O‑Benzyl Xanthate Esters under Ni/Photoredox Dual Catalysis: Selective Radical Generation and Csp3–Csp2 Cross-Coupling

• Published in: ACS catalysis Vol. 7; no. 6; pp. 3955 - 3959
• Main Authors: Vara, Brandon A, Patel, Niki R, Molander, Gary A
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02-06-2017
• Subjects: Letter; cross-coupling; alkyl xanthate esters; selective radical generation; metal-catalyzed reactions; carbon-centered radicals
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.7b00772

Alkyl xanthate esters are perhaps best known for their use in deoxygenation chemistry. However, their use in cross-coupling chemistry has not been productive, which is due, in part, to inadequate xanthate activation strategies. Herein, we report the use of O-benzyl xanthate esters, readily derived from alcohols, as radical pronucleophiles in Csp3–Csp2 cross-couplings under Ni/photoredox dual catalysis. Xanthate (C–O) cleavage is found to be reliant on photogenerated (sec-butyl) radical activators to form new carbon-centered radicals primed for nickel-catalyzed cross-couplings. Mechanistic experiments support the fact that the key radical components are formed independently, and relative rates are carefully orchestrated, such that no cross reactivity is observed.