Synthesis and properties of cross-conjugated ω,ω′-bis-dimethylamino ketones and dinitriles with N-acetyl- and N-benzylpiperidine cycles

• Published in: Russian chemical bulletin Vol. 60; no. 10; pp. 2014 - 2020
• Main Authors: Krasnaya, Zh. A., Tret’yakova, E. O., Kachala, V. V., Zlotin, S. G.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.10.2011
• Subjects: Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Full Articles; Inorganic Chemistry; Organic Chemistry; ketocyanines; protonation; polymethine salts; methylation; malononitrile; cyanines; absorption spectra
• ISSN: 1066-5285; 1573-9171
• DOI: 10.1007/s11172-011-0306-5

Reactions of N -acetyl- and N -benzyl-4-piperidones with aminal of β-dimethylaminoac-rolein yielded ketocyanines bearing piperidine cycle. Reaction of 3-dimethylamino-1,1,3-trimethoxypropane with 1-acetylpiperidin-4-ylidenemalononitrile in the presence of ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF 4 ), resulted in cross-conjugated ω,ω’-dimethylamino dinitrile. Protonation of ketocyanines bearing N -acetyl- and N -benzyl-piperidine cycles with Et 2 O·HBF 4 (1 equiv.) furnished piperidinium salts, while protonation of the latter with Et 2 O·HBF 4 (2 equiv.) afforded doubly charged 4-hydroxypolymethine salts. Unlike protonation, reaction of 3,5-bis(3-dimethylaminoprop-2-enylidene)-1-acetylpiperidin-4-one with Me 2 SO 4 involved only the oxygen atom and led to a singly charged 4-methoxypolymethine salt. Methylation of 3,5-bis(3-dimethylaminoprop-2-enylidene)-1-benzylpiperidin-4-one with Me 2 SO 4 (1 equiv.) involved cyclic nitrogen atom and resulted in piperidinium salt; heating of the latter with the excess of Me 2 SO 4 afforded doubly charged bis-methoxysulfonate. Starting from 4-methoxytetrahydropyridinium salts, meso -methoxythiapentacarbocyanine dyes were synthesized.