SOMMELET-HAUSER Ammonium

SOMMELET Aldehyde aynthesis 353 SOMMELET HAUSER Ammonium ylid rearrangement 354... 

SOMMELET HAUSER Ammonkjmyfld rearrangement Rearrangement of quaternary ammonium ylids to aminas by aryl trarafer. 

Benzylic quaternary ammonium salts, when treated with alkali metal amides, undergo a rearrangement called the Sommelet-Hauser rearrangementSince the product is a benzylic tertiary amine, it can be further alkylated and the product again subjected to the rearrangement. This process can be continued around the ring until an ortho position is blocked. ... 

Ammonium ylides can isomerize to (1,2) rearrangement products (Stevens rearrangement) or to (2,3) shift products (Sommelet-Hauser sigmatropic rearrangement) when allyl or benzyl are located on the nitrogen atom. A strong microwave effect is noticed (Eq. 66) [116]. 

Die in Bd.XI/1, S.908 erwahnte Sommelet-Hauser-Umlagerung von Benzyl-trime-thyl-ammonium-Salzen zu Dimethyl-(2-methyl-benzyl)-amin ist fur das Jodid in Lit.3 aus-fiihrlich beschrieben. 

Anders verlauft die durch Fluorid-Ion (Casiumfluorid) bewirkte Umlagerung von Benzyl-dia]kyl-(trimethylsilyl-methyl)-ammonium-halogeniden. Hauptprodukt ist in diesem Fall das durch Desilylierung und Sommelet-Hauser-Reaktion entstandene 2-(Dialkyl-amino-methyl)-l-methyl-benzol(I) neben zumeist sehr geringen Mengen (wenige Prozent) an dem durch Stevens-Reaktion entstandenen l-Dialkylamino-2-phenyl-ethan(II)1,2. 

Rearrangement of benzylic quaternary ammonium salts (Sommelet-Hauser)... 

Fluoride ion-assisted desilylation has been extensively used to create an ylid from a /V-silyl methyl-quaternary ammonium salt. Its evolution to final produces) is variable and Sommelet-Hauser and Stevens rearrangement products were obtained (often as major products) in a ratio that can be shifted from one structure to another very close one, as in examples 1 and 2 dealing with //-benzyl salts.246,366 Differences in the solvents used are not significant because in the first example, HMPA does not reverse the ratio, yields and selectivity being just a bit lower, /so-toluene was proposed as an intermediate in example 1 it might also be the intermediate in example 2. Thus product partition reflects the relative ability of the C-H or the C-C bonds to be cleaved to produce aromatization with proton or a-amine carbocation migration. 

The Sommelet-Hauser rearrangement formally involves the conversion of a benzyl ammonium salt such as 76 into a benzyl amine (e.g., 79). 

SOMMELET - HAUSER AninwnlumyHd rearrangement Rearrangement of quaternary ammonium yHds to aminas by aryt transfer. 

The variants with allylic ammonium and sulfonium ylidesl are well known and correspond to the Sommelet-Hauser and the Stevens rearrangement. Two representative examples are shown in Schemes 50 and 51. 

Another type of ylidic rearrangement, the Sommelet-Hauser rearrangement, was discovered later, in 1937, by Sommelet and studied extensively by Sommelet and by Hauser. This transposition involves the base-promoted rearrangement of non stabilized ammonium and sulfonium ylides. Thus, the ammonium salt (11), when heated with alkali, gave cleanly the substituted diphenylmethane derivative (12 Scheme 5). Wittig found that the dibenzyl ammonium salt (13) reacted with phenyllithium giving two... 

In 1930, Ingold and Jessop reported the rearrangement of the fluorenyl ylide (412).Compound (414) was obtained in what can be considered as the first example of a Sommelet-Hauser reaction (Scheme 106). In 1937, Sommelet described the base-catalyzed transformation of the benzhydryl ammonium bromide (415) into the substituted benzylic amine (416 Scheme 107, equation a)." Wittig found later that reacting the salt (417) with phenyllithium produced two amines, (418) and (419). The former is derived from a Sommelet-Hauser 3,2-rearrangement, whereas the latter comes from a Stevens... 

Several limitations of this base-promoted rearrangement are worthy of mentioning (a) when structurally feasible, both Stevens and Sommelet-Hauser reactions will compete (b) certain substituents on the aromatic ring, e.g. Cl, CN, NO2, prevent the formation of the ylide and no rearrangement takes place (c) if a p-hydrogen is present on the ammonium salt, elimination becomes yet another undesirable side reaction, In an attempt to overcome these limitations, Sato has utilized the fluoride-induced desilylation of... 

Sommelet-Hauser rearrangement The rearrangement of a benzyl quaternary ammonium salt, C6H5CH2N+R3X-, when treated with an alkali metal amide to give the orthomethylbenzyl tertiary amine, o-CH3C6H4CH2NR2. The tertiary amine may subsequently be alkylated, and the reaction... 

Sommelet-Hauser rearrangement. Rearrangement of benzyl quaternary ammonium salts to orr/to-substituted benzyldialkylamines on treatment with alkali metal amides. 

In the presence of NaNH2 benzylic quaternary ammonium salts generally lead to the Sommelet-Hauser rearrangement (refs. 90, 92-104). An ortho alkylation takes place via an exomethylene intermediate. If the two ortho and ortho positions are methylated, the methylene compounds can be isolated (refs. 92, 93). The first anion formed in this reaction can be trapped at a very low temperature (-80 °C) in an aldol reaction for example (ref. 103). At -30°C the isomerization and the rearrangement occur (Fig. 16). 

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