Esterification with 2,2,2-trichloroacetimidate

The Overman esterification is a palladium-catalyzed formation of enantioenriched allyl esters from carboxylic esters with primary allyl imidates. From a mechanistic point of view, it is related to the Tsuji-Trost reaction. It proceeds under quite mild conditions with high enantiomerically access if the COP ([Ti -(5)-2-(4-methylethyl)-oxazolinylcyclo-pentadienyl]-(T] -tetraphenylcyclobutadiene)cobalt) complex is used. For example, Kirsch and co-workers used the Pd-catalyzed Overman esterification " in their approach to 1,3-polyols starting from (Z)-allylic trichloroacetimidates to build up the stereogenic centers. By choice of the required enantiomer of COP-OAc catalyst, every possible diastereoisomer is accessible in high stereoselectivity (Experimental Procedure below). 

Related to the Overman esterification is the Overman rearrangement. The latter allows the conversion of readily available allylic alcohols into allylic amines by a two-step synthesis involving the rearrangement of an allylic trichloroacetimidate to an allylic trichloroacetamide with clean 1,3-transposition of the alkenyl moiety. Although this rearrangement can be thermally driven, addition of palladium salts lower the needed temperature. Chiral ligands such as proline-based diamines would lead to enantioenriched material. ... 

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