Tunable Dimerization and Trimerization of β-Alkynyl Ketones via Silver Catalysis for Accessing Spiro and Dispiro Compounds Containing 1H-Isochromene

New silver-catalyzed tunable dimerization and trimerization reactions of β-alkynyl ketones have been established, enabling multiple C−C bond-forming events to selectively access skeletally diverse spiroisochromenes with generally good yields. The silver-enabled bicycloaddition of β-alkynyl ketones with water offered hydroxylated spiroisochromenes. Without water, spiroisochromenes with a methylene moiety were obtained through catalytic 6-endo-dig oxo-cyclization/[4+2] cycloaddition cascades by using pyridine as additive whereas employment of 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate (BiNPO₄H) as a Brønsted acid catalyst rendered the unprecedented dispiro trimerization products through double C(sp³)–H functionalization. (Figure presented.).