Synthesis and nucleophilic properties of 4-aryl-5-triphenylphosphonium-1,2,3-triazole ylides or 4-aryl-1,2,3-triazol-5-yltriphenylphosphoranes

Abstract

The title heterocyclic compounds have been prepared by the addition of sodium azide to arylethynyltriphenylphosphonium halides in dimethylformamide. In hot basic aqueous solution these ylides hydrolyze to give 4-aryltriazole anion and triphenylphosphine oxide. More notably, the ylides are nucleophilic: displacements of halide from ethyl iodide, benzoyl chloride, ethyl chloroacetate, ethyl /3-chloropropionate, 2,4-dinitrobromobenzene, and mercuric chloride and Michael additions to ethyl propiolate have been realized. In all of these examples, the point of attack is exclusively at the 2-nitrogen of the ylide. CNDO calculations on the hypothetical unsubstituted l,2,3-triazol-4-ylphosphorane indicate a charge density in the molecule which is consistent with a mesoionic or ylide structure.

A phosphine-mediated stereocontrolled synthesis of Z-enediynes by a vicinal dialkynylation of ethynylphosphonium salts

“…3. The sequence is initiated by b-addition of the lithioacetylide reagent 11 to the ethynylphosphonium cation 12 to give a vinylidene phosphorane 13 intermediate 6, which by virtue of its bent geometry 14 may exist as either E or Z configurational isomers. In contrast to vinylidene ylides of more electronegative elements, the poor nucleofugality of the triarylphosphine moiety implicates vinylidene phosphorane 6 as a persistent intermediate in solution, assuring equilibration of the geometrical isomers to the less hindered Z configuration.…”

Alkynylcarbenium ions and related unsaturated cations

“…A method for the synthesis of a new family of heterocyclic ylides 525 based on reactions of alkynylphosphonium salts with sodium azide has been developed. 250 Phenylethynylpyridines 528 have been obtained by the reaction of the salt 516a with pyridine N-oxides. 255 The use of alkynylphosphonium salts in the synthesis of heterocycles comprising the addition of nucleophiles to a triple C:C bond and subsequent cyclisation with the removal of the activating triphenylphosphine fragment has been demonstrated 35 in relation to reactions of the salt 516a.…”

Synthesis and antiinflammatory activity of some 1,2,3- and 1,2,4-triazolepropionic acids

“…The less polar, front-running isomer was recrystallized from aqueous MeOH to yield 1.8 g of the triazole-2-propionic acid 7 as white silvery platelets, mp 143 °C. 13 Anal. (CnHnNaOa) C, H. The NMR spectra (C5D6N) displayed the triazole proton at 489 Hz and the phenyl protons as two multiplets, one of 2 H centered at 478 Hz and one of 3 H centered on 445 Hz.…”