Cobalt oxazoline palladacycle

Nomura H, Richards CJ (2007) An investigation into the allylic imidate rearrangement of trichloroacetimidates catalyzed by cobalt oxazoline palladacycles. Chem Eur J 13 10216-10224... 

Prasad RS, Anderson CE, Richards CJ, Overman LE (2005) Synthesis of tert-leucine-derived cobalt oxazoline palladacycles. Reversal of palladation diastereoselectivlty and application to the asymmetric rearrangement of N-aryl trifluoroacetimidates. Organometallics 24 77-81... 

The catalysed rearrangement of allylic imidates including allylic trichloroace-timidates such as (12.12) has been reported by Overman using palladium catalysts with some of the highest ees obtained using the cobalt oxazoline palladacycle (12.13). 

Cobalt Oxazoline Palladacycles (COPs) are organocobalt-palladium complexes which catalyse the asymmetric rearrangements of non-chiral allylic trichloroacetamidates with very high enantiomeric selectivity (>90%) to provide chiral allylic amines [it is an aza-Claisen rearrangement, The Overman Rearrangement Overman Carpenter Org React 66 2005, Kirsch, Overman and Watson J Org Chem 69 8101 2004] and in the presence of phenols stereospecific cross-couphng also occurs to provide chiral phenoxyallyl ethers with veiy high (>90%) enantiomeric selectivity [Kirsch, Overman and White Org Lett 9 911 2007, Overman Carpenter Org React 66 2005]. 

A recent synthesis of (+)-z5o-6-cassine makes use of enantioselective Overman rearrangement of imidate 74. Treatment of 74 with chiral cobalt oxazoline palladacycle (5)-COP-Cl vide supra) in dichloromethane gives rise to the iV-trichloroacetyl derivative 75 in good yield. This asymmetric reaction installs the absolute stereochemistry of C-6 in (+)-fso-6-cassine. ... 

Sigmatropic Rearrangement of Trichloroacetimidates The development of the asymmetric palladium(II)-catalyzed [3,3]-sigmatropic rearrangement of trichloroacetimidates has proven to be a powerful method for the generation of chiral amines from achiral allylic alcohols [12]. In particular, the cobalt oxazoline palladacycles, such as COP-Cl (4), have been shown to be particularly efficient for this transformation (Scheme 5.1) [13]. 

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