PMHS-involved Bismuth Or Palladium-catalyzed Transfor-Mations Of Chalcones

Bismuth salt is non-toxic and environmentally friendly, that is the reason why it is widely used in organic synthesis. However, research focused on the catalyzed role of Bismuth salt in organic synthesis is still challenging. This paper focused on bismuth-catalyzed organic synthesis. At the very beginning, we mostly focused on bismuth-catalyzed conjugate Reduction of chalcone. Then, we focused on palladium-catalyzed dicyano-transfer reactions. Although, bismuth triflate on fluorination of β-ketoester in the presence of chiral primary amine (QN-NH2) is not very good. We then investigated the catalyzed effect of chiral primary amine (QN-NH2) in fluorination reaction.We have shown firstly that the combined Bismuth triflate-malononitrile system can serve as an efficient reductant/reagent in1,4-conjugate reduction of enones. As a α.β-unsaturated ketones, chalcone can be reduced to produce several products, to our surprise, only2a was obtained in promising yields through1,4-conjugate reduction. The unexpected results led us to investigate this catalyste system in detail. And next investigation showed that4-phenylbut-3-en-2-one was not suitable substrate in the conjugate reduction metioned before, thus we continue to modify the bismuth-based catalyst system to improve the catalytic activity or change the possible mechanistic procedure. Under the optimized reation conditions, commercial available and cheap NH4Cl was found to be effective for the conjugate reduction in the presence of malononitrile turated Ketones.In addition, we found that PdCl2, PMHS can catalyze the conversion of4a to2-((E)-1,3-Diarylallylidene)malononitriles in promising yield. The effect of solvent. temperature, time and the quantity of PMHS on the reaction was investigated in this work. The investigation showed that PdCl2,(5mol%) and PMHS (2.5eq.) can serve as an efficient catalyste system in MeOH.In the last, we have found that the chiral primary amine, bismuth triflatea and malononitrile system cannot serve as an efficient reagent in enantioselective fluorination reaction of β-ketoester. We used L-leucine and QN-NH2as dual primary amine catalysts for enantioselective fluorination of β-ketoester, which led to the determination of a novel dual organocatalyst with promising catalytic activity. Furthermore, the dual organocatalysts with organosilicon compounds as additive promoted the fluorination of β-ketoester to give99%yield and promising enantioselectivity(47%ee). On a detailed experimental investigation, we have demonstrated a possible mechanism of this reaction that enantioselectivity in the fluorination of β-ketoester stems from the steric environment of the chiral enamine species.