Synthesis of ferrocene-labeled steroids via copper-catalyzed azide–alkyne cycloaddition. Reactivity difference between 2β-, 6β- and 16β-azido-androstanes

Copper-catalyzed cycloaddition of steroidal azides and ferrocenyl-alkynes were found to be an efficient methodology for the synthesis of ferrocene-labeled steroids. At the same time, a great difference between the reactivity of 2β- or 16β-azido-androstanes and a sterically hindered 6β-azido steroid toward both ferrocenyl-alkynes and simple alkynes, such as phenylacetylene, 1-octyne, propargyl acetate and methyl propiolate, was observed.

Figure optionsDownload as PowerPoint slideHighlights
► New ferrocene labeled steroidal triazoles were produced.
► Products were obtained by a cycloadditon of steroidal azides with ferrocenyl alkynes.
► A great difference in the reactivity of 6β- and 2β-/16β-azido–androstanes was observed.
► The same difference was observed in the cycloaddition with simple alkynes.
► The reactivity difference was explained using computational methods.