Preparation, reactivity and tautomeric preferences of novel (1H-quinolin-2-ylidene)propan-2-ones

Abstract

1,1-Difluoro-3-(1H-quinolin-2-ylidene)propan-2-one 1a, 1,1,1-trifluoro-3-(1H-quinolin-2-ylidene)propan-2-one 1b, 1,1,1-trifluoro-3-(4-chloro-1H-quinolin-2-ylidene)propan-2-one 1c and 1,3-dibromo-1,1-difluoro-3-(2-quinolyl)propan-2-one 2 are prepared and characterized by various spectroscopic techniques. The crystal structure of 1a is determined by X-ray diffraction. Furthermore, a series of previously known non-halogenated (1H-quinolin-2-ylidene)propan-2-ones 1d-1h are oxidized with AgBrO 3 in the presence of AlCl 3 . In all cases, 2-(1-bromo-1-chloromethyl)quinoline 3 is obtained in high yield. The bromination order and sites of 1a are analyzed based on ab initio MP2 and DFT calculations for the molecule and its anions.

CO2 production in the bromate‐1,4‐cyclohexanedione oscillatory reaction

“…Baeyer-Villiger type oxidation of bromobenzoquinone is capable of forming lactone 3, which would be susceptible in aqueous acid to hydrolysis to form carboxylic acid-containing keto-aldehyde 4. It may also be possible that this overall transformation of benzoquinone to 4 is accomplished via a Lieben haloform reaction, as they are known to be initiated by both silver bromate and NaOBr; [23,24] we consider this less likely due to the strongly acidic conditions in the current case. Following aldehyde oxidation of 4 to the b-keto acid function ((Z)-5), acid induced hemi-acetal formation (6), and dehydration would give (7), which has been proposed previously by our group to undergo a Hunsdiecker-type decarboxylative bromination [25][26][27][28] The most plausible mechanism for dibromoacetic acid formation also initiates with Baeyer-Villiger oxidations, but of 2,5-dibromobenzoquinone, and on both ketone carbonyls, affording eight-membered ring compound 9.…”