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New Chiral P-N Ligands for the Regio- and Stereoselective Pd-Catalyzed Dimerization of Styrene
Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy
Department de Química Analítica i Química Orgànica, Universitat Rovira i Virgili, C. Marcel.lí Domingo s/n 43007 Tarragona, Spain
* Author to whom correspondence should be addressed.
Received: 27 December 2010; in revised form: 17 February 2011 / Accepted: 18 February 2011 / Published: 22 February 2011
Abstract: Two new chiral, enantiomerically pure, hybrid P-N ligands, namely (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octan-4-one (1) and (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octane (2), have been synthesized starting from L-proline. The two ligands differ in the presence or not of a carbonyl group in the diazaphosphane ring. Their coordination chemistry towards Pd(II) was studied by reacting them with [Pd(CH3)Cl(cod)]. A different behaviour was observed: ligand 2 shows the expected bidentate chelating behaviour leading to the mononuclear Pd-complex, while ligand 1 acts as a terdentate ligand giving a dinuclear species. The corresponding cationic derivatives were obtained from the palladium neutral complexes, both as mono- and dinuclear derivatives, and tested as precatalysts for styrene dimerization, yielding E-1,3-diphenyl-1-butene regio- and stereoselectively as the sole product. A detailed analysis of the catalytic behaviour is reported.
Keywords: hybrid phosphorus-nitrogen ligands; palladium; alkene dimerization
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Fanfoni, L.; Meduri, A.; Zangrando, E.; Castillon, S.; Felluga, F.; Milani, B. New Chiral P-N Ligands for the Regio- and Stereoselective Pd-Catalyzed Dimerization of Styrene. Molecules 2011, 16, 1804-1824.
Fanfoni L, Meduri A, Zangrando E, Castillon S, Felluga F, Milani B. New Chiral P-N Ligands for the Regio- and Stereoselective Pd-Catalyzed Dimerization of Styrene. Molecules. 2011; 16(2):1804-1824.
Fanfoni, Lidia; Meduri, Angelo; Zangrando, Ennio; Castillon, Sergio; Felluga, Fulvia; Milani, Barbara. 2011. "New Chiral P-N Ligands for the Regio- and Stereoselective Pd-Catalyzed Dimerization of Styrene." Molecules 16, no. 2: 1804-1824.