  Following our recent work on the benzene molecule
[\href{https://doi.org/10.1063/5.0027617}{J.~Chem.~Phys.~\textbf{153}, 176101
(2020)}], itself motivated by the blind challenge of Eriksen \textit{et al.}
[\href{https://doi.org/10.1021/acs.jpclett.0c02621}{J.~Phys.~Chem.~Lett.~\textbf{11},
8922 (2020)}] on the same system, we report accurate full configuration
interaction (FCI) frozen-core correlation energy estimates for twelve five- and
six-membered ring molecules in the standard correlation-consistent
double-$\zeta$ Dunning basis set (cc-pVDZ). Our FCI correlation energy
estimates, with estimated error smaller than 1 millihartree, are based on
energetically optimized-orbital selected configuration interaction (SCI)
calculations performed with the \textit{Configuration Interaction using a
Perturbative Selection made Iteratively} (CIPSI) algorithm. Having at our
disposal these accurate reference energies, the respective performance and
convergence properties of several popular and widely-used families of
single-reference quantum chemistry methods are investigated. In particular, we
study the convergence properties of i) the M{\o}ller-Plesset perturbation
series up to fifth-order (MP2, MP3, MP4, and MP5), ii) the iterative
approximate coupled-cluster series CC2, CC3, and CC4, and iii) the
coupled-cluster series CCSD, CCSDT, and CCSDTQ. The performance of the
ground-state gold standard CCSD(T) as well as the completely renormalized CC
model, CR-CC(2,3), are also investigated.
