for i in `echo {{a..z},{0..9}};echo {{a..z},{0..9}}{{a..z},{0..9}}`;do dict -d all -C ${i}de>/dev/null 2>&1; if [ "$?" == "0" ];then echo $i.de; fi done

or the equivalent multi-liner:

for i in `echo {{a..z},{0..9}};echo {{a..z},{0..9}}{{a..z},{0..9}}`;
  do
    dict -d all -C ${i}de >/dev/null 2>&1;
    if [ "$?" == "0" ]; then
      echo $i.de;
    fi
  done

No comment (*cough*)

(P.S. That’s for ASCII alphanumeric domains only)