Enantioselective addition of carbon acids to α-nitroalkenes: the first asymmetric aminocatalytic reaction in liquefied carbon dioxide

A Greener, Efficient Approach to Michael Addition of Barbituric Acid to Nitroalkene in Aqueous Diethylamine Medium

“…Interestingly, the Michael product was separated in enol form and not in keto form in very good to excellent yields ( Table 2, entries [13][14][15][16][17][18][19][20]. Finally, to show the generality of the procedure, we tested ferrocene nitroalkene as Michael acceptor and the products were obtained in very good yields (Table 2, entries 9, 19).…”

“…[10][11][12][13]. Extensive studies have been devoted to the development of catalytic systems for Michael additions of various active methines such as pronucleophiles to nitroalkenes including cinchona organocatalysts [14], enzymes [15], various chiral amines [16,17], transition metal-free organocatalysts [18][19][20] and chiral metal complexes [21][22][23][24][25].…”

Investigating the efficacy of green solvents and solvent-free conditions in hydrogen-bonding mediated organocatalyzed model reactions

“…22 Among greener solvents, carbon dioxide (CO 2 ) has attracted signicant interest in green chemistry due to its availability, non-toxicity, non-ammability, and stability. 23,24 Liquid and supercritical CO 2 have been extensively studied in chemical reactions, including asymmetric synthesis using organometallics [25][26][27][28][29] or biocatalysts. [30][31][32][33] Currently, there are limited studies on applying CO 2 as a reaction medium in asymmetric organocatalysis.…”

“…[30][31][32][33] Currently, there are limited studies on applying CO 2 as a reaction medium in asymmetric organocatalysis. 23,[34][35][36][37] Further research is necessary to comprehensively grasp the scope and limitations of environmentally friendly solvents.…”

Stereodivergent Michael addition of diphenylphosphite to α-nitroalkenes in the presence of squaramide-derived tertiary amines: an enantioselective organocatalytic reaction in supercritical carbon dioxide

“…Recently, we have discovered 11 that enantioselective organocatalytic reactions such as asymmetric additions of carbon acids to α-nitroalkenes in the presence of Takemoto's tertiary amine-thiourea organocatalyst 12 can be efficiently carried out in liquid carbon dioxide (liq-CO 2 ), which is produced from renewable natural ( plants) and industrial (burning of fuels) sources, and, along with supercritical carbon dioxide (sc-CO 2 ), is likely to be a prospective medium for future chemical processes. 13 Liq-CO 2 (100 bar, r.t.) enhances the reaction rate and reduces the appropriate catalyst loading without a detrimental effect on enantioselectivity as compared with corresponding reactions in organic solvents.…”