Benzaldehyde oxime, Beckmann rearrangement

A simple montmorillonite K 10 clay surface is one among numerous acidic supports that have been explored for the Beckmann rearrangement of oximes (Scheme 6.27) [54]. However, the conditions are not adaptable for the aldoximes that are readily dehydrated to the corresponding nitriles under solventless conditions. Zinc chloride has been used in the above rearrangement for benzaldehyde and 2-hydroxyacetophe-none, the later being adapted for the synthesis of benzoxazoles. 

Barium thiocyanate, 118 Base catalysis, 34 in acylations, 47, 48 of chelate formation, 95 of clevage, 128 of cydization, 127 in hydrolysis, 115 Basicity, of 2-aminothiazole, 90 of 2-imino-4-thiazolines, 124 Beckmann rearrangement, of oxime, 16 Benzaldehyde, with alkyl-acetamidothi-azole, 46... 

Barton reaction, 398, 446 Beckmann rearrangement of oximes, 325, 343-345 Benzaldehyde, 178 Benzoates, pyrolytic elimination,... 

Treatment of benzaldehyde oxime ether (166) with butyllithium (pentane/-10 C) demonstrates the complexity of the reaction (Scheme 32) as the desired alkoxyamine (167 R = Bu) is accompanied by other oxime-derived side products" (entry 1, Table 12). Selectivity is reagent/solvent dependent as allyl Grignard (ether)," allylzinc bromide (THF)," and butyllithium (THF)" treatment produce predominantly amine (171 R = allyl) (the Beckmann rearrangement derived product), alkoxyamine (167 R = allyl) (the oxime addition product) and ketone (169 R = Bu) (the nitrile-derived pro ct), respectively (entries 2-4, Table 12). 

Butler, R. N., O Donoghue, D. A. Direct detection of intermediates and synthetic applications of the reaction of thionyl chloride with oximes of substituted acetophenones and benzaldehydes Beckmann rearrangements. J. Chem. Res., Synop. 1983,18-19. 

The complex formed with BF3-OEt2 and Epichlorohydrin in DMF acts as a catalyst for the Beckmann rearrangement of oximes. Cyclohexanone, acetaldehyde, and syw-benzaldehyde oximes are converted into e-caprolactam, a mixture of iV-methyl-formamide and acetamide, and Al-phenylacetamide, respectively. 

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