The only time '{' needs to be escaped is when it is followed by a set of digits, followed by an optional comma and more digits, followed by a closing '}'. If you don't want that sequence of characters to be interpreted as a quantifier, all you need to do is escape the leading '{'. (This is ignoring places where {...} is part of an escaped expression like \p{Xyz} and \N{CHARACTER}.)

'{' is only a metacharacter in a very specific circumstance. You almost never need to backslash it in a regex.