Imidazoles oxadiazine synthesis

A related synthesis leads to 4-trifluoromethylimidazoles. Trifluoracetylated aldehyde dimethyl-hydrazones thermally rearrange to give mixtures of oxadiazines and imidazoles. Higher temperatures and more polar solvents suppress formation of the six-membered rings, while solvent variation also alters the proportions of the imidazole regioisomers. In carbon tetrachloride the major product is... 

When the approach in Scheme 67 was attempted for the synthesis of alboinon 381 (a natural product from marine organism Dendrodoa grossularia), it was discovered that the oxadiazine system does not survive even the mildest of the SEM deprotection conditions. Therefore, an alternative method, starting from imidazole, via a Baeyer-Villiger approach was improvised <1997T2055> (see Section 9.09.9.4). 

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