The dibromo ketones (u/I)-8b react with sodium azide to afford the a, a'-diazido ketones (u/l)- 9b, which are reduced to the diastereomeric a, a'-diamino ketones (u/1)-11 b. The hydrochlorides of the latter are separated through fractionating crystallization yielding pure (1)-11 b. 2 HCl (de> 99%) and (u)-11 b. 2 HC1 having de of 60%. Oxidation of (u)-11 b and (1)-11 b with sodium hypobromite produces the 4-pyrazolones cis-6b (de= 60%) and trans ...
