Rearrangement Of Ammonium Ylides Research Articles

Controlling Selectivity by Controlling the Path of Trajectories.

Consideration of the role of dynamic trajectories in [1,2]- and [2,3]-sigmatropic rearrangements suggests a counterintuitive approach to controlling the selectivity. In our hypothesis, [2,3] selectivity can be promoted by reaction conditions that thermodynamically disfavor the [2,3] rearrangement step and thereby make the transition state later. The application of this idea has led to a successful prescription for dictating the selectivity in Stevens/Sommelet-Hauser rearrangements of ammonium ylides. A combination of kinetic isotope effects, crossover experiments, and computational dynamic trajectories support the idea that the selectivity is controlled through control of the path of trajectories.

ChemInform Abstract: Rearrangements of Nitrile‐Stabilized Ammonium Ylides

AbstractReview: [57 refs.

Rearrangements of Nitrile-Stabilized Ammonium Ylides

Rearrangements of nitrile-stabilized ammonium ylides are useful reactions for the construction of alkylamines, nitrogen heterocycles, or carbonyl compounds. In spite of their attractive synthetic potential, they are much less frequently used than rearrangements of ammonium ylides either carrying charge-stabilizing carbonyl groups or being devoid of additional stabilization of the negative charge. This review focuses on different classes of rearrangements of nitrile-stabilized ammonium ylides as well as their application in synthetic organic chemistry. 1 Introduction 2 [1,2]-Stevens Rearrangements 3 [2,3]-Sommelet–Hauser Rearrangement 4 [2,3]-Stevens Rearrangements 5 Competitive [1,2]-, [2,3]-, and [1,4]-Rearrangements 6 [1,4]-Rearrangements Involving Ring Expansion 7 Summary

Sigmatropic Rearrangement of Ammonium Ylides—Key Step in the Synthesis of Methyl 2-Formylphenyl Acetate

N-Cyanomethyl-N,N-dimethyl-N-(α-methoxycarbonyl)benzylammonium salts 5 were synthesized and treated with different base/solvent systems, giving the products of sigmatropic rearrangements [2,3] 7 and [1,2] 8. In reactions carried out in liquid ammonia, [2,3] rearrangement definitively prevailed. Pure 7(or mixture of 7 and 8) were deprotected to afford methyl 2-formylphenyl acetate (9) in good yield.

A stable intermediate in the Sommelet–Hauser rearrangement of 1-methyl-2-phenyl-piperidinium 1-methylides: the improved Sommelet–Hauser rearrangement

Reaction of 1-methyl-1-(trimethylsilyl)methyl-2-(substituted phenyl)piperidinium iodides (2) with caesium fluoride gave high yields of 2-methyl-1,3,4,5,6,11a-hexahydro-2H-2-benzazonines (4) which are regarded as unstable intermediates in the Sommelet-Hauser rearrangement of ammonium ylides (3) to 2-methyl-2,3,4,5,6,7-hexahydro-1H-2-benzazonine derivatives (5).

Base catalysed rearrangements involving ylide intermediates. Part 18. Competing [1,2], [1,3], and [1,4] rearrangements of ammonium ylides

The [1,2] rearrangements of acyl stabilised ammonium ylides are, in several cases, accompanied by competing [1,3] rearrangements and in one case by a [1,4] rearrangement. For examples involving migrating benzyl or phenylethyl groups the mechanism of these rearrangements has been studied. Thus the competing [1,2], [1,3], and [1,4] rearrangements of the ylide (12) are largely intramolecular, but the intermolecularity is as high as 28% for the [1,2] and [1,3] rearrangements and 14% for the [1,4] rearrangement in methanol at 55 °C. The competing [1,2] and [1,3] rearrangements of the optically active ylide (29a) give products with predominant retention of the configuration of the migrating phenylethyl group, but the intramolecular stereoselectivity of the [1,2] rearrangement is significantly greater than that of the [1,3] rearrangement. These results are consistent with a radical pair pathway for all three modes of rearrangement. Suitably substituted acyl stabilised allylammonium ylides (55) rearrange by competing [1,2], [1,3], [3,2], and [3,3] processes.