Preparation of Acidic 5-Hydroxy-1,2,3-triazoles via the Cycloaddition of Aryl Azides with ß-Ketoesters.

Herein, a high-yielding cycloaddition reaction of ß-ketoesters and azides to provide 1,2,3-triazoles is described. The reactions employing 2-unsubstituted ß-ketoesters were found to provide 5-methyl-1,2,3-triazoles, whereas 2-alkyl-substituted ß-ketoesters provided 5-hydroxy-1,2,3-triazoles (shown to be relatively acidic) in high yields and as single regioisomers. Several novel compounds were reported and characterized including long-chain 5-hydroxy-1,2,3-triazoles potentially bioisosteric to hydroxamic acids.

Enantioselective Synthesis of 3,4-Dihydropyran-2-ones via Phase-Transfer-Catalyzed Addition-Cyclization of Acetylacetone to Cinnamic Thioesters.

Herein, we present the first example of synthesis of 3,4-dihydropyran-2-ones from cinnamic thioesters via a stereoselective phase-transfer-catalyzed domino Michael-cyclization reaction with acetylacetone. The reaction proceeded under the catalysis of Cinchona-derived quaternary ammonium phenoxide that, in combination with inorganic bases, provided 3,4-dihydropyran-2-ones in yields of up to 93% and enantioselectivities of up to 88% enantiomeric excess.

Reaction of azides and enolisable aldehydes under the catalysis of organic bases and Cinchona based quaternary ammonium salts.

Herein we report a two-step sequence for the preparation of amides starting from azides and enolisable aldehydes. The reaction proceeded via the formation of triazoline intermediates that were converted into amides via Lewis acid catalysis. Preliminary studies on the preparation of triazolines under chiral phase transfer catalysis are also presented, demonstrating that enantioenriched amides could be prepared from achiral aldehydes in moderate to low enantioselectivity.