Preparation of alkylidene cyclic carbonates via cyclization of propargylic carbonates

1,3-Dialkylimidazolium-2-carboxylates as versatile N-heterocyclic carbene–CO2 adducts employed in the synthesis of carboxylates and α-alkylidene cyclic carbonates

“…3 requires a catalyst. Several transition metals have been successfully employed including Pd, 29 Ru, 30 Co, 31 Cu, 32,33 and Ag, 34 but the reaction is also promoted by tertiary phosphines. 35, 36 An overview of data reported in the literature about this reaction allows to conclude that (i) tertiary propargyl alcohols are more reactive substrates; 37 (ii) higher yields are usually obtained when R 1 -R 2 (Eq.…”

“…3) are represented by linear alkyl groups (alcohols 11a-b, 65-99% yield), while substrates with R 1 -R 2 represented by bulky (alcohol 11c, 58-75% yield) or phenyl groups (alcohol 11d, 32-50% yield) gave lower yields. [29][30][31][32][33][34][35][36] Very recently a Japanese Patent 38 reported the use of imidazoland imidazolin-2-ylidenes with bulky N-alkyl and N-aryl substituents and their CO 2 -adducts as catalysts in the synthesis of carbonate 12a (obtained in 88% yield). These data confirm that NHCs compete with phosphines for donating properties 39 and catalytic activity, and open the question about the role of the NHC in the carboxylative cyclization reaction.…”

Effective Guanidine‐Catalyzed Synthesis of Carbonate and Carbamate Derivatives from Propargyl Alcohols in Supercritical Carbon Dioxide

“…This strategy is based on the "in situ" formation of propargyl carbonate HC CC(R anionic species. Methods based on the use of transition metals such as Ru, [5] Co, [6] Pd, [7] Cu, [8] Fe, [9] phosphines, [10] inorganic bases (K 2 CO 3 ) in the presence of crown ethers, [11] or organic bases such as DBU coupled to Ag salts [12] have been developed for the reaction of CO 2 with propargyl alcohols. Several reaction media have been used, such as conventional polar aprotic solvents, scCO 2 and ionic liquids in the presence of copper metal salts.…”

Polycondensation behavior between propargyl carbonates having a bulky ester group and bisphenols in the presence of Pd(0) catalyst: synthesis of exomethylene-containing polyethers

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] In these reactions, two consecutive nucleophilic attacks occur. A nucleophile attacks at the central carbon of the Z 3 -allenyl/propargyl intermediate generated by reaction of a propargylic carbonate with Pd(0) to yield a p-allylpalladium intermediate, which is successively attacked by a second nucleophile.…”