Rhodium(III)-catalyzed C-H activation and indole synthesis with hydrazone as an auto-formed and auto-cleavable directing group.
An efficient, practical, and external-oxidant-free indole synthesis from readily available aryl hydrazines was developed, by using hydrazone as a directing group for Rh(III)-catalyzed C-H activation and alkyne annulation. The hydrazone group was formed by in situ condensation of hydrazines and C=O source, whereas its N-N bond was served as an internal oxidant, for which we termed it as an auto-formed and auto-cleavable directing group (DG(auto)). This method needs no step for pre-installation and post-cleavage of the directing group, making it a quite easily scalable approach to access unprotected indoles with high step economy. The DG(auto) strategy was also applicable for isoquinoline synthesis. In addition, synthetic utilities of this chemistry for rapid assembly of π-extended nitrogen-doped polyheterocycles and bioactive molecules were demonstrated.
Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084 (P.R. China).
Liyao
L
Zheng
Ruimao
R
Hua
D002384:Catalysis; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006835:Hydrazones / Q000737:chemistry*; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry*; D007546:Isoquinolines / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D012238:Rhodium / Q000737:chemistry*
D006571:Heterocyclic Compounds; D006835:Hydrazones; D007211:Indoles; D007546:Isoquinolines; D012238:Rhodium
CH activation; NN cleavage; hydrazones; indoles; rhodium catalysis