The use of readily available 1-aryl-3-arylidenepyrrolidine2,5-diones in high yielding direct diazo-transfer reactions and subsequent involvement of the resulting diazo compounds in Rh-II-catalyzed O-H, S-H, and N-H insertion reactions delivered 4-substituted 1-aryl-3-arylidenepyrrolidine-2,5-diones of defined regiochemistry and geometrical configuration. These products are intended to be studied as Michael acceptors capable of inhibiting thioredoxin reductase, a promising cancer target.