1. Facile one-pot synthesis of 4,5-disubstituted 1,2,3-(NH)-triazoles through Sonogashira coupling/1,3-dipolar cycloaddition of acid chlorides, terminal acetylenes, and sodium azide
Jihui Li, Dong Wang, Yuanqing Zhang, Jiting Li, Baohua Chen Org Lett. 2009 Jul 16;11(14):3024-7. doi: 10.1021/ol901040d.
A novel and efficient way of synthesizing 4,5-disubstituted-1,2,3-(NH)-triazoles through palladium-catalyzed and ultrasonic promoted Sonogashira coupling/1,3-dipolar cycloaddition of acid chlorides, terminal acetylenes, and sodium azide in one pot is developed. The reaction scope is quite general, and the methodology can produce excellent yields. The regioselective 1,4,5-trisubstituted-1,2,3-(NH)-triazoles can be made easily from 4,5-disubstituted-1,2,3-(NH)-triazoles.
2. Polymer-supported 1,3-oxazolium-5-olates: synthesis of 1,2,4-triazoles
Swapan K Samanta, Jari Yli-Kauhaluoma J Comb Chem. 2005 Jan-Feb;7(1):142-6. doi: 10.1021/cc049905p.
A traceless synthesis of 3,5-disubstituted 1,2,4-triazoles has been developed on polymeric supports. The synthetic process utilizes immobilized mesoionic 1,3-oxazolium-5-olates (munchnones) as key intermediates in the 1,3-dipolar cycloaddition reaction. The initial step in the synthesis involves reductive alkylation of phenylglycine methyl esters with Ameba resin. The resulting immobilized amino acid esters were subsequently acylated with a variety of carboxylic acid chlorides and subjected to hydrolysis with 15% KOH to yield the polymer-bound carboxylic acids. Finally, the cycloaddition between diethyl diazocarboxylate or 4-phenyl-4H-1,2,4-triazoline-3,5-dione and the polymer-bound munchnones generated from the corresponding carboxylic acids afforded the polymer-bound 3,5-disubstituted 1,2,4-triazoles. Cleavage from the polymeric support using trifluoroacetic acid gave the desired 3,5-disubstituted 1,2,4-triazoles with excellent yield and high purity.
3. Traceless azido linker for the solid-phase synthesis of NH-1,2,3-triazoles via Cu-catalyzed azide-alkyne cycloaddition reactions
A Emil Cohrt, Jakob F Jensen, Thomas E Nielsen Org Lett. 2010 Dec 3;12(23):5414-7. doi: 10.1021/ol102209p. Epub 2010 Nov 4.
A broadly useful acid-labile traceless azido linker for the solid-phase synthesis of NH-1,2,3-triazoles is presented. A variety of alkynes were efficiently immobilized on a range of polymeric supports by Cu(I)-mediated azide-alkyne cycloadditions. Supported triazoles showed excellent compatibility with subsequent peptide chemistry. Release of pure material (typically >95%) from the solid support was readily achieved by treatment with aqueous TFA.
