1-Phosphino-2-sulfenylferrocenes as Planar Chiral Ligands in Enantioselective Palladium-Catalyzed Allylic Substitutions

• Published in: Journal of organic chemistry Vol. 68; no. 9; pp. 3679 - 3686
• Main Authors: Mancheño, Olga García, Priego, Julián, Cabrera, Silvia, Arrayás, Ramón Gómez, Llamas, Tomás, Carretero, Juan Carlos
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 02.05.2003; Amer Chemical Soc
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Chemistry, Organic; Exact sciences and technology; General and physical chemistry; Physical Sciences; Science & Technology; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; ASYMMETRIC-SYNTHESIS; TRANSITION-METAL COMPLEXES; (ETA-ALLYL)PALLADIUM COMPLEXES; CHEMICAL-SHIFTS; PHOSPHINOOXATHIANE LIGANDS; ALKYLATION; 1,1'-P,N-FERROCENE LIGANDS; X-RAY STRUCTURE; NUCLEOPHILIC-ADDITION; 1,2-DISUBSTITUTED FERROCENES; Catalytic reaction; Enantioselectivity; Tertiary phosphine; Molecular structure; Palladium complex; Chiral compound; NMR spectrometry; X ray diffraction; Allylic compound; Chemical substitution; Organic sulfide; Ferrocene; Bidentate ligand; Iron complex; Reaction mechanism; Chemical synthesis; Ethylenic compound; Nucleophile
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo0340657

The synthesis of a wide structural variety of enantiopure 1-phosphino-2-sulfenylferrocene ligands 1 possessing exclusively planar chirality is described. In the case of the readily available tert-butylsulfenyl derivatives very high enantioselectivities were obtained in the palladium-catalyzed allylic substitution of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate (ee's up to 97%) and nitrogen nucleophiles (ee's up to 99.5%). Palladium complexes of these ferrocenes were characterized by NMR and X-ray diffraction, revealing the P,S-bidentate character of the ligands 1 and the formation of a single epimer on the stereogenic sulfur atom resulting from the complexation with palladium. A model justifying the observed asymmetric induction exerted by this novel family of chiral ferrocenes, supported by solution NMR studies on a palladium allylic complex, is discussed.