Copper-Catalyzed Cascade Annulation of o-Hydroxyphenyl Propargylamines with Pyrazolin-5-ones to Access Pyrano[2,3-c]pyrazoles.

An efficient copper-catalyzed cascade annulation of o-hydroxyphenyl propargylamines and pyrazolin-5-ones is described. This methodology leads to the rapid assembly of a series of valuable pyrano[2,3-c]pyrazoles with good yields across a wide range of substrates in a simple fashion. This novel reaction involves the formation of alkynyl ortho-quinone methides, a 1,4-conjugate addition, and a subsequent 6-endo cyclization process. The mechanistic elucidation is well supported by control experiment and literature precedents.

Regio- and Diastereoselective Spirocyclopropanation of Benzofuran-Derived Azadienes through 1,4-Addition-Induced Dearomatization Reaction under Mild Conditions.

A Cs2CO3-mediated [2 + 1] cycloaddition of benzofuran-derived azadienes (BDAs) with bromomalonate by using a dearomatization strategy has been developed. Through this process, BDAs serve as a potential 2-atom synthon in the construction of a range of functionalized spirocyclopropane derivatives, such as spirobenzofuran-2-cyclopropanes and spiroindane-2-cyclopropanes.