21676-08-4Relevant articles and documents
CP2TiCl2-catalyzed hydroalumination of internal alkynes: An access to (Z)-olefins
Parenty, Arnaud,Campagne, Jean-Marc
, p. 1231 - 1233 (2007/10/03)
The reduction of alkynols with LiAlH4 in diglyme is a long known process leading to the formation of (E)-alkenols. We have, by serendipity, found that, in the presence of a catalytic amount (10%) of Cp2TiCl2, the stereoselectivity of the reaction is reversed, leading to the selective formation of the (Z)-alkenols. The scope and limitations of this methodology and a postulated catalytic cycle are also discussed.
A novel hydrogen transfer hydroalumination of alkenes with triisobutylaluminum catalyzed by Pd and other late transition metal complexes
Gagneur, Sebastien,Makabe, Hidefumi,Negishi, Ei-Ichi
, p. 785 - 787 (2007/10/03)
Hydrogen transfer hydroalumination of terminal alkenes and dienes can be achieved with 1.1 equiv. of (i-Bu)3Al and catalytic amounts of Cl2Pd(PPh3)2 and other late transition metal complexes containing Co, Rh, Ni, and Pt at ambient temperature in high yields.
Azidomercurations of alkenes: Mercury-promoted Schmidt reactions
Pearson,Hutta,Fang
, p. 8326 - 8332 (2007/10/03)
Azides bearing a suitably disposed alkene, when treated with either mercuric perchlorate or mercuric trifluoromethanesulfonate, produce bicyclic iminium ions. This new version of the Schmidt reaction proceeds by capture of the mercuronium ion intermediate by the azide to produce an aminodiazonium ion, which suffers a 1,2-shift to give an iminium ion (e.g., 10 → 16 → 17 → 18). Reduction of the iminium ion may then be carried out to produce an amine. Compared to earlier work on the protic acid-promoted intramolecular Schmidt reaction of azido-alkenes, the mercury-promoted Schmidt reaction has several advantages. First, the acid-promoted Schmidt reaction of azido-alkenes requires that the intermediate carbocations be tertiary, allylic, benzylic, or propargylic. The mercury-promoted method has no such limitation; thus even 1,2-disubstituted alkenes may be used. Second, the mercury-promoted method is milder, allowing the presence of acid-sensitive functionality. The protic version, typically employing trifluoromethanesulfonic acid, is limited in its functional group tolerance. Third, whereas carbocation rearrangement is often observed prior to cyclization/rearrangement in the acid-promoted Schmidt reaction, the mercury-promoted method avoids this problem. Fourth, the presence of the mercurio group during the rearrangment may alter the regioselectivity of the 1,2-migration. Finally, the mercury-bearing iminium ions that are the result of the Schmidt reaction were found to be sensitive to protodemercuration, precluding their use in other transformations.
The Copper(I)-catalysed Coupling of Grignard Reagents with 5-Lithio-2,3-dihydrofuran and 6-Lithio-3,4-dihydro-2H-pyran
Barber, Christopher,Bury, Paul,Kocienski, Philip,O'Shea, Michael
, p. 1595 - 1597 (2007/10/02)
The organocuprates derived from reaction of Grignard reagents with CuBr*Me2S react with 5-lithio-2,3-dihydrofuran and 6-lithio-3,4-dihydro-2H-pyran via a 1,2-metallate rearrangement to generate an alkenylmagnesium cuprate.
FRGMENTATION INDUITE PAR LE SILICIUM (II). SYNTHESE STEREOSELECTIVE DU NONACOSADIENE-7(Z), 11(Z), PHEROMONE DE CONTACT DE DROSOPHILA MELANOGASTER
Bac, Nguyen Van,Fall, Yagamare,Langlois, Yves
, p. 841 - 844 (2007/10/02)
7(Z),11(Z)-nonacosadiene 1, pheromone of Drosophila melanogaster, has been prepared from tetrahydropyridine 3 via a silicon induced fragmentation, a coupling reaction with Grignard reagent and a Witting olefination.
