FeCl3 catalyzed synthesis of fluorene-C-9-linked furan hybrids from biphenyl-linked conjugated ene-yne-ketones.

In this study, we present a novel and efficient synthetic strategy for the construction of fluorene-C-9-tethered furan hybrids in excellent yields, starting from biphenyl-linked conjugated ene-yne-ketones. The reaction proceeds under mild conditions using iron(III) chloride (FeCl3) as a catalyst. The use of FeCl3 is particularly noteworthy due to its abundance, low cost, non-toxic nature, and environmental compatibility, aligning well with the principles of green chemistry. This methodology offers several important advantages, including high atom economy, operational simplicity, and tolerance towards a wide range of functional groups. The protocol provides a sustainable alternative to the use of precious metals or harsh reagents. Mechanistically, the transformation is proposed to proceed via the in situ generation of a (2-furanyl)iron-carbene intermediate, which facilitates an intramolecular cyclization to afford the desired fluorene-furan hybrid products. This transformation highlights the synthetic utility of FeCl3 in enabling carbene-mediated hetero-cyclization and demonstrates its potential in designing metal-catalyzed processes for the rapid construction of structurally diverse heteroaromatic frameworks relevant to medicinal chemistry and materials science.