Photochemistry of allyloxybenzophenones: a pseudo-Paternò-Büchi rearrangement accompanied by hydrogen transfer induced 1,5-cyclization.
The solution photochemistry of the ortho allyloxy-substituted benzophenone has been investigated in detail. Product analysis revealed formation of a diastereomeric mixture of dihydrobenzofuran derivatives by cyclization via a short-lived intermediate 1,5-biradical and an unusual acetal by a pseudo-Paternò-Büchi rearrangement. The latter reaction pathway was supported by means of laser flash photolysis, where a long-lived intermediate with a maximum absorption band at 380 nm was observed. Besides, theoretical calculations (TD-DFT) of this UV-transient resulted in a band with maximum intensity at 390 nm showing a good correlation between experimental results and theoretical calculations. For comparison, the meta-substituent substrate was also investigated showing preferred triplet-triplet energy transfer.
Pérez-Ruiz
Raúl
R
Department of Chemistry, University of Cologne, Greinstrasse, 4, D-50939, Cologne, Germany.
Hinze
Olga
O
Neudörfl
Jörg-M
JM
Blunk
Dirk
D
Görner
Helmut
H
Griesbeck
Axel G
AG
D000042:Absorption; D001577:Benzophenones / Q000737:chemistry*; D003500:Cyclization; D004579:Electron Transport; D006859:Hydrogen / Q000737:chemistry*; D010777:Photochemistry; D010782:Photolysis; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D013997:Time Factors
D001577:Benzophenones; D006859:Hydrogen