General alkyl fluoride functionalization via short-lived carbocation-organozincate ion pairs

Abstract Fluorinated organic compounds are frequently used across the chemical and life sciences. Although a large, structurally diverse pool of alkyl fluorides is nowadays available, synthetic applications trail behind the widely accepted utility of other halides. We envisioned that C(sp2)-C(sp3) cross-coupling reactions of alkyl fluorides with fluorophilic organozinc compounds should be possible through a heterolytic mechanism that involves short-lived ion pairs and uses the stability of the Zn-F bond as the thermodynamic driving force. This would be mechanistically different from previously reported radical reactions and overcome long-standing limitations of organometallic cross-coupling methodology, including competing β-hydride elimination, homodimerization and hydrodefluorination. Here, we show a practical Csp3-F bond functionalization method that expands the currently restricted synthetic space of unactivated primary, secondary and tertiary C(sp3)-F bonds but also uses benzylic, propargylic and acyl fluorides. Many functional groups and sterically demanding substrates are tolerated, which allows practical carbon-carbon bond formation and late-stage functionalization

Radical Capture at Ni(II) Complexes: C-C, C-N, and C-O Bond Formation

The dinuclear b-diketiminato NiIItert-butoxide {[Me3NN]Ni}2(μ-OtBu)2 (2), synthesized from [Me3NN]Ni(2,4-lutidine) (1) and di-tert-butylperoxide, is a versatile precursor for the synthesis of a series of NiIIcomplexes [Me3NN]Ni-FG to illustrate C-C, C-N, and C-O bond formation at NiII via radicals. {[Me3NN]Ni}2(μ-OtBu)2 reacts with nitromethane, alkyl and aryl amines, acetophenone, benzamide, ammonia and phenols to deliver corresponding mono- or dinuclear [Me3NN]Ni-FG species (FG = O2NCH2, R-NH, ArNH, PhC(O)NH, PhC(O)CH2, NH2and OAr). Many of these NiII complexes are capable of capturing the benzylic radical PhCH(•)CH3 to deliver corresponding PhCH(FG)CH3 products featuring C-C, C-N or C-O bonds. DFT studies shed light on the mechanism of these transformations and suggest two competing pathways that depend on the nature of the functional groups. These radical capture reactions at [NiII]-FG complexes outline key C-C, C-N, and C-O bond forming steps and suggest new families of nickel radical relay catalysts.</p

Protection of the Benzoxaborole Moiety: Synthesis and Functionalization of Zwitterionic Benzoxaborole Complexes

The synthesis and utility of three benzoxaborole protecting groups are reported. These protecting groups improve organic solubility and allow otherwise incompatible reactions (oxidations, substitutions, and mild reductions) to be achieved in the presence of the benzoxaborole moiety. 3-(<i>N</i>,<i>N</i>-Dimethylamino)-1-propanol was determined to be useful in one-step sequences and is readily cleaved upon workup. Two other groups, <i>N</i>-methylsalicylidenimine and 2-[1-(methylimino)­ethyl]­phenol, are suitable for multistep syntheses. Deprotection with mild aqueous acid allows for chromatography-free isolation of the benzoxaborole in high yields