TIFFENEAU Aminoalcohol Rearrangement

The stereochemistry of cyclic primary amines or aminoalcohols dramatically influences the product distribution of their respective Demjanov and Tiffeneau-Demjanov rearrangements. P. Vogel and co-workers have studied the ring-expansion of 2-aminomethyl-7-oxabicyclo[2.2.1]heptane derivatives upon treatment with nitrous acid. Some of their findings are shown below. ... 

It should be noted that the 2-oxazolines are connected directly with enamides, being their products of cyclization on the one hand ", as well as being the heterocyclic precursors of W-acylenamines on the other . However, it is no less important that the 2-oxazolines are cyclic derivatives (and precursors also) of the 1,2-aminoalcohols. In essence, the reactions 117 122 (equation 41) and 125- 128 (equation 43) are the transformations of ketones to 1,2-aminoalcohols, i.e. they are the reversal of one of the pinacol rearrangement variants, i.e. the Tiffeneau and MacKenzie reactions . These transformations which proceed via the iV-acyliminium intermediates 118, 126 are examples of a real retropinacol rearrangement according to structural, functional and redox features (see Section III.B.3). 

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