Action des composes organomagnesiens sur les pyrones-2-VIII : Identification des intermediaires reactionnels

The correlation between the structure of the intermediates and final products during the reactions of the methylmagnesium iodide with several 2-pyrones could be established by intercepting the intermediates before hydrolysis using methyl iodide in HMPT. In this way it was possible to show that these reactions either involve the formation of the dihydropyranol or the unsaturated E-ketol depending on the stereochemistry of these intermediates. The presence of cyclic magnesium alkoxides was established so proving the existence of a tautomeric “ring-chain” equilibrium before hydrolysis.