Copper Catalyzed Borylation of Alkynes: An Experimental Mechanistic Study.

The copper catalyzed hydroboration of alkynes with Bpin was studied by in detail studies of individual relevant steps along the catalytic pathway. A number of reaction steps were retraced by in situ NMR spectroscopy as well as central intermediates and side-products were isolated and comprehensively characterized. A copper boryl complex is central to the catalytic process by inserting the terminal alkyne substrate into the B-Cu bond.

Synthesis, Reactivity and Coordination Chemistry of Group 9 PBP Boryl Pincer Complexes: [(PBP)M(PMe)] (M = Co, Rh, Ir; = 1, 2).

The unsymmetrical diborane(4) derivative [(d(CHP(Pr))abB)-Bpin] () proved to be a versatile PBP boryl pincer ligand precursor for Co(I) (, ), Rh(I) (-) and Ir(I/III) (-, -) complexes, in particular of the types [(d(CHP(Pr))abB)M(PMe)] (-) and [(d(CHP(Pr))abB)M-PMe] (-). Whilst similar complexes have been obtained before, for the first time, the coordination chemistry of a homologous series of PBP pincer complexes, in particular the interconversion of the five- and four-coordinate complexes -/-, was studied in detail. For Co, instead of the mono phosphine complex , the dinitrogen complex [(d(CHP(Pr))abB)Co(N)(PMe)] () is formed spontaneously upon PMe abstraction from in the presence of N.

Total Synthesis of Indolizidine Alkaloids via Nickel-Catalyzed (4 + 2) Cyclization.

A Ni-catalyzed (4 + 2) cycloaddition of alkynes and azetidinones toward piperidinones was used as key reaction in the enantioselective synthesis of naturally occurring indolizidine alkaloids. The reaction benefits from the use of an easily accessible azetidinone as an advanced and divergent intermediate to build the indolizidine core. This methodology has been applied in the total syntheses of (+)-septicine, (+)-ipalbidine, and (+)--antofine to illustrate the applicability of the general approach.