You need to double the backslashes used to escape the regular expression special characters. However, as @Bohemian points out, most of those backslashes aren’t needed. Unfortunately, his answer suffers from the same problem as yours. What you actually want is:
The backslash is being interpreted by the code that reads the string, rather than passed to the regular expression parser. You want:
Note the quadrupled backslash. That is definitely needed. The string passed to the regular expression compiler is then identical to @Bohemian’s string, and works correctly.