import re
s="""some text before Expedien: 1-21-212-16-26 some random text
Reference RE9833 of all sentences.
abc
123
456
something blah blah Ref.: 
tramite  1234567
Ref.:
some junk Expedien N° 18-00777 # some new content
some text Expedien N°18-0022995 # some garbled content"""
my_list = ['Ref.:', 'Reference', 'tramite', 'Expediente', 'Expediente No', 'Expedien N°', 'Exp.No', 'Expedien']
rx = r'(?<!\w)({})\W*([A-Z]*\d+(?:-+[A-Z]*\d+)*)'.format('|'.join(map(re.escape,my_list)))
print(re.findall(rx, s))