- New methodology for the conversion of epoxides to alkenes
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Epoxides have been transformed in good yields to alkenes by a process involving (i) ring-opening of the epoxide with 2-mercaptobenzothiazole, (ii) oxidation of the derived ss-hydroxy thioethers to the corresponding sulfones, and (iii) thermal or base-promoted fragmentation of these sulfones to alkenes. The stereochemistry of the starting epoxide is transfer-red faithfully to the alkene product, because of the SN2 epoxide ring-opening reactions and the antiperiplanar SO2 elimination reaction of the ss- alkoxysulfinate intermediates. This methodology may form the basis of a new protecting group strategy for alkenes.
- Wu, Feng-Ling,Ross, Benjamin P.,McGeary, Ross P.
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experimental part
p. 1989 - 1998
(2010/06/15)
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- From vinyl sulfides, sulfoxides, and sulfones to vinyl transition metal complexes
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A transformation with promising versatility: The vinyl zirconium complex 1 can be prepared readily in situ from the educts mentioned in the title and reacts with electrophiles, including other transition metal complexes, to give polysubstituted olefins (s
- Farhat, Shahera,Marek, Ilan
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p. 1410 - 1413
(2007/10/03)
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- Highly stereo and chemoselective iron-catalyzed alkenylation of organomagnesium compounds
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In the presence of Fe(acac)3, Grignard reagents react readily with alkenyl halides (X = I, Br or Cl) in a THF/NMP mixture to give the cross-coupling products in high yields with an excellent stereoselectivity (≤99.5%). The scope of the reaction is very broad since a vast array of functional groups are tolerated (esters, nitriles, aromatic or aliphatic halides and even ketones). The procedure reported herein is an interesting alternative to the classical Pd- or Ni-catalyzed reactions, especially for preparative organic chemistry.
- Cahiez, Gerard,Avedissian, Hovsep
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p. 1199 - 1205
(2007/10/03)
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- Thermal Dehydrochlorination of Poly(vinyl chloride) Model Compounds. I
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The liquid phase (neat and solution) thermal degradation of a number of compounds which model the common defect groups found in pvc has been investigated.Compounds with halogen atoms at tertiary positions have stabilities similar to allylic halides.However, there was nearly a tenfold difference in the rate of reaction between the positionally isomeric 2-chloroalk-3-enes and 4-chloroalk-2-enes.Compounds with unsaturation within a longer chain or compounds lacking a terminal methyl group are somewhat less reactive.The dehydrochlorination reaction was confirmed to be accelerated by glass surfaces, hydrogen chloride and polar solvents.
- Boughdady, Nabil M.,Chynoweth, Kevin R.,Hewitt, David G.
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p. 567 - 579
(2007/10/02)
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- Direct and Regioselective Transformation of α-Chloro Carbonyl Compounds into Alkenes and Deuterioalkenes
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The successive treatment ethyl chloroacetate or chloroacetyl chloride with Grignard reagents and lithium powder leads to symmetrical terminal olefins in a regioselective manner.The best results are obtained with acid chlorides.The influence of the temperature and the reaction time on overall yield of the process are studied; in general, yields are increased by working at low temperature (-60 deg C).Internally substituted olefins are obtained from α-chloro acid chlorides through a similar process.The treatment of α-chloro aldehydes, ketones and carboxylic acid derivatives (esters or acid chlorides) with lithium aluminium hydride or lithium aluminium hydride/aluminium chloride and lithium powder at low temperature (-60 deg C) leads in a regioselective manner to olefins with the same carbon skeleton as the starting carbonyl compound.Reactions with lithium aluminium deuteride lead to incorporation of deuterium at predetermined positions in the alkene.
- Barluenga, Jose,Yus, Miguel,Concellon, Jose M.,Bernad, Pablo
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p. 2721 - 2726
(2007/10/02)
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