Sommelet reaction Hauser rearrangement

In a base-catalyzed ring expansion route to 1,2-diazocines, Sommelet-Hauser rearrangement of the A-amino derivative of nicotine (22) using sodium in ammonia afforded pyrido-l,2-diazocine 23. The reaction was regiospecific, i.e., no isomeric 24 was detected (82H1595). 

Modification of the stereochemistry of the reaction has been demonstrated by studying desilylation reaction of cis- and mmy-2-methyl-1 -(phenyl)isoindolinium 2-methylides. It has been established that cw-isomer leads preferentially to the Sommelet-Hauser rearrangement product (eight-membered ring formed) whereas the trans-isomer leads predominantly to the Stevens rearrangement product.374... 

The Sommelet-Hauser rearrangement has rarely been used as a tool in organic synthesis and then only for very special systems [54], The reason is undoubtedly that the Hofmann elimination and the dealkylation reaction of quaternary nitrogen atoms are in direct competition with the ring expansion reactions of these substrates. 

Lactams participate in a number of ring enlargement reactions of different types. Because of the classification in this review they are described at other places too e.g. Sommelet-Hauser rearrangement (Chapter V3). 

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... 

Tertiary amines are aminated to give unstable hydrazinium compounds, for example (54), is suggested by the formation of hydrazine (55) via a Sommelet-Hauser rearrangement on reaction of (51) with iV,jV-dimethylallyl amine (Scheme 11) <91S327>. 

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). 

Some heteroaromatic IV-imines possess structural elements analogous to those compounds which undergo Sommelet-Hauser rearrangements. Nevertheless, only few intramolecular rearrangement reactions of heteroaromatic IV-imines are known. 

A Sommelet-Hauser rearrangement of the initially formed sulfonium ylide 13 is a key reaction step. This brings about the required ortho-linkdigQ with the arene, which results in the formation of the o-aminobenzyl carbonyl compound 14. 

---