The ammonioamidates (7) and ( 11) undergo [1,2] rearrangement (R3 = CH,Ph) and competing [1,2] and [3,2] rearrangements (R3 = allyl). The rates of the [1,2] and [3,2] rearrangements of the cinnamyl ammonioamidates (1 1 a), (1 1 b), (1 1 d), and (1 1 g) show similar dependence on the nature of the substituent X. The rate of the [1,3] rearrangement of the reaction products (14b), (14d), and (14g) is relatively insensitive to substituent effects, suggesting that the rates of ammonioamidate rearrangements are largely controlled by conjugation between the group X and the NCO system. The [1,2] and [3,2] rearrangements of the cinnamylammonioamidate (1 1 d) show moderate and similar dependence upon solvent polarity suggesting that the transition state for both reactions has considerable dipolar character. The apparent intramolecularity of the [ 1,2] and [3,2] rearrangements of the cinnamylammonioamidate (1 1 e) as estimated by isotopic mixing methods is decreased by isotopic scrambling in the ylide due to radical recombination to give ylide (1 1 I) in addition to products ( 131) and ( 141). If allowance is made for this effect the [3,2] rearrangement appears to be largely, or even entirely, intramolecular and the [I ,2] rearrangement shows intermolecularity comparable with that found for the rearrangements of analogous ammonium ylides under similar reaction conditions. * A useful, but perhaps over simple, analogy is provided by the conjugation energy of the NCOX system as indicated by rotational barriers about the N-COX bond of amides.I6

Das durch HBr‐Abspaltung aus dem entsprechenden Ammoniumbromid erhaltene Ylid ( la) lagert sich in einer ein‐ bis vielstündigen Reaktion zum Produkt (IIa) um, das sowohl aus einer [l,2]‐ als auch aus einer [3,2 I‐Umlagerung hervorgehen kann.