- Selective reduction of mono- and disubstituted olefins by NaBH4 and catalytic RuCl3
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Direct use of the relatively inexpensive reagent, RuCl3 × H2O, as a catalyst for the reductions of olefins in the presence of water is reported. The combination of cheap and readily available sodium borohydride and a catalytic amount of RuCl3 × H2O selectively reduces mono- and disubstituted olefins, whereas trisubstituted olefins, unless activated, and benzyl ethers remain inert.
- Sharma, Pawan K.,Kumar, Surender,Kumar, Pawan,Nielsen, Poul
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p. 8704 - 8708
(2008/03/14)
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- Synthesis of 2,3-disubstituted indoles by radical cyclization with hypophosphorous acid and its application to total synthesis of (±)-catharanthine
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Radical cyclization of o-alkenylthioanilides using hypophosphorous acid and AIBN in the presence of Et3N proceeded smoothly to furnish the corresponding 2,3-disubstituted indoles in high yields. Utilizing the newly developed cyciization condition, a stereocontrolled total synthesis of (±)-catharanthine has been completed.
- Reding, Matthew T.,Kaburagi, Yosuke,Tokuyama, Hidetoshi,Fukuyama, Tohru
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p. 313 - 330
(2007/10/03)
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- Structural studies on dioxan-2-ylium ions: intramolecular attack of an oxygen atom on a carbenium ion centre
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As models for the ionization of orthoesters, a series of 1,3-dioxan-2-ylium salts have been prepared and characterized.The properties of 1,3-dioxan-2-ylium hexachloroantimonate 1, 5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 2, 2-methyl-5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 3, and 2-phenyl-5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 4, have been studied by 1H and 13C NMR spectroscopy.The structures of 3 and 4 have been determined using X-ray crystallography.Salts 3 and 4 both crystallize in monoclinic crystal systems.For 3, the space group is C2/c, with a=30.192(4) Angstroem, b=9.613(2) Angstroem, c=12.742(2) Angstroem, β=109.71(1) deg, V=3482(1) Angstroem3, and Z=8.Complex 4 crystallizes in the space group P21/n, with a=10.638(2) Angstroem, b=11.849(2) Angstroem, c=16.970(3) Angstroem, β=106.84(1) deg, V=2047(1) Angstroem3, and Z=4.The geometries of 3 and 4 are similar with the ether oxygen disposed over the dioxan-2-ylium ring.However, the interaction between the ether oxygen and the cationic centre is not significant due to the large internuclear distance observed.The cation 5, in which the carbon chain length between the ether oxygen and C(5) was increased, was prepared.This ion was found to undergo a reversible, intramolecular rearrangement resulting in the formation of 1-methyl-4-acetoxymethyl-tetrahydroguranyl oxonium hexachloroantimonate 11.
- Childs, Ronald F.,Kang, Guogong J.,Wark, Teresa A.,Frampton, Christopher S.
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p. 2084 - 2093
(2007/10/02)
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- Method of preparing alkoxymethylenemalonic acid esters
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Preparation of alkoxymethylene malonic acid ester of formula: STR1 wherein R and each R' is an alkyl group, by reaction of malonic acid diester and ortho formic acid triester. The reaction is performed in the presence of a carboxylic acid or a carboxylic acid anhydride and a Lewis acid. The ortho ester is initially present in amount of at least 1,4 mols per mole of the malonic acid ester starting material. Alcohol formed during the reaction is removed during the reaction.
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