(Z)-4-[(aril/alquil)amino]-1,1,1-tricloro-4-fenilbut-3-en-2-onas e 2H-1,3,2-oxazaborininos derivados: síntese, caracterização e propriedades fotofísicas

Abstract

The present work aims to evaluate the synthetic possibility of new substituted trichloromethyl β-enaminoketones as synthetic intermediates. Initially the synthesis of the (Z)-1,1,1-trichloro-4-methoxy-4-phenylbut-3-en-2-one (1) was carried out by the acylation reaction of a mixture of the acetal derivative of acetophenone with trichloroacetyl chloride, from a methodology already described in the literature. The synthesis of β-enaminoketones of interest, by addition/elimination reactions were performed between (Z)-1,1,1-trichloro-4-methoxy-4-phenylbut-3-en- 2-one (1) and different alkyl and aryl amines (RNH2, 2a-i), R = i-Pr, n-Bu, C6H5, 4-CH3-C6H4, 4-OCH3-C6H4, 4-Br-C6H4 , 4-F-C6H4, 4-NO2-C6H4, 2-Naphthyl, by methodologies adapted from the literature which resulted in the isolation of an unpublished series of nine examples of (Z)-1,1,1-trichloro-4-[(aryl / alkyl)amino]-4-phenylbut-3-en-2-ones (3a-i) in yields of 61-90%. Subsequently the possibility of obtaining fluoro-organoboron heterocyclic compounds derived from β-enaminoketones 3, a reaction involving β-enaminoketone (Z)-1,1,1-trichloro-4-(p-toluylamino)-4-phenylbut-3-en-2-one (3d) in the presence of BF3.OEt2 and anhydrous Et3N in anhydrous CHCl3 as solvent was performed. Thus, the desired product 2,2-difluoro-4-phenyl-3-(p-toluyl)-6-(trichloromethyl)-2H-1,3,2-oxazaborinin-2-ium-3-uid (4d) was obtained in 70% yield, demonstrating an interesting synthetic applicability for β-enaminoketones 3. Finally, comparative photophysical tests were performed between the precursor β-enaminoketone (3d) and the respective substituted fluoro-organoboron trichloromethyl compound (4d) evaluating luminescence property. As a result, it was possible to observe that the compounds absorb in the ultraviolet region (UV), and in relation to the fluorescence emission, enaminone (3d) does not fluoresce and the fluoro-organoboron heterocyclic compound (4d) fluoresce in an intensity too low, almost in the noise. The compounds obtained were structurally characterized by 1H, 13C {1H}, 19F and 11B NMR techniques, gas chromatography coupled to mass spectrometry (GC-MS) and high resolution mass spectrometry (HRMS).