A Catalytic Version of the Knorr Pyrrole Synthesis Permits Access to Pyrroles and Pyridines.

Aromatic -heterocycles, such as pyrroles and pyridines, are important natural products and bulk and fine chemicals with numerous applications as active ingredients of pharmaceuticals and agrochemicals, as catalysts, and in materials sciences. We report here a catalytic version of the Knorr pyrrole synthesis in which simple and diversely available starting materials, such as 1,2-amino alcohols or 1,3-amino alcohols and keto esters, undergo a dehydrogenative coupling to form pyrroles and pyridines, respectively. Our reaction forms hydrogen as a collectible (and usable) byproduct and is mediated by a well-defined Mn catalyst.

A Selective Iron(I) Hydrogenation Catalyst.

Iron is the most abundant transition metal of the Earth's crust, and the understanding of its function in key technologies, such as catalysis, is highly important. We report here on an iron(I) hydrogenation catalyst. Our catalyst activates hydrogen via heterolytic bond cleavage, forms a monohydride, and hydrogenates polar double bonds via a bimetallic pathway (potassium-assisted hydride transfer).

Synthesis of Branched α-Olefins via Trimerization and Tetramerization of Ethylene.

α-Olefins are very important bulk and fine chemicals and their synthesis from ethylene, an abundantly available and inexpensive feedstock, is highly attractive. Unfortunately, the direct or on-purpose synthesis of olefins from ethylene is limited to three examples, 1-butene, 1-hexene, and 1-octene, all having a linear structure. Herein, the direct synthesis of 3-methylenepentane and 4-ethylhex-1-ene, branched trimerization, and tetramerization products of ethylene, respectively, is reported.

A Closed-Loop Recyclable Low-Density Polyethylene.

Low-density polyethylene (LDPE) is one of the most important plastics, which is produced unfortunately under extreme conditions. In addition, it consists of robust aliphatic C─C bonds which are challenging to cleave for plastic recycling. A low-pressure and -temperature (p = 2 bara, T = 70 °C) macromonomer-based synthesis of long chain branched polyethylene is reported.

Unusual coordination mode for 1,3-diphosphete ligands towards a Cr-Cr quintuple bond complex.

The reaction of LCrCrL (L = NCH, 1) with the phosphaalkynes R-C≡P (R = Bu, Me, Ad) yields the neutral dimerisation compounds [LCr(μ,η:η:η:η-PCR)] (R = Bu (2), Me (3)) and the tetrahedrane complex [LCr(μ,η:η-PCAd)] (4). The 1,3-diphosphete ligands in complexes 2 and 3 are the first to possess this structural feature spanned over a metal-metal multiple bond, while the slightly bigger adamantyl phosphaalkyne remains a monomer in 4 with a side-on coordination mode.