Beckmann-type fragmentation

Aldoximes are among the most suitable starting materials for the synthesis of nitriles. A plethora of reagents [222-227] has been introduced for this Beckmann-type fragmentation (see Beckmann reaction, under Section 9.3.2.2). Among these are acetic anhydride [223], metal salts [224] or other metal catalysts [225], selenium dioxide [226] and Burgess reagent [227]. In the presence of hahde derivatives [228] or metal salts [229] aldoximes can also be oxidized to nitrile oxides. 

The key stage of the synthesis to prepare 100 g amounts of a novel anthelmintic drug 500 from the metabolite VM-44866 (499) was a Beckmann-type oxime fragmentation (equation 217). A two-step reassembly of the spiroketal moiety efficiently produced the target molecule (30% yield of complete sequence in a 0.5 kg scale). 

Kita, Fujioka and co-workers reported that the reaction of a-alkoxycycloalkanone oxime acetates sueh as 35 with organoaluminum reagents caused Beckmann fragmentation and subsequent carbon-carbon bond formation to give different (o-eyano-a-alkyl (or alkynyl) ethers of type 36 in high yield, as illustrated in Sch. 22 [45]. 

The complete paper on the synthesis of samandarine-type alkaloids (6, 401) by Beckmann fragmentation has been published. ... 

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