Biobased chiral semi-crystalline or amorphous high-performance polyamides and their scalable stereoselective synthesis.

The use of renewable feedstock is one of the twelve key principles of sustainable chemistry. Unfortunately, bio-based compounds often suffer from high production cost and low performance. To fully tap the potential of natural compounds it is important to utilize their functionalities that could make them superior compared to fossil-based resources. Here we show the conversion of (+)-3-carene, a by-product of the cellulose industry into ε-lactams from which polyamides. The lactams are selectively prepared in two diastereomeric configurations, leading to semi-crystalline or amorphous, transparent polymers that can compete with the thermal properties of commercial high-performance polyamides. Copolyamides with caprolactam and laurolactam exhibit an increased glass transition and amorphicity compared to the homopolyamides, potentially broadening the scope of standard polyamides. A four-step one-vessel monomer synthesis, applying chemo-enzymatic catalysis for the initial oxidation step, is established. The great potential of the polyamides is outlined.

ortho-Phenylene bridged palladium bis-N-heterocyclic carbene complexes: synthesis, structure and catalysis.

A series of ortho-phenylene bridged palladium bis-NHC complexes has been synthesized. Complexes with imidazolium and benzimidazolium derived NHCs and methyl-/benzyl-wingtips are reported. Bis(benz)imidazoles with a doubly brominated ortho-phenylene bridge could be obtained by an electrophilic substitution reaction. The structure of the complexes could be confirmed by three solid-state structures. All catalysts have been tested in the catalytic functionalisation of propane. The catalytic activity is highly dependent on the ligand, whereas ligand effects on the regioselectivity (n/iso) are much smaller.

Stereoselective OsO4-catalyzed oxidative cyclization of 1,5-dienes.

The mechanism of the oxidation of 1,5-dienes with osmium tetroxide was investigated by density functional theory calculations (B3LYP/6-311+G*). The observed products, 2,5-bis(hydroxymethyl)tetrahydrofurans, are formed stereoselectively in a concerted reaction. Enantioselectivity could be induced by an enantioselective dihydroxylation followed by condensation of the 5,6-dihydroxyolefine with osmium tetroxide, while the diastereoselectivity is achieved by reaction of the 1,5-diene with osmium tetroxide and intermediate reoxidation of the osmium(VI) ester.