Synergistic Cooperative Effect of L‐Arginine‐[bmim]Br in Cascade Decarboxylative Knoevenagel‐Thia‐Michael Addition Reactions: Green Approach Towards C−S Bond Formation with In Situ Generated Unactivated α,β‐Unsaturated Ester

Abstract

In this report, a synergistic combination of L-arginine and [bmim]Br has been realized for the first time towards step-economical synthesis of b-aryl-b-sulfanyl esters from aromatic aldehyde, malonate and thiol via cascade thia-Michael addition reaction on in situ formed unactivated b-aryl-a,b-unsaturated esters (via decarboxylative Knoevenagel reaction) under metal-and acid/base-free conditions. Furthermore, the gram scalability and recyclability of the catalytic system (up to 5 cycles) makes our one-pot two-step protocol more economically efficient and synthetically attractive for cascade CÀC and CÀS bond formation than traditional two-step methods. The synergistic interaction of the catalytic system i. e. L-arginine with [bmim]Br has been probed by NMR ( 1 H and 13 C) studies. employing multicomponent cascade reaction strategy under the influence of green cooperative catalysis is not reported in the literature.Recently, a drift has been observed from the traditional mono-catalysis towards contemporary multi-catalysis particularly cooperative catalysis [15][16][17][18][19][20] which has allowed chemists to venture into the untouched horizon of organic synthesis by improving the reactivity and selectivity of the reactions. Inspired by the robustness of the synergistic [15][16][17] cooperative effect, we envisaged its potential for effective cascade decarboxylative Knoevenagel condensation [21][22][23] and nucleophilic thia-Michael addition reaction to afford the corresponding b-aryl-b-sulfanyl esters via in-situ generated unactivated b-aryl-a,b-unsaturated ester.In this report, a synergistic combination of Larginine and [bmim]Br promoted cascade decarboxylative Knoevenagel-thia-Michael addition reaction under metal-and acid/base-free conditions is described employing aldehyde, monoethyl malonate and thiol as commercially available starting materials towards synthesis of b-aryl-b-sulfanyl ester via CÀC and CÀS bond formation in one pot (Scheme 1).

Ionic-Liquid-Catalyzed Access to CTr: An Antitumor Agent

“…Presumably, 7 could be better stabilized by the second H-bond formed via a 6-membered ring between the HSO 4 – proton and the N atom of 3 . Intercomplex (or trimerization-like) interaction among three units of 7 assembled a supramolecule ( 8 ) via the H-bonds between the C 2 –H in one complex and the Bn-linked O atom in another. − As a precursor intermediate, 8 was computed to be more stable than its variants (Scheme ; Figure b and S4). The HSO 4 – protons of 8 selectively promoted the formation of three covalent bonds between C 3 and C 8 in different complexes, with the ILs released for next catalytic cycle and benzyl alcohol (verified by TLC) liberated to form trispirocyclic intermediate ( 9 ).…”

Synergistic Dual Role of [hmim]Br-ArSO2Cl in Cascade Sulfenylation–Halogenation of Indole: Mechanistic Insight into Regioselective C–S and C–S/C–X (X = Cl and Br) Bond Formation in One Pot

“…To understand the synergistic effect of water, initially sulfenylation of indole ( 1e ) was conducted with 2b in [hmim]­Br, which provided the product 3f in 72% yield at rt in 5 h, whereas the yield of product 3f drastically decreased to 10% when anhydrous [hmim]Br (lyophilized or vacuum-dried to remove traces of water from IL) was used. When 50 μL of water was charged during the sulfenylation of 1e , the product 3f was achieved in 82% yield at rt, while product 4n was obtained in 78% yield at 50 °C (Scheme ), which confirms the synergistic , and cooperative role of water during sulfenylation and sulfenylation–halogenation of indole with [hmim]­Br-ArSO 2 Cl.…”

Towards an Understanding of the “Ambiphilic” Character of Ionic Liquids for Green Synthesis of Chemically Diverse Architectures

“…Sinha et al. for the first time harnessed the synergistic, cooperative effect of L‐arginine‐[bmim]Br for thia‐Michael addition reaction on in situ generated α,β‐unsaturated esters which are low reactive electrophile via decarboxylative Knoevenagel reaction (Scheme ) . The crucial cooperative interaction of L‐arginine‐[bmim]Br enabled the synthesis of desired product 80 by employing arange of aromatic, heteroaromatic and aliphatic substituted β‐sulfanyl esters with varied aromatic andaliphatic thiol.…”