Effective Guanidine-Catalyzed Synthesis of Carbonate and Carbamate Derivatives from Propargyl Alcohols in Supercritical Carbon Dioxide
作者:Nicola Della Ca'、Bartolo Gabriele、Giuseppe Ruffolo、Lucia Veltri、Tito Zanetta、Mirco Costa
DOI:10.1002/adsc.201000607
日期:2011.1.10
The reactions of propargyl alcohols with carbondioxide in supercriticalcarbondioxide or in acetonitrile with gaseous carbondioxide in the presence of organic bases as catalysts have been examined. Bicyclic guanidines are effective catalysts for the formation of α‐methylene cyclic carbonates under mild reaction conditions. Oxoalkyl carbonates, oxoalkyl carbamates or α‐methyleneoxazolidinones are
Boosting the Catalytic Performance of Organic Salts for the Fast and Selective Synthesis of α-Alkylidene Cyclic Carbonates from Carbon Dioxide and Propargylic Alcohols
carboxylative coupling of CO2 with propargylicalcohols is receiving increasing interest but requires the use of catalysts that are most often added in large quantities and/or lack selectivity. Herein, we describe the fine‐tuning of the structure of organocatalysts of the ammonium‐type that enables us to identify the important structural parameters that dictate their catalytic performance. Tetrabutylammonium
n‐Tetrabutylammonium organic salts were used for the first time as catalysts for the coupling of CO2 with 2‐methyl‐3‐butyn‐2‐ol to form an α‐methylene cyclic carbonate. Final yields up to 98 % were reached in less than 10 h at 353 K and 3 MPa under solvent‐free conditions. A particular synergistic effect between the cation and the anion of the organocatalyst was demonstrated through catalyst screening
The metal‐free coupling of a propargylic alcohol with CO2 catalysed by guanidine derivatives was investigated in detail through the combination of online kinetic studies by in situ attenuated‐total reflection IR (ATR–IR) spectroscopy and DFT calculations. Bicyclic guanidines, namely 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) and 7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (MTBD) are effective catalysts
AbstractGetting a fix: N‐heterocyclic carbenes (NHCs) and NHC–CO2 adducts serve as potent organocatalysts for carbonate synthesis by the addition of a CO2 unit to propargylic alcohols or epoxides under mild and solvent‐free reaction conditions (see scheme). The enhanced Lewis basicity of imidazol‐2‐ylidenes bearing electron‐donating alkyl groups on the nitrogen atoms leads to utilizing CO2 as a nucleophilic fragment in the chemical fixation processes.magnified image