The Pd(0)-mediated rapid coupling of methyl iodide with an excess of alkenyltributylstannane was examined with the aim of incorporating a short-lived 11C-labeled methyl group into a biologically significant organic compound with a 1-methylalkene unit for the synthesis of a PET tracer. Four sets of reaction conditions (A–D) were used, all performed in DMF at 60 °C for 5 min. Condition B, using CH3I/stannane/Pd2(dba)3/P(o-tolyl)3/CuCl/K2CO3 (1 : 40 : 0.5 : 4–6 : 2 : 5), works well in almost all cases. Condition D, using CH3I/stannane/Pd2(dba)3/P(o-tolyl)3/CuX (X = Br, Cl, or I)/CsF (1 : 40 : 0.5–5 : 2–20 : 2–20 : 5–50), shows the best results with regard to general applicability to tin substrates, affording the corresponding methylated product in >90% yield based on consumption of methyl iodide. P(t-Bu)2Me was less effective than P(o-tolyl)3, particularly for α,β-unsaturated carbonyl substrates. No regio- or stereoisomerization occurred under these reaction conditions. The efficiency of the protocol was demonstrated by synthesis of an 11C-methylated compound.
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