Hydrogenation of 1,3-enynes 1a-e in the presence of heterocyclic aromatic aldehydes and ketones using chirally modified cationic rhodium precatalysts results in reductive coupling to afford dienylated alpha-hydroxy heteroarenes 2-23 with exceptional levels of regio- and enantiocontrol. Coupling of enyne 1a to 2-pyridinecarboxaldehyde using an achiral rhodium catalyst in the presence of a chiral Akiyama-Terada-type phosphoric acid derived from BINOL as the Brønsted acid co-catalyst provides the coupling product 2 with substantial levels of optical enrichment (82% ee). This result suggests that substrate protonation and/or formation of a strong hydrogen bond occurs in advance of the stereogenic C-C bond forming event. Further, the high levels of asymmetric induction demonstrate that interaction of the aldehyde with the Brønsted acid activates the system toward C-C coupling. Reductive coupling of enyne 1a and 2-pyridinecarboxaldehyde under an atmosphere of elemental deuterium provides the monodeuterated product deuterio-2, consistent with a catalytic mechanism involving alkyne-carbonyl oxidative coupling followed by hydrogenolytic cleavage of the resulting oxametallacycle. The diene side chain of the coupling products is subject to diverse selective transformations, as demonstrated by the conversion of coupling products 2 and 8 to compounds 24-26 and 27-29, respectively.

Hydrogenation of alkynes in the presence of carbonyl compounds and imines using cationic rhodium(I) and iridium(I) precatalysts enables the formation of allylic alcohols and allylic amines, respectively. Through the use of hydrogenation catalysts modified by chiral ligands, allylic alcohols and allylic amines may be generated in highly optically enriched forms. Hydrogenative fragment couplings of this type circumvent the use of preformed organometallic reagents and avoid the generation of stoichiometric byproducts.

Hydrogenation of 2-vinyl azines 1a-1e in the presence of N-arylsulfonyl imines 2a-2l at ambient temperature and pressure employing cationic rhodium catalysts ligated by tri-2-furylphosphine results in regioselective reductive coupling to furnish branched products of imine addition 3a-3v, which embody modest to high levels of syn-diastereoselectivity. Catalytic coupling of 6-bromo-2-vinylpyridine 1a to imine 2l under an atmosphere of elemental deuterium provides deuterio-3l, with deuterium exclusively at the former beta-position of the vinyl moiety. These data are consistent with a catalytic mechanism involving oxidative coupling of the vinyl azine and imine partners to furnish a cationic aza-rhodacyclopentane, which upon deuteriolytic cleavage releases the adduct and regenerates cationic rhodium(I) to close the catalytic cycle. These studies represent the first metal catalyzed reductive C-C couplings of vinyl azines.

The cationic ruthenium catalyst generated upon the acid-base reaction of H2Ru(CO)(PPh3)3 and 2,4,6-(2-Pr)3PhSO3H promotes the redox-triggered C-C coupling of 2-alkynes and primary alcohols to form (Z)-homoallylic alcohols with good to complete control of olefin geometry. Deuterium labeling studies, which reveal roughly equal isotopic compositions at the allylic and distal vinylic positions, along with other data, corroborate a catalytic mechanism involving ruthenium(0)-mediated allene-aldehyde oxidative coupling to form a transient oxaruthenacycle; an event that ultimately defines (Z)-olefin stereochemistry.

Ring expansion metathesis polymerisation (REMP) has proven to be a viable approach to prepare high purity macrocyclic phenylenevinylene polymers.