Why Do Catalytic Quantities of Lewis Acid Generally Yield More Product than 1.1 Equivalent in the Intramolecular Diels-Alder Reaction with a Furan Diene? Competitive Complexation NMR Studies Provide an Answer

The effect of LiNTf2 on the propagation rate coefficient of methyl methacrylate

“…The conjugated radical is stabilised by coordination of Li + to the ester moiety, with the radical stabilisation energy (RSE) increasing relative to the corresponding uncoordinated species by between 5 to 8 kJ mol À1 , depending on the extent of cation solvation (see Table S7 in ESI †). These results suggest that saturated ester moieties are more basic than comparable a,b-unsaturated esters, which is consistent with previous experimental 35 and theoretical studies. 36 Although these results could be indicative of a modest preference for coordination to the ester group of the polymer terminus, this preference is too modest and the models considered too simplistic to allow for any conclusions regarding the position of Li + coordination.…”

“…It is well known that Lewis basicity is dependent not only on the functional identity of the coordination site but also its extended substitution. 35,36 In a bulk MMA polymerization, there are 3 functionally distinct methyl ester moieties: those of the monomer, the radical terminus and polymer side-chains. To examine if there was an underlying electronic preference for coordination to a particular ester group, binding enthalpies of various unimeric models (Fig.…”

Alkyl Aluminum Halide Promoted Intramolecular Cyclization of ω‐Allyl‐cycloalk‐2‐enones: Access to Bridged Bi‐ and Tricyclic Compounds

“…The yields dramatically decreased with R 5 or R 6 =H, which reflects the necessity of cation stabilization at the 3′ position of the allylic substituent in ketone 6 (Table 1, entry 10). Entry 11 shows that an additional ester group in substrate 6 k consumes at least one equivalent of the Lewis acid by a competitive complexation, although esters were shown to be less basic than ketones 13…”

Die Verwendung von Lewis-Säuren bei Reaktionen freier Radikale

“…Darüber hinaus bietet die gröûere Basizität ungesättigter Systeme im Vergleich zu der von gesättigten die Möglichkeit zur Katalyse. [63] Kunz et al berichteten über die Addition von Methylradikalen an chirale Oxazolidinone in Gegenwart von Me 2 AlCl. [64] Dieses wird dabei in groûem Überschuû verwendet und dient sowohl als Radikalquelle wie auch als Lewis-Säure.…”