DABCO-catalyzed [4 + 2] and Bu(3)P-catalyzed [3 + 2] cycloadditions between 3-acyl-2H-chromen-ones and ethyl 2,3-butadienoate were developed for the synthesis of dihydropyran-fused and cyclopenten-fused chromen-2-ones with high regio- and stereo-selectivities, respectively. The synthetic procedures have the advantages of mild reaction conditions, convenient handling and good atom economy as well as a wide substrate scope, which make this method useful for the synthesis of potentially biologically active dihydropyran-fused and cyclopenten-fused chromen-2-ones derivatives. Possible reaction mechanisms have also been proposed on the basis of previous literature and our investigation.

A series of pyrimidinyl benzylamine analogues containing a phosphonyl group (2)

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An unexpected FeCl3-mediated three-component cascade reaction has been used to construct structurally diverse pyrrolo[1,2-c]quinazolinone derivatives with potential biological activities. This method has advantages of mild conditions, simple work-up, as well as wide substrate scope, which makes it a powerful approach to the synthesis of diverse pyrrolo[1,2-c]quinazolinones. This cascade reaction involves 1,3-dipolar cycloaddition between azomethine ylides and allenoates, followed by intramolecular nucleophilic addition in the presence of FeCl3. The obtained products could be easily transformed into derivatives with the pyrrolo[2,3-c]quinazoline alkaloid skeleton.

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