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 N-[(3aR,6aS)-3-(5-chloro-2,4-dimethoxyphenyl)-5,5-dioxo-3a,4,6,6a-tetrahydrothieno[3,4-d][1,3]thiazol-2-ylidene]-2-(2-chlorophenyl)acetamide .
user
C21H20Cl2N2O5S2
assistant