Scope and Mechanistic Insights into the Use of Tetradecyl(trihexyl)phosphonium Bistriflimide: A Remarkably Selective Ionic Liquid Solvent for Substitution Reactions

Abstract

A survey of substitution reactions conducted in a phosphonium bistriflimide ionic liquid is presented. The results demonstrate high selectivity favoring substitution over typically competitive elimination and solvolytic processes even when challenging secondary and tertiary electrophiles are employed. The first reports of Kornblum substitution reactions in an ionic liquid are described that proceed with very high chemoselectivity in favor of nitro over nitroso products and elimination side products. The structure-reactivity study indicates that these reactions proceed through a narrow spectrum of pathways ranging from straight S(N)2 to a preassociation pathway along a saddle point that approaches the S(N)1 limit. The barrier to the formation of dissociated carbocations is attributed to the structural features of this ionic liquid that favor intervention of the associated nucleophile over dissociation, also preventing cross over to E1 processes. The lack of any basic entity in the phosphonium bistriflimide ionic liquid appears to prevent any potential base-mediated elimination reactions, which makes this a highly selective medium for use in general substitution reactions.

Easy and direct conversion of tosylates and mesylates into nitroalkanes

“…General Information: Compounds 2a [38], 2b [24], 2c [15], 2d [25], 2e [39], 2f [24], 2g [40], 2h [40], 2i [24] and 2j [41] are known, and their spectroscopic data are in agreement with those reported in the literature. Compounds 1 were synthesized by Ghosh and Nicponski’s methodology [42].…”

Identification, Synthesis, and Biological Evaluation of the Metabolites of 3-Amino-6-(3′-aminopropyl)-5H-indeno[1,2-c]isoquinoline-5,11-(6H)dione (AM6–36), a Promising Rexinoid Lead Compound for the Development of Cancer Chemotherapeutic and Chemopreventive Agents

“…Briefly, the nitro group of precursor 24 36 was reduced with iron and ammonium chloride. The solution was neutralized with sodium hydroxide, 37 the intermediate acetylated, 38 and the mixture treated again with sodium hydroxide to afford the desired metabolite 9 .…”

Molecular features contributing to the lower viscosity of phosphonium ionic liquids compared to their ammonium analogues

“…25,27,[45][46][47][48] In recent years, phosphonium based ILs have become an intensely investigated subgroup of ILs. [49][50][51][52][53][54][55][56][57] One superior property of phosphonium based ILs compared to ammonium analogues is their improved stability. 53,[58][59][60] Additionally, phosphonium based ionic liquids typically have a lower viscosity compared to their ammonium analogues 57,[59][60][61][62][63][64][65][66] , see table 1 for selected examples.…”