Three molecular switches containing a fluorene ring were designed and synthesized. The introduction of the amino group substituted fluorene ring resulted in the target molecular switches having some optical properties in the near-infrared region. It was demonstrated that the N-substituents on the fluorene rings and the switch units both had great influence on the molecular switch optical properties including the absorption maximum, absorption intensity and fluorescence quantum yield. The open-ring forms and showed obvious solvatochromic behaviour. The closed-ring forms and showed obvious hydrochromic behaviour in MeCN/water binary solvent systems and acidichromic behaviour in MeCN solution with high reversibility. Especially, the distinct off-on fluorescence signal in the near-infrared region using the stimuli of acid means that the designed compounds have great potential application value in the field of biological sensing.
A catalytic enantioselective synthetic strategy for the aryl-substituted all-carbon quaternary stereocenters of bioactive hydrodibenzofuran alkaloids was achieved by the Michael addition reaction of α-cyano ketones and acrylates using a chiral tertiary amine-thiourea catalyst. This method can tolerate steric bulkiness and multiple functional groups, and 32 Michael adducts were prepared in good to excellent yields with
Based on the two aggregation-state changes of the THF system of 2, a new dual guaranteed strategy for the real-time naked-eye detection of fluoride-ions was developed.
Michael addition of α‐cyanoketones and acrylates in the presence of chiral cinchonidine catalyst (CJN) produces the corresponding Michael adducts in high yields with moderate to good enantioselectivities.
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