Key TakeawaysDeutsche Bank upgraded Celanese stock to "buy," saying yesterday's big selloff was overdone.The bank's analysts called the chemical supplier's problems "painful but transitory."The analysts called Celanese a "high-quality" company. Their price target calls for appreciation, but is below the Street's consensus. Shares of Celanese (CE) dropped 26% yesterday. At least one Wall Street analysts says it's time to get back on board. The chemical supplier's shares, which plummeted yesterday after a di ...