Visible-Light-Promoted Desulfurative Alkylation of Alkyl Thianthrenium Salts with Activated Olefins
Xin Li, Weili Si, Zhanhui Liu, Haitao Qian, Tingxue Wang, Shengnan Leng, Jinwei Sun, Yan Jiao and Xuan Zhang*
*School of Chemistry and Materials Science, Institute of Advanced Materials and Flexible Electronics (IAMFE), Nanjing University of Information Science and Technology, 219 Ningliu Road, Nanjing 210044, China,
Email: xuanzhangnuist.edu.cn
X. Li, W. Si. Z. Liu, H. Qian, T. Wang, S. Leng, J. Sun, Y. Jiao, X. Zhang, Org. Lett., 2022, 24, 4070-4074.
DOI: 10.1021/acs.orglett.2c01525
Abstract
The formation of an alkyl thianthrenium salt/Hantzsch ester electron donor-acceptor complex enables a photocatalyst- and metal-free generation of an alkyl radical and a subsequent C(sp3)-C(sp3) bond formation with activated olefins. This protocol tolerates a broad range of functionality and can successfully be used in late-stage functionalization of pharmaceuticals.
see article for more examples
proposed mechanism
Details
The document discusses a novel, catalyst-free method for desulfurative alkylation of alkyl thianthrenium salts with activated olefins under visible-light irradiation. This approach generates alkyl radicals from primary alcohols using an electron donor-acceptor (EDA) complex formed between alkyl thianthrenium salts and Hantzsch ester. The method is significant for its mild conditions, broad substrate scope, and sustainability, avoiding the use of expensive photocatalysts and noble metals. The reaction was optimized using 456 nm light, N,N-dimethylacetamide (DMA) as the solvent, and Hantzsch ester as the electron donor, achieving up to 84% yield. The study also explored various activated olefins and alkyl thianthrenium salts, demonstrating good functional group tolerance and applicability in late-stage functionalization of pharmaceuticals. Mechanistic experiments confirmed the involvement of alkyl radicals, and the proposed mechanism involves single-electron transfer within the EDA complex under light irradiation. This method provides a green and efficient approach for C(sp3)−C(sp3) bond formation, utilizing abundant alcohols as alkylating reagents in organic synthesis.
Key Words
alkylation, Hantzsch ester, photochemistry
ID: J54-Y2022