i’ve found these. i am not sure about absolute correct dates, so please double check:
Bank Julius Bär CEO Boris Collardi: Nov. 27, 2017 ==switched to „Pictet Bank“
Steinhoff CEO Markus Jooste: Dec. 05, 2017
Novartis Oncology CEO Bruno Strigini: Dec. 14, 2017
Aida Minerals Corp. CEO Robin S. Tolbert: Dec. 17, 2017
Helvetia (Insurance) President Board of Directors Pierin Vincenz: Dec. 18, 2017
ProSiebenSat.1 CEO Thomas Ebeling will leave earlier: Feb 22, 2018