The synthesis of a series of enantiomerically pure, C,-symmetric 4,4,5,5'-tetrahydro-2,2'-methylenebis[oxazoles] and 4,4',5,5'-tetrahydro-2,2'-bi(oxazoles) is reported. Copper complexes with anionic tetrahydromethylenebis[oxazole] ligands are efficient catalysts for the enantioselective cyclopropane formation from olefins and diazo compounds (up to 96% ee in the reaction of styrene with menthyl diazoacetate). Tetrahydrobi(oxazole)iridium(I) complexes were found to catalyze transfer hydrogenations of aryl alkyl ketones with i-PrOH (up to 91 % ee). Tetrahydrobi(oxazo1e)palladium complexes can be used as enantioselective catalysts for allylic nucleophilic substitution (up to 77% ee in the reaction of PhCH=CHCH(OAc)Ph with NaHC(COOMe),).Introduction. -In our previous papers in this series [l-31, we have reported on the synthesis and application of chiral semicorrins 1, a class of bidentate ligands specifically designed for enantioselective control of metal-catalyzed reactions. Essential structural features of the semicomns 1 are the conformationally rigid ligand framework and the C,-symmetric arrangement of the stereogenic centers in close proximity to the coordination site. In a metal complex, the substituents at the stereogenic centers effectively shield the metal ion from two opposite directions and, therefore, should have a distinct effect on the stereochemical course of a reaction taking place in the coordination sphere. So far, we have found two promising areas of application for semicorrin ligands: [Cu(semicorrinato)]-catalyzed cyclopropane formation from olefins and diazo compounds (up to 97% ee [ 1][3]) and [Co(semicorrinato)]-catalyzed conjugate reduction of a$-unsaturated carboxylic esters and amides (up to 99% ee [21[31).Symmetric 4,4',5,5'-tetrahydro-2,2'-methylenebis[oxazoles] 2 are structurally closely related to the semicorrins 1. Removal of a proton at the methylene bridge leads to anionic ligands which provide essentially the same steric environment for a coordinated metal ion as the corresponding semicorrinates (cf. 3). Chiral tetrahydrobis[oxazoles] of this type can be easily synthesized from amino alcohols and malonic acid. Starting from other dicarboxylic

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Reaction of the tartrate-derived diol (R,R)-d, CI, a',a'-tetraphenyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol (TADDOL) with chlorodiphenylphosphane gives a new bis(diphenylphosphany1) ligand (TADDOP). The complex 4 formed with PdCI, has been crystallized and its structure determined by X-ray diffraction (Fig. I). The complex is used for Pd-catalyzed enantioselective 1,3-diphenylaIlylations of various nucleophiles which give products with enantiomer ratios of up to 88 : 12 (Scheme 2). Crystallization procedures lead to the enantiomerically pure ( > 99 : 1) product 11 derived from dimethyl malonate. The structure of the TADDOP complex 4 is compared with those of other transition-metal complexes containing chelating bis(diphenylphosphany1) ligands (Fig. 2). A crystallographic data base search reveals that the structures of transition-metal complexes containing two Ph2P groups (superpositions in Fzg.3) fall into one of two categories: one with approximate C, symmetry and the other with C s mmetry (20 and 19 examples, resp.). A mechanistic model is proposed which correlates the conformational chirality (6 or A ) of the four Ph groups' arrangement in such complexes with the topicity of nucleophile approach on Pd-bound trans,trans-l,3-diphenylallyl groups (Scheme 3 and Table).