11C-C bond formation by palladium-mediated cross-coupling of alkenylzirconocenes with [11C]methyl iodide
11C-C bond formation by palladium-mediated cross-coupling of alkenylzirconocenes with [11C]methyl iodide
Berndt, M.; Wüst, F.
The prenyl group is known as an important structural building block in natural and medicinal products. The isotopic substitution of one of the two methyl groups with a [11C]methyl group would provide an access to a large number of interesting 11C-labelled compounds. Here we report a strategy for the synthesis of 11C-labelled prenyl group-containing derivatives starting from methyl-substituted alkynes (1) via a novel 11C-C bond forming reaction. A commonly employed strategy to form a,a-disubstituted alkenes comprises the formation of alkenylzirconocenes by the syn-insertion of a C-C triple bond into the Zr-H bond of Schwartz reagent [Cp2Zr(H)Cl] followed by metal-mediated C-C bond formation with electrophiles under retention of the configuration of the C-C douple bond [1,2].
In principle the formation of alkenylzirconocenes by syn-addition of Schwartz reagent onto disubstituted alkynes (1) leads to a mixture of regioisomers 2 and 2. However, treatment of an excess of Schwartz reagent favors the formation of the sterically less hindered isomer 2. Transmetalation with transition metal complexes M(PPh3)4 and conversion with [11C]MeI leads to compound 4.
Keywords: 11C-C bond formation; [11C]MeI; alkenyl-zirconium complexes
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Lecture (Conference)
International Symposium on Radiopharmaceutical Chemistry (ISRC 2005), 24.-28.06.2005, Iowa City, Iowa, USA -
Abstract in refereed journal
Journal of Labelled Compounds and Radiopharmaceuticals 48(2005), S24
Permalink: https://www.hzdr.de/publications/Publ-7432
Publ.-Id: 7432