| Abstract: | Nucleophilic Substitution Reactions of Hydroxysteroids using Triphenylphosphane/diethylazodicarboxylate Nucleophilic substitution reactions by means of the title reagent on various more or less hindered steroid alcohols with suitable nucleophils in benzene is described. It was not possible to run this substitution process in the hitherto used solvent THF. Cholestan-3α-ol ( 1 ) was transformed to the 3β-substituted products 3β-benzoyloxy-cholestane ( 1a ) and 3β-azido-cholestane ( 1b ). Testosterone ( 2 ) affords with the corresponding nucleophils after short heating in benzene the inverted 17α-substituted products 3a, 3b and 3c . Analogously the 17α-azido-derivative 5a arises from 17β-hydroxy-androst-3-on ( 4 ). In the presence of a ketogroup in the substrate a competitive reaction can occur as it is shown in the case of cholestan-3-on ( 6 ): the products are the en-hydrazo-dicarboxylate-steroids 7a and 7b . The sterically very hindered 11α-position in 11α-hydroxy-4-pregnen-3,20-dion ( 8 ) can be transformed also to the 11β-azide 9a . The substitution of a 6 β-hydroxy group in androstane-3β, 6β, 17β-triol-3,17-diacetate ( 10 ) to the 6α-azide 11a affords the elimination product 12 as main component. Trans-diaxial vicinal diols such as cholestane-2β,3α-diol ( 13 ) give a mixture of the α- and β-oxiranes 14a and 14b . |
