gem-Dialkyl effect in the intramolecular Diels-Alder reaction of 2-furfuryl methyl fumarates: the reactive rotamer effect, the enthalpic basis for acceleration, and evidence for a polar transition state

TADDOLs, Their Derivatives, and TADDOL Analogues: Versatile Chiral Auxiliaries

“…at most contributes to the stability of the propeller-like form of the TADDOLs, with two axial and two equatorial groups. Apparently the preferred arrangement is one with the heteroatoms in close proximity, hence the observed predisposition to ring formation and chelation, driven by the two geminal aryl groups (compare with the influence of geminal methyl groups on rates of ring-closure reactions, the Thorpe ± Ingold effect [103,104] ). It is thus no wonder that bicyclic TADDOL derivatives in which the heteroatoms at the diphenylmethyl groups participate in sixor seven-membered rings (overlay in the center of Figure 5) show precisely the same orientation of the aryl groups as titanium TADDOLates ( Figure 5, right), and that they conform almost exactly with the structures of the TADDOL precursors.…”

Renaissance of Organic Synthesis Using Isocyanides

“…The presence of bulky substituent(s) at the ¢-position of enones should facilitate the intramolecular cyclization step by the ThorpeIngold effect, 14 which was indeed observed experimentally. The viability of this mechanism was supported in a computational study by Xie.…”

Platinum(II) Complexes with the Diethyl Aminomethylphosphonate Ligand (amp): Characterization, Properties, and Unusual Solution Behavior

“…[17] This effect is similar to that first described by Thorpe and Ingold in relation to the cyclization of organic moieties [18a-18c] and discussed in greater detail in later work. [19] An additional factor that could favor chelation of smp is the cis-labilizing effect of the coordinated sulfoxide group, [20a-20d] which could favor the release of a cis-chlorido ligand in the adduct with monocoordinated smp. Once the chelate ring has been formed, the sulfur-bound oxygen points outward from the chelate ring and does not labilize the cis-coordinated phosphonic group.…”