Photocyclization of N-Alkoxyalkylphthalimides with Favored δ-Hydrogen Abstraction : Syntheses of Oxazolo [4, 3-α] isoindoles and Oxazolo [4, 3-α]-isoindole-1-spiro-1'-cycloalkane Ring Systems

Photolysis of N-ω-alkoxyalkylphthalimides 1 gave the intramolecularly cyclized compounds, oxazolo [4, 3-a] isoindoles 2a-g, pyrrolo [2, 1-a] isoindoles 6i-j, oxazolo [4, 3-a]-isoindole-1-spiro-1'-cycloalkanes 2k-n and 3, 4-dihydro-2-benzazepine-1, 5 (2H)-dione 3, via δ-hydrogen abstraction and/or two-fold Norrish type II processes.