Electrostatically tuned phenols: a scalable organocatalyst for transfer hydrogenation and tandem reductive alkylation of N-heteroarenes

Abstract

Charging the catalytic site! Incorporation of charged arm on the phenol has tremendous increase in the catalytic activity compared to its uncharged counterpart. We also performed NMR studies to understand the mechanism of the activity.

Modular synthesis of spirocyclic carbonates: unravelling the synergistic interplay of electronic and electrostatic sites on phenolic catalyst

“…36,37 Alternatively, the ring expansion routed through cycloaddition and annulation reactions helps to retain the spirocyclic scaffold with the advantage of reactivity and atom economy. 22,38,39 Intrigued by these later advancements and inspired by the catalytic power of our recently reported phenolbased organocatalyst in an aprotic polar solvent, 34 we envisioned exploring its activity towards the installation of CO 2 in spiro-fused oxirane 1a (Fig. 2).…”

“…30,33 In one of our recent works, we revealed the catalytic activity of electrostatically tuned phenols (ETPs) for tandem transfer hydrogenation and N-alkylation of quinoline derivatives with distinctive advantages. 34 These findings and evidence from literature led us to hypothesize that a molecular construct derived from phenol with reasonable chemical functionalities (alkyl ammonium center and bulky electron donating group, a dynamic duo) located on either side of the hydroxyl group may deliver synergistic catalytic activity towards the chemical fixation of CO 2 with spiroepoxides. To test this hypothesis variety of phenol-derived catalysts (PDCs) were synthesized 34 and studied for their activity.…”

“…34 These findings and evidence from literature led us to hypothesize that a molecular construct derived from phenol with reasonable chemical functionalities (alkyl ammonium center and bulky electron donating group, a dynamic duo) located on either side of the hydroxyl group may deliver synergistic catalytic activity towards the chemical fixation of CO 2 with spiroepoxides. To test this hypothesis variety of phenol-derived catalysts ( PDCs ) were synthesized 34 and studied for their activity. The rationale is that the bulky ( tert -butyl) group in one side arm of the phenol may retard the resonance of the hydroxyl group with the phenyl ring and probably enhance the acidity.…”

Ruthenium/HI-catalyzed direct hydromethylation of indoles and quinolines in DME

“…[8][9][10][11][12][13][14][15] Although significant advances have been made, these procedures are traditionally performed using aromatic primary amine as the substrate, 3,4 and considerably less attention has been devoted to saturated N-heterocycles, such as piperidine or pyrrolidine and its derivatives. [16][17][18] On the other hand, the direct (transfer) hydrogenation of N-heteroarenes is one of the simplest methods for the synthesis of saturated N-heterocycles, [19][20][21][22][23][24][25][26][27][28][29][30][31][32] by which N-methyl saturated N-heterocycles are constructed via N-methylation. Typically, the traditional preparation of N-methyl saturated N-heterocycles (such as 1-methylindoline) usually involves two steps (Scheme 1c).…”

“…On the other hand, the direct (transfer) hydrogenation of N-heteroarenes is one of the simplest methods for the synthesis of saturated N-heterocycles, 19–32 by which N -methyl saturated N-heterocycles are constructed via N -methylation. Typically, the traditional preparation of N -methyl saturated N-heterocycles (such as 1-methylindoline) usually involves two steps (Scheme 1c).…”