Other Ligand Classes

As with N,N ligands, P,S ligands have not received much attention in the area of the Mizoroki-Heck reaction. However, there are a couple of reported examples. Kang et al. [53] applied the pseudo-C2-symmetric P,S-hybrid ferrocenyl ligand 85 to the phenylation of 2,3-dihydrofuran (1). However, low conversions ( 37%) and low enantiomeric excesses ( 34%) were achieved. Molander et al [54] applied cyclopropane-based P,S ligands 86 and 87 to the same reaction. Excellent conversions (np to 99%) and moderate enantiomeric excesses (up to 60%) were obtained. 

Dai et al. [55] reported the only example of P,0 ligands applied to the asymmetric Mizoroki-Heck reaction. The atropisomeric amide-derived ligands 88 were applied to the reaction of phenyl triflate (2) and 2,3-dihydrofuran (1). Conversions were low ( 30%) in all cases, although moderate enantioselectivity was observed (52% ee, ligand 88a). 

(1968) Arylation, methylation and carboxyalkylation of olefins by Group Vm metal derivatives. J. Am. Chem. Soc., 90, 5518-22. 

Mizoroki, T., Mori, K. and Ozaki, A. (1971) Arylation of olefins with aryl iodide catal3raed by palladium. Bull. Soc. Chem. Jpn., 44, 581-1. 

and Nolley, J.P. Jr (1972) Palladium-catalyzed vinylic hydrogen substitution reactions with aryl, benzyl, and styryl halides. J. Org. Chem., 37, 2320-2. 

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Ferrocene-based complexes have some potential for the enantioselective reduction of ketones, but compared to other ligand classes this is relatively limited [3]. Rh complexes of bppfa, bophoz and josiphos are among the most selective catalysts for the hydrogenation of a-functionalized ketones (Table 25.9 Fig. 25.18, 30-32). Ru complexes of walphos and ferrotane are quite effective for... 

With few other ligand classes do zinc and cadmium form such a structurally varied series of complexes.7676 Multinuclear complexes and intriguing geometries abound. 

Other ligands have been examined to improve the performance of platinum-catalyzed reactions,40 and bicyclic aminophosphines (Scheme 7, G) are a sterically demanding structural class that has been employed to afford very high regioselectivities41... 

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