Ni<sup>I</sup>Catalyzes the Regioselective Cross-Coupling of Alkylzinc Halides and Propargyl Bromides to Allenes
作者:Rita Soler-Yanes、Iván Arribas-Álvarez、Manuel Guisán-Ceinos、Elena Buñuel、Diego J. Cárdenas
DOI:10.1002/chem.201603758
日期:2017.1.31
We describe the unprecedented formation of allenes by Ni‐catalyzed cross‐coupling of propargyl bromides with alkylzinc halides. The reaction regioselectivity is complementary to the previously reported formation of propargyl‐coupled compounds. Experiments support the formation of NiI complexes as the active species and the participation of radical intermediates. Kinetic studies showed that the reaction
Oxidative Coupling Reactions of Grignard Reagents with Nitrous Oxide
作者:Gregor Kiefer、Loïc Jeanbourquin、Kay Severin
DOI:10.1002/anie.201302471
日期:2013.6.10
Catalysis with laughing gas: N2O in combination with transition‐metal catalysts allow the oxidative homo‐ and cross‐coupling of Grignard reagents. The reactions can be performed under mild conditions despite the inert character of N2O.
Iron-Catalyzed Hydroborylative Cyclization of 1,6-Enynes
作者:Natalia Cabrera-Lobera、Patricia Rodríguez-Salamanca、Juan C. Nieto-Carmona、Elena Buñuel、Diego J. Cárdenas
DOI:10.1002/chem.201704401
日期:2018.1.19
reaction takes place under mild conditions, with inexpensive catalytic system and full atomeconomy. Mechanistic studies suggest the intermediacy of FeII-hydride active catalyst capable to react with the alkyne group prior to alkene insertion, and computational studies suggest the occurrence of barrierless σ-bond metathesis involving HBpin and Fe−C bonds along the catalytic cycle.
Annulations via Bifunctional Reagents. Total Syntheses of (±)-Methyl Cantabrenonate and (±)-Methyl Epoxycantabronate
作者:Edward Piers、Johanne Renaud
DOI:10.1055/s-1992-34160
日期:——
Total syntheses of the angularly fused triquinane sesquiterpenoids (±)-methyl cantabrenonate (10) and (±)-methyl epoxycantabronate (11) are described. The bicyclic enone, (RS)-5-methylbicyclo-[3.3.0]oct-1 (8)-en-2-one (18), was readily obtained from 3-methyl-2-cyclopenten-1-one (20). The highly stereoselective conversion of 18 into the tricyclic oxo alkene, (1R*,5R*,8R*)-5-methyl-9-methylenetricyclo [6.3.0.01,5]undecan-2-one (19), was achieved via a one-pot process involving the reaction of 18 with the novel lower order bifunctional cuprate reagent lithium (4-chloro-1-buten-2-yl)-cyanocuprate (15). The key intermediate 19 was transformed into the tricyclic enone (1R*,5R*,8S*, 9R*)-2,5,9-trimethyltricyclo-[6.3.0.01,5]undec-2-en-4-one (44), by means of a straightforward sequence of reactions. Hydrogenation of 44 gave a single ketone 45, which was converted, in two synthetic operations, into (±)-10. Treatment of 10 with hydrogen peroxide/sodium hydroxide provided, stereoselectively, (±)-11.
Fe-catalysed Kumada-type alkyl–alkyl cross-coupling. Evidence for the intermediacy of Fe(i) complexes
作者:Manuel Guisán-Ceinos、Francisco Tato、Elena Buñuel、Paloma Calle、Diego J. Cárdenas
DOI:10.1039/c2sc21754f
日期:——
A novel Fe–NHC catalytic system allows the alkyl–alkyl cross-coupling reaction of alkyl halides and alkylmagnesium reagents has been developed. To our knowledge, this is the first Fe-catalysed Kumada-type coupling for the formation of C(sp3)–C(sp3) bonds in the presence of functional groups. The process takes place under mild conditions, avoiding the formation of β-elimination products. Mechanistic