Highly Selective Carboxylative Cyclization of Allenylmethylamines with Carbon Dioxide Using N-Heterocyclic Carbene-Silver(I) Catalysts
摘要:
Silver(I) carboxylate complexes promote the carboxylative cyclization of allenylmethylamines to afford 5-alkenyl-1,3-oxazolidin-2-ones in 2-propanol. The use of an N-heterocyclic carbene ligand (IPr) under pressurized CO2 is effective in suppressing the intramolecular hydroamination that leads to 2,5-dihydropyrroles. The mechanism involving a nucleophilic attack of the carbamate of the allene moiety and a subsequent protonation was realized on the basis of experimental and theoretical results involving a model intermediate, the alkenylgold(I) complex, which was synthesized from Au(OH)(IPr) and 1-methylamino-2,3-butadiene.
A new entry for the synthesis of 3-alkyl substituted 5-vinyloxazolidin-2-one derivatives 2 from cis-2-butenylene-1,4-dicarbonate 1 and primary amines mediated by palladium–phosphine catalysts is described. The scope and limitation, a plausible mechanism, and an asymmetric version of the reaction are also discussed.
Palladium-catalyzed carboxylative cyclization of α-allenyl amines in dense carbon dioxide
作者:Yoshihito Kayaki、Naoko Mori、Takao Ikariya
DOI:10.1016/j.tetlet.2009.09.015
日期:2009.11
Carboxylative transformation of 2,3-allenic amines into 5-vinyl-1,3-oxazolidin-2-ones was promoted by palladium catalysts under a pressurized CO2 condition. The presence of a stereogenic center adjacent to the allene group resulted in the formation of the corresponding cyclic urethane as a single trans-diastereomer.
Reaction of dimethyl (Z)-2-butenylene dicarbonate la with primary amines in the presence of [Pd(eta(3)- C3H5)Cl](2) and 1,1'-bis(diphenylphosphino)ferrocene (dppf) produced vinyl-oxazolidone compounds 2 in up to 70% yield. (C) 2000 Elsevier Science Ltd. All rights reserved.