Photoinduced Vicinal 1,2-Difunctionalization of Olefins for the Synthesis of Alkyl Sulfonamides

Abstract

Alkyl sulfonamides are an important class of bioactive molecules. Historical syntheses have relied on multistep sequences incorporating harsh reaction conditions. Photochemical methods have been limited to hydrosulfamoylation, installing only one substituent across an olefin. Herein, radical/polar crossover (RPC) is used to establish the first multicomponent 1,2-difunctionalization reaction incorporating a sulfonamide moiety and a second reaction partner. This protocol, exemplified on a range of olefins, utilizes various commercial sulfamoyl chlorides and organotrifluoroborates as coupling partners.

Azido-alkynylation of alkenes through radical-polar crossover

“…23 Potassium alkynyl-trifluoroborates were selected as nucleophilic alkynes as they had been previously employed for the trapping of similar carbocations. 20,21 The reaction was performed under photoredox conditions with BF 3 ·Et 2 O as additive to afford 3a in 74% yield after 1.5 hours at −20 °C (Table 1, entry 1).…”

“…Based on these experiments and literature precedents, a plausible mechanism could be proposed (Scheme 4C). 13 b ,20,21 Under blue light irradiation, excited state Ru(bpy) 3 2+* ( E 1/2 [Ru III /Ru II* ] = −0.86 V vs. SCE) 27 is capable of reducing Ts-ABZ ( E 1/2 red = −0.62 V vs. SCE) 28 generating the azide radical. Addition of the latter to alkene 1 would lead to carbon-centered radical I-1 ( E 1/2 ox = 0.37 V vs. SCE) 29 which can be oxidized by the previously formed Ru(bpy) 3+ ( E 1/2 [Ru III /Ru II ] = + 1.29 V vs. SCE) 27 regenerating the ground state photocatalyst.…”

Recent Developments in Selenylation and Thiolation of Alkenes via Three‐component Reactions

“…As described by the Molander group, [70] commercial sulfamoyl chlorides 52.1 could be applied in radical sulfonylation of alkenes. Under light irradiation, the photoexcitation of photocatalyst promoted the generation of S‐centered radicals 52.2 .…”

Photocatalytic C(sp2)–H sulfamoylation of enamides: regio- and stereoselective construction of (E)-β-sulfamoyl enamides

“…Based on the experimental results and literature reports, 5–9 a tentative mechanism was proposed as shown in Scheme 4. Upon visible-light irradiation, initially, the single electron transfer between the excited photocatalyst (4CzIPN*) and morpholine-4-sulfonyl chloride ( 2a ) gives dimethylsulfamoyl radical A , which adds to the β-position of the double bond in enamide 1a to generate benzyl radical intermediate B .…”