168049-26-1Relevant articles and documents
Application of Proline-Derived (Thio)squaramide Organocatalysts in Asymmetric Diels-Alder and Conjugate Addition Reactions
Bagi, Péter,Dargó, Gyula,Drahos, László,Huszthy, Péter,Kis, Dávid,Kupai, József,Mátrav?lgyi, Béla,Nagy, Sándor,Tóth, Blanka
, (2022/02/22)
The synthesis of chiral proline-derived squaramide and thiosquaramide organocatalysts, which are capable of the dual activation in asymmetric reactions is reported. The (thio)squaramide moiety can form hydrogen bonds to activate the substrates and to stereocontrol the reaction, while the pyrrolidine unit can form enamines to activate carbonyl compounds via aminocatalysis. Comparing the performance of thiosquaramide to squaramide, the Diels Alder reaction of (anthracen-9-yl)acetaldehyde and trans-?-nitrostyrene was examined, which has been investigated in the literature using quantum chemical calculations. Both squaramide and thiosquaramide gave excellent yields (up to 99%) and enantiomeric excess values (up to 98%). Moreover, their catalytic performance was compared in conjugate addition of lawsone to ?,?-unsaturated ?-keto ester.
Staudinger/aza-Wittig reaction to access Nβ-protected amino alkyl isothiocyanates
Santhosh,Durgamma,Shekharappa,Sureshbabu, Vommina V.
, p. 4874 - 4880 (2018/07/15)
A unified approach to access Nβ-protected amino alkyl isothiocyanates using Nβ-protected amino alkyl azides through a general strategy of Staudinger/aza-Wittig reaction is described. The type of protocol used to access isothiocyanates depends on the availability of precursors and also, especially in the amino acid chemistry, on the behavior of other labile groups towards the reagents used in the protocols; fortunately, we were not concerned about both these factors as precursor-azides were prepared easily by standard protocols, and the present protocol can pave the way for accessing title compounds without affecting Boc, Cbz and Fmoc protecting groups, and benzyl and tertiary butyl groups in the side chains. The present strategy eliminates the need for the use of amines to obtain title compounds and thus, this method is step-economical; additional advantages include retention of chirality, convenient handling and easy purification. A few hitherto unreported compounds were also prepared, and all final compounds were completely characterized by IR, mass, optical rotation, and 1H and 13C NMR studies.
Pyrrolidine modified PANF catalyst for asymmetric Michael addition of ketones to nitrostyrenes in aqueous phase
Du, Jianguo,Shuai, Bin,Tao, Minli,Wang, Guangwei,Zhang, Wenqin
, p. 2625 - 2631 (2016/05/24)
Three chiral pyrrolidine functionalized polyacrylonitrile fiber catalysts have been designed, prepared, and evaluated for their catalytic performance in asymmetric Michael addition of ketones to nitrostyrenes in water. With the optimized catalysts and conditions in hand, their reaction scope for nitrostyrenes was explored. Then the fiber catalysts were further applied to a packed-bed reactor for continuous-flow Michael addition. Based on the fact that organic solvent can inhibit the catalytic activity, a novel microenvironment catalytic mechanism is proposed.