Lanthanide-catalyzed deamidative cyclization of secondary amides and ynones through tandem C-H and C-N activation

Versatile C─H Alkylation and Alkylidenation via Catalytic Alkylidene Transfer of Enones

The alkylidene transfer reactions of alkenes are of particular significance but challenging. Here, we report that enones can serve as diverse alkylidene sources for catalyst-controlled selective C─H alkylation and/or alkylidenation of various nucleophiles. Treatment of a mixture of ketone (or lactam), enone, and diarylmethanol, with a catalytic amount of Y[N(TMS)2]3, gave the corresponding α-C─H bond alkylation products derived from the alkylidene transfer from enones to ketones/lactams, whereas the reaction of enones with various C-nucleophiles in the presence of KOH as a catalyst resulted in C─H alkylidenation. Moreover, the application of these strategies for the late-stage modification or structural simplification of some bioactive molecules is also presented. These alkylidene transfer reactions are characterized by operational simplicity, mild reaction conditions, and remarkable catalyst-controlled product outcomes. These results not only demonstrate a significant potential for easily accessible and recyclable enones to serve as versatile alkylidene sources in C─H alkylation and alkylidenation but also provide an attractive and concise method for hydrodealkylidenation of electron-deficient alkenes.

Synthesis of Pyridin-2(1H)-imines via the Transformation of Conjugated Ynones

Conjugated ynones represent an important class of reactive species, useful synthetic intermediates, and synthons. However, the reactivity and synthetic applications of ynones are usually focused on the transformation of mono- or dual-functional groups. Herein, we developed a straightforward synthesis of pyridin-2(1H)-imines from the transformation of conjugated ynones. This cascade process probably began with a Michael addition of ynones and 2-aminopyridines, further underwent an intramolecular cyclization to generate the N,O-bidentate intermediates, and finally reacted with sulfonyl azides giving the pyridin-2(1H)-imines with accompanying loss of diazo.

Base- and sulfur-promoted oxidative lactonization of chalcone-acetate Michael adducts: access to pyran-2-ones

A cost-effective, practical, straightforward and scalable synthesis of α-pyrones via base- and sulfur-promoted annulation of phenylacetates and chalcones is reported. Generated in situ from the starting components by using dbu as a base catalyst, the Michael adducts underwent a smooth oxidative cyclization into 3,4,6-triaryl-2-pyranones upon heating with DABCO and sulfur in DMSO. Extension to malonate in place of phenylacetates led to 4,6-diaryl-2-pyranone-2-carboxylates.