Phosphine-Mediated Divergent Cascade Cycloaddition of Cyclic Diketones and Terminal Alkynes: Access to Diverse Pyran-Fused Polycycles.

A facile phosphine-mediated divergent cascade cycloaddition was developed to construct diverse pyran-fused polycycles from cyclic diketones and electron-deficient terminal alkynes. This reaction exhibits alkyne-tuned divergent reactivity and broad functional group compatibility, applicable to both common 2-arylidene-1,3-indanediones and rarely reported alkylidene dibenzo-β-tropolones. A plausible dual-pathway mechanism was proposed to elucidate the divergent reaction process.