Synthesis of Tetrahydroazepines through Silyl Aza-Prins Cyclization Mediated by Iron(III) Salts

A new methodology for the synthesis of seven-membered unsaturated azacycles (tetrahydroazepines) was developed. It is based on the powerful aza-Prins cyclization in combination with the Peterson-type elimination reaction. In a single reaction step, a C–N, C–C bond and an endocyclic double bond are formed. Under mild reaction conditions and using iron(III) salts as sustainable catalysts, tetrahydroazepines with different degrees of substitution are obtained directly and efficiently. DFT calculations supported the proposed mechanism.Grants (PGC2018-094503-B-C22 to J.I.P. and PID2019-106184GB-I00 and RED2018-102387-T to I.F.) funded by MCIN/AEI/10.13039/50100011033 and, as appropriate, by “ERDF A way of making Europe”, by the “European Union” or by the “European Union NextGeneration EU/PRTR”. V.S. thanks the Spanish MCIU for an FPU fellowship. The manuscript was edited by Guido Jones, also funded by the Cabildo de Tenerife under the same TFinnova support.Peer reviewe