A Lewis Acid-Promoted Michael Addition and Ring-Expansion Cascade for the Construction of Nitrogen-Containing Medium-Sized Rings

Abstract

A Lewis acid-promoted annulation of azadienes and cyclobutamines was developed. This reaction proceeded through Michael addition and ring-expansion cascade, affording the corresponding nitrogen-containing medium-sized rings with a broad scope in moderate to high yields. The catalytic asymmetric version of this reaction has also been explored using a chiral base.

Molecular-iodine catalyzed selective construction of cyclopenta[b]indoles from indoles and acetone: a green gateway to indole-fused cycles

“…Indole-fused annulated structures form an important class of privileged nitrogen-heterocycles due to their widespread occurrence in natural products and active pharmaceutical ingredients. 1–4 Among them, cyclopentannulated indoles are especially attractive because of their prevalence in numerous alkaloids, presenting impressive pharmacological activities including cytotoxicity, antibacterial and insecticidal properties, and acting as enzyme receptors. 5–7 Their enormous biological significance has prompted researchers to contribute to the design and construction of these natural product-inspired frameworks and drug-like molecules.…”

Streamlined Synthesis of Varied Heteroarene-Condensed Benzofuran Derivatives via [4 + 2] Annulation of Benzofuran-Derived Azadienes and N-Alkyl Quinolinium Salts

“…The relative configuration of 3aa was again determined by single crystal X-ray diffraction and NOESY experiments (see Supporting Information). Drawing from the literature reports, dichloroethane (DCE) appeared to be a more suitable solvent for this transformation. Consequently, using DCE as the solvent resulted in the synthesis of product 3aa with a 61% yield (entry 6).…”