Catalyst- and excess reagent recycling in aza-Michael additions.

16α-Azolyl-pregnenolone derivatives were prepared 2-butyl-1,1,3,3-tetramethylguanidine (-Bu-TMG) catalysed aza-Michael addition of 16-dehydropregnenolone (16-DHP) carried out in [bmim][BF]. The application of the guanidine base and the imidazolium ionic liquid made it possible to recycle not only the catalyst/solvent mixture but also the excess of the N-heterocyclic reagent. By the introduction of CO at the end of the reaction, both the guanidine base and the unreacted (excess) reagent could be converted into ionic species that remained dissolved in the ionic liquid phase, while the steroid components were extracted with an apolar solvent.