Kinetic Resolution of Oxiranes by Use of Chiral Lewis Acid Catalysts

Kinetics and Mechanism of the Reaction between Barbituric Acid and Glycidol, Part III: Methylene Group Reaction with Glycidol at High Concentration

“…The methylene group of BA has an acid dissociation constant equal to 1.26 × 10 −4 , which suggests its involvement in the reaction with oxiranes by hydrogen transfer as it was observed previously for the reactions between oxiranes and carboxylic acid of comparable acid dissociation constants .…”

“…Barbituric acid (BA) has two imide groups O═C─NH─C═O with slightly acidic N─H hydrogen. Although not plenty of data are available on imide reactivity toward oxirane , much more is known on various reaction mechanisms of oxiranes with alcohols , phenols , thiols , carboxylic acids , and amines depending on medium of reaction, acidity of substrates and products, and kind of catalyst . The mechanism of isomerization of imides substituted with oxirane and oxethane groups on nitrogen was examined .…”

Sustainable metal-based catalysts for the synthesis of cyclic carbonates containing five-membered rings

“…Brunner et al reported a method for the kinetic resolution of racemic epoxides using chiral binol ligands on titanium. 105 The authors formed the active chiral complex in situ by simply adding together a titanium acetate salt and one equivalent of the enantiopure binol ligand. Both epichlorohydrin 3e and styrene oxide 3b were studied, with the best result being for 3b, which, at a conversion of 41% gave 24% ee for unreacted epoxide and 35% ee for cyclic carbonate 4b (s = k fast /k slow = 2.6) in a reaction carried out at room temperature for 24 hours using 5 bar carbon dioxide pressure, 1 mol% catalyst and binol and 4 mol% of tetrabutylammonium iodide.…”

“…The use of dimethylaminopyridine as a co-catalyst is however problematic as this is highly toxic. 105 It is to be hoped that further research in this area can overcome these limitations.…”

Transformation of oxiranes into other oxygen-containing heterocyclic systems

“…The proposed mechanism is confirmed by the formation of carbonate 145 as the only product; alternative preliminary reaction of carbon dioxide with triethylamine would give rise to stereoisomeric product 146. By the reaction with 2-phenyloxirane Brunner et al [140] succeeded in obtaining the corresponding carbonate in up to 40% ee using chiral Lewis acids as catalysts. By the reaction with 2-phenyloxirane Brunner et al [140] succeeded in obtaining the corresponding carbonate in up to 40% ee using chiral Lewis acids as catalysts.…”