Are Vinyl Cations Finally Coming of Age?

Abstract

C(sp 3 )ÀHf unctionalization ·c arbene analogues ·carbocations ·C À Hinsertion ·v inyl cations Carbocations are important reactive intermediates for Highlights Highlights

Stereoselective Synthesis of (Z)‐β‐Enamido Triflates and Fluorosulfonates from N‐Fluoroalkylated Triazoles

“…[7][8][9][10][11] Recently,t he synthetic community has been witnessing ar enewed interest in transformations involving vinyl cations. [12,13] Despite the valuables ynthetica pplicationso fv inyl triflates,they possess some drawbacks that limit their industrial application.F or instance, they are commonly liquids, sensitive to hydrolysis and their preparation requires expensiver eagents. [14] Vinyl triflates are usually prepared from carbonyl compounds either by trapping the respective enolate with a triflating agent [15,16] or by treating the carbonylc ompound with triflic anhydride in the presence of ab ulky base.…”

Stereodivergent Alkyne Hydrofluorination Using a Simple Practical Reagent

“…A range of primary, secondary, cyclic or acyclic alkyl-substituted alkynes could be employed in the hydrofluorination to furnish respective products again with moderate to good yields and excellent regio-and stereoselectivities (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39). Remarkably, substrates with potentially sensitive functional groups including a primary chloro, a carboxymethyl, a cyano, a pyridyl, and a phthalimido group also delivered the monofluoroalkene products, highlighting the mildness and good functional group tolerance of this protocol (40)(41)(42)(43)(44)(45)(46). This scalability of the procedure was demonstrated by the gram-scale preparation of 44, which proceeded with unchanged regio-and stereoselectivities and only a slightly reduced yield (1.65 g, 64%).…”

“…Previously, vinyl cations have been generated through several approaches 36 , including metal catalysis 37,38 , photochemical processes 39 , ionization of vinyl iodonium 40 and diazonium species 41 , (pseudo)halide abstraction with Lewis acids 42,43 , as well as protonation of alkynes with strong Brønsted acid 44,45 . In spite of the challenging and specialized conditions that are often required for their generation, the versatility of this intermediate has led to a recent renaissance in their synthetic applications 46 . In this context, the hydrofluorination conditions reported here represent an unprecedentedly mild, stereocontrolled, and functional group compatible approach for utilizing these intermediates.…”

Stereodivergent Alkyne Hydrofluorination Using Protic Tetrafluoroborates as Tunable Reagents

“…[31,32] Despite the challenging and specialized reaction conditions that are often required for their generation, the versatility of this intermediate has led to ar ecent renaissance in their synthetic applications. [33] In this context, the hydrofluorination conditions reported here represent an unprecedentedly mild, stereocontrolled, and functional-group compatible approach for utilizing these intermediates.…”