Evaluation of Tungsten Catalysis among Early Transition Metals for -Aryl-2,3,4,5-tetraarylpyrrole Synthesis: Modular Access to N-Doped π-Conjugated Material Precursors.

Low-valent tungsten species generated from WCl and ,-bis(trimethylsilyl)-2,5-dimethyldihydropyrazine (-Me-DHP) promotes the catalytic formation of -phenyl-2,3,4,5-tetraarylpyrroles from diarylacetylenes and azobenzene (). An initial catalyst activation process is a three-electron reduction of WCl with -Me-DHP to afford transient 'WCl' species. Catalytically active bis(imido)tungsten(VI) species via successive one-electron reduction and N═N bond cleavage of was revealed by isolating W(═NPh)Cl(PMePh) from imidotungsten(V) trichloride and in the presence of PMePh.

CpTi(II) Mediated Rearrangement of Cyclopropyl Imines.

Ti-catalyzed oxidative alkyne carboamination with alkenes and azo compounds can yield either α,β-unsaturated imines or cyclopropyl imines through a common azatitanacyclohexene intermediate. Herein, we report the synthesis of a model azatitanacyclohexene complex () through the ring-opening of a cyclopropyl imine with CpTi(BTMSA) (BTMSA = bis(trimethylsilyl)acetylene). readily undergoes thermal or reductant-catalyzed ring contraction to an azatitanacyclopentene (), analogous to the proposed mechanism for forming α,β-unsaturated imines in the catalytic reaction.

α-Diimine synthesis titanium-mediated multicomponent diimination of alkynes with C-nitrosos.

α-Diimines are commonly used as supporting ligands for a variety of transition metal-catalyzed processes, most notably in α-olefin polymerization. They are also precursors to valuable synthetic targets, such as chiral 1,2-diamines. Their synthesis is usually performed through acid-catalyzed condensation of amines with α-diketones.

Multicomponent syntheses of 5- and 6-membered aromatic heterocycles using group 4-8 transition metal catalysts.

In this , we discuss recent syntheses of 5- and 6-membered aromatic heterocycles multicomponent reactions (MCRs) that are catalyzed by group 4-8 transition metals. These MCRs can be categorized based on the substrate components used to generate the cyclized product, as well as on common mechanistic features between the catalyst systems. These particular groupings are intended to highlight mechanistic and strategic similarities between otherwise disparate transition metals and to encourage future work exploring related systems with otherwise-overlooked elements.