Non-C2-Symmetric Chiral-at-Ruthenium Catalyst for Highly Efficient Enantioselective Intramolecular C(sp3)-H Amidation.

A new class of chiral ruthenium catalysts is introduced in which ruthenium is cyclometalated by two 7-methyl-1,7-phenanthrolinium heterocycles, resulting in chelating pyridylidene remote N-heterocyclic carbene ligands (rNHCs). The overall chirality results from a stereogenic metal center featuring either a Λ or Δ absolute configuration. This work features the importance of the relative metal-centered stereochemistry. Only the non-C2-symmetric chiral-at-ruthenium complexes display unprecedented catalytic activity for the intramolecular C(sp3)-H amidation of 1,4,2-dioxazol-5-ones to provide chiral γ-lactams with up to 99:1 er and catalyst loadings down to 0.005 mol % (up to 11 200 TON), while the C2-symmetric diastereomer favors an undesired Curtius-type rearrangement. DFT calculations elucidate the origins of the superior C-H amidation reactivity displayed by the non-C2-symmetric catalysts compared to related C2-symmetric counterparts.

Electrochemical Synthesis of Aryl Iodides by Anodic Iododesilylation.

An electrochemical access to iodinated aromatic compounds starting from trimethylsilyl-substituted arenes is presented. By design of experiments, highly efficient and mild conditions were identified for a wide range of substrates. A functional group stability test and the synthesis of an important 3-iodobenzylguanidine radiotracer illustrate the scope of this process.

Suzuki Cross-Coupling for Post-Complexation Derivatization of Non-Racemic Bis-Cyclometalated Iridium(III) Complexes.

A straightforward method for post-complexation derivatizations of diastereo- and enantiomerically pure bis-cyclometalated benzoxazole and benzothiazole iridium(III) complexes is reported. Triflate- and bromine-functionalized iridium(III) complex dimers, represented as [Ir(µ-Cl)(C^N)2 ]2 , were converted to the corresponding diastereomeric complexes, represented as Ir(C^N)2 (N^O), using readily available chiral salicyloxazolines and salicylthiazolines as ancillary ligands, which are represented as N^O. The Ir(C^N)2 (N^O) complexes, formed as mixtures of diastereomers, were then resolved by flash chromatography and the diastereomerically pure complexes Ir(C^N)2 (N^O) subjected to Suzuki cross-couplings. The post-complexation cross-couplings proceed without affecting the metal-located stereocenter and hence provide post-complexation derivatized non-racemic iridium(III) complexes, which were not easily accessible with previous methods. This strategy expands the toolbox to access functionalized non-racemic iridium(III) complexes for diverse applications in the life sciences, materials sciences, and catalysis.