You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Name the molecular formula for the molecule established as 1-[3-chloro-4-(3-oxopiperazin-1-yl)phenyl]-3-[(2S)-2-(diethylamino)-2-thiophen-3-ylethyl]urea using the IUPAC nomenclature.
user
C21H28ClN5O2S
assistant