Beckmann rearrangement, base catalyzed

Base-catalyzed ring-expansion of benzisoxazolones (217) provides a general route to 2,2-dialkyldihydro-l,3-benzoxazin-4-ones (218) (78CPB549) and the 2,4-dione (220) can be prepared by a Beckmann rearrangement of the oxime (219) (02CB3647). 2-Thion-4-ones (222) are formed from salicylic acids (221) by treatment with triphenylphosphine diisothiocyanate in dichloromethane at -40 °C (78CI(L)806). 

Aly, N. F., Abd-EI Aleem, A. E. A. H., Eltamany, S. H., Abou-Hadeed, K. Base-catalyzed Lessen rearrangement and acid-catalyzed Beckmann rearrangement with N-(arylsulfonyloxy)naphthalene-2,3-dicarboximides. Egypt. J. Chem. 1990, 31,133-140. 

DoleschaU and Seres described a novel base-catalyzed isoxazole-oxazole ring transformation. Treatment of ethyl 5-hydroxy-3-(5-methylisoxazol-4-yl)isoxazole-4-carboxylate 115 with KOrBu/DMF produced ethyl 4-cyano-5-methyloxazol-2-yl acetate 120 in 82% yield. Mechanistically, the authors proposed a base-catalyzed Beckmann rearrangement of 115 via the intermediate ketenimine 118 to account for isolation of 120 (Scheme 1.32). The structure of 120 was confirmed by saponification and decarboxylation to 4-cyano-2,5-dimethyloxazole 121. The generality of this novel rearrangement has not yet been defined. 

The direct ammoximation of cyclohexanone has been performed with hydrogen peroxide and ammonia using a catalyst based on TS-1 (5a). Good performance was obtained, with water as the only side product. EniChem built a 12,000 t/yr demonstration plant (300), which has been running successfully since 1994. Sumitomo built a unit with a capacity of60,000 t/yr in 2003 and both companies plants have operated without any major problems. (232) Sumitomo (301) commercialized its process, in combination with a zeohte-catalyzed Beckmann rearrangement of cyclohexanone oxime... 

An integrated process, which combines catalytic EniChem TS-1, catalyzed direct ammoximation of cyclohexanone and Sumitomo Chemical vapour-phase Beckmann rearrangement, both exploiting MFI based zeolite-like materials, is now industrially used for greener caprolactam production from cyclohexanone without co-producing any ammonium sulfate (Fig. 15.2). ... 

---