Table 2. Reaction Free Energies Δ_rG° and Selected Activation Free Energies Δ^‡G° (kcal mol^–1) in Water^a for the Reaction Steps Proposed in Scheme 6^b.

step	ΔrG°	Δ‡G°
thiyl radical addition	–11.5	4.9 (6.0)c
rearomatization and tautomerization	–23.2	d
H-atom abstraction	7.2

^aM06-2X/6-311++G(2d,2p), SMD//PBE0/6-31+G(d,p), PCM.

^bAll energies are referred to the reactants of the individual step.

^cIn parentheses, the value computed at the DLPNO-CCSD(T)-F12/cc-pVTZ-F12//M06-2X/6-311++G(2d,2p), SMD level.

^dUnder conditions of general base catalysis, C-5 deprotonation of IV-5 is a low barrier or a barrierless step.