Catalyst‐ and Solvent‐Dependent Stereodivergence in the Intramolecular Et2Zn/Pd0‐Promoted Carbonyl Propargylation: Mechanistic Implications. Issue 41 (21st August 2013)

• Record Type: Journal Article
• Authors: Arrate, Mónica; Durana, Aritz; Lorenzo, Paula; de Lera, Ángel R.; Álvarez, Rosana; Aurrecoechea, José M.
• Is Part Of: Chemistry. Volume 19:Issue 41(2013)
• Page Start: 13893
• Page End: 13900
• Publication Date: 2013-08-21
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201301170
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Carbonyl‐tethered propargylic benzoates undergo intramolecular carbonylpropargylation upon treatment with Et₂Zn in the presence of a catalytic amount of Pd⁰ with the formation of 2‐alkynylcyclopentanol products. A ligand/solvent effect on the <italic>cis</italic>/<italic>trans</italic> selectivity (referring to the relative positions of alkynyl and OH groups) of ring‐closure has been found. In a non‐coordinating solvent (benzene), increasing the electron‐donating ability of the phosphine ligand (while decreasing its dissociation ability) leads to an increased tendency towards the <italic>trans</italic> product. On the other hand, the combination of a coordinating solvent (THF) and PPh₃, an easily dissociated phosphine, results in the exclusive formation of <italic>cis</italic> products. Experimental and computational results are compatible with a divergent behavior of an allenylethylpalladium intermediate that partitions between competitive carbonyl‐addition and transmetalation pathways, each leading to a different diastereoisomer. These results also suggest that the dissociating ability of the phosphine regulates that behavior.</p> </abstract>