Photochemical cyclization of o-methylphenyl 1,3-diketones

Abstract

The photochemistry of five 1,3-dicarbonyl compounds, substituted at the 1-position with an o-methylphenyl group, has been investigated. Compounds 5a-c cyclize upon irradiation to give tetralones 6a and 6c and octahydroanthracene derivative 6b, respectively. Compounds 5d and 5e do not form similar photoproducts. Diketone 5c is the most efficient in this reaction, indicating that the reaction probably occurs via the keto tautomer. A mechanism involving initial y-hydrogen abstraction followed by interception of the resulting 1,Cbiradical by the second carbonyl group is proposed.

Acid-Catalyzed Reactions of Aromatic Aldehydes with Ethyl Diazoacetate: An Investigation on the Synthesis of 3-Hydroxy-2-arylacrylic Acid Ethyl Esters

“…At this temperature the yield of the 3-hydroxyacrylate is significantly improved (entries 9,15,20,and 30,Table 4). In some cases, the only product isolated from the reaction was the desired 3-hydroxyacrylate, whereas 1 is ineffective as a catalyst at this temperature (entries 4 and 17, Table 4) due to slow dissociation of the THF ligand from 1.…”

Antifungal Metabolite with a New Carbon Skeleton from Keissleriella sp. YS4108, a Marine Filamentous Fungus

“…In the 1 H-NMR spectrum of 1, a couple of broadened aromatic proton singlets at d 6.17 and 6.12, together with two pairs of mutually coupling one-proton doublets at d 3.06 (J = 16.9 Hz) and 2.94 (J = 16.9 Hz), and 2.71 (J = 17.1 Hz) and 2.88 (J = 17.1 Hz), suggested that it was a 3,4-dihydro-1-naphthalenone derivative carrying presumably a 3-hydroxy group. This assumption was substantiated by a set of carbon resonance lines in its 13 C-NMR spectrum at d 108.7 (CH), 163.9 (C), 101.6 (CH), 165.2 (C), 110.4 (C), 200.3 (C), 49.8 (CH 2 ), 72.5 (C), 41.8 (CH 2 ) and 143.7 (C) [7], [8]. Further reinforcement of the proposal was provided by extensive 2D NMR spectroscopic analyses (COSY, HMBC, HMQC and NO-SEY) allowing the exact assignment of all proton and carbon signals.…”

Solvent Dependent Photochemical Reactions of 3-(2-Alkylphenyl)-2,2-dimethyl-3-oxopropanoates and Their Related Compounds

“…Irradiation of Methyl 3-(2-Alkylphenyl)-2,2-dimethyl-3-oxopropanoates: Effect of Bulkiness of Ortho Alkyl Substituents on Photoreactivities. Irradiation of methyl 3- o -tolyl-2,2-dimethyl-3-oxopropanoate ( 4a ) in methanol with a high-pressure mercury lamp through a Pyrex filter gave the oxonaphthalenone 9a (23%) as the major product together with the benzocyclobutenol 10a (9%) at 94% conversion, in contrast to Hornback's report that naphthalenone derivatives were obtained exclusively in the photochemical reactions of o -tolyl 1,3-diketones in methanol . The yields of photoproducts 9 and 10 are given in Table .…”

“…Contrary to the extensively studied o -alkylphenyl ketones, the photochemistry of o -alkylphenyl 1,3-diketones is still less explored . Irradiation of some o -alkylphenyl 1,3-diketones in methanol gave naphthalenone derivatives exclusively instead of benzocyclobutenols . However, irradiation of o -alkylphenyl β-keto esters having no substituents on the alpha position did not afford any isolable photoproducts, though they produce dienols upon irradiation, as evidenced by deuterium incorporation …”