190442-40-1Relevant academic research and scientific papers
Carbon dioxide as a carbonylating agent in the synthesis of 2-oxazolidinones, 2-oxazinones, and cyclic ureas: Scope and limitations
Paz, Jairo,Perez-Balado, Carlos,Iglesias, Beatriz,Munoz, Luis
experimental part, p. 3037 - 3046 (2010/07/15)
Carbon dioxide can be used as a convenient carbonylating agent in the synthesis of 2-oxazolidinones, 2-oxazinones, and cyclic ureas. The transient carbamate anion generated by treating a primary or secondary amine group in basic media can be activated with phosphorylating agents such as Diphenylphosphoryl azide (DPPA) and Diphenyl chlorophosphate (DPPCl) but also with other types of electrophiles such as SOCl2, TsCl, or AcCl. The intramolecular trapping of the activated carbamate by a hydroxyl group leads to the formation of 2-oxazolidinones or 2-oxazinones in good to excellent yields. This methodology was successfully applied to the synthesis of cyclic ureas up to 7-membered rings from the corresponding diamines.
Stereoselective reactions, 25. Enantioselective deprotonation of prochiral 4-substituted cyclohexanones by chiral chelated lithium amides
Shirai, Ryuichi,Sato, Daisaku,Aoki, Kazumasa,Tanaka, Masahide,Kawasaki, Hisashi,Koga, Kenji
, p. 5963 - 5972 (2007/10/03)
Enantioselective deprotonation of prochiral 4-substituted cyclohexanones (4a-d) by chiral chelated lithium amides (8a-k) in the presence of excess trimethylsilyl chloride was realized to give the corresponding chiral silyl enol ethers (6a-d) in up to 89% ee. It is shown that enantioselectivity of the reaction is dependent on the solvent used, but becomes almost independent on the solvent in the presence of HMPA. The sense of asymmetric induction can be correlated to the configuration at the chiral carbon bearing amide nitrogen of the lithium amide.
