The targeted degradation of proteins by reprogramming E3 ligases with bifunctional small molecules is an exciting area of chemical biology because it promises a set of chemical tools for achieving the same task as siRNA or CRISPR/Cas9. Although there are hundreds of E3 ligases in the human proteome only a few have been shown to be reprogrammable to target new proteins. Recently various arylsulfonamides were shown to induce degradation of the splicing factor RBM39 via the RING type E3 ligase CRL4 DCAF15 . Here we identify the arylsulfonamide most amenable to chemical modifications and demonstrate its behaviour in bifunctional reprogramming.