4 research outputs found
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
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