Chan rearrangement

The Chan rearrangement is a chemical reaction which was discovered by Tak - Hang Chan. It is a rearrangement reaction of a Acyloxacetat to a 2- hydroxy-3- ketoester.

Overview reaction

In the Chan rearrangement Acyloxacetat is here LDA, rearranged in the presence of a strong base to give 2- hydroxy-3- keto ester:

The radicals are organic radicals. The reaction was successful in the total synthesis of Taxol by Robert A. Holton is used.

Reaction mechanism

The Reaktionsmeachnismus the Chan rearrangement proceeds as follows:

The methyl group of the Acyloxacetats ( 1), marked here in blue is so acidic that they with strong, but not nuclephilen bases such as lithium diisopropylamide ( LDA) can be deprotonated. It is formed due to the deprotonation, the carbanion 2 The nucleophilic attack of the anion thus generated to the neighboring acyl group leads to an intermediate epoxide 3 by electron migration arises from the epoxide ring-opening an alkoxide 4 The acidic workup leads ultimately to a hydroxy group and there is the product 2- hydroxy-3- keto ester 5 the reaction is related to the Darzens Glycidestersynthese.