Perfluoroalkylation of Alkenes by Frustrated Lewis Pairs

Abstract

The activation of perfluoroalkyl iodides by the frustrated Lewis pair tris(pentafluorophenyl)borane and tri-tert-butylphosphine is described. By abstraction of both a fluorine and an iodine atom, an iodophosphonium fluoroborate salt is formed. In the presence of alkenes the corresponding iodoperfluoroalkylation products are generated regioselectively. First mechanistic investigations support a radical mechanism.

Visible Light-Induced Homolytic Cleavage of Perfluoroalkyl Iodides Mediated by Phosphines

“…In our studies addressing the Lewis-base-mediated iodoperfluoroalkylation of simple alkenes [40,42,43] we found that catalytic amounts of phosphines and phosphites effectively catalyze this process with complete regioselectivity upon irradiation with visible light (461 nm) (Scheme 1). Mechanistic investigations involving 19 F-NMR analysis suggested the intermediate formation of an EDA complex F(CF 2 ) n -I • • • PR 3 by halogen bond formation to the phosphorus atom [44,45].…”

Visible-light Promoted Atom Transfer Radical Addition−Elimination (ATRE) Reaction for the Synthesis of Fluoroalkylated Alkenes Using DMA as Electron-donor

“…Alkenes play a ubiquitous role in the realm of chemical synthesis due to their enriched reactivity and abundance, fluoroalkylation of carbon-carbon double bonds is an attractive method for accessing fluorine containing compounds. Since 1945, atom transfer radical addition (ATRA) has extensively been utilized for fluoroalkylation of alkenes [20][21][22][23][24][25][26][27][28][29]. However, the preparation of alkenes containing fluorinated functional groups via Heck-type reaction were less studied owning to the lack of efficient and general strategies [30][31][32].…”

Metal-Free Iodoperfluoroalkylation: Photocatalysis versus Frustrated Lewis Pair Catalysis

“…Transition-metal complexes 11 (based on ruthenium, iridium, copper) or organic dyes 12 (eosin Y, rose bengal, riboflavin) are nowadays popular catalysts for photochemical reactions. 9a,13 In 2016, we reported the frustrated Lewis pair (FLP)catalyzed iodoperfluoroalkylation of unsaturated hydrocarbons, 14 which was followed by further mechanistic studies in 2019 (Scheme 1). 15 For these transformations, we used the popular FLP consisting of tris(pentafluorophenyl)borane (2) (often abbreviated as BCF) and tri-tert-butylphosphine (1).…”

“…(1) (10 mol%) and B(C 6 F 5 ) 3 (2) (10 mol%) as catalysts 14,15 As this FLP-mediated iodoperfluoroalkylation showed some peculiar characteristics, we investigated the mechanism of this reaction more thoroughly. 15 While activation of the iodoperfluoroalkane by the Lewis base was indicated by NMR spectroscopy, kinetic studies revealed strong evidence for an additional photomediated process.…”

“…When we started our investigation on the FLP-catalyzed reaction, one of the first observations was the formation of [ t Bu 3 PI][FB(C 6 F 5 ) 3 ] (3) upon mixing t Bu 3 P and B(C 6 F 5 ) 3 with various perfluoroalkyl iodides (Scheme 3). 14 to learn more about supramolecular chemistry, physical-organic chemistry and molecular photoswitches. Since February 2018, he has been an independent research group leader at Heinrich-Heine-Universität Düsseldorf, Germany.…”