Palladium-catalyzed oxyarylation of olefins using silver carbonate as the base. Probing the mechanism by electrospray ionization mass spectrometry

• Published in: Journal of organometallic chemistry Vol. 695; no. 18; pp. 2062 - 2067
• Main Authors: Buarque, Camilla D., Pinho, Vagner D., Vaz, Boniek Gontijo, Eberlin, Marcos N., da Silva, Alcides J.M., Costa, Paulo R.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-08-2010
• Subjects: Mass spectrometry; ortho-Iodophenols; Oxa-Heck; Oxyarylation; Palladium catalyst; Pterocarpans; Pterocarpans; Oxa-Heck; ortho-Iodophenols; Oxyarylation; Palladium catalyst; Mass spectrometry
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2010.05.014

The Pd(OAc)
2-catalyzed oxyarylation of electron-rich (
8 and
12) and electron-poor (
10) olefins by
ortho-iodophenols (
3a–
d) was studied using Ag
2CO
3 as the base, in acetone, and in the presence and absence of PPh
3. The corresponding adducts of oxyarylation were obtained in moderate yields. The reaction mechanism was examined by electrospray ionization mass spectrometry (ESI-MS). Cationic arylpalladium intermediate (
14), formed by the oxidative insertion of Pd(0) into
3a, and the cationic palladacycles (
15), obtained by reaction of
14 with olefins
8 and
12, were intercepted by ESI-MS and characterized by ESI-MS/MS.
The mechanism of the Pd-catalyzed oxyarylation of
8 by
3a leading to (±)-
9a was investigated by electrospray ionization mass spectrometry. The key intermediate cyclo-palladate
15b was intercepted and characterized. The scope of this synthetically useful reaction was studied using other olefins (
10 and
12) and
ortho-iodophenols (
3b,
c,
d). A similar cationic intermediate was intercepted in the reaction of
12 with
3a. Competitive experiments show that reactivity order toward
3a is
8
>
12
>
10.
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