Rings having (formally) the maximum number of noncumulative double bonds, e.g. benzene, indene, indole, 4
H-1,3-dioxine. Also called mancunide-ring systems.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1348 (https://doi.org/10.1351/pac199567081307)