Under the conditions of ruthenium(0)-catalyzed hydrohydroxyalkylation, vicinal diols 1a-1l and methyl acrylate 2a are converted to the corresponding lactones 3a-3l in good to excellent yield. The reactions of methyl acrylate 2a with hydrobenzoin if, benzoin didehydro-1f, and benzil tetradehydro-1f form the same lactone 3f product, demonstrating that this process may be deployed in a redox level-independent manner. A variety of substituted acrylic esters 2a-2h participate in spirolactone formation, as illustrated in the conversion of N-benzyl-3-hydroxyoxindole lo to cycloadducts 4a-4h. Hydrohydrox-yalkylation of hydroxyl-substituted methacrylate 2i with diols 1b, if, 1j, and 11 forms a-exo-methylene-y-butyrolactones 5b, 5f, 5j, and 51 in moderate to good yield. A catalytic cycle involving 1,2-dicarbonyl acrylate oxidative coupling to form oxaruthenacyclic intermediates is postulated. A catalytically competent mononuclear ruthenium(II) complex was characterized by single-crystal Xray diffraction. The influence of electronic effects on regioselectivity in reactions of nonsymmetric diols was probed using para-substituted 1-phenyl-1,2-propanediols 1g, 1m, and 1n and density functional theory calculations.