Recapitula=ng the sequence of scale-up, product isola=on, and characteriza=on revealed that the reac=on of iTCO with Pyr2 (1) yields predominantly the cyclized elimina=on product Pi (Fig. ), which underwent very slow oxida=on to Pia (<30% aUer a week). Worth poin=ng out, Pi has the same m/z value as a respec=ve Patype isomer, which would have been the expected product based on the conven=onal mechanism-another case underscoring the importance of elucida=ng product structures.