Diastereo- and enantioselective aldehyde addition reactions of 2-allyl-1,3,2-dioxaborolane-4,5-dicarboxylic esters, a useful class of tartrate ester modified allylboronates

Allylation of Aldehyde and Imine Substrates with in situ Generated Allylboronates — A Simple Route to Enantioenriched Homoallyl Alcohols.

“…Conducting the allylation of 3b with isolated chiral allylboronate at room temp. (23°C/CH 2 Cl 2 ) the enantiomeric excess drops to 30 %, [9] which is in the same range as the analog reaction with in situ generated allylboronate (Entry 18) giving 45 % ee.…”

“…Roush and co-workers [4,9] have shown that allylation of 3b and 3c with (S,S)-7 (or its enantiomer) can be achieved with 71 % and 86 % ee (Scheme 3) at -78°C in toluene. An obvious drawback of the presented reactions is that they are conducted at room temp.…”

Allylation of Aldehyde and Imine Substrates with In Situ Generated Allylboronates – A Simple Route to Enatioenriched Homoallyl Alcohols

“…[9,31,32] According to this model (Scheme 10) TS structure 16a is stabilized by attractive interactions between the aldehyde carbonyl carbon (δ+) and the ester carbonyl oxygen (δ-). [31,32] On the other hand, 16b is destabilized by four-electron interactions induced by the close proximity of the lone-pair electrons in the aldehyde carbonyl and in one of the ester carbonyls of the tartrate functionality.…”

Quantum chemical study on asymmetric allylation of benzaldehyde in the presence of chiral allylboronate

“…(3) we can conclude that the main product is R-chiral alcohol for the asymmetric allylation of benzaldehyde which is in agreement with the experimental results (78 %e.e.) (Roush et al, 1985b).…”

“…And tartrate esters modified allylboronates from several laboratories have been studied thoroughly because of its simple preparation and high enantioselectivity (Haruta et al, 1982;Roush et al, 1985b;Roush et al, 1988;Roush et al, 1990a). However, the reaction mechanism has rarely been reported owing to its complexity.…”