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

[Display omitted] ► 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. 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.