There have been a number of recent podcasts about Putin, discussing how hard it would be to pry him out from within. Many believe it would require the Soloviki to take action in some way; specifically some combination of Patrushev, Bortnikov, Naryshkin, and Shoigu. Many of these guys are either old KGB cronies of Putin's dating back to the 70s and/or (in the case of Patrushev) corrupt St. Petersburg conspiracy theorists who are actually fueling Putin's imperialist views instead of pushing back against them. Putin has also managed to diversify away from the old KGB crowd incase they decide to move against him but putting an outside like Shoigu in charge of the military. This would make it very hard to plot a successful coup against him because not all of the necessary players would be sufficiently unified to keep it a secret for long enough to pull it off.
But circling back to sanctions, these are definitely the guys who need to be targeted (along with all family members remotely close to them) instead of the the usual caviar slurping Oligarchs with mega yachts who have little sway to influence Putin's behavior.