Photosensitized hydrogen abstraction from 2-alkyl-1, 3-dioxolanes by triplet benzophenone gives the corresponding 1, 3-dioxolan-2-yl radicals and these are trapped by α, β-unsatured ketones yielding monoprotected 1, 4-diketones. With open chain ketones (3-buten-2-one and 4-penten-3-one) the yields are low and competitive pathways in part consume the radicals. With cyclic enones however, yields are good as tested with cyclopentenone, ...
