Copper-catalyzed aerobic cascade reaction for the conversion of 3,4-dihydropyrimidine-2(1H)-thiones to arylthiopyrimidines

Synthesis of Arylthiopyrimidines by Copper‐catalyzed Aerobic Oxidative C–S Cross‐coupling

“…Hinted by relative insensitivity of the C–S cross‐coupling to O 2 or air we envisioned a copper‐catalyzed cascade reaction, which combines the C–S cross‐coupling (Equation 1) with concomitant oxidative dehydrogenation (Equation 2) as shown in Scheme . Herein, we report the synthesis of fully substituted arylthiopyrimidines 4 from 3,4‐dihydropyrimidine‐2(1H)‐thiones (DHPMs) and aryl iodides under air, presumably via tautomerization, C–S cross‐coupling, and oxidative dehydrogenation (oxidation followed by elimination) (Equation 3) …”

“…At ≤ 70 °C, the reaction in PhCH 3 , THF, or dioxane did not proceed (entries 1–3). However, the detection of a trace amount of the desired product 9 in the case of DMF or NMP solvent (entries 4 and 5) led us to optimize the reaction conditions. Since higher temperature (100 °C) increased the reaction yield, we carried out the reaction with further elevation of temperature.…”

Transition-Metal-Catalyzed C–S, C–Se, and C–Te Bond Formations via Cross-Coupling and Atom-Economic Addition Reactions. Achievements and Challenges

“…421 The transformation of 3,4-dihydropyrimidine-2(1H)-thiones via tautomeric transformation, Ullmann coupling, oxidation, and elimination−aromatization leads to the formation of arylthiopyrimidines (Scheme 91 (2)). 422 Aminourea is a good surrogate for sulfur upon Cu(OAc) 2 catalysis in DMSO without ligand (Scheme 92, A). 423 Using dithiooxamide as a sulfur surrogate in the CuI-catalyzed reaction with PhI required significant optimization since it produced a mixture of diaryl sulfide and diaryl disulfide.…”

“…Arylthiopyrimidines are formed from 3,4-dihydropyrimidine-2­(1 H )-thiones in the CuI-catalyzed Ullmann-type process (Scheme (1)) . The transformation of 3,4-dihydropyrimidine-2­(1 H )-thiones via tautomeric transformation, Ullmann coupling, oxidation, and elimination–aromatization leads to the formation of arylthiopyrimidines (Scheme (2)) …”