Mercuric trifluoracetate (0.2-0.6 equiv) is shown to be an effective catalyst for equilibrating , -dimethylcarbamic esters of allylic alcohols at room temperature. Acyclic, cyclic, terpene, and steroid examples are reported. Yields are uniformly high (Tables I-III), and side reactions typically encountered in acid-catalyzed isomerizations are not observed. This method for allylically transposing oxygen functionality would appear to be the method of choice in cases where "classical" acid-catalyzed methods fail. When an excess of mercuric trifluoroacetate (1.1-3.0 equiv) is employed, a significant amount of the allylic carbamates is bound as covalent adducts. This observation forms the basis of a method for achieving contrathermodynamic allylic isomerizations (eq 3). The method is limited in scope and preparatively significant contrathermodynamic isomer enrichments were obtained only with the 2-alken-l-yl carbamates 3 and 18. Future applications of this methodology are discussed in terms of the semiquantitative model of Scheme I. The mechanism of the mercury (Il)-catalyzed allylic rearrangement is considered in detail. An ionization-recombination mechanism is ruled out by (a) the inability to detect allyl cation intermediates, (b) the formation of rearranged carbamates rather than amines, and (c) the inversion of the allyl fragment which is observed in the catalyzed rearrangement of thionocarbamate 27. The experimental observations are most consistent with a mechanism (eq 8) in which the mercuric catalyst interacts with the carbon-carbon bond to promote an intramolecular cyclization to yield a 1,3-dioxanium ion intermediate. We suggest the name cyclization-induced rearrangement for this catalysis mechanism (eq 6). More general implications of the cyclization-induced rearrangement mechanism are also considered.Besides being one of the focal points for the evolution of mechanistic organic chemistry, the allylic rearrangement of allylic alcohols and their derivatives occupies a position of some importance in synthetic organic chemistry.3 Often the more readily accessible allylic isomer is not the desired one. If in such cases, the desired isomer predominates at equilibrium, or is favored under kinetically controlled conditions, a synthetic strategy involving an allylic rearrangement may be utilized.

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Hg(II)‐trifluoracetat (HgAz) ist ein wirksamer Katalysator für Umlagerungsreaktionen (Gleichgewichtsreaktionen) allylischer Carbamate.