Unusual mechanisms in Claisen rearrangements: an ionic fragmentation leading to a meta-selective rearrangementElectronic supplementary information (ESI) available: Experimental details, full characterization for new compounds, spectral data and computational details. CCDC 1540803, 1540804 and 1568395. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04736c

A mechanistic investigation of the acid-catalysed redox-neutral oxoarylation reaction of ynamides using electrospray ionisation mass-spectrometry (ESI-MS) and quantum chemical calculations (DFT and MP2) is presented. This study reveals the diversity of pathways and products available from an otherwise deceptively simple-looking, classical transformation: fragmentation, an unusual meta -arylation and competing α-carbonyl cation pathways are some of the alternatives unveiled by ESI-MS and mechanistic experiments. Detailed calculations explain the observed trends and rationalise the results. A mechanistic investigation of the acid-catalysed redox-neutral arylation of ynamides intertwining ESI-MS, DFT and experiments reveals diverse pathways available from an otherwise simple-looking transformation.