Diastereoselective Synthesis of Chiral (Triazolinylidene)rhodium Complexes Containing an Axis of Chirality

An easy and direct method for the synthesis of 1,2,4-triazole derivatives through carboxylic acids and hydrazinophthalazine

“…1,2 Enders and co-workers developed the synthesis of triazole salts by amine reaction with oxadiazolium salt by condensation of N, N´-diformylhydrazine. 3 Triazole rings are typically synthesized by a process that represents a dehydrated condensation between hydrazides and nitrile derivatives. These procedures are carried out at high temperatures and depend on a stage derived from nitrile and a subsequent stage for the synthesis of acylamidrazone intermediate prior cyclization.…”

Synthesis, structure and electronic properties of N-dialkylamino- and N-alkoxy-1,2,4-triazol-3-ylidene ligands

“…2) show the expected square-planar geometry around the rhodium atom with the carbene ligand perpendicular to this plane. The carbene carbon-rhodium bond lengths of 201.6 and 201.1 pm, respectively, are similar to those observed in other NHC-rhodium(I) complexes [17]. In 14d, the 2,5-dimethylpyrrol-1-yl substituent on the 1,2,4-triazol-3-ylidene ring also adopts a relative perpendicular orientation that minimizes steric interactions.…”

NHC ligands versus cyclopentadienyls and phosphines as spectator ligands in organometallic catalysis

“…For example, with phase-transfer catalysts like tetrabutylammonium bromide it is possible to generate NHC complexes with a milder bases such as aqueous sodium hydroxide solution -benzimidazolium bromides and (Me 2 S)AuCl react in CH 2 Cl 2 /H 2 O at room temperature to give [(NHC) 2 Au]Br [19]. For the more acidic triazolium salts, triethylamine in THF can be used as the external base for deprotonation, but in cases where deprotonation takes place in the presence of a metal complex or salt, the NHC may bind to the metal in an agostic mode or even oxidatively add to the metal first, so that the deprotonation is greatly facilitated [20]. For imidazolines, the alcohol adduct is a useful precursor [8b].…”