Rearrangement Polonovski

Lormetazepam (84) is readily synthesized by Polonovski rearrangement of benzodiazepine oxide derivative by heating with acetic anhydride followed by saponification of the resulting rearranged ester.The mechanism of this rearrangement to... 

The pyrimido[5,4-(/J[2]benzazepine 7-oxide 11 (see Section 3.2.1.5.2.) undergoes a Polonovski rearrangement in hot acetic anhydride to yield the 5-(acetoxy)-5//-pyrimido[5,4-r/] [2]benzazcpine 12, which on hydrolysis gives the 5-hydroxy derivative 13.180... 

It will perhaps be recalled from the earlier volume that such N-oxides are prone to undergo the Polonovski rearrangement when treated with acetic anhydride, and that this was illustrated by the formation of oxazepam. It is not surprising that the N-methyl analogue (4) also undergoes this process, and hydrolysis of the resulting acetate gives... 

The one-step Polonovski rearrangement by Kobayashi, which contains the reduction of a similar iminium ion, also supports this prediction. See [16]. 

A simple and efficient procedure for the direct oxidation of C-3 of l,4-benzodiazepin-2-ones, applicable to the preparation of the anxiolytic agents oxazepam and lorazepam, has been developed that represents an improvement over the well-established Polonovsky rearrangement of the N-4 oxide <20060PD1192>. Iodine in AcOH at 65 °C catalyzed acetoxylation in a reaction that involved iodination at C-3 followed by a rapid nucleophilic displacement by KOAc. The liberated HI was recycled to iodine by inclusion of a stoichiometric oxidant, with K2S2O8 being the optimal compromise of cost, availability, and efficiency. 

Replacement of carbon by nitrogen at position 8 of the pteridine ring in MTX and AMT has been accomplished by Srinivasan and Broom [36]. Starting from 6-bromomethylpyrido[3,2-rf]pyrimidine-2,4(lf/,3/f)-dione (III. 115), the xV-oxide was prepared by w-chloroperbenzoic acid oxidation and subjected to Polonovski rearrangement (AcjO-AcOH) to obtain the 6-acetoxymethyl derivative (III.116). Treatment of (III.116) with POCI3 afforded the 2,4-dichloro derivative (III.117), which on being heated at 160-170 °C in liquid ammonia in a pressure vessel was converted to the... 

Vinylogous trifluoromethyl amides. The Potier-Polonovski rearrangement of tertiary amine A(-oxides induced by (CFjCOjjO is frequently followed by trifluoroacetylation. This method is most suitable for the synthesis of (-)-altemicidin. ... 

Polonovsky rearrangement, selenium-mediated 43, 361 Polyarenes, angular 44,869 Polyaryls... 

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