Micro-flow synthesis and structural analysis of sterically crowded diimine ligands with five aryl rings

• Shinichiro Fuse,
• Nobutake Tanabe,
• Akio Tannna,
• Yohei Konishi and
• Takashi Takahashi

Beilstein J. Org. Chem. 2013, 9, 2336–2343, doi:10.3762/bjoc.9.268

• ligands exerted high polymerization activity in the ethylene homopolymerization and copolymerization of ethylene with polar monomers. Keywords: amidine formation; diimine; flow chemistry; polymerization; Introduction The design of a ligand is a key step in the development of new catalysts because the

Synthetic studies towards bottromycin

• Stefanie Ackermann,
• Hans-Georg Lerchen,
• Dieter Häbich,
• Angelika Ullrich and
• Uli Kazmaier

Beilstein J. Org. Chem. 2012, 8, 1652–1656, doi:10.3762/bjoc.8.189

• reactions are described as an excellent synthetic tool for the synthesis of sterically highly hindered endothiopeptides. S-Methylation and subsequent amidine formation can be carried out in an inter- as well as in an intramolecular fashion. The intramolecular approach allows the synthesis of the bottromycin

• this approach failed (as did all other activations investigated) because of the formation of thiazolone side product, which could not be cyclized. In parallel, we tried to figure out if the amidine formation is possible with sterically hindered endothiopeptides (Scheme 2). As a model substrate we chose

• obtained from endothiopeptide 2. Here, the expected amidine was only formed in a trace amount, and a range of side products was obtained. Therefore, we decided to change our strategy and to replace the intermolecular amidine formation by an intramolecular one. In this case the peptide ring should be formed