Oximes of Ketosteroids

A possibility of successful application of the Trofimov reaction for the construction of the pyrrole ring bonded to the steroid skeleton has been exemplified by oximes of ketosteroids. 

Under these conditions, the initial ketoxime reacts with acetylene quantitatively to deliver O-vinyl oxime (10%), N-vinylpyrrole (63%), and vinyl ethers of pregnenolone as a mixture of epimers (in 25% total yield). The expected migration of the endocyclic double bond or change in the initial configuration of the steroid function is not observed. The major product, doubly vinylated pyrrole-steroid ensemble, contains steroid, vinyl ether, and N-vinylpyrrole fragments in a one molecule, which ensures that different types of chemical modifications are possible including addition and polymerization reactions. 

When the reaction is carried out under milder conditions (VS C, 5 min.), along with N-vinylpyrrole, the formation of its non vinylated precursor is also observed. 

SCHEME 1.40 Reaction of oxime of A -pregnen-3p-ol-20-one with acetylene. 

SCHEME 1.41 Synthesis of N-vinylpyirole from A -cholesten-3-one oxime and acetylene in the KOH/DMSO system. 

---