Beckmann reaction alkylation

In addition to the Beckmann reaction, the Schmidt rearrangement is used to generate M-alkylated lactams, too. Alkyl azides 231 react with the cyclic ketones (and aldehydes) in the presence of proton or Lewis acids. On running the inter-molecular reactions, in most cases symmetric ketals 230 have been converted... 

The most widely used route to l-benzazepin-2-ones involves the Beckmann or Schmidt reaction of the easily accessible 1-tetralones. Many biologically active compounds described in this review have been prepared on the basis of these reactions they have been fully reviewed [2], In the Beckmann reaction of 1-tetralone oximes, polyphosphoric acid is used as a catalyst-solvent in most instances. Aryl migration generally takes precedence over alkyl migration under these reaction conditions, and various 1-tetralone oximes substituted on the aromatic and/or aliphatic rings can be converted to the appropriate 2,3,4,5-tetrahydro-l//-l-benzazepin-2-ones (51) [5, 20-23, 36, 59, 65, 80, 107-112]. Both courses of the rearrangement occur in some instances, yielding l-benzazepin-2-ones (51) and the isomeric 2-benzazepine-l-ones, probably due to electronic effects of the substituents [90, 113, 114]. 

Beckmann rearrangement-alkylation sequenceOxime sulfonates react with AIR, to form rearranged imines, which are reduced to amines by DIBAH (equation I). The reaction involves selective migration of the R group anti to the oxime sulfonate. 

Into this group fall the named oxidation rearrangement reactions which proceed with carbon-carbon bond cleavage and 1,2-transfer of an alkyl group to a heteroatom, such as the Baeyer-Villiger reaction (discussed in Chapter 5.1, this volume) and the Beckmann reaction (found in Chapter 5.2, this volume) of ketones, as well as the Hofmann reaction/Schmidt reaction/Curtius reanangement of carboxylic acid derivatives. The two examples discussed here involve related reactions of alcohols. 

Beckmann rearrangement, 6, 156 Isothiazole, 3-alkoxy-tautomerism, 6, 145 Isothiazole, alkyl-bromination, 5, 58 Isothiazole, 3-alkyl-5-amino-synthesis, 6, 166 Isothiazole, alkylthio-mass spectra, 6, 142 Isothiazole, amino-azo dyes from, 1, 330 tautomerism, 6, 157 Isothiazole, 3-amino-synthesis, 5, 135 tautomerism, 6, 146 Isothiazole, 4-amino-azo dyes from, 6, 175 diazotization, 6, 158 methylation, 5, 95 quaternization, 6, 158 reactions... 

Substituents R, R at the starting oxime 1 can be H, alkyl, or aryl. The reaction conditions for the Beckmann rearrangement often are quite drastic (e.g. concentrated sulfuric acid at 120 °C), which generally limits the scope to less sensitive substrates. The required oxime can be easily prepared from the respective aldehyde or ketone and hydroxylamine. 

A number of reactions have been explained on the basis of generation of carbocations. The examples include the Friedel-Crafts alkylation and arylation reactions. Besides pinacol-pinacolne rearrangement, Beckmann rearrangement and Wagner-Merwein rearrangement are other examples. 

Beckmann rearrangement of ketoketoximes 288 (R,R = alkyl, aryl) with thionyl chloride unexpectedly afforded 2-aryl(or alkyl)amino-4,6-disubstituted pyrylium salts 289 (equation 124). This reaction is the first example of rearrangement/cyclization involving carbonylic oxygen as terminator. ... 

Another synthetic route via the Beckmann rearrangement, which is promoted by organoaluminum reagent along with alkylation, involves a new stereoselective reduction of the imino group. The starting oxime sulfonate (228) was synthesized from cyclopentanone (226) in three steps Reaction of 226 with 1-undecene in the presence of silver oxide produced the a-undecylcyclopentanone (227) which on successive treatment with hydroxylamine and methanesulfonyl chlo-ride-triethylamine gave the mesylate (228). Treatment of the oxime mesylate... 

Beckmann rearrangement, 4, 809 reactions, 4, 809 toxicity, 1, 136 Thiophene, 2-acyl-alkylation, 4, 777 synthesis, 4, 917 transacylations, 4, 760 Thiophene, 3-acyl-synthesis, 4, 918... 

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