You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance 2-[2-(2,5-dichlorophenyl)sulfonylethyl]-1-methyl-3,4-dihydro-1H-pyrrolo[1,2-a]pyrazine .
user
C16H18Cl2N2O2S
assistant