Utilization of C-C bond activation as a unique mode of reactivity for constructing C-C bonds provides new strategies for preparing important organic molecules. Development of a Rh(I)-catalyzed C-C activation of diynones to synthesize symmetrical and unsymmetrical conjugated diynes through decarbonylation is reported. This C-C cleavage strategy takes advantage of the innate reactivity of conjugated ynones without relying on any ring strain or auxiliary directing group. This alkynation method also has orthogonal properties compared to typical cross-coupling reactions.

In this full article, detailed development of a catalytic decarbonylation of conjugated monoynones to synthesize disubstituted alkynes is described. The reaction scope and limitation has been thoroughly investigated, and a broad range of functional groups including heterocycles were compatible under the catalytic conditions. Mechanistic exploration via DFT calculations has also been executed. Through the computational study, a proposed catalytic mechanism has been carefully evaluated. These efforts are expected to serve as an important exploratory study for developing catalytic alkyne-transfer reactions via carbon−alkyne bond activation.

A Rh-catalyzed controlled decarbonylation of alkynyl α-diones is described. By using different ligand and solvent combinations, mono and double decarbonylation can be selectively achieved to give conjugated ynones and disubstituted alkynes, respectively. A fundamental study on catalytic activation of un-strained C−C bonds under non-oxidative conditions is presented.

A mild, phosphine-mediated partial reduction of alkynyl carbonyls to the corresponding alkenes was developed. Tuning of the reaction conditions led to either the (E)- or (Z)-diastereomer with high selectivity. A range of alkynyl esters, amides, and ketones were reduced to form alkenes in good to high yields and with excellent functional group tolerance.