Paper
4‐(Pentafluorosulfanyl)benzenediazonium Tetrafluoroborate: A Versatile Launch Pad for the Synthesis of Aromatic SF5 Compounds via Cross Coupling, Azo Coupling, Homocoupling, Dediazoniation, and Click Chemistry
Published Mar 1, 2014 · T. Okazaki, K. Laali, S. Bunge
European Journal of Organic Chemistry
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Abstract
The reagent 4-(pentafluorosulfanyl)benzenediazonium tetrafluoroborate (1) was synthesized and isolated as a stable salt for the first time; its application in a wide assortment of transformations was subsequently investigated. A series of novel SF5-bearing alkenes, alkynes, and biaryl derivatives were synthesized by employing Heck–Matsuda, Sonogashira, and Suzuki coupling protocols. Dediazoniation with TMSX (X = Hal; N3; and CN) and NH4SCN in [BMIM][BF4] as solvent furnished the corresponding p-SF5–C6H4X derivatives. The azide derivative p-SF5–C6H4N3 entered into click chemistry with phenylacetylenes to furnish the corresponding triazoles. The 4,4′-bis(pentafluorosulfanyl)biphenyl was synthesized by homo-coupling using Pd(OAc)2. The corresponding azo compounds were obtained through azo-coupling with reactive aromatic nucleophiles (1,3-dimethoxybenzene, 1,3,5-trimethoxybenzene, 1,2,4-trimethoxybenzene, aniline and phenol). Fluorodediazoniation in [BMIM][PF6] and [BMIM][BF4] selectively furnished the fluoro derivative p-SF5–C6H4F. Dediazoniation in [BMIM][NTf2] gave p-SF5–C6H4OS(O)(CF3)=NSO2CF3 as the major and p-SF5–C6H4-NTf2 as the minor products. Homolytic dediazoniation in MeCN/NaI gave the unsymmetrical biaryls p-SF5–C6H4-Ar (ArH = mesitylene and p-xylene) along with p-SF5–C6H4I. Analysis of the dediazoniation product mixtures indicated that dediazoniation of p-SF5–C6H4N2+ BF4– in low nucleophilicity, highly ionizing, solvents (TfOH, TFE, HFIP, TFAH) is mainly heterolytic, while in MeOH it is mainly homolytic. The isodesmic reaction p-SF5–C6H4+ + R-C6H5 → SF5–C6H5 + p-R-C6H4+ (with R = NO2, CF3, H) was gauged by DFT at various levels and by PCM.
The synthesized 4-(pentafluorosulfanyl)benzenediazonium tetrafluoroborate is a versatile tool for synthesizing aromatic SF5 compounds through various transformations.
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