ChemDraw: Which naming convention (IUPAC, etc.) is used to generate names using the Structure to Name tool

Convert Structure to Name' follows IUPAC rules as closely as possible when generating chemical names. However,
while handling indicated hydrogens, it conforms to CAS nomenclature recommendations. 

For example, the carbon atom between two oxygen atoms in 1,3-dioxole can never form double bonds as its two neighbors (oxygen atoms) have no free valences. While preferred IUPAC (PIN) name for that structure is 2H-1,3-dioxole, 'Convert Structure to Name' generates the name 1,3-dioxole. The name produced by 'Convert Structure to Name' conforms to CAS nomenclature recommendations in this regard.