Bash * directory wildcard not working in if statement using double brackets

Shell globbing patterns potentially expand to more than one pathname. For example, if /a/*/b/file.asd expands to multiple pathnames, then the test that you are performing becomes nonsensical.

Also, shell globs are not expanded inside [[ ... ]]. From the bash manual:

Word splitting and pathname expansion are not performed on the words between the [[ and ]]

If you know that you want to perform the test on a particular file, e.g. /a/x/b/file.asd, then use that pathname in the test. If you want to perform the test on all pathnames that matches that pattern, use a loop:

shopt -s nullglob dotglob for pathname in /a/*/b/file.asd; do if [[ $pathname -nt /c/d/file.asd ]]; then printf 'found new file: %s\n' "$pathname" fi done 

The nullglob and dotglob shell options are set so that the pattern is removed if it does not match anything and so that * catches any hidden directories.

Also, the test could be done with find, unless the pattern /a/*/b/file.asd expands to many thousands of pathnames:

find /a/*/b/file.asd -prune -type f -newer /c/d/file.asd 

This would expand the pattern /a/*/b/file.asd and use each of the pathnames that it expands to as a search path for find. The search paths are tested against /c/d/file.asd and the pathnames are printed if they are newer than that file. The -prune stops find from moving down into a search path, just in case any of them refers to a directory.