Annulation of 4-Hydroxypyrones and α-Keto Vinyl Azides; A Regiospecific Approach towards the Synthesis of Furo[3, 2-c]Pyrone Scaffolds under Catalyst Free Condition

Base-mediated 1,3-dipolar cycloaddition of pyridinium bromides with bromoallyl sulfones: a facile access to indolizine scaffolds

An expedient and transition-metal-free synthetic strategy has been developed for the construction of substituted indolizines from a unique combination of pyridinium salts and 2-bromoallyl sulfones. This approach does not compromise with the diverse substitutions on both the pyridinium salts and 2-bromoallyl sulfones. Wide substrate scope, operational simplicity, milder reaction conditions and good to moderate yields are the merits associated with the current approach. Moreover, this method provides two products which are amenable for the generation of a library of key indolizine building blocks.

Access to 2,3-Fused Pyrroles via Visible Light Driven Coupling of α-Azidochalcones with 1/2-Naphthols, or 2-Hydroxy-1,4-Naphthoquinone

α-Azidochalcones were coupled with 1/2-naphthols or 2-hydroxy-1,4-naphthoquinone using Ru(bpy)₃(PF₆)₂ as a photocatalyst under blue LED light irradiation to yield 2,3-fused pyrroles in high yields (68-84%). The overall transformation involves photosensitized decomposition of α-azidochalcones into highly reactive 2 H-azirines which are trapped by 1/2-naphthols or 2-hydroxy-1,4-naphthoquinone, leading to the construction of two new C-N and one new C-C bonds.