摘要
Different from the established trans-endo-selective cyclization of alkyne-tethered electrophiles that involve an E/Z isomerization process,herein,the authors present a novel strategy to allow trans-exo-selective arylative cyclization of 1,6-enynes.Through initiation of rhodium(III)-catalyzed C-H activation,a diverse range of N-heterocyclic directing groups,including pyridine,pyrazole,imidazo[1,2-a]pyridine,benzoxazole,benzothiazole,and purine,was feasible for the cascade transformation,exhibiting high efficiency(up to 92%yield),broad substrate scope,and excellent functional group compatibility.Moreover,the modification of natural products and pharmaceutical compounds was also demonstrated to showcase its synthetic utility.Based on density functional theory(DFT)calculations,a key three-membered ring intermediate through the insertion relay,rather than the direct E/Z isomerization of alkenyl rhodium species,controlled the stereochemical outcome for this trans-exo-selective cyclization.The subsequent ring-opening protonation of the more favored rotamer led to exclusive trans-exo-selectivity.
基金
Financial support was generously provided by the National Natural Science Foundation of China(nos.21871184,21871284,21702182,and 21873081),the Shanghai Municipal Education Commission(no.2019-01-07-00-10-E00072),the Science and Technology Commission of Shanghai Municipality(no.18401933500),the Strategic Priority Research Program of the Chinese Academy of Sciences(no.XDB 20020100),the Key Research Program of Frontier Science(no.QYZDYSSW-SLH026),the Fundamental Research Funds for the Central Universities(no.2019QNA3009),and the China Postdoctoral Science Foundation(no.2018M640546).Calculations were performed on the high-performance computing system at the Department of Chemistry,Zhejiang University.The authors thank Jie Sun(Shanghai Institute of Organic Chemistry)for X-ray crystallographic analysis.
