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Two tunable cascade reactions of alkynols and alkynes have been developed by combining Sc(OTf)3 and rhodium catalysis. In the absence of H2O, an endo-cycloisomerization/C–H activation cascade reaction provided 2,3-dihydronaphtho[1,2-b]furans in good to high yields. In the presence of H2O, the product of alkynol hydration underwent an addition/C–H activation cascade reaction with an alkyne, which led to the formation of 4,5-dihydro-3H-spiro[furan-2,1′-isochromene] derivatives in good yields under mild reaction conditions. Mechanistic studies of the cascade reactions indicated that the rate-determining step involves C–H bond cleavage and that the hydration of the alkynol plays a key role in switching between the two reaction pathways. [ABSTRACT FROM AUTHOR]

A tetradentate nitrogen-phosphorus ligand is used for the ruthenium-catalyzed title reaction with high exo-selectivity. [ABSTRACT FROM AUTHOR]

Three new bonds are generated in one step by the combination of an alkyne-based 5-exo-dig cyclization with a Pd(II) carbene migratory insertion and an intramolecular cyclization. [ABSTRACT FROM AUTHOR]