Ferrocenyl oxazoline

The synthesis of ferrocene 9 relied on chemistry introduced by Sammakia, Uemura, and Richards [18]. They had shown that 2-ferrocenyl oxazoline 10 derived from t-leucine could be selectively deprotonated and trapped with electrophiles to afford ortho-functionalized planar-chiral products 11 with excellent diastereoselectivities (Scheme 2.1.2.3). Following this strategy, 9 became accessible in a highly straightforward manner by trapping the lithiated intermediate derived from 10 with benzophenone [10, 11],... 

Various ferrocene-based organosilanols 165 have been synthesized in two steps fi om chiral 2-ferrocenyl oxazolines 163. Diastereoselective ortho-lithiation with sec-BuLi followed by electrophilic attack with chlorosilanes gave diastereomerically enriched 164, which were oxidized in air with [IrCl(C8Hi2)]2 as catalyst to give, after purification, stereochemically homogeneous samples of 165. Their application in asymmetric phenyl transfer reactions to substituted benzaldehydes afforded products with high ee (up to 91%) <050L1407>. 

Donde Y, Overman LE (1999) High enantioselection in the rearrangement of allylic imidates with ferrocenyl oxazoline catalysts. J Am Chem Soc 121 2933-2934... 

In addition, Bonini et al. have shown that a planar chiral sulfur-containing ferrocenyl-oxazoline carbinol ligand, depicted in Scheme 3.59, could also be used to catalyse the addition of ZnEt2 to benzaldehyde with a moderate enantioselectivity (46% ee). ... 

Scheme 3.59 Sulfur-containing ferrocenyl-oxazoline carbinol ligand for addition of ZnEt2 to benzaldehyde.

Ferrocenyl ligands, via zinc reagents, 9, 120 Ferrocenylmethyl phosphonium salts, with gold(I), 2, 274 Ferrocenylmonophosphine, in styrene asymmetric hydrosilylation, 10, 817 Ferrocenyl oxazolines, synthesis, 6, 202 Ferrocenylphosphines with chromium carbonyls, 5, 219 in 1,3-diene asymmetric hydrosilylation, 10, 824-826 preparation, 6, 197 various complexes, 6, 201 Ferrocenylselenolates, preparation, 6, 188 Ferrocenyl-substituted anthracenes, preparation, 6, 189 Ferrocenyl terpyridyl compounds, phenyl-spaced, preparation 6, 188 Ferrocifens... 

Donde, Y., Overman, L. E. High Enantioselection in the Rearrangement of Allylic Imidates with Ferrocenyl Oxazoline Catalysts. J. Am. Chem. Soc. 1999, 121, 2933-2934. 

Scheme 20 Pd-catalyzed oxidative cross-coupling of ferrocenyl oxazoline with simple arenes...

Overman and co-workers carried out extensive studies on Pd(II)-catalyzed asymmetric allylic rearrangement of allylic imidates to form enantioenriched allylic amides. They achieved 97 % ee as the best result by the reaction of the allylic imidate 612 using the cyclopalladated ferrocenyl oxazoline 613 having elements of planar chirality as a catalyst precursor, and discussed the mechanism of the reaction [220]. 

Chiral phenylsulfenyl derivatives of ferrocenyl-oxazoline were used as chiral ligands in the Pd-catalyzed alkylation of 1. The highest ee (98%) of (R)-2 was obtained with 7 as a ligand (Scheme 3). 

Scheme 5.3 Synthesis of planar chiral ferrocenyl oxazolines reported by You.

Figure 11.1 Comparison of bite angles of diphosphine ferrocenyl oxazoline with dppf and BINAP.

A cyclopalladated ferrocenyl oxazoline 3-methoxy-3-pentyl derivative 8.12 was activated in CH2CI2 by deiodination with CFjCOOAg, for example, to give rearranged allylic amide 8.11 in a high yield and a high enantioselectivity from -allylic imidate 8.10, as shown in Eq. (8.1) [16]. 

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