Site-Selective N-Dealkylation of 1,2,3-Triazolium Salts: A Metal-Free Route to 1,5-Substituted 1,2,3-Triazoles and Related Bistriazoles.

N3-Alkylation of 1-(pivaloyloxymethyl)-1,2,3-triazoles with alkyl triflates carrying latent "click" functionality, followed by a nucleophile-promoted N1-dealkylation of the resulting strongly electrophilic intermediate triazolium salts, provides an efficient route to 1,5-disubstituted 1,2,3-triazoles. The azide and alkyne groups incorporated by N-alkylation can be submitted to further copper-catalyzed azide-alkyne and Huisgen cycloadditions to provide bis(1,2,3-triazoles) with unprecedented 1,5/1,4 substitution patterns.

Cationic 1,2,3-Triazolium Alkynes: Components To Enhance 1,4-Regioselective Azide-Alkyne Cycloaddition Reactions.

4-Alkynyl-1,2,3-triazolium cations undergo thermal [3 + 2] cycloaddition reactions with azides roughly 50- to 100-fold faster than comparable noncharged alkynes. Further, the reaction is highly 1,4-regioselective (dr up to 99:1) owing to the selective stabilization of 1,4-TS transition states via conjugative π-acceptor assistance of the alkyne triazolium ring. The novel cationic triazolium alkynes also accelerate the CuAAC reaction to provide bis(1,2,3-triazoles) in an "ultrafast" way (<5 min).

Introducing axial chirality into mesoionic 4,4'-bis(1,2,3-triazole) dicarbenes.

Mesoionic 4,4'-bis(1,2,3-triazole-5,5'-diylidene) Rh(I) complexes having a C2 chiral 4,4'-axis were accessed from 3-alkyltriazolium salts in virtually complete de. Their structure and configurational integrity were assessed by NMR spectroscopy, X-ray crystallography, and chiral HPLC. Computational analysis of the MICs involved in the reaction suggested the formation of a highly stable and unprecedented cation-carbene intermediate species, which could be evidenced experimentally by cyclic voltammetry analysis.