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Osmium-catalyzed allylic alkylation

AuthorsEsteruelas, Miguel A. ; García-Yebra, Cristina ; Oliván, Montserrat ; Oñate, Enrique ; Valencia, Marta
Issue Date2008
PublisherAmerican Chemical Society
CitationOrganometallics 27(19): 4892-4902 (2008)
AbstractComplex [OsCl2(η6-p-cymene)]2 (1) reacts with (5,7-dioxa-6-phosphadibenzo[a,c]cyclohepten-6-yl)-dimethylamine (L1) and (-)-(R)-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′] dinaphthalen-4-yl)di-methylamine (L2) to give OsCl 2(η6-p-cymene)L (L = L1 (2), L2 (3)). Complexes 1-3 and OsCl2(η6-p-cymene){P(OPh) 3} (4) are efficient catalyst precursors for the alkylation of 1-phenylallyl methylcarbonate (5a), 1-phenylallyl acetate (5b), cinnamyl methylcarbonate (6a), and cinnamyl acetate (6b) with sodium dimethylmalonate to afford 1-phenylallyl dimethylmalonate (7) and cinnamyl dimethylmalonate (8) with branchedrlinear molar ratios between 97:3 and 67:33. In the absence of sodium dimethylmalonate, the reaction of 1 with 5a leads initially to {OsCl(η6-p-cymene)}2(ο-OMe)2 (9) and subsequently to [{Os(η6-p-cymene)}2(ο-OMe) 3][O2COMe] (10). In the absence of 5a, the reaction of 1 with sodium dimethylmalonate gives Os{k1-C3-[CH(CO 2Me)2]}{k2-O,O-[CH(CO2Me) 2]}(η6-p-cymene) (11). Complexes 9-11 are also efficient catalyst precursors for the alkylation of 5a with sodium dimethylmalonate. The activity of 9 and 10 is the same as that of 1. However, complex 11 is significantly less efficient than 1. In contrast to the latter, complexes 2 and 3 do not react with 5a in the absence of sodium dimethylmalonate. In the absence of the substrate, the reactions of 2 and 3 with sodium dimethylmalonate lead to OS{k1-C3-[CH(CO 2Me)2]}Cl(η6-p-cymene)L (L = L1 (12), L2 (13)), which further react with excess sodium dimethylmalonate to give 11. The catalytic behavior of 12 and 13 has been also studied. Their activities are the same as those of 2 and 3 and intermediate between those of 10 and 11. Complexes 3, 9, 11, and 12 have been characterized by X-ray diffraction analysis. © 2008 American Chemical Society.
Identifiersdoi: 10.1021/om800460h
issn: 0276-7333
e-issn: 1520-6041
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