An efficient four-component cascade reaction for the synthesis of trisubstituted hexahydroimidazoA C H T U N G T R E N N U N G [1,2-a]pyridines starting from readily available aldehydes, ketones and ethane-1,2diamine catalyzed by p-toluenesulfonic acid is described. Two new cycles and five new bonds are constructed with all reactants being efficiently utilized in this transformation. The mechanism of the reaction was investigated and some crucial reaction intermediates were observed.
The combination of a chiral phosphate anion with a silver ion has been demonstrated as a powerful and synergistic ion pair catalyst for the aza-Mannich reaction. A series of valuable quaternary α,β-diamino acid derivatives was obtained in high yield, and with excellent diastereo- (up to 25:1 dr) and enantioselectivity (up to 99% ee). The adducts can be smoothly transformed into the corresponding protected chiral quaternary α,β-diamino acids by a one-pot hydrolysis reaction.
An N-heterocyclic carbene-catalyzed stereoselective Michael-Mannich-lactamization cascade reaction of tosyl-protected o-amino aromatic aldimines and 2-bromoenals for the construction of functionalized pyrrolo[3,2-c]quinolines with three consecutive stereocenters was achieved in good yields with excellent diastereo- and enantioselectivities.
Nature Communications 8: Article number: 15544 (2017); Published: 18 May 2017, Updated: 13 July 2018 In the originally published version of this Article, financial support was not fully acknowledged. The PDF and HTML versions of the Article have now been corrected to include support from the National Natural Science Foundation of China grant number 81573325.
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