- A switchable oxidation process leading to two various versatile pharmaceutical intermediates
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An efficient high-yielding and environmentally benign switchable oxidation process that can selectively produce two different versatile synthetic intermediates is disclosed. One of the two intermediates, 2,3-dimethoxy-5- methylcyclohexa-2,5-diene-1,4-dione (coenzyme Q0), is obtained by means of a telescoped two-step synthetic protocol that in the first step involves treatment of the substrate (1,2,3-trimethoxy-5-methylbenzene) with hydrogen peroxide in acetic acid with p-toluene sulphonic acid present as a Bronsted acid catalyst, succeeded by a telescoped second step that entails treatment with fuming nitric acid to achieve the target molecule in an excellent isolated yield (88%). If the substrate is treated directly with nitric acid (65%) in glacial acetic acid two different products can be obtained, namely acetic acid 3,4,5-trimethoxybenzyl ester in a superb isolated yield (93%) or, under slightly altered reaction conditions, 1,2,3-trimethoxy-5- (nitromethyl)benzene in a moderate to low yield (35%) and low selectivity. The two pathways leading to the two different products in the nitric acid oxidation protocol were investigated by means of DFT calculations as an aid to elaborate a proposal for the reaction mechanism.
- Occhipinti, Giovanni,Liguori, Lucia,Tsoukala, Anna,Bjorsvik, Hans-Rene
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supporting information; experimental part
p. 1379 - 1384
(2011/09/20)
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- Photochemical nitration by tetranitromethane. Part XXXVII. Adduct formation and the regiochemistry of attack of trinitromethanide ion on radical cations in the photochemical reactions of 2-methyl-, 2,3-dimethyl- and 2,4-Dimethylanisoles
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The photolysis of the charge transfer (CT) complex of tetranitromethane and 2-methylanisole 2 in dichloromethane at 20 °C gives the epimeric 1-methoxy-6-methyl-6-nitro-3-trinitromethylcyclohexa-1,4-dienes 8 and 9 in addition to 2-methyl-4-trinitromethylanisole (3) and 2-methyl-4-nitroanisole (4). In acetonitrile the yields of compound 4 and adducts 8 and 9 are significantly higher. Similar reaction of 2,3-dimethylanisole (6) in dichloromethane gave nitro-trinitromethyl adducts 10 and 11, hydroxy-trinitromethyl adducts 12 and 13, 2,3-dimethyl-5-trinitromethylanisole (14), 4-methoxy-2,3-dimethylbenzonitrile N-oxide (15), 2,3-dimethyl-4-trinitromethylanisole (16), 2,3-dimethyl-4-nitroanisole (17), 2,3-dimethyl-4,6-dinitrophenol (18), 3-methoxy-4,5-dimethyl-benzoic acid (19) and the hydroxy dinitro compound (20). The photolysis of the CT complex of 2,4-dimethylanisole (7) with tetranitromethane in dichloromethane gave the epimeric 1-methoxy-4,6-dimethyl-6-nitro-3-trinitromethylcyclohexa-1,4-dienes 21 and 22, together with 4,6-dimethyl-3-trinitromethylanisole (23), 4,6-dimethyl-2-nitrophenol (24), 4,6-dimethyl-2-trinitromethylanisole (25), 4,6-dimethyl-3-nitroanisole (26), 4,6-dimethyl-2-nitroanisole (27) and 4,6-dimethyl-4-nitrocyclohexa-2,5-dienone (28). The modes of formation of the above products are discussed, including the effects of the reaction solvent on those processes. The X-ray crystal structure of 1-methoxy-2-methyl-c-6-nitro-r-3-trinitromethylcyclohexa-1,4-diene (9) is reported. Acta Chemica Scandinavica 1997.
- Butts, Craig P.,Eberson, Lennart,Hartshorn, Michael P.,Robinson, Ward T.,Timmerman-Vaughan, David J.
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