Lewis Acid-Catalyzed Benzannulation of Vinyloxiranes with 3-Formylchromones or 1,4-Quinones for Diversely Functionalized 2-Hydroxybenzophenones, 1,4-Naphthoquinones, and Anthraquinones.

A facile and convenient protocol for the regioselective construction of functionalized 2-hydroxybenzophenones is described. This protocol involves the Sc(OTf)/BF·OEt-catalyzed benzannulation of 2-vinyloxirans with 3-formylchromone, which involves cascade in situ diene formation, [4 + 2] cycloaddition, elimination, and ring-opening strategies. Moreover, it provides an expedited synthetic pathway to access biologically intriguing 1,4-naphthoquinones and anthraquinones including vitamin K3 and tectoquinone.

Sc(OTf)/BF·OEt-Catalyzed Annulation of 3-Formylchromones with Functionalized Alkenes: Access to Diverse 2-Hydroxybenzophenones.

The Sc(OTf)/BF·OEt-catalyzed annulation of 3-formylchromones with functionalized alkenes for the direct construction of 2-hydroxybenzophenones is described. Sc(OTf)/BF·OEt acts as a synergistic catalyst, providing rapid synthetic access to diversely and highly functionalized 2-hydroxybenzophenones. This reaction has excellent regio- and chemoselectivities and is suitable for late-stage functionalization.

Cyrene™ as a Neoteric Bio-Based Solvent for Catalyst-Free Microwave-Assisted Construction of Diverse Bipyridine Analogues for Heavy-Metal Sensing.

An environment-friendly synthetic protocol was developed to access polyfunctionalized bipyridines from readily available amines, chromone-3-carboxaldehydes, and pyridinylacetonitriles under catalyst- and additive-free conditions using the bio-renewable neoteric solvent dihydrolevoglucosenone (Cyrene™). In this strategy, amines served as both a mild-base promoter and a substrate. In addition, water was the only by-product of this reaction.

Base-Mediated Denitrogenative Sulfonylation/Benzannulation of Conjugated -Sulfonylhydrazones with 3-Formylchromones for the Construction of Polyfunctionalized Biaryl Sulfones.

Base-promoted benzannulation of conjugated -sulfonylhydrazones and 3-formylchromones for the synthesis of diverse biaryl sulfones is described. The approach facilitates new C-C and C-S bond formation via the cascade diazo formation/Michael addition/ring opening/denitrogenative sulfonylation/intramolecular cycloaddition/dehydration and introduces diverse functional groups onto biaryl sulfones. The synthesized compounds are converted to aryl sulfones bearing bioactive benzisoxazole and benzofuran frameworks.