Metal-Free, Acid/Phosphine-Induced Regioselective Thiolation of p-Quinone Methides with Sodium Aryl/Alkyl Sulfinates

Abstract

A simple and efficient method for the regioselective thiolation of p-quinone methides with sodium aryl/alkyl sulfinates has been established using an acid/phosphine-induced radical route under transition-metal-free conditions. A broad range of sodium aryl/alkyl sulfinates and p-quinone methides (p-QMs) are compatible for the reaction, giving the expected products with good to excellent yields. Control experiments were also performed to gain insights into the generation mechanism of thiyl radicals and hydrogen-atom transfer process. This protocol provides a safe and feasible way for the formation of carbon−sulfur bonds.

Nucleophilic Reactivities of Thiophenolates

“…The aryl-substituted p -quinone methides ( p QMs) have repeatedly been used as reference electrophiles for reactions with anionic nucleophiles in DMSO, a polar, non hydrogen bond donor solvent . We intended, therefore, to follow the kinetics of the 1,6-additions , of the X-substituted ArS – 1a – j (in DMSO) to the p QMs 2a – f whose Mayr electrophilicity parameters E are known (Chart ).…”

Rongalite as a Sulfone Source: Sulfonylation of para‐Quinone Methides and Alkyl/allyl Halides

“…Analogously, by using 3‐methyl‐1‐phenyl‐pyrazolone (and NBS) with 4 aa afforded bis‐spiro compound 6 in a diastereomerically enriched form (≥9 : 1) in 66% yield [15] . Further, reduction of the S=O bonds (in 4 ka ) was performed using sulfuric acid and PPh 3 to provide aryl thioether 7 in 67% yield [16] . Additionally, product 4 na was converted to compound 8 by using Pd 2 (dba) 3 and phosphoramidite (5 mol% each) ligands in 74% yield.…”

“…[15] Further, reduction of the S=O bonds (in 4 ka) was performed using sulfuric acid and PPh 3 to provide aryl thioether 7 in 67% yield. [16] Additionally, product 4 na was converted to compound 8 by using Pd 2 (dba) 3 and phosphoramidite (5 mol% each) ligands in 74% yield.…”

Multicomponent Synthesis of S-Benzyl Dithiocarbamates from para-Quinone Methides and Their Biological Evaluation for the Treatment of Alzheimer’s Disease

“…In 1 H NMR, the CDCl 3 peak is graduated to 7.26 ppm, and it is 77.00 ppm for 13C NMR spectra. Starting materials ( p -QMs) were prepared using the literature procedures. , Solvents and chemicals were purchased from commercial sources and used without further purification.…”