We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz’s reagent. Photochemical homolysis of the C–Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction
New effective reagent [Cp2ZrH2·ClAlEt2]2 for alkene hydrometallation
作者:Lyudmila V. Parfenova、Rushana F. Vil’danova、Svetlana V. Pechatkina、Leonard M. Khalilov、Usein M. Dzhemilev
DOI:10.1016/j.jorganchem.2007.04.007
日期:2007.7
New bimetallic complex [CP2ZrH2 . ClAlEt2](2) (1) was synthesized, and its reactivity in hydrometallation reaction with the following alkenes was studied: hept-l-ene, okt-l-ene, alpha-methylstyrene, (IS)-beta-pinene, (+)-camphene. Complex 1 shows the highest reactivity among the other known AI,Zr-bimetallic complexes: [CP2ZrH2 . ClAlBu2i](2) (2), [CP2ZrH2 . AlEt3](2) (3), [CP2ZrH2 . AlBu3i](2) (4) and [CP2ZrH2 . HAlBu2i] (5) as well as organoaluminium compounds (OAC): (BU2AlH)-B-i, (Bu3Al)-Bu-i and (Bu2AlCl)-Bu-i in presence of Zr catalysts. Chlorine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-beta-pinene <= (+)-camphene < alpha-methylstyrene < oct-l-ene < hept-l-ene. Hydrometallation of (1S)-beta-pinene and its subsequent oxidation with 12 run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation is less than that for (1S)-beta-pinene, and the reaction gives predominately endo-camphanol. (c) 2007 Elsevier B.V. All rights reserved.