decarboxylative homo-Nazarov cyclization catalyzed by a Lewis acid was achieved using a cyclic enol carbonate bearing a cyclopropane moiety as a substrate. Various substrates were converted into the corresponding multi-substituted cyclohexenones in good yieldsviadecarboxylation, followed by 6-membered ring formation involving cyclopropane-ring-opening.
Formal [4?+?4] cycloaddition of 3-arylcyclobutanones with anthracene and their acid-promoted intramolecular cyclization with skeletal rearrangement
A reaction of 3-arylcyclobutanones with anthracene in the presence of TiCl4 gave 14-aryl-9,10-dihydro-9,10-butanoanthracen-12-ones as a formal [4 + 4] cycloadduct of anthracenes with a C4 unit formed by cleaving the more substituted C2–C3 bond of cyclobutanones. On the other hand, activation of 3-arylcyclobutanones with TfOH in the absence of nucleophiles gave 2-tetralones with skeletal rearrangement.
Synthesis of Quinolines and 2H-Dihydropyrroles by Nucleophilic Substitution at the Nitrogen Atom of Oxime Derivatives
Isomerization of oxime derivatives was researched in detail to find out the methods for the syn-anti isomerization of O-substituted oximes. Based on these findings were developed simple methods for the preparation of aza-heterocycles from both stereoisomers of oximes. Quinolines were synthesized from β-aryl ketone oximes by treatment with trifluoroacetic anhydride and 4-chloranil. γ,δ-Unsaturated O-methoxyacetyloximes were transformed to 2H-dihydropyrroles by reaction with methoxy-acetic acid.
The 5-aryl-3-isopropyl-6,6-dimethyl-2-cyclohexenones 4a-f were synthesized by base-catalysed reactions of aromatic aldehydes with 3-methyl-2-butanone in ethanol/water at 70 deg C.Benzaldehyde and butanone react in the same way.Two of four possible 5-aryl-