[2+2+1+1] Cycloaddition for de novo Synthesis of Densely Functionalized Phenols.

A unique benzannulation strategy for regioselective de novo synthesis of densely functionalized phenols is described. Through metal-mediated formal [2+2+1+1] cycloaddition of two different alkynes and two molecules of CO, a series of densely functionalized phenols were obtained. The benzannulation strategy allows efficient regioselective installation up to five different substituents on a phenol ring. The resulting phenols have a substitution pattern different from those obtained from Dötz and Danheiser benzannulations.

Oxidation-induced coupling reactions of bi(metallacycloprop-1-ene) complexes.

The feasibility of coupling of two carbene ligands of biscarbene complexes LnM(CR2)2 to form alkene complexes LnM(η2-R2CCR2) was predicted theoretically as early as 1982. However, until now, there appear still no reports on carbene coupling reactions of well-defined biscarbene complexes. This work reports oxidation-induced coupling reactions of bi(metallacycloprop-1-ene) complexes to give η4-butadiene complexes, a unique example of coupling of two carbene ligands of biscarbene complexes.