Highly Diastereoselective Synthesis of γ-Lactams Enabled by Photoinduced Deaminative [3 + 2] Annulation Reaction
Chengcheng Shi, Lin Guo, Han Gao, Mengqi Luo, Chao Yang* and Wujiong Xia*
*State Key Lab of Urban Water Resource and Environment, School of Science, Harbin Institute of Technology, Shenzhen, Guangdong 518055, China,
Email: xyyang
hit.edu.cn, xiawjhit.edu.cn
C. Shi, L. Guo, H. Gao, M. Luo, C. Yang, W. Xia, Org. Lett., 2022, 24, 4365-4370.
DOI: 10.1021/acs.orglett.2c01565
see article for more reactions
Abstract
A photoinitiated deaminative [3 + 2] annulation reaction of N-aminopyridinium salts with alkenes provides functionalized γ-lactams. This transformation shows good functional group tolerance as well as excellent diastereoselectivity.
see article for more examples
proposed mechanism
Details
The document describes a highly diastereoselective synthesis of γ-lactams via a photoinduced deaminative [3 + 2] annulation reaction. This method involves the reaction of N-aminopyridinium salts with alkenes under visible-light irradiation, facilitated by a photocatalyst, fac-Ir(ppy)3. The process generates amidyl radicals through N−N bond cleavage via a single-electron transfer (SET) process. These radicals add to the double bond of alkenes, followed by a radical-mediated annulation to form γ-lactams. The method shows good functional group tolerance and excellent diastereoselectivity. Optimization of reaction conditions revealed that a mixture of DMSO and CH3CN (1:1) as the solvent and Na2HPO4 as an additive provided the best yields. The scope of the reaction was explored with various N-aminopyridinium salts and alkenes, yielding γ-lactams with high diastereoselectivity. Mechanistic studies indicated a radical pathway, with the amidyl radical intermediate playing a crucial role. This method offers a new approach to synthesizing γ-lactams under mild conditions, potentially useful for creating complex molecular architectures and drug-related molecules. The research was supported by various Chinese scientific foundations and institutions.
Key Words
γ-lactams, photochemistry
ID: J54-Y2022
