1217436-37-7Relevant articles and documents
31P NMR Spectroscopically Quantified Hydrogen-Bonding Strength of Thioureas and Their Catalytic Activity in Diels-Alder Reactions
N?dling, Alexander R.,Jakab, Gergely,Schreiner, Peter R.,Hilt, Gerhard
supporting information, p. 6394 - 6398 (2016/02/18)
The hydrogen-bonding strength of a variety of commonly employed thiourea catalysts was quantified by using a trialkylphosphine oxide as a 31P NMR probe. Simple diarylthioureas and more complex bifunctional amine- and hydroxy-substituted thiourea derivatives were examined. Their catalytic activity was determined in a Diels-Alder reaction, and the obtained pseudo-first-order rate constants were correlated with the 31P NMR chemical shifts. A linear correlation between both variables was observed throughout the functionalized thioureas. The 31P NMR probe correlation fared better in comparison to a pK a correlation. Accordingly, the quantification presented herein by using a 31P NMR probe offers an elegant way to estimate the catalytic activity of thiourea catalysts in hydrogen-bond-activated reactions such as the Diels-Alder reaction. The correlation of 31P NMR shift values [Δδ(31P)] for the determination of hydrogen-bond strengths of thiourea derivatives with kinetic data [ln (k rel)]of thiourea-catalyzed Diels-Alder reactions is evaluated. A Hammett-type plot provides a more reliable correlation than the correlation of kinetic data with the pK a values of the thiourea derivatives.
Effective asymmetric Michael addition of acetone to nitroalkenes promoted by chiral proline amide-thiourea bifunctional catalysts
Wang, Qiao-Wei,Peng, Lin,Fu, Ji-Ya,Huang, Qing-Chun,Wang, Li-Xin,Xua, Xiaoying
experimental part, p. 340 - 351 (2010/08/04)
A series of secondary amine-thiourea catalysts 1a-1d derived from L-proline and chiral diamine were prepared and successfully applied to the Michael addition of acetone to trans-nitroalkenes in excellent yields (up to 99%) and enantioselectivities (44-91%
Effective construction of quaternary stereocenters by highly enantioselective α-amination of branched aldehydes
Fu, Ji-Ya,Xu, Xiao-Ying,Li, Yan-Chun,Huang, Qing-Chun,Wang, Li-Xin
supporting information; experimental part, p. 4524 - 4526 (2010/11/21)
A highly efficient enantioselective α-amination of branched aldehydes with azadicarboxylates promoted by chiral proline-derived amide thiourea bifunctional catalysts was developed for the first time, affording the adducts bearing quaternary stereogenic centers with excellent yields (up to 99%) and enantioselectivities (up to 97% ee).