Why raw strings don't compile?

Question

C++ / C#

Faced some misunderstandings when trying to write a regular expression. I write R"\(test\)" and it doesn't compile for me. Or swallows brackets. What's the problem then? I'm just escaping them for regex. This escaping is not for C++. That's why I wanted to use this very R. Or is it spelled differently here? Tell. I'm a total noob at pros. =(