Prototropic Isomerizations and Rearrangements

Metal catalysis is a general method for promoting prototropic isomeriza-tions and to reach the thermodynamic equilibrium between positions and/or geometrical unsaturated isomers. 

Example one step of a tetrahydrofuranecarboxaldehyde synthesis involves a rhodium catalyzed isomerization of the double bond in a dioxacyclohep-tene ring  

Such a prototropic isomerization has also been applied in an original method for protecting hydroxy groups in carbohydrate chemistry. 

Rearrangements As 7r-allyl Pd species are easily formed from allyl acetates, 1,3-migration of an acetoxy group in allylic compounds is readily carried out in the presence of Pd catalysts (in the absence of added nucleophiles). 

Moreover, Pd species promote sigmatropic rearrangements, mainly of the 3,3-type, particularly when heteroatoms are involved [44]. 

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