Fotoquímica de 1,2,3-Indanotriona em presença de Olefinas

Abstract

The photochemistry of 1,2,3-indanetrione (6) in the presence of olefins containing allylic hydrogen (2,4,4-trimethyl-1-pentene, cyclohexene, 2-methyl-2- butene, 2-methyl-1-butene and trans-piperylene), strongly electron donors (2,3- diphenyl-1,4-dioxene), weakly electron donors (acenaphthylene, cis-stilbene, transstilbene, 1,1-diphenylethylene and 4-methylstyrene) or electron acceptors (methyl fumarate and chalcone) was investigated. In the presence of olefins containing allylic hydrogen a dramatic preference for hydrogen abstraction was observed. Thus, 2,4,4-trimethyl-1-pentene leads to the formation of I; cyclohexene to II and the mixture 2-methyl-2-butene:2-methyl-1-butene (12:1) gives the products III, IV e V. The reaction with 2-methyl-2-butene and 2,3-diphenyl-1,4-dioxene gives [2+2] photocycloaddition products, VI e VIl, respectively. These products can be formed from the intermediacy of either 1,4-biradicals or radical ion pairs. The irradiation of 6 in the presence of olefins containing electon acceptors or weakly electron donors did not lead to any product formation. On the other hand, trans-piperylene reacted thermally by a Diels-Alder reaction, yielding the dihydropyran Vlll. Modern NMR techniques, mass spectrometry and infrared spectroscopy allowed the structural determination for products I-VlII. XV