Beckmann rearrangement of OTDP salts of oximes of aromatic ketones and synthetic applications

Reaction between tris(dimethylamino)-phosphine, carbon tetrachloride and ox imes of ketones leads to the corresponding Oximoxy-Tris-(Dimethylamino)-Pho sphonium salts (OTDP salts), which are isolated in the form of hexafluoroph osphates. These salts are solid and stable except if they are completely de hydrated. Their solutions, in non polar solvents like CHCl3, give Beckmann rearrangement at room temperature. The kinetics and mechanism have been stu died by NMR. We have defined the conditions of trapping of the cationic int ermediates formed in the rearrangement, leading to an effective synthesis o f amidines and an access to a glycoside structure using the hemiacetalic hy droxyl group of sugar as nucleophile. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.