Payne rearrangement mechanism

A considerable amount of work was required to optimize the leaving group and avoid racem-ization through a Payne rearrangement mechanism.12 Of course, the Sharpless epoxidation of allyl alcohols is well-known to access these 3-functionalized epoxides. 

The aza-Payne rearrangement and its use as a synthetically valuable equilibration process has been reviewed. Unusual diazadioxabicyclo[2.2.2]octanes (352) have been obtained by the acid-catalysed rearrangement of A -quinazolinonyl- and A -phthalimido-aziridines derived from 3-phenylcyclohex-2-enol. ° A probable mechanism is outlined in Scheme 108. A-Acyl-2,2-dimethylaziridines have been isomerized by sodium iodide into three isomers whose yields appear to depend... 

Unusual triethylamine-catalysed rearrangements of bicyclic endoperoxides derived from substituted cycloheptatrienes have produced383 a variety of products (see, e.g., Scheme 80). Ab initio calculations have shown that energised 2,3-epoxypropoxide anions undergo a degenerate Payne rearrangement in the gas phase via a three-centre mechanism.384 It has been reported385 that treatment of isonitrile epoxides (330) with... 

It is noteworthy that the Payne rearrangement proceeds in a stereospecific manner, providing clean inversion of stereochemistry at the central 2-position as a result of an intramolecular SN2-type mechanism Thus, both configurations at this site are readily available from the same starting material by appropriate control of the rearrangement. 

The isomerization of 2,3-epoxy alcohol 1 under the influence of a base to l,2-epoxy-3-ol 2 is referred to as Payne rearrangement. It involves an equilibrium of the epoxy alcohol 1 with the isomeric 2 and the reaction is stereospecific, proceeding with inversion of configuration at C-2 carbon of the epoxide ring via Sn2 t5q>e mechanism. 

The mechanism of Payne rearrangement involves intramolecular nucleophilic attack by an alkoxide on an adjacent epoxide to form an isomeric alkoxide. This isomerisation results an equilibrium mixture of the two epoxides, the position of which is controlled by the relative thermodynamic stabilities of the two compounds. 

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