- Controlling the reactive state through cation binding: Photochemistry of enones within zeolites
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The nature of the lowest triplet state of enones is altered by the cations present within Y zeolites. Alkali metal ions, such as Li+, are predicted to interact with the carbonyl unit of enones in a collinear fashion and significantly lower both the p-type n and π-2 orbitals. Excited state energies, estimated at the CIS(D)/6-31+G* level, show that the lowest triplet is n-π* in character for the enones, but switch to π-π* on coordination with Li+. Observed product distribution within zeolite is consistent with this theoretical prediction.
- Uppili, Sundararajan,Takagi, Shinsuke,Sunoj,Lakshminarasimhan,Chandrasekhar,Ramamurthy
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p. 2079 - 2083
(2007/10/03)
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- Long-range effect of 17-substituents in 3-oxo steroids on 4,5-double bond hydrogenation
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The long-range effect of substituents in the 17-position on the hydrogenation of double bond of the steroidal Δ4-3-ketones in acetic acid on a platinum catalyst is described in a series of testosterone (1) and epitestosterone (5) esters with carboxylic acids of varying alkyl chain length. The ratio 5α-to 5β-products is affected by the nature of substituents in the position 17.
- Sidova, Romana,Stransky, Karel,Kasal, Alexander,Slavikova, Barbora,Kohout, Ladislav
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p. 1528 - 1542
(2007/10/03)
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- Stereochemistry of the Palladium-catalyzed Hydrogenation of 3-Oxo-4-ene Steroids. V. A Kinetic Study in Basic and Acidic Media
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Effects of the β-methyl group at C-10 and some oxygen functions (=O, OH, OAc) at C-11, C-17, and C-20 on the rates of hydrogenation of 3-oxo-4-ene steroids have been studied with palladium catalyst in pyridine or THF/HBr as solvent.In contrast to the hydrogenation in pyridine, the rate in THF/HBr was greatly depressed by the presence of 10β-methyl group.The reactivity of the steroids was enhanced by the oxygen functions, in particular, by 11, 17-dioxo group.The effects of the substituents are discussed from a mechanistic consideration based on the obtained results.
- Nishimura, Shigeo,Momma, Yasuhiro,Kawamura, Hideo,Shiota, Michio
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p. 780 - 783
(2007/10/02)
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- NAD(P)H Models XV. Reduction of Δ4-3-ketosteroids via their iminium salts, by 1,4-dihydropyridine derivatives
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Pyrrolidinium salts derived from a series of 17-substituted Δ4-3-ketosteroids are reduced by 1-benzyl-1,4-dihydronicotinamide (BNAH) and 2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine (Hantzsch ester, 1 eq.) to the corresponding isomeric 5α- and 5β-enamines which hydrolyse to the corresponding 3-ketosteroids.In the case of the Hantzsch ester reduction, proton transfer from the oxidized Hantzsch ester to the enamine results in the formation of iminium salts, which are further reduced to the corresponding ammonium salts.Mechanistic, stereochemical and biochemical implications of the reactions are discussed.
- Gase, Ronald A.,Pandit, Upendra K.
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p. 334 - 340
(2007/10/02)
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