Transition-metal-free, mild and efficient ring expansion of amino acid derivatives: facile access to densely functionalized azepines

Abstract

Azepines are important structural motifs in drug discovery possessing valuable biological and medicinal properties. However, the approaches for the preparation of these versatile skeletons are limited and still challenging. Herein,...

Photochemical Skeletal Editing of Pyridines to Bicyclic Pyrazolines and Pyrazoles

“…Pyridine skeletal editing transformations can be categorized into two strategies: ring expansion and ring contraction (Figure D). Typically, the nucleophilicity of the nitrogen atom of pyridines is harnessed to prepare cationic pyridinium salts. − Pyridine expansion via N-functionalized pyridinium salt (imidopyridine ylide) has been widely employed in synthetic methodologies. − Additionally, ring contractions via carbon deletion under light or electricity have been documented, yielding pyrroles or pyrazolines as exclusive products. − …”

Nickel-Catalyzed Deaminative Alkyl–Alkyl Cross-Coupling of Katritzky Salts with Cyclopropanols: Merging C–N and C–C Bond Activation

“…With our continuing interest in nickel-catalyzed cross-coupling reactions, and the conversions of Katritzky type pyridinium salts, ,, we envisioned if cyclopropanolsan important class of ketone homoenolate precursors in organic synthesiscould be employed as reactive partners to fulfill the desired transformation via C–C bond cleavage. However, despite their widespread use in the preparation of β-functionalized carbonyl compounds, the application of unmasked cyclopropanols in nickel catalysis, especially in coupling with unactivated alkyl electrophiles, remains scarce and challenging .…”