A number of 3-hydroxy substituted indolic nitrones were found to quantitatively photorearrange to (2-benzoylamino)phenyl ketones upon UV-A irradiation. EPR-Spin Trapping experiments suggest that the process, which is believed to proceed via the formation of an oxaziridine, follows a homolytic pathway. Although DFT calculations do not allow to totally exclude alternative routes involving singlet intermediates, they do provide support to the proposed homolytic mechanism, which would be driven by a 1,5-hydrogen transfer subsequent to the oxaziridine ring opening. When this hydrogen transfer was made impossible by methylation of the 3-OH group, a benzoxazine was isolated as the sole reaction product.
RADICAL INTERMEDIATES IN THE PHOTOREARRANGEMENT OF 3-HYDROXYINDOLIC NITRONES / Alberti, A., Astolfi, P., Carloni, P., Döpp, D., Greci, L., Rizzoli, C., Stipa, P.. - In: TETRAHEDRON. - ISSN 0040-4020. - 67:(2011), pp. 6889-6894. [10.1016/j.tet.2011.06.094]
RADICAL INTERMEDIATES IN THE PHOTOREARRANGEMENT OF 3-HYDROXYINDOLIC NITRONES
ASTOLFI, PAOLA;CARLONI, PATRICIA;L. Greci
;STIPA, Pierluigi
2011-01-01
Abstract
A number of 3-hydroxy substituted indolic nitrones were found to quantitatively photorearrange to (2-benzoylamino)phenyl ketones upon UV-A irradiation. EPR-Spin Trapping experiments suggest that the process, which is believed to proceed via the formation of an oxaziridine, follows a homolytic pathway. Although DFT calculations do not allow to totally exclude alternative routes involving singlet intermediates, they do provide support to the proposed homolytic mechanism, which would be driven by a 1,5-hydrogen transfer subsequent to the oxaziridine ring opening. When this hydrogen transfer was made impossible by methylation of the 3-OH group, a benzoxazine was isolated as the sole reaction product.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
