Anton Philips made great efforts to protect his jewish staff claiming them required to keep up the quality of production - in a similar way to Oscar Schindler.
Siemens as it exists today is a post war amalgamation of Siemens & Halske, a German company and Siemens Brothers Ltd. a British company founded in the late 1800s by Sir Charles Siemens who were very much on our side during WW2 and a major contractor to the Brits and Americans.
However business is complex, BASF, Bayer, AGFA, Sanofi and GAF, all major chemical and pharmaceutical companies are the successors to the Nazi administered IG Farben chemical company, who were the distributors of Zyklon B.
The manufacturers of Zyklon, Degesch, still exist as Detia Degesch, a major player in pest control - Zyklon itself, which was a very useful insecticide was produced under the same name until the late 70s, then as Uragan D2 (same product, different name) by another manufacturer until 2024 when it was banned due to being rather too dangerous.
The brand name persisted in the US into at least the 50's under the licencee American Cyanamid Corporation.
Of course you have to put yourself in the shoes of some of the businessmen in the midst of the situation - take J.A.Topf & Sons of Erfurt in Germany, at the time a leading manufacturer of crematorium furnaces. If the SS rocked up and said we would like you to build furnaces for our camps, it would have taken brave directors to say sod off - cowards, collaborators, or just business people caught up in world events.
As an engineer and the owner of a small manufacturing company, I'd like to say I'd have the courage to stand up, but I'm not sure.