DABCO-catalyzed reactions of hydrazones with activated olefins

P(III)-Mediated Formal Reductive N-H Bond Insertion Reaction of Hydrazones to α-Keto Esters

A diazo-, metal-, and base-free multi-substituted hydrazone synthesis via a formal reductive N-H bond insertion reactions of hydrazones to α-keto esters has been developed. The protocol features a broad substrate scope and good functional group tolerance, providing N-H bond insertion products in moderate to excellent yields. Moreover, P(III)-mediated N-H functionalization of pharmaceutical containing hydrazone moiety was also successfully achieved.

Cu(II)-Catalyzed Aminocyclization of N-Propargyl Hydrazones to Substituted Pyrazolines

An efficient route for the copper(II)-catalyzed synthesis of substituted pyrazolines from readily accessible N-propargyl hydrazones has been reported under open flask conditions via intramolecular C-N bond formation. N-acyl and N-tosyl-substituted pyrazolines have been prepared in moderate to excellent yields. Mechanistic investigations using NMR, high-resolution mass spectrometry (HRMS), and Hammett analyses suggest that the Cu(II) catalyst generally acts as a Lewis acid to form an iminium-ion intermediate via cyclization, which afforded the desired pyrazolines upon hydrolysis. One progesterone receptor antagonist has also been synthesized utilizing this reaction methodology.

Development of a DABCO-Succinic Acid Based Catalytic System for the Aza-Michael Addition and Aza-Michael/Knoevenagel Tandem Reaction of Thiazolidine-2,4-dione to Electron Deficient Alkenes

A DABCO catalyzed aza-Michael addition of thiazolidine-2,4-dione to a variety of electron deficient alkenes has been developed. Additionally, a DABCO/succinic acid salt system has been designed that allows for the one pot tandem aza-Michael/Knoevenagel reaction of thiazolidine-2,4-dione to give difunctionalized thiazolidine-2,4-dione products. To the best of our knowledge, this is the first example of a one-pot tandem aza-Michael/Knoevenagel reaction involving thiazolidine-2,4-dione.

Synthesis of trifluoromethylated pyrazolidines by [3 + 2] cycloaddition

[3 + 2] cycloaddition between trifluoromethylated N-acylhydrazones and nitroolefins in the presence of potassium hydroxide and Bu₄NI is developed to afford potentially bioactive trifluoromethylated pyrazolidines.

Reinvestigation of the reaction between 1,3-diketones and 2-hydroxyarylaldehydes: a short, atom-economical entry to tetrahydroxanthenones

A short and facile access to novel functionalized tetrahydroxanthenonesviaa DABCO-promoted tandem Knoevenagel condensation/hemiketalisation process from easily accessible substrates in a high yield.

Formation and aromatization of strained bicyclic pyrazolidines via tandem reaction of alkyl 2-aroyl-1-chlorocyclopropanecarboxylates with acylhydrazones

The formation and aromatization of strained bicyclic pyrazolidines.