Quantum anomaly is a powerful tool to study quantum field theories. Anomalies exist for discrete symmetries and they are now focus of attention in various fields. For example, they are related to symmetry protected topological phases (SPT) or can put constraints on QCD at theta = \pi. In this talk I will consider a global anomaly for center of Lie groups in the Wess Zumino Witten model and its relation to boundary conformal field theory.