Rearrangement of a 2-Methylenecylobutanone Derivative Triggered by Photoinduced Electron Transfer:

摘要

In a non-Kekule molecule system, replacing a carbon atom with an oxygen atom induces considerable changes in the geometry, multiplicity, electronic structure, and chemical reactivity of molecules, as exemplified by an oxyallyl, oxa analogue of trimethylenemethane. The oxatetramethyleneethane (3-methylenebutan-2-one-1,4-diyl) radical cation (OTME~(·+)) shown in Chart 1 is a radical cation variant of an unprecedented oxa analogue of tetramethyleneethane (TME). Expecting to generate OTME~(·+) intermediate 3~(·+), in this work, we studied photoinduced electron-transfer (PET) reactions of 2,2-bis(p-methoxyphenyl)-3,3-dimethyl-4-methylenecyclobutanone(1, Scheme 1, Ar = 4-MeOC_6H_4) and 2,2-bis(p-methoxyphenyl)-4-isopropylidenecyclobutanone (2). We now report a novel rearrangement of 1 to 2 via 3~(·+) together with ESR observations of 3~(·+).