Paraformaldehyde and methanol as C1 †feedstocks in metal-catalyzed C-C couplings of π-unsaturated reactants: beyond hydroformylation.

Ruthenium-catalyzed reductive couplings of paraformaldehyde with dienes, alkynes, and allenes provide access to products of hydrohydroxymethylation that cannot be formed selectively under the conditions of hydroformylation. In certain cases, the regioselectivity of the CC coupling can be inverted by using nickel catalysts. With iridium catalysts, methanol engages in redox-neutral regioselective hydrohydroxymethylations.

Hydroaminomethylation Beyond Carbonylation: Allene-Imine Reductive Coupling by Ruthenium-Catalyzed Transfer Hydrogenation.

Ruthenium(II)-catalyzed hydrogen transfer from 2-propanol mediates reductive coupling of 1,1-disubstituted allenes with formaldimines with complete branch-regioselectivity, thus representing a new method for hydroaminomethylation beyond classical hydroformylation/reductive amination.

Ruthenium-catalyzed C-C coupling of fluorinated alcohols with allenes: dehydrogenation at the energetic limit of ß-hydride elimination.

Ruthenium(II) complexes catalyze the CC coupling of 1,1-disubstituted allenes and fluorinated alcohols to form homoallylic alcohols bearing all-carbon quaternary centers with good to complete levels of diastereoselectivity. Whereas fluorinated alcohols are relatively abundant and tractable, the corresponding aldehydes are often not commercially available because of their instability.

Alkyne-aldehyde reductive C-C coupling through ruthenium-catalyzed transfer hydrogenation: direct regio- and stereoselective carbonyl vinylation to form trisubstituted allylic alcohols in the absence of premetallated reagents.

Nonsymmetric 1,2-disubstituted alkynes engage in reductive coupling to a variety of aldehydes under the conditions of ruthenium-catalyzed transfer hydrogenation by employing formic acid as the terminal reductant and delivering the products of carbonyl vinylation with good to excellent levels of regioselectivity and with complete control of olefin stereochemistry. As revealed in an assessment of the ruthenium counterion, iodide plays an essential role in directing the regioselectivity of C-C bond formation. Isotopic labeling studies corroborate reversible catalytic propargyl C-H oxidative addition in advance of the C-C coupling, and demonstrate that the C-C coupling products do not experience reversible dehydrogenation by way of enone intermediates. This transfer hydrogenation protocol enables carbonyl vinylation in the absence of stoichiometric metallic reagents.

Ruthenium catalyzed reductive coupling of paraformaldehyde to trifluoromethyl allenes: CF3-bearing all-carbon quaternary centers.

Trifluoromethyl substituted allenes engage in ruthenium catalyzed reductive couplings with paraformaldehyde to form products of hydrohydroxymethylation as single regioisomers. This method enables generation of CF3-bearing all-carbon quaternary stereocenters.