"The report said the financial transactions were enabled by the secrecy and anonymity with which the art market operates and it called for tighter rules to force greater transparency." (UPDATED)

New York Times: Senate Report: Opaque Art Market Helped Oligarchs Evade Sanctions.

UPDATE: A deep-dive from Tim Schneider, which ends up here: "The Senate report shows how complicated it can be to unmask the end client when shell companies, anonymous trusts, and legit-on-the-surface intermediaries are involved. Intense due diligence also conflicts with the volume and speed of business they need to do to break even, let alone turn a profit."