Enediyne-Comprising Amino Aldehydes in the Passerini Reaction

Multicomponent reactions represent a highly efficient approach to a broad spectrum of structurally diverse compounds starting from simple and affordable compounds. A focused library of tweezers-like compounds is prepared by employing the multicomponent Passerini reaction comprising enediyne-derived amino aldehydes. The reaction proceeds under mild conditions yielding Passerini products in good to excellent yields. Postcondensation modifications of Passerini products are demonstrated through a simple deprotection/coupling approach comprising amino functionality, furnishing enediyne cores with highly decorated arms

Chiral Brønsted Acid Catalyzed Enantioselective aza-Friedel–Crafts Reaction of Cyclic α‑Diaryl <i>N</i>‑Acyl Imines with Indoles

Asymmetric addition of indoles to cyclic α-diaryl-substituted <i>N</i>-acyl imines, which are generated <i>in situ</i> from 3-aryl 3-hydroxy­isoindolinones, is described. The transformation proceeds smoothly with a broad range of indoles and isoindolinone alcohols using a SPINOL-derived chiral Brønsted acid catalyst to afford α-tetrasubstituted (3-indolyl)­(diaryl)­methanamines in excellent yields and enantioselectivities (up to 98% yield, up to >99:1 e.r.). The origin of stereochemical induction is supported by DFT calculations and experimental data

“Backdoor Induction” of Chirality: Asymmetric Hydrogenation with Rhodium(I) Complexes of Triphenylphosphane-Substituted β‑Turn Mimetics

Bioconjugate bidentate ligands <b>2</b>–<b>10</b> were obtained by tethering triphenylphosphanecarboxylic acid to amino acid substituted spacers with different flexibility, ranging from a rigid enediyne-based β-turn inducer to flexible linear aliphatic chains with up to eight carbon atoms. The 21 synthesized ligands revealed up to 81% ee selectivity in rhodium-catalyzed asymmetric hydrogenation of α,β-unsaturated amino acids. The key feature of the catalysts is the prochiral coordination sphere of the catalytic metal while the chirality is transmitted by “backdoor induction” from distant hydrogen-bonded amino acids. DFT calculations were applied to study the structure and relative stability of the precatalytic organometallic Rh­(I) complexes, with particular emphasis on hydrogen-bonded secondary structures