Ammonium ylides, cyclic

Ammonium ylides undergo [l,2]-shift in a manner similar to oxonium and sulfonium ylides. A preferentially migrating group is usually a benzyl group. A sequence of intramolecular formation of ammonium ylide and subsequent rearrangement was extensively explored by West and co-workers in the synthesis of cyclic amines. ... 

The cyclic ammonium ylide/[l,2]-shift approach has been successfully applied by West and Naidu to a key step in the total synthesis of (—)-epilupinine, one of the biologically active lupin alkaloids. Cu(acac)2-catalyzed diazo decomposition of enantiomeric pure diazoketone 160 in refluxing toluene generates a spiro ammonium ylide 161 and 162, which then undergoes [l,2]-shift to give rise to a quinolizidine skeleton as a mixture of diastereomers (95 5) (Scheme Major diastereomer 164 has enantiomeric purity of 75% ee. The partial retention of stereo-... 

The chemistry of ammonium ylides formed from the reaction of cyclic amines with carbenes was found to be dependent on the ring size of the amine.52 For example, treatment of 1-benzylazetidine (104) with ethyl diazoacetate in the presence of a copper (II) catalyst afforded pyrrolidine 106 in 96% yield. This result is consistent with ammonium ylide formation followed by ring expansion. In contrast, treatment of 1 -phenethylaz-iridine (107) under identical conditions gave the fragmentation product 109 in quantitative yield. Similar results were observed for the reaction of aziridine 107 with dichlorocarbene.53 On the other hand, reaction of 1-phenethylpyrrolidine with ethyl diazoacetate in the presence of a... 

Sigmatropic rearrangements of cyclic sulfonium and ammonium ylides have been extensively used in ring contraction and ring enlargement methods. An example is shown in Scheme 55. 

West, F. G., Naidu, B. N. Applications of Stevens [1,2]-Shifts of Cyclic Ammonium Ylides. A Route to Morpholin-2-ones. J. Org. Chem. 

Sulfur and ammonium ylides are susceptible to [2,3]-sigmatropic rearrangements under mild conditions with efficient transfer of chirality, as Trust and Ham-men showed in 1973 [1626], Most of the applications of these rearrangements have been conducted on chiral synthons [1622]. Kurth and coworkers [1627, 1628] have applied this reaction to the synthesis of P-chiral, y,8-unsaturated acids via the rearrangements of cyclic sulfonium ylides 10.21, starting from thiol 10.22 (Figure 10.9). 

Such a reaction course dependence has also been observed in the case of the Rh- or Cu-catalysed three-component reaction of diazoacetates (60) with anilines and p,y-unsaturated a-keto esters (61) (Scheme 8). Depending on the electronic nature of (60) and to a lesser extent on the metal nature of the catalyst (Rh or Cu), the three-component reaction can be directed selectively towards acyclic products (62) or cyclic products (63). The observed regioselectivity has been attributed to the inherent reactivity of the intermediate ammonium ylides (64) according to HSAB principles. 

Glaeske, K. W., West, F. G. (1999). Chirality transfer from carbon to nitrogen to carbon via cyclic ammonium ylides. Organic Letters, 1, 31-33. 

Mageswaran S, Ollis WD, Sutherland lO. Base catalysed rearrangement involving ylide intermediates. Part 9. The rearrangement reactions of cyclic allylic ammonium and sulphonium ylides. 7. Chem. Soc., Perkin Trans. 1 1981 1953-1962. 

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