Sommelet-Hauser rearrangement salts

An effective method of hexahydrothieno[3,2-c]- and [2,3-c]azocines 146 and 148 syntheses involving a Sommelet-Hauser rearrangement of l,l-dimethyl-2-(2- or 3-thienyl)pyrrolidine salts 145 and 147 under the action of NaNH2 in liquid ammonia has been described (87SC935 Scheme 40). 

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

Benzylic quaternary ammonium salts, when treated with aUcali-metal amides, undergo a rearrangement called the Sommelet-Hauser rearrangement Since 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 aroimd the ring until an ortho position is blocked. ... 

Sommelet-Hauser rearrangement of quaternary ammonium salts ... 

Shirai, N., Sato, Y. Ylide rearrangement of benzyltrialkylammonium salts the improved Sommelet-Hauser rearrangement. J. Org. Chem. 1988, 53, 194-196. 

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... 

Finally, attempts have been made to induce asymmetry in the Sommelet-Hauser rearrangement, but with limited success. Campbell rearranged the optically active sulfonium salt (449) and obtained a mixture of the two Sommelet-Hauser products (450) and (451). The chiral product (451) displayed only low optical activity (Scheme 116). 

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. 

Pine 115> reported the first example of a para-Sommelet-Hauser rearrangement by using a-phenylneopentylammonium salts. The yield of />ara-rearrangement product varies from 0 to 10%, depending on the anion and the solvent. 

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). 

Giumanini et al.7B have studied rearrangements of N,/V-dimethyl-/V-bis(2-thenyl)ammonium salts (39, X = Cl, I). The two products, 40 and 41 (Eq. 16), arise by the Stevens and Sommelet-Hauser rearrangements, respectively it was found that the product ratio depended on the nature of the base, the solvent, and the temperature. The highest proportion of the dithienylmethane 41 (75%) in the product was obtained with sodamide in liquid ammonia at —45°C. 

The pyridodiazocine (27) is formed by Sommelet-Hauser rearrangement of the nicotinium salt (26 R = NH2 X = OMes ) in liquid ammonia in the presence of sodamide.42 The key step in the preparation of nicotine—2—carboxamide (29) is the Minisci carbamoylation of the pyrrolinylpyridine (28).43... 

Sigmatropic rearrangement of the sulfonium ylides from 3-(bromomethyl)thiophene and 2-(bromomethyl)benzo[f)]thiophene has been reported <8980958). Treatment of the bromomethyl compounds with dimethylsulfide gave the sulfonium salts. These were deprotonated (NaOEt or NaH) to generate the ylides. Sommelet-Hauser rearrangement of the ylides gave the products (458) and (459) (Scheme 93). 

In the Sommelet—Hauser rearrangement, a benzyl quaternary ammonium salt reacts with a strong base to give a benzyl tertiary amine, as exemplified below ... 

The mechanism of the [2,3]-migration in a quaternary ammonium salt when treated with strong bases in the classic Sommelet-Hauser rearrangement is well studied, usually in contrast with the related [1,2]-migration observed in the same systems as a consequence of the Stevens rearrangement. Its mechanism was easily clarified by intermediate isolation and labeling experiments. ... 

The transformation of quaternary ammonium salts 1 and sulfonium salts 3 to the corresponding amines 2 and sulfides 4 in the presence of a strong base is known as Stevens rearrangement. The salts are usually obtained by the alkylation of the corresponding amines and sulfides. The competing reaction is the Sommelet-Hauser rearrangement. 

Sigmatropic rearrangements of benzyl quaternary ammonium salts are known as the Sommelet-Hauser rearrangements. The treatment of the benzyl quaternary ammonium salt with sodium amide or other alkali metal amide generates benzyl ammonium ylide. The following examples are illustrative [108, 116-119] ... 

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