Photochemistry of cyclic vicinal tricarbonyl compounds. Photochemical reaction of 1,2,3-Indanetrione with 2,3-dimethyl-2-butene: hydrogen abstraction and photocycloaddition

Abstract

A irradiação na região do ultravioleta de 1,2,3-indanotriona, em presença de 2,3-dimetil-2-buteno, em diclorometano, leva a uma mistura complexa de produtos formados a partir de reações de abstração de hidrogênio, fotocicloadição [2 π +2 π ] (reação de Paternò-Büchi) e fotocicloadição [4 π +2 π ]. A distribuição de produtos é dependente de fatores eletrônicos e estéricos, com estes últimos sendo os responsáveis pelo alto rendimento químico de formação do produto resultante da cicloadição fotoquímica [4 π +2 π ].UV irradiation of 1,2,3-indanetrione, in CH 2 Cl 2 , in the presence of 2,3-dimethyl-2-butene yields a complex mixture of products arising from hydrogen abstraction, [2 π +2 π ] photocycloaddition (Paternò-Büchi reaction), and [4 π +2 π ] photocycloaddition. The reaction is dependent on electronic and steric effects, with the later accounting for the high chemical yield observed for the formation of the dioxene-type product.

Ninhydrin as a building block in scaffold-linked chromophoric dyad construction

“…A single case of ninhydrin acting as a hetero-1,3-diene in which vicinal carbonyls act as the 4π-reagent with 2,3-dimethyl-2-butene by photochemical formal [4π+2π] addition takes place via 1,4-biradical. 11 The reaction of CE-1 with ninhydrin was conducted in dichloromethane at 140 o C in a sealed glass tube and produced two cycloadducts which were separated by radial chromatography. The major product was the 1:1-adduct 12 derived by attack at the central C=O dipolarophile (Scheme 2).…”

Laser flash photolysis study of the reaction of 1H-benz[f]indane-1,2,3-trione with olefins

“…Electron spin resonance and laser flash photolysis studies have provided clear-cut evidence of the intermediates involved in these mechanisms. 20 For example, photolysis of 2 (R=H) with electron-rich olefins containing allylic hydrogen, such as 2-methyl-2-butene 11 or 2,3-dimethyl-2-butene, 21 results in the formation of products by hydrogen abstraction and photocycloaddition. For mono-or disubstituted olefins containing allylic hydrogen and which are not so electron-rich, such as 2,4,4-trimethyl-1-pentene, 11 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene, 12 cyclohexene, 2-methyl-1-butene, 12 and 2,5-dimethyl-2,4-hexadiene, 12 the only products observed were those resulting from a hydrogen abstraction process.…”

“…However, previous studies on the reaction of cyclic vicinal tricarbonyl compounds with olefins show that electronic effects predominate over steric effects in the quenching process, with photocycloaddition products only starting to be formed when the ionization potential of the olefin approaches 8.7 eV. 4,11,21 Monoketones containing a naphthalene chromophore show triplet energy around 55-59 kJ mol -1 and display very low reactivity towards hydrogen abstraction or photocycloaddition reaction, 22 which is due to the , * character of their lowest triplet state. Recent spectroscopic work from Roy and co-workers 5 (see above) shows that 1H-benz[f]indane-1,2,3-trione (1) has a lowest singlet excited state containing 188 kJ mol -1 and showing n, * character.…”

Oxetane Synthesis through the Paternò-Büchi Reaction

“…1,2,3-Indanetrione reacted with 2,3-diphenyl-1,4-dioxene to give the oxetane on the carbonyl in the 2 position [53]. On the contrary, when the less electron rich 2,3-dimethyl-2-butene is used as alkene, a complex mixture of products is obtained [54]. The irradiation of 2,3-dihydrofuran with benzophenone in benzene gave adduct 8 (Scheme 5) [55,56,57].…”

“…The adduct was found also in the reaction between quinones and acenaphthylene [77]. Benzophenone can react also with a paracyclophane derivative 32 (Scheme 41) [54].…”