The 8.5cm F2 Sonnar- the barrel "should" just unscrew, using a rubber pad. The rear group unscrews from the barrel once it is out. Getting the glass out should not be hard, unless someone has botched a prior "repair".
I tried this once- the answer was no, the shape of the back of the barrel was changed and it would not fit. ALSO- the J-9 focus is too far off for a Leica standard camera. The best option is to use an Amedeo adapter with the Contax mount lens. That is what I do.Is mounting the optical block into a Jupiter-9 barrel a possibility?