Chiral Helical Oligotriazoles: New Class of Anion-Binding Catalysts for the Asymmetric Dearomatization of Electron-Deficient N-Heteroarenes

Abstract

Helical chirality and selective anion-binding processes are key strategies used in nature to promote highly enantioselective chemical reactions. Although enormous efforts have been made to develop simple helical chiral systems and thus open new possibilities in asymmetric catalysis and synthesis, the efficient use of synthetic oligo- and polymeric helical chiral catalysts is still very challenging and rather unusual. In this work, structural unique chiral oligotriazoles have been developed as C-H bond-based anion-binding catalysts for the asymmetric dearomatization of N-heteroarenes. These rotational flexible catalysts adopt a reinforced chiral helical conformation upon binding to a chloride anion, allowing high levels of chirality transfer via a close chiral anion-pair complex with a preformed ionic substrate. This methodology offers a straightforward and potent entry to the synthesis of chiral (bioactive)heterocycles with added synthetic value from simple and abundant heteroarenes.

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

“…The resultant close chiral anion-pair complexes would then undergo a chiral counterion-controlled asymmetric reaction with a nucleophile. This proposal was validated experimentally, and a chloride-induced conformational switch to form a helical backbone was experimentally observed by circular dichroism (CD) during the titration of L4 with TBAC [37]. …”

Double Stranded Helical Organo-lead 3D-Supramolecular Coordination Polymer Containing Copper Cyanide and Phenanthroline Ligand as Antimicrobial Agent

“…Helical structures have received special attention in the past decades as helicity is an essential element for bioactivity and also due to their potential applications in asymmetric catalysis [1,2], nonlinear optical materials [3], antitumor [4] and anti-inflammatory [5,6] activities. To date, quite a few single-or double-helical chains have been generated [7][8][9][10][11][12][13], with most helical polymers being obtained by using chiral ligands [14][15][16] or oligo-pyridines [17] and other optically active ligands [18,19].…”

“…On the other hand, the organometallic R 3 M ? (R = Me or Ph, M = Sn or Pb) unit can act as a connecting moiety by axial anchoring to two donor atoms, exhibiting trigonal bipyramidal configuration, creating structure of high dimensionality [2,26,29]. Herein, we tried to introduce the Me 3 Pb ?…”

“…The synthesis of the SCP 1 was performed in H2 O/acetonitrile system. A solution of 44 mg (0.155 mmol) of K 3 [Cu(CN) 4 ] in 5 mL H 2 O was added, with gentle stirring to a mixture of solutions containing 136 mg (0.47 mmol) of Me 3 PbCl in 5 mL H 2 O and 30 mg (0.155 mM) of phen in 5 mL of acetonitrile.…”

β‐Hydroxy‐tetrahydroquinolines from Quinolines Using Chloroborane: Synthesis of the Peptidomimetic FISLE‐412

“…[1] These compounds are synthetically challenging, they are usually made through multistep synthesis. [1a, 2] Wide varieties of reducing agents have been used extensively to make THQ, [3] however, very limited reduction approaches were synchronized with significant functionalization. [4] Stereoselective silylative reduction of quinolines using B(C 6 F 5 ) 3 and Et 2 SiH 2 is a good example to access β -silylated THQs, [4a] which can be used as precursors for wide range of transformations including β -hydroxy-THQs.…”