CF₃SO₂Na as a Bifunctional Reagent: Electrochemical Trifluoromethylation of Alkenes Accompanied by SO₂ Insertion to Access Trifluoromethylated Cyclic N‐Sulfonylimines

Abstract

An unprecedented electrochemical trifluoromethylation/SO 2 insertion/cyclization process has been achieved in an undivided cell in an atom-economic fashion. The protocol relies on tandem cyclization of N-cyanamide alkenes by using Langlois reagent as a source of both CF 3 and SO 2 under direct anodically oxidative conditions, in which two C À C bonds, two C À X bonds (N À S and S À C), and two rings were formed in a single operation. This transformation enabled efficient construction of various trifluoromethylated cyclic N-sulfonylimines from readily accessible materials.

The Shuttle of Sulfur Dioxide: Iridium/Copper‐Cocatalyzed Trifluoromethylfluorosulfonylation of Alkenes

“…X-ray crystallographic analysis unambiguously confirmed the structure of 3-35 (Please see the Supporting Information for an extended evaluation of reaction scope and limitations). A larger scale reaction was then conducted (3)(4)(5)(6)(7)(8)(9)(10)(11). Longer reaction time (48 h) has been found necessary and a non-negligible decrease (69% to 41%) in conversion was detected, indicating that further optimization may be required for larger scale.…”

“…[6] Based on the aforementioned unique profile of sulfonyl radical, we envisioned that using a proper trifluoromethyl sulfonyl radical precursor, both CF 3 and sulfonyl moiety can be introduced across the carbon-carbon double bonds through the in situ release and re-insertion of SO 2, i.e., the shuttle of SO 2 (Scheme 1C). [7] In this regard, several pioneering work has been reported by Liu, [8] Liao, [9] Akita, [10] Glorious [11] and Hong [12] group, respectively. However, this intriguing concept was still in its infancy.…”

Progress in Electrochemical Trifluoromethylation Reactions

“…Langlois reagent supplied CF 3 radical and SO 2 for this highly atom economical green reaction. [36] The protocol led to the efficient construction of various trifluoromethylated cyclic N-sulfonylimines from easily accessible starting materials though the yields and regioselectivity were moderate (Scheme 39) The method has also been used for difluoromethylation in a representative example with a low yield. Interestingly, the presence of the cyanamide moiety was very crucial for this tandem reaction as a substrate without the same failed to afford the expected product.…”

“…The reaction was carried out in an undivided cell using graphite anode and Pt plate cathode in the presence of Bu 4 NBF 4 as the electrolyte. Langlois reagent supplied CF 3 radical and SO 2 for this highly atom economical green reaction [36] . The protocol led to the efficient construction of various trifluoromethylated cyclic N‐sulfonylimines from easily accessible starting materials though the yields and regioselectivity were moderate (Scheme 39) The method has also been used for difluoromethylation in a representative example with a low yield.…”

Arylsulfonylacetate as Bifunctional Reagent for Photoredox Catalytic Alkylarylation of Alkynes

“…Bifunctional reagent, which employs a linker to bind two individual components, have recently been used for the rapid difunctionalization of unsaturated carbon-carbon bond [25][26][27][28][29][30][31][32][33] . Several brilliantly designed molecules have demonstrated powerful capacity as surrogates for both radical donors and acceptors, enabling the efficient difunctionalization of alkenes by Zhu [34][35][36][37][38] , Stephenson [39][40][41] , Nevado 42 and Hong [43][44][45] .…”