A highly efficient potassium carbonate-mediated [3 + 2] cycloaddition reaction of hydrazonoyl chlorides with cinnamic aldehydes to furnish multi-substituted pyrazoles under nontoxic and mild conditions has been developed.
The discovery and synthesis of natural products, especially those possessing novel scaffolds, are crucial to the development of new drugs. Dracaenones are part of homoisoflavone natural products, owning a complex spiro-bridged polycyclic structures bearing benzylic quaternary carbon centers, and some of them reveal considerable biological activity. There have been continuous studies on these compounds due to the rare structure and the important biological properties. However, a systematic summary and analysis for dracaenone is lacking. This review aims to generally summarize the natural source, synthetic strategies and biological activities of dracaenones, moreover, the limitations, challenges, and future prospects were discussed, wishing to provide references for the follow-up study of compounds with similar skeleton.
A novel one-pot two-step process for the preparation of 1,3,4-triarylpyrazoles was disclosed. This process involved a sequential 1,3-dipole cycloaddition reaction of in situ generated nitrile imines with alkenyl isoxazoles and SnCl2-promoted aromatization/elimination reaction, offering a collection of 1,3,4-triarylpyrazoles in a fully regioselective manner. This protocol featured mild reaction conditions, easily available raw materials and excellent regioselectivity.
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