Hauser rearrangement

Another indole/oxindole synthesis achieves the critical ortho-substitution by Sommelet-Hauser rearrangement of an anilinosiilfonium ion intermediate. Use of P-thioketones (G = R, an alkyl group) generates 2-substituted indoles, whereas P-thioesters (G = OR) lead to oxindoles. In each case, a 3-thio substituent must be removed by desulfuri2ation. 

The Somme let-Hauser rearrangement competes when Z is an aryl group (see 13-22). Hofmann elimination competes when one of the R groups contains a p hydrogen atom (17-6 and 17-7). 

Recently, N-aryl sulphimides were found to react with diphenyl cyclopropenone and its thione226 giving rise to imines 331 and 332. Apparently attack of the sulph-imide at cyclopropenone C3 gives rise to intermediacy of a ketene 330, which is consumed by an excess of the sulphimide (to give 331 after hydrolysis) or by its Somme-let-Hauser rearrangement (to give 332) ... 

Transformation of allyl ethers into homoallylic alcohols by treatment with base. Also known as Still-Wittig rearrangement. Cf. Sommelet-Hauser rearrangement... 

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 chlorosulfonium compounds can also be used for the synthesis of oxindoles, the stable tautomeric form of 2-hydroxyindoles. The a -methylthio ketone is replaced by ethyl methylthioacetate and the products of the Sommelet-Hauser rearrangement are cyclized to 3-methylthiooxindoles. The methylthiooxindoles are reductively desulfurized with Raney nickel (equation 102) (74JA5508). 

We have mentioned previously as a stable ylide dimethyl sulfonium fluorenide (see Section 2.9). It yielded the first example (1938) of a [2,3] sigmatropic rearrangement of a sulfur ylide [505, 506] (Sommelet-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). 

Based on a previous study by Miller,289 a series of iV-benzyl-MSMA chlorides or bromides have been treated with a base and/or a nucleophile. For example, in the presence of the amide anion, the trimethylsilyl derivative yields iV,/V-dimethyl-2-methyl-a-(trimethylsilyl)benzylamine (a Sommelet-Hauser rearrangement product) as the main... 

The presence of an alkyl group or not on the benzylic carbon atom has little influence on the result (example 2). The Sommelet-Hauser rearrangement product is not obtained as its exo-1 -alkylidene-cyclohexadi-2,4-ene precursor is stable (allowed typical cyclohexadiene chemistry) and isolable as a 1 5 mixture (35% yield) of the two stereoisomers. Styrene is also obtained as the major product (50%) whereas the Stevens product is formed in trace amounts. Triene A is converted quantitatively into 2-ethylbenzylamine under treatment with diluted KOH at 60 °C for 0.5 h in ethanol.368... 

An illustration of the Sommelet-Hauser rearrangement is the synthesis of 2-methyl-2,3,4,5,6,7-hexahydro-lH-2-benzazonine from 2-phenyl-l-[(trimethylsilyl)methyl]-piperidine in good yield, where a stable trienic intermediate aromatized only after treatment with base for 24 h at room temperature.369... 

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... 

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