K3PO4‐Promoted Cycloannulation of (E)‐β‐Iodovinyl Sulfones with ortho‐Hydroxy‐Chalcones/Cinnamates for the Synthesis of 2,3,4‐Trisubstituted 4H‐Benzopyran Derivatives.

K3PO4‐mediated cycloannulation of (E)‐β‐iodovinyl sulfones with ortho‐hydroxy chalcones/ortho‐hydroxy cinnamates has been realized to access 2,3,4‐trisubstituted‐4H‐benzopyran derivatives. A metal‐free tandem oxa‐Michael addition and cycloannulation allows the diversity‐oriented synthesis of the corresponding 3‐sulfonyl‐4H‐benzopyrans in good to high yields. More importantly, one‐pot three‐component reaction between (E)‐β‐iodovinyl sulfones, 2‐hydroxybenzaldehydes, and phosphonium ylides has been established for the synthesis of 4H‐chromene derivatives in moderate to good yields. Notably, this metal‐free process features a broad substrate scope and easy elaboration into numerous multifaceted chromene products, including bioactive estrone‐derivative. The present protocol is sustainable at the gram scale reactions, and post‐synthetic applications were also demonstrated. A plausible mechanism is also presented on the basis of existing experimental results. [ABSTRACT FROM AUTHOR]