Boron Beckmann rearrangement

A variety of ketoxime ethyl carbonates undergo the Beckmann rearrangement in excellent yields (74-99%), upon treatment with 1 equivalent of boron trifluoride etherate at room temperature (equation 91). 

Hoffenberg, D. S., Hauser, C. R. Dehydration or Beckmann rearrangement of aldoximes with boron... 

Acylation of thiochromanones with boron trifluoride and acetic anhydride readily affords (92), which may be elaborated into (93) (equation 36) (79CJC3292), while conversion of the keto function to an oxime (94) permits the formation of the palladium complex (95) as a first step towards functionalization of the aromatic ring (equation 37) (78BCJ3407), or ring expansion by Beckmann rearrangement (equation 38) (76JCS(P1)2343). 

Aniikumar, R., Chandrasekhar, S. improved procedures forthe Beckmann rearrangement the reaction of ketoxime carbonates with boron trifiuoride etherate. Tetrahedron Lett. 2000, 41, 5427-5429. 

The Beckmann rearrangement of cyclohexanone oxime was tested over phosphates of boron with compositions varying in the range B/P = 0.4-1.6. Catalysts with excess of boron had very high activity whereas catalysts with excess phosphorus had no activity [8]. AlP04-Ti02 catalysts were more lactam-selective than AIPO4 catalysts [9]. 

E-Caprolactam is an important starting material for the production of nylon-6. It is synthesized by the Beckmann rearrangement reaction of cyclohexanone oxime catalyzed by a solid acid catalyst. Many solid acid catalysts, such as mixed boron oxide [1-3], Si02-Al203 [4,5], metal phosphates [6-8] and moclified zeolites [3,9-12], are reported to catalyze the cycdohexanone oxime rearrangement. The acid function of the catalyst is essential to effect the rearrangement reaction. 

Fomi, L., Fomasari, G., Tosi, C., Trifirb, F., Vaccari, A., Dumeignil F., and Grimblot, J. Non-conventional sol-gel synthesis for the production of boron-alumina catalyst applied to the vapour phase Beckmann rearrangement. Appl. Catal. A Gen. 2003, 248, 47-57. 

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