Catalytic synthesis of 1H-2-benzoxocins; Cobalt(III)-carbene radical approach to 8-membered heterocyclic enol ethers

01 July 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The metallo-radical activation of ortho-allylcarbonyl-aryl N-arylsulfonylhydrazones with the paramagnetic cobalt(II) porphyrin catalyst [Co^II(TPP)] (TPP = tetraphenylporphyrin) provides an efficient and powerful method for the synthesis of novel 8-membered heterocyclic enol ethers. The synthetic protocol is versatile, practical and enables the synthesis of a wide range of unique 1H-2-benzoxocins in high yields. The catalytic cyclization reactions proceed with excellent chemoselectivities, have a high functional group tolerance, and provide several opportunities for the synthesis of new bioactive compounds. The reactions are shown to proceed via cobalt(III)-carbene radical intermediates, which are in-volved in intramolecular hydrogen transfer (HAT) from the allylic position to the carbene radical, followed by a near barrierless radical rebound step in the coordination sphere of cobalt. The proposed mechanism is supported by experi-mental observations, density functional theory (DFT) calculations and spin trapping experiments.


carbene radical
8-membered ring ether

Supplementary materials

Supporting Information.
Experiment details; synthesis procedures; relevant NMR, EPR, HRMS, XRD data; DFT study (PDF);


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