Photochemical irradiation of 2,3-dihydro-2-tert-butyl-3-benzyl-4(1H)-quinazolinone produced 3-benzyl-4(3H)-quinazolinone through photoinduced elimination via a radical mechanism. The use of photochemical conditions such as chloroform and UV irradiation (λ = 254 nm) got the 3-benzyl-4(3H)-quinazolinone in a high yield. Some theoretical calculations were achieved to explain the mechanism and the presence of radical intermediates was confirmed by trapping with different 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derivatives.4-Quinazolinone derivatives are important building blocks of active molecules isolated from different natural sources. 1 Their principal derivatives are 2,3-dihydro-4(1H)-quinazolinones and 4(3H)-quinazolinones. These compounds possess a wide range of useful biological activities and interesting pharmacological properties, 2 and their syntheses have been well described in the literature. 3 The use of photochemical irradiation in these compounds, however, has been less common, and only a few have been reported such as preparation of fused quinazolin-4-one derivatives, for example, luotonin A and related fused compounds through radical intermediates, 4 photodecomposition of 8-chloro-6-(2-fluorophenyl)-1-methyl-4H-imidazo[1,5-a][1,4]benzodiazepine (Midazolam) to get a 4(3H)-quinazolinone derivative, 5 and irradiation of 4-phenylquinazolin-2-ones in the presence of a hydrogen donor in order to get the reduced 3,4-dihydroquinazolin-2-ones 6 as well as the photoaddition of 4(3H)-quinazolinone derivatives to olefins. 7 In this study we analyzed the behavior of 2,3-dihydro-2-tert-butyl-3-benzyl-4(1H)-quinazolinone under UV irradiation, and theoretical calculations were developed to propose a mechanism, and trapping of the radical intermediate was achieved using TEMPO derivatives. Knowledge of these reactions could help to develop photochemically controlled reactions of other 2,3-dihydro-4(1H)-quinazolinone derivatives.Our research was focused on the preparation of starting materials following the methodology previously reported by our group 8 in which a reaction between isatoic anhydride and benzylamine in ethyl acetate at 40°C results in the corresponding aminobenzamide 1 in 90% yield. Next, the cyclocondensation of 1 with pivalaldehyde in dichloromethane and p-toluenesulfonic acid monohydrate gives 2 in 86% yield (Scheme 1).Preliminary studies rapidly led to the conclusion that it was necessary to protect the reaction from light source since this would suffer photoinduced elimination and hence reduces the yield of compound 2. The absorption spectrum of 2 ( Figure 1) presents two absorption bands at λ = 242 and 341 nm, attributed to π-π* and n-π* transitions, respectively. The fluorescence spectrum is shown in the Figure 2 and presents a maximum emission at λ = 404 nm. The quantum yield of fluorescence was measured at 25°C using quinine sulfate (H 2 SO 4 0.5 M, Φ = 0.55) as standard and employing existing equations for calculating quantum fluorescence yield;
A simple one-pot procedure for the preparation of imines from the corresponding aldehydes and amines, and their subsequent oxidation reaction with m-CPBA to produce synthetically useful oxaziridines is reported. The method is applicable to imines derived from both aliphatic and aromatic aldehydes and diverse alkyl amines. Short reaction times, essentially quantitative yields, very mild reaction conditions, and easy purification are the main features of the procedure reported herein.
It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pure manner and with a high yield in a very short reaction time: 3 -10 min. In general terms, the condition under which this reaction is carried out accelerates the decarboxylation significantly of a series of disubstituted malonic acid derivatives, and makes this new process efficient, easy and environmentally friendly.
3-Benzyl-2-(tert-butyl)-2,3-dihydroquinazolin-4(1H)-one rac-11 was resolved via the preparation of diastereomers with N-phthalyl-L-alanine chloride and its absolute configuration was determined by X-ray crystallographic analysis. This heterocycle has potential as a substrate chiral in asymmetric induction due to the steric effects of its tert-butyl group.
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