Table 3. Lengths of Forming σ-Bonds (d, in Å) and Difference between Bond Forming Distances (Δd, in Å) at Transition States TS1xy Found for the Diels–Alder Cycloaddition of 1b,e with the 2a,b Optimized at the ωB97X-D/6-31+G** Theoretical Level in Toluene.

	dC7a-C7/dC5–C6, Δd		dC7a-C7/dC5–C6, Δd
TS1xy	endoA	exoA	endoB	exoB
1b+2a	2.00/2.91, 0.91	1.95/2.93, 0.97	2.64/1.96, 0.67	2.58/1.96, 0.62
1b+2b	2.02/2.96, 0.94	2.01/2.94, 0.92	2.77/1.97, 0.80	2.71/1.97, 0.74
1e+2a	2.02/2.83, 0.80	2.00/2.92, 0.92	2.23/2.14, 0.09	2.18/2.18, 0.00
1e+2b	2.06/2.91, 0.86	2.05/2.94, 0.88	2.60/1.96, 0.64	2.56/1.96, 0.60