Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO₂ fixation by N-benzyl cyclic guanidine under dry and wet conditions

Abstract

The efficient CO2 fixation by N-benzyl cyclic guanidine 1 was achieved by bubbling dry CO2 through CH3CN at 25 °C for 2 h. In addition, the zwitterion adduct 2 and bicarbonate salt 3 were selectively prepared from 1 under dry (in anhydrous CH3CN) and wet (in CH3CN containing an equimolar amount of water for 1) conditions, respectively. Both compounds 2 and 3 were isolated as white solids and their structures were characterized in detail by elemental analysis, FTIR-ATR, solid-state NMR, TGA, and DFT calculation. These analytical results obviously revealed the formation of a zwitterion adduct and bicarbonate salt from N-benzyl cyclic guanidine and CO2. Especially, the zwitterion adduct of the monocyclic guanidine derivative and CO2 was isolated and characterized for the first time.

Claisen‐Schmidt Condensation and Domino Claisen‐Schmidt Condensation ‐ Michael Addition of 16‐Formyl Steroids in the Presence of Switchable Polarity Solvents

“…[7] Due to the efficiency of SPSs in carbon dioxide fixation, several studies can be found in the literature reporting on the physical and chemical properties of this special group of ionic liquids. [8][9][10][11][12] The basic component of the SPS can be used as a catalyst in base-catalyzed reactions. In such cases the molecular form of the SPS may play the dual role of catalyst and solvent.…”

One‐Step Synthesis of 3,4‐Disubstituted 2‐Oxazolidinones by Base‐Catalyzed CO2 Fixation and Aza‐Michael Addition

“…We propose a mechanism based on quantitative 13 C NMR experiments, an isolated acyclic carbamate, control experiments, and previous literature (Scheme ). Initially, TMG reacts reversibly with CO 2 to form a zwitterionic intermediate A , as has been previously established . Then, A undergoes CO 2 exchange with aniline 2 a to give the mixed carbamate B , as was observed by quantitative 13 C NMR studies (see the SI) .…”

“…Initially,T MG reacts reversibly with CO 2 to form az witterionic intermediate A,a sh as been previously established. [50][51][52] Then, A undergoes CO 2 exchange with aniline 2a to give the mixed carbamate B, [52][53][54] as was observed by quantitative 13 CNMR studies (see the SI). [55] In the following step, the mixed carbamate B reacts with Michael acceptor 1 by nucleophilic substitution of bromine to form the acyclic O-alkyl carbamate C and TMG·HBr.I ntermediate C was identified by using N-methylaniline as as ubstrate, leadingt o the isolation of acyclic carbamate 3r.N ext, highly soluble Cs 2 CO 3 regenerates TMG by deprotonation.…”

Zwitterion π–conjugated nanoporous polymer based on guanidinium and β-ketoenol as a heterogeneous organo-catalyst for chemical fixation of CO2 into cyclic carbonates

“…These cyclic carbonates are important as precursors of raw materials in the production of plastics, pharmaceutical chemical intermediates, aprotic polar solvents and biomedical applications [15][16][17]. Recently, numerous catalyst systems, such as ammonium and phosphonium salts, ionic liquids, cyclic amidines and guanidines, porous organic polymers, metal-organic frameworks (MOFs), have been developed 3 for this conversion [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Generally, homogeneous catalysts show effective catalytic activity with well-defined mechanisms but main drawbacks are the need for separations and the purification of products.…”