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. Author manuscript; available in PMC: 2010 Feb 11.
Published in final edited form as: J Am Chem Soc. 2009 Feb 11;131(5):1947–1957. doi: 10.1021/ja8079548

Table 5.

Endo (n) and Exo (x) TS Geometries and Energetics for a Range of Substituted Silylated Dienes with Dienophile Complex A2, with an Emphasis on Twist-Mode Asynchronicity.

Entry Diene TS geometry ΔG‡298a ΔE0‡b θc Me(H)–Me dihedral angle
endo exo
1 graphic file with name nihms-89481-t0042.jpg graphic file with name nihms-89481-t0043.jpg graphic file with name nihms-89481-t0044.jpg 30.3(n) 27.4(x) 2.0 (−14.8) (n) −0.1 (−14.1) (x) −6°(n) +15°(x) 47°(n) 69°(x)
2 graphic file with name nihms-89481-t0045.jpg graphic file with name nihms-89481-t0046.jpg graphic file with name nihms-89481-t0047.jpg 23.8(n) 23.0(x) −1.4 (−12.9) (n) −1.3 (−11.2) (x) −6°(n) +8°(x) 52°(n) 57°(x)
3 graphic file with name nihms-89481-t0048.jpg graphic file with name nihms-89481-t0049.jpg graphic file with name nihms-89481-t0050.jpg 31.3(n) 29.9(x) 6.8 (−9.8) (n) 5.5 (−9.4) (x) −4°(n) +13°(x) 51°(n) 66°(x)
a

Gas phase Gibbs energies at B3LYP/6−31G(d) level, corrected for solvent effects by PCM single-points at HF/6−31+G(d,p) on B3LYP/6−31G(d) vacuum optimized geometries.

b

Gas phase uncorrected electronic energy at B3LYP/6−31G(d)//B3LYP/6−31G(d) level. The corresponding MP2/6−31+G(d)//B3LYP/6−31G(d) level in parentheses.

c

Twist-asynchronicity parameter. See Figure 6b for definition.