Baldwin's Rules - Department of Medicinal Chemistry
Baldwin's Rules - Department of Medicinal Chemistry
Baldwin's Rules - Department of Medicinal Chemistry
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Chemical Reviews REVIEW<br />
Table 19. Activation, Reaction, and Intrinsic Energies<br />
(kcal/mol) for the Parent 5-exo- and 6-endo-dig Radical<br />
Cyclizations at the B3LYP/6-31+G(d,p) and<br />
M05-2X/6-31+G(d,p) Levels <strong>of</strong> Theory a<br />
a The M05-2X data are given in parentheses. 24 All cyclizations correspond<br />
to Motif A and the ring-closing bond is shown in red.<br />
Scheme 28. Regioselective 5-exo-dig Cyclization <strong>of</strong> Primary<br />
Carbon Radicals onto a Variety <strong>of</strong> Substituted Alkynes<br />
Scheme 29. Effect <strong>of</strong> Substitution at the Interior Propargylic<br />
Position on the Yield <strong>of</strong> 5-exo-dig Product<br />
the silyl group. Subsequent 5-exo-trig closure completed the cascade<br />
and yielded the final tricyclic product (Scheme 33). 131<br />
While polarization controls the regioselectivity <strong>of</strong> anionic cyclizations<br />
effectively (Scheme 21 and Scheme 53), Weavers et al. observed<br />
Scheme 30. Formation <strong>of</strong> Bi- and Polycyclic Products by<br />
Regioselective Radical 5-exo-dig Cyclizations and Erosion <strong>of</strong><br />
Regioselectivity Because Increased Strain in a [3.3.0] System<br />
Scheme 31. Strain-Controlled Radical 6-endo-dig Cyclizations<br />
in Cyclic trans-Fused Systems<br />
Scheme 32. Cyclizations <strong>of</strong> Conjugated 2° and 3° Carbon<br />
Radicals Corresponding to Motifs E G<br />
5-exo-dig closure for silyl, aryl alkyl substituted alkynes instead <strong>of</strong><br />
radical conjugate addition (RCA) 132 which would provide the 6-endo<br />
V dx.doi.org/10.1021/cr200164y |Chem. Rev. XXXX, XXX, 000–000
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