Cobalt-Catalyzed Carbozincation of Ynamides.

An original cobalt-catalyzed ynamide carbozincation leading mainly to diverse 3-aryl enamides with mild reaction conditions and good functional-group tolerance has been developed. This reaction displays an excellent regio- and total stereoselectivity and opens the way to appealing synthetic applications. Moreover, this approach allows the selective synthesis of biologically relevant 3,5-disubstituted oxazolone frameworks.

Catalytic α-Arylation of Imines Leading to N-Unprotected Indoles and Azaindoles.

A palladium N-heterocyclic carbene catalyzed methodology for the synthesis of substituted, N-unprotected indoles and azaindoles is reported. The protocol permits access to various, highly substituted members of these classes of compounds. Although two possible reaction pathways (deprotonative and Heck-like) can be proposed, control experiments, supported by computational studies, point toward a deprotonative mechanism being operative.

Palladium-catalyzed α-arylation of arylketones at low catalyst loadings.

A general catalytic protocol for the α-arylation of aryl ketones has been developed. It involves the use of a preformed, bench-stable Pd-N-heterocyclic carbene pre-catalyst bearing IHept as an ancillary ligand, and allows the coupling of various functionalized coupling partners at very low catalyst loading. Careful choice of the solvent/base system was crucial to obtain optimum catalyst performance. The pre-catalyst was also successfully tested in the synthesis of an industrially relevant compound.

Reductive cross-coupling reactions between two electrophiles.

Reductive cross-electrophile coupling reactions have recently been developed to a versatile and sustainable synthetic tool for selective C-C bond formation. The employment of cheap and abundant electrophiles avoids the pre-formation and handling of organometallic reagents. In situ reductive coupling is effected in the presence of a transition-metal catalyst (Ni, Co, Pd, Fe) and a suitable metallic reductant (Mn, Zn, Mg). This Concept article assesses the current state of the art and summarizes recent protocols with various combinations of alkyl, alkenyl, allyl, and aryl reagents and highlights key mechanistic studies.

Cobalt-catalysed synthesis of highly substituted styrene derivatives via arylzincation of alkynes.

A new two-step procedure was developed by carbozincation of internal and terminal alkynes to synthesise highly functionalised vinylzinc bromides. Various tri and tetrasubstituted alkenes were prepared in moderate to good yields under mild reaction conditions in a stereo-selective manner. This methodology represents an interesting alternative to previously known methods.