Hydration Of Alkynes Catalyzed By BF₃·Et₂O And Synthesis Of Flavanone Derivatives And Their Activity Evaluation

Firstly, nine ketones were synthesized from alkynes with BF3·Et2O as the catalyst,which were characterized by NMR spectroscopy. The optimal routine is derived fromthe research of the quantity of solvent and catalyst. The results exhibit that thehydrations of alkynes can run easily when methylene chloride is employed as solventand1eqv. of BF3·Et2O as the catalyst. Water is not necessary in the reaction systembecause the little water in solvent and atmosphere is enough. The hydrations ofalkynes will possess higher activities when the C≡C bonds are connecting witharomatic rings. The reaction mechanism is not clear, but we suppose the mechanismof this reaction may be the following. As the hybride obitals of B atom in BF3·Et2O issp2, the rest p-obital can accept the electrons from the C≡C bond. Meanwhile, thewater molecule attacks the carbon atom nearby the aromatic ring, leading the electrontransfer to yield the enolic-structure, and the ketone-structure generates followed. Theadvantages of this method are mild condition, simple route and no-metals, etc., whilethe yield still need to be improved.Secondly, the addition or substitution reactions between the unsaturated bondsand the cayno compounds with Pbf-CN or Ts-CN as cyano reagent and styrene orphenylacetylene as substrates were investigated, in order to construct C-CN bonds.No satisfying results were obtained with CuBr, Ag2O, PdCl2and NC-ligand as thecatalysts.Thirdly, We synthesized two flavanones bearing iso-pentenyl side chain andevaluated their anti-Staphylococcus aureus(S. aureus) activity. The target compounds7a[2-5’-(1",2"-dimethylallyl)-2’-methoxy-4’,5,7-tetrahydroxyflavanone] and7b[2-5’-(1",2"-dimethylallyl)-3’-methoxy-4’,5,7-tetrahydroxyflavanone] weresynthesized respectively through total four steps starting from2,4,6-trihydroxyacetophenone and the corresponding iso-pentenyl substituted benzaldehyde, in whichthe1,2-dimethyl-2-propenyl group had been introduced previously via abnormalClaisen rearrangement. The bioactivities of the two flavanones against S. aureus strains ATCC25923,29213, and MRSA252were evaluated, showing the sameminimum inhibitory concentration(MIC) value of16μg/mL.