An alternative green method was developed for the synthesis of thio-and selenoflavones by the ring closure of 2-chlorophenyl ethynyl ketone with NaHY (Y = S, Se). These nucleophilic chalcogen species were generated in situ using NaBH4 to reduce the elemental chalcogen in the presence of polyethylene glycol-400 (PEG-400). The efficiency of this reaction is strongly dependent on the PEG-400 solvent, acting like a crown ether, complexing with the sodium atom of NaHY species, making the chalcogen nucleophile more active. The synthetic protocol proceeded efficiently at 100 °C under argon, using a range of 2-chlorophenyl ethynyl ketone containing alkyl, aryl, or vinyl groups and the sulfur and selenium chalcogen. By this efficient and simple approach, 18 chalcogenoflavones were obtained in good to excellent yields after 2 h.

In this work, enantiopure 1,1’-bi-2-naphthol (BINOL) derivatives and carboxylic acids were evaluated as chiral solvating agents (CSAs) in the nuclear magnetic resonance (NMR) chiral discrimination of primary amines. Among the CSAs screened, the readily available (+)-BINOL revealed a simple and rapid chiral auxiliary for 1H NMR chiral discrimination. The procedure required few minutes, assigning of the absolute configuration. The protocol was improved using the 1H pure shift pulse sequence for overcrowded alkyl primary amines due to the absence of JHH couplings. The 1H pure shift NMR experiment and the readily available (+)-BINOL chiral auxiliary can be used for routine chiral discrimination analysis of complex NMR spectra.

Um método simples e eficiente foi desenvolvido para a hidrocalcogenação de alquinos contendo um aceptor de Michael (éster, cetona e nitrila) com ânions fenilcalcogenolatos gerados in situ a partir do respectivo dicalcogeneto de difenila (Se, Te, S), usando hidreto de boro e sódio suportado em alumina e meio livre de solvente. Este método é geral e permite a obtenção de ésteres, cetonas e nitrilas (Z)-beta-fenilcalcogeno-<FONT FACE=Symbol>a,b</FONT>-insaturados, com rendimentos e seletividade comparados aos obtidos quando se utiliza solvente orgânico e atmosfera inerte. O uso de irradiação de microondas facilitou o procedimento e acelerou a reação.

A simple, clean and efficient solvent-free protocol was developed for hydrochalcogenation of alkynes containing a Michael acceptor (ester, ketone and nitrile) with phenylchalcogenolate anions generated in situ from the respective diphenyl dichalcogenide (Se, Te, S), using alumina supported sodium borohydride. This efficient and improved method is general and furnishes the respective (Z)-beta-phenylchalcogeno-<FONT FACE=Symbol>a,b</FONT>-unsaturated esters, ketones and nitriles, in good yield and higher selectivity, compared with those that use organic solvent and inert atmosphere. The use of microwave (MW) irradiation facilitates the procedure and accelerates the reaction.