Synthesis of Cyclobutenes by the Novel Photochemical Ring Contraction of 4-Substituted 2-Amino-3,5-dicyao-6-phenyl-4H-pyrans

Article abstract of DOI:10.1021/jo00274a021

4-Substituted 2-amino-3,5-dicyano-6-phenyl-4H-pyrans undergo a novel photochemical ring contraction to cyclobutenes from the triplet state.For example, irradiation of a solution of 2-amino-3,5-dicyano-6-phenyl-4H-pyran-4-spirocyclopentane (9a) in methylen