Scalable, Chemoselective Nickel Electrocatalytic Sulfinylation of Aryl Halides with SO2

Abstract

Simple access to aryl sulfinates from aryl iodides and bromides is reported using an inexpensive Ni-electrocatalytic protocol. The reaction exhibits a broad scope, uses stock solution of simple SO₂ as sulfur source, and can be scaled up in batch and recycle flow settings. The limitations of this reaction are clearly shown and put into context by benchmarking with state-of-the-art Pd-based methods.

Keywords: Chemoselectivity; Electrochemistry; Fluoride; Nickel; Sulfur.

Figure 1

A) Aryl sulfinates as the gateway to various S^IV and S^VI functional groups. B) Established metal‐catalyzed sulfinylation for the formation of various sulfonyl‐containing compounds. C) Recent advancement of Ni catalysis enabled by electrochemistry.

Figure 2

A) One‐pot derivatization of aryl sulfinate 38 into various sulfonyl functional groups. B) Scale‐up reaction in I) gram scale using ElectraSyn 2.0 setup, II) multigram scale in capped reagent bottle, and III) decagram scale in recycle flow system. [a] TBAF (4 equiv), NCS (4 equiv), rt, 0.5 h, then aq. KHF₂ (4 equiv), rt, 2 h. [b] 4‐MeC₆H₄CH₂Br (2 equiv), rt, 1 h. [c] Morpholine (3 equiv), NCS (4 equiv), rt, 1 h. [d] Refer to Table 2 and Supporting Information for comparison conditions, followed by the addition of aq. KHF₂ (4 equiv).

Figure 3

A) Cyclic voltammograms of SO₂ alone (grey dotted line), SO₂ with DIPEA (blue line), Ni(dtbpy)₃Br₂ (red line), NMPI (green line), and 2‐iodoanisole (1) (yellow line), which were taken with n‐Bu₄NBF₄ [0.1 M] as electrolyte in CH₃CN, glassy carbon working electrode, Ag/AgCl as reference, at 298 K. Scan rate=200 mV s⁻¹. B) Reaction profile of the e‐sulfinylation of 2‐iodoanisole (1) over a course of 8 F/mol, with the amount of aryl iodide 1 (yellow squares), sulfinate product 2 (red dots), anisole (blue triangles), and NMPI (green diamonds) determined by HPLC using 4,4′‐di‐tert‐butylbiphenyl as internal standard. C) Proposed mechanism for e‐sulfinylation.