Transformations of dibenzo(γ-oxopiperidino)aza-14-crowns-4 upon acylation. Molecular structure of dibenzo-16-crown-3
摘要:
The result of acylation of dibenzoaza-14-crowns-4 containing a 4-oxopiperidine fragment with acetic anhydride depends on the substituent on the nitrogen atom. The NH-substrates initially undergo acylation at the piperidine nitrogen atom, followed by enolization and O-acylation. The acylation of N-methyl derivatives is accompanied by cleavage of the piperidine ring at the C-N bond with formation of acetylamino-substituted dibenzo-16-crowns-3. The Structure of the latter was determined by X-ray analysis.
The reaction of diethyl ketone with 2-{2-[2-(2-formylphenoxy)ethoxy]ethoxy}benzaldehyde in acid medium at room temperature gave 43% of dibenzo(4-oxotetrahydropyrano)oxa-14-crown-4. The condensation of the same compounds in boiling ethanol in the presence of alkali involved cascade transformations leading to the formation of thermody namically more stable dibenzocrownophane which was assigned the structure of 8,9:15,16-dibenzo-1,4,7-trioxacyclohexadec-8,10,13,15-tetraen-12-one (yield 29%). Treatment of an alcoholic solution of the latter with gaseous ammonia or methylamine at 20C afforded 73-74% of dibenzoaza-14-crowns-4 containing a 4-oxopiperidine fragment.