Synthesis of Imidazolidin-2-ones and Imidazol-2-ones via Base-Catalyzed Intramolecular Hydroamidation of Propargylic Ureas under Ambient Conditions

Abstract

The first organo-catalyzed synthesis of imidazolidin-2-ones and imidazol-2-ones via intramolecular hydroamidation of propargylic ureas is reported. The phosphazene base BEMP turned out to be the most active organo-catalyst compared with guanidine and amidine bases. Excellent chemo- and regioselectivities to five-membered cyclic ureas have been achieved under ambient conditions, with a wide substrate scope and exceptionally short reaction times (down to 1 min). A base-mediated isomerization step to an allenamide intermediate is the most feasible reaction pathway to give imidazol-2-ones, as suggested by DFT studies.

Unexpected Stereoselective Access to 2‐Aminooxazolines from Propargyl Ureas by Silver Salts under Mild Conditions

“…If another propargylic function is present at the other N (R 1 =propargyl fragment) and R 2 and R 4 are hydrogens, a second annulation process takes place in a regioselective 6 ‐ endo ‐ dig , [16] providing the final oxazolopyrimidine product 4 (Scheme 3, path b). Remarkably, compared to our previous base‐catalyzed protocol, [10] the exclusive formation of Z configuration on the exocyclic C−C double bond is observed, and moreover, ureas bearing alkyl substituents on the N (R 1 ) can be competent substrates, widening the scope of previously reported methods [6,8,9] …”

Carboxylative Cyclization of a Propargylic Amine with CO₂ Catalyzed by a Silica-Coated Magnetite

“…Degassed toluene and 2-propanol were prepared by freeze-pump-thaw cycling of commercially available dry toluene and 2-propanol for the synthesis of the 2-oxazolidinone 2 and for the washing of a silica-coated magnetite 3, respectively. Propargylic amines 1a, 20) 1c, 21) and 1h 7) were synthesized by the condensation of the corresponding propargylic halides and benzylamine. 20) Propargylic amine 1d was synthesized by the condensation of the corresponding propargylic primary amine and benzyl chloride.…”

New multicomponent reactions in water: a facile synthesis of 1,3-dioxo-2-indanilidene-heterocyclic scaffolds and indenoquinoxalines through reaction of ninhydrin-malononitrile adduct with diverse N-binucleophiles

“…1. [28][29][30] Indeno[1,2-b]quinoxaline skeleton exist in a large number of drug candidates (Fig. 1).…”