Photoinduced transformation of matrix-isolated methyl 2-pyrone-3-carboxylate into methyl 2-pyrone-5-carboxylate via intramolecular hydrogen shift in open-ring aldehyde-ketene

Key steps of the UV-induced conversion of methyl 2-pyrone-3-carboxylate (mp3c) into methyl 2-pyrone-5-carboxylate (mp5c).