- Iterative synthesis of alkenes by insertion of lithiated epoxides into boronic esters
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The insertion of lithiated epoxides into boronic esters followed by thermal syn-elimination provides a stereospecific entry to alkenes. This process avoids transition metals and is amenable to iteration to provide higher substitution patterns.
- Bojaryn, Kevin,Fritsch, Stefan,Hirschhaüser, Christoph
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supporting information
p. 2218 - 2222
(2019/04/10)
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- A regio- and stereoselective synthesis of trisubstituted alkenes via gold(i)-catalyzed hydrophosphoryloxylation of haloalkynes
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A new stereoselective synthesis of trisubstituted alkenes is developed. Hydrophosphoryloxylation of haloalkynes provides Z-alkenyl halophosphates, which undergo Pd-catalyzed consecutive cross-coupling reactions to afford regio- and stereodefined trisubsti
- Chary, Bathoju Chandra,Kim, Sunggak,Shin, Doosup,Lee, Phil Ho
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p. 7851 - 7853
(2011/09/12)
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- Novel alkylidenating agents of iron(III) derivatives by base-mediated α,μ-dehydrohalogenation and their chemical trapping by cycloaddition
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Studies of the reactions between group 4 metal, chlorides (M = Ti, Zr, Hf) and methyllithium at -78 °C in toluene can lead to methylidene-metal complexes, H2C=MCl2, by a sequence of monomethylation, α-carbon lithiation and α,μ-elimination of LiCl. Here study of the preparation of alkylidene derivatives of iron was attempted by the interaction of FeCl3 with n-butyllithium in various ratios at -78 °C. The presence of any resulting butylidene-iron(III) derivative, nPrCH=FeE (E = Cl, nBu), was probed by adding chemical trapping agents, such as diphenylacetylene, benzonitrile, methyl benzoate and benzophenone. In each experiment the hydrolyzed products were consistent with a cycloaddition reaction of nPrCH=FeE with the trapping agent. The products from, di-phenylacetylene and from, benzonitrile with D2O workup are uniquely in accord with such a carbene precursor. A 3:1 ratio of nBuLi/FeCl3 gave the optimal yield of nPrCH=FenBu, ca. 80%, from, the MBu2FeCl precursor. When a 3:1. reaction mixture was simply brought to 25 °C and hydrolyzed, the purple alkylidene-iron complex decomposed completely to iron metal. A study of a 3:1 interaction of PhCH2MgCl and FeCl3 under similar conditions and trapping with diphenylacetylene provided evidence for the formation of PhCH=FeCH2Ph in ca. 40%. These results support; the hope that alkylidene-iron(III) analogs of the Grubbs reagents may be accessible by this process.
- Eisch, John J.,Sohn, Jane U.,Rabinowitz, Edon J.
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experimental part
p. 2971 - 2977
(2010/08/20)
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- Carbolithiation of diphenylacetylene as a stereoselective route to (Z)-tamoxifen and related tetrasubstituted olefins
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(Chemical Equation Presented) Carbolithiation of diphenylacetylene can be exploited to generate (E)-1-lithio-1,2-diphenylalkyl-1-enes which can be reacted in situ with triisopropylborate to stereoselectively provide (E)-1,2-diphenyl-1-alkylene boronic acids. These tetrasubstituted vinylboronic acids served as versatile intermediates for the generation of tetrasubstituted olefins with retention of stereochemistry. The application of this method for the stereoselective synthesis of (Z)-tamoxifen and related analogues is described.
- McKinley, Neola F.,O'Shea, Donal F.
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p. 9552 - 9555
(2007/10/03)
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- The Peterson olefination using the tert-butyldiphenylsilyl group: Stereoselective synthesis of di- and trisubstituted alkenes
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The reaction of α-tert-butyldiphenylsilyl carbonyl compounds with organometallics leads with a high diastereoselectivity to erythro-β-hydroxysilanes, which under acidic or basic elimination conditions give E or Z di- and trisubstituted alkenes.
- Barbero,Blanco,Garcia,Pulido
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p. 1223 - 1228
(2007/10/03)
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- DIRECT PREPARATION OF SUBSTITUTED OLEFINS FROM EPOXIDES UTILIZING LITHIUM TETRAALKYLCERATE
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Alkylated olefins were directly synthesized in good yields by the deoxygenation reaction of epoxides with concomitant introduction of the alkyl group using lithium tetraalkylcerate.Styreneoxide and (1-naphtyl)ethyleneoxide gave terminal olefins, while ethyleneoxide replaced by alphatic substituent, 1,2-epoxy-4-phenylbutane, afforded internal olefin.The utility of the present method was demonstrated in the one-step synthesis of a sesquiterpene, dehydro-α-curcumene.
- Ukaji, Yutaka,Fujisawa, Tamotsu
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p. 5165 - 5168
(2007/10/02)
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