import re


def is_valid_doi(doi: str) -> bool:
    """Validate a DOI via regular expressions.

    Parameters
    ----------
    doi : string
        A single DOI to be validated.

    Returns
    -------
    bool
        True, if DOI is valid, False if not.

    """
    patterns = [
        r"^10.\d{4,9}/[-._;()/:A-Z0-9]+$",
        r"^10.1002/[^\s]+$",
        r"^10.\d{4}/\d+-\d+X?(\d+)\d+<[\d\w]+:[\d\w]*>\d+.\d+.\w+;\d$",
        r"^10.1021/\w\w\d+$",
        r"^10.1207\/[\w\d]+\&\d+_\d+$",
    ]
    for pat in patterns:
        if re.match(pat, doi, re.IGNORECASE):
            return True
    return False